Effect of nickel on catalytic behaviour of bimetallic Cu–Ni catalyst supported on mesoporous alumina for the hydrogenolysis of glycerol to 1,2-propanediol

Abstract

The catalytic conversion of glycerol to 1,2-propanediol by hydrogenolysis has potential use in the commercial biomass industry. However, the high hydrogen pressure required for the reaction is a major drawback. To overcome this limitation, in this study, we added nickel metal to a copper-based catalyst for both supplying hydrogen via aqueous-phase reforming (APR) of glycerol and improving selectivity for 1,2-propanediol in hydrogenolysis. The bimetallic Cu–Ni catalyst supported on mesoporous alumina (MA) was prepared by a sol–gel method. The prepared Cu–Ni catalyst contains ordered mesopores with high surface area and well-dispersed active sites, as confirmed by BET, TEM, XRD, and TPR. The 9Cu–1Ni/MA (molar ratio of copper to nickel: 9 : 1) catalyst showed the highest catalytic performance among the various xCu–yNi/MA catalysts in a low pressure of H₂. The XPS results showed that the surface ratio of Ni to (Cu + Ni) and Cu⁰/(Cu⁰ + Cu²⁺) is closely related to catalytic performance, selectivity and yield. The effect of nickel on the hydrogen production was experimentally proven by the time-on-stream tests over monometallic (Cu) and bimetallic (Cu–Ni) catalysts in the absence of hydrogen. The optimum value of the ratio of Ni to Cu is varied with the conditions in the presence of H₂. The reaction mechanism was proposed for the Cu–Ni bimetallic catalysts for hydrogenolysis with APR of glycerol.