Warm-plasma catalytic reduction of CO2 with CH4

Abstract

Toward developing an efficient plasma-based technique for CO2 reduction with CH4, warm-plasma catalytic (WPC) reduction of CO2 with CH4 in a reactor using gliding arc discharge and Ni/CeO2/Al2O3 catalyst is reported. In the warm plasma (WP) case, besides dry reforming reaction, reverse water gas shift (RWGS) reaction also comparably contributes for CO2 reduction. Although the contribution of dry reforming reaction is significantly enhanced by the increase of CH4/CO2 ratio, it accounts for only 60% due to the limitation of maximum CH4/CO2 ratio by the serious carbon deposition at CH4/CO2 >1/2. In addition, the low CH4/CO2 ratio also results in the low CO2 conversion, H2/CO ratio and H2 selectivity. In the WPC case, extra CH4 was fed after plasma to increase the CH4/CO2 ratio to 1, dry reforming reaction becomes the major contributor of CO2 reduction. Under the conditions of specific energy input of 86 kJ/mol, total flow rate of 2.67 SLM, catalyst-bed temperature of 850 °C and gas hourly space velocity of 3200 h−1, CO2 conversion of 91% and CH4 conversion of 94% with H2/CO = 1 and nearly 100% H2 selectivity are achieved with a CO2 energy cost of 598 kJ/mol and an energy efficiency of 72%.