Oxidative coupling of methane with microwave and RF plasma catalytic reaction over transitional metals loaded on ZSM-5

Abstract

In the microwave and radio frequency (RF) plasma catalytic reaction at room temperature, the oxidative coupling of methane (OCM) over transitional metals loaded on ZSM-5 has been carried out. The transitional metals, Fe, Ni, Co and Cu (1B family element), loaded on ZSM-5 have been tested for the OCM using the plasma catalytic reaction. In this work, the conversion of methane to C2 products has been improved without the carbon deposition when the oxygen as a co-reactant gas was supplied. The order of the catalysts of higher conversion to C2 products in the microwave plasma reaction with plasma power of 120 W is Co–ZSM-5>Fe–ZSM-5≒Cu–ZSM-5>Ni–ZSM-5. Selectivity to ethylene is as high as 29.8%, to ethane 10% and to acetylene 49.9% and conversion of methane was as high as about 54.9% with pressure of 5–10 Torr, total flow rate of 125 ml/min and a methane/oxygen ratio of 4:1 over Co–ZSM-5. It is suggested that the catalyst may provide an active site for combination of radicals. It was found that yield of C2 products has been enhanced in the microwave plasma catalytic reaction, as microwave plasma system of high frequency has better energy efficiency than RF plasma system of low frequency.