The Synthesis And Application Of Teflon-Supported Fluorous Catalysts

As a rare earth metal salt of perfluorooctane sulfonic acid, ytterbium perfluorooctanesulfonate [Yb(OPf)3] is a highly effective Lewis acid and the recovery of Yb(OPf)3is also an important part in the recovering of fluorous catalysts. The common methods of recovering fluorous catalysts include perfluorinated solvent method, fluorous solid-phase extraction (F-SPE), fluorous high performance liquid chromatography separation (F-HPLC) and so on. But these methods have some defects, such as the perfluorinated solvents are expensive and difficult to decompose, which is not eco-friendly, only small amount of fluorous catalysts can be recovered with F-SPE and the reuse of fluoride silica gel column is low. Polytetrafluoroethylene (Teflon) is a kind of white waxy thermoplastics. Compared with other plastics, Teflon has excellent overall performance and is widely used in modern industry. The fine powder of polytetrafluoroethylene (Teflon) has the excellent characteristics of Teflon, in addition, it has many unique properties, such as high crystallinity and dispersion, ease of uniformly mixing with other materials.In this paper, the ytterbium perfluorooctanesulfonate [Yb(OPf)3] was prepared by Yb2O3and KOPf, then Yb(OPf)3was supported on Teflon powder which has the average diameter of5μm, moreover, the influence of preparation conditions was studied and finally we obtained the optimized method which made the catalyst loading up to3%at0℃, stirring for2h with Teflon and Yb(OPf)3on the mass ratio of20:3. Subsequent experiments were carried out to evaluate the leaching of the catalyst in diverse solvents, which illustrated that the leaching of Yb(OPf)3from Teflon could be prevented in non-polar solvents. Considering the boiling points and solubilities of the solvents, we chose toluene as the suitable solvent and investigated the application and recycling of Yb(OPf)3-Teflon in amine-aldehyde condensation and acetalization reactions. Specifically, the amine-aldehyde condensation reaction employed benzaldehyde and o-phenylenediamine under the equal molar ratio at90℃for10h, providing yield of89.2%. The catalyst could be easily recovered and reused for5times without significant loss of activities. The acetalization reaction occurred at120℃for7h with benzaldehyde, ethylene glycol on the molar ratio of1:2, in yield of99.0%. The catalyst could be easily recycled for more than5times without apparent loss of activities.