Alcohol Solvent Assisted Synthesis of Metallic and Metal Oxide Catalysts: As-Prepared Cu/ZnO/Al2O3 Catalysts for Low-Temperature Methanol Synthesis with an Ultrahigh Yield

Metallic (Cu/ZnO/Al2O3) and metal oxide (Fe2O3, Co3O4, NiO) catalysts are prepared by a facile alcohol solvent assisted method without additional aging and washing steps. In contrast to the conventional solid-state method using an oxalic acid/M2+ (M = metal cation) molar ratio as high as 4/1, this method is easily operated at room temperature, atmospheric pressure, and an oxalic acid/M2+ molar ratio of only 1.06/1, which prevents the release of lots of flammable gases from the decomposition of excessive oxalic acid. The effect of alcohol solvent types on the physicochemical properties of Cu/ZnO/Al2O3 catalysts and catalytic performance for low-temperature methanol synthesis is systemically studied. Using 1-propanol as solvent, the catalyst realizes an ultrahigh methanol yield of 1782.5 g/kgcat·h–1 at 220 °C and 5.0 MPa, much higher than most reported Cu-based catalysts for conventional high-temperature methanol synthesis. Besides, the Cu/ZnO/Al2O3 catalyst prepared by the alcohol solvent assisted method displayed much higher catalytic activity compared to other catalysts synthesized by conventional methods such as co-precipitation, impregnation, sol–gel, solid-state, and urea hydrolysis. Such good catalytic activity was due to the higher Cu0 surface area, smaller Cu crystallite size, greater surface basicity, and stronger H2 adsorption ability. This work provides not only a hopeful strategy for the large-scale fabrication of metallic and metal oxide catalysts but also a self-catalysis reaction pathway to achieve low-temperature methanol synthesis from CO and CO2 hydrogenation.