Microwave-Driven Nonoxidative and Selective Conversion of Methane to Ethylene over Mn-Based Catalysts.

Recent advancements in microwave-driven nonoxidative catalytic synthesis of C2H4 from CH4 coupling offer a promising, energy-efficient, and eco-friendly alternative to conventional methods, where selective heating under microwave irradiation enables comparable conversions at substantially lower bulk temperatures and shorter reaction times. This study explores the performance of an MnOX-based catalyst supported on CeO2 and HY zeolite (silica-to-alumina ratio = 5.1) for the nonoxidative coupling of CH4 (NOCM) under microwave irradiation. Inspired by the well-established efficacy of MnOX catalyst in oxidative CH4 coupling (OCM), their application in NOCM has also shown significant performance. The catalytic system achieved 15% CH4 conversion and 99% selectivity toward C2 hydrocarbons and maintained 64% selectivity toward C2H4 surpassing the yields reported in the literature even at higher temperatures (700-1000 °C). Catalyst performance was correlated with measurements by in situ Raman spectroscopy, and additional characterizations were performed using H2-temperature programmed reduction , NH3-temperature programmed desorption, and BET surface area analysis to understand structural changes during the reactions. These findings suggested that Mn functions as active sites for CH4 activation in nonoxidative environments while also promoting efficient C-C coupling under microwave irradiation.