Energy-saving research on the separation of isopropyl acetate and isopropanol azeotrope using pressure-swing distillation based on phase equilibrium

Abstract

In high purity thioglycolic acid production, isopropyl acetate is used to extract the acid from intermediates, but it hydrolyzes and forms azeotrope with isopropanol under acidic conditions. To achieve environmental conservation, resource utilization, and clean production goals, the design of economically profitable separation processes becomes imperative. Pressure-swing distillation (PSD) with process intensification is employed after derived binary interaction parameters from VLE data at lower pressures, and sequential iteration simplified optimization is performed. Further to overcome the high energy consumption encountered in traditional PSD, heat integration and steam recompression technology were incorporated, resulting in four energy-saving PSD designs. And temperature-enthalpy diagrams were utilized to assess their energy consumption. Based on evaluation indicators of total annual cost (TAC), total energy consumption (TEC), and CO₂ emissions, all improved PSD processes significantly reduced TAC and CO₂ emissions. Among them, heat pump (HP-PSD) demonstrating the highest economy and eco-friendliness with a 30.1 % and 82.4 % reduction in TAC and CO₂ emissions. Heat pump assisted heat integration (HP-HIPSD) also attracted significant attention of reducing TAC by 16.3 %. A longer payback period is expected to yield higher cost savings from all enhanced designs. This study provides invaluable insights for the separation and sustainable development of alcohol ester azeotropes.