Solvent Separation Of A Mixture Of Benzene Carboxylic Acid Model

As a very important material ,terephthalic acid is widely used in chemical industry .The most important use of it is purified to make polyester with ethynyl glycol. With the development of polyester industry,the production of purified terephthalic acid(PTA) has increased intensively. And the problem caused by the PTA residues has become more and more serious. According to various originations,the PTA residues are divided into there kinds which are respectively called the oxidation residue, the residue from the purification process and the residue from the effluent setting chamber. For the purpose of environmental protection and sufficient utilization of natural resources, it is necessary to separate, recover and reuse the residues.This work is concentrated on the technologic model of seperating the PTA residues using solvents.First of all,a laser monitoring observation system and programmed heating apparatus are set up to determine the solubilities of the systems which have quick solid-liquid equilibria by synthetic method. As well, another apparatus is set up to determine the solubilities of the systems which have slow S-L-E . The solubilities of 2 binary systems and 3 ternary systems are precisely determined. The binary systems include benzoic acid -chloroform system and p-toluic acid -chloroform system.And the 3 ternary systems are benzoic acid-p-toluicacid-chloroform co-solute system at 30 ,40 and50 . Totally 82experimental points are obtained. Through experiments,it is also proved that the solubilities of terephthalaldehydic acid and terephthalic acid & its isomeric compounds in chloroform are tremendously small,in other words, they do not solve in chloroform.On basis of the experimental data, a modified UNIFAC model is set up by defining 2 new functional groups, which are BA(Benzoic Acid),and MBA(p-Toluic Acid) .In this modified UNIFAC model, group volume -7parameters, group surface-area parameters and group interaction parameters are optimized. This model can perfectly predict the experimental solubilities. TheS-L-E of chloroform-p-toluic acid-benzoic acid ternary system at 50 is predicted using the BA/MBA group interaction parameters regressed from the solubilities of this ternary system at30and 40 together with the binaryinteraction parameters. The results also fit in well with the experimental values.Three ternary-system phase diagrams are drawn according to the predicted data by the modified UNIFAC model.Then,a technologic model is established to separate the mixed benzene carboxylic acids in the PTA residues mainly by using chloroform. Benzoic acid, terephthalic acid are recovered from the oxidation residue, terephthalic acid is recovered from the residue from the purification process and the residue from the effluent setting chamber.The recovered benzene carboxylic acids have fairly high purities.In the future,this technologic model for separating mi benzene carboxylic acid mixtures can be used in the engineering design of PTA residue recoveries.In the last part of this thesis,a set of laboratory apparatus for synthesizing the polyester (PET) is set up.A kind of polyester is produced from the synthesis of the terephthalic acid recoverd by the mentioned technologic model and ethylene glycol. The PET product has a relatively high molecular weight, which demonstrates that the recovered terephthalic acid has a high purity and the technologic model for separating benzen carboxylic acid mixtures presented in this thesis is feasible.