Features of Preparation of the Methanol Synthesis Component of a Bifunctional Dimethyl Ether Synthesis Catalyst

Abstract

The production of dimethyl ether from synthesis gas involves the use of bifunctional catalysts, which mediate the synthesis and dehydration of methanol. The effect is provided by the presence of a methanol synthesis component and a dehydration component in the catalyst; the components can be synthesized independently. The published data on the synthesis of a CuО/ZnО/Al2О3 methanol synthesis catalyst by precipitation from a nitrate solution are conflicting; therefore, it is relevant to study the effect of the procedure and conditions for the precipitation of copper, zinc, and aluminum nitrate solutions with sodium carbonate on the activity of the above catalyst. Data on the phase composition of the precipitates after a heat treatment and the activity of the synthesized catalysts in methanol synthesis suggest that the presence of nitrate groups in the precipitates leads to a decrease in catalytic activity. A method to prepare a methanol synthesis catalyst at room temperature by introducing a solution of copper, zinc, and aluminum salts into a sodium carbonate solution (reverse coprecipitation) is proposed. This method provides the level of activity of the resulting samples directly in methanol synthesis that is close to the level of activity of a commercial methanol synthesis catalyst. Dimethyl ether synthesis in the presence of bifunctional catalysts, in which the methanol synthesis component is prepared by different methods and the dehydration component is commercial gamma-Al2O3, is studied. In the presence of the synthesized samples, the methanol selectivity is almost identical; however, the productivities with respect to oxygenates and dimethyl ether are significantly different.