Abstract: USY, HZSM-5, ANA, Al2O3, and SiO2 catalysts were used to study the effects of catalysts on the conversion of animal fat and yields of products in a fixed-bed microreactor. The results showed that the initial decomposition (mainly cleavage of theC-Obond) of animal fat proceeded through decarboxylation and decarbonylation reactions. Subsequent cracking of the resulting heavy hydrocarbons and oxygenated hydrocarbons into light molecules (such as liquefied petroleum gas and gasoline) occurred on acid sites of the catalysts. The conversion of this secondary cracking over USY and HZSM-5 zeolites was high because of their strong acid sites. However, the weak acidic Al2O3 catalyst containing large pores permitted a mild secondary cracking with a lower conversion. On the other hand, the secondary cracking was strongly inhibited on non-acidic and large pore SiO2 catalyst and non-acidic and none pore ANA zeolite. The conversion on these two catalysts was much low, and there were a lot of heavy oxygenated hydrocarbons in the liquid products. Additionally, more CO2 was produced by thermal cracking, but a relatively more CO was formed by catalytic cracking.

Key words: animal fat, zeolite, catalyst, initial decomposition, subsequent cracking, acidity