Stable Cu-Ni/SiO 2 catalysts prepared by using citric acid-assisted impregnation for vapor-phase hydrogenation of levulinic acid

Cu-Ni/SiO2 catalyst was developed by impregnation assisted with citric acid for the vapor-phase hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL). The prepared catalysts were characterized by using X-ray powder diffraction (XRD), transmission electron microscope (TEM), temperature-programed reduction, thermogravimetry analysis, and X-ray fluorescence analysis. The XRD analysis and the TEM observation of the catalyst samples indicate that the usage of citric acid in the preparation process of impregnation improved the dispersion of Cu and Ni metal on SiO2. A Cu-Ni/SiO2 catalyst with Cu loading of 4 wt.% and Ni of 16 wt.% showed the best performance in the hydrogenation of LA to GVL under ambient H2 pressure at a high weight hourly space velocity (WHSV) of 13.2 h−1 and 250 °C: the conversion was 98.2% and the GVL selectivity was 97.6%. The catalyst prepared by citric acid-assisted impregnation showed the resistance to catalyst deactivation.