Efficient conversion of carbohydrates into levulinic acid over chromium modified niobium phosphate catalyst

Abstract

In this work, a series of mesoporous niobium phosphate material with different Cr content (Cr/NbP) were synthesized and used as catalysts for glucose conversion to levulinic acid (LA). The results showed that the acidic properties of the material, including acid density, acid amount, and type of acid sites, had the important effects on glucose conversion. And the doping of Cr into niobium phosphate enhanced the catalyst acid amount, especially for Lewis acid amount, which finally resulted in the increase of LA yield through glucose-fructose isomerization. The effect of various reaction parameters such as temperature, time, catalyst dosage, and substrate concentration on LA generation have been optimized, and among the testing, 5%Cr/NbP catalyst exhibited the highest catalytic performance with 62.4 mol% LA yield obtaining from 100 mol% glucose conversion at 180 °C for 180 min. Besides, the synthesized Cr/NbP also displayed high activity for disaccharide or polysaccharide conversion to LA. The recycling of Cr/NbP manifested that the material can be reused at least for four times with the activity loss less than 10.0 mol%. The experiments results demonstrated the potential of Cr/NbP catalyst for carbohydrates conversion to LA in aqueous media under mild process conditions.