Carbon supported polyoxometalates as recyclable solid acid catalysts in aqueous reactions

Acidic Polyoxometalates have been identified as promising catalysts for the hydrolysis of lignocellulosic biomass. They possess a high Bronsted acidity but are soluble in water and most organic solvents, which impedes their recycling and thus industrial application. To develop a solid acid catalyst with both good activity and recyclability, phosphotungstic acid (PTA) was immobilized on activated carbon (AC) by equilibrium impregnation. Characterization of the catalyst materials revealed a stabilizing effect by oxygen functional groups on the support material by increasing the polarity of the support and enabling a chemical interaction between the heteropolyacid and the surface. PTA/AC was applied in the hydrolysis of the hemicellulose xylan as an aqueous model reaction, selectively yielding the biorefinery platform compound xylose with up to 74 % yield. The catalyst can be easily separated from the reaction system and possesses good reusability over 20 recycling runs with a low constant leaching of 3-4 % per run.

Automated summary

A solid acid catalyst with good activity and recyclability was developed by immobilizing phosphotungstic acid on activated carbon. It selectively produced xylose in the hydrolysis of lignocellulosic biomass model reaction, and could be easily separated and reused.