Selective hydrogenation of γ-valerolactone to 1,4-pentanediol over hydrotalcite-derived CuCoAl catalysts

In this study, a series of CuCoAl catalysts with different Cu/Co molar ratios were prepared from hydrotalcite-like precursors and then adopted for γ-valerolactone (GVL) hydrogenation to 1,4-pentanediol (1,4-PeD). By tuning the Cu/Co ratio in the CuCoAl catalysts and optimizing the reaction conditions, nearly 100% yield of 1,4-PeD was finally achieved with the Cu0.2Co0.8Al catalyst (Cu/Co = 1: 4) at 433 K and 4 MPa H2. The high activity of the Cu0.2Co0.8Al catalyst was attributed to the existence of Cu-CoOx synergistic active sites and the abundant surface acidity. The electron transfer from Cu to Co resulted in the formation oxygen-defected CoOx sites and surface acidic sites, which were beneficial for the adsorption of GVL and the activation of C-O/C=O bonds. The proximity between Cu particles and defective CoOx facilitated the dissociative adsorption of H2 on Cu0 and the subsequent hydrogen spillover to CoOx sites, thereby significantly promoted the selective hydrogenation of GVL to 1,4-PeD. In addition, applications of the Cu0.2Co0.8Al catalyst to the ring-opening reactions of other lactones (including α-adamyllactone, γ-caprolactone, δ-pentyllactone, and ε-caprolactone) were further investigated. Eventually, high yields (> 93%) of the corresponding diols were attained, demonstrating the excellent catalytic versatility of Cu0.2Co0.8Al in selective hydrogenation of lactones. Overall, this work shows high potential of hydrotalcite-derived CuCoAl catalysts for selective hydrogenation of GVL to 1,4-PeD, and provides insights for the design of efficient bimetallic catalysts in lactone hydrogenolysis.