Dehydration of sorbitol to isosorbide over sulfonic acid resins under solvent-free conditions

Abstract

Different commercial sulfonic acid resins (Purolite and Amberlyst type) have been evaluated as acid catalysts for the dehydration of sorbitol to isosorbide. These acidic resins differ in their acid properties, as well as in their thermal and mechanical stabilities. Dehydration of sorbitol has been carried out under solvent-free conditions, by melting sorbitol. At the beginning of reaction, different sorbitans (monodehydration products) were detected, whose dehydration and subsequent cyclization lead to the formation of isosorbide. A maximum yield of 75% is reached after 12h at 413K, by using a 5wt% of Purolite CT269, at atmospheric pressure. This resin maintains its catalytic activity after four runs, and the stability is corroborated by the negligible presence of sulphur species (coming from sulfonic acid leaching) in the reaction medium. This suitable catalytic performance can be explained by its high acid capacity (5.2meqg−1) and mechanical and thermal stabilities associated to the macroreticular structure.