Sequential and in situ extraction of furfural from reaction mixture and effect of extracting agents on furfural degradation

Furfural is a platform chemical that can be obtained from renewable resources. It can be produced by acid-catalyzed dehydration of xylose. Currently, the furfural yield is relatively low due to side reactions (degradation of furfural). The furfural yield can be improved by rapidly and continuous removal of the furfural from the reaction mixture (in-situ extraction), preventing further furfural degradation. In this work, the (in-situ) extraction of furfural from the reaction mixture using different organic solvents and hydrophobic deep eutectic solvents is investigated. First, the distribution coefficients of furfural in various organic solvents were determined. It was found that extracting agents containing phenol-groups showed the highest distribution ratios. Thereafter, the acid-catalyzed degradation of furfural in the presence of the different solvents was assessed. Addition of organic solvents or hydrophobic deep eutectic solvents resulted in a significant decrease in furfural degradation compared to the blank and the benchmark. Finally, in-situ extraction with the different extracting agents was performed. The xylose conversion was not influenced by solvent addition, whereas the furfural yields were significantly higher compared to the blank experiment, even when low amounts of extracting agents were applied. This was explained by the limited co-extraction of the acid to the organic phase, preventing further contact/reaction between the furfural and the acid. Hence, organic solvents and hydrophobic deep eutectic solvents can be promising in-situ extracting agents for the removal of furfural from biorefinery processes.