Thermochemical transformation of CO2 for CH4 production using metal hydride and carbonates as portable sources

Abstract

The thermochemical reaction between MgH2 and Li2CO3 is investigated for the first time for the CO2 transformation into fuels with and without nickel as a catalyst. Successful production of CH4 with high yields is reached depending on different reaction conditions such as microstructural refining, MgH2:Li2CO3 molar ratio, temperature and time. In absence of a catalyst, a methane yield of 68.2% was achieved by heating the milled MgH2:Li2CO3 mixture at 450 °C for 5 h. The global mechanism involves the reduction of CO2 from Li2CO3 by MgH2/Mg, producing CH4 and Li2O/MgO. For the Ni-catalyzed system, the highest methane yield of >90% was reached at 400 °C after 5 h of thermal treatment. The global process responds to a Sabatier reaction, with a contribution of a direct reduction of CO2 depending on the starting mol ratio. The results demonstrate that thermochemical activation of the Ni-catalyzed MgH2:Li2CO3 mixture is a powerful process for the generation of CH4 and CO2 utilization.