Catalytic Transfer Hydrogenation of Ethyl Levulinate to γ-Valerolactone Over Ni Supported on Equilibrium Fluid-Catalytic-Cracking Catalysts

Abstract

Nickel supported on equilibrium fluid-catalytic-cracking catalysts (Ni/E-cats) were prepared by a simple grinding-pyrolysis method and employed for the transfer hydrogenation of ethyl levulinate (EL) to γ-valerolactone (GVL). 96.2% selectivity of GVL and 90.3% conversion of EL were obtained at 180 °C for 6 h over 30-Ni/E-cat. Through XRD, N2 adsorption–desorption, NH3-TPD and SEM analysis, the high activity of the 30-Ni/E-cat catalyst was attributed to its dispersed Ni metal active centers and available acidic sites. Catalytic probe test revealed that metal and acid sites of Ni/E-cat played a synergistic catalytic role in the synthesis of GVL in 2-propanol, where Ni metal sites contribute to the hydrogenation of ketone group in EL, and acid sites of E-cat promoted the lactonization of intermediate ethyl- or isopropyl 4-hydroxyvalerate. Two reaction pathways and synergistic mechanism were proposed in this catalytic system. Moreover, Ni/E-cat catalyst exhibited good stability up to four cycles without obvious loss of catalytic activity.