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The Determination, Correlation And Calculation Of The Excess Enthalpies For The Binary System Of Alcohols And Esters

Posted on:2008-03-02Degree:DoctorType:Dissertation
Country:ChinaCandidate:H DongFull Text:PDF
GTID:1101360215477423Subject:Chemistry
Abstract/Summary:PDF Full Text Request
The research of excess thermodynamics not only aid to clarify the structure of solution, test and improve theories of solution, but also can provide significant thermodynamic basic data for the development and design of chemical engineering process, and also can provide pivotal data to calculate the properties of multi-components compounds. The investigation on the interaction between unlike molecules in the system of interest can be carried out by measurement of the excess molar enthalpies. Then we can correlate the macroscopic thermodynamic properties and microcosmic intermolecular interaction, molecular size and so on to form modern solution theory. In the research of solution phenomenon, excess enthalpy is an important thermodynamic property. It reflects the degree of liquid mixtures deviated from ideal solution, and it is the one of primary sign to scale the nonideal property of solution.The application of excess enthalpy namely mixed heat is very extensive in the production and design of chemical engineering. The accuracy of vapor components is not good in the experimental process, it is difficult to measure vapor-liquid equilibrium for some systems, whose components are very different from each other in their boiling point; especially there is a component with easy volatility. Then we can use excess enthalpy data to estimate activity coefficients, and to predict vapor-liquid equilibrium (VLE), liquid-liquid equilibrium data. We can predict VLE, LLE (liquid-liquid equilibrium) data from the properties of pure components and excess enthalpy data, and decrease mostly experimental work. There need excess enthalpy data to test the thermodynamic consistency of the isobaric VLE data. Many research groups expatiate on the mentioned experimental methods, data and theory to accelerate the development of this field. Excess properties, for example excess volume, excess Gibbs energy, excess enthalpy, excess entropy etc, are mostly used for describing the behavior of solution, it is not only change with the influence of temperature and pressure, but also it is a function of components at the constant temperature and pressure. Excess function provides a significant and economical method to the application in more than two mixtures. These methods decrease the experimental work of describing multi-components.In the first chapter of this thesis, we summarize the references about our research and introduce the correlative theories. The current developments of theories were summarized and the research contents of this thesis were described. The second chapter, we introduce the experimental contents. The excess enthalpies of esters and alcohols at high temperature and pressure were determined by CSC4400 flow mixing micro-calorimeter. We can investigate the effects of temperature, pressure, mole fractions and the carbon numbers on excess enthalpies from data acquisition, result and discussion. In order to explain better the experimental phenomenon, we calculated the interaction energies of the binary system DMEA and alcohols by quantum chemistry calculation software in the third chapter. The optimized geometry and energies were discussed using Gaussian 03 at RB3LYP/6-31++G (d, p) level. We expatiate on the process of COSMO calculation; this is the base of COSMO models calculation in the fourth chapter. The proposition and development of a new model to predict thermodynamic properties, and its' application to predict the excess enthalpies were also introduced in this chapter. The application to predict vapor-liquid equilibrium was introduced in fifth chapter. We can acquire the VLE data used the parameters correlated from experimental data of excess enthalpies and the classical activity coefficient models. The estimation data was compared with the prediction results from COSMO-SAC model. In the last chapter, all of the experimental work and theories calculation were summarized; we find the deficiencies in this thesis and propose the idea of the latter research.
Keywords/Search Tags:excess enthalpies, vapor-liquid equilibrium, Wilson equation, NRTL equation, UNIQUAC equation, COSMO model, esters, and alcohols
PDF Full Text Request
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