In-situ stripping by water-ethanol steam improves continuous conversion of corncob hydrolysate to furfural

Furfural is an important biomass-derived furanic platform chemical that has been produced on an industrial scale. Conventional batch processes suffer from low yield, numerous by-products, and high energy consumption. Herein, a continuous countercurrent blowing strategy using superheated water-ethanol mixed steam is proposed to directly convert the acid hydrolysis mixture of corncob (containing pentose and hydrolysis residue) into furfural. By utilizing superheated steam for synchronous dehydration and stripping, a furfural yield of 61.8% with selectivity > 70% is achieved at 180 °C, a relative saturation of 26.37%, and an initial sulfuric acid concentration of 3.0 wt%. The introduction of 10 vol% ethanol reduces the heat transfer resistance of the liquid film, increases the surface acid concentration, stabilizes carbocation intermediates, and accelerates the gas-phase migration of furfural, further increasing the furfural selectivity to 80.7%. During continuous operation for 12  h, the yield stabilizes at 55-60%, the residual aldehyde content in the residue is below 0.01%, and steam consumption is reduced by 20%. Techno-economic analysis shows that compared with the conventional batch process, the total production cost of the proposed process is reduced by 26.7% and the revenue is increased by 5.2%. Life cycle assessment indicates that all environmental impact categories are reduced by about 30%, with a 27.2% decrease in carbon footprint. This continuous process requires no additional organic solvents or ionic liquids, is based on the well-established dilute sulfuric acid hydrolysis system, and has excellent potential for industrial scale-up.