Studies On The Preparation Of Dimethyl Ether By Hydrogenation Of Carbon Dioxide

Carbon dioxide is one of the main greenhouse gases. Dimethyl ether (DME) is an important organic chemical product. Hydrogenation of CO₂ to dimethyl ether is an effective way to use CO₂. It is significance in using exhaust air, eliminating the greenhouse effect, improving the energy structure and promoting the use of renewable resources.Preparation of dimethyl ether by hydrogenation of CO₂ is a complex chemical process, including two main steps of CO₂ hydrogenation and methanol dehydration. In this paper, thermodynamics, kinetics, reaction mechanism and catalyst research for the synthesis of dimethyl ether from carbon dioxide hydrogenation were reviewed, and the following works were done:Catalyst of CuO-ZnO-Al₂O₃-Cr₂O₃/HZSM-5 was prepared by uniform gel method. It was characterized by the methods of XRD,FT-IR and TG/DTA. Catalytic activity of CuO-ZnO-Al₂O₃-Cr₂O₃ /HZSM-5 for the synthesis of dimethyl ether from hydrogenation of CO₂ was studied in the differential fixed-bed reactor and the effects of the reaction temperature, pressure and the components of catalyst on the catalytic activity were investigated under the conditions of H2 /CO₂ = 3(volume ratio) and airspeed = 1600 h-1. The result shows that the conversion of CO₂ can be reached to 28.94%, the yield of dimethyl ether is 13.98%, the selectivity and yield of dimethyl ether can reached to 31.76% and 8.76%, respectively under the conditions of pressure at 3 MPa, temperature at 533K,CuO/ZnO = 2/1 (mass ratio) and Cr₂O₃ =1.5-2.0% (mass percentage).Acid modified polygorskite loaded uniform gel of CuO-ZnO-Al₂O₃-Cr₂O₃ was prepared and characterized. It was used for the hydrogenation of CO₂ to form dimethyl ether. Acidified polygorskite can effectively accelerate dehydration of methanol to dimethyl ether. Effect of acid concentration and calcination temperature on modified polygorskite, also as the temperature and the pressure on CuO-ZnO-Al₂O₃-Cr₂O₃/modified polygorskite on hydrogenation of CO₂ to dimethyl ether were investigated, respectively. CuO-ZnO-Al₂O₃-Cr₂O₃ /modified polygorskite shows the highest activity as polygorskite was acidified by 0.2mol/L HCl solution and was calcined at 573K, and hydrogenation was carried out at temperature of 553K and pressure of 3 MPa.