Polymeric acid catalysis
A highly fluorinated polymer is very useful as an acid catalyst. The highly fluorinated polymer has at least two repeating unit types that are the polymerized derivatives of a perfluorinated cyclic or cyclizable compound and a highly fluorinated vinyl ether compound having a sulfur containing functional group. The polymer can be formed by radical copolymerization of the fluorinated monomers with the sulfur-containing functional group in sulfonyl fluoride form (—SO 2 F) that is subsequently converted to sulfonic acid form (—SO 3 H). The highly fluorinated polymer can be used to advantage in a solution comprising an aprotic, polar organic solvent that has a dielectric constant of at least 15 and preferably is free of hydroxyl functional groups. Suitable solvents are those in which the polymer is soluble to at least 1 wt %. Hydroxyl group-containing protic, polar organic solvents are less preferred. The highly fluorinated polymer can be an effective heterogeneous catalysts when used in form of solid, fine particles insolubly suspended in or in contact with a fluid reaction mass.
1. A method of increasing acidity comprising the steps of
(A) providing a substance to be highly acidified
(B) providing a fluorinated polymeric acid formed by copolymerizing monomers comprising (i) a perfluorinated cyclic monomer and, (ii) a fluorinated vinyl ether monomer that contains a pendant sulfonic acid moiety, and
(C) intimately mixing the substance to be highly acidified with the fluorinated polymeric acid for a duration effective to increase acidity of the substance to be highly acidified,
in which the perfluorinated cyclic monomer forms in the fluorinated polymeric acid a repeating unit of the following formula
in which R f4 and R f5 are each independently a fluorine atom or a C 1-5 perfluoroalkyl group, and R f8 is a fluorine atom, a C 1-5 perfluoroalkyl group or a C 1-5 perfluoroalkoxy group.
2. The method of claim 1 in which the repeating unit formed by the perfluorinated cyclic monomer has the following formula in which R f16 and R f17 each independently is a fluorine atom or a trifluoromethyl group, and
in which the fluorinated vinyl ether monomer forms in the fluorinated polymeric acid a repeating unit formed by the fluorinated vinyl ether monomer of the following formula
in which the R f group is a linear or branched, perfluoroalkyl group containing 1 to 10 carbon atoms, and optionally substituted by one or more ether oxygen atoms.
3. The method of claim 2 in which the fluorinated polymeric acid has the following formula wherein y is zero or one, and in which m and n are the respective mole fractions of the repeating units in the fluorinated polymeric acid of the perfluorinated cyclic monomer and the fluorinated vinyl ether monomer
4. The method of claim 1 in which during the intimately mixing step, the substance to be highly acidified is a fluid and the fluorinated polymeric acid is present in a solid state of matter.
5. The method of claim 4 in which the fluid is a liquid, the fluorinated polymeric acid is present as fine particles, and the intimately mixing step comprises dispersing the fine particles substantially uniformly in the liquid.
6. The method of claim 4 in which the substance comprises reactants of an acid-catalyzed chemical reaction mass.
7. The method of claim 1 which further comprises dissolving the fluorinated polymeric acid to at least about 1 wt % in a solvent to form an acid solution, and intimately mixing the substance to be highly acidified with the acid solution.
8. The method of claim 7 in which the solvent is polar, aprotic and has a dielectric constant of at least about 15.
9. The method of claim 7 in which the solvent is free of hydroxyl functional groups.
10. The method of claim 7 in which the solvent is a compound containing hydroxyl functional groups selected from the group consisting of water and C 1-8 alcohols.
11. The method of claim 7 in which the solvent is water.
12. The method of claim 1 in which the monomers forming the fluorinated polymeric acid further comprise additional comonomers.
13. The method of claim 12 in which the additional comonomers are selected from the group consisting of tetrafluoroethylene, trifluoroethylene, chlorotrifluoroethylene, vinyl fluoride and vinylidene fluoride.
14. The method of claim 2 which comprises converting sulfonyl fluoride of repeating units formed by the fluorinated vinyl ether monomer to an acid form of the following formula
15. The method of claim 3 in which the sum of m plus n is 1.0.