Correspondence pubs.acs.org/IECR
Reply to “Comment on ‘An Improvement to COSMO-SAC for Predicting Thermodynamic Properties’” R. Xiong, S. I. Sandler,* and R. I. Burnett Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, Delaware 19716, United States n Dr. Klamt’s first comment, he states “in eq 12 of their latest article,1 they now offer the original averaging equation as a simplification of eq 4”. A scaling factor fdecay was used in the σ-averaging equation in previous models.2,3 In the present article,1 we simplified the σ-averaging equation, and, although it turns out that it is of the same form as our original COSMOSAC paper,4 the purpose is different. The purpose in this article1 was to separate the electrostatics from the σ-averaging, which had not been done in our previous models.2−4 Also, we did not present this as the major contribution in this work. In fact, in this article,1 we have already given our credit to Dr. Klamt’s COSMO-RS paper5 and the work of Gmehling and coworkers6−8 for this simplified σ-averaging equation. In Dr. Klamt’s second comment, he points out “the authors are using quite exactly the averaging radii of 0.82 Å consistent with their first COSMO-SAC paper with DMol3 and of 0.51 Å, i.e., almost exactly the averaging radius suggested in the original COSMO-RS paper with COSMO files from ADF” and concludes that “it should be clearly stated that in contrast to the explicit claim made in the original COSMO-SAC paper4 of having achieved a consistency of ravand reff, all COSMO-RS implementations, including COSMO-SAC, do require an averaging radius rav which is much less than radius reff of an effective contact area”. We thank Dr. Klamt for pointing out this interesting observation. In our new parametrization in this article,1 we included the averaging radii (ravg) in the optimization with experimental data and did not intend to fix it in any specific value. In fact, we tried different initial guesses for ravg, although the optimization converged to more or less the same value. This consistency, in turn, confirms that our new parametrization is meaningful and successful. However, we do not agree with Dr. Klamt that it should be clearly stated in this article1 that all COSMO-RS implementations, including COSMO-SAC, require a ravg value that is much less than the radius reff of an effective contact area. This conclusion is only based on this σ-averaging equation. As he also mentioned, if the readers are interested in this point, they are referred to discussions in earlier comments regarding this issue.9,10
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(2) Wang, S.; Sandler, S. I.; Chen, C.-C. Refinement of COSMO− SAC and the Applications. Ind. Eng. Chem. Res. 2007, 46, 7275−7288. (3) Hsieh, C. M.; Sandler, S. I.; Lin, S. T. Improvements of COSMOSAC for vapor−liquid and liquid−liquid equilibrium predictions. Fluid Phase Equilib. 2010, 297, 90−97. (4) Lin, S. T.; Sandler, S. I. A priori phase equilibrium prediction from a segment contribution solvation model. Ind. Eng. Chem. Res. 2002, 41, 899−913. (5) Klamt, A.; Jonas, V.; Burger, T.; Lohrenz, J. C. W. Refinement and parametrization of COSMO-RS. J. Phys. Chem. A 1998, 102, 5074−5085. (6) Grensemann, H.; Gmehling, J. Performance of a conductor-like screening model for real solvents model in comparison to classical group contribution methods. Ind. Eng. Chem. Res. 2005, 44, 1610− 1624. (7) Mu, T. C.; Rarey, J.; Gmehling, J. Performance of COSMO-RS with sigma profiles from different model chemistries. Ind. Eng. Chem. Res. 2007, 46, 6612−6629. (8) Mu, T. C.; Rarey, J.; Gmehling, J. Group contribution prediction of surface charge density profiles for COSMO-RS(Ol). AIChE J. 2007, 53, 3231−3240. (9) Klamt, A. Comments on “A Priori Phase Equilibrium Prediction from a Segment Contribution Solvation Model”. Ind. Eng. Chem. Res. 2002, 41, 2330−2331. (10) Lin, S. T.; Sandler, S. I. Reply to “Comments on ‘A Priori Phase Equilibrium Prediction from a Segment Contribution Solvation Model’”. Ind. Eng. Chem. Res. 2002, 41, 2332−2334.
AUTHOR INFORMATION
Corresponding Author
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[email protected]. Notes
The authors declare no competing financial interest.
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REFERENCES
(1) Xiong, R.; Sandler, S. I.; Burnett, R. I. An Improvement to COSMO-SAC for Predicting Thermodynamic Properties. Ind. Eng. Chem. Res. 2014, DOI: 10.1021/ie404410v. © 2014 American Chemical Society
Published: May 15, 2014 8936
dx.doi.org/10.1021/ie501775s | Ind. Eng. Chem. Res. 2014, 53, 8936−8936
