Effect of molecular sieve addition on methanol synthesis from CO2 and H2 through alcohol assisted method over CU/ZnO catalyst

Abstract

Low-temperature methanol synthesis from CO2 and H2 was carried out using ethanol as catalytic solvent. The alcohol-assisted method reduced synthesis temperature and enhanced methanol yield (35.8%) at 150 oC (5.0 MPa, Cu/ZnO catalyst). However, ethyl acetate and water were generated as byproducts from the reaction. The byproducts formed azeotrope mixture with methanol and led to a complex product purification. Therefore, in this study, molecular sieves (MS) were introduced to adsorb the byproducts. The effect of different MS (3A and 5A) was studied. It was found that MS helped enhancing methanol yield. The highest methanol yield (42.6%) was obtained when adding MS_3A to adsorb water. The MS_5A could separate methanol and ethyl acetate, providing high methanol purity. The effect of operating temperature was also investigated. When reducing temperature, methanol yield decreased but methanol selectivity significantly increased. The optimum temperature was 130 oC where the pleasant methanol yield (30.6%) and selectivity (>98%) were obtained. Controlling temperature and using MS could help enhance the yield and selectivity of methanol.