Liquid-Liquid Equilibrium for the Esterification System of Acrylic Acid with n-Butanol Catalyzed by Ionic Liquid [BMIm][HSO4] at Atmospheric Pressure

n-Butyl acrylate (n-BA), one of the important chemicals in the resin industry, can be synthesized by esterification of acrylic acid (AA) and n-butanol (BuOH). Owing to the thermodynamic immiscibility of n-BA and water, reactive extraction is promising to intensify the esterification with a suitable solvent (e.g., ionic liquid, IL) through in situ shifting of the reaction equilibrium toward n-BA. Herein, a typical Bronsted acidic IL 1-butyl-3-methylimidazolium hydrogen sulfate ([BMIm]-[HSO4]) was employed to intensify the esterification process. The liquid-liquid equilibrium (LLE) of ternary systems {AA or BuOH + n-BA + [BMIm]-[HSO4]} and a quinary system {AA + BuOH + n-BA + water + [BMIm]-[HSO4]} was investigated at atmospheric pressure and temperatures T = 313.15, 333.15, and 353.15 K and T = 333.15, 343.15, and 353.15 K, respectively. According to experimental results, the solute distribution coefficient and solvent selectivity were tested to verify the thermodynamic feasibility of [BMIm] [HSO4] as a catalyst and an extractant for n-BA formation. In addition, the NRTL model was adopted to correlate the experimental data, and the binary interaction parameters for the esterification system were fitted.