• High yield of HMF (30.9 %) is achieved by 1 %Nb 2 O 5 -ZrO 2 -TiO 2 (1 % Nb-ZrTi) catalyst. • The lowest Brønsted to Lewis acid sites ratio of 1 % Nb-ZrTi promotes HMF formation. • The catalyst has excellent stability and is hardly deactivated after six cycles. 5-Hydroxymethylfurfural (HMF) is an attractive platform compound derived from lignocellulosic biomass. In order to convert cellulose into HMF in a single pot, a variety of Nb-based metal oxides produced using the co-precipitation-impregnation technique are employed as catalysts. Using 1% Nb 2 O 5 -ZrO 2 -TiO 2 (1% Nb-ZrTi) catalysts, an HMF yield of up to 30.9% is achieved at 190 °C for 8 h. Furthermore, the conversion behaviors of potential key intermediates (fructose and glucose) are explored to provide indirect evidence of the complete reaction pathway. To investigate the structure-activity relationship of the Nb-based catalysts, characterization techniques such as pyridine-adsorbed Fourier transform infrared spectrometer (Py-FTIR), ammonia temperature-programmed desorption (NH 3 -TPD), high-resolution transmission electron microscopy (HR-TEM), and X-ray diffraction (XRD) are employed. It is discovered that the lowest total acid concentration and the lowest Brønsted to Lewis acid sites (B/L) ratios of 1% Nb-ZrTi are associated with its exceptional catalytic activity. Furthermore, after six cycles, the catalyst still demonstrates good recyclability and catalytic activity. These findings give new directions for future catalyst improvement and process development.
Wang et al. (Sat,) studied this question.