(180u) Position Group Contribution Method for the Prediction of Vaporization Heat of Organic Compounds
AIChE Annual Meeting
Monday, November 9, 2009 - 6:00pm to 8:00pm
1. Introduction Enthalpy of vaporization is an important parameter that is utilized for the design and operation of vapor?liquid equilibrium-based processes, where enthalpy of vaporization must be known for at least one temperature. It is not always possible, however, to find experimental values of properties for the compounds of interest in the literature. Since, it is not practical to measure them as the need arises, estimation methods are generally employed in this and other similar situations. There exist many empirical correlations that allow one to calculate the enthalpy of vaporization of pure fluids (Carruth and Kobayashi (1972), Svoboda and Smolova, 1994; Liley, 2003; Meyra et al., 2004).1-4 Certainly, the property may also be calculated by means of group contribution models (Basarova and Svoboda, 1995; Tu and Liu, 1996; Li et al., 1997; Fau xndez et al., 2000; Cuadros et al., 2003).5-10 However, most group contribution methods have a serious problem that they cannot distinguish among structural isomers. To overcome these limitations, esveral attemptes have been reported in the literature. Constantinou and Gani,11 Marrero and Gani,12 and Dalmazzone et al.13developed methods which perform estimations at different levels. Recently, Depends on three parameters related to the shape and size of the molecule and to the intermolecular interactions, Mulero et al.14 have proposed a model for the prediction of the enthalpy of vaporization at 273.15K of organic compounds. Recently, our Laboratory proposed a model for the prediction of critical properties of organic compounds. The higher prediction accuracy of the proposed method shown in our previous works suggests that it is possible to use a similar framework to predict the three critical properties, of organic compounds containing various functionalities. 15-19 Therefore, the objective of this work is the application our new model in the prediction of the enthalpy of vaporization of organic compounds at the normal boiling point and 298.15K using a database that covers a variety of chemical classes. 2. Method proposed in this work The standard enthalpies of vaporization function is constructed by all groups' contribution as well as the position correlation factor. The position correlation factor were used to take into account longer distance interactions, which could distinguish most isomer include cis- and trans- or Z- and E- structure of organic compounds for their thermodynamics properties. Here, the position distribution function for the estimation of standard enthalpies of vaporization is expressed as: Parameter or stands for or group contributions, for the number of each group that carbon element forms the centre of the group in the molecular formula, for the number of each group that non-carbon element forms the centre, for total number of groups, for the position correlation factor, and , for parameters of the model. The set of contributions that allowed to minimize the residual estimation difference was then computed by regression. is constant and is molecular weight. According to the IUPAC nominating method, we draw the structures and assign the values for the relevant positional correction. Table 1 reports the values computed for the group contributions . And our method developed is applicable only to comparatively low-molar-mass compounds involving carbon chain from C2 to C18. Conclusion Based on position group contribution method, a new method recently proposed for the estimation of the critical properties and boiling point as well as melting point , is extended to the prediction of standard enthalpies of vaporization. Contributions for compounds containing carbon, hydrogen, oxygen, nitrogen, chlorine and sulphur were reported, and that position distribution function has been developed which could distinguish between the thermodynamic properties of most isomers of organic compounds including cis- and trans- or Z- and E- structures. The results indicate that our model provides highly significances. The overall means absolute difference for enthalpies of vaporization predictions of 223 organic compounds is 2.78%. The higher prediction accuracy of the proposed method shown in our previous works and this work suggests that it is possible to use a totally same framework to predict the critical properties and the thermodynamics properties, of organic compounds containing various functionalities. Literature Cited 1. Carruth, G. F. and Kobayashi, R. (1972). Ind. Eng. Chem. Fundam.,11, 509 2. Svoboda, V. and Smolova, H. (1994). Fluid Phase Equilib.,97, 1 3. Liley,P.E.(2003). Ind.Eng.Chem.Res., 42, 6250. 4. Meyra, A.G., Kuz, V. A., and Zarragoicoechea,G. J.(2004). FluidPhaseEquilib., 218,205. 5. Basarova, P. and Svoboda, V. (1995).Fluid Phase Equilib.,105, 27 6. Tu,C.H. and Liu,C.P.(1996). FluidPhaseEquilib., 121,45. 7. Li et al., 1994; (4) Li, P.; Ma, P. S.; Yi, S. Z,; Zhao, Z. G.; Cong, L. Z. (1994). Fluid Phase Equi. 101, 101?119 8. Li, P.; Liang, Y.H., Ma, P. S.; Zhu, C., (1997). Fluid Phase Equi. 101, 101?119 9. Faundez, C. A., Mulero, A., and Cuadros, F.(2000). J. Phase Equilib., 21,364 10. Cuadros, F., Mulero, A., Okrasinski, W., Faundez, C. A., and Parra, M.I.(2003). Rev.Chem.Eng.,19,387 11. Constantinou and Gani,5 (5) Constantinou, L.; Gani, R. New group contribution method for estimating properties of pure compounds. AIChE J. 1994, 40, 1697-1710 12. Marrero and Gani,6 (6) Marrero, J.; Gani R. Group-contribution based estimation of pure component properties. Fluid Phase Equilibria 2001, 183?184, 183?208 13. Dalmazzone,D., Salmon, A., and Guella, S., 2006. Fluid Phase Equilibria, 242, 29-42 14. Mulero, A., CACHADINA, I., CUADROS, F.,2006,Chem.Eng.Comm.,193:192-205 15. Wang, Q.; Ma, P. Sh; Jia, Q. Zh.; Xia, Sh. Q. Position Group Contribution Method for the Prediction of Critical Temperatures of Organic Compounds. J. Chem. Eng. Data 2008, 53, 1103-1109 16. Wang, Q.; Jia, Q. Zh.; Ma, P. Sh. Position Group Contribution Method for the Prediction of Critical Pressure of Organic Compounds. J. Chem. Eng. Data 2008, 17. Jia, Q. Zh.; Wang, Q.; Ma, P. Sh. Position Group Contribution Method for the Prediction of Critical Volume of Organic Compounds. J. Chem. Eng. Data 2008, 53 (11), 2606-2612 18. Wang, Q.; Ma, P.; Wang, C.; Xia, S. Position Group Contribution Method for the Prediction of Boiling Point of Organic Compounds. Chin. J. Chem. Eng. 2009, 17 (2), 254-258 19. Wang, Q.; Ma, P.; Nai, S. Position Group Contribution Method for the Prediction of Melting Point of Organic Compounds. Chin. J. Chem. Eng. 2009, 17 (3), 468-472
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