Catalysis Of Syngas One-step Synthesis Of Dimethyl Ether

Dimethyl Ether (DME) is not only an important chemical, but also an ideal substitute for diesel or liquefied petroleum gas. Furthermore, DME is also an important chemical feedstock for the preparation of light alkenes. So, the application prospect of DME becomes wider. In recent years, DME synthesizing from synthesis gas has attracted much attention in research fields and industrial fields for its low cost and low energy consumption.The single-step Syngas-to-Dimethyl ether process was investigated in a fix-bed reactor. A series of catalysts were prepared with mechanical mixing, precipitation sedimentation and impregnation method. These catalysts were investigated by means of XRD, TPR, TG-DTG, and BET. The effects of some technical conditions on the one-step Syngas-to-Dimethyl ether catalysts have been studied respectively, which include reaction temperature, reaction pressure, reaction gas GHSV, prepared temperature, pH, calcination temperature, the ratio of Cu/Zn, ZrO2 contents, MS (methanol synthesis )/MTD (methanol to DME) and promoters etc...The results show that the optimum technical condition is 533 K of reaction temperature, 3.0 Mpa of reaction pressure; 1000~3000 h-1 of reaction gas SHSV About the catalysts of being prepared with different methods, the rank of CO conversion is precipitation sedimentation> mechanical mixing> impregnation method. In these catalysts, the catalysts which were prepared with mechanical mixing method have best DME yield. Prepared temperature and pH could affect catalysts performance. When prepared temperature was 353 K and pH was 8.0, the catalysts had the best performance. The ratio of catalysts (CuO-ZnO-ZrO2/HZSM-5) affects catalysts performance also. When Cu/Zn was 3:7, MS/ MTD was 3:1-2:1, ZrO2 may improve the performance of bifunctional catalysts. When ZrO2 contents are 6.0 mol %, CO conversion , DME selectivity and the over-heating tolerance arrived the best . Based on the results of XRD and TPR analysis, it can be concluded that addition of ZrO2 is benefit for the active components to be dispersed in the catalysts better, whichmay prevent the catalysts from sintering at higher temperature and enhance the reduce capability of the catalysts also. About MTD catalyst, HZSM-5 could be a well catalyst performance. And the addictives of catalysts could also affect catalysts performance. Al, Mg, Mn addictives could improve catalysts DME selectivity, so they were the good addictives in these catalysts.The over-heating tolerance of catalysts was investigated. Catalyst performance was worse when after over-heating tolerance. The reason of catalysts deactivation could be the CuO sintering and collapsing of molecular formula. Otherwise, the reason may also be the flowing of CuO into the hole of molecular formula.