Nature of the interactions between Fe and Zr for the methane dehydroaromatization reaction in ZSM-5

Abstract

Methane is an abundant feedstock with steadily increasing availability due to recent technological developments. The methane dehydroaromatization reaction is a possible chemical route to convert methane into benzene, which has a higher energy density. This reaction presents thermodynamic limitations on benzene production, while coke formation is favored. In a previous work, the combination of Fe and Zr in ZSM-5 catalysts showed promising results regarding selective prevention of coke deposition, favoring benzene production. In this work, FeeZr/ZSM-5 catalysts were synthesized with varying Zr/Fe ratios and characterized with XRD, BET, TPR-H 2 , TPD-NH 3 , Raman and TEM in order to better understand the effects of Zr over Fe. DFT calculations were used to investigate the interactions between Zr and Fe within the ZSM-5 structure. Experimental and computational results show that mixed FeeZr oxides were not formed, and ZrO 2 and Fe 2 O 3 oxides were deposited on the ZSM-5. The Zr was found to promote Fe 2 O 3 reduction to Fe 0 and deposit in the Brønsted acid sites of the zeolite, which could explain the decreased induction period and coke deposition in FeeZr/ZSM-5 catalysts for methane dehydroaromatization observed in previous works.