| Dicarboxylic acid is a kind of important chemical raw materials which can be further used to synthesis polyester, abundant of waste water will be generated from the process of terephthalic acid production, including its isomer isophthalic acid and phthalic acid. Therefore, research on how to extracting the useful substances from the residue with high efficiency and low energy consumption has important practical significance. The solvent crystallization separation was studied to solve the problem of high cost and long process when separating isomeric compounds. Recently, some researchers found that adduct crystallization could be used to recovery and purification the effective components from the residue. Terephthalic acid and isophthalic acid form adduct crystallization with some organic solvents, such as N,N-dimethyl formamide (DMF), N,N-dimethyl acetamide (DMAC) and N-methyl pyrrolidone (NMP).In this paper, the equilibrium solubility of phthalic acid in N,N-dimethyl formamide (DMF), N,N-dimethyl acetamide (DMAC) and N-methyl pyrrolidone (NMP) were measured experimentally using balance method at temperatures ranging from (283.15-333.15) K at atmospheric pressure. The solubility data were correlated by Van’t Hoff equation, Apelblat equation, Wilson equantion and NRTL equation, the paramaters of these equation and corresponding RMSD and RD were obtained. The fitting precision of Apelblat equation is better than those for other equations, the Apelblat equation is suitable for the correlation the solubility of system.The mutual solubility for ternary system of terephthalic acid+isophthalic acid+ N-methyl-2-pyrrolidone, phthalic acid+isophthalic acid+N-methyl-2-pyrrolidone and phthalic acid+terephthalic acid+N-methyl-2-pyrrolidone were measured at 303.15 K and 313.15 K, the equilibrium solution density was determinated. The solubility of ternary system was correlated by NRTL model, and the results show that the calculation has good agreement with the experiment value. The solubility of terephthalic acid+isophthalic acid+phthalic acid+ N-methyl-2-pyrrolidone quaternary system was measured by the moist solid method at 303.15 K and 313.15 K. There are three crystal areas, three saturation curves and one saturation point. Compared with the ternary phase diagram, when a third substance adds in, the solubility of other two materials in the solvent decrease.Thermal analysis was further carried to investigate the thermal decomposition kinetic of the prepared adduct IPA·2NMP using TG-DTG techniques with constant rate in nitrogen. The activity energy of IPA·2NMP thermal decomposition is obtained using Ozawa-Flynn-Wall method and Kissinger method without involving any decomposition mechanism of solid state. The activity energy of thermal decomposition of IPA-2NMP is obtained using the two models is 45.60 KJ·mol-1 and 35.49 KJ·mol-1, respectively, the decomposition temperature of the product measured is 333.15 K.The multivariate nonlinear regression was successfully used to determine the kinetic model for decomposition mechanism. The activity energy was calculated and the decomposition kinetics was predicted according to the regessed parameters. Different models were evaluated by the F value to describe the decomposition process of IPA-2NMP, and the model with the smallest F value will be the most suitable to describe the decomposition reaction. It can be concluded from the multivariable nonlinear regression results that the model of Bna, CnB, C1B, An and Fn can describe very well the decomposition reaction kinetics of IPA-2NMP. The F values for the five models are all less than 2, the correlation coefficients were greater than 0.99. |
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