Catalytic activity of Cu–Zn–Al–Mn admixed with gamma-alumina for the synthesis of DME from syngas: manganese effect or just method of preparation?

Abstract

A series of methanol synthesis catalysts, CuO/ZnO/Al₂O₃ and CuO/ZnO/Al₂O₃ containing 5 mol% of manganese physically admixed with γ-Al₂O₃ were tested for the direct synthesis of dimethyl ether from syngas. The catalysts were prepared by coprecipitation of the metal nitrates with several types of alkali carbonate solution. Aqueous solutions of Na₂CO₃, NaHCO₃/Na₂CO₃ buffer, and NaHCO₃ were used as the precipitating agents to investigate the effects of the preparation method on the microstructure of the precursors and on the physicochemical properties and reactivity of the resulting catalysts. It was found that the most responsible factor in determining the catalytic activity of the methanol synthesis catalyst is the preparation method rather than the incorporation of manganese as the structure modifier. There is a substantial correlation between the copper metal surface area and the activity of the catalyst derived from the structurally active precursor, hydrotalcite-like layered double hydroxides.