A comparative thermodynamic study on the CO2 conversion in the synthesis of methanol and of DME

Abstract

A thermodynamic approach of the synthesis processes of methanol and DME from H2+CO+CO2 has been conducted, in order to compare the feasibility of incorporating CO2 in the feed of both processes. The effects of reaction temperature (200-400 ºC), pressure (10-100 bar) and CO2/(CO+CO2) ratio in the feed on the CO2 conversion, yield and selectivity of oxygenates (methanol + DME), and heat released in each process have been studied. CO2 conversion is strongly dependent on the CO2 content in the feed and is higher in the DME synthesis for high CO2 concentration values in the feed (CO2/(CO+CO2) > 0.75). The increase of reaction temperature has a favorable effect on the oxygenate yield and selectivity, while the increase of reaction pressure and the increase of CO2 content in the feed have an unfavorable effect. Comparing both processes, higher oxygenate yield and selectivity values are obtained in the synthesis of DME, which is more relevant for CO2 rich feeds. Moreover, feeding CO2 lessens the exothermic nature of both processes which is a positive effect for protecting the metallic function of the catalyst, as the formation of hot spots is avoided.