Investigation on CuO-ZnO-Al_2O_3/HZSM-5 Catalysts for Synthesis of Dimethyl Ether from CO_2 Hydrogenation

Bifunctional catalysts of CuO-ZnO-Al2O3/HZSM-5 for dimethyl ether synthesis from hydrogenation of CO2 were directly prepared by parallel-flow-coprecipitation method,using anhydrous ethanol as solvent,and oxalic acid as precipitator.The catalytic performance of the catalyst was studied.The influence of mass ratio of the hydrogenation component(CuO-ZnO-Al2O3) to the methanol dehydration component(HZSM-5) and the stability of the catalyst were investigated.The experiments results demonstrated that there existed an optimal mass ratio between the two components of the CuO-ZnO-Al2O3/HZSM-5 bifunctional catalysts for dimethyl ether synthesis.At 270 ℃,3.0 MPa,space velocity 4 800 h-1,the one way conversion of CO2 was 29.8%,the selectivity and the yield of dimethyl ether could reach 53.8% and 16%,respectively.XRD,BET,TPR and NH3-TPD were employed to investigate the structure and surface performance of the catalysts.The results indicated the crystallization degree,grain size and the reducibility of the CuO of the hydrogenation component,as well as the acidic property of the dehydration component of HZSM-5,were highly determined by the mass ratio of the two components of the catalysts.