Gibbs free energy minimization as a way to optimize the combined steam and carbon dioxide reforming of methane

Gibbs free energy minimization was applied to study thermodynamic equilibrium of the combined steam and carbon dioxide reforming of methane. Coke deposition, the content of methane and carbon dioxide in syn-gas as well as H2/CO ratio were investigated as a function of CO2/CH4 and H2O/CH4 mole ratios at different temperatures and pressures. The ranges of the molar ratios CH4/CO2/H2O in the feed with H2/CO = 2.1–2.2 were identified at which reforming of methane is not complicated by coke deposition. For each range optimized CH4/CO2/H2O molar ratios characterized by the lowest content of methane and carbon dioxide in syn-gas were found.