One-pot cascade process for efficient upgrading of furfural to γ-valerolactone over adjustable Lewis-Brønsted bi-acidic catalyst

A series of zirconium phosphate (ZrP) loaded H-beta-25 zeolite (i.e., ZrP@HB) multifunctional composite catalysts were synthesized by a simple co-precipitation method, and the one-pot upgrading for the transfer hydrogenation of furfural to γ-valerolactone (GVL) was systematically investigated through various characterizations and catalytic evaluation experiments. Comparative characterization analysis of the ZrP@HB-X(Y) catalysts showed that the ZrP@HB-4(4) catalyst has uniform distribution of elements, exhibiting a large specific surface area and hierarchical mesoporous/microporous structure. Fourier transform infrared spectroscopy of pyridine (Py-FTIR) and NH3 temperature-programmed desorption characterizations indicated the presence of Lewis and Brønsted acid sites, as well as weak, moderate, and strong acid sites in the ZrP@HB-4(4) catalyst. It was confirmed by X-ray photoelectron spectroscopy and FTIR that the main reason for Lewis and Brønsted acid sites formation is the presence of P-O-Zr, P-O-H, and HB zeolite on the ZrP@HB-4(4) catalyst. The HB zeolite as well as Zr and P ratio, can be easily adjusted to efficiently regulate the acidity strength and Lewis and Brønsted acid sites of the ZrP@HB-X(Y) catalysts. The catalytic experiments demonstrated that the physicochemical properties of the ZrP@HB-4(4) catalyst mentioned above significantly enhance the GVL production. Notably, Lewis and Brønsted acid sites as well as transition metal sites of Zr in the ZrP@HB-4(4) catalyst were identified as the main factors that enhance the yield of the target product. By optimizing the reaction conditions, the yield of GVL could be as high as 88.16%. Reusability experiments demonstrate that the ZrP@HB-4(4) catalyst possesses excellent stability. Using levulinic acid as the substrate, the yield of GVL reached 93.92%, suggesting its potential versatility.