A Study On The Preparation Of Hexafluoropropylene Oligomer

Hexafluoropropylene oligomer mainly includes hexafluoropropylene dimer and hexafluoropropylene trimer.It was prepared from hexafluoropropene by oligomerization.Hexafluoropropylene oligomer has good thermodynamic and chemical stability.It can be used as an intermediate for the preparation of perflurane,fluorinated surfactants,lithium battery electrolytes,pharmaceutical pesticides and polymers,as well as liquid cooling media and media in special environments.With the further research of hexafluoropropylene oligomer and its derivatives,it shows great development prospect and application potential.In this thesis,a liquid phase oligomerization method is used to prepare hexafluoropropylene dimer and hexafluoropropylene trimer.Through the exploration of the reaction process method,a process method suitable for industrial production of hexafluoropropylene oligomer has been developed.The main research contents are as follows:(1)A study on the preparation of hexafluoropropylene dimer.The effect of solvent,catalyst,pressure,temperature,etc.on the reaction of preparing hexafluoropropylene dimer was explored.Through research,it is found that the anprotic polar solvent acetonitrile is beneficial to the formation of hexafluoropropene dimer,potassium fluoride and quaternary ammonium salt can catalyze the oligomerization reaction,and proper pressure can increase the oligomerization rate and the yield of hexafluoropropene dimer,low temperature is beneficial to the selective formation of hexafluoropropene dimer.The optimal reaction conditions for preparing hexafluoropropylene dimer are: acetonitrile was used as solvent,the molar ratio of catalyst was potassium fluoride: octadecyl trimethyl ammonium bromide=1:0.15,the concentration of potassium fluoride is 0.34 mol/L,the reaction pressure is 0.4 MPa,and the reaction temperature is 20 ℃.Under these reaction conditions,the content of hexafluoropropylene dimer D-1 in the oligomerization product is 91.3%,the conversion of hexafluoropropene is 75.5%,and the yield of hexafluoropropene dimer is68.9%;At the same time,the effect of solvent,catalyst ratio and reaction time etc.on the isomerization of dimer D-1 to D-2 with high chemical reaction activity was explored.It is found that the aprotic polar solvent dimethyl sulfoxide can be used as the solvent for the isomerization reaction,The catalytic system of potassium fluoride and cetyltrimethyl ammonium bromide can catalyze the reaction.The optimal reaction conditions for the isomerization reaction of hexafluoropropylene dimer D-1 are: dimethyl sulfoxide as the solvent,the volume ratio of solvent to D-1 is 1:1.5,and the catalyst molar ratio is potassium fluoride: cetyltrimethylammonium bromide=1:0.1,the concentration of potassium fluoride is 0.17 mol/L,reaction at 40 ℃ for 10 h,the conversion rate of hexafluoropropylene dimer D-1 is 95.4%,the yield of D-2 is 94.4%.(2)A study on the preparation of hexafluoropropylene trimer.The effect of solvent,catalyst,pressure,temperature,etc.on the reaction of preparing hexafluoropropylene trimer was explored.Through research,it is found that the aprotic polar solvent N,N-dimethylacetamide is beneficial to the formation of hexafluoropropylene trimer.Appropriate pressure can increase the oligomerization reaction rate and the yield of hexafluoropropylene trimer.The medium and high temperature is conducive to the selective formation of hexafluoropropylene trimer.Adding the cocatalyst octadecyl trimethyl ammonium bromide can effectively increase the conversion rate of hexafluoropropylene and the yield of hexafluoropropylene trimer.The optimal reaction conditions for preparing hexafluoropropylene trimer are: N,N-dimethylacetamide as solvent,the molar ratio of catalyst is potassium fluoride: octadecyl trimethyl ammonium bromide=1:0.3,the concentration of potassium fluoride is 0.11 mol/L,the reaction pressure is 0.35 MPa,and the reaction temperature is 80 ℃.Under this reaction condition,the content of hexafluoropropylene trimer in the oligomerization product is 93.2%,the conversion rate of hexafluoropropylene is 96.5%,and the yield of hexafluoropropylene trimer is 89.9%.