J. Phys. Chem. B 2009, 113, 6581
Reply to “Comment on ‘Characterization of the Ability of CO2 to Act as an Antisolvent for Ionic Liquid/Organic Mixtures’” Joan F. Brennecke,* Aaron M. Scurto,† and Sudhir N. V. K. Aki‡ Department of Chemical and Biomolecular Engineering, UniVersity of Notre Dame, Notre Dame, Indiana 46556 ReceiVed: October 21, 2008; ReVised Manuscript ReceiVed: February 03, 2009 We fully agree with Ku¨hne et al. that the phase transitions that we had identified in Scurto et al.1 and subsequent publications were not LCEPs (lower critical end points). They are, in fact, simple phase transitions of the type L + V f L1 + L2 + V. We apologize for any confusion that this may have caused. The points originally identified as K-points do exhibit critical opalescence. This is likely due to the fact that there is no detectable ionic liquid in the vapor phase or the less dense liquid phase. Therefore, as the phase transition is approached, those * To whom correspondence should be addressed. E-mail:
[email protected]. † Current address: University of Kansas, Department of Chemical & Petroleum Engineering, 4132 Learned Hall, 1530 W. 15th St., Lawrence, KS 66045-7609. ‡ Current address: Intermediates R&D, Invista S.a.r.l., Sabine River Laboratory B 568, 3055A FM 1006 Road, Orange, TX 77630.
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two phases are essentially binary mixtures of the organic and CO2. Thus, it is no surprise that the phase transitions that we identified as K-points exhibit critical opalescence and occur at the same pressure at a given temperature as the binary mixture critical points of the organic and CO2. More importantly, we showed that the phase transitions that we described as K-points occurred at the same pressure at a given temperature, regardless of the initial molar ratio of ionic liquid to organic compound. In other words, there is only one degree of freedom, consistent with the phase rule for a critical point, as described by Ku¨hne et al. Except for the presence of an infinitesimal amount of ionic liquid, the vapor and liquid phases do become identical, in the presence of a heavier liquid phase, at an effective K-point. Finally, we appreciate that Ku¨hne et al. recognize the usefulness of the data that we have presented. The paper by Scurto et al.1 was the first to show that CO2 pressure could be used to induce phase splits in ionic liquid/organics systems as a way of recovering and purifying the ionic liquid and the organic. We are pleased that a number of research groups, including that of Professor Peters, have pursued work based on this discovery. References and Notes (1) Scurto, A. M.; Aki, S. N. V. K.; Brennecke, J. F. J. Am. Chem. Soc. 2002, 124, 10276–10277.
JP809307R
10.1021/jp809307r CCC: $40.75 2009 American Chemical Society Published on Web 04/14/2009
