Synergistic effect between CaCl2 and Γ-Al2O3 for furfural production by dehydration of hemicellulosic carbohydrates

Article abstract of DOI:10.1016/j.apcata.2019.117188

γ-Al₂O₃ has successfully been used as solid acid catalyst for xylose dehydration in a water:toluene biphasic system. The addition of alkaline earth metal chlorides improved the partition coefficient, thus facilitating the extraction of furfural from the aqueous phase. In this sense, the best catalytic performance was attained by using CaCl₂ and γ-Al₂O₃ with almost full xylose conversion and a furfural yield of 55% after 50 min, at 150 °C. A ¹H NMR study has demonstrated that CaCl₂ shifts the α-xylopyranose/β-xylopyranose anomeric equilibrium toward the α-form, more favorable for initiating the dehydration process, and γ-Al₂O₃ promotes the furfural production. γ-Al₂O₃ can be reused during ten catalytic cycles without any pretreatment. Finally, the synergistic effect between CaCl₂ and γ-Al₂O₃ could also be inferred from the increase in furfural yield, until a value of 83% after 50 min at 175 °C, by using a hemicellulosic liquor obtained from olive stones.