Nano-ZSM-5 decorated cobalt based catalysts for Fischer-Tropsch synthesis to enhance the gasoline range products selectivity

Abstract

The amount of acid sites is crucial for modifying the product selectivity for Fischer-Tropsch synthesis (FTS) since the acid sites may affect the hydrocracking performance of heavy hydrocarbons. Fewer acid sites usually present poor hydrocracking ability while the excessive acid sites result in over hydrocracking of heavy hydrocarbons. Here, a kind of hybrid Co/M-Z catalyst with different amount of acid sites was prepared by mixing different amount of nano-H-ZSM-5 zeolite with Co/M catalyst, which combined the great activity and stability of Co/M (Co/MCF) catalyst and the acid function of nano-H-ZSM-5 zeolite. The NH3-TPD result indicates that the amount of acid sites increased to 1.96 × 10−4 mol gcat−1 with the mass content of nano-H-ZSM-5 zeolite increasing to 80 wt%. N2-adsorption desorption result proves the Co/M catalyst presents suitable mass transfer ability. FTS performance indicates that CO conversion, STY value and the C21+ product selectivity decrease with the content of nano-H-ZSM-5 zeolite increase. While, the CH4 selectivity is on the opposite. Among these catalysts, the Co/M-Z catalyst presents the highest C5-11 selectivity (53.5%) due to the suitable amount of acid sites.