Catalytic dehydration of sorbitol to isosorbide over sulfonated phenolic resins with surface hydrophobic modification

In this work, soluble and low-molecular-weight phenolic resol was cross-linking solidified by a solvothermal method using hexamethylenetetramine as a curing agent, which was modified with hydrophobic functional groups and sulfonated by chlorosulfonic acid. Modified and sulfonated phenolic resins were used as catalysts for the dehydration of sorbitol to isosorbide, and the effects of surface hydrophobicity, acid type and acid amount on sorbitol conversion and isosorbide yield were investigated systematically. The results showed that the introduction of 3-MPTMS by coupling with phenolic hydroxyl groups of phenolic resins can significantly enhance the surface hydrophobicity of sulfonated phenolic resins and increase the surface acid amount by the oxidation of thiol groups in 3-MPTMS using H2O2 to sulfonic acid groups. As a result, the catalytic performance of sulfonated phenolic resins with surface hydrophobicity modification was improved obviously; about 100% sorbitol conversion and 75.44% isosorbide yield could be achieved under optimal reaction conditions. Compared to commercial acid resins, sulfonated phenolic resins offer the advantages of lower cost and a more convenient preparation process. Sulfonated phenolic resins with excellent catalytic properties for dehydration of sorbitol to isosorbide were constructed.