Role of Acid Centers over Ni/ZSM-5 Catalysts for Hydrodeoxygenation of Methyl Laurate to Biojet Fuels
Tinghu Wang, Yuzhi Li, Wenjing Zhang, Furang Li, Lei Fan, Jianye Fu, Xinmei Liu, Yuchao Lyu
Abstract
Acidity of supports always plays a key role in the determination of dispersion and electron density of metal components and then the catalytic behavior of bifunctional catalysts for deoxygenation of biomass-based resources. Herein, Ni/ZSM-5 catalysts with various Si/Al ratios and acidity were synthesized, and the role of acid centers in the deoxygenation of methyl laurate (ML) was discussed. The decreasing Si/Al ratios promote dispersion of Ni due to the anchoring effect of framework Al to nickel species. It also increases the electron density of Ni, which not only benefits the activation of hydrogen but also curbs the cleavage of C–CHO bonds. All of these accelerate ML transformation and preferentially promote the hydrodeoxygenation (HDO) route instead of decarboxylation (DCO 2 ) or decarbonylation ones. The metal centers play a key role in the hydrogenolysis of ML and the hydrogenation of resultant fatty acids, while the acid centers can facilitate these processes. Besides, suitable acidity of the catalyst would increase selectivity to target alkanes and isomerized ones for biojet fuels by enhancing the HDO routes. However, excessive acid centers favor cracking reactions, reducing the selectivity of target products. This work contributes a profound understanding of the role of acid centers in the deoxygenation of ML into biojet fuels and can be extended to other bifunctional deoxygenation catalysts.