Azeotropic formic acid-water separation by sulfolane extractive distillation feasibility study

Due to the formation of an azeotrope at 57.6 mol.% formic acid under atmospheric pressure, conventional distillation is ineffective for separating formic acid and water into pure components. This study explores the use of extractive distillation with sulfolane as a solvent to overcome this limitation. The binary interaction parameters for the formic acid-water and sulfolane-water systems were determined using the NRTL model in Aspen Plus V10 software, based on experimental data. The investigation focuses on the effect of varying solvent concentrations on the thermodynamic equilibrium and the relative volatility of water to formic acid. The proposed process design incorporates two sequential columns: an extractive distillation column and a solvent regeneration column, both operating under reduced pressure. Simulation results confirm the feasibility of this method for purifying formic acid. For water concentrations between 80% and 50%, the boiler energy consumption in the extractive distillation process decreases by 42%. The regeneration column operates at 0.254 bar to minimise corrosion and ensure complete recovery of sulfolane. This study highlights the effectiveness of extractive distillation with sulfolane, achieving a high recovery rate of nearly pure formic acid.