Conversion of ethyl levulinate to γ-valerolactone catalyzed by the new Zr-containing organic-inorganic hybrid catalysts

Abstract

Three novel heterogeneous Zr-containing organic–inorganic hybrid catalysts were prepared for the transfer hydrogenation of biomass-derived ethyl levulinate (EL) to γ-valerolactone (GVL) with isopropyl alcohol (IPA) as the hydrogen donor and were characterized by Fourier transform infrared (FT-IR), Temperature-programmed desorption (TPD), Thermogravimetry (TG), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). On their basis, the effects of temperature, time, the amount of catalyst, and the solvent were investigated on the yield of GVL. A GVL yield of 96.5% with 99% EL conversion was obtained using Zr-Pg, which was prepared by the reaction of ZrCl4 and phloroglucinol (Pg) in N,N-dimethylformamide (DMF) at room temperature. The high catalytic activity may be attributed to the strong basicity, which was increased by the sufficient quantity of phenate in the structure of Zr-Pg. Meanwhile, Zr-Pg could be efficiently and easily recycled at least five times without any notable loss of activity and selectivity. Through the results of comparative experiments and characterization, we propose a plausible reaction mechanism for the high activity of Zr-Pg.