Hydroprocessing of biomass feedstock over sulfided CoMo-, NiMo-, and NiW-supported catalysts for bio-jet fuel component production: a review

Abstract

Recently, bio-jet fuels have attracted significant attention as a prospective additive to conventional aviation fuels since this is the most promising strategy to reduce CO₂ emissions in the aviation sector in the future. Bio-jet fuels can be produced via the hydroprocessing of vegetable oils containing long-chain triglycerides. This study presents a review of the recent literature on the catalytic properties of sulfided CoMo-, NiMo- and NiW-supported materials in the hydroprocessing of oils under different reaction conditions. The comparison of CoMo and NiMo/Al₂O₃ catalysts showed that CoMo catalysts can produce jet fuel hydrocarbons C₈–C₁₆ with low yields of 5.0–17.5%, which are insufficient for commercial use. Alternatively, the use of NiMo/Al₂O₃ catalysts increased the yields of jet fuel achieved via hydroprocessing a mixture of vegetable oils with gas oil/kerosene or hydroprocessing vegetable oil with a high content of C₁₀–C₁₄ fatty acids. In addition, the modification of zeolites (ZSM-5, USY) promoted the formation of suitable mesoporosity and acidity in support for the inhibition of deep cracking of C₉–C₁₈ hydrocarbons, resulting in high yields of bio-jet components in the range of 30–75%. The i/n ratio was more than 2.0, which promoted the formation of bio-jet fuel with a low freezing point, meeting the regulation of ASTM standards. In contrast, NiW-containing catalysts have been scarcely studied for the hydroconversion of vegetable oils for jet fuel production due to the high price of W precursors and complex transformation of the oxidic precursor of tungsten to the active sulfided state. A continuous pilot plant experiment showed that the Ni–W/SiO₂–Al₂O₃ catalyst could stably function for 100 hours without loss in the yield of bio-jet components (30%).