Catalytic dehydration of sorbitol and fructose by acid-modified zirconium phosphate

Abstract

Zirconium phosphate, a typical metal phosphate material, is characteristic in the design of structures and active sites, which has received widespread attention as solid acid catalysts in biomass conversion. In this work, the acid-modified zirconium phosphate catalyst was synthesized and characterized by the methods of XRD, TGA, FT-IR, NH3-TPD, pyridine-adsorbed FT-IR, SEM, TEM and 31P MAS NMR. Subsequently, the as-obtained material has been employed for the dehydration of sorbitol and fructose, which can be converted into isosorbide (ca. 73.6% selectivity) and 5-hydroxymethylfurfural (ca. 73.4% selectivity), respectively under optimal reaction conditions. It was found that the modification of oleum enhanced both the amounts and strength of Brönsted and Lewis acidic sites, and also improved the dispersity by “exfoliating” zirconium phosphate, resulting in the formation of very thin nanosheets instead of original amorphous structure and thus exposing more active sites for catalytic reaction. These effects were favorable for improving the catalytic dehydration activity and selectivity of sorbitol and fructose significantly. Meantime, the acidic sites of the acid-modified zirconium phosphate catalyst is highly leaching-resistant in dehydration reaction and the catalyst can be recycled up to five times without any considerable loss of activity.