Highly active bifunctional Pd-Co9S8/S-CNT catalysts for selective hydrogenolysis of 5-hydroxymethylfurfural to 2,5-dimethylfuran

Abstract A series of Pd-Co bimetallic catalysts were smoothly synthesized using sulfur-modified carbon nanotubes (S-CNT) as support by impregnation method. Those catalysts were characterized by XRD, XPS, TEM, SEM, H2-TPR, TGA, and nitrogen adsorption-desorption. Selective catalytic hydrogenolysis of 5-hydroxymethylfurfural (HMF) to 2,5-dimethylfuran (DMF) was realized over these synthesized sulfur-modified Pd-Co bimetallic supported on carbon nanotubes (PdCox/S-CNT) under mild conditions. Among them, PdCo8/S-CNT catalyst possessed extremely active and selective for the production of DMF, giving 96.0 % conversion of HMF with 83.7 % selectivity to DMF at the temperature of 120 °C with 0.3 MPa H2 for 13 h. It is found that the formed Co9S8 species are related to the high catalytic activity in PdCo8/S-CNT. Control experiments for evaluating the roles of palladium and Co9S8 revealed that Pd catalyzed the hydrogenation of the aldehyde group in HMF whereas Co9S8 was beneficial for hydrogenolysis of the hydroxy group in HMF. The remarkable hydrogenolysis/hydrogenation performance of the bifunctional Pd-Co9S8/S-CNT was due to support-enhanced adsorption effect and the effective synergy between highly dispersed metallic Pd and the Co9S8 nanoparticles.