Research Of Reaction Mechanism And Reaction Kinetics Of Preparation Of Dioctylterephthalate

Dioctylterephthalate(DOTP) is a kind of new PVC residuces recovery which developes in recent years,it's more and more widely recognized by rubber and plastic industry for its high insulation ,softness and good merits of low volatilization ,heat and cold resisting and good consistency with PVC. Some of its merits are better than the merits of all function residuces recovery named Dioctylphthalte(DOP).DOTP is synthesized by terephthalic acid and 2-ehtyl-1-hexanol. Sulfuric acid and nonacid ester catalyst are used in the formation of DOTP now. Sulfuric acid catalyst has many disadvantages which include corruption to the equipment ,side reaction , carbonization and deep color and lustre,but nonacid ester catalyst can avoid these disadvantages ,for this reason nonacid ester catalyst has gotton the universal attention.In order to get the basic data for industry production in a large scale and obatain useful information,such as the influence of catalyst,reaction temperature,mixing speed and reaction time,it's necessary to study the reaction mechanism and reaction kinetics and to optimize the synthetic condition of DOTP. At present the documents about the dynamics of DOTP are not enough. Liu Xingpeng of Qingdao Institute of Chemical Technology studied the dynamics of DOTP using the catalyst SnCl2 and broughtforward the formula -DCA/dt= kCA ,Ca is the consistency of terephthalic acid. Thevalue of apparent activation energy Ea is 34.03 KJ mol-1,and the value of rate constant k is 3.82xl04exp(-4837/T) L3 mol-1 min-1 ,T is the reactiontemperature.Dai Lizong of Xiameng University used the formula in high polymer chemistry .He got some rate constants of different temperatures then obtained the apparent activation energy by arrhenius graphing method. The value of apparent activation energy Ea he got is 63.05KJ/mol and is much different from the data of Liu Xingpeng's.The two people had different research ways and got different answers.At present we have not gotten the documents about dynamices of DOTP using the catalyst tetrabutyl titanate,so we have a desire to study the kinetics and mechanism ofDOTP using catalyst tetrabutyl titanate.Our conclusion tells that this esterification reaction is a consecutive parallel reaction. This reaction is divided into two steps,the first step is the synthesis of mono-(2-ethylhexyl) terephthalate from terephthalic acid ,the second step is synthesis of Dioctyl Terephthalate from mono-(2-ethylhexyl) terephthalate. The reaction is a heterogenious reaction in early stage then a homogeneous reaction in final time.We have not found any paper about mono-(2-ethylhexyl) terephthalate and know nothing about it ,so we synthesize it by using SOCI2 and terephthalic acid.then we determinate its chemical and physical property which is very important to the determinating of kinetics of DOTP.In this article we study four elements which effect yield of DOTP,the four elements are the amount of catalyst, grain size of terephthalic acid,mixing speed and mole ratio of alcohol and acid. By determinating the amount of water and titrating the amount of mono-(2-ethylhexyl) terephthalate in the reaction liquid we obtain the concentration distribution of all materials in the reaction liquid in the optimized condition, we know this complicated reaction agrees the features of consecutive parallel reaction by calculations we can treat it as a single stage consecutive reaction.The formula is -dCa/dt = k1CACB and -dCR/dt = k1CACB-k2CRCB ,CA is theconsistency of terephthalic acid,Ce is consistency of 2-ehtyl-l-hexanol,CR is consistency of mono-(2-ethylhexyl) terephthalate.The value of apparent activationenergy Ea1 equals Ea2 and the value is 86.63 KJ mol-1, the value of frequency factor km is 1.243 x107L3 mol-1 min-1 and the value of k02 is2.245 x108L3 mol-1 min-1. We also find that the translaotry speed of DOTP from mono-(2-ethylhexyl) terephthalate is about 19 times of that of mono-(2-ethylhexyl) terephthalate from terephthalic acid...