Highly efficient conversion of cellulose into 5-hydroxymethylfurfural using temperature-responsive ChnH5-nCeW12O40 (n=1-5) catalysts

The design of stable heteropolyacid (HPA) catalysts with strong Bronsted acidity and mild Lewis acidity is crucial for the efficient conversion of renewable biomass to value-added chemicals. Firstly, a novel strategy was proposed to synthesize the Ce-based HPA of H5CeW12O40. Secondly, the H5CeW12O40 was combined with ChCl to form a series of temperature-responsive HPA catalysts (Ch(n)H(5-n)CeW(12)O(40), n = 1-5), which allowed the catalysts to be applied as soluble catalysts at a temperature > 80 degrees C and be easily separated as an insoluble catalyst at a temperature < 80 degrees C. In the H2O/DMSO/MIBK biphasic system, one-pot production of 5-hydroxymethylfurfural (5-HMF) from cellulose was achieved with an excellent yield of 67.5% over ChH(4)CeW(12)O(40) catalysis at 140 degrees C for 6 h, and other carbohydrates were converted, including fructose (83.1%), glucose (74.2%), sucrose (75.8%), cellobiose (70.2%) and starch (68.7%). Such high efficiency was attributed to the homogeneous catalysis at high temperature, the strong Bronsted acidity of [H5-nCeW12O40](n-), and the appropriate Lewis acidity from Ce(III). Moreover, the temperature-responsive property and the high stability were beneficial for recycling without significant structural change and activity loss.