Development of a continuous process for the production of hexafluoropropyl methyl ether.
Partially fluorinated dialkyl ethers are valuable intermediates for organofluorine syntheses. These compounds can be used for the preparation of perfluoroacrylic acids or the anhydrides, amides and esters thereof. They also serve as very effective solvents, particularly for the extraction of essential oils. A continuous process for producing 1,1 ,2,3,3,3-hexafluoropropyl methyl ether by reacting a liquid mixture of potassium hydroxide and methanol with gaseous hexafluoropropene in one or more microstructured devices was developed. The reaction of hexafluoropropene and potassium methoxide is highly exothermic, with higher operating temperatures favouring the formation of hexafluoropropyl methyl ether. The reactants are contacted for a prescribed time within a reaction zone having a high heat transfer area to reaction volume ratio and in intimate contact with a cooling medium, facilitating efficient dissipation of the exothermic reaction heat. The product mixture is contacted with water at below ambient temperature to extract the residual methanol and the raffinate is further purified by means of conventional distillation. The water and methanol mixture is fed to a distillation column that recovers methanol at a purity of 99%. The HME-methanol mixture is fed to another distillation column which produces HME at 98% purity. The methanol recovered from both distillation columns is recycled to the start of the process. The synthesis of hexafluoropropyl methyl ether using the aforementioned process was demonstrated experimentally using a falling film microreactor. Quadratic response surface methodology was used to probe for optimal reaction conditions for the yield of hexafluoropropyl methyl ether as well as the purity of the raw product.