Understanding The Effect of Catalytic Pyrolysis Bio-oil Produced Using CaO During Hydrotreatment

Abstract

Energy is very important for sustaining human life, and mankind is dependent on fossil fuels for energy need. Since fossil fuels reserves are limited and are depleting in a rapid rate, there is a surge for alternative fuel sources. Wind, solar, hydropower, and geothermal are some of the key alternative sources of energy. However, the carbon based liquid form of alternative energy can be obtained only form biomass. Biomass can be converted to liquid intermediates such as bio-oil and then upgraded it to “drop-in” and “fungible” biofuels. There are different methods for converting biomass to biofuels, and a fast pyrolysis is touted as one of the promising technologies. The fast pyrolysis is carried out at moderate temperature (400 – 600oC) in the absence of oxygen with a very short residence time to convert solid biomass into chars, condensable vapors and non-condensable gases. There are different parameters that play influential role in fast pyrolysis process such as temperature, residence time, type of biomass, heating rate and type of reactor. However, bio-oil obtained from fast pyrolysis process has high acidity, high viscosity, high oxygen content and low heating value, which make it incompatible to be used as a transport fuel. In order to improve these properties, bio-oil needs to be upgraded over catalyst(s), and hydrotreating is one the effective methods. Hydrotreating process is carried out at high pressure where hydrogen helps to remove oxygen from bio-oil in order to obtain biofuels that is comparable to fuels obtained from crude oil. Instead of conducting convectional pyrolysis followed by hydrogen treatment, catalytic fast

pyrolysis, in which biomass is reacted with catalysts during pyrolysis, is an efficient method to improve bio-oil properties. Chapter 1 gives brief introduction about the basis of study and overall research objective. Chapter 2 summarizes brief information of energy scenario, fast pyrolysis, list of parameters affecting fast pyrolysis, bio-oil properties, upgrading technique along with tribological aspect of bio-oil. Chapter 3 included comparative study of upgraded non-catalytic and catalytic bio-oils. In this study, non-catalytic (quartz sand) and catalytic (CaO) fast pyrolysis process were performed to produce two types of bio-oil from hybrid poplar biomass. Bio-oil collected from electrostatic precipitator (ESP) were upgraded in three conditions: Pt/C catalyst, ZSM-5 catalyst and control (without any catalyst). Product distribution and major biofuel properties were compared between upgraded bio-oils from both catalytic and non-catalytic fast pyrolysis process (Chapter 3). From this study, it was observed that higher liquid yields were obtained when bio-oils were upgraded over Pt/C catalyst for both non-catalytic (69.79 wt. %) and catalytic (68.67 wt. %) bio-oils. Higher heating value of original ESP bio-oil from catalytic fast pyrolysis (33.4 MJ/kg) was higher than non-catalytic (27 MJ/kg) fast pyrolysis bio-oil although there was no significant effect on upgraded catalytic bio-oils. The upgraded as well as original ESP bio-oils included higher fraction (52 - 66%) of vacuum gas oil range in both catalytic and non-catalytic. Acidic nature of original ESP oil reduced to around 53 for both catalytic and non-catalytic upgraded bio-oils. Viscosity of original ESP bio-oils was reduced from non-catalytic (98.22 cSt) to catalytic (68.07 cSt) bio-oils. Friction and wear tests were performed using original ESP bio-oils based on their viscosity values and compared with the standard base oils from Petro Canada. Friction coefficient of the original catalytic bio-oil was lower compared to standard and non-catalytic bio-oil. Wear volume results showed that catalytic original ESP bio-oil performed better than any other oils tested.