No 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 ZrCl 4 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. K E Y W O R D Sethyl levulinate, hydrogen donor, transfer hydrogenation, Zr-Pg, γ-valerolactone

Catalytic transfer hydrogenation (CTH) of ethyl levulinate (EL) to γ‐valerolactone (GVL) is an alluring reaction in the field of biomass catalytic conversion, but it normally depends on the consumption of H2. In this study, we report a porous Zr‐containing inorganic pyrophosphate catalyst (ZrOPP), which was used as a catalyst for CTH of EL to GVL in the presence of isopropanol and characterized using FT‐IR, py‐FTIR, TGA, XRD, BET, XPS, ICP‐AES, SEM, TEM, NH3‐TPD, and CO2‐TPD. We achieved a high yield of 94% GVL at 433 K for 11 hr. Furthermore, the ZrOPP has the trait of easy separation and could be reused more than five times without distinct decrease in activity and selectivity. In addition, this catalyst could also be applied to other catalytic hydrogenation reactions, such as those of cyclohexanone, acetophenone, 2‐heptanone etc. Its outstanding performance was mainly ascribed to the acid sites from the Zr element and basic sites from phosphate groups interspersing on the surface of the catalyst.

Organic hybrid zirconium phosphonate materials (ZrATMP, ZrEDTMPS, ZrDTPMPA, and ZrHEDP) were synthesized through reaction of organic phosphonic acid sodium salt and ZrOCl 2 in water, which exhibited high catalytic activity on the conversion of ethyl levulinate (EL) to γ-valerolactone (GVL) in the presence of isopropanol. The obtained catalysts were characterized by FT-IR, TGA, XRD, BET, XPS, ICP-AES, SEM, TEM, NH 3 -TPD, and CO 2 -TPD. The results demonstrate that the number of acid sites and basic sites between the layers of the catalysts play a very important role in promoting the conversion of EL to GVL and that the functional groups that exist in phosphates could regulate the number of acid and basic sites. Meanwhile, the catalysts could be easily separated from the reaction system and reused at least five times without any obvious decrease in activity or selectivity.