Modeling of the Phase Behavior of Carboxylic Acid Systems Using the SAFT-VR Mie DBD Model: Application to the Simulation of the Acrylic Acid Production Process

A new model, referred to as the SAFT-VR Mie DBD model, is proposed to capture the intricate behavior of short carboxylic acids. The new model is based on the SAFT-VR Mie model and integrates a general association term encompassing the formation of doubly bonded dimers (DBD), which enables precise predictions of vaporization enthalpies, densities, heat capacities, and phase behavior for both pure carboxylic acids and their mixtures. This work focuses on the acrylic acid (AA) production process from the oxidation of propene, which involves various unit operations (flash separation, absorption, liquid-liquid extraction, and distillation units). The SAFT-VR Mie DBD model can accurately describe vapor-liquid equilibrium (VLE) data, excess enthalpies, and other essential properties of mixtures containing acetic acid (ACE), acrylic acid (AA), diisopropyl ether (DIPE), water, and various components. To facilitate the practical application of the new thermodynamic model in an industrial context, a dynamic link library (DLL) is developed and made compatible with Simulis Thermodynamics to generate a CAPE-OPEN property package. The process simulations performed on Aspen Plus demonstrate the feasibility of using the SAFT-VR Mie DBD model for designing and optimizing the acrylic acid production process. This study serves as a proof of concept, thereby showcasing the possibility of employing complex thermodynamic models for simulating industrial processes.