Experimental study on high frequency capacitively coupled plasma–catalysis hybrid system for methane complete oxidation

Abstract

Methane (CH 4 ) is the second most important anthropogenic greenhouse gas in the atmosphere after CO 2 . In this work, CH 4 oxidation was investigated in a high frequency capacitively coupled discharge quartz tube reactor where both catalyst and high frequency capacitively coupled plasma (CCP) were hybridized into one in-plasma catalysis system. The calcium titanium catalyst were used as oxidation catalyst. Experiments have been performed to examine the characteristics of this high frequency capacitively coupled discharge firstly. It was found that the input power and using catalyst or not were the key parameters affecting the plasma characteristics such as plasma length, temperature, and energy transfer efficiency. Then the conversion efficiency of CH 4 and products of reaction were analyzed in the absence of catalyst. The result indicates that the CH 4 conversion efficiency will increase with the increase of input power, the final products of CH 4 oxidation were CO, CO 2 and H 2 O, NO and NO 2 were by-products from the oxidation of CH 4 . The synergistic effect of CCP and catalyst for oxidation was studied also and compared to the cases without catalyst in the reactor. When the catalyst was present, the CH 4 conversion efficiency was improved, the CO 2 selectivity was increased in the reaction product, the by-product concentration of NO and NO 2 was decreased. • Complete oxidation of CH 4 proceeded in the high frequency capacitively coupled plasma–catalysis hybrid system. • Plasma–catalysis hybrid system had much higher CO 2 selectivity compared to plasma only reaction. • Only BaTiO 3 /Al 2 O 3 catalyst demonstrated the synergistic effect of plasma and catalyst on CH 4 oxidation. • The hybrid system was found to be a good way for CH 4 oxidation.