H₃PW₁₂O₄₀/SiO₂ for sorbitol dehydration to isosorbide: High efficient and reusable solid acid catalyst

Tungstophosphoric acids (PW) supported on various metal oxides (SiO₂, γ-Al₂O₃, TiO₂, ZrO₂ and CeO₂) were synthesized and used as catalysts for sorbitol dehydration to isosorbide for the first time. 30% PW/SiO₂ exhibited the best catalytic performance for sorbitol dehydration, over which 56% isosorbide selectivity could be gained at a 95% sorbitol conversion at 250 °C. The catalytic performance of regenerated 30% PW/SiO₂ catalysts by dichloromethane elution showed no loss after recycling five runs. Characterizations with UV-Vis, XRD, NH₃-TPD and thermal analysis techniques revealed that PW had a good dispersion, and the primary Keggin structure was preserved after supporting PW on different supports. The interaction between PW and oxides resulted in different acidity of catalysts, which affected conversion of sorbitol and selectivity for isosorbide. The final acidity order of supported PW catalysts was the following: SiO₂<γ-Al₂O₃<TiO₂ ≈ ZrO₂<CeO₂.