Vapor-phase hydrogenolysis of glycerol to value-added 1,2-propanediol over copper-nickel bimetallic catalysts supported on activated carbon

In the production of biodiesel, a sustainable energy alternative to fossil fuel, surplus glycerol, is generated as a by-product. Valorization of excess glycerol is the most promising approach for rendering the biodiesel sector fiscally practical. Herein, copper and nickel monometallic and bimetallic catalysts supported over activated carbon were developed using the incipient wetness impregnation technique for the hydrogenolysis of vapor-phase glycerol to 1,2-propanediol (1,2-PDO) at a pressure of 0.75 MPa and temperature of 220 °C. The catalysts were characterized by Brunauer-Emmett-Teller, X-ray diffraction, H₂-temperature-programmed reduction, NH₃-temperature-programmed desorption, X-ray photoelectron spectroscopy, and scanning electron microscopy analyses. The bimetallic catalysts afforded higher product yields than the monometallic catalysts did in glycerol hydrogenolysis. Cu-Ni(1:1)/AC gave the maximum yield of 1,2-PDO (87.3%), with high glycerol conversion (95.7%) under the previously mentioned reaction conditions, with a comparatively low molar ratio of hydrogen to glycerol (54.6). The strong copper-nickel synergy, smaller crystallite size, and high acid strength of Cu-Ni(1:1)/AC account for this superior performance.