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Study On Phase Equilibrium Of Mixed Dibasic Acid Addition Crystallization Process

Posted on:2016-09-19Degree:MasterType:Thesis
Country:ChinaCandidate:L WangFull Text:PDF
GTID:2271330470481638Subject:Chemical engineering
Abstract/Summary:PDF Full Text Request
Adipic acid is one of the two main material for the production of nylon 66 and nylon 66 salts. Its production process is mainly by the oxidation of nitric acid, cyclohexanol or cyclohexanone in the role of copper, vanadium salt as catalyst. Some by-products were produced in the production process, such as glutaric acid and succinic acid. The so-called mixed dibasic acid is a mixture of dibasic acid obtained by the crystallization in a suitable solvent, such as water, diethylene glycol and so on. In this paper, some research on purifying and separating of mixed dibasic acid has been made, which provided basic theory guidance and fundermental data for the crystallization process of dibasic acid. Theoretical basis on separation of dibasic acids by crystallization method of urea adduct is the solubility of urea and dibasic acids in different solvents. However, no further investigations on the ternary phase diagrams were made in the literature. Therefore, the study of solubility for urea and dibasic acid in solvents, constructing ternary phase diagrams and separating dibasic acid according to the phase diagram by crystallization has both higher academic value and great practical significance.(1) Solid-liquid phase equilibrium had been measured for the binary systems of succinic acid + glutaric acid, glutaric acid + adipic acid, adipic acid + succinic acid by using differential scanning calorimetry (DSC). The melting temperatures and enthalpies of fusion were obtained. It was found that this system was a simple eutectic system. The eutectic compositions are 0.3760 at 350.95 K (mole fraction of succinic acid),0.6433 at 360.35 K (molar fraction of glutaric acid) and 0.6107 at 382.75 K (molar fraction of adipic acid) respectively. Furthermore, the solubility obtained in binary mixtures of (succinic acid + glutaric acid, glutaric acid + adipic acid, adipic acid + succinic acid) have been compared with those predicted by the ideal model and correlated by Wilson and NRTL equations. The calculated solubility via NRTL model showed well agreement with the experimental values.(2) The mutual solubility and density value-composition relationship of succinic acid + urea + water, glutaric acid + urea + water, adipic acid + urea + water were determined by Schreinemaker’s method of residue at 288.15K and 303.15K, respectively. The phase diagrams of these systems were constructed on the basic of the measured solubilitity. The solubility data were correlated using the NRTL model. Comparing simulated datas with experimental values, the standard deviation is small and the simulation result is acceptable.(3) The solubility of succinic acid, glutaric acid, adipic acid, and urea in diethylene glycol were measured in different temperatures and the solubility was fitted by using solubility empirical equation, the fitted standard deviation is small and the result is acceptable.The mutual solubility and density value-composition relationship of succinic acid + urea + diethylene glycol, glutaric acid + urea + diethylene glycol, adipic acid + urea + diethylene glycol were determined by Schreinemaker’s method at 298.15K and 333.15K, the phase diagrams of these systems were constructed on the basic of the measured solubilitity.(4) In this paper, the adducts of 2:1 urea-succinic acid,2:1 urea-glutaric acid,1:1 urea-glutaric acid,2:1 urea-adipic acid were prepared.These adducts were characterized by Infrared spectroscopy (IR) and differential scanning calorimetry (DSC).
Keywords/Search Tags:Succinic acid, Glutaric acid, Adipic acid, Adduct crystallization, Phase diagram, Phase equilibrium, NRTL, Wilson
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