Title: Coke Accumulation on Catalysts used in a Fluidized Bed Pyrolyzer Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: September 23, 2010
Publication Date: September 23, 2010
Citation: Jackson, M.A., Compton, D.L., Boateng, A.A. 2010. Coke accumulation on catalysts used in a fluidized bed pyrolyzer [abstract]. TCS 2010: Symposium on Thermal and Catalytic Sciences for Biofuels and Biobased Products. p. 55. Technical Abstract: We have examined the impact of various solid catalysts on the product distribution resulting from the pyrolysis of biomass. Though catalysts do have a discernible impact, this impact is small. In our bench-top pyrolyzer designed as a catalyst screening tool, we measure bulk product distribution as solid, gas, and liquid phases as well as composition of the liquid and noncondensible gasses. These distributions are compared to those found when quartz sand is used in the reactor and the results are used as an assessment of the catalysts’ impact. The most notable result from the catalysts when compared to sand is the change in liquid phase components from highly oxygenated products to simple aromatics such as the BTEX mix. Also notable is the change in gas composition which is seen in the amount of hydrogen and carbon monoxide produced compared to carbon dioxide. However, we have noted that on subsequent runs with a catalyst sample, the product distributions appear more like those from pyrolysis over sand. The catalytic activity returns upon calcination of the catalyst. This process causes the carbonaceous material deposited on the catalysts to be burned off resulting in fresh catalyst surface. These coke deposits quickly accumulate to an extent that they poison the catalyst. Consequently, we have used Temperature Programmed Oxidation to examine the coke deposits on several catalysts including zeolites, metal exchanged zeolites, and mesoporous silica supports. Characterization of the deposits is limited to the temperature at which the carbon oxidizes with higher temperatures attributed to more organized, crystalline, or graphite-like, stable carbon. The complex traces generated by the TPO experiment can usually be deconvolved into separate peaks. The coke found on sand has three oxidation peaks centered at 535°C. The catalysts we examined have oxidation peaks ranging from 377°C on hydrotalcite to 670°C on Ca-exchanged zeolite Y. These results and our efforts to minimize coke deposition will be shown.