Preparation of the Nb-P/SBA-15 catalyst and its performance in the dehydration of fructose to 5-hydroxymethylfurfural

Dehydration of fructose to 5-hydroxymethylfurfural (5-HMF) is one of the pivotal reactions in conversion of biomass towards valuable platform compounds. In this work, Nb/SBA-15 was prepared via incipient wetness impregnation with self-made SBA-15 as support; Nb/SBA-15 was further treated with phosphoric acid and calcined at 450℃, to obtain the Nb-P/SBA-15 catalyst. The Nb-P/SBA-15 catalyst was characterized by SEM, TEM, BET, XRD and NH₃-TPD; its performance in the dehydration of fructose to 5-HMF was then investigated. The results indicate that the microscopic structure of SBA-15 is well preserved in Nb/SBA-15 with an internal channel diameter of about 10 nm and the niobic species are highly dispersed on the surface of the channels; the wall of channels became thinner after impregnation of Nb and treatment with phosphoric acid. After the treatment with phosphoric acid, the weak acid sites are increased, moreover, the medium and strong acidic sites are generated in Nb-P/SBA-15; as a result, for the dehydration of fructose in a water/MIBK biphasic system, Nb-P/SBA-15 exhibits higher catalytic activity and selectivity to 5-HMF. By reaction at 160℃ for 1.5 h, with a water/MIBK volume ratio of 1/2, the conversion of fructose and the yield of 5-HMF reach 96.1% and 92.6%, respectively. Moreover, the Nb-P/SBA-15 catalyst also exhibits excellent stability in view of water tolerance; it still demonstrates high catalytic activity and selectivity to 5-HMF even after successive recycling for four times.