Integrated supercritical carbon dioxide extraction for efficient furfural production from xylose using formic acid as a catalyst

This study investigates the production of furfural via formic acid-catalyzed dehydration of xylose and the effect of simultaneous extraction of furfural using supercritical carbon dioxide (Sc-CO2). The addition of Sc-CO2 results in a secondary reaction pathway comprised of two steps: CO2-catalyzed isomerization of xylose into the reactive intermediate xylulose, followed by furfural production from xylulose, catalyzed by formic acid. Xylose dehydration with CO2 in both batch and semi-batch systems yielded a higher furfural yield and selectivity compared with systems without CO2. The Sc-CO2 extraction in a semi-batch system prevents furfural degradation by maintaining high productivity, even with increased initial xylose concentration. A maximum furfural yield of 68.5% (71.4% selectivity and 99% separation efficiency) was achieved after 5 h at 140 degrees C and 20 MPa with a constant flow rate of 5 g/min of CO2 and initial concentrations of 10 g/L of xylose and 10 wt% of formic acid.