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

[Display omitted] • Transition metals (Fe, Cu, and Ni) were impregned on Na-ZSM-5 and H-ZSM-5. • Hydrogen transfer index related with Si-(OH)-Al and external silanol group. • Transition metals loading on ZSM-5 enhanced propylene selectivity. • Both medium acid site and metal site participate in propylene production. • Coke content on metal was in the order of nickel > iron > copper. 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, N 2 adsorption and desorption, FT-IR, NH 3 -IR, NH 3 -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 Ni-loaded ZSM-5 was the least stable catalyst for the reaction due to high coke content and deactivation rate. [ABSTRACT FROM AUTHOR]