Surface Synergetic Effects of Ni-ReOx for Promoting the Mild Hydrogenation of Furfural to Tetrahydrofurfuryl Alcohol

Ni-ReOx bimetallic catalysts (Ni-ReOx/TiO2) were prepared through a successive impregnation method, which is extremely active in furfural (FAL) hydrogenation to tetrahydrofurfuryl alcohol (THFOL) under mild reaction conditions. For instance, high FAL initial reaction rate (439.4 mmol/g-Ni/h) and THFOL formation rate (80.4 mmol/g-Ni/h) were achieved over Ni-5ReO(x)/TiO2, which are 13.2 and 6.6 times higher than those of Ni/TiO2, respectively. The unique catalyst reactivity derives from rich Lewis acidic ReOx and intimate electron interaction of ReOx with Ni NPs. Kinetic studies reveal that ReOx decoration decreases the activation barrier of -C=O hydrogenation other than the furan ring. Mechanism studies show that ReOx has a good affinity for C=O and H-2 and favors hydrogen spillover and C=O bond activation on Ni, thus reinforcing the synergistic effect of Ni and ReOx. This catalyst is versatile for various furan aldehydes and is relatively stable for 5 times recycling, showing relative potential for industrial application.