Phosphoric Acid Modified Nb2O5: A Selective and Reusable Catalyst for Dehydration of Sorbitol to Isosorbide

Niobium oxide (Nb2O5) and phosphated Nb2O5 were synthesized and used as catalysts for sorbitol dehydration to isosorbide. The characterization results of N-2 adsorption, XRD and NH3-TPD revealed that the phosphoric acid modification could well prevent the crystallization of Nb2O5. And the amorphous phosphated Nb2O5 catalysts kept the relatively large surface area and stable acidity at high calcination temperature. The catalytic results showed that the selectivity to isosorbide could be dramatically enhanced over phosphated Nb2O5. The excellent catalytic performance with 100.0% sorbitol conversion and 62.5% isosorbide selectivity were obtained over the 0.8P/NBO-400 catalyst. Comparing with Nb2O5 catalysts, phosphated Nb2O5 catalysts regenerated through a simple calcination process showed no significant activity loss after recycling three runs.