Thermodynamics Foundation and Separation Process Design for Production of Propionic Acid from Ethanol Carbonylation Catalyzed by Iodide

Ethanol carbonylation catalyzed with iodoethane has gradually received much attention as a promising propionic acid production process. However, the separation of products is one of the most key bottle-neck problems for this method used in the industry because of the existence of the azeotrope and the lack of thermodynamic data for designing the product separation process. In this article, the vapor–liquid equilibrium data of iodoethane/propionic acid and iodoethane/ethyl propionate were measured and regressed. Based on the thermodynamics data, two heterogeneous azeotrope distillation separation processes with different reflux strategies to recover the propionic acid were simulated and compared, which was optimized by minimizing the total annual cost and maximizing the recovery of propionic acid. The result indicates that the azeotrope distillation process with the two phases refluxing was proved to be a better strategy currently to recover more propionic acid. These results also provide chemical engineers with an alternative way to produce propionic acid.