| With the annual growth of phthalic acid(PTA)capacity,the amount of PTA oxidation residue also increases year after year.It has always been an issue about the treatment of PTA oxidation residue,which troubles the entire PTA industry.There are a lot of benzoic acid,terephthalic acid,m-phthalic acid and a small number of phthalic acid in PTA oxidation residue while the diisooctyl terephthalate(DOTP),diisooctyl mphthalate(DOIP)and diisooctyl phthalate(DOP)in industry are often used as plasticizer.Isooctyl benzoate can also be used as downstream productions.Therefore,a resourcebased method is put forward in this paper to make mixed plasticizer(DOTP,DOIP and DOP)using PTA oxidation residue as a raw material.We have obtained the optimal condition to compound mixed plasticizer,simulated and verified the purification process of mixed plasticizer by experiments,and furthermore the synthesis and separation process of mixed plasticizer were studied,which offered a certain guidance to resource utilization of the actual PTA oxidation residue.First of all,the simulated oxidation residue of PTA and isooctyl alcohol as raw materials were taken to investigate the effects of different catalysts on the yield of each component of synthetic mixed esters.The tetrabutyl titanate was filtrated to be the best catalyst.Furthermore,investigations about the effects of reaction temperature,molar ratio of reactants and amount of catalyst on the yield of each component of synthetic mixed esters were carried out to confirm the optimal reaction condition.Based on it,Aspen Plus was adopted to simulate the separation and purification of mixed esters from PTA oxidation residue and to optimize the feed stage,feed ratio and reflux ratio with the sensitivity analysis function,getting the optimal operating paraineters for separation of mixed esters by distillation.In a practical batch distillation unit,the mixed ester obtained by experiments was purified,from which the DOP quality score is 9.5%,DOIP quality score is 23.6%,DOTP quality score is 66.2%and the other components were only 0.7%.Secondly,Aspen Plus was adopted to simulate the separation and purification of mixed esters from actual PTA oxidation residue.There were three towers in the whole process,and operating parameters and the liquidoid composition distribution of each column plate in the distillation column were obtained.Under the optimal conditions,the mixed plasticizer was synthesized from actual PTA oxidation residue and got separation and purification in the distillation column.Lastly,the optimized process of producing plasticizer from PTA oxidation residue was discussed.The traditional reactive redistillation process,the traditional reactive redistillation and coupled differential pressure column process,the reactive distillation process and the reactive distillation coupled differential pressure column process were discussed respectively.The operation parameters of each process were obtained,the economic input of each process was calculated,and reactive distillation process was the best process through comparing various processes above. |
