Preparation of high performance nano-sized Cu/ZnO/Al2O3 methanol synthesis catalyst via aluminum hydrous oxide sol

• Methanol synthesis catalysts were prepared by co-precipitation via novel sols.
• Aluminum hydrous oxide sol-based catalysts showed improved catalytic performance.
• TPR profile deconvolutions suggested three CuO types based on ease of reducibility.
• Approach to equilibrium values showed that WGS superpassed RWGS reaction.
• Methanol synthesis rate from CO2 is significantly larger than that from CO.

Ternary Cu/ZnO/Al2O3 methanol synthesis catalysts were synthesized by co-precipitation of copper and zinc hydroxycarbonates in the presence of various aluminum hydrous oxide sol preparation methods from sodium aluminate and aluminum nitrate as aluminum oxide sources. The catalysts were characterized at various stages of preparation by nitrogen adsorption-desorption, X-ray diffraction, transmission electron microscopy, temperature programmed reduction and N2O chemisorption techniques. The TPR profiles of calcined precipitates were deconvoluted into three peaks which were assigned to the reduction of copper oxide species exhibiting different crystallite size and/or different interactions with zinc oxide. All catalysts were tested for methanol synthesis activity in a fixed-bed reactor under conditions similar to that of commercial operation (503 K, 50 bar and GHSV of 17250 h−1), using H2, CO, and CO2 (80/12/8 molar ratio) mixture as the feed. The experimental results illustrated that the catalyst synthesized based on aluminum hydrous oxide sol prepared by peptization of aluminum hydroxide exhibited higher specific surface area, copper dispersion and catalytic activity for methanol synthesis. The catalysts thus prepared were shown to have less hydrotalcite-like phase, stronger interdispersion between Cu and ZnO and well-dispersed Cu nanoparticles with improved stability and activity in methanol synthesis from syngas.

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