Dehydrocyclization-cracking of Soybean Oil Using Pt/NiMo Sulfide Catalysts Supported on Hierarchical ZSM-5-Al₂O₃-TiO₂-composite Prepared by Sol-gel Method

Abstract

Hierarchical ZSM-5-Al2O3-TiO2-composite supported Pt, Ni and Mo sulfides catalysts were used for the dehydrocyclization-cracking of soybean oil at 1.0 MPa of hydrogen in the range 420-580 °C. Pt/NM/Z(24)75Ti(500sg) (N=Ni, M=Mo, Z=ZSM-5, 24=SiO2/Al2O3, 75=weight ratio, Ti=TiO2, 500=cal-cination temp. °C, sg=sol-gel method) and Pt/NM/Z(24)75Ti(600sg) prepared by the sol-gel method exhibited the higher activity in this reaction and the higher aromatics yields than the catalysts with single use of Al2O3 and TiO2 prepared by the kneading method. Further, Pt/NM/Z(24)30Al30Ti prepared by the kneading method and Pt/NM/Z(24)75Al(600sg) prepared by the sol-gel method exhibited the highest aromatics yield of 15% among the catalysts tested. The result indicated that the addition of TiO2 to the composite support would promote the interaction between molybdenum sulfide and TiO2, activate hydrogen and lead to enhanced cracking of ester group of triglyceride and cyclization of hydrocarbon fragments. When the sol-gel method was used, the catalysts with not only TiO2 but also Al2O3 exhibited the higher aromatics yields. Pt/NM/Z(24)75Ti(500sg) and Pt/NM/Z(24)75Ti(600sg) inhibited the formation of gaseous products while Pt/NM/Z(24)30Al30Ti and Pt/NM/Z(24)75Al(600sg) increased gaseous products, suggesting that the mechanism of aromatics formation might be different, and that the former would produce aromatics through the direct cyclization of longer-chained hydrocarbon fragments while the latter would produce them through gasification to C2-C4 olefins and the successive cyclization by the Diels-Alder reaction of olefins.