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

Area of Science:

• Catalysis
• Chemical Engineering
• Materials Science

Background:

• Nonoxidative methane coupling (NOCM) is crucial for converting methane into valuable C₂ hydrocarbons.
• Conventional NOCM often requires high temperatures, leading to energy inefficiency and catalyst deactivation.
• Microwave irradiation offers selective heating, potentially improving energy efficiency and reaction kinetics.

Purpose of the Study:

• To evaluate the performance of an MnOₓ-based catalyst supported on CeO₂ and HY zeolite for microwave-driven NOCM.
• To investigate the catalytic activity and selectivity under microwave irradiation for methane conversion to ethylene.
• To understand the role of manganese active sites in methane activation and C-C coupling under nonoxidative conditions.

Main Methods:

• Utilized an MnOₓ/CeO₂/HY zeolite catalyst for nonoxidative coupling of methane (NOCM) under microwave irradiation.
• Performed in situ Raman spectroscopy to monitor catalyst behavior during reaction.
• Conducted H₂-temperature programmed reduction, NH₃-temperature programmed desorption, and BET surface area analysis for catalyst characterization.

Main Results:

• Achieved 15% CH₄ conversion with 99% selectivity towards C₂ hydrocarbons.
• Maintained 64% selectivity for C₂H₄, surpassing literature yields at higher temperatures.
• Demonstrated efficient C-C coupling and CH₄ activation attributed to Mn active sites under microwave irradiation.

Conclusions:

• Microwave-driven NOCM using MnOₓ catalysts is a viable and energy-efficient alternative to conventional methods.
• The MnOₓ/CeO₂/HY zeolite catalyst exhibits high performance in terms of methane conversion and C₂H₄ selectivity.
• Manganese active sites play a key role in methane activation and C-C coupling, enhanced by microwave heating.