Catalytic activity in methanol synthesis from gas containing CO(2) and H(2), is very low compared with that in synthesis from gas with high CO content provided by steam reforming of natural gas. Therefore, it is necessary to develop a catalyst with high activity. When the molecular pore size of the methanol synthesis catalyst is smaller than the mean free path of the diffusing gases, Knudsen diffusion is dominant. Because the Knudsen diffusion coefficient is proportional to the molecular pore size, studies to improve the methanol synthesis catalyst were conducted by increasing the molecular pore size of the catalyst. The reaction rate and the apparent specific gravity of an improved catalyst with larger pore sizes and larger pore volumes than the original catalyst (main components: CuO-ZnO-Al(2)O(3)-Ga(2)O(3)-MgO) were investigated. The reaction rate per unit weight of catalyst was almost 1.2 times higher, and the apparent specific gravity per unit weight of catalyst was nearly 0.7 times lower for the improved catalyst compared with the original catalyst. DME synthesis using a hybrid catalysts consisting of the methanol synthesis catalyst and a methanol dehydration catalyst was undertaken using a bench-scale test plant. It was determined that: (1) the yield of improved catalyst was the same as that of the original catalyst, (2) the stability of the improved catalyst was the same as that of the original catalyst during 200 h of bench-scale testing, and (3) use of the improved catalyst contributed to a reduction of catalyst consumption, leading to reduced operating costs.