The Study Of Direct Gas-phase Epoxidation And Heterogeneous Catalysis Of Hexafluoropropylene For The Synthesis Of Hexafluoropropylene Oxide

Hexafluoropropylene oxide(HFPO) is the most important epoxide which contains fluorine.It can be the intermediate product of many organic compounds which contain fluorine.For example,it can be used for the synthesis of fluorinated polyether,ion exchange resin,FS,fluorine rubber,HFA and so on.The existing methods for producing HFPO mainly include the H₂O₂ oxidation method, hypochlorous acid salt oxidation method,electro-chemistry method etc.But the problems are the complicated technique,high cost and enviormental pollution etc. Molecular oxygen is cheap and green.Direct gas-phase epoxidation of hexafluoropropylene(HFP) with molecular oxygen is the most direct and reasonable method.We adopt direct epoxidation of HFP with molecule oxygen using Ag/γ-Al₂O₃ catalyst mainly.The conversion of HFP is 15%and the selectivity to HFPO is 23.3%.The kinetics studies have been done for direct gas-phase epoxidation of HFP with molecule oxygen usingγ-Al₂O₃ supported silver catalyst.The results show that when the total flow rate of reactants is more than 150ml/h,and the granule diameter of the catalyst is bellow F2.5mm,both the internal and external diffusion have no effect on the reaction.In the BET adsorption plant,the adsorption conditions of HFP and O₂ have been studied at different temperatures.Their adsorption conditions are very different.The adsorption speed of HFP is very fast.There is obvious adsorption five minutes later.The adsorption quantity of HFP goes up quickly along with the rising of the adsorption pressure,and the adsorption quantity has no change with the temperatuer. The adsorption speed of oxygen is very slow.There is some adsorption an hour later.The adsorption quantity varies inconspicuously with the rising of pressure,and the adsorption quantity goes down a little with the rising of the temperature.The catalysts have been processed by the deposition-precipitation method.For the different precipitators,the effect of Na₂CO₃ is better than NaOH.And the precipitators of low concentration have higher conversions of HFP and selectivities to HFPO.When NaOH is used for the precipitator,at first the conversion changes little with the rising of the catalyst calcination temperature,at the same time selectivity rise slowly.But when the calcination temperature rises to 700℃,both conversion and selectivity descend quickly.When Na₂CO₃ is used for the precipitant,the conversion is rising higher and higher along with the rising of the calcination temperatures,while the selectivity to HFPO goes down at the temperature of 750℃.The catalyst of Ag/γ-Al₂O₃ has been modified by NaCl,KCl,RbCl,and CsCl. For the best result,the quantity of the addition of NaCl,KCl,RbCl,and CsCl are respectively 3%,2%,1%and 2%.Compared with the results of Ag/γ-Al₂O₃ catalyst without any modification,both the conversion of HFP and the selectivity to HFPO are improved.The selectivity to HFPO is the highest(51%) using Ag/γ-Al₂O₃ catalyst modified by 2%CsCl.The FeAlPO-5 and CuAlPO-5 have been synthesized,and the best conditions have been found.The initial synthesis experiment has been done with them.The activity of the FeAlPO-5 and CuAlPO-5 are very low.No HFPO has been found. (Maybe there is a little HFPO,but it is included in the peaks of the materials.)The Cu₂(OH)PO₄ has been synthesized,and the best conditions have been found.The initial synthesis experiment has been done with it.The activity of the Cu₂(OH)PO₄ is lower than the FeAlPO-5 and CuAlPO-5.There is only a little carbon dioxide,and no HFPO has been found.