Reactivity of Methane and Benzene over Metal/MFI Zeolite Analyzed with Temperature‐Programmed Reaction Technique

• Published in: ChemCatChem Vol. 12; no. 8; pp. 2333 - 2340
• Main Authors: Nakamura, Koshiro, Okumura, Kazu, Tsuji, Etsushi, Suganuma, Satoshi, Katada, Naonobu
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 20.04.2020
• Subjects: Benzene; Deactivation; Dehydrogenation; High temperature; Hydrocarbons; Ion exchange; Metal/MFI; Methane; Methylation; Oxidation; Rhodium; Selectivity; Temperature-programmed reaction; Valence; Zeolites
• ISSN: 1867-3880; 1867-3899
• DOI: 10.1002/cctc.202000030

Reactivity of methane and benzene over various metals supported on MFI zeolite was investigated in a wide range of temperature by a temperature‐programmed reaction method. The oxidation state was also analyzed, as supported by X‐ray absorption near edge structure (XANES). Pt, Rh, and Rh on MFI were reduced at <600 K, and showed high activity for both benzene methylation and methane dehydrogenation, and hence, low selectivity for the methylation at high temperature. The short catalyst life of Pt/MFI suggests deactivation due to carbonaceous produced by the dehydrogenation. The oxidation state of Co species on ion exchange site of MFI was kept at +II in the experimental range (<843 K), and relatively high selectivity was observed on Co/MFI even at high temperature. Stable oxidized state of Co species thus contributed to catalyze the target reaction (methylation of benzene with methane). Temperature programmed reaction (TPR) using methane and benzene was performed over metal/MFI catalysts in 373–843 K to investigate the reactivity and oxidation states, with an aid of X‐ray absorption near edge structure (XANES). Cationic cobalt species on MFI was stable during the reaction, unlike noble metals, and mainly catalyzed methylation of benzene with methane over a wide range of temperature.