Understanding the Reaction Mechanism of Glycerol Hydrogenolysis over a CuCr₂ O₄ Catalyst

The reaction mechanism of glycerol hydrogenolysis to 1,2-propanediol over a spinel CuCr₂ O₄ catalyst was investigated by using DFT calculations. Theoretical models were developed from the results of experimental characterization. Adsorption configurations and energetics of the reactant, intermediates, final product, and transition states were calculated on Cu(1 1 1) and CuCr₂ O₄ (1 0 0). Based on our DFT results, we found that the formation of acetol is preferred to that of 3-hydroxypropionaldehyde thermodynamically and kinetically on both surfaces. For glycerol hydrogenolysis to 1,2-propanediol, the CuCr₂ O₄ surface is less exothermic but more kinetically favorable than the Cu surface. The low activation barrier during the reaction on the CuCr₂ O₄ surface is attributed to the unique surface structure; the cubic spinel structure provides a stable adsorption site on which reactants are allowed to be dehydrated and hydrogenated easily with the characteristic adsorption configuration. The role of the Cu and Cr atoms in a CuCr₂ O₄ surface were revealed. The results of reaction tests supported our theoretical calculations.