Bifunctional catalysts for conversion of synthesis gas to dimethyl ether

The effects of preparation methods and dehydration components on catalytic properties and the structures of bifunctional catalysts were investigated. Catalytic synthesis of dimethyl ether from synthesis gas was evaluated in a fixed-bed flow microreactor at a pressure of 4.0 MPa and a GHSV of 1500 h(-1). Characterization of catalysts has been carried out using XRD, TPR, Pyridine-TPD, CO2-TPD and XPS. The experimental results show that CuO-ZnO-Al2O3/HZSM-5 and CuO-ZnO-Al2O3/HSY catalysts, which were prepared by a coprecipitating sedimentation method, exhibit the highest catalytic activity for direct synthesis of dimethyl ether from synthesis gas with 89% CO conversion and 99% selectivity of dimethyl ether (in organic products). In addition, the results indicate that the dehydration step of the reaction occurs on the weak acidic sites and there is a 'synergistic effect' between the two kinds of active components in bifunctional catalysts. (C) 1998 Elsevier Science B.V.