Aromatics formation by dehydrocyclization-cracking of methyl oleate using ZnZSM-5-alumina composite-supported NiMo sulfide catalysts

Abstract

In order to investigate the dehydrocyclization-cracking of methyl oleate, one of fatty acid methyl esters, ZnZSM-5-alumina composite-supported NiMo sulfide catalysts were prepared, where the contents of NiMo were changed with the content of alumina. Approximately 100% conversion was achieved for each catalyst even at 450 °C under the 0.5 MPa hydrogen pressure while the selectivity for products changed depending on temperature and the configuration of the composite catalysts. The increase in the content of alumina and the increase in the metal content brought about the increase in the hydrocracking activity. When the content of alumina ratio was low and the metal content decreased, however, the C15–C18 diesel component increased, but hydrocracking did not proceed sufficiently and the larger amount of C19- fraction tended to be formed. The yield of aromatics increased with an optimum combination of amounts of alumina-supported NiMo sulfide and Zn-exchanged ZSM-5, and 9.3NM/Zn(13)Z(24)35A catalysts gave the highest yield of 20 wt%. This catalyst generated relatively smaller amounts of gaseous products and olefins, suggesting that most of the reaction products would be gasified once and then cyclization may occur to produce aromatic compounds. The reaction of methyl oleate started on NiMo/γ-Alumina part in NiMo/ZnZSM-5/γ-Alumina and produced C17 and C18 hydrocarbon fragments through decarboxylation, decarbonylation and hydrodeoxygenation. After successive hydrocracking by NiMo/ZnZSM-5/γ-Alumina and cracking by ZnZSM-5 part, forming smaller alkanes and alkenes, finally C2-C4 olefins and gasoline fractions would be produced. It is likely that C2-C4 olefins would be subjected to selective aromatization to benzene, toluene and xylene on Zn/ZSM-5.