Three reactions involved in dimethyl ether (DME) synthesis from COhydrogenation: methanol synthesis reaction (MSR), methanol dehydration reaction (MDR) and water gasshift reaction (WGSR) are studied by thermodynamic calculation. For demonstrating this process indetail, three models, MSR, MSR+MDR, MSR+MDR+WGSR, are used. Their basic characteristics can beobtained by varying widely the ratios of H_2 to CO in the feed (no CO_2). Through thermodynamicanalysis a chemical synergic effect obviously exists in the second and third models. By comparisonbetween two models it is found that WGSR plays a special role in dimethyl ether synthesis. It ispossible for the two models to shift one to the other by regulating CO_2 concentration in feed. ForModel 2, the selectivity for DME in oxygenates (DME+methanol) does not change with the ratio of H_2to CO.
