Effect of Reduction Protocol of Pd Catalysts on Product Distribution in Furfural Hydrogenation

Single step conversion of furfural to ring hydrogenation and decarbonylation products, 2-methyltetrahydrofuran (2-MeTHF) and tetrahydrofuran (THF) in high selectivity was achieved by controlling the particle size of Pd/C catalyst. The particle size variation of Pd/C catalysts in the range of 3.8 to 22 nm could be achieved by employing different reducing agents. Of particular interest was the NaBH4 reduced catalyst (Pd−B/C), which gave the lowest crystallite size of 4.8 nm due to incorporation of B into the inner lattices of Pd−Pd. This phase was evidenced by a characteristic XRD peak of Pd−B at 2θ=38.85 O as well as a shift of (111) peak (40.07 O) of Pd towards the lower value (39.8 O). As compared to formaldehyde reduced catalyst (Pd−F/C), Pd−B/C catalyst completely suppressed the formation of furfuryl alcohol to give > 65 % selectivity to 2-MeTHF and THF. At 180 OC, almost equal distribution of side chain hydrogenation and ring opening products, 2-MF (45 %) and PeDO (37 %), respectively, was observed while, higher temperature clearly favoured ring hydrogenation and decarbonylation reactions to give 2-MeTHF and THF.