Aromatic hydrocarbons production from catalyst assisted microwave pyrolysis of Douglas fir sawdust pellet
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The aims of this dissertation were to understand the effects of zeolite as a catalyst for improving biofuel quality on in-situ microwave assisted catalytic pyrolysis and ex-situ catalytic cracking close coupled to microwave assisted pyrolysis process. Douglas fir sawdust pellet (DF) was used as feedstock. The reaction conditions were optimized with central composite experimental design (CCD). GC/MS was used to analyse bio-oil chemical composition. The bio-oil from in-situ microwave assisted catalytic pyrolysis resulted in a series of important and useful chemical compounds: phenols, guaiacols, and aromatic hydrocarbons. Phenols and guaiacols were the most abundant compounds which were about 50-82 % in bio-oil depending on the pyrolysis conditions. Ex-situ catalytic cracking close coupled to microwave assisted pyrolysis process was conducted from direct catalytic cracking of DF pyrolysis vapor. The aromatic hydrocarbons were enriched and became the most abundant compounds accounting for about 15-92.6% in the bio-oils depending on the catalytic pyrolysis conditions. The aromatic hydrocarbons were mainly composed of benzene, toluene, xylene, naphthalene, and there derivatives. High cracking temperature and inverse weight hourly space velocity (WHSV) -1 favored the production of aromatic hydrocarbons. The fresh ZSM-5 catalyst has a high selectivity for aromatic hydrocarbon, and the used ZSM-5 catalyst still has a moderate selectivity for phenols. The ZSM-5 catalyst was stable during the catalytic reaction cycles.Zinc modified ZSM-5 catalysts were synthesized and tested in ex-situ catalytic cracking close coupled to microwave assisted pyrolysis process. It was found that the Zn loading on ZSM-5 catalyst could lower the coke and made the process more sensitive to the (WHSV) -1 , less sensitive to the cracking temperature than ZSM-5 catalyst.The thermal decomposition behavior and kinetics of DF pyrolysis and catalytic pyrolysis were analyzed. Adding catalysts tended to slightly lower the temperature of thermal degrading process. A first reaction model fitted for both DF pyrolysis and catalytic pyrolysis. The Py-GC/MS analysis showed that using of ZSM-5 catalyst increased the aromatic hydrocarbons and reduced the oxygenated compounds from different feedstock (DF and cellulose).