Title : Thermodynamic analysis of toluene–butanol separation under elevated pressure: A novel approach toward sustainable process design
Abstract:
Purpose: Toluene and butanol are widely used solvents in petrochemical, pharmaceutical, and chemical manufacturing industries. Their separation from azeotropic mixtures is challenging due to close boiling points and complex phase behavior. Additionally, their presence in industrial wastewater poses environmental risks, including water contamination and ecological damage.
Methods: This study utilized Aspen Plus software to simulate TXY equilibrium diagrams for the toluene–butanol mixture under various pressures (1, 2, 3, 5, and 7 atm). Thermodynamic models NRTL and UNIQUAC were applied to predict phase behavior. At 1 atm, the azeotropic point was identified at a mole fraction of 0.6495 for toluene and 0.3505 for butanol.
Results: As pressure increased, the boiling point difference between the two components diminished, and TXY curves converged. This phenomenon is attributed to reduced enthalpy of vaporization and enhanced intermolecular interactions at high pressure. The nonpolar aromatic structure of toluene and the polar hydroxyl group in butanol exhibit more similar phase behavior under elevated pressure, reducing separation efficiency.
Conclusion: Elevated pressure leads to convergence of thermodynamic properties and boiling points, rendering conventional distillation ineffective. Alternative separation techniques such as azeotropic distillation, solvent extraction, or membrane technologies are recommended. Environmental considerations should be integrated into process design to minimize solvent emissions.
Keywords: Azeotropic Separation, Toluene–Butanol Mixture, Pressure Effect, Aspen Plus Simulation, Environmental Impact
