Integrated production of furfural and second-generation bioethanol from Eucalyptus wood residues: experimental results and process simulation

In this study, furfural production in a two-stage system was investigated using Eucalyptus wood residues (pinchips) as raw material. Firstly, an autohydrolysis treatment at 170 °C was performed for 40 min to solubilise xylosaccharides from biomass. In a second stage with sulphuric acid, furfural production was evaluated at different temperatures (170–240 °C) and reaction times (2.5–30 min) with two acid concentrations (0.3 and 3.0% w/w). The maximum furfural yield achieved was 77.4% of the theoretical production, considering the solubilised xylosaccharides content in the autohydrolysis liquor. This condition was achieved at 210 °C for 10 min with a sulphuric acid concentration of 0.3% w/w. The biomass pretreatment was a two-stage pretreatment with the above autohydrolysis followed by a soda-pulping stage of the solid fraction at 155 °C and 7.8 atm for 90 min using a 2.4% w/w NaOH solution. These results were added to previous experimental results for bioethanol production by enzymatic hydrolysis and fermentation to develop the process design. A lignocellulosic biorefinery plant co-producing furfural (from the hemicellulosic fraction) and bioethanol (from the cellulosic fraction) was proposed and simulated using Aspen Plus® V11. According to the material balance results, the proposed plant processes 166 tonne/d of Eucalyptus pinchips, with a production capacity of 203 tonne/d of bioethanol and 35 tonne/d of furfural. Finally, 33.0 MW of hot and 15.2 MW of cold utilities are required for the proposed process according to the heat integration analysis.