Synthesis of Sulfated Sn–Zr Mesoporous Catalysts for the Selective Dehydration of Hexose‐Type Monosaccharides

Synthesis of combined Brønsted and Lewis acid sites in SBA‐15 by Zr and Sn incorporation onto the mesoporous support, followed by a sulfation procedure to get enhanced acid catalysts for fructose‐to‐5‐hydroxymethylfurfural (HMF) selective dehydration, is here studied. Different preparation methods are used to attain the Sulfated Sn–Zr–SBA‐15 material with adequate combination of Brönsted and Lewis acidity. Samples are characterized by using different analytical and spectroscopic techniques, results indicating a correlation between the preparation procedure and the acid characteristics of the materials. The latter are evaluated in the catalytic conversion of concentrated fructose solutions (30 wt%) into HMF in a biphasic system (water + iso‐butylketone/2‐butanol). The most efficient catalyst, SO 4 /Sn–Zr–SBA‐15 (Zr/Sn molar ratio = 1.98), yields ≥ 70% HMF at a substrate conversion of ≈90% under optimal reaction conditions (150 °C for 120 min.), these results being particularly relevant when considering the higher initial fructose concentrations here used compared to those typically employed in previous reports. This catalyst exhibits a higher ratio of Bronsted/Lewis (B//L) acid sites of moderate strength and a lower density of acid sites compared to the other catalytic samples evaluated, mainly due to the presence of well‐dispersed tin and zirconium species, as well as to the enhanced acidic properties provided by sulfate groups in the material.