Study On Synthesis Process And Application Of Trioctyl Citrate And Acetyl Trioctyl Citrate

Trioctyl citrate (TOC) was firstly synthesized from citric acid and 2-ethylhexanol in the presence of tetrabutyl titanate as catalyst, and then acetyl trioctyl citrate (ATOC) was prepared with TOC and acetic anhydride with sulphamic acid as catalyst. The optimized reaction conditions of esterificaton and acetylization were abtained via experiments. Based on the above, thermodynamics and kinetics including three esterification reactions and one side reaction were studied in detail for the synthesis process of TOC. Finally, plasticizing effect of TOC and ATOC on PVC films were investigated by different performance tests.The optimal synthesis conditons of TOC are as follows:the mass ratio of catalyst is 1.4 wt% of citric acid, n(2-ethylhexanol):n(citric acid)= 4.5:1, reaction time is 4.0 h at 150℃-160℃. The optimum process conditons of ATOC are as follows:the mass ratio of catalyst is 1.5 wt% of TOC, n(aceticanhydride):n(TOC)= 1.8:1, reaction time is 1.5 h at 100℃.The results of thermodynamic analysis show that three esterification reactions are exothermic and the equilibrium constants are in the range of 2254.38-5561.87 within 140℃-170℃, which indacates the reactions are almost irreversible. A by-product during the esterification process has been determined by means of 1H-NMR and LC-MS. Then a kinetic model combined with three esterification reactions and one side reaction was developed. The model parameters ki and Eai for each reaction have been estimated by fitting the kinetic experimental datas. The results show that the activation energies of the first and second steps are smaller than that of the third step, which is sligthly smaller than that of the side reaction.The performance testing results show that PVC films plasticized by TOC and ATOC are superior to those plasticized by DOP, TBC and ATBC in mechanical properties, thermostability and resistance transference. Therefore, TOC and ATOC can be widely used in PVC products in replace of DOP for higher requirement, such as healthy and safety, and also make up for the poor migration resistance of citrate plasticizers.