Thermodynamic analysis of carbon dioxide reforming of methane and its practical relevance

•Equilibrium compositions provide good estimates for CO2 reforming reactor outlets.•Sequentially, CO2 reforming is equilibrated first followed by steam reforming.•Steam reforming approaches to equilibrium in reverse direction via RWGS reaction.•CO equilibrium selectivity maximizes at CO2/CH4 ratios slightly larger than unity.•Ni/MgO catalyst shows stable CO2 reforming approach to equilibrium close to unity.

Thermodynamic equilibrium analysis of reforming of methane with carbon dioxide (dry reforming) and in combination with steam reforming (mixed reforming) was performed using constrained Gibbs free energy minimization method. The results were compared with that of a commercial plant reactor and our experimental data over Ni/MgO catalysts tested in a fixed-bed quartz reactor. It was concluded equilibrium values are good measures of reaction performance and could be used for prediction of reaction performance and coke formation studies. Numerical values 1.02 and 1.96 were obtained for approach to equilibrium of carbon dioxide reforming and steam reforming reactions, respectively, at 850 °C and space velocity of 530 ml/h.gcat. These values illustrated that, during dry reforming; first carbon dioxide reforming equilibrates, and then steam reforming reaction approaches to equilibrium in the reverse direction.

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