Co-reaction of methanol and alkanes with different carbon numbers over microsphere catalysts

Abstract

The co-reaction of methanol with C₅–C₁₆ n-alkanes was investigated over microsphere catalysts with varying surface acidity and ZSM-5 as the active components. The results indicate that, as the carbon number of alkanes increases, the formation of C₁–C₄ alkanes decreases while the production of C₂–C₄ alkenes increases on the catalyst with weak outer surface acidity. This suggests that side reactions such as alkene aromatization and hydrogen transfer are suppressed. Conversely, on the catalyst with strong outer surface acidity, further reaction of olefins significantly increases, leading to a gradual decrease in light olefin yield and a corresponding increase in benzene, toluene, xylene, and heavy aromatics. Additionally, it is observed that long-chain n-alkanes (the kinetic diameter of n-hexadecane exceeds the pore size of ZSM-5 zeolite, the active component in the microspherical catalyst) cannot enter the internal pores of ZSM-5, resulting in primary cracking due to the acidic sites on the outer surface. However, long-chain n-alkanes can adjust their molecular orientation on pure ZSM-5 zeolites and enter the pore structure, leading to alkane cracking influenced by both internal and external surface acidity. These findings provide valuable guidance for the design of industrial catalysts, particularly in terms of pore size and acidity.