Liquid phase chemo-selective catalytic hydrogenation of furfural to furfuryl alcohol

Abstract

Novel Cu:Zn:Cr:Zr based catalysts were developed for the hydrogenation of furfural to furfuryl alcohol. Physio-chemical characterizations of the catalysts were performed by using XRD, BET, FTIR, TPR, NH₃-TPD, ICP-MS, SEM, TEM, CO-chemisorption, and XANES techniques. Among all the catalysts prepared, the catalysts Cu(3):Zn(2):Cr(1):Zr(3) and Cu(3):Zn(2):Cr(1):Zr(4), referred as Cat-C and Cat-D, respectively are the best ones to demonstrate high activity and selectivity profile. Cat-C and Cat-D exhibited 100% conversion and 96% selectivity at 170 ± 2 °C and 2 MPa of hydrogen pressure. The role of constituent metals in the catalyst was delineated. Incorporation of Zn increases the activity for furfural conversion whereas Zr contributes significantly to the selectivity of furfuryl alcohol. It was also found that Zr loading not only increases the acidity of the catalyst but also helps in the dispersion of metallic Cu. The particle size of metallic Cu was found to be in the range of 17–19 nm as confirmed by TEM, XRD and CO chemisorption techniques. XANES analysis confirmed the presence of copper in Cu⁰ and Cu²⁺ oxidation states in Cat-C (freshly reduced) and Cat-C (fresh), respectively. Hydrogenation of furfural to furfuryl alcohol follows a pseudo-first order reaction with an the apparent activation energy of 24.4 kcal/mol. Cat-C was recycled at least 4 times for the hydrogenation of furfural with no loss of activity and selectivity when compared to the fresh catalyst.