EFFECT OF PROCESS PARAMETERS ON METHANOL TO OLEFINS 
 
 REACTIONS OVER SAPO CATALYSTS 
 
 
Except where reference is made to the work of others, the work described in this thesis is 
my own or was done in collaboration with my advisory committee.  This thesis does not 
include proprietary or classified information. 
 
 
____________________________ 
Luckner Jean 
 
 
 
Certificate of Approval: 
 
          
Christopher B. Roberts     James A. Guin, Chair 
Uthlaut Professor      Professor 
Chemical Engineering      Chemical Engineering 
 
 
 
          
Steve R. Duke                                 Stephen L. McFarland 
Associate Professor      Dean 
Chemical Engineering      Graduate School 
 
 
 
EFFECT OF PROCESS PARAMETERS ON METHANOL TO OLEFINS 
 
 REACTIONS OVER SAPO CATALYSTS 
 
 
Luckner Jean 
 
 
A Thesis 
Submitted to 
the Graduate Faculty of 
Auburn University 
In Partial Fulfillment of the 
Requirement for the 
Degree of 
Master of Science 
 
 
Auburn, Alabama 
August 8, 2005 
 
 
 iii
EFFECT OF PROCESS PARAMETERS ON METHANOL TO OLEFINS  
 
REACTIONS OVER SAPO CATALYSTS 
 
 
Luckner Jean 
 
 
Permission is granted to Auburn University to make copies of this thesis at its discretion, 
upon the request of individuals or institutions and at their expense.  The author reserves 
all publication rights. 
 
 
 
     
Signature of Author 
 
 
     
Date 
 
 
Copy sent to: 
 Name        Date 
 
 
 
 
 iv
VITA 
Luckner Jean, son of Saurel Jean and Anicia Guillaume, was born on May 05, 
1970 in Port-au-Prince, Haiti.  He left Haiti in 1985 and emigrated to the United States 
where he is still living ever since.   In 1999 he was awarded a degree in Chemical 
Engineering from the Illinois Institute of Technology (IIT) in Illinois.  Upon graduation 
he continued doing research activities in the Chemistry Department at Chicago State 
University.  In August 2003, he started graduate studies in Chemical Engineering at 
Auburn University in Alabama. 
 
 
 
 
 
 
 
 
 
 
 
 
 v
THESIS ABSTRACT 
EFFECT OF PROCESS PARAMETERS ON METHANOL TO OLEFINS 
 
 REACTIONS OVER SAPO CATALYSTS 
 
 
Luckner Jean 
 
Master of Science, August 8, 2005 
(B.S. Chemical Engineering, Illinois Institute of Technology, 1999) 
 
116 Typed Pages 
Directed by Dr. James A. Guin 
 
Acidic catalysts such as silicoaluminophosphate oxides (SAPO) have been known 
to play an essential role in olefins synthesis reactions.  Because of their unique selectivity  
towards light olefins, these SAPO catalysts offer a promising alternative as reaction 
media in catalytic reactions based on the abundant supply of natural gas.  In this thesis 
several studies were undertaken in order to examine the effects of process parameters on 
the methanol to olefins reactions (MTO) with particular emphasis on catalytic activity, 
lifetime, and product selectivity.  All of the MTO reactions were performed under 
atmospheric pressure with catalyst bed temperature maintained at 400 
o
C in a continuous 
 vi
fixed bed reactor by employing small pore SAPO catalysts:  SAPO-34, SAPO-44, SAPO-
47, and SAPO-56 (0.3 ~0.9 Si).         
            In order to judiciously make good use of the limited catalyst stocks, a scale-down 
analysis was performed by reducing all reaction parameters by 40%, i.e. catalyst load, 
methanol feed, and nitrogen flow.  Product distribution profiles between before and after 
parameter reductions indicated almost identical catalytic activities with minor variations.  
A significant portion of this thesis was devoted to the particle size effects on the reaction 
behavior.  The results from the ground particles demonstrated all catalysts maintained 
their stability.  With the exception of SAPO-56 which showed no apparent activity 
difference for reduced particles, all SAPO?s tested showed enhanced catalytic activity 
and lifetime. Improvements in C
2
 to C
4
 olefins selectivity and methanol conversion were 
observed as well. These same effects were also apparent upon temperature variation (300 
o
C to 500 
o
C).  Effect of silicon content over SAPO-56 prepared with three different 
silicon amounts (0.3, 0.6, and 0.9 Si) indicated optimum olefins selectivity at 0.6 Si.  
Also, a spent catalyst was ground and tested for activity.  From that reaction, only 
dimethyl ether (DME) and methanol (MeOH) were present in the product stream, 
indicating that all of the particle active sites have been covered with coke deposits.  A 
thorough examination of all reactions over ground particles pointed to increased DME 
yields after catalyst deactivation began, as compared to before grinding.  Reactions over 
catalysts modified with Ru only showed slight improvements when compared with the 
unmodified catalysts.  Modification with metals such as palladium (Pd) and platinum (Pt) 
would be interesting. 
 vii
ACKNOWLEDGEMENTS 
 
 The author would like to express his sincere appreciation and gratitude to various 
people.  Mr. Joe Aderholdt for helping repair equipment malfunction and breakdown; Dr. 
Prakash M. Adekkanattu for preparing all the original SAPO samples and Dr. Richard 
Ernst group at the University of Utah for the SAPO modification; Dr. Xiwen Huang for 
assisting him in the lab in various capacities; Dr. Dave Kanis for all his encouragements; 
and Dr. Nimir Elbashir for providing him with valuable advice.  Also, the author would 
like to extend a warm thanks to the Chemical Engineering Department staff for their 
assistance:  Mses. Sue Abner, Nancy Borland, Jennifer Harris, and Kellie Wilson. 
 In addition the author is very grateful both to Dr. Steve Duke and Dr. Christopher 
Roberts for serving in his oral committee and for offering him valuable advice in the 
toughest of times.  Most of all, he owes much of the success of this study to his advisor 
Dr. James Guin for guiding him throughout the course of the project.   
The author is very thankful to his friends back in Chicago for their continued 
friendly advice and moral support in the challenging days: Marie, Yvrose, Dieudonne, 
Enold, Sandra, and Franklin just to name a few.  Also, he would like to acknowledge 
those friends he had come to know since being here in Alabama.  To his family, he would 
like to thank his brothers and sisters for always being there in believing in him.  To his 
mom and dad, he can?t thank them enough for the wisdom and humility they instilled in 
him which guided him to this point, he loves them very much. 
 viii
Style manual or journal used Guide to Preparation and Submission of Theses and 
Dissertations, Applied Catalysis A: General 
 
Computer software used Microsoft Word, Microsoft Excel, Microsoft Paint, Microsoft 
Photo Editor, EndNote for Students 
 ix
TABLE OF CONTENTS 
 
LIST OF TABLES                           xii 
 
LIST OF FIGURES                         xiii  
 
I.        INTRODUCTION                  1 
 
II.       LITERATURE REVIEW                3 
    
        Background                  3 
        Methanol to Olefins (MTO)                8 
        Methanol to hydrocarbons Mechanism                        9 
           SAPO Impregnation                          12 
        Effect of Acid                            13 
        Template (Structure Directing Agent)                                   14 
        Coke Formation (Catalyst Deactivation)                       16 
        Role of water                            18 
        Catalyst Regeneration                          19 
        SilicoAluminoPhosphate (SAPO)                        20 
        Particle Size and Shape                         21 
 
III.      EXPERIMENTAL                          24 
   
        Sample Preparation                          24    
           Modified Catalysts                           24 
           Particle Characterization                         25         
           SAPO-47 Fractionation                          25 
          Grinding of Particles                          26 
           Standard Analysis  (Olefins, Paraffins, DME and MeOH)                     27     
           Product Analysis (Actual Runs)                          29 
           Reaction Procedures                          31 
           Temperature Method                          34 
 
IV.      RESULTS AND DISCUSSIONS                        35 
 
           SEM Analysis                           35 
        Scale-Down Analysis                          36 
           Temperature Studies                          38 
        Temperature Study (SAPO-34), (P-5)                        39                
 x
        Temperature Study (SAPO-44), (P-6)                                              41 
           Temperature Study (SAPO-56), (P-18), (0.6 Si)                      43 
           Catalytic Reaction Study                         45 
           SAPO-44, (P-6)                          46 
           SAPO-34, (P-5)                                                                           53              
           SAPO-47, (P-31)                              57 
           SAPO-56                           61 
           SAPO-56 (P-18), (0.6 Si)                         61 
           SAPO-56 (P-28), (0.3 Si)                         65 
           SAPO-56 (P-29), (0.9 Si)                         68 
           Effect of Silicon Content              71 
           SAPO-56 (P-18), (0.6 Si) Spent Catalyst                       72 
           SAPO Incorporated with Ruthenium                        73 
           Ru-SAPO-34 (Ru-P-5)                          73 
           Ru-SAPO-44 (Ru-P-6)                          74 
           Ru-SAPO-56 (Ru-P18)                         75 
   
V.       CONCLUSION                          78 
 
VI.      REFERENCES                          80 
                
VII.     APPENDICES                           84 
 
           Appendix A                            85 
                    
                  A-1.  Table of Zeolite structures.                        86 
                  A-2.  Wig-L-Bug.                          87 
                 
           Appendix B (SEM Micrographs)                                              88 
                   
                  B-1.   SAPO-34                          89 
                  B-2.   SAPO-44                          89 
                  B-3.   SAPO-44 (After 5 min Grinding)                       90 
                  B-4.   SAPO-44 (After 10 min Grinding)                       90 
                  B-5.   SAPO-44 (After 15 min Grinding)                       91 
                  B-6.   SAPO-47                           91 
                  B-7.   SAPO-47                          92 
                  B-8.   SAPO-47 (Sonicated in Acetone)                       92  
                  B-9.   SAPO-47 (Sonicated in Acetone)                       93 
                  B-10. SAPO-56 (0.3 Si)                          93 
                  B-11. SAPO-56 (0.6 Si)                         94 
                  B-12. SAPO-56 (0.9 Si)                         94 
                  B-13. RuSAPO-56                         95 
                  B-14. RuSAPO-44                          95 
                  B-15. RuSAPO-44                         96 
                  
 xi
      B-16. RuSAPO-56                         96 
                  B-17. RuSAPO-56                         97 
 
                  
           Appendix C  (Calculation Procedure)                        98 
 
                  C.1 ? C.12 (List of Equation)                        99 
 
 xii
LIST OF TABLES 
 
Table  2.1.  Acronyms for Framework Composition                                          5 
 
Table  2.2.  Typical SAPO and MeAPO Framework Composition                              5 
 
Table  2.3.  Typical Structures in AlPO4-based Molecular Sieves                               7 
 
Table  3.1.  Retention Time for Olefins Standard Components                           28  
 
Table  3.2.  Retention Time for Paraffins Standard Components                          28 
 
Table  3.3.  Retention Time for Methanol Standard.                                       29 
 
Table  3.4.  Retention Time for Dimethyl Ether Standard.                         29 
 
Table  3.5.  MTO Product Distribution over SAPO-47(Finer Particles)                      34 
 
Table  4.1.  Product Distribution over SAPO-44 (P-6), After 10 min. Grinding.        49  
 
Table  4.2.  Product Distribution over SAPO-44 (P-6), After 15 min. Grinding.        51 
 
Table  4.3.  Product Distribution over SAPO-56 (P-28), No Grinding.         65 
 
Table  4.4.  Product Distribution over SAPO-56 (P-28), After 15 min. Grinding.        67 
 
Table  4.5.  Product Distribution over SAPO-56 (P-29), No Grinding.         68 
 
Table  4.6.  Product Distribution over SAPO-56 (P-29), After 15 min. Grinding.        70 
 
Table  4.7.  Product Distribution over Ru-SAPO-56 (Ru-P-18).          76 
 
 
 
 
 
 
 
 
 
 
 xiii
LIST OF FIGURES 
 
Figure  2.1.  Illustration of the molecular sieve effect.                         4 
 
Figure  2.2.  Shape Selectivity                            8 
a) Reactant                  8 
b) Product                  8 
c) Transition-state                 8 
 
Figure  2.3.  View of two adjoining cages formed at channel intersections in the 
                    all-silica zeolite SSZ-23 (STT) showing the position of the structure 
                    directing agent TMAda+  around which the frameworks forms.                  15 
 
Figure  3.1.  Illustration for packed bed reactor.                        27 
 
Figure  3.2.  GC Profile of Olefins Standard.                                    27 
 
Figure  3.3.  GC Profile of Paraffins Standard.                        28 
 
Figure  3.4.  GC Profile of Methanol Standard MeOH.                       29 
 
Figure  3.5.  GC Profile of Dimethyl Ether (DME).                        29 
 
Figure  3.6.  Spreadsheet for MTO Analysis.                                    31 
 
Figure  3.7.  Close-Up View of the Quartz Tube Reactor.                       32 
 
Figure  3.8.  MTO Reactor Diagram.                                     33 
 
Figure  3.9.  GC Product Distribution Profile over SAPO-47 (P-31)            
                    (Finer Particles), Temp= 400
o
C.                             34 
 
Figure  4.1.  Distribution of C
2
 ? C
4
 Olefins, DME, and MeOH over           
SAPO-56 (P-18), (0.6 Si), (Load = 0.504 g,  
MeOH flow = 0.005 ml/min, WHSV = 0.5 hr
-1
).                      37 
 
Figure  4.2.  Distribution of C
2
 ? C
4
 Olefins, DME, and MeOH, SAPO-56        
(P-18), (0.6 Si), (Load = 0.307 g,  
MeOH flow = 0.003 ml/min, WHSV = 0.5 hr
-1
).                      38 
 
 xiv
Figure  4.3.  Temperature Effect on Product Distribution over SAPO-34 (P-5),    
                    (No Grinding).                           40 
 
Figure  4.4.  Temperature Effect on Product Distribution over SAPO-34 (P-5),            
                    (After 15 min. Grinding).                         40 
 
Figure  4.5.  Temperature Effect on Product Distribution over SAPO-44 (P-6),            
                    (No Grinding).                           42 
 
Figure  4.6.  Temperature Effect on Product Distribution over SAPO-44 (P-6),            
                    (After 15 min. Grinding).                         42 
 
Figure  4.7.  Temperature Effect on Product Distribution over            
                    SAPO-56 (P18), (0.6 Si), (No Grinding).                       43 
 
Figure  4.8.  Temperature Effect on Product Distribution over                       44 
                    SAPO-56 (P-18), (0.6 Si), (After 15 min. Grinding). 
 
Figure  4.9.  Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and  
                    DME over SAPO-44 (P-6), 400
o
C, (No Grinding).                                 47                     
 
Figure 4.10. Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and  
                    DME over SAPO-44 (P-6), 400
o
C, (After 5 min. Grinding).                     47                     
 
Figure 4.11. Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and  
                    DME over SAPO-44 (P-6), 400
o
C, (After 10 min. Grinding).                     49                     
 
Figure 4.12. Distribution of Ethylene, Propylene, C
2 
? C
4
 Olefins, MeOH, and  
                    DME over SAPO-44 (P-6), 400
o
C, (After 15 min. Grinding).                      51 
 
Figure 4.13. Effect of Grinding Time over SAPO-44 (P-6).                                      52 
                        
Figure 4.14. Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and  
                    DME over SAPO-34 (P-5), 400
o
C, (No Grinding).                       53                       
 
Figure 4.15. Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and  
                    DME over SAPO-34 (P-5), 400
o
C, (After 5 min. Grinding).                     54                     
  
Figure 4.16. Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and  
                    DME over SAPO-34 (P-5), 400
o
C, (After 10 min. Grinding).                     55                       
 
Figure 4.17. Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and  
                    DME over SAPO-34 (P-5), 400
o
C, (After 15 min. Grinding).                     56 
                       
 xv
Figure 4.18. Effect of Grinding Time On Product Distribution.  
                    (GT = Grinding Time)                                          57 
 
Figure 4.19. Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and  
                    DME over SAPO-47 (P-31), 400
o
C, Coarse Particles.                               58 
 
Figure 4.20. Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and  
                    DME over SAPO-47 (P-31), 400
o
C, Coarse Particles.            
                    (No Grinding).                           58 
  
Figure 4.21. Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and  
                    DME over SAPO-47 (P-31), 400 
o
C,  Finer Portions.            
                    (No Grinding).                           59 
  
Figure 4.22. Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and  
                    DME over SAPO-47 (P-31), 400 
o
C, (Finer Particles)                      60 
         (After 15 min Grinding) 
 
Figure 4.23. Methanol Conversion Profile over SAPO-47 (P-31), 400 
o
C, 
                    (Finer Particles).                                  61 
 
Figure 4.24. Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and  
                    DME over SAPO-56 (P-18), 400 
o
C, (0.6 Si), (No Grinding).                     62                        
 
Figure 4.25. Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and  
                    DME over SAPO-56 (P-18), 400 
o
C, (0.6 Si), (No Grinding).                       63                       
  
Figure 4.26. Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and  
                    DME over SAPO-56 (P-18), (0.6 Si), 400 
o
C, 
         (After 15 min. Grinding).                         64 
 
Figure 4.27. Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and  
                    DME over SAPO-56 (P-18), (0.6 Si), 400 
o
C.                        
                    (After 15 min. Grinding)               64 
 
Figure 4.28. Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and  
                    DME over SAPO-56 (P-18), (0.3 Si), 400 
o
C, (No Grinding).                     66                       
 
Figure 4.29. Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and  
                    DME over SAPO-56 (P-18), (0.3 Si), 400 
o
C,  
         (After 15 min. Grinding).                         67 
                       
Figure 4.30. Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and  
                    DME over SAPO-56 (P-29), (0.9 Si), 400
o
C, (No Grinding).                       69                       
 xvi
Figure 4.31. Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and  
                    DME over SAPO-56 (P-29), (0.9 Si), 400
o
C .             
                    (After 15 min. Grinding).                        70  
 
Figure 4.32. Effect of Silicon Content on Olefins Selectivity over SAPO-56, 
                    (No Grinding).                          71 
 
Figure 4.33. Effect of Silicon Content on Olefins Selectivity over SAPO-56, 
                    (No Grinding).                          72 
 
Figure 4.34. Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and  
                    DME over Spent SAPO-56 (P-18), (0.6 Si) catalyst.                          73 
                    (After 15 min. Grinding) 
 
Figure 4.35. Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and  
                    DME over Ru impregnated SAPO-34 (Ru-P-5), 400
o
C.                              74 
                        
Figure 4.36. Distribution of Ethylene, Propylene, C
2
 ? C
4 
Olefins, MeOH, and  
                    DME over Ru impregnated SAPO-44 (Ru-P-6), 400
o
C.                              75 
                      
Figure 4.37. Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and  
                    DME over Ru impregnated SAPO-56 (Ru-P-18), 400
o
C.                       77  
                       
 
 
 
 
 
 
 1
I. INTRODUCTION 
 
 
 
With the world economy becoming more interconnected and dependent, finding 
new sources of energy and industrial valuable products has become very critical to 
remain competitive in meeting market demand.   With energy demand far outstriping 
energy supply this focus seems more relevant than ever.  In recent years the methanol to 
olefins (MTO) process has received wide attention as it provides an indirect route in 
reaching that goal.  Since their discovery at Union Carbide laboratory small pore 
molecular sieves have been in the center of the MTO phenomenon.  In catalytic reactions 
these microporous materials particularly silicoaluminophosphate oxides (SAPO) give a 
narrow range of product distribution with a high selectivity towards C
2
-C
4
 olefins, 
however, diffusion of larger molecules through their narrow pores is very restricted.  
Their unique selectivity ability has spurred considerable interest in the research 
community in finding better ways to making them more efficient in performance and 
overcoming rapid coke formation brought about by larger molecules formed inside the 
pores.  Variations in parameters such as silicon content, acid site density, acid strength, 
crystallite size, nature of template, silicon and aluminum source and hydrothermal 
conditions have been known to influence catalytic activity and selectivity towards light 
olefins.   
In the present work, testing of various microporous SAPO catalysts has been 
undertaken with particular emphasis on several process parameters such as: particle 
 2
size, temperature, silicon content and metal incorporation. How these parameters are 
varied would indicate the extent of their influence towards light olefins selectivity, 
catalyst activity, and methanol conversion.  To complement the SAPO testing analyses, a 
few other studies were pursued as well.  With the available catalyst stock running low, a 
scale-down study was undertaken to assess the impact of process variables reduction on 
reaction behavior.  Methanol feed, nitrogen flow and catalyst load were all reduced by a 
40% margin.  A study on a spent catalyst was performed in order to see if some of the 
catalyst activities could be regenerated in which the catalyst was ground for 15 minutes 
and tested for activity.  
 
   
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 3
II. LITERATURE REVIEW 
 
 
 
  Background 
 
 The history of zeolites didn?t begin until 1756 when a Swedish mineralogist by 
the name of Cronstedt first discovered the mineral zeolite: stilbite.  This mineral which 
appeared like crystals would swell or enlarge when heated in a blow tube flame.  And 
from that point on Cronstedt would characterize the mineral a ?zeolite?, the combination 
of two Greek words: zeo and litho meaning to boil and a stone, respectively.  In 1840, 
Damour observed that crystals of zeolites could be reversibly dehydrated with no 
observable change in their transparency or morphology.  Way and Thompson, who in 
1850 studied the nature of ion exchange in soil, had their work expanded upon by 
Eichhon who showed in 1858 the reversibility of ion-exchange on zeolite minerals. 
Friedel, who noticed that various liquids such as alcohol, benzene, and chloroform, were 
occluded by dehydrated zeolites, developed the porous nature of zeolites in 1896.   The 
behavior of zeolites as molecular sieves, a term developed by McBain 1932 was reported 
in 1925 by Weigel and Steinhoff.  This feature which is unique to zeolites structures 
selectively allows passage of certain molecules within their pores while limit passage of 
other molecules due to their sizes and shapes (Figure 2.1). 
 
   
 4
     
Figure.  2.1.  Illustration of the molecular sieve effect.   
                      The straight chain molecular normal octane (left) passes through the eight-ring aperture 5A   
        zeolite.  The branched molecule iso-octane (right) cannot. (Flanigen et al., 2001) 
 
Many zeolites occur naturally as minerals, they are mined extensively in many 
parts of the world.  Others, however, are synthetic ? they are made for commercial uses ? 
or produced by research scientists trying to understand more about their chemistry (See 
Figure A-1, in Appendix A).  Early discovery of some twenty synthetic aluminosilicate 
zeolites in the late 1940?s and early 1950?s by researchers at the Union Carbide 
Laboratories and the potential applications for many of these materials formed the basis 
for the molecular sieve industry.  To date there are more than 40 known natural zeolites 
and almost 200 synthetic ones, and new ones are being discovered continuously.  Zeolites 
are microporous crystalline solids with well-defined structures.   They generally contain 
silicon, aluminum and oxygen in their framework, with a normalized formula, TO
2
, 
representing the concentration of elements in the composition (Tables 2.1 and 2.2).  
Because of their unique porous properties, they are used in a variety of 
applications.  In the western world, they are used in petrochemical cracking, ion-
exchange (water softening and purification), and in the separation and removal of gases 
and solvents.  Properties such as ion-exchange, sorption capacity, shape selectivity, 
catalytic activity among others are characteristics of zeolites determined essentially by 
their structures.   
 5
 Table  2.1.  Acronyms for Framework Compositions (Flanigen et al., 1986) 
 
       TO
2
, T=                   Acronym                             TO
2
, T=                     Acronym 
 
       Si, Al, P                   SAPO                                  Me, AL, P, Si            MeAPSO 
       Me, AL, P                MeAPO                               Fe, Al, P, Si              FAFSO 
       Fe, Al, P                   FAPO                                 Mg, Al, P, Si             MAPSO 
       Mg, Al, P                 MAPO                                Mn, Al, P, Si             MnAPSO 
       Mn, Al, P                 MnAPO                              Co, Al, P, Si              CoAPSO 
       Co, Al, P                  CoAPO                               Zn, Al, P, Si              ZAPSO 
       Zn, Al, P                  ZAPO                                   
 
Other Elements: 
 
       El, Al, P                   ElAPO                                El, Al, P, Si               ElAPSO 
 
 
 
Table  2.2. Typical SAPO and MeAPO Framework Composition. (Flanigen et al., 1986)  
                    x, y, z:  mole fractions of the respective elements. 
 
SAPO Species                  (Si
x
         AL
y
         P
z
)O
2
                Net Framework Charge/TO
2
 
                                            x            y             z 
 
       5               0.14       0.45        0.41                                   -0.04 
      11                                0.14       0.44        0.42                                   -0.02 
      34                                0.13       0.50        0.37                                   -0.13 
      37                                0.16       0.50        0.34                                   -0.16 
 
 
MAPO Species                  (Me
x
         AL
y
        P
z
)O
2
               Net Framework Charge/TO
2
 
                                            x              y           z 
 
       5                                 0.08       0.42        0.50                                  -0.08 
      36                                0.09       0.42        0.49                                  -0.11 
      11                                0.08       0.42        0.50                                  -0.08 
      44                                0.14       0.36        0.50                                  -0.14 
      20                                0.16       0.33        0.51                                  -0.14 
 
 
 
These zeolite frameworks are made up of 4-connected networks of atoms.  These 
networks of atoms form tetrahedrals with a silicon atom in the middle and oxygen atoms 
at the corners.  These tetrahedrals link together by their corners to form a variety of 
beautiful structures.  The framework structure may contain linked cages, cavities, or 
channels, which are of the right size to allow small molecules to enter.  The limiting pore 
sizes are roughly between 3 and 10 ? in diameter depending on the number of rings 
(McCusker and Baerlocher, 2001). 
 6
 There are about 130 different framework structures that are now known. Aside 
from having a silicon or aluminum as the tetrahedral atom, other compositions have also 
been synthesized, with the growing category of microporous aluminophosphates, known 
as ALPOs (Table 2.3). 
Zeolites have the ability to act as catalysts for chemical reactions which take place 
within the internal cavities.  Many organic reactions including crude oil cracking, 
isomerization and fuel synthesis involve the catalyzed reaction by hydrogen-exchange 
zeolites whose framework bound protons give rise to very high acidity.  Also, zeolites 
can serve as oxidation or reduction catalysts, especially after metals have been introduced 
into the framework.  Examples include titanium ZSM-5 in the production of caprolactam 
and copper zeolites in NO
x
 decomposition. 
A key feature in the nature of microporous zeolites is their shape-selective 
attribute.  Three types of shape selectivity have been identified (Weisz, 1980): a) reactant 
shape selectivity; b) product shape selectivity; and c) transition-state shape selectivity 
(Figure 2.2).  Different types of molecules enter the zeolite, but some diffuse through the 
channels more quickly, leaving others stuck behind, as in the purification of paraxylene 
by silicalite (Attfield, 2002).  This feature has been given enormous attention in order to 
synthesize high-value chemicals for the pharmaceuticals and cosmetics industries.  
 
 
 
 
 
 
 7
Table  2.3:  Typical Structures in AlPO
4
-based Molecular Sieves (Flanigen et al., 1986) 
     Species          Structural Type                    Pore Size(nm) 
 
Very Large Pore 
       VPI-5      Novel     1.25 
 8     Novel     0.9 
 
     Large Pore 
            5     Novel     0.8 
           36      Novel      0.8 
           37       FAU      0.8 
           40      Novel      0.7 
           46      Novel      0.7 
 
   Intermediate 
           11      Novel      0.6 
           31      Novel     0.65 
           41       Novel      0.6 
 
     Small Pore 
           14      Novel      0.4 
           17       ERI     0.43 
           18      Novel     0.43 
           26      Novel     0.43 
           33      Novel      0.4 
      34,44,47       CHA     0.43 
           35       LEV     0.43 
           39      Novel      0.4 
           42       LTA     0.43 
           43       GIS     0.43 
           52      Novel     0.43 
           56      Novel     0.43 
 
Very Small Pore 
           16      Novel      0.3 
           20      SOD      0.3 
           25      Novel      0.3 
           28      Novel      0.3 
 
 
 
 
 
 8
  
                        
Figure  2.2.  (a) Reactant Selectivity; (b) Product Selectivity; (c) Transition-state Selectivity.    
                     (Attfield, 2002) 
 
 
 
Methanol To Olefins (MTO) 
 
 New zeolite derived catalysts began to appear on the scene in the early 80?s with 
the discovery of crystalline microporous aluminophosphates (AlPO
4
).  Further 
improvement of these structures eventually led to the discovery SAPO-n framework 
where n denotes structure type.  Since then these SAPO structures have received 
considerable attention due to their role in the methanol to olefins process (MTO).  This 
process provides an indirect way of converting fossil resources to industrially valuable 
olefins and other value-added products.   
 Because of their narrow pore openings (~ 0.43 nm) microporous SAPO catalysts 
like SAPO-17, SAPO-18, SAPO-35 and SAPO-44 are good candidates for the MTO 
process as their small pore openings can only sorb straight chain molecules such as 
primary alcohols, linear paraffins, and olefins, but not branched isomers and aromatics.  
 9
These small pore molecular sieves have been reported to be very selective towards 
ethylene and propylene (Wilson and Barger, 1999; Chen et al., 1994; Djieugoue et al, 
1994).  
Of all SAPO catalysts known to date SAPO-34 is by far the most widely studied 
and desirable catalyst for the MTO process.  Other catalysts such as SAPO-44, SAPO-47 
and SAPO-56 have received much less attention.  The technology for methanol 
production from natural gas is widely used and well-established, however, the 
mechanism for converting the methanol to hydrocarbons is still not understood.  The 
effects of adsorption, diffusion, secondary reactions including coke formation are aspects 
of the MTO reaction that are still not resolved. 
 
 
Methanol to Hydrocarbons Mechanism  
 
 The selective dehydration of methanol to olefins is a potential route for the 
production of C
2
 -- C
4
 lower olefins.  Understanding the reaction mechanism is important 
for the development of a high efficiency catalyst.  The mechanism involves C-C bond 
formation from C
1
 fragments generated in the presence of certain acidic catalysts.  The 
mechanism, though not well understood, is believed to go through a dimethyl ether 
(DME) intermediate:   
          
  
The main reaction steps of methanol conversion to hydrocarbons can be 
summarized as follows: Methanol is first dehydrated to dimethyl ether.  The equilibrium 
 10
mixture formed, consisting of methanol, dimethyl ether and water, is then converted to 
light olefins.  In the last step of this scheme, the light olefins react to form paraffins, 
aromatics, naphthenes, and higher olefins by hydrogen transfer, alkylation and 
polycondensation (Stocker, 1999).  
There has been a general consensus that the intermediate in the dehydration of 
methanol to dimethyl ether over solid acid catalysts is a protonated surface methoxyl, 
which is subject to a nucleophilic attack by methanol (Chang et al., 1988).  The 
subsequent conversion of light olefins to paraffins, aromatics, naphthenes and higher 
olefins, which proceeds via classical carbenium ion mechanisms with concurrent 
hydrogen transfer, is well known from hydrocarbon chemistry in acid media (Froment et 
al., 1992).  However, the second step which represents the initial C?C bond formation 
from the C
1
 reactants, has been the topic of extensive discussion throughout the years.  
For the last 25 years over 20 possible mechanistic proposals for the formation of C -- C 
bond have been offered and the most discussed and relevant of these mechanisms can be 
classified as follows: 
a) The oxonium ylide mechanism 
b) The carbine mechanism 
c) The carbocationic mechanism 
d) The free radical mechanim 
 
However, those proposed mechanisms may be broadly classified and lumped into  
 
two groups: 
 
1) The consecutive type mechanism: 
 
                   
 
 11
2) The parallel type mechanism:  
    
                         
 
Dahl and Kolboe (1993, 1994) showed the consecutive mechanism was not 
appropriate, and therefore proposed what they called a ?carbon pool mechanism? which 
is a kind of modified parallel mechanism: 
                              
 
This model (Hydrocarbon Pool Mechanism) implies a dynamic situation in 
which large carbonaceous species build up inside the cages of the structure.  These 
carbonaceous compounds are continuously adding reactants and splitting off products 
(Dahl et al., 1999). 
 
 
SAPO Impregnation 
 
Because of the rapid deactivation that often occurs in methanol to olefin 
conversion reaction, researchers continuously look for ways to improve catalyst 
performance and simultaneously minimize or control the rate of coke formation.  Some of 
the commonly used methods in modifying the SAPO framework include: impregnation, 
ion-exchange, and isomorphous substitution.  SAPOs incorporated with transitional metal 
ions have been shown to have much improved activity and physical properties, with the 
 12
attribute of inhibiting unwanted side reactions such as paraffins and aromatics 
formations.   
 Fougret and Holderich (2001) in the hydration of ethylene over metal phosphates 
impregnated with phosphoric acid, found that impregnated aluminum, zirconium and 
cerium phosphate catalysts showed higher conversions than phosphoric acid on silica gel.  
In the case of impregnated aluminum phosphate, it was shown that the acidity of AlPO
4
 
carrier determined by TPD of ammonia decreased dramatically during the impregnation 
process.  They concluded the acidity was more dependent upon the existence of liquid 
phosphoric acid on the surface of the carriers.  
 Inui and Kang (1997) observed that the incorporation of nickel into the tetrahedral 
framework positions of SAPO-34 leads to a higher selectivity towards ethylene.  They 
attributed the higher selectivity to framework distortion and acidity modification after the 
nickel incorporation. 
 Coke formation inside catalyst pore often plays a major factor in the deactivation 
of SAPO catalyst.  Dubois et al (2003) studied SAPO-34 modified with Ni, Mn, Co, and 
Ni-SAPO-34.  While these catalysts exhibited activities and selectivities towards ethylene 
through butene, they concluded SAPO-34 modified with Mn (MnSAPO-34) to be better 
based on the catalyst?s lifetime (TOS = 54 hr).  And as for the two Ni containing 
catalysts, they noticed a major difference in the methane present in the product.  They 
thought the difference could be due to the Ni location inside the catalyst and suggested 
this might be an interesting and convenient way to improve catalyst lifetime for MTO 
reaction. 
 
 
 13
Effect of Acid  
 
The aluminophosphate (AlPO) framework is neutral, therefore AlPOs exhibit no 
acidity, which restricts their use as acid catalysts.  However, introduction of silicon atoms 
into the framework results in Br?nsted acidity and these silicoaluminophosphates 
(SAPOs) can be used as acid catalysts.  For instance, substituting either the P or Al for a 
metal - Si, for instance - the framework becomes electrically negative and therefore 
possesses acidic properties (Derouane et al, 1988; Flanigan et al, 1986).  Also, increasing 
the silicon amount can lead to a high acidity, therefore control of the SAPO synthesis is 
of extreme importance in order to obtain a high silicon content catalyst.  
Chen et al (1994) prepared and studied samples of SAPO-5, SAPO-17, SAPO-18, 
and SAPO-34 to understand their Br?nsted acidity.  Using DRIFT spectroscopy for 
analysis, it turned out that the acidic strength present in the samples was in the following 
order SAPO-5 < SAPO-17 < SAPO-18 < SAPO-34.  They found that smaller cages 
SAPO-18 and SAPO-34 yielded higher activity and selectivity towards olefins for the 
MTO reaction than samples SAPO-5 and SAPO-17.  However, among the samples - 
SAPO-5 exhibited the longest life time because the accumulation of coke is less 
favorable for its one-dimensional 12 ring channels. 
Inui and Kang (1997) incorporated crystal ingredients P, Si, and Ni into the 
framework of SAPO-34, and they concluded that the crystallites with the solid acid 
density distributed within their framework exhibited the highest ethylene selectivity 
(88%).  These crystals also exhibited a minor deactivation due to the lower amounts of 
coke formation primarily to no space-restrictions on the external surface that would 
facilitate the growth of bulky aromatic coke. 
 14
Hocevar et al., 1993, incorporated MeAPSO-44 with: Co, Mn, Cr, Zn, and Mg. 
These metal incorporated catalysts were investigated for their acidity and catalytic 
activity along with SAPO-44, AlPO
4
-5 and AlPO
4
-14 molecular sieves and compared 
with SAPO-34 and NiAPSO-34.  And the order of acidic strength was determined as 
follows: MnAPSO-44 > CoAPSO-44 ~ ZnAPSO-44 > MgAPSO-44 > CrAPSO-44 > 
SAPO-44 >> AlPO
4
-5 ~ AlPO
4
-14.  As for catalytic activity, the order was as follows: 
AlPO
4
-14 > AlPO
4
-5 ~ SAPO-44 > CoAPSO-44 > MnAPSO-44.  AlPO
4
-14 which 
showed the least acidic strength displayed the highest catalytic activity, where MnAPSO-
44 followed the opposite trend.  However, among the samples investigated, CoAPSO-44 
exhibited the highest selectivity towards ethylene production.  The authors concluded that 
metal type could play a role in degree of selectivity.  However, when samples MeAPSO-
44 and MeAPSO-34 were compared side by side, the -44 structures were 3 times more 
selective to olefins than the -34 structures.   
 
 
Template (Structure Directing Agent) 
 
One particular useful strategy in the formation and design of new microporous 
materials has been the inclusion of quaternary ammonium ions (as a hydroxide or halide 
salt) or organic amines in the synthesis mixture.  These organic guest molecules act as 
structure directing agents and are incorporated into the final product where they replace 
the usual charge compensating metal cations and other extra-framework molecules.  
Shape and size (Figure 2.3) of the organic guest molecules play important roles that can 
lead to the formation of new and novel microporous structures that often cannot be 
produced by any other methods.  In other words, these organic guests provide the basis 
 15
upon which host structures could be crystallized and retained the shape consistent with 
the respective template.  They fill the void space around which the framework of the 
microporous material forms but for which a particular structure can be formed by more 
than one particular type of guest molecule and guest molecules that are specific to the 
formation of a certain framework structure only.  For instance, SAPO-17 and SAPO-44 ? 
ERI and CHA, respectively ? can be synthesized with morpholine as the template; the 
same type of zeolite (CHA) may be crystallized using various templates i.e.: SAPO-34, 
SAPO-44, and SAPO-47. 
             
Figure 2.3.  View of two adjoining cages formed at channel intersections in the all-silica zeolite SSZ- 
                    23 (STT) showing the position of the structure directing agent TMAda+ around which  
                    the framework forms.  (Attfield, 2002) 
 
Tetrapropylammonium and tetraethylammonium hydroxides are good templates 
for obtaining CHA structures.  Diethylethanolamine and cyclohexylamine may also act as 
templates giving rise to more or less pure phases.  Morpholine and methylbutylamine 
exhibit appreciable selectivities towards the formation of pure SAPO-34 and SAPO-47, 
respectively (Dumitriu et al., 1977).   
But obtaining pure phases of a particular SAPO can be tricky as factors such as 
chemical concentration, pH value of the synthesis gel, and sequence of chemical mixing 
 16
impact significantly the final product.  For instance the order of chemical mixing can 
determine whether a pure phase or combination of phases is realized.  Although SAPO-
34 could be synthesized with piperidine as a template, Dumitriu et al (1977) had found 
that SAPO-34 and SAPO-20 were competing phases at high piperidine concentrations, 
whereas SAPO-3, SAPO-17 and SAPO-35 are the phases present at low template 
concentrations.      
The SAPO-5 structure can transform into the SAPO-34 structure with increase of 
crystallization time.  Jhung et al.(2003) found this to be due probably to the relative 
stability of the two phases at the reaction conditions.   But SAPO-5 can be selectively 
formed by fast crystallization of alkaline or acidic reactants gels.  
Prior to testing, catalysts must undergo calcinations to remove the organic guest 
molecules (template) present in the framework.  This is often accomplished by heating 
the material under flowing oxygen or air at temperatures greater than 400 
o
C, or in some 
instances the guest molecule can be washed out under acidic or basic conditions. During 
the template removal, some host molecules undergo structural collapse.  Collapse occurs 
when the constituent bonds of the framework are too weak to maintain the structural 
integrity of the framework without the aid of the favorable electrostatic, hydrogen 
bonding or van der Waals interactions between the components of the framework and the 
structure directing agent (Attfield, 2002).   
 
 
Coke Formation (Catalyst Deactivation) 
 
Loss of catalytic activity presents a major problem in regard to catalysis.  There 
are three main categories into which the loss of activity can be divided:  sintering or 
 17
aging, fouling or coking, and poisoning.  Of those three types, the deactivation by coking 
or fouling is common to reactions involving hydrocarbons.  Basically, coke material is 
being deposited on the surface of the catalyst as the reaction proceeds.   
Little attention was paid to this phenomenon in the early days of zeolite catalysis 
except for a few notable studies by Eberly et al. (1966).   But beginning in the late 
seventies, many papers dealing with coke formation continued to emerge due in no small 
part to industrial applications and fundamental research on zeolite catalysis. 
Voorhies, in 1945, had developed a model to quantify the amount of coke 
deposited on the surface after some time t:   
                         C
c
 = At
n
 
 
where C
c
 is the concentration of carbon on the surface and n and A are fouling parameters 
dependent of the feed rate.  This model has been found to hold for a wide variety of 
catalysts.   
The deactivation of all zeolites has been considered to occur in three ways 
depending on the coke content (Chen et al., 1994):  
           (a) Limited access for the reactant molecules on the active sites (site coverage); 
           (b) blockage of the access to the active sites in the cavities (or in the channel      
                 intersections) where coke molecules are located;  
           (c) blockage of the access to the active sites in the cavities (or in the channel  
                intersections) where there are no coke molecules.   
 
Coke by its nature appears to be mainly paraffinic, but polycyclic aromatics have 
been found to be present as well (Aguayo et al., 1999).  Eisenbach and Gallei (1974) 
visualized this process as the build-up of very bulky, polyaromatic systems with even 
graphite-like structure.  Other aspects of their presence offered new insight into their 
nature.  According to Froment et al. (1992), the deactivation by coke and its effect on the 
 18
product selectivities depend on the way the coke is deposited on the catalyst.  Bos et al. 
(1995) developed a kinetic model for the MTO process based on small pore molecular 
sieve catalyst of the class SAPO-34.  They have found the coke content of the catalyst to 
be the main factor governing selectivity and activity of the catalyst.   
One other way in understanding catalyst deactivation has to account for one 
important factor: pore structure. Because these small-pore zeolites adsorb linear 
hydrocarbons but exclude the larger branched or aromatic hydrocarbons, these bulkier 
species, when formed internally, cannot diffuse out.  Since Sahini and Tsotsis (1985) 
recognized that catalyst deactivation is a percolation phenomenon, a number of 
approaches have used the percolation concepts for modeling catalyst deactivation (Mann 
et al., 1986; Beyne et al., 1990, 1993). 
Chen et al. (1994) have recently studied the role of coke deposition in the 
conversion of MeOH to olefins over SAPO-34.  They found that the coke formed from 
oxygenates, referred to as active coke, promoted olefin formation, while the coke formed 
from olefins, referred to as inactive coke, only had a deactivating effect.   In addition 
coke was found to reduce the DME diffusivity, which enhances the formation of olefins, 
particularly ethylene (Wilson and Barger, 1999).  
 
 
Role of Water  
 
To control product distribution and diminish coke effect over time in the course of 
catalytic reactions, methanol is often coupled with water in the feed stream.  It has been 
proposed that the presence of water in the feed lessens coke formation, either by 
 19
converting Lewis to Br?nsted sites or by competing for surface sites with coke precursors 
(Aguayo et al., 1999).    
When the reaction is carried out with SAPO-34, Liang et al. (1990) and Marchi 
and Froment (1991) have proven that the presence of water in the feed gives way to a 
considerable increase in the selectivity to olefins C
2 
- C
4
, which is not observed when 
nitrogen is used as the diluent.  Froment et al. (1992) attribute this result to the 
competition of water against olefins for adsorption on the strong acid sites.   
Also water present in the zeolite nanocage significantly increases ethylene 
selectivity at the expense of propene, and that has been attributed to enhanced state shape 
selectivity.  According to Song et al. (2001) co-feeding of water with methanol 
significantly increased the average number of methyl groups per ring at steady state 
relative to identical conditions without additional water, and also increased ethylene 
selectivity, apparently through transition state shape selectivity (Figure 2.2(c)). 
Zhao and Wojciechowski (1996) carried out a rigorous study which has proven 
that an alteration in the mechanism of 2-methylpentane cracking over USHY zeolite 
occurs because of the presence of water in the reaction medium.  In the MTO process on 
HZSM-5 zeolite, the presence of water gives way to an increase in the selectivity to light 
olefins (by decreasing the formation of aromatics) and also changes their distribution by 
increasing the ethene selectivity.   
 
Catalyst Regeneration 
 
Many studies have shown thermal treatment to be effective in reversing coking 
effects and prolonging reaction operation.  This technique is sometimes used in 
 20
conjunction with a fluidized bed scheme where spent catalyst can be re-circulated along 
the reactor to be treated at elevated temperature.  For example, it has been found that 
spent catalyst completely recovers its activity by burning the deposited coke with air at a 
temperature of 823 K when operating in reaction generation cycles (Gayubo et al., 2000). 
Temperature choice is significant in catalyst regeneration.  Cai et al. (1995) had 
found that catalysts regenerated at temperature higher than 550 
o
C took much shorter to 
decoke (10 min) compared to those treated at lower than 550 
o
C (30 min).  The activity 
and selectivity of the catalyst are almost the same as those of the fresh catalysts after long 
time treatment in steam or in air flow at 800 
o
C.  X-ray diffraction results show only little 
decrease of the crystallinity of the treated samples, as compared with that of the fresh 
catalysts.   
 This strategy is considered as the most suitable by Mobil for the MTO process on 
ZSM-5 zeolites.  However, results for on-stream testing in a fixed bed reactor shows that 
activity of SAPO-34 had decreased within about 2 hr under the reaction conditions 450 
o
C, WHSV (MeOH) = 0.6hr
-1
.  Thermal treating of the catalyst in a stream of air at 500 
o
C ? 650 
o
C completely restores its activity (Cai et al., 1995).  
 
 
SilicoAluminoPhosphate (SAPO) 
 
Small pore molecular sieves such as SAPO-34 have been the subjects of extensive 
studies primarily due to their inclination for lower olefins selectivity and high activity 
(Wilson and Barger, 1999).  Depending on the reaction conditions, lower olefins 
selectivity up to 90% could be easily achieved at 100% methanol conversion.  Such 
selectivity performance is attributed to their narrow pore structures.  However, their high 
 21
activity is primarily due to the high Br?nsted acidity arising from isolated silicon 
substitution for framework phosphorus.  Other small pore molecular sieves include 
SAPO-44 and SAPO-47 with an 8 oxygen ring and a pore aperture of 0.35 ? 0.45 mm.  
SAPO-34, SAPO-44 and SAPO-47 are analogs of the Chabazite Structure (CHA) 
with stacking sequence of AABBCC; cell dimensions of a = 13.675 ? and c = 14.767 ?; 
space group R3m; and the number of atoms per unit cell (Z) = 36.  SAPO-56 on the other 
hand, is a novel type catalyst.  Although it is classified as a small molecular sieve, it 
belongs to the (AFX) structure type with a stacking sequence of AABBCCBB formation 
with cell dimensions of a = 13.674 ?, c = 19.695 ? and space group of P6
3
/mmc with Z 
(atoms per unit cell) = 48.  But its pore size is equivalent to that of SAPO-34 at 0.43 nm 
with 8-oxygen ring size (Wilson et al., 1999).  
 
 
Particle Size and Shape  
 
Particle size and shape are of primary importance because they determine a wide 
range of physical and chemical properties. Both the particle size distribution and the 
particular shape have a strong effect on particle product quality.  For example, in the area 
of drug delivery, the degree and rate at which a substance is absorbed into a living system 
or is made available at the site of physiological activity often depends on both the particle 
size and shape. In paint opacity is a function of size, whereas coating layer properties are 
a function of the shape distribution (Lohmander, 2000).  In catalysis, shape is important 
because it affects catalyst effectiveness (Buffham, 2000).   
Crystal size and, more importantly, the crystal pore size, have major influences in 
the catalysis deactivation rate and life (Wison and Barger, 1999).  The strict pore 
 22
restriction imposed by small aperture crystals enable the buildup of branched compounds 
inside the compounds triggering secondary reactions which facilitates coke deposits 
inside the pores and ultimately the rapid deactivation of the catalysts (Guisnet, 2002).  In 
the process, olefins production which is highly desirable is often suppressed. 
Another important factor in particle analysis is particle breakage.  It is of interest 
because it occurs both naturally and in many manufacturing processes.  These processes 
span a range of industries including pharmaceuticals, pigments, agricultural chemicals, 
and foods.  It is of particular interest in chemical processing plants because it can have a 
strong impact on unit operations.  Breakage may be beneficial and intentional as in the 
case of crushing; or it may be detrimental and unintentional as in the case of 
fragmentation and attrition in fluidized bed reactors and combustors (Shamlou et al., 
1990). 
 According to Miller (1994) and Campello and Lafont (1995) the geometry and the 
size of the SAPO channels were found to be a prerequisite for the preferential formation 
of monobranched alkane isomers.  They noted further that medium-pore 
silicoaluminophosphate molecular sieves were found to be most suitable for the selective 
hydroisomerization of linear alkanes.  From a comparative study of large and small 
crystals of Pt/SAPO-11 it was concluded that small crystals were more active in the 
hydroisomerization of n-octane owing to the higher number of pore entrances present as 
the crystal size decreases (Miller, 1992).  It was hence suggested that parameters such as 
the acidity, the pore structure and the grain size of SAPO catalysts could affect their 
hydro-isomerization behavior. 
 23
 While catalyst grain size can be influenced greatly during the synthesis phase of 
preparation, mechanical treatment (ball milling) of fresh catalyst particles also lends itself 
as a viable route for obtaining much smaller particle size.  In addition to the lowering of 
particle size, other advantages offered by this method include: increase of specific surface 
area and change in particle morphology.   Kosanovic et al. (1992) studied the effect of 
mechanical treatment on physicochemical properties of several zeolites.  XRD analysis of 
the treated particles revealed loss of crystallinity indicated by the decrease of the peak 
intensities as a function of milling time.  SEM analysis of one of the samples showed 
formation of polydispersed powder with irregular particle shape.  IR spectra during the 
ball mill showed decrease of cation-exchange capacity and an increase of solubility 
caused by breaking of Si-O-Si and Si-O-Al bonds in the zeolite structure.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 24
III. EXPERIMENTAL 
 
 
 
Samples Preparation 
 
All original SAPO catalysts utilized for this research were prepared by Dr. 
Prakash M. Adekkanattu based on information provided on the literature with the 
following chemicals: orthophosphoric acid (85 wt %), aluminum isopropoxide (98+ %), 
pseudoboehmite (Catapal-B, 70 wt % Al
2
O
3
), fumed silica (99.8 wt %, 380 m
2
/ g), 
colloidal silica (Ludox LS, 30 wt %), nickel acetate tetra hydrate (99.98 wt %), 
cyclohexylamine (99+ wt%), NN-diisopropylethylamine (99 wt%), morpholine (99+ wt 
%), tetraethylammonium hydroxide (30 wt % in water), methylbutylamine (96 wt %), 
N,N,N
?
,N
?
 -tetramethylhexane 1,6-diamine (99 wt %). All the chemicals except 
pseudoboehmite were from Aldrich. Pseudoboehmite was from Vista.  Detailed 
information including temperature, crystallization time, pH, and gel composition for all 
samples in addition to XRD analysis can be found in a report submitted by Adekkanattu, 
(2003).  
 
Modified Catalysts 
Three samples (SAPO-34, SAPO-44, and SAPO-56) were sent to Dr. Richard 
Ernst at the University of Utah to be impregnated with ruthenium using a vapor phase 
vacuum technique (Wilson et al., 1986).  Appropriate amounts of bis (2,4-
dimethylpentadienyl) ruthenium were added to each sample to give a 1% Ru load. The 
 25
SAPO-56 sample incorporated the Ru compound relatively quickly - within 16 hrs. The 
SAPO-44 incorporated the Ru compound over 72 hrs and the SAPO-34 never fully 
incorporated the Ru compound, even at 40 ?C for 168 hours.   All the samples took on a 
yellow color after incorporation.  After the incorporation each sample underwent an 
oxidation step where colors changed to either black or charcoal gray. 
 
Particle Characterization 
 For characterization purposes SEM analysis was performed at the Auburn 
University Research Instrumentation Facility.  Samples were studied by scanning with a 
Zeiss DSM940 microscope.  Prior to introducing samples inside the machine chamber, 
particles were treated with a gold coating.   
 Because of the large amount of agglomerates formed when particles undergo 
mechanical treatment (grinding operation), samples were often mixed with acetone then 
sonicated prior to SEM analysis in order to spread particles for proper size 
characterization.  
 
SAPO-47 Fractionation 
 Particle sizes revealed by SEM observation for SAPO-47 were not as uniform as  
other SAPOs analyzed.  With that in mind, it was decided that particles should be 
separated into their respective sizes and tested in catalytic reactions.  Results from those   
various size particles would be analyzed and compared with ground particles.  Particles 
were separated by water settling and divided into two sets: coarse and finer fractions. 
 
 26
Grinding of Particles 
 In order to achieve smaller sized particles, use of planetary ball mills is often 
required to reduce the particle size.  Ball milling is recognized as an efficient way to 
optimize powder properties (Kano, J. et al., 1998).  For our study we employed a grinder 
(Wig-L-Bug, Model 30, #3110-3A) from Dentsply/Rinn (Figure A-2) to enable us to 
process small amounts of samples available for experiments.  This machine operates at 
3200 RPM with 110V, 0.65 Amp and 60 Hz.  Sample preparation can be reproduced 
from sample to sample by replicating the cycle time.  Grinding operation is controlled by 
a 30-min timer or manual button.   
 The grinder comes with a small agate vial (1 5/16
?
 h x 9/16
?
 dia.) and a capacity 
of approximately 2 ml.  Once the sample is placed inside the vial, a small ball (about 1/4? 
dia.) is added to the sample and the vial is tightly capped with the cover.  Finally, it is 
mounted and securely seated on the grinder.  When the system is operating the sample 
material is hit alternately from various sides by the grinding ball while the grinder 
performs radial vibrations in a horizontal setting. 
SEM analysis revealed extensive particle size reduction after grinding operations.  
For SAPO-34 and SAPO-44, effect of grinding time on product distribution and catalyst 
activity was studied.  Grinding times (GT) were chosen as: 5, 10, and 15 minutes.   
Because of the finer sized particle resulting from the grinding process and the 
void constraints imposed by the particle contacts, reactions over ground particles often 
experienced great pressure drop and brief flow fluctuation as a consequence (Figure 3.1). 
      
 
 27
  
Figure 3.1.  Left-hand legend, reacting fluid channels out freely without difficulty around catalyst  
                    particles.  Right-hand legend, fluid moves along particles with great difficulty.  
 
 
Standard Analysis (Olefins, Paraffins, DME and MeOH) 
 Knowing that products resulting from the MTO catalytic reactions consist 
primarily of olefins and paraffins and oxygenates, a set of calibrations was devised so 
that accurate recognition of the resulting peaks could be obtained.   Using a syringe 
(SGE, P/N 005250, 100?l) a 100 ?l sample was extracted from a mixture of C
2
 ? C
6
 
olefins (Matheson Tri-Gas, GMT10358TC) then injected into the GC for calibration.  The 
same procedure was repeated for the C
1 
? C
6
 paraffins (Matheson Tri-Gas, 
GMT10411TC).  From this operation, retention time values for each compound were 
obtained and recorded for olefins and paraffins.  The area under each peak represents 
large quantities of ions proportional to the number of organic molecules for each organic 
compound present (Table 3.1, Figure 3.2). 
 
 
Figure  3.2.  GC Profile of Olefins Standard. 
 
 
C
2
= 
C
3
= 
C
4
= C
5
= C
6
=
 28
Table  3.1.  Retention Times for Olefins Components. 
Component Symbol Retention Time (min) Area Area % 
Ethylene C
2
= 1.433 89.003 12.422 
Propylene C
3
= 8.933 125.471 17.512 
1-Butene C
4
= 17.166 161.497 22.541 
1-Pentene C
5
= 20.933 174.431 24.346 
1-Hexene C
6
= 24.066 166.067 23.179 
  
 
Figure  3.3.  GC Profile of Paraffins Standard. 
 
Table  3.2.  Retention Times for Paraffins Components. 
Component Symbol Retention Time (min) Area Area % 
Methane C
1
- 0.75 50.888 7.237 
Ethane C
2
- 1.85 88.531 12.591 
Propane C
3
- 10.133 134.783 19.169 
Butane C
4
- 17.55 149.33 21.238 
Pentane C
5
- 21.233 152.396 21.674 
Hexane C
6
- 24.316 127.193 18.09 
 
 
Retention times determination for methanol (MeOH) and dimethyl ether (DME) 
followed differently.  In the case of methanol, with no catalyst inside the reactor tube, 
both N
2 
and  MeOH ( set at 36.0 sccm and 0.003 ml/min -  respectively ) were allowed to 
flow at 400
o
C and atmospheric pressure.  One hour later a sample (exactly 100 ?l) was 
extracted from the collection point of the reactor and injected into the GC FID port to 
obtain the MeOH retention time.  For dimethyl ether, 1.0 ml. of pure DME was injected 
into a nitrogen filled glass collecting bulb (V = 29.7 ml.) and allowed to mix (N
2
 + DME) 
C
1
_
 
C
2
_
 
C
3
_
 
C
4
_
C
5
_
C
6
_
 29
for about 60 minutes.  From that mixture 100 ?l was extracted, and then injected into the 
FID port of the GC to obtain the DME retention time. 
 
Figure  3.4.  GC Profile of Methanol (MeOH) Standard. 
 
Table  3.3.  Retention Times for Methanol (MeOH). 
Component Symbol Retention Time (min) Area Area % 
Methanol MeOH 15.433 1252.2 100 
 
 
Figure  3.5.  GC Profile of Dimethyl Ether (DME) Standard. 
 
Table  3.4.  Retention Times for Dimethyl Ether (DME) Component. 
Component Symbol Retention Time (min) Area Area % 
Dimethyl Ether  DME 13.183 1457.09 92.4737 
Other  15.933 118.59 7.5263 
 
 
3.7  Product Analysis (Actual Runs) 
 Product composition was analyzed by a GC (Varian 3000) equipped with a Flame 
Ionization Detector (FID) using a Plot-Q capillary column (Agilent, P/N: 19095P-Q04, 
MeOH
DME
 30
S/N: 60231117) with column length being 30 m, inside diameter being 0.543 mm, and 
film thickness about 40.0 ?m.  This is a polystyrene-divinylbenzene bonded based 
column made specifically for hydrocarbon (Olefins, Paraffins, and Oxygenates) 
separation.    
As reactions proceeded, manual injections were made hourly into the GC.  Data 
handling was performed by PeakSimple Chromatography Data Systems (Model 203, 220 
V) mounted in the GC via a 20-bit high resolution A/D board.  Data can be acquired at 
the rate of 50 Hz in one channel.  Each separated component is identifiable from their 
characteristic retention time.  PeakSimple software enables quick and easy data analysis 
which otherwise would have required enormous amount of time such as when an 
HP3396A integrator was employed for this task.  After the reaction stopped, data were 
translated into an Excel spreadsheet for product analysis (Figure 3.6).  Detailed 
information about the calculations can be found in Appendix C. 
 31
 
Figure  3.6.  Spreadsheet for MTO Analysis. 
 
Reaction Procedures 
 MTO reactions were performed in a quartz tube, fixed-bed reactor (Figures 3.7 
and 3.8).  The process was continuous and pressure was maintained at 1 atm.  
Temperature was kept fixed at specific designated setpoint, 400 
o
C.  Prior to catalytic 
testing, 0.307 (+/- 0.003) g was loaded inside the quartz tube reactor firmly held between 
two pieces of quartz wool to secure it in place.  If wool was too tightly pressed, a large 
pressure drop resulted.   This is often the case when ground particles are in the bed even 
when the wool plugs are not too tight. The reactor tube is then placed inside the furnace 
(Lindberg/Blue, TP55035A - 1) equipped with a UP 150 Controller.  Nitrogen (carrier 
gas) flow is turned on to precondition the catalyst for about 1 hr.  During this time, soap 
 32
bubble (Snoop) solution is used to check for possible gas leak(s) along the reactor lines.  
In the second hour the furnace is turned on.  It takes about 1 hour for the furnace to reach 
the setpoint (reaction temperature).  Temperature was monitored by a thermocouple 
placed in a quartz probe well inside the catalyst bed.  The temperature observed in the 
catalyst bed (400 
o
C) was always greater than the furnace temperature setpoint (384 
o
C).  
When the catalyst bed temperature (400 
o
C) was reached liquid methanol was pumped 
(KD Scientific, SN. 12953, Model 101) to the system at a rate of 3 ?l/min (0.003 
ml/min).  Up to this point 3.0 hours have already elapsed plus an additional 1 hour before 
the first data point is taken for analysis.  For every data point, a check is made for leaks 
as mentioned before and effluent gas flow was measured via the bubble flow meter and 
recorded. 
                 
Temperature Probe Well
Catalyst Bed
Quartz Wool
Collection Point
L = 81.2 cm
I.D. = 0.95 cm
Inlet
Outlet
 
Figure 3.7.  Close-Up View of the Quartz Tube Reactor 
 33
  
   O     O
  
Temperature
Gauges
Methanol
Pump
Bubble Flow
Meter
Nitrogen
Tank
SAPO
Catalyst
Three-Way
Valve
Flow
Regulator
Relief
Valve
Water
Trap
Collection
Point
Flow 
Reading 
Furnace
Quartz Tube
Reactor
High Temp Zone
Pressure
Indicator
Collection Bottles
Temperature Controller
Rotameter
Two-Way
Valve
Heating Tape
 
Figure  3.8. MTO Reactor Diagram. 
 
 
Figure  3.9.  GC Product Distribution Profile Over SAPO-47 (P-31), (Finer Particles), Temp=400
o
C. 
C
1
_
 
C
2
= 
C
2
_
 
C
3
=
C
3
_
DME
MeOH
C
4
=
C
4
_
 
C
5
= 
C
5
_
 
C
6
=
 34
 
Table  3.5.  MTO Product Distribution over SAPO-47 (P-31), (Finer Particles). 
                   
Component Symbol Retention Time Area Area %
(min)
Methane C
1
_
0.716 14.798 0.9361
Ethylene C
2
= 1.4 587.254 37.1495
Ethane C
2
_
1.783 15.688 0.9924
Propylene C
3
= 8.433 584.44 36.9715
Propane C
3
_
9.7 63.769 4.034
Dimethyl Ether DME 13.75 36.624 2.3168
Methanol MeOH 15.966 55.158 3.4893
Butene C
4
= 16.95 36.79 2.3273
17.25 8.154 0.5158
Butane C
4
_
17.366 139.684 8.8364
Pentene C
5
= 19.3 1.003 0.0634
19.483 4.206 0.2661
Pentane C
5
_
19.65 28.501 1.803
Hexene C
6
= 22.083 4.718 0.2985
 
 
 Temperature Method 
This study was conducted primarily to assess temperature effects on product 
distribution, and catalyst deactivation.  Dubois (2002), in her thesis, undertook such a 
study over SAPO-34.   Here, however, we extend that study to SAPO-44 and SAPO-56.  
Basically, the idea is same as we had done in other experiments with WHSV being the 
same (about 0.5 hr
-1
), except temperature is varied from 300 
o
C to 500 
o
C at 50 
o
C 
increments.  At each temperature, reaction was allowed to run for one hour before sample 
extraction.  After sample extraction, the temperature was raised to the next temperature 
setpoint and reaction was again allowed to proceed for another hour before the next 
extraction.  This process was repeated until temperature had reached 500 
o
C.  
 35
IV. RESULTS AND DISCUSSIONS 
 
 
 
 In this section details of the MTO experiments will be analyzed and the results 
will be compared with related works by Dubois (2002) and Adekkanattu (2003).  Catalyst 
particles were analyzed using SEM.  In addition three of the original SAPO samples were 
incorporated with ruthenium (SAPO-34, -44, and -56(0.6 Si)) in Dr. Richard Ernst?s lab 
at the University of Utah.  These incorporated samples were investigated to confirm if the 
ruthenium did indeed confer any improvement in the catalysts? performance.   
 All reactions reported here were operated under atmospheric pressure, with 
methanol delivery at a rate of 0.003 ml/min, and a catalyst loading of 0.307 (+ / - 0.003) 
g.  Catalyst bed temperature was maintained at 400 
o
C.  To ensure that a good separation 
of olefins and paraffins components derived from the product mixture takes place, the GC 
was set with the following temperature program: initial temp set at 40
 o
C, hold for 10 
min, then ramp at a rate of 10
 o
C/min to 100
 o
C, hold for 15 min, again ramp at a rate of 
10
 o
C/min to finally 170
 o
C.  
 
 
SEM Analysis 
 
 All SEM micrographs can be found in Appendix B.   Examination of the 
micrographs shows distinct shape variations among all the present SAPO materials.  
SAPO-34 shows very well defined cubic morphology with particle size varying between 
12 to 14 ?m.  SAPO-44 shows intergrowth of cubic crystals to form circular or oval discs 
 36
with sizes ranging between 45 and 55 ?m.  SAPO-47 crystallized in widely varying 
crystallite sizes between 35 to 220 ?m with very irregular cubic morphology.  SAPO-56 
had been synthesized with varying silicon amounts (0.6 ? 0.9).  The effect of these silicon 
concentrations can be observed in the relative morphologies.  For instance, at low 
concentrations of (0.3 Si) the crystal takes on a hexagonal shape with sizes varying 
between 60 to 70 ?m.  However, when the silicon amount was increased to (0.6 Si) the 
crystal appears more like a disk with sizes varying between 50 to 60 ?m.  At (0.9 Si) the 
crystal shape approaches more of a doughnut shape with sizes varying between 80 to 90 
?m.  Morphologies for the ruthenium modified samples are very close to the 
corresponding unmodified types. 
 
Scale-Down Analysis 
In earlier studies it was common practice to use 500 mg of SAPO as a standard 
loading capacity for each run while the nitrogen and methanol were maintained at 60 
sccm and 0.005 ml/min, respectively, with weight hourly space velocity (WHSV) 
maintained at 0.5 hr
-1
.  However, anticipating continued use of such a quantity would 
rapidly deplete our catalyst stockpile, we decided as a first task to conduct a scale-down 
analysis to ascertain as to whether any significant difference would occur both in terms of 
catalyst activity and  product distribution profile.  For this analysis, 40% less catalyst 
(300 mg) was charged in the reactor.  Similarly, nitrogen and methanol flows were scaled 
back by the same factor (40%) thereby ensuring same WHSV of 0.5 hr
-1
 in both 
operations.  This study can appropriately be summarized as follows:  
 
 37
a) Standard method (Load = 500 g, N
2
 flow = 60 ml/min, MeOH feed = 0.005  
      ml/min) 
b) Scale-down method (Load = 300 g, N
2
 flow = 36 ml/min, MeOH feed = 0.003  
      ml/min) 
 
The catalyst of choice for this study was SAPO-56 (0.6 Si).  While a similar study 
was conducted on CoSAPO-34, our discussion in this section refers exclusively to results 
from the SAPO-56 (0.6 Si) experiments. 
Figures 4.1 and 4.2 depict results for activity over SAPO-56 (0.6 Si).  From these 
figures it seems obvious that both catalysts exhibited similar profiles.  From hour 6 and 
beyond both DME and MeOH reached their plateau (Figure 4.1) where they maintained 
the same levels for the remainder of the experiment.  Judging from that result it became 
logical that a similar trend or pattern would follow in Figure 4.2 so this experiment was 
immediately stopped at the 7
th
 hr.    
0
10
20
30
40
50
60
70
80
90
100
0123456789101
Time on Stream, hr
Mol %
Ethylene
Propylene
C2-C4 olefins
MeOH
DME
Methane
 
Figure 4.1.  Distribution of Ethylene, Propylene, C
2  
--C
4
 Olefins, DME, and MeOH, (SAPO-56) 
                    (P-18), (0.6 Si), Temp = 450 
o
C, MeOH Flow = 0.005ml/min, Load = 0.504 g,  
                    WHSV = 0.5 hr
-1
) 
 
 38
0
10
20
30
40
50
60
70
80
90
100
0123456789101
Time on Stream, hr
Mo
l %
Ethylene
Propylene
C2-C4 olefins
MeOH
DME
Methane
 
Figure 4.2.  Distribution of Ethylene, Propylene, C
2 
-- C
4
 Olefins, DME, and MeOH 
                    (SAPO-56), (P-18), (0.6 Si), Temp = 450 
o
C, MeOH Flow = 0.003m./min, Load = 0.307 g,  
                    WHSV = 0.5 hr
-1
) 
 
In both experiments, the catalyst remained active for the first 4 hrs and profiles 
for both experiments looked almost identical.  A closer look reveals some slight 
differences.  C
2
 to C
4
 yields in Figure 4.2 appear a little bit higher than in Figure 4.1 
signaling slightly more olefins is produced during that time.  Also, Figure 4.2 shows 
complete deactivation starts in hour 6 compared to hour 5 in Figure 4.1.  Both DME and 
MeOH appeared early on in the 1
st
 hr in Figure 4.2, then dropped in the 2
nd
 hr and then 
increased thereafter.     
 
 
Temperature Studies 
 
 In this study both the effects of coke formation brought about by temperature 
increase and product distribution due to rapid oligomers quenching were studied over a 
wide range of temperature from an initial 300 
o
C with an increment of 50 
o
C to a 
 39
maximum of 500 
o
C.  The reactions were performed over SAPO-34, SAPO-44, and 
SAPO-56 (0.6 Si).   
 
 
Temperature Study (SAPO-34), (P-5) 
 
 Figures 4.3 and 4.4 show product distribution at each temperature point for 
SAPO-34.  Over the temperature range chosen, 300 
o
C seems to be the best operating 
condition where significant amounts of olefins C
2
 to C
4
 were produced.  However, 
increasing the temperature to 350 
o
C and higher (Figure 4.3) resulted in significantly 
lower methanol conversion.  Since higher temperatures favor faster catalyst deactivation 
due to coke formation and lower selectivity to olefins, in the present study we did not 
expect olefins formation to precipitously drop that rapidly with temperature rise.  Dubois 
(2002) in conducting a similar study found olefins amounts at each temperature tested 
which is counter to what is experienced here. 
In Figure 4.4, however, where particles undergo grinding treatment we found 
improvements both in catalyst activity and product distribution.  Unlike the previous case 
where no olefins were detected beyond the initial temperature of (300 
o
C), here olefins 
products were still present up to temperature of 400 
o
C.  As temperature rose to 450 
o
C 
and higher, both DME and MeOH became the dominant components in the product 
stream.  However, DME was present at a far higher level than MeOH, 70% to 27% at 450 
o
C and 65% to 34% at 500 
o
C, respectively.    
 
 40
 
0
10
20
30
40
50
60
70
80
90
100
C1 C2 C3
300 C
    C4
C5+
DM
E
MeOH
C1 C2 C3
350 C
    C4
C5+
DM
E
MeOH
C1 C2 C3
400 C
    C4
C5+
DM
E
MeOH
C1 C2 C3
450 C
    C4
C5+
DM
E
MeOH
C1 C2 C3
500 C   C4
C5+
DM
E
MeOH
Mo
l %
MeOH
DME
C5+
Paraffin
Olefin
 
Figure  4.3  Temperature Effect on Product Distribution.  SAPO-34 (P-5), No Grinding. 
 
0
10
20
30
40
50
60
70
80
90
100
C1 C2 C3
300 C    C4
C5
+
DME
MeOH
C1 C2 C3
350 C    C4
C5
+
DME
MeOH
C1 C2 C3
400 C    C4
C5
+
DME
MeOH
C1 C2 C3
450 C    C4
C5
+
DME
MeOH
C1 C2 C3
500 C   C4
C5
+
DME
MeOH
Mol
 %
Olefin Paraffin C5+ DME MeOH
 
Figure  4.4.  Temperature Effect on Product Distribution. SAPO-34 (P-5), After 15 min Grinding. 
Catalyst = SAPO-34
WHSV   = 0.5 hr
-1
 
Temp     = 400
o
C 
Catalyst = SAPO-34
WHSV   = 0.5 hr
-1
 
Temp     = 400
o
C 
 41
Temperature Study (SAPO-44), (P-6) 
 In addition to SAPO-34, a temperature study was also conducted over SAPO-44. 
Like SAPO-34, all operating conditions were the same: nitrogen flow, methanol flow, 
and temperature range.    
 In the case of SAPO-44, both olefins and paraffins components were continually 
present in the product stream over the temperature spectrum for the original size particles.  
But as the temperature increased (Figure 4.5), these amounts decreased along with an 
increase of methanol suggesting incomplete methanol conversion.  DME amounts 
fluctuated over the same temperature range, from a high 27% at 350 
o
C then gently 
decreased to a low 14% at 400 
o
C and came right back up to a high of 28% at 500 
o
C.  
This behavior is reasonable because DME is an intermediate in the MTO reaction.  Low 
olefins conversion occurred at 350 
o
C and deactivation was observed at 500 
o
C 
accompanied by high DME amounts. 
 Both the yield and catalytic activity over SAPO-44 particles greatly 
increased (Figure 4.6) after grinding.  Olefins distribution remained significant 
throughout except at 500 
o
C where both DME and MeOH became dominant components 
in the product stream.  This catalyst showed great resistance to DME and MeOH 
runaways.  Of the five temperature points, 450 
o
C seemed to be the best operating point 
where ethylene to propylene ratio was highest.  Overall both DME and MeOH were 
present early on, but at relatively low levels compared to olefin levels.    
 
 42
0
10
20
30
40
50
60
70
80
90
100
C1 C2 C3
300 C    C4
C5
+
DME
MeOH
C1 C2 C3
350 C    C4
C5
+
DME
MeOH
C1 C2 C3
400 C    C4
C5
+
DME
MeOH
C1 C2 C3
450 C    C4
C5
+
DME
MeOH
C1 C2 C3
500 C   C4
C5
+
DME
MeOH
Mol
 %
Olefin Paraffin C5+ DME MeOH
 
Figure  4.5.  Temperature Effect on Product Distribution.  SAPO-44 (P-6), No Grinding. 
 
0
10
20
30
40
50
60
70
80
90
100
C1 C2 C3
300 C    C4
C5
+
DME
MeOH
C1 C2 C3
350 C    C4
C5
+
DME
MeOH
C1 C2 C3
400 C    C4
C5
+
DME
MeOH
C1 C2 C3
450 C    C4
C5
+
DME
MeOH
C1 C2 C3
500 C   C4
C5
+
DME
MeOH
Mol
 %
Olefin Paraffin C5+ DME MeOH
 
Figure  4.6.  Temperature Effect on Product Distribution.  SAPO-44 (P-6), After 15 min Grinding. 
 
Catalyst = SAPO-44  
WHSV   = 0.5 hr
-1
 
Temp = 400
o
C
Catalyst = SAPO-44
WHSV   = 0.5 hr
-1
 
Temp     = 400
o
C 
 43
Temperature Study (SAPO-56), (P-18), (0.6 Si) 
 
 A temperature study was also conducted over SAPO-56 both before and after 
grinding.  Figures 4.7 and 4.8 show these results.  Product distribution profiles in both 
cases appear quite similar.  Throughout the temperature spectrum, except at 500 
o
C, both 
C
2
 and C
4
 were present in significant amounts.  The high olefins yield could be the result 
of oligomer cracking reactions taking place inside the catalyst pores thereby favoring 
continued olefins production.  At 500 
o
C however, these olefins decreased rapidly 
coupled with the DME and MeOH rise. 
0
10
20
30
40
50
60
70
80
90
100
C1 C2 C3
300 C    C4
C5
+
DME
MeOH
C1 C2 C3
350 C    C4
C5
+
DME
MeOH
C1 C2 C3
400 C    C4
C5
+
DME
MeOH
C1 C2 C3
450 C    C4
C5
+
DME
MeOH
C1 C2 C3
500 C   C4
C5
+
DME
MeOH
Mo
l %
Olefin Paraffin C5+ DME MeOH
 
Figure  4.7.  Temperature Effect on Product Distribution.  SAPO-56 (P-18), (0.6Si), (No Grinding). 
 
Catalyst = SAPO-56  
WHSV   = 0.5 hr
-1
 
Temp = 400
o
C
 44
0
10
20
30
40
50
60
70
80
90
100
C1 C2 C3
300 C    C4
C5
+
DME
MeOH
C1 C2 C3
350 C    C4
C5
+
DME
MeOH
C1 C2 C3
400 C    C4
C5
+
DME
MeOH
C1 C2 C3
450 C    C4
C5
+
DME
MeOH
C1 C2 C3
500 C   C4
C5
+
DME
MeOH
Mo
l %
Olefin Paraffin C5+ DME MeOH
 
Figure  4.8.  Temperature Effect on Product Distribution.  SAPO-56 (P-18), (After 15 min   
                      Grinding). 
 
Temperature studies over SAPO-34, SAPO-44, and SAPO-56 (0.6 Si) were 
carried out over a broad temperature range (300 
o
C ? 500 
o
C).  Except for SAPO-56, 
catalysts in their original size were prone to rapid deactivation very early on, even after 
the first hour of time on stream (TOS).  MeOH breakthrough appeared at the first hour 
suggesting incomplete conversion at the lowest temperature.  Particle size reduced by 
mechanical grinding significantly increased catalyst yield, activity and olefin distribution, 
however, both DME and MeOH still maintained their presence in the product stream to a 
small extent.  It could be argued that better diffusion in ground particles enabled greater 
access to active sites inside the pores thereby facilitating reactions at higher rates.  It was 
found that the best operating condition was generally somewhere between 400 
o
C to 450 
o
C.  For the catalysts tested, SAPO-44 turned out to be the best in terms of olefins 
Catalyst = SAPO-56  
WHSV   = 0.5 hr
-1
 
Temp = 400
o
C
 45
distribution before and after grinding, followed by SAPO-34 and finally SAPO-56.  
SAPO-56, however, showed no significant improvement with the product distribution 
remaining almost the same.   The effective initial particle size could perhaps be one 
reason this result is obtained.  
 
Catalytic Reaction Study 
 Given the interest in SAPO catalysts, it is fitting to extend our studies to other 
areas where our understanding of these catalysts can be further enhanced.  This process 
provides us with a greater appreciation for the complexity and intricacy of SAPO?s 
catalytic reactions.  Like SAPO-34, SAPO-44 and SAPO-47 are analogues of the 
Chabazite structure and are potential candidates for the MTO process. Of the MTO 
SAPO catalysts known to date, only SAPO-34 has shown promise of reaching the 
commercialization stage.   There still remains a lot to learn about the other SAPOs and 
research is under way in various quarters of the scientific community to learn as much as 
possible about them.   
 In addition to SAPO-34, here we will report results on SAPO-44, SAPO-47, and 
SAPO-56 (0.3 Si), SAPO-56 (0.6 Si) and SAPO-56 (0.9 Si).  For each catalyst, two 
catalytic tests were undertaken, and the effect of particle size variation on activity, 
lifetime, and selectivity is reported.  
   To study particle size effects, samples were ground for 5, 10, and 15 mins.  
Approximately 0.307 (+ / - 0.003) g of sample with a supply of 0.003 ml/min of MeOH 
were used for each reaction, which is equivalent to a WHSV of 0.5 hr
-1
.  Temperature 
was set at 400 
o
C and pressure at 1atm. 
 46
SAPO-44, (P-6)  
 
Figures 4.9 ? 4.12 illustrate profiles of product selectivity over SAPO-44 for 
different grinding conditions. In Figure 4.9 with no grinding treatment the catalyst 
remained active for nearly 6 hours.  For the first three hours, olefins production C
2
 to C
4
 
was significant and accounts for more than 60% of the overall product.  Ethylene to 
propylene ratio was a little above unity indicating selectivity towards these two 
components was about the same.  During the initial period (3hrs) both DME and MeOH 
did not appear as major constituents in the product stream.  But after the third hour there 
was a precipitous decline in MeOH conversion, and by the fourth hour almost all the 
product constituents remained flat (nearly zero) with the exception of DME which 
remained at about 13% the total product.   At the same time MeOH level in the output 
increased from a mere 15% to a high of 80% and stayed at this level until the reaction 
was stopped.  
Figure 4.10 shows the profile of product selectivity after 5 minutes of grinding. 
SEM analysis shows a great size reduction when compared with the original size 
(Appendix B, Figure B-3).  Grinding effects are clearly evident when compared to 
(Figure 4.9).  First and foremost is the catalyst activity as the reaction remained ongoing 
for a relatively long time of 11 hours.  For the first six hours C
2
 to C
4
 olefins selectivity 
was significant, and the highest selectivity occurred during hours 3 and 4 where C
2
 to C
3
 
ratio was highest.  Then afterwards olefins production declined after the fourth hour to 
the ninth hour where it remained steady at around 5% selectivity. 
 
 47
0
10
20
30
40
50
60
70
80
90
100
0123456789101
Time on Stream, hr
Mo
l %
Ethylene
Propylene
C2-C4 olefins
MeOH
DME
Methane
 
Figure  4.9.  Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and DME, over SAPO-44  
                     (P-6), 400 
o
C, (No Grinding). 
0
10
20
30
40
50
60
70
80
90
100
0123456789101
Time on Stream, hr
Mol
 %
Ethylene
Propylene
C2-C4 olefins
MeOH
DME
Methane
 
Figure  4.10.  Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and DME SAPO-44 (P-6), 400 
o
C,  
                        After 5 min. Grinding. 
 
 48
 DME and MeOH breakthroughs did not commence until the fourth hour, then 
increased rapidly with each passing hour.  Unlike the previous run (no grinding), here 
DME constitutes a major component in the product stream as both olefins and paraffins 
amounts abated.  DME to MeOH ratio is nearly two.  Methane presence was well below 
10% for the first four hours and decreased thereafter.  
 Figure 4.11 depicts the selectivity profile with catalyst particles ground for 10 
minutes.  During the first three hours C
2
 to C
4
 selectivity was a little above 70% (Table 
4.1).  Again the C
2
 to C
3
 ratio was slightly above unity for a long time until hour 9 when 
the ratio became exactly one.  MeOH and DME breakthrough started right after the third 
hour accompanying a decline of C
2
 to C
4
 output and rapidly decreasing until hour nine.  
Methane selectivity remained relatively low throughout the course of the reaction, with 
minor fluctuation between hours 3 to 9.  As in the previous run (5 min grinding), DME 
became the major component in the product stream along with MeOH as the catalyst 
undergoes deactivation.  From the third hour MeOH began rising gently and continued 
increasing steadily until hour eight when it jumped from 20% to 25% and remained there 
until the end of the reaction. 
 
 49
0
10
20
30
40
50
60
70
80
90
100
0123456789101
Time on Stream, hr
Mo
l %
Ethylene
Propylene
C2-C4 olefins
MeOH
DME
Methane
 
Figure  4.11.   Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and DME SAPO-44  
                        (P-6), 400 
o
C, After 10 min. Grinding. 
 
 
Table  4.1.  Product Distribution over SAPO-44 (P-6), After 10 min. Grinding. 
 
COMPONENT
TOS(hr) 1
st
2
nd
3
rd
4
th
5
th
6
th
7
th
8
th
9
th
10
th
11
th
C
1
_
7.44 7.23 8.56 6.47 6.72 5.84 5.28 2.85 4.01 4.78 3.07
C
2
_
1.98 1.98 1.81 1.79 1.73 1.59 1.29 0.80 0.74 0.79 0.62
C
2
= 37.26 39.63 40.72 37.04 35.62 32.91 25.49 19.07 6.49 3.40 2.59
C
3
_
8.90 8.16 7.49 6.34 5.91 4.98 4.26 2.61 3.01 2.99 2.85
C
3
= 30.15 29.51 28.51 24.63 22.46 20.11 15.49 11.05 4.94 3.22 2.72
C
4
_
6.49 5.79 5.71 4.66 4.05 3.50 2.62 1.78 0.90 0.65 0.55
C
4
= 2.65 2.53 2.49 2.07 1.88 1.62 1.26 0.79 0.70 0.62 0.52
1.10 0.81 0.70 0.67 0.62 0.60 0.49 0.30 0.33 0.00 0.00
C
5
_
2.25 2.26 2.30 2.05 1.82 1.87 1.50 0.90 0.82 0.81 0.66
C
5
= 0.69 1.18 1.17 1.12 1.02 0.95 0.82 0.24 0.29 0.00 0.00
C
6
_
0.00 0.00 0.00 0.00 0.00 0.59 0.50 0.00 0.00 0.00 0.00
C
6
= 1.10 0.93 0.54 0.86 0.82 0.83 0.70 0.44 0.00 0.00 0.00
DME 0.00 0.00 0.00 4.87 7.86 13.52 24.96 37.81 50.87 54.57 56.73
MeOH 0.00 0.00 0.00 7.45 9.51 11.07 15.33 21.37 26.91 28.17 29.70
  
 
 
 
 50
Figure 4.12 was by far the best outcome for the product profile for SAPO-44. 
This experiment used particles ground for 15 minutes with the catalyst particle size being 
the smallest (Appendix B, Figure B-5).  In the second hour when C
2
 to C
4 
selectivity 
reached its highest peak at 82% (Table 4.2) and olefin production remained relatively 
high well above 70%.  From the first hour to the eight hour, C
2
 to C
3
 ratio slowly 
increases with each passing hour.  All other products remained relatively low, below 5%, 
for the first six hours.  DME and MeOH breakthroughs started early (3
rd
 and 4
th
 hour, 
respectively) ? and remained steady at a 5% level until the 6
th
 hour and C
2
 to C
4
 outputs 
did not deviate much.  At the 6
th
  hour olefin production began to decline accompanying 
increases in MeOH and DME production.  Here, DME accounts for much of the product 
and reaches its highest amount at the 11
th
  hour.  At the same time, the DME to MeOH 
ratio increased rapidly with time from one at the sixth to more than two and a quarter at 
the end point of the reaction.  
 51
0
10
20
30
40
50
60
70
80
90
100
0123456789101
Time on Stream, hr
Mol
 %
Ethylene
Propylene
C2-C4 olefins
MeOH
DME
Methane
 
Figure  4.12.   Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and DME SAPO-44 (P-6),  
                        400 
o
C, After 15 min. Grinding. 
 
 
Table  4.2.  Product Distribution over SAPO-44 (P-6), After 15 min. Grinding. 
 
COMPONENT
TOS(hr) 1
st
2
nd
3
rd
4
th
5
th
6
th
7
th
8
th
9
th
10
th
11
th
C
1
_
4.00 3.85 3.75 3.67 3.75 4.20 3.23 3.59 2.23 1.69 1.38
C
2
_
1.48 1.72 1.67 1.67 1.60 1.74 1.56 1.17 0.65 0.42 0.34
C
2
= 40.64 43.77 43.43 43.99 44.57 44.62 41.49 33.20 15.46 4.59 2.57
C
3
_
7.34 6.30 5.55 4.82 4.44 4.36 3.47 2.90 1.84 1.27 1.13
C
3
= 32.50 31.82 29.33 27.94 26.97 26.57 23.69 19.37 9.59 2.96 1.88
C
4
_
6.92 2.95 5.86 5.36 4.98 4.78 3.92 2.98 1.42 0.52 0.33
C
4
= 2.44 2.38 2.19 2.01 1.86 1.75 1.48 1.13 0.63 0.34 0.26
1.01 4.07 0.65 0.52 0.48 0.47 0.39 0.37 0.21 0.13 0.00
C
5
_
2.07 1.88 0.26 0.69 1.10 0.49 0.23 0.51 0.00 0.00 0.00
C
5
= 0.49 0.64 2.11 2.09 2.05 1.96 1.72 1.42 0.65 0.43 0.22
C
6
_
0.81 0.34 0.00 0.00 0.00 0.00 0.30 0.00 0.00 0.00 0.00
C
6
= 0.28 0.27 0.52 0.00 0.49 0.23 0.24 0.41 0.00 0.00 0.00
DME 0.00 0.00 4.68 3.68 3.58 4.61 10.98 21.40 42.86 61.41 65.05
MeOH 0.00 0.00 0.00 3.55 4.12 4.22 7.32 11.55 24.48 26.24 26.84
 
 
 
 
 
 
 52
 Adekkanattu, (2003) in his final report conducted a similar reaction over SAPO-
44.  His findings when compared to what is reported here (Figure 4.9, no grinding),  
showed some differences.  In his report, the catalyst remained active for the first four 
hours with high olefin C
2
 to C
4
 production, above 80%, with the highest point reached at 
87%.  Unlike the case here where catalyst showed deactivation after the 2
nd
 hour, in 
Adekkanattu?s case the catalyst remained active for nearly twice that time.  In addition 
selectivity remained considerably higher during that time. 
 Figure 4.13 provides an overall assessment of grinding effects on catalyst activity 
and product yield.  It is obvious from the graphical representation that the catalyst 
maintained a longer activity with longer grinding time coupled with more olefins C
2
 to C
4
 
selectivity. With no grinding, the catalyst deactivated rather quickly.   
0
10
20
30
40
50
60
70
80
90
100
0123456789101
Time On Stream, hr
Mol
 %
GT =  0 min
GT =  5 min
GT = 10 min
GT = 15 min
 
Figure  4.13.   Effect of Grinding Time on Product Distribution. (GT = Grinding Time). 
 
 
 
Catalyst = SAPO-44 (P-6)
WHSV   = 0.5 hr
-1
 
Temp     = 400 
o
C 
 53
Catalytic Reactions (SAPO-34), (P-5)  
 
 Figure 4.14 provides the profile for product selectivity over SAPO-34 (no 
grinding).  Catalyst remained active for almost four hours.  For the first two hours olefins 
C
2
 -- C
4
 selectivity reached their peak at nearly 75% while C
2
 to C
3
 ratio remained a little 
above unity.  DME and MeOH breakthroughs didn?t become noticeable until after the 
second hour and accompanied a rather sharp decline in C
2
 to C
4 
outputs, which decreased 
to nearly zero by the fourth hour.  DME selectivity was relatively low from a high of 17% 
at the 3
rd
 hour while decreasing to 15% and remained at that level through the end of the 
reaction.  The DME profile ran counter to that was reported by Adekkanattu from his 
experiment where DME was the main product constituent once deactivation commenced 
(Adekkanattu, 2003).  By the 4
th
 hour MeOH selectivity was at its highest at 88%.   
0
10
20
30
40
50
60
70
80
90
100
0123456789101
Time on Stream, hr
Mo
l %
Ethylene
Propylene
C2-C4 olefins
MeOH
DME
Methane
 
Figure  4.14.  Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and DME SAPO-34(P-5),  
                       400
o
C, No Grinding. 
 
 54
 Particles ground for 5 minutes showed improvements both in terms of activity and 
product distribution (Figure 4.15).  Both DME and MeOH breakthroughs commenced at 
the 2
nd
  and 3
rd
  hours, respectively.  The catalyst remained active a little less than six 
hours.  As in the previous cases C
2
 to C
3
 ratio remained at above unity with the highest 
value attained at the 3
rd
  hour.  As expected both DME and MeOH constitute the main 
product constituents through the remainder of the reaction with DME to MeOH ratio 
above 1.5.  Methane selectivity was small, ranging from around 5%, to about 0 by the 6
th
  
hour. 
0
10
20
30
40
50
60
70
80
90
100
0123456789101
Time on Stream, hr
Mol
 %
Ethylene
Propylene
C2-C4 olefins
MeOH
DME
Methane
 
Figure  4.15.  Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and DME SAPO-34 (P-5),  
                       400 
o
C, After 5 min. Grinding. 
 
 Figure 4.16 shows SAPO-34 activity over catalyst ground for 10 min.  Very early 
both DME and MeOH broke away and rapidly increased to their highest levels.  C
2
 to C
4
 
selectivity remained high for the first couple of hours, then began to decline fairly 
 55
steadily and rapidly decreased from the 5
th
  hour to the 7
th
  hour.  Although coke 
formation occurred early and rapidly increased with time, the catalyst did however 
remain active for seven hours.  C
2
 to C
3
 ratio remained above unity until the 7
th
 hour.  As 
in almost all of the other reactions over ground particles, DME remained as the main 
constituent in the product stream, where DME to MeOH ratio remains around 2.0. 
 
 
0
10
20
30
40
50
60
70
80
90
100
0123456789101
Time on Stream, hr
Mo
l %
Ethylene
Propylene
C2-C4 olefins
MeOH
DME
Methane
 
Figure  4.16.  Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and DME SAPO-34(P-5),  
                       400
o
C, After 10 min. Grinding. 
 
 Figure 4.17 shows the product selectivity profile after 15 min. catalyst grinding 
time.  Coke formation occurred fairly early, but the catalyst remained active for nearly 
ten hours.  Deactivation began soon after the first hour.  Both DME and MeOH started 
along the same path and crisscrossed one another up to the seventh hour where they each 
 56
settled on their individual path.  DME selectivity was rather significant, slightly above 
60% and nearly double the amount of MeOH present. 
 
0
10
20
30
40
50
60
70
80
90
100
0123456789101
Time on Stream, hr
Mol
 %
Ethylene
Propylene
C2-C4 olefins
MeOH
DME
Methane
 
Figure  4.17.  Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and DME SAPO-34(P-5),  
                       400 
o
C, After 15 min. Grinding. 
 
 Figure 4.18 shows the general particle size effect on C
2
 -- C
4
 selectivity.  Just as 
in the case of SAPO-44, each increase in grinding time accompanies an increase in C
2
 -- 
C
4
 selectivity coupled with a further increase in catalyst lifetime.  However, unlike 
SAPO-44, SAPO-34 showed a great tendency for deactivation even after the 1
st
 hour.  
SAPO-44 showed a great resistance to deactivation up after the 3
rd
 hour.  But in both 
cases effects of grinding on olefin distribution was significant. 
 
 57
0
10
20
30
40
50
60
70
80
90
100
0123456789101
Time On Stream, hr
Mo
l %
GT =  0 min
GT =  5 min
GT = 10 min
GT = 15 min
 
Figure  4.18.  Effect of Grinding Time on Product Distribution.  (GT = Grinding Time) 
 
 
 
SAPO-47, (P-31) 
 
 As reported earlier SEM analysis for SAPO-47 showed a wide particle size 
distribution with an elongated cubic morphology (Appendix B, Figures B-6 ? B-8), 
therefore, particles were separated in two fractions by water settling: a finer fraction and 
a coarser fraction.  Catalyst testing over the coarse fraction showed very little activity. 
Even when the coarse particles were ground, no significant olefin production occurred 
and the entire product was DME and MeOH (Figures 4.19 and 4.20).  As reported in the 
literature, a spent catalyst can be regenerated by thermal treatment.  Here however, the 
sample was recalcined for over 15 hours at 560 
o
C, and even then very little activity 
occurred when tested.   
 
Catalyst = SAPO-34 (P-5)
WHSV   = 0.5 hr
-1
 
Temp     = 400 
o
C 
 58
0
10
20
30
40
50
60
70
80
90
100
0123456789101
Time on Stream, hr
Mol
 %
Ethylene
Propylene
C2-C4 olefins
MeOH
DME
Methane
 
Figure  4.19.  Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and DME over spent 
                       SAPO-47 (P-31), 400 
o
C, Coarser Particles, After 15 min. Grinding. 
0
10
20
30
40
50
60
70
80
90
100
C1 C2 C3
1 hr    C
4
C5+
DME
MeOH
C1 C2 C3
2 hr    C
4
C5+
DME
MeOH
C1 C2 C3
3 hr    C
4
C5+
DME
MeOH
C1 C2 C3
4 hr    C
4
C5+
DME
MeOH
C1 C2 C3
5 hr    C
4
C5+
DME
MeOH
Mol
 %
Olefin Paraffin C5+ DME MeOH
 
Figure  4.20.  Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and DME over spent 
                       SAPO-47 (P-31), 400
o
C, Coarser Particles, After 15 min. Grinding. 
 
 59
 Figure 4.21 shows product selectivity profile over the finer size particle fractions.  
Although the catalyst remained active for a little more than 4 hours, deactivation occurred 
very early on.  Methanol conversion decreased rather rapidly as reaction proceeded.  C
2
 
to C
4
 selectivity achieved its highest point at the first hour, and then declined 
precipitously.  C
2
 to C
3
 ratio was fairly constant at little above unity.  DME and MeOH 
were the main product components after the third hour and remained as such until the end 
of the reaction.  A similar reaction of SAPO-47 was reported by Adekkanattu (2003), 
however, direct comparison could not be made here due to different reaction conditions 
(i.e. particle size effects).    
0
10
20
30
40
50
60
70
80
90
100
0123456789101
Time on Stream, hr
Mol
 %
Ethylene
Propylene
C2-C4 olefins
MeOH
DME
Methane
 
Figure  4.21.  Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and DME SAPO-47(P-31),   
                       400 
o
C, Finer Particles, No Grinding. 
 
 
 Figures 4.22 depict profiles of product selectivity over finer size particles ground 
for 15 minutes.  Compared with Figure 4.21 improvements in catalyst activity and 
 60
lifetime are obvious. Similarly, olefin distributions remained fairly significant over the 
course of the reaction coupled with increased MeOH conversion (Figure 4.23).  The 
DME to MeOH ratio is about 2.0. 
 We see the same tendency for rapid coke formation for SAPO-47 just like that 
found for SAPO-34 even when particles were ground.  In Adekkanattu?s finding MeOH 
conversion was fairly high at 100% for the first four hours and then began to decrease 
rather quickly thereafter.  
 
0
10
20
30
40
50
60
70
80
90
100
0123456789101
Time on Stream, hr
Mol
 %
Ethylene
Propylene
C2-C4 olefins
MeOH
DME
Methane
 
Figure  4.22.  Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and DME SAPO-47(P-31),  
                       400 
o
C, Finer Particles, After 15 min Grinding. 
 
 61
0
10
20
30
40
50
60
70
80
90
100
0.0E+00 5.0E-03 1.0E-02 1.5E-02 2.0E-02 2.5E-02 3.0E-02
Amount of Methanol Converted, mol
Percent Methanol Conversion
GT =   0 min.
GT = 15 min.
 
Figure  4.23.  Methanol Conversion Profile over SAPO-47 (P-31), 400
o
C, Finer Particles, Before and   
                       After Grinding. 
 
 
 
SAPO-56  
 
 SAPO-56 being a novel catalyst with structure analogous to the AFX type 
remained as one catalyst about which the least information was available.  Here, we look 
at SAPO-56 with three silicon contents embedded within its framework: (0.3 Si), (0.6 Si), 
and (0.9 Si) 
 
 
SAPO-56 (P-18), (0.6 Si) 
  
 Figures 4.24 and 4.25 depict profiles for product selectivity and distribution over 
SAPO-56 with (0.6 Si) content.  During the first couple of hours C
2
 to C
4
 selectivity was 
its highest being above 70%.  During that period both DME and MeOH remained 
 62
essentially flat for the first 3 hours, then started their ascent and reached their maximum 
at the 8
th
 hour where selectivities leveled off at 69% and 28%, respectively.  What is 
significant in this profile is the DME to MeOH ratio at around 2.5 indicating a sizable 
portion of MeOH is being converted to DME.  Results for this experiment did not match 
Adekkanattu?s findings (Adekkanattu, 2003).  In his experiment C
2 
to C
4
 outputs 
remained fairly stable for the first 9 hours before coke formation occurred.  Methane 
levels were rather high, however.  Like the findings here, DME and MeOH in his 
experiment became increasingly dominant once catalyst deactivation began. 
0
10
20
30
40
50
60
70
80
90
100
0123456789101
Time on Stream, hr
Mol
 %
Ethylene
Propylene
C2-C4 olefins
MeOH
DME
Methane
 
Figure  4.24.  Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and DME SAPO-56(P-18),   
                       (0.6 Si), 400 
o
C, No Grinding. 
 63
0
10
20
30
40
50
60
70
80
90
100
C1
1 hr
    C4
MeOH
C1
2 hr
    C4
MeOH
C1
3 hr
    C4
MeOH
C1
4 hr
    C4
MeOH
C1
5 hr
    C4
MeOH
C1
6 hr
    C4
MeOH
C1
7 hr
    C4
MeOH
C1
8 hr
    C4
MeOH
C1
9 hr
    C4
MeOH
C1
1
0
 hr
   C
4
MeOH
Mol
 %
Olefin Paraffin C5+ DME MeOH
 
Figure  4.25.  Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and DME SAPO-56(P-18),   
                       (0.6Si), 400 
o
C, No Grinding. 
 
 Figures 4.26 and 4.27 show profiles for catalytic activity and product distribution 
over ground particles (15 min.).  Coke formation was not significant for the first 5 hours, 
and olefin selectivity remained extremely high and steady for first 6 hours.  Altogether, 
C
2
 to C
4
 olefins account for about 65% to 74% of the total product during that period.  
Methane on the other hand remained below 20% and faded away after the 8
th
 hour.  
Activity did not improve, however.  In fact the catalyst maintained the same lifetime (8 
hours) both before and after grinding.  By the end of the reaction DME selectivity nearly 
quadrupled MeOH?s. 
 64
0
10
20
30
40
50
60
70
80
90
100
0123456789101
Time on Stream, hr
Mo
l %
Ethylene
Propylene
C2-C4 olefins
MeOH
DME
Methane
 
Figure  4.26.  Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and DME, SAPO-56  
                       (P-18), (0.6Si), 400 
o
C, After 15 min Grinding. 
0
10
20
30
40
50
60
70
80
90
100
C1
2
 
hr
    C4
MeO
H
C1
3
 
hr
    C4
MeO
H
C1
4
 
hr
    C4
MeO
H
C1
5
 
hr
    C4
MeO
H
C1
6
 
hr
    C4
MeO
H
C1
7
 
hr
    C4
MeO
H
C1
8
 
hr
    C4
MeO
H
C1
9
 
hr
    C4
MeO
H
Mol
 %
Olefin Paraffin C5+ DME MeOH
 
Figure  4.27.  Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and DME SAPO-56(P-18),  
                       (0.6Si), 400 
o
C, After 15 min Grinding. 
 65
SAPO-56 (P-28), (0.3 Si) 
 
 Figure 4.28 depicts the profile of product selectivity over SAPO-56 with 0.3 Si 
silicon content.  Product selectivity appears fairly stable during the first four hours.  
Although MeOH conversion was below 100%, coke formation remained fairly low 
during that period.  Both ethylene and propylene production remained at moderate levels 
with C
2
 to C
3
 ratio a little above unity.  Total olefin production reached its maximum at 
61% after 3 hours on stream (Table 4.3).  After the 4
th
  hour, C
2 
to C
4
 olefins outputs 
declined rapidly to below 5% selectivity, while DME and MeOH selectivities increased 
significantly to levels above 62% and 64%, respectively.    
Despite the catalyst?s strong performance during the active period, this result did 
not match Adekkanattu?s findings (Adekkanattu, 2003).  In fact, his result showed 
catalyst activity remaining for almost 10 hours. 
 
Table  4.3.   Product Distribution over SAPO-56 (P-28), No Grinding. 
COMPONENT
TOS(hr) 1
st
2
nd
3
rd
4
th
5
th
6
th
C
1
_
10.03 12.55 13.77 13.02 3.19 2.99
C
2
_
1.51 1.69 1.72 1.53 0.46 0.57
C
2
= 31.58 32.82 33.61 30.57 3.10 0.70
C
3
_
10.25 8.55 8.21 6.79 1.35 0.79
C
3
= 25.96 24.86 24.78 22.43 2.43 0.84
C
4
_
5.87 5.34 5.21 4.56 0.48 0.24
C
4
= 2.22 1.99 1.92 1.68 0.36 0.00
1.44 1.09 1.03 0.91 0.16 0.00
C
5
_
2.41 2.21 2.41 2.17 0.44 0.00
C
5
= 1.24 0.78 0.85 0.84 0.00 0.00
C
6
_
1.01 1.47 1.55 1.59 0.00 0.00
C
6
= 0.34 0.00 0.00 0.00 0.00 0.00
DME 0.00 0.81 0.00 6.09 62.48 66.71
MeOH 6.14 5.83 4.95 7.82 25.54 27.17
 
 66
0
10
20
30
40
50
60
70
80
90
100
0123456789101
Time on Stream, hr
Mol
 %
Ethylene
Propylene
C2-C4 olefins
MeOH
DME
Methane
 
Figure  4.28.  Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and DME SAPO-56(P-28),  
                       (0.3Si), 400 
o
C, No Grinding. 
 
 When the same catalyst was ground for 15 minutes ? as shown in Figure 4.29 and 
Table 4.4 ? catalyst yield abated somewhat to levels below those obtained before 
grinding.  C
2 
to C
4
 outputs declined sharply, accompanied by increases in DME and 
MeOH outputs.  Only methane remained fairly stable during the first 5 hours, and then 
decreased after that.  The catalyst did, however, last for an extra hour (6 hours total).  As 
in all the previous catalyst runs, DME constituted the main component in the product 
stream from the 5
th
 hour onward. 
 
 
 
 
 
 
 
 
 
 67
Table  4.4   Product Distribution over SAPO-56 (P-28), After 15 min. Grinding 
 
COMPONENT
TOS(hr) 1
st
2
nd
3
rd
4
th
5
th
6
th
7
th
C
1
_
10.91 11.77 9.14 8.97 4.96 2.32 2.42
C
2
_
1.40 1.39 0.97 0.95 0.56 0.50 0.00
C
2
= 30.81 28.06 19.42 17.73 8.04 0.74 0.61
C
3
_
8.68 7.10 6.01 3.94 2.12 0.82 0.00
C
3
= 25.31 21.65 15.72 13.59 6.49 0.89 0.89
C
4
_
5.59 4.57 3.43 2.67 1.22 0.00 0.00
C
4
= 1.99 1.66 1.59 1.04 0.56 0.00 0.00
1.27 0.96 0.88 0.53 0.26 0.00 0.00
C
5
_
2.22 1.88 1.98 1.38 0.71 0.00 0.00
C
5
= 0.82 0.70 1.11 0.54 0.19 0.00 0.00
C
6
_
1.00 1.41 1.66 0.98 0.71 0.00 0.00
C
6
= 0.31 0.00 0.52 0.00 0.00 0.00 0.00
DME 3.17 9.28 19.29 27.62 48.16 66.63 67.85
MeOH 6.53 9.59 18.28 20.05 26.02 28.10 28.23
 
 
 
0
10
20
30
40
50
60
70
80
90
100
0123456789101
Time on Stream, hr
Mo
l %
Ethylene
Propylene
C2-C4 olefins
MeOH
DME
Methane
 
Figure  4.29.  Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and DME SAPO-56(P-28),  
                       (0.3Si), 400
o
C, After 15 min. Grinding. 
 
 
 
 
 
 68
SAPO-56 (P-29), (0.9 Si) 
 
 Figure 4.30 shows the product selectivity profile for SAPO-56 with (0.9 Si) 
silicon content.  This catalyst, with the highest silicon content present in its framework, 
turned out to be the poorest performing catalyst among the SAPO-56 types tested.  
Reaction remained ongoing for about 4 hours total, but by the third hour, all catalyst 
activity ceased.  By the second hour C
2 
to C
4
 outputs equaled MeOH output.  In the first 
hour C
2 
to C
4
 selectivity appeared below 60% and decreased precipitously afterwards to 
essentially zero by the third hour.  Both methane and DME formations remained fairly 
low.   MeOH selectivity was significant near the end of the reaction at about 83% (Table 
4.5). 
Table  4.5.  Product Distribution over SAPO-56 (P-29), No Grinding 
               
COMPONENT
TOS(hr)           1
st
2
nd
3
rd
4
th
C
1
_
10.68 7.51 1.83 1.58
C
2
_
2.23 1.48 0.70 0.52
C
2
= 28.15 17.64 0.56 0.41
C
3
_
16.38 9.39 1.22 0.74
C
3
= 21.71 12.98 0.87 0.00
C
4
_
4.54 3.03 0.18 0.00
C
4
= 2.02 1.08 0.00 0.00
2.13 1.10 0.00 0.00
C
5
_
2.29 1.90 0.00 0.00
C
5
= 1.01 0.64 0.00 0.00
C
6
_
1.06 0.74 0.00 0.00
C
6
= 0.00 0.27 0.00 0.00
DME 0.00 8.78 12.25 9.15
MeOH 7.79 33.46 82.39 87.60
 
 
 
 
 69
0
10
20
30
40
50
60
70
80
90
100
0123456789101
Time on Stream, hr
Mol
 %
Ethylene
Propylene
C2-C4 olefins
MeOH
DME
Methane
 
Figure  4.30.  Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and DME SAPO-56(P-29),  
                       (0.9Si), 400 
o
C, No Grinding. 
 
When same catalyst was ground for 15 minutes (Figure 4.31), both activity and 
selectivity increased with MeOH remaining at moderately low levels. There was a sharp 
increase in C
2 
to C
4
 selectivity with ethylene to propylene ratio maintained at above 1.0.  
Methane formation was fairly stable for the first 3 hours at roughly 11% before declining 
to nearly 0 (Table 4.6).  DME became dominant after the 4
th
 hour.  From the 2
nd
 hour 
MeOH selectivity increased at a constant slope to a maximum 28% in product selectivity.   
 Although SAPO-56 (0.6 Si) was more active and lasted longer for time on stream, 
but results for SAPO-56 (0.9 Si) indicate greater improvement after grinding when 
compared with those of SAPO-56 (0.3 Si) and (0.6 Si).  One reason for the behavior of 
SAPO-56 (0.9 Si) may be that the particles are larger (thicker) than the other SAPO-56 as 
 70
revealed from the SEM micrographs (See Figures B-10 to B12).  Thus, they may be less 
active originally but show more improvement after grinding as found here. 
Table  4.6.  Product Distribution over SAPO-56 (P-29), After 15 min Grinding 
          
COMPONENT
TOS(hr)           1
st
2
nd
3
rd
4    
th
6    
th
C
1
_
10.91 11.77 9.14 8.97 4.96
C
2
_
1.40 1.39 0.97 0.95 0.56
C
2
= 30.81 28.06 19.42 17.73 8.04
C
3
_
8.68 7.10 6.01 3.94 2.12
C
3
= 25.31 21.65 15.72 13.59 6.49
C
4
_
5.59 4.57 3.43 2.67 1.22
C
4
= 1.99 1.66 1.59 1.04 0.56
1.27 0.96 0.88 0.53 0.26
C
5
_
2.22 1.88 1.98 1.38 0.71
C
5
= 0.82 0.70 1.11 0.54 0.19
C
6
_
1.00 1.41 1.66 0.98 0.71
C
6
= 0.31 0.00 0.52 0.00 0.00
DME 3.17 9.28 19.29 27.62 48.16
MeOH 6.53 9.59 18.28 20.05 26.02
1
4
1
2
 
0
10
20
30
40
50
60
70
80
90
100
0123456789101
Time on Stream, hr
Mo
l %
Ethylene
Propylene
C2-C4 olefins
MeOH
DME
Methane
 
Figure  4.31.  Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and DME SAPO-56(P-29),  
                       (0.9Si), 400
o
C, After 15 min. Grinding. 
 71
 
Effect of Silicon Content 
 
 While introduction of silicon atoms into the framework of aluminophosphate 
molecular sieves enable them to exhibit Br?nsted acidity, thereby facilitating their use as 
acid catalysts, the effect of the silicon content on SAPO-56 is being examined here.   
Figures 4.32 and 4.33 depict profiles of the olefins selectivity over these catalysts before 
and after grinding, respectively.  When silicon content is increased from 0.3 to 0.6, an 
increase in olefins selectivity was observed.  However, increasing the silicon content 
further to 0.9 showed a reverse in olefins selectivity.  This finding indicates that too much 
silicon content inside the framework posed a detrimental effect on the catalyst?s overall 
effectiveness.  Again after grinding, a slight improvement was apparent for catalysts with 
0.6 and 0.9 silicon content.  
0
10
20
30
40
50
60
70
80
90
100
0123456789101
Time On Stream, hr
C
2
-C
4
 Olefins Selectivity, (Mol %)
0.3 Si
0.6 Si
0.9 Si
 
Figure  4.32.  Effect of Silicon Content on Olefins Selectivity over SAPO-56, No Grinding. 
 
 72
0
10
20
30
40
50
60
70
80
90
100
0123456789101
Time On Stream, hr
C
2
-C
4
 O
l
efins Selectivity, (Mol %)
0.3 Si
0.6 Si
0.9 Si
 
Figure  4.33.  Effect of Silicon Content on Olefins Selectivity over SAPO-56, After 15 min. Grinding 
 
 
SAPO-56 (P-18), (0.6 Si) Spent Catalyst 
  
It is well known and noted in the literature that spent catalysts can be regenerated 
when thermally treated.  Here, however, we tried a different approach by grinding the 
spent catalyst.   Bear in mind this catalyst is the same one tested in Figure 4.24 and was 
ground for approximately 15 min. before testing in the new experiment (Figure 4.34).  
In this new experiment, little activity was observed.  Nearly all components with 
the exception of DME and MeOH remained near 0.  From this figure it looks as though 
DME and MeOH selectivities mirrored one another over the course of the reaction.  Since 
not much activity was apparent for the initial 4 hours, the experiment was eventually 
terminated.  It thus appears that particle size reduction alone, i.e. grinding, is not effective 
 73
in restoration of catalyst activity, indicating that the deactivation occurs throughout the 
particles, not just around the outer edges. 
0
10
20
30
40
50
60
70
80
90
100
0123456789101
Time on Stream, hr
Mo
l %
Ethylene
Propylene
C2-C4 olefins
MeOH
DME
Methane
 
Figure  4.34.  Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and DME SAPO-56, 
                       (P-18), (0.6Si), 400
o
C, Spent Catalyst Ground for 15 min.  
 
 
 
SAPO Incorporated with Ruthenium 
 
 In this section findings based on SAPOs incorporated with ruthenium are reported 
and discussed.  Samples treated with Ru include: SAPO-34, SAPO-44, and SAPO-56 (0.6 
Si).  The incorporation process was performed in Dr. Richard Ernst?s lab in the 
University of Utah Chemistry Department.   
 
 
Ru-SAPO-34 (Ru-P-5) 
 
 The product distribution over Ru incorporated SAPO-34 was not improved as is 
shown in Figure 4.35.  Compared with Figure 4.14 for unmodified SAPO-34, the Ru 
 74
catalyst performed poorly.  While SAPO-34 remained active for nearly 4 hours with C
2
 to 
C
4
 selectivity relatively high during the first 3 hours, Ru impregnated SAPO-34 only 
lasted for 3 hours.  Both ethylene and propylene levels were very low compared to 
unmodified SAPO-34.  MeOH conversion was also very low.  After the second hour, the 
product consisted mainly of MeOH indicating very poor activity.  MeOH to DME ratio 
was high, between 3.5 to 4. 
0
10
20
30
40
50
60
70
80
90
100
0123456789101
Time on Stream, hr
Mol
 %
Ethylene
Propylene
C2-C4 olefins
MeOH
DME
Methane
 
Figure  4.35.  Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and DME over Ru  
                        impregnated SAPO-34 (Ru-P-5), 400 
o
C. 
 
 
 
Ru-SAPO-44 (Ru-P-6) 
 
 SAPO-44 modified with ruthenium (Figure 4.36) likewise did not show much 
improvement compared with the corresponding unmodified sample, with both catalysts 
remaining active for quite a while with the modified sample lasting about 2 hours longer.  
C
2
 to C
4
 selectivity profiles in both experiments were almost the same, however, with 
 75
slightly lower amounts present with the Ru modified catalyst.  In both experiments 
methane selectivity occurred around the same level, 10% and lower.  Additionally, both 
DME and MeOH exhibited almost identical profiles in these two experiments with 
MeOH amounts being almost 8 times DME.      
0
10
20
30
40
50
60
70
80
90
100
0123456789101
Time on Stream, hr
Mol
 %
Ethylene
Propylene
C2-C4 olefins
MeOH
DME
Methane
 
Figure  4.36.  Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and DME Ru  
                        impregnated SAPO-44 (Ru-P-6), 400 
o
C. 
 
 
 
Ru-SAPO-56 (Ru-P-18)  
 
 Like SAPO-34, and SAPO-44, SAPO-56 (0.6 Si) did not show much 
improvement when modified with ruthenium (Figure 4.37).  Unlike the unmodified 
sample where a gradual C
2
 ? C
4
 olefin decline was noticed early on, RuSAPO-56 
remained fairly stable early on for the first 4 hours before starting its descent.  Catalyst 
activity profiles for both samples were just about the same with the modified sample 
 76
lasting a bit longer at relatively low olefins selectivity levels. Methane amounts in both 
these cases reach their peaks at around 16 mol %.  Furthermore, DME amounts were 
present in significant amount above MeOH levels from the 6
th
 hour forward (Table 4.7). 
 In summary, three SAPO catalysts were incorporated with ruthenium and tested 
for activity.  When results from these tests were compared with corresponding tests of 
unmodified samples, no significant improvements were observed.  In fact for Ru-SAPO-
44 and Ru-SAPO-56, selectivity profiles and catalyst yield were nearly identical except 
that catalyst activity lasted about an hour longer for the Ru treated samples.  Ru-SAPO-
34, however, performed poorly and deactivated much faster as compared to the 
unmodified version.  Huang et al. (2005) in studying temperature effects over SBA-15 
modified with Ru and Pt for the dehydrogenation of cyclohexane found catalytic activity 
to be superior for Pt supported catalyst.  Improvement in catalysis performance for Ru 
modified SBA-15 was minimal.   It may very well be that metals other than Ru would 
give improved SAPO performance. 
Table  4.7.  Product Distribution over Ru-SAPO-56 (Ru-P-18) 
 
COMPONENT
TOS(hr) 1
st
2
nd
3
rd
4
th
5
th
6
th
7
th
8
th
9
th
C
1
_
10.62 15.33 15.20 15.49 13.23 11.67 6.25 4.19 4.50
C
2
_
1.66 2.13 2.02 1.91 1.59 1.38 0.78 0.69 0.84
C
2
= 26.75 33.95 31.41 31.63 27.12 22.69 5.74 1.88 1.41
C
3
_
11.46 9.96 10.55 9.86 7.72 5.84 3.28 2.37 2.12
C
3
= 23.79 27.19 25.79 25.49 21.44 18.52 4.90 2.63 2.20
C
4
_
5.23 5.55 5.57 5.54 4.47 3.67 1.00 0.53 0.20
C
4
= 2.37 1.88 2.48 2.39 1.91 1.59 0.72 0.55 0.00
1.48 1.11 1.09 1.01 0.90 0.76 0.34 0.00 0.00
C
5
_
2.68 1.84 2.90 2.91 2.56 2.16 0.93 0.50 0.00
C
5
= 0.74 0.39 0.79 1.44 1.23 1.06 0.27 0.00 0.00
C
6
_
1.74 0.37 1.57 1.75 2.12 1.41 0.00 0.00 0.00
C
6
= 0.59 0.30 0.63 0.58 0.00 1.27 0.00 0.00 0.00
DME 0.00 0.00 0.00 0.00 5.83 14.65 49.68 58.86 60.91
MeOH 10.89 0.00 0.00 0.00 9.89 13.34 26.11 27.79 27.80
 
 77
0
10
20
30
40
50
60
70
80
90
100
0123456789101
Time on Stream, hr
Mol
 %
Ethylene
Propylene
C2-C4 olefins
MeOH
DME
Methane
 
Figure  4.37.  Distribution of Ethylene, Propylene, C
2
 ? C
4
 Olefins, MeOH, and DME Ru  
                        impregnated SAPO-56 (Ru-P-18), 400 
o
C. 
 
 
 
 
 
 
 78
V. CONCLUSION 
 
 
 
 Although SAPO catalysts have been in existence for over 25 years, many efforts 
have been under way in studying them to make them more efficient.  Incorporation of 
various metals into their framework is one method often employed to achieve that.  
Process conditions have been investigated very thoroughly by various groups in order to 
systematically understand the optimum conditions in regard to product distribution, 
olefins selectivity, catalysis yield and catalytic activity.  This thesis was based on 
experiments carried out over several microporous SAPO catalysts and various process 
conditions including temperature, particle size, and catalyst modification effects were 
studied and analyzed. 
 Results from comparing the scaled-down and standard operating conditions 
revealed almost identical product selectivity profiles with negligible differences in 
catalyst lifetime and MeOH conversion.  This finding confirmed our original hypothesis 
that maintaining WHSV at the same level (0.5 hr
-1
) when reducing all operating 
conditions by the same factor would not greatly change the reaction outputs.  Results 
from the temperature study led us to believe that when catalyst particles were ground, the 
ability for catalysts to resist rapid deactivation might be improved.  Some, but not all, 
catalysts were improved by the particle size reduction.  Of the three SAPOs tested, 
SAPO-44 turned out to be better in terms catalytic performance and catalyst yield after 
grinding treatments.  However, SAPO-56 maintained the same activity level before and 
 79
after grinding treatment.  SAPO-56 (0.9 Si) gave a slight improvement.  Due to the 
effective particle size of SAPO-56 (0.3 and 0.6 Si), diffusional effects could have played 
less of an effect while for SAPO-56 (0.9 Si) the effect was more apparent as revealed 
from the catalysis performance.  SAPO-34, did not perform well in any of the categories 
studied compared to the other samples.  Further, results from this study indicated the 
optimum operating temperature condition yielding the greatest C
2
 to C
4
 ratio was 
between 400 
o
C to 450 
o
C.  This finding is in agreement with reports by Dubois et al. 
(2003) and Wu et al. (2004). 
 Various SAPOs incorporated with ruthenium based on a gas phase deposition  
method were tested for catalytic activity.  Data for these samples did not show much 
improvement for any of the categories analyzed: yield, product distribution or lifetime.  
These catalysts were incorporated with only 1% Ru loading, and it is possible an increase 
of 5% to 10% loading could quantitatively and qualitatively lead to major performance 
improvements.  In any event both SAPO-44 and SAPO-56 maintained nearly the same 
levels before and after Ru modification with slight improvements.  SAPO-34 performed 
poorly, even to the point of loosing activity as a result of the Ru treatment.  Impregnation 
with other metals such as Pd and Pt remains a possible avenue for improvement. We 
also looked at the possibility of whether a spent catalyst would show any improvement in 
activity after grinding.  Results from an experiment with SAPO-56 (0.6 Si) did not show 
any evidence of regeneration or restored activity following grinding. DME and MeOH 
were the only products present in abundant amounts in the product stream. 
 
 
 
 
 80
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Miller, S.J.; US Pat. 5 135 638, 1992. 
 
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Prakash, A., Huang, X., Dubois, D., Obrzut, D., Jyothi, T., Liu, J., Guin, J., 
?Development of Microporous Shape-Selective Catalysts for Ethylene, Propylene, and 
other Value-Added Products via C-1 Chemistry?, in C1 Chemistry for the Production of 
Ultra-Clean liquid Transportation Fuels and Hydrogen, Annual Report for October1, 
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 84
VII. APPENDICES 
 
 
 
Appendix A: Table of Zeolites and Grinder 
 
Appendix B:  SEM Micrographs 
 
Appendix C:  List of Calculations 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 85
APPENDIX A 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Zeolites and Grinder 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 86
 
 
Table of Zeolite Structures 
 
                           
AFX 
                                             
BEC                                                                                  BOG
 
 
 
                              
CAN
                                                  
CGF
                                              
CHA
 
 
 
         
DAC    
                  
AEI                                                      MEL 
 
 
Table  A-1.  Zeolite Structures 
                     ( Database of Zeolite of Zeolite Structures: International Zeolite Association (2000) ) 
      Source: ?http://topaz.ethz.ch/IZA-SC/Introduction.htm? 
 
 
 
 
 
 
 87
                      
Figure  A-2.  Wig-L-Bug from Dentsply/Rinn.   
                      On the left hand side is the actual grinder, and on the right side is the agate vial which  
                       holds the sample. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 88
 
APPENDIX B 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
SEM Micrographs 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 89
 
                        
Figure  B-1.  SAPO-34 (P-5), X1000, 10kV, 14mm 
 
 
                        
Figure  B-2.  SAPO-44 (P-6), X500, 10kV, 14mm 
 
50 ?m
13.4 ?m 
 90
                        
Figure  B-3.  SAPO-44 (P-6), After 5 min Grinding, X500, 10kv, 12mm  
                     
 
                        
 Figure  B-4.  SAPO-44 (P-6), After 10 min Grinding, X500, 10kv, 12mm 
 
10.5 ?m 
9.1 ?m 
 91
                         
Figure  B-5.  SAPO-44 (P-6), After 15min Grinding, X500, 10kV, 12mm 
 
 
                        
Figure  B-6.  SAPO-47 (P-31), X50, 10kv, 13mm 
112 ?m 
6.3 ?m 
 92
                         
Figure  B-7.  SAPO-47 (P-31), X50, 10kV, 14mm 
 
 
                         
Figure  B-8.  SAPO-47 (P-31), X50, 10kV, 14mm, (Sonicated in Acetone) 
               
  
141 ?m
  141 ?m 
 93
                         
Figure  B-9.  SAPO-47 (P-31), X200, 10kV, 13mm, (Sonicated in Acetone) 
 
 
                         
Figure  B-10.   SAPO-56 (P-28), (0.3 Si) 
 
 
14.1 ?m 
70 ?m 
 94
                         
Figure  B-11.  SAPO-56 (P-28), (0.6 Si), X200, 10kV, 12mm 
 
         
                         
Figure  B-12.  SAPO-56 (P-29), (0.9 Si), X200, 10kV, 14mm 
 
 
60 ?m 
135.8 ?m 
 95
                         
Figure  B-13.  Ru-SAPO-34 (Ru-P-5), X1000, 10kV, 14mm 
 
 
                         
Figure  B-14.  Ru-SAPO-44 (Ru-P-6), X500, 10kV, 14mm 
 
13.4 ?m 
49.4 ?m
 96
                         
Figure  B-15.  Ru-SAPO-44 (Ru-P-6), X1000, 10kV, 14mm 
 
 
                         
Figure  B-16.  Ru-SAPO-56 (Ru-P-18), X500, 10kV, 14mm 
 
 
30 ?m
52.5 ?m
 97
 
                         
Figure  B-17.  Ru-SAPO-56 , X500, 10kV, 14mm 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
52.5 ?m
 98
APPENDIX C 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
CALCULATION PROCEDURE 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 99
This section provides detailed information on calculation procedure.  Please refer 
to Standard Analysis in Experimental Section for further clarification: 
Column labeled with ?Retention Time? contains information obtained directly 
from standard calibrations. 
Column labeled with ?Standard ppm? refers to concentration of standard 
components.  Separate calculations were made in order to arrive at ppm values for DME 
and MeOH.  
Column labeled with ?Standard Area for 100?l? refers to standard values obtained 
during GC analysis. 
Column labeled ?Sample peak area 100?l?contains values reported from actual 
experiments. 
Column labeled ?ppm of sample product? contains concentration values for 
individual product components and is based on the following equation: 
     
                                                                                                                   C-1 
 
Column labeled ?% of compound? refers to percent of individual component 
present in product mixture and is calculated as follow: 
 
                                                                                                                   C-2  
Column labeled with ?mol/min of compound? refers to the mole per minute of ith 
component and is calculated as follow: 
                                                                                                                 
                                           ( ppm of compound i x outlet molar flowrate )
mol/min of compound i  =  ------------------------------------------------------------------------
                                                                         1000000
                          ( Standard ppm x Peak Area )
ppm product  =  -----------------------------------------------
                              Standard Area for 100?l
                                ( ppm of compound i x 100 )
% of compound i  =  --------------------------------------------
                                             All components
?
 100
                                                                                                                       C-3 
Column labeled with ?mol C/min? refers to the number of moles of carbons per 
component and is calculated as follow: 
                                                                                                                       C-4   
The followings are calculated as follows (Please refer to figure): 
  
                                                                                                                      C-5 
                                                                                                               
                                                                                                                      C-6 
                                                                                                                      C-7 
                                                                                                                      C-8 
  
                                                                                                                         C-9 
 
Selectivity is the mole percent of a species produced by the reaction. The selectivity of 
products is calculated as follow: 
  
                                                                                                                      C-10 
 
                                                                                                                      C-11 
The methanol conversion calculates how much of the methanol is being 
converted. The calculation goes as follow: 
 
                                                                                                                                 C-12 
                                  [( MeOH in -- MeOH products )mol x 100 ]
MeOH Conversion  =  ---------------------------------------------------------------
                                                      MeOH in (mol)
mol C / min  =  ( mol/C of compound i ) x ( # of Carbons present )
                                   ( MeOH flowrate x MeOH density )
MeOH In (mol/min)  =  ----------------------------------------------------
                                                  M.W. of MeOH
Carbon in (mol/min)  =  Methanol in (mol)
Carbon out (mol/min)  =  ( Total mol C / min ) 
Carbon balance  =  ( Carbon out -- Carbon in ) mol/min ) 
                             [( Carbon out -- Carbon in ) x 100 ]
% Loss or Gain  =  -----------------------------------------------------
                                                Carbon in
                                           ( mol of Methane x 100 )
Methane Selectivity  =  -------------------------------------------------
                                     [( Total products -- MeOH )mol ]
                                        ( mol of Propylene x 100 )
Propylene Selectivity  =  -----------------------------------------
                                            Total mol of products