Development of a bimetallic Cu/Mg/MCM catalyst for glycerol hydrogenolysis to propanediol without external hydrogen

Abstract

The catalytic performance of all monometallic and bimetallic catalysts for the hydrogenolysis of glycerol to 1,2-propanediol (1,2-PDO) and 1,3-propanediol (1,3-PDO) was evaluated in a high-pressure batch reactor operated at 180–220 °C for 1–4 hours under 5 bar (1,2-PDO) and 20 bar (1,3-PDO) of N₂ using various solvents as in situ hydrogen sources with different catalyst loading (0.1–0.5 g). Commercial Al-MCM-41 was impregnated with different contents of monometallic Cu and different ratios of Cu/Mg/MCM via the incipient wetness impregnation technique, followed by drying at 100 °C for 24 hours and calcination at 550 °C for 5 hours. The catalysts' physicochemical properties were analyzed using XRD, N₂ adsorption–desorption isotherms, and H₂-TPR. The XRD patterns of all the synthesized catalysts revealed diffraction peaks corresponding to a well-ordered two-dimensional hexagonal structure of the MCM support at low angles, along with the presence of CuO and MgO phases at higher angles. A progressive decrease in the surface area and pore volume was observed with increasing the Cu and Mg loading. The association of Cu with Mg in a synergistic interaction resulted in decreasing the reduction temperature, proving the occurrence of the MgO hydrogen spillover effect as the Cu content was greater than that of Mg. The performance of all catalysts was assessed in glycerol hydrogenolysis reactions without the addition of external hydrogen gas to investigate the influence of Cu/Mg loading on the MCM-supported catalyst efficiency for the production of 1,2-PDO and 1,3-PDO.