Role of Support in Hydrotreatment of Jatropha Oil over Sulfided NiMo Catalysts

Hydrotreatment of jatropha oil over a series of sulfided NiMo/SiO2-Al2O3 and NiMo/ZSM-5-Al2O3 catalysts in a fixed-bed reactor was carried out. Effect of support on various reactions occurring in hydrotreatment was investigated. For NiMo/SiO2-Al2O3 series catalysts, the rates of decarboxylation and/or decarbonylation increased with increasing Si/(Si+Al) ratio, while the ratio of hydrodeoxygenation decreased with increasing Si/(Si+Al) ratio. For NiMo/ZSM-5-Al2O3 series catalysts, with increasing amounts of ZSM-5, the rate of decarboxylation and/or decarbonylation versus hydrodeoxygenation did not change. These results could be attributed to the total acidic sites of catalyst having a positive effect on the decarboxylation and/or decarbonylation pathways. NiMo/SiO2-Al2O3 catalysts showed a much higher isomerization/cracking ratio than NiMo/ZSM-5-Al2O3 catalysts. It was suggested that isomerization reaction was favorable for weak and middle acidic sites but cracking reaction was favorable for strong acidic sites.