Mesoporous tantalum oxide as catalyst for dehydration of glucose to 5-hydroxymethylfurfural

Mesoporous tantalum oxide was prepared by acid hydrolysis of tantalum penta-ethoxide in the presence of a triblock co-polymer Pluronic L-121, a non-ionic surfactant, at room temperature and subsequent calcination at 550 degrees C for 6 h. This solid exhibits a suitable specific surface area (79 m(2) g(-1)) and a high acidity (353 mu mol NH3 g(-1)) with the presence of both Bronsted and Lewis acid sites, demonstrating to be active as solid acid catalyst in the dehydration of glucose to 5-hydroxymethylfurfural (HMF), in a biphasic water/methyl-iso-butyl ketone (MIBK) system. Thus, by using a glucose:catalyst weight ratio of 3:1, a glucose conversion of 69% and a HMF yield of 23% were achieved at 175 degrees C, and after only 90 min of reaction time. The catalytic process is selective toward HMF, which is preserved from ulterior hydration to levulinic acid. Fructose was also detected as by-product of glucose isomerisation with 14% of selectivity. The catalyst is very stable, since no leaching of tantalum species to the liquid phase was found; moreover, the catalytic performance of this acid solid is well recovered after calcination at 550 degrees C for 2 h. (c) 2014 Elsevier B.V. All rights reserved.