| Summary: | Catalytic conversion of fructose to levulinic and formic acids over tin-containing superacid (<i>H</i><sub>0</sub> = −14.52) mixed oxide was studied. Mesoporous ZrO<sub>2</sub>–SiO<sub>2</sub>–SnO<sub>2</sub> (Zr:Si:Sn = 1:2:0.4) was synthesized by the sol–gel method. The fructose transformation was carried out in a rotated autoclave at 160–190 °C for 1–5 h using a 20 wt.% aqueous solution. The results showed that doping ZrO<sub>2</sub>–SiO<sub>2</sub> samples with Sn<sup>4+</sup> ions improved both fructose conversion and selectivity toward levulinic and formic acids. Under optimal conditions of 180 °C, 3.5 h and fructose to catalyst weight ratio 20:1, levulinic and formic acids yields were 80% and 90%, respectively, at complete fructose conversion. At this, humic substances formed in the quantity of 10 wt.% based on the target products.
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