Solvent-Free Production of Isosorbide from Sorbitol Catalyzed by a Polymeric Solid Acid
Graphical Hard graft : A series of polymeric solid acid catalysts (PDSF- x ) is prepared by grafting strong electron-withdrawing groups (−SO 2 CF 3 ) on a sulfonic acid-modified polydivinylbenzene (PDS) precursor. The effect of acid strength on sorbitol dehydration is investigated. A series of polymeric solid acid catalysts (PDSF- x ) is prepared by grafting strong electron-withdrawing groups (−SO 2 CF 3 ) on a sulfonic acid-modified polydivinylbenzene (PDS) precursor synthesized hydrothermally. The effect of acid strength on sorbitol dehydration is investigated. The textural properties, acidity, and hydrophobicity are characterized by using Brunauer–Emmett–Teller analysis, elemental analysis, and contact angle tests. The results of FTIR spectroscopy and X-ray photoelectron spectroscopy show that both −SO 3 H and −SO 2 CF 3 are grafted onto the polymer network. We used solid-state 31 P NMR spectroscopy to show that the acid strength of PDSF- x is enhanced significantly compared with that of PDS, especially for PDSF-0.05. As a result, PDSF-0.05 exhibits the highest isosorbide yield up to 80 %, a good turnover frequency of 231.5 h −1 (compared to other catalysts), and excellent cyclic stability, which is attributed to its large specific surface area, appropriate acid strength, hydrophobicity, and stable framework structure. In addition, a plausible reaction pathway and kinetic analysis are proposed.
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