Optimization of furfural production from d-xylose with formic acid as catalyst in a reactive extraction system

Furfural is one of the most promising platform chemicals derived from biomass. In this study, response surface methodology (RSM) was utilized to determine four important parameters including reaction temperature (170–210 °C), formic acid concentration (5–25 g/L), o-nitrotoluene volume percentage (20–80 vt.%), and residence time (40–200 min). The maximum furfural yield of 74% and selectivity of 86% were achieved at 190 °C for 20 g/L formic acid concentration and 75 vt.% o-nitrotoluene by 75 min. The high boiling solvent, o-nitrotoluene, was recommended as extraction solvent in a reactive extraction system to obtain high furfural yield and reduce furfural-solvent separation costs. Although the addition of halides to the xylose solutions enhanced the furfural yield and selectivity, the concentration of halides was not an important factor on the furfural yield and selectivity.