A biochar catalyst with functional Brønsted–Lewis acid sites for enhancing hydroxymethylfurfural production from glucose

Abstract

The sustainable production of 5-hydroxymethylfurfural (HMF) from glucose remains a major challenge in advancing bio-based chemical platforms. Despite extensive research, achieving high HMF yields in environmentally friendly systems is hindered by the complexity of glucose conversion pathways. This study presents a novel bifunctional catalyst (B-TsFe), derived from cassava rhizome (CR) biochar and functionalized with Brønsted and Lewis acid sites. The catalyst design leverages the carbon-rich nature of CR, integrating p-toluenesulfonic acid (TsOH) and ferric chloride (FeCl<inf>3</inf>) to establish synergistic acid functionalities. Comprehensive characterization confirmed the presence of both acid site types and mesoporous structures conducive to catalytic activity. The catalyst's performance was evaluated in a water–isopropanol (iPrOH) biphasic system, achieving a maximum HMF yield of 34.5 wt.% under optimized conditions (200°C, 75 min, 3:2 iPrOH:H<inf>2</inf>O ratio). Furthermore, the catalyst maintained high activity over five reuse cycles with minimal loss in performance. Compared to conventional biochar-based catalysts, B-TsFe exhibits superior acidity, enhanced glucose conversion efficiency, and a lower environmental impact due to its renewable origin and green solvent system. This work offers an eco-efficient strategy for HMF synthesis, addressing key limitations in catalyst development and process sustainability.