Hydrothermally stable Nb-SBA-15 catalysts applied in carbohydrate conversion to 5-hydroxymethyl furfural.

[Display omitted] • Acidity adjustable Nb-SBA-15 with 2D hexagonal-ordered structure was synthesized. • Nb-SBA-15 is an high effective catalyst for the production of HMF from carbohydrate. • Nb-SBA-15 performs good hydrothermal stability in glucose conversion. • Nb species in SBA-15 framework and the mononuclear NbO 4 are the main active sites. 5-hydroxymethyl furfural (HMF) is a bio-based platform chemical with high potential. The as-synthesized Nb-SBA-15 catalysts with mesoporous structures showed high catalytic performance for the conversion of carbohydrates to HMF in a "one-pot" process using biphasic conditions of THF/H 2 O-NaCl as the solvents. Nb-SBA-15 catalysts with different Si/Nb ratios were characterized by analytical techniques such as XRD, elemental analysis, SEM, TEM, N 2 adsorption, NH 3 -TPD UV–vis DRS, Raman and Pyridine-FTIR. It was found that the acidity of Nb-SBA-15 catalysts could be tuned by modifying addition amount of niobium. The effects of reaction conditions, including temperature, time, and catalyst loading, on the conversions of carbohydrates and the yields of HMF were also investigated. The studies showed that Nb-SBA-15-40 catalysts which Si/Nb ratio is 40 gave the best yields of HMF due that Nb-SBA-15-40 had more niobium species in the SBA-15 silica framework and the mononuclear tetrahedral NbO 4. Under the optimized conditions, the yield of HMF could reach 61.8% at 93.5% glucose conversion and 50.7% at 94.0% cellulose conversion, respectively. Moreover, its catalytic performance was largely retained after 10 recycles in glucose conversion reaction vindicating its good catalytic stability. [ABSTRACT FROM AUTHOR]