The Synthesis Of Plasticizer Citrate Under Microwave And New Catalyst

Tetraoctyl pyromellitate (TOPM) was synthesized from pyromellitic dianhydride and isooctyl alcohol over butyl titanate under microwave radiation. The solid super acid catalyst SO42-/TiO2-SiO2 was prepared and tributyl citrate(TBC) was synthesized over SO42-/TiO2-SiO2 using citric acid and n-butanol as reactants.The main findings are as follows:In the synthesis of TBC over SO42-/TiO2-SiO2,the solid acid preparation conditions such as content of SiO2 and calcination temperature have great influence on the catalytic activity of SO42-/TiO2-SiO2. The optimum preparation conditions are:weight ratio of SiO2 to TiO2 is 3:2, calcination temperature is 400℃. By orthogonal experiments the optimum synthesis conditions were determined as follows:molar ratio of n-butanol to citric acid is 4.0:1, reaction time is 180 minutes, dosage of catalyst is 4% of citric acid weight. Under the above conditions, the yield of TBC reached 96.6%. Meanwhile, The reaction mechanism was studied. The solid-liquid heterogeneous phase reaction kinetics model was established. Based on the experimental data, the model parameters were determined. In addition, SO42-/TiO2-SiO2 was characterized by using infrared spectroscope (IR), differential scanning calorimetry (DSC) and X-ray diffraction (XRD).Factors that affect the conversion of pyromellitic dianhydride under microwave radiation were discussed, such as molar ratio of reactants, dosage of catalyst, reaction time and microwave power. The optimum reaction conditions were confirmed by orthogonal experiments: microwave power is 300w, reaction time is 20 minutes,dosage of catalyst is 0.08% of pyromellitic dianhydride weight,molar ratio of isooctyl alcoholto pyromellitic dianhydride is 5.2:1,. Under these conditions the conversion of pyromellitic dianhydride is 99.5%. According to the rate equation of the unidirectional esterification under nonisothermal conditions, the kinetic parameters of the controlling step for TOPM synthesis from bis-2-ethylhexyl pyromellitate were calculated.