Isosorbide, a bicyclic C6 diol produced via successive cyclodehydrations of D-sorbitol, has received recent attention for its utility in the production of sustainable, bio-derived polymers. Large-scale production of isosorbide requires homogenous acid catalysts, commonly H<sub>2</sub>SO<sub>4</sub>, which create harmful acidic waste and complicate separation. Therefore, a heterogenous acid catalyst capable of producing isosorbide from sorbitol in high yield under mild conditions is desirable. Neat, liquid-phase dehydration was investigated over sulfated zirconia (SZ) solid acid catalysts produced via sol-gel synthesis. The catalyst preparation methodology allows for precise particle morphology and tunable catalytic activity. The S/Zr ratio (0.1-2.0) and calcination temperature (425-625°C) were varied to better understand their effect on crystalline phase, acidity and resulting reactivity. The SZ catalyst synthesized with S/Zr ratio of 0.5 and calcined at 425°C achieved isosorbide yield of 77% under ambient, mild conditions due to high concentration of strong acid sites while effectively suppressing side reactions that lead to the formation of humins. Detailed kinetic analyses were conducted to enable a better understanding of the relative rates of reaction, reaction networks, catalyst descriptors, and to determine activation parameters.

Successive cyclodehydration of sorbitol to isosorbide using a tunable, sulfated zirconia acid catalyst

ACS Spring 2022

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