Thermodynamic Analysis on Reaction Characteristics of the Coupling Steam, CO2 and O2 Reforming of Methane

Abstract

This study presents an analysis of coupling steam, CO2 and O2 reforming of CH4 using the thermodynamic equilibrium constant method. Effects of molar ratio of O2/CH4, H2O/CH4 and CO2/CH4 on reforming characteristics in both carbon deposition and carbon-free systems are analyzed. The results indicate that CH4 conversion rate, H2, and CO yield increase with increasing O2/CH4 molar ratio in two systems. In addition, the carbon elimination is achieved when O2/CH4 ratio increases to 0.31, and changing the amount of O2 can be an effective way to alter n(H2)/n(CO) ratio in the carbon deposition systems. CH4 conversion rate increases with increasing H2O/CH4 ratio in the carbon-free system, while it declines in the carbon deposition system. H2O plays a role of altering n(H2)/n(CO) ratio, and its effects on two systems are opposite. The deposited carbon is totally eliminated when H2O/CH4 ratio increases to 0.645. The increase of CO2/CH4 molar ratio leads to a rapid increase of CO2 conversion when CO2/CH4 ratio is less than 0.5. A slightly change of CO2/CH4 ratio can result in a huge difference on n(H2)/n(CO) ratio in both systems, and carbon elimination is achieved at CO2/CH4 = 0.99. The analyzed results have theoretical significance to efficiently catalyze methane coupling.