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

Application of the Conduct-like Screening Models for Real Solvent and Segment Activity Coefficient for the Predictions of Partition Coefficients and Vapor–Liquid and Liquid–Liquid Equilibria of Bio-oil-Related Mixtures

The 1-octanol/water partition coefficients (log <i>P</i>) at 298.15 K and the vapor–liquid and liquid–liquid equilibria (VLE and LLE) of biofuel-related mixtures have been predicted with four different thermodynamic models: conduct-like screening models for real solvent (COSMO-RS), conduct-like screening models for segment activity coefficient (COSMO-SAC) (2002 version), modified COSMO-SAC (2006 version), and universal functional activity coefficient (UNIFAC). The 2002 version of COSMO-SAC gives more reasonable predictions for log <i>P</i> for most investigated mixtures than the other two approaches when appropriate molecular geometries are chosen for the computation of the σ profiles. However, the COSMO-RS model gives better predictions for VLE pressures and vapor-phase compositions for biofuel-related mixtures, as well as for the LLE of the 1-octanol + water and furfural + water mixtures. The accuracy of the models for the predictions of the partition coefficients and VLE may be improved by changing the molecular conformations used to generate the σ profiles. Generally, the three COSMO-based models give better predictions than UNIFAC for log <i>P</i> and VLE of the investigated systems and can be applied to predict the thermodynamic properties of the biofuel-related mixtures especially when no experimental data are available