Dimethyl ether synthesis from carbon dioxide by catalytic hydrogenation (Part 1) activities of methanol dehydration catalysts

The authors have developed CuO-ZnO-Al2O3-Ga2O3-MgO catalyst for methanol synthesis from CO2 and H-2, and have been studying a technology for the direct synthesis of dimethyl ether (DME) from CO2 and H-2 using the combination of the methanol synthesis catalyst above mentioned and a methanol dehydration catalyst. In the present study, the catalytic activities of three types of gamma-Al2O3 with different specific surface areas, four types of compound oxides (ZrO2 . Al2O3, SiO2 . Al2O3, SiO2 . TiO2, ZrO2 . TiO2), and a ZSM-5 zeolite for DME synthesis by methanol dehydration were tested. DME synthesis activity increased with higher specific surface area of gamma-Al2O3 catalyst. Compound oxide catalysts containing Al2O3 showed higher DME synthesis activity than catalysts without Al2O3, and ZrO2 . Al2O3, the best compound oxide, showed higher DME synthesis activity than the best gamma-Al2O3 with the largest specific surface area (250 m(2)/g). Addition of a metal oxide as the promoter is effective for improving the DME synthesis activity of Al2O3 by methanol dehydration. ZSM-5 zeolite produced more olefins rather than DME. The presence of water in the methanol feed suppressed the DME synthesis reaction by methanol dehydration.