Conversion of xylose into furfural over MC-SnOx and NaCl catalysts in a biphasic system

Furfural is a promising platform chemical that can be catalyzed from lignocellulose biomass. In this study, a novel micro-mesoporous carbon supported tin oxide catalyst (MC-SnOx) was developed to convert xylose into furfural in a low sodium chloride (NaCl) concentration and acid-free biphasic system. The catalysts synthesized by annealing from 400 °C to 600 °C for 3.5h were characterized by BET, SEM, XPS, XRD, NH3-TPD and FTIR techniques. The factor that mostly affected the catalytic performance was the acid concentration of the catalysts, and the best catalytic performance was achieved by MC-SnOx annealed at 450 °C. Further increasing the annealing temperature can cause reduction, volatilization and aggregation of Sn species, which can finally affect acid concentration and performance of the catalyst. In addition, a synergistic catalytic effect was found between MC-SnOx and NaCl and effectivity of low concentration of NaCl indicated the potential of applying seawater or wastewater containing NaCl as a low-cost reaction solvent and NaCl source. To balance the catalytic performance, cost, equipment safety and environmental concerns, a reasonable furfural yield of 53.9% was achieved over the MC-SnOx-450 and NaCl (0.2 M) in biphasic system under mild conditions (180 °C and 20 min) with a good catalyst reusability.