Dimethyl ether (DME) synthesis from CO2 and H2 through ethanol-assisted methanol synthesis and methanol dehydration

Abstract

Two steps of dimethyl ether (DME) synthesis from CO2 and H2 in a batch reactor were studied, including CO2 hydrogenation to methanol through ethanol-assisted method and methanol dehydration to DME. Additions of 10 wt% ZrO2, Al2O3 and ZrO2–Al2O3 into Cu/ZnO were investigated in low-temperature methanol synthesis using ethanol as catalytic solvent. Suitable zeolite (ZSM-5 and ferrierite) for methanol dehydration was also determined. Ethanol-assisted method offered high methanol yield and Cu/ZnO/ZrO2 catalyst provided the highest CO2 conversion (82.1%) and methanol yield (60.8%) at 150 °C and 50 bar since ZrO2 decreased CuO crystallite sizes and increased surface areas of the catalyst. For methanol dehydration to DME, zeolite's strong acidity related to DME formation. The Cu/ZnO/ZrO2 - Ferrierite provided the highest DME productivity at 0.44 mmolDME/gcat. In addition, DME synthesis from CO2 and H2 through ethanol-assisted methanol synthesis and methanol dehydration can be a potential method to simultaneously produce DME and ethylene. Under the operating conditions, ethylene was produced as a valued by-product of 5.65 mmolEthylene/gcat from dehydration of ethanol. In this study, rather high methanol yield was obtained from ethanol-assisted method. However, DME yield can be further improved by increasing synthesis temperature.