Direct and transfer hydrogenation of furfural over MOF-derived Pd-Cu@C catalysts

Owing to the self-reducing ability of palladium acetate in solutions, an ethanol solution containing Pd-0 particles was prepared and coated in-situ into copper metal-organic framework (Cu-MOF), forming Pd@Cu-MOF in a coated structure. The Pd@Cu-MOF was reduced under N-2 or H-2 to form carbon-coated Pd-Cu@C. The pyrolysis and carbonization of Cu-MOF and the reduction of Cu2+ were studied. The Cu-MOF under either N-2 or H-2 was pyrolyzed and carbonized, but the Cu2+ reduction mechanisms were different. The high-temperature carbothermic reduction of Cu2+ under N-2 produced Cu-0, but during low-temperature reduction under H-2, the reducing H-2 reduced Cu2+ to Cu-0. Furfural hydrogenation experiments showed that compared with H-2, the Pd-Cu@C prepared under N-2 reduction displayed higher furfural hydrogenation activity. The catalytic activity of Pd-Cu@C prepared from in-situ Pd-0 coating was higher than the Pd/Cu@C prepared from the impregnation method. With i-propanol as the solvent, the catalytic hydrogenation of furfural under H-2 consisted of direct catalytic hydrogenation with molecular hydrogen as the hydrogen source and catalytic transfer hydrogenation with i-propanol as the hydrogen donor. The catalytic activity of direct catalytic hydrogenation is higher than the catalytic transfer hydrogenation.