Low Temperature Oxidation of Carbon Monoxide Using Microfibrous Entrapped Catalysts for Fire Escape Mask Application

Abstract

The prime reason for life casualties in fire is not the fire itself but poisoning caused by presence of carbon monoxide. It has been reported by American Medical Association that CO causes about 2100 deaths per year and about 10000 physical injuries in United States. Carbon monoxide can be lethal at a concentration of more than 400 ppm. Depending upon cases, fire can contain as high as 3600 ppm of carbon monoxide. This dissertation presents results of R&D efforts to develop a thin, low pressure drop, high face velocity, catalyst substrate capable of meeting various CO reduction standards for Respiratory Protection Applications including CBRN (recently adapted by NIOSH), EN 403 (European Union) and ANSI / ISEA 110-2003 (ANSI).

The goals for this work were set based on performance of current commercial products in the domain and new and emerging standards for testing of fire escape masks. The current products meet well existent EN 403 standards, which corresponds to removal of 2500 ppm CO down to 200 ppm, for a flow rate of 30 LPM for minimum 15 minutes. The new and emerging standards are more stringent and pose a significant challenge for development. Also, current commercial products have been designed based on packed bed configuration of catalyst, hence suffer pressure drop. The effort here utilizes a unique approach known as Microfibrous Entrapment. Resultant materials are a composite structure wherein a micron sized powder of the catalyst (ca. 10-250 micron in diameter) is entrapped within a sinter-locked mesh of metal, polymer or ceramic fibers (ca. 2 20 micron in diameter). These materials are highly advantageous for applications where high contacting efficiency is required. The approach also provides a number of other advantages such as high thermal conductivity, low pressure drop, and high mechanical & structural stability. In this work, a promoted and proprietary Pt/Al2O3 (150 250 micron) has been entrapped into a nickel microfibrous mesh consisting of 2-3 vol% of 4 and 8 micron diameter fibers. The catalyst has been tested in a tubular reactor. Various tests were performed according to all the test protocols. Non-linear dynamics of CO oxidation, hysteresis effects, effect of moisture, kinetic oscillations phenomenon are also discussed. Analysis of commercial products was done to compare this technology with existing ones. The results show that this technology utilized 10 times lower quantity of catalyst, has a four-fold lower pressure drop and weighs ten times lighter compared to commercial products. Technology transfer has been detailed to test the scalability of the process.