Catalytic hydrogenation of furfural to furfuryl alcohol over chromium-free catalyst: Enhanced selectivity in the presence of solvent

Copper chromite (Cr2CuO4) catalyst is commercially being used for hydrogenation of furfural (FAL) to furfuryl alcohol (FA). However, due to the negative environmental impact of chromium, the use of a chromium-free catalyst has become a logical choice. In order to develop Cr-free catalysts, several Cu-Zn-X-Y [X and Y = additives] based trimetallic and tetrametallic catalysts were synthesized and tested for selective hydrogenation of furfural to furfuryl alcohol in different solvents. The characterization of catalysts using XRD, N-2 sorption, H-2-TPR, and HRTEM reveals the synergetic effect between CuO and ZnO interface. Interestingly, the strong influence of solvents was observed on the catalytic activity and selectivity. The positive influence of the solvent on enhancing selectivity was associated with the hydrogen bond donation (HBD) and hydrogen bond acceptance (HBA) capability. Water, a green solvent, has been found the most effective solvent. The high hydrogen bond donor capability of water was responsible for the strong positive effect. The effect of parameters, such as H-2 pressure, catalyst loading, furfural concentration, temperature, and reaction time, was studied on catalyst performance. Excellent selectivity for furfuryl alcohol >= 99% was obtained at mild operating conditions of temperature of 100 degrees C and H-2 pressure of 1 MPa. The kinetic study revealed that the furfural conversion profile was well fitted by the first-order kinetic model. The best CZAl catalyst showed reproducible activity up to 5 cycles.