Optimal design and performance comparison of reaction-coupled extractive distillation processes for acetonitrile-tert-butanol-water system

Abstract

In the chemical and pharmaceutical industries, a large amount of wastewater containing acetonitrile (ACN) and tert‑butanol (TBA) is generated. The effective separation of the ACN/TBA/water system poses a significant challenge due to the presence of multiple azeotropes. To overcome the limitations of high energy consumption and low efficiency of conventional extractive distillation (CED), this study proposes three reaction-coupled extractive distillation processes—reactive distillation followed by extractive distillation (RD-ED), extractive distillation followed by reactive distillation (ED-RD), and reactive-extractive distillation (RED). During the process optimization aimed at the total annual cost (TAC) and CO₂ emissions, since the azeotropes of ACN/water and ACN/TBA are pressure-sensitive, the pressure of ACN extractive distillation column is optimized, resulting in significant energy savings. These processes are comprehensively compared in terms of economy, environmental impact, energy, and exergy efficiency. The results indicate that compared with the CED, the reaction-coupled extractive distillation processes have achieved significant optimization effects in multiple aspects. Among them, the RED process exhibits the optimal comprehensive performance: the TAC is reduced by 33.82 %, CO₂ emissions are decreased by 40.44 %, the total energy consumption is lowered by 41.55 %, and the thermodynamic efficiency is increased to 27.93 %.