Carbon dioxide utilization for methane production: A thermodynamic analysis

Thermodynamic equilibrium analysis of carbon dioxide hydrogenation to methane and side reactions was performed using constrained Gibbs free energy minimization. The applicability for upgrading of CO2-rich natural gas in particular was investigated as a case study. The thermodynamics simulation to obtain equilibrium CO2 conversions and product compositions was performed in the range T=200-550 degrees C, P=1-30 bar and H-2/CO2=1-8 mol/mol. Over the range of practical interest, the carbon dioxide conversion is very high, while the competitive reverse water gas shift is relatively insignificant. Consequently, the equilibrium selectivity to methane is also very high. Below 300 degrees C, in most cases, complete conversion of CO2 to methane with very high selectivity is thermodynamically feasible. The approach to equilibrium analysis of experimental data suggested that over Ni-based catalysts CO2 methanation could occur via reverse water-gas-shift reaction. (C) 2015 Elsevier B.V. All rights reserved.