Preparation of Imidazole-modified HZSM-5 Zeolite and Its Application in the Catalytic Synthesis of Dimethyl Ether from Hydrogenation of Carbon Dioxide

Imidazole modified HZSM-5 zeolite was prepared by hydrothermal synthesis method using tetrapropylammonium hydroxide as template and imidazole as additive. The samples were characterized by means of the methods of XRD,SEM,EDS,BET,TG and NH 3-TPD. The results show that the addition of a small amount of imidazole can produce uniform and smaller HZSM-5 zeolite particles with higher acidity and perfect resistance to high temperature. The CuO-ZnO-Al 2 O 3 / imidazole-modifiedHZSM-5 bifunctional catalyst was prepared by impregnation method and its catalytic activity for the hydrogenation of carbon dioxide to synthesize dimethyl ether was investigated. Under the conditions of reaction pressure 3. 0 MPa,space velocity( SV) 1 800 mL /( g cat ·h),volume ratio of CO 2 / H 2 1 ∶ 3, temperature 270 ℃,molar ratio of CuO / ZnO 2 ∶ 1 and mass ratio of CuO-ZnO-Al 2 O 3 / imidazolemodified-HZSM-5 2∶1,the conversion of CO 2 and selectivity of dimethyl ether can reach 42. 3% and 33. 1%,respectively.