Hydrogenation of furfural over Pd@ZIF-67 derived catalysts: direct hydrogenation and transfer hydrogenation.

Pd particles coated with ZIF-67 (Pd@ZIF-67) was prepared from the self-reduction of palladium acetate. With isopropanol as the solvent, the furfural hydrogenation reaction performances of Pd@ZIF-67 and ZIF-67 heated at different temperatures were tested in H₂ and N₂ reaction atmosphere, respectively. The pyrolytic carbonization of Pd@ZIF-67 and ZIF-67 produced Pd–Co@C and Co@C in carbon coating structures, respectively. It was found that furfural hydrogenation reaction systems with different catalytic active sites included direct hydrogenation with H₂ as the hydrogen source, and transfer hydrogenation with isopropanol as the hydrogen donor. The Pd–Co@C and Co@C with metal active sites both experienced direct hydrogenation and transfer hydrogenation simultaneously, and the direct hydrogenation activity was higher. The ZIF-67 with Lewis acidic sites experienced transfer hydrogenation, and the catalytic activity was higher than the transfer hydrogenation activity of Pd–Co@C and Co@C. Moreover, reaction routes in which furfural direct hydrogenation and transfer hydrogenation occurred in metal active sites and Lewis acidic sites were identified. [ABSTRACT FROM AUTHOR]