Consideration of dimerization for property prediction with COSMO-RS-DARE

• COSMO-RS-DARE is shown, an extension of COSMO-RS for consideration of dimerization.
• It is tested on systems containing a carboxylic acid and a nonpolar component.
• New COSMO-RS-DARE parameters are obtained for observed systems.
• Results obtained with COSMO-RS-DARE are more accurate than results without extension.
• Parameters are general for all observed systems.

With COSMO-RS, interactions between molecules are described with statistical thermodynamics of interacting surface segments. Thereby, all spatial information is neglected. Hence, concerted multiple contacts of molecules, and therefore dimerization, are not captured with COSMO-RS.In this study COSMO-RS-DARE, an extension of COSMO-RS for consideration of dimerization when predicting liquid phase properties, is evaluated for binary mixtures of dimerizing carboxylic acids and nonpolar components. For this extension two new parameters are introduced. These dimerization parameters are determined for the above-mentioned mixtures. Furthermore, a generalization of these parameters for a general application to that type of systems observed in this study is investigated.For this purpose activity coefficients for the binary mixtures of carboxylic acids and nonpolar components, calculated with COSMO-RS-DARE, are fitted to activity coefficients determined using experimental data by varying the new parameters.A better description of mixtures containing a dimerizing carboxylic acid and a nonpolar component can be achieved with COSMO-RS-DARE. If the dimerization parameters are determined for a single system, this system can be described with a high accuracy. Good results are achieved also with dimerization parameters generalized for a general application. This holds for systems used to determine these parameters as well as for systems not used to determine these parameters.Therefore, it can be stated that activity coefficients calculated with COSMO-RS-DARE have a higher accuracy than activity coefficients calculated with COSMO-RS without this extension. Nevertheless, further investigations with more systems are necessary to evaluate portability of COSMO-RS-DARE to a broader range.

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