Enhancement of furfural formation from C5 carbohydrates by NaCl in a green reaction system of CO2–water–isopropanol

A novel green reaction system of CO2-water-isopropanol has been developed for the production of furfural (FF) from xylose. Initially, a simple CO2-water system was investigated, and the results showed that the formation of FF from xylose was greatly enhanced. CO2 at high pressure could increase the acidity of the reaction system, and thus the FF yield was improved. By raising the reaction temperature, the conversion of xylose was remarkably accelerated in the CO2-water-isopropanol system, leading to an acceptable conversion rate (94.41%) and FF yield (55.81%). Addition of an appropriate amount of NaCl further increased the yield to 69.20%. Other carbohydrates (arabinose and xylan) were also tested in the same reaction system and modest results were obtained.