Observation of reduction on alkane products in butene cracking over ZSM-5 modified with Fe, Cu, and Ni catalysts

The transition metals: iron (Fe), copper (Cu), and nickel (Ni) were doped on ZSM-5 (Si/Al = 20), Na-ZSM-5, and H-ZSM-5 supports by incipient-wetness impregnation to investigate the influence of transition metals loading on the hydrogen transfer reaction in butene cracking. All samples were characterized by XRD, SEM, XRF, N2 adsorption and desorption, FT-IR, NH3-IR, NH3-TPD, UV-VIS, and TPO techniques. It was found that the propylene selectivity increased by the transition metal-loaded catalysts due to the increased medium acid sites on the catalyst surface. The hydrogen transfer index of modified ZSM-5 catalysts was lower than that of the unmodified ones. Moreover, the lack of strong acid sites on ZSM-5 was one of the significant factors that suppressed the formation of light alkanes. Besides, the acidic bridging hydroxyl groups and the external silanol group on ZSM-5 were also active sites during the hydrogen transfer reaction producing light alkanes (propane and butane). Hence, the Na-ZSM-5 exhibited the best performance in terms of propylene yield and catalyst stability. The Niloaded ZSM-5 was the least stable catalyst for the reaction due to high coke content and deactivation rate.

Automated summary

Transition metal-loaded catalysts enhance propylene selectivity and improve hydrogen transfer reaction; Lack of strong acid sites on ZSM-5 is a significant factor suppressing the formation of light alkanes; Na-ZSM-5 exhibits the best performance in propylene yield and catalyst stability.