Soluble and reusable polymer-based catalysts with Brønsted and Lewis acidity for the one-pot synthesis of hydroxymethylfurfural from glucose

Abstract

Hydroxymethylfurfural (HMF) is an interesting renewable platform molecule due to the number of products that can be obtained from it. Various catalytic systems have been used to produce HMF from glucose; however, challenges, such as the lack of recovery and reutilization and/or low catalytic activity, have been encountered. This article reports a series of novel polystyrene sulfonic acid (PSSA)-based catalysts with both Brønsted and Lewis acid sites for the one-pot synthesis of HMF from glucose. These catalysts combine the advantages of both homogeneous and heterogeneous catalysts, as they are soluble in water (highly active) and recoverable by ultrafiltration for further use. Due to the presence of Brønsted and Lewis acid sites, these catalysts have the ability to perform both the isomerization of glucose to fructose and the dehydration of fructose to HMF. The interplay between Brønsted and Lewis acid sites was investigated by synthesizing a series of PSSA–AlCl₃ catalysts with different Brønsted : Lewis acid ratios. A maximum HMF yield of ∼55 mol% was obtained with the PSSA–AlCl₃ catalyst with H⁺/Al mole ratio = 4 after 4 h of reaction, and this was recycled and reused up to five times without significant loss of activity. Remarkably, this catalyst was effective in the valorization of highly concentrated solutions of glucose in water (up to 16.7 wt%). A techno-economic analysis estimated that the minimum fuel selling price (MFSP) of this HMF would be $1.94 per kg at a feed price of $0.30 per kg glucose. This MFSP could be further reduced by improving the HMF yield, minimizing the volume of solvent used, or using a lower-cost feedstock.