Theoretical study on the feasibility of intramolecular hydrogen transfer reaction of 5-hydroxymethylfurfural

The intramolecular hydrogen transfer reaction (IHTR) of 5-hydroxymethylfurfural can potentially reach a 100% atomic economic efficiency, which is of great significance to the utilization of biomass raw materials. In this work, the feasibility of IHTR on Cu, Pd and Cu3Pd2 bimetallic catalysts was investigated by density functional theory (DFT) calculations. Eight intramolecular hydrogen-transfer pathways, consisting of four elementary reactions each, are proposed. The elementary reactions were categorized and discussed as follows: C-H bond cleavage, C-2(H)=C-3 hydrogenation, O-H bond cleavage and C-2=C-3(H) hydrogenation. The relevant adsorption, activation and reaction energies were calculated and compared. Results reveal that the C-H bond is not easy to break on Cu(111). On the surface of Pd(111), both the O-H bond cleavage and C=C bond hydrogenation reactions require higher energy barriers to overcome. Cu3Pd2(111) demonstrates high activity for both hydrogenation and dehydrogenation reactions. The reaction steps of the lowest energy path on Cu3Pd2(111) involve C-H bond cleavage, C-2=C-3(H) hydrogenation, O-H bond cleavage and C-2(H)=C-3 hydrogenation. The rate-limiting step is the cleavage of the C-H bond, and its activation barrier is 0.89 eV. As a result, the Cu3Pd2(111) catalyst is predicted to be the most active catalyst for intramolecular hydrogen migration, while the Cu(111) surface is also conducive to the IHTR reaction with slightly higher energy barrier. The calculation results provide valuable theoretical basis for the optimization of experimental research.