Theoretical Development of the Composite Absorbent for Maleic Anhydride Production: Insights from COSMO-RS, VLE Experiments, and Process Simulation

Maleic anhydride, produced via n-butane oxidation, is typically selectively absorbed from the water-rich reaction gas stream by organic solvents, but the process is challenged by the inherent conflict between hydrophobicity of solvents and their affinity for maleic anhydride. Herein, a composite absorbent strategy was proposed based on the COSMO-RS model, vapor–liquid equilibrium experiments, and process simulation, demonstrating that the addition of 20 wt % sulfolane to dibutyl phthalate effectively balances hydrophobicity and absorption capacity. As a result, the absorbent consumption, desorption energy demand, and exergy loss were reduced by 40%, 27%, and 38%, respectively. Microscopic insights from σ-profiles and molecular surface electrostatic potential distribution maps revealed that the enhanced absorption capacity arises from an increased frequency of complementary polar interactions between solvents and solutes. The methodology holds broader implications for optimizing solvents in extractants and absorbents, particularly those acting on polar solute systems.