Production of biofuel 2,5-dimethylfuran using highly efficient single-step selective hydrogenation of 5-hydroxymethylfurfural over novel Pd-Co/Al-Zr mixed oxide catalyst

Abstract

Sustainable and cleaner production of liquid biofuel 2,5-dimethylfuran (DMF) is in great demand. Because of its water insolubility, high boiling point, and high energy density, DMF seems to be a promising liquid biofuel. Selective hydrogenation of biomass-derived 5-hydroxymethylfurfural (HMF) to 2,5-DMF can be achieved using novel catalysts and is presented here. In this study, a series of Al-Zr mixed oxide catalysts (AZMO) were prepared by co-precipitation and hydrothermal techniques. AZMO catalyst prepared by the co-precipitation method gave higher acidity and surface area. Furthermore, mono and bimetallic M/AZMOCP (M = Ni, Co, Cu, and Pd) catalysts were developed by the impregnation and used for hydrogenation of HMF. The catalytic activity was found in the order of: 2%Pd-5%Co/AZMOCP > 1%Pd-5%Co/AZMOCP > 2%Pd-3%Co/AZMOCP > 1%Pd-3%Co/AZMOCP > 5%Ni-5%Co/AZMOCP > 1%Pd/AZMOCP > 5%Co/AZMOCP > 5%Cu-5%Co/AZMOCP > 3%Co/AZMOCP. It was found that 2%Pd-5%Co/AZMOCP resulted in complete conversion of HMF with 97% yield of DMF at 100 °C and 10 atm H2 pressure. The catalysts were characterized by sophisticated techniques such as FESEM, EDS, XRD, NH3-TPD, ATR-FTIR, BET analysis, HRTEM, TPR, XPS and TGA-DSC. The reaction mechanism was developed based on dual-site Langmuir-Hinshelwood-Hougen-Watson (LHHW) model. The catalyst was highly selective and reusable. The overall process is clean and green.