Enhancing the conversion of D-xylose into furfural at low temperatures using chloride salts as co-catalysts: Catalytic combination of AlCl₃ and formic acid

Furfural is a potential platform chemical derived from biomass, which has gained increased attention as a potential substitute for the displacement of petrochemicals and the production of biofuels. The catalytic effect of different metal tri-chlorides (FeCl₃, AlCl₃ and CrCl₃) with formic acid (FA) was investigated for the selective conversion of D-xylose to furfural in aqueous solutions. Reactions were carried out at various temperatures (100–170 °C), FA concentrations (0–65 wt%), and metal chloride concentrations (0.2–0.8 M). Lyxose was identified as primary intermediate of the conversion of xylose at low temperatures and FA concentrations. A mixture containing 0.4 M AlCl₃ and 55 wt% FA was the most selective and active system for the production of furfural at low temperatures (130 °C, selectivity ≈70–90%). A simplified kinetic model was developed to describe the overall xylose conversion and furfural formation under the selected conditions, offering a valuable tool for process optimisation and design.