UV-Vis spectroscopic studies of solute–solvent and solute–cosolvent interactions in supercritical carbon dioxide

Abstract

The keto–enol tautomeric equilibria of ethyl acetoacetate in supercritical (SC) CO₂ with and without ethanol cosolvent were investigated over the pressure range from 75.9 to 185 bar at 308.2 K using UV-Vis spectroscopy. In order to obtain the local densities of solvent and cosolvent about the solute, we correlated the standard Helmholtz free energy of the tautomerization with a solvent parameter based on the Onsager reaction field theory. In both SC CO₂ and SC CO₂–ethanol, the local density enhancement of CO₂ in the vicinity of the solute is most remarkable at the reduced density close to unity. The highest degree of aggregation of cosolvent about the solute takes place at the lowest pressure investigated, which is slightly above the critical pressure. Moreover, the clustering of ethanol with the solute competes with that of CO₂. In addition, the local concentration enhancement of ethanol was studied in the concentration range of 0 to 6 mol%. It was found that the local concentration of ethanol is enhanced significantly at lower cosolvent concentrations.

References

1. G. M. Schneider, Angew. Chem. Int. Ed. Engl., 1978, 17, 716.
2. T. J. Bruno and J. F. Ely, Supercritical Fluid Technology: Reviews in Modern Theory and Applications, CRC Press, Boca Raton, FL, 1991.
3. D. A. Moyler, in Extraction of Natural Products Using Nearcritical Solvents, ed. M. B. King and T. R. Bott, Chapman & Hall, Glasgow, 1993.
4. M. A. McHugh and V. J. Krukonis, Supercritical Fluid Extraction: Principles and Practice, Butterworths, Stoneham, MA, 2nd edn., 1994.
5. P. E. Savage, S. Gopalan, T. I. Mizan, C. J. Martino and E. E. Brock, AIChE J., 1995, 41, 1723.
6. A. V. Yazdi and E. J. Beckman, J. Mater. Res., 1995, 10, 530.
7. E. J. Beckman, Science, 1996, 271, 613.
8. D. J. Dixon, G. Luna-Barcenas and K. P. Johnston, Polymer, 1994, 35, 3998.
9. (a) C. A. Eckert, D. H. Ziger, K. P. Johnston and T. K. Ellison, Fluid Phase Equilib., 1983, 14, 167; (b) C. A. Eckert, D. H. Ziger, K. P. Johnston and S. Kim, J. Phys. Chem., 1986, 90, 2738.
10. P. G. Debenedetti, Chem. Eng. Sci., 1987, 42, 2203.
11. (a) S. Kim and K. P. Johnston, AIChE J., 1987, 33, 1603; (b) S. Kim and K. P. Johnston, Ind. Eng. Chem. Res., 1987, 26, 1206.
12. C. R. Yonker and R. D. Smith, J. Phys. Chem., 1988, 92, 235.
13. R. M. Lemert and J. M. DeSimone, J. Supercrit. Fluids, 1991, 4, 186.
14. (a) Y.-P. Sun, M. A. Fox and K. P. Johnston, J. Am. Chem. Soc., 1992, 114, 1187; (b) Y.-P. Sun, G. Bennett, K. P. Johnston and M. A. Fox, J. Phys. Chem., 1992, 96, 10001; (c) Y.-P. Sun and M. A. Fox, J. Phys. Chem., 1993, 97, 282.
15. C. Carlier and T. W. Randolph, AIChE J., 1993, 39, 876.
16. A. Morita and O. Kajimoto, J. Phys. Chem., 1990, 94, 6420.
17. R. S. Urdahl, K. D. Rector, D. J. Myers, P. H. Davis and M. D. Fayer, J. Chem. Phys., 1996, 105, 8973.
18. J. F. Brennecke, D. L. Tomasko, J. Peshkin and C. A. Eckert, Ind. Eng. Chem. Res., 1990, 29, 1682.
19. (a) J. Zagrobelny and F. V. Bright, J. Am. Chem. Soc., 1992, 114, 7821; (b) T. A. Betts, J. Zagrobelny and F. V. Bright, J. Am. Chem. Soc., 1992, 114, 8163; (c) T. A. Betts, J. Zagrobelny and F. V. Bright, J. Supercrit. Fluids, 1992, 5, 48.
20. Y.-P. Sun, T. L. Bowen and C. E. Bunker, J. Phys. Chem., 1994, 98, 12486.
21. D. G. Peck, A. J. Mehta and K. P. Johnston, J. Phys. Chem., 1989, 93, 4297.
22. S.-i. Ikawa and Y. Fujita, J. Phys. Chem., 1993, 97, 10607.
23. K. P. Johnston and C. Haynes, AIChE J., 1987, 33, 2017.
24. C. B. Roberts, J. E. Chateauneuf and J. F. Brennecke, J. Am. Chem. Soc., 1992, 114, 8455.
25. Y. Ikushima, N. Saito and M. Arai, J. Phys. Chem., 1992, 96, 2293.
26. T. W. Randolph and C. Carlier, J. Phys. Chem., 1992, 96, 5146.
27. (a) T. A. Rhodes, K. O'Shea, G. E. Bennett, K. P. Johnston and M. A. Fox, J. Phys. Chem., 1995, 99, 9903; (b) G. E. Bennett, P. J. Rossky and K. P. Johnston, J. Phys. Chem., 1995, 99, 16136.
28. I. B. Petsche and P. G. Debenedetti, J. Chem. Phys., 1989, 91, 7075.
29. R.-S. Wu, L. L. Lee and H. D. Cochran, Ind. Eng. Chem. Res., 1990, 29, 977.
30. I. G. Economou and M. D. Donohue, AIChE J., 1990, 36, 1920.
31. K. Koga, H. Tanaka and X. C. Zeng, J. Phys. Chem., 1996, 100, 16711.
32. J. P. O'Connell, Fluid Phase Equilib., 1995, 104, 21.
33. C. C. Liew, H. Inomata and S. Saito, Fluid Phase Equilib., 1995, 104, 317.
34. J. M. Dobbs and K. P. Johnston, Ind. Eng. Chem. Res., 1987, 26, 1467.
35. Y. Koga, Y. Iwai, Y. Hata and Y. Arai, Fluid Phase Equilib., 1996, 125, 115.
36. D. L. Tomasko, B. L. Knutson, F. Pouillot, C. L. Liotta and C. A. Eckert, J. Phys. Chem., 1993, 97, 11823.
37. A. K. Dillow, K. P. Hafner, S. L. J. Yun, F. Deng, S. G. Kazarian, C. L. Liotta and C. A. Eckert, AIChE J., 1997, 43, 515.
38. R. B. Gupta, J. R. Combes and K. P. Johnston, J. Phys. Chem., 1993, 97, 707.
39. D. Andrew, B. T. Des Islet, A. Margaritis and A. C. Weedon, J. Am. Chem. Soc., 1995, 117, 6132.
40. J. B. Ellington, K. M. Park and J. F. Brennecke, Ind. Eng. Chem. Res., 1994, 33, 965.
41. S. P. Kelley and R. M. Lemert, AIChE J., 1996, 42, 2047.
42. B. L. Knutson, S. R. Sherman, K. L. Bennett, C. L. Liotta and C. A. Eckert, Ind. Eng. Chem. Res., 1997, 36, 854.
43. C. A. Eckert and B. L. Knutson, Fluid Phase Equilib., 1993, 83, 93.
44. R. D. Schulte and J. F. Kauffman, J. Phys. Chem., 1994, 98, 8793.
45. D. M. Pfund and H. D. Cochran, in Supercritical Fluid Engineering Science: Fundamentals and Applications, ed. E. Kiran and J. F. Brennecke, ACS Symp. Ser. 514, American Chemical Society, Washington, DC, 1991, ch. 12.
46. K. E. O'Shea, K. M. Kirmse, M. A. Fox and K. P. Johnston, J. Phys. Chem., 1991, 95, 7863.
47. K. Yamasaki and O. Kajimoto, Chem. Phys. Lett., 1990, 172, 271.
48. M. T. Rogers and J. L. Burdett, Can. J. Chem., 1965, 43, 1516.
49. G. Allen and R. A. Dwek, J. Chem. Soc. B, 1966, 161.
50. J. Powling and H. J. Bernstein, J. Am. Chem. Soc., 1951, 73, 4353.
51. M. M. Folkendt, B. E. Weiss-Lopez, J. P. Chauvel and N. S. True, J. Phys. Chem., 1985, 89, 3347.
52. CRC Handbook of Chemistry and Physics, ed. D. R. Lide, CRC Press, Boca Raton, FL, 75th edn., 1994.
53. M. Zhong, J. Ke, B. Han and H. Yan, Acta Physico-Chimica Sinica, 1996, 12, 816.
54. K. Suzuki, H. Sue, M. Itou, R. L. Smith, H. Inomata, K. Arai and S. Saito, J. Chem. Eng. Data, 1990, 35, 63.
55. D. W. Jennings, R.-J. Lee and A. S. Teja, J. Chem. Eng. Data, 1991, 36, 303.
56. J.-H. Yoo, H.-S. Lee and H. Lee, J. Chem. Eng. Data, 1993, 38, 53.
57. C. N. Rao, Ultra-Violet and Visible Spectroscopy, Butterworths, London, 1961, p. 70.
58. The Sadtler Standard Spectra, Sadtler Research Laboratories, Inc., USA, 1975, p. 54.
59. F. H. Huang and M. H. Li, Chem. Eng. Jpn., 1985, 18, 490.
60. L. J. Onsager, J. Am. Chem. Soc., 1936, 58, 1486.
61. G. E. Papanastasiou and I. Ziogas, J. Chem. Eng. Data, 1991, 36, 46.
62. A. Michels and C. Michels, Philos. Trans. R. Soc., London Ser. A, 1933, 231, 409.
63. G. E. Bennett and K. P. Johnston, J. Phys. Chem., 1994, 98, 441.
64. M. P. Heitz and F. V. Bright, J. Phys. Chem., 1996, 100, 6889.
65. J. K. Rice, E. D. Niemeyer, R. A. Dunbar and F. V. Bright, J. Am. Chem. Soc., 1995, 117, 5832.
66. B. L. Knutson, D. L. Tomasko, C. A. Eckert, P. G. Debenedetti and A. A. Chialvo, in Supercritical Fluid Technology: Theoretical and Applied Approaches to Analytical Chemistry, ed. F. V. Bright and M. E. P. McNally, ACS Symp. Ser. 488, American Chemical Society, Washington, DC, 1992, p. 60.
67. A. Wesch, N. Dahmen and K. H. Ebert, Ber. Bunsen-Ges Phys. Chem., 1996, 100, 1368.
68. H. Looyenga, Physica, 1965, 31, 401.