Recovery of branched fluorinated emulsifiers
Described herein is a process for recovering a branched, ether-containing fluorinated emulsifier from an anion exchange resin by (1) contacting the anion exchange resin with a recovery fluid to form an eluate, the recovery fluid comprising an ammonium salt, water, and a water-miscible solvent, wherein the fluorinated emulsifier is of the formula: [Rf-(0-R′f)n-0-CF(CF3)-C(0)0-]i M+1; and (2) separating the anion exchange resin from the eluate.
1. A process for recovering a fluorinated emulsifier from an anion exchange resin, comprising
contacting the anion exchange resin with a recovery fluid to form an eluate, the recovery fluid comprising an ammonium salt, water, and a water-miscible solvent, wherein the fluorinated emulsifier is of the formula:
[Rf—(O—R′f) n —O—CF(CF 3 )—C(O)O − ] i M +i
wherein Rf is a fluorinated alkyl group comprising 1 to 5 carbon atoms; R′f is a divalent fluorinated group comprising 1 to 5 carbon atoms; n is 0, 1, 2, or 3; and M +i represents a cation having the valance i and i is 1, 2 or 3; and
separating the anion exchange resin from the eluate.
2. The process of claim 1 , wherein the fluorinated emulsifier is selected from at least one of: (i) n=0 and Rf═CF 3 (CF 2 ) 2 —; and (ii) n=1 and Rf═CF 3 — and R′f=—CF(CF 3 )CF 2 —.
3. The process of claim 1 , wherein the ammonium salt is of the formula:
(NR 4 ) n X
wherein each R is independently selected from H and an alkyl group comprising 1-5 carbon atoms; n is 1 or 2; and X is selected from F, Cl, Br, I, and an anionic organic residue.
4. The process of claim 1 , wherein the water-miscible solvent is an aliphatic alcohol having between 1-5 carbon atoms.
5. The process of claim 1 , wherein the recovery fluid is substantially free of a strong acid.
6. The process of claim 1 , wherein the recovery fluid has a pH greater than 6.
7. The process of claim 1 , wherein an amount of the ammonium salt is 0.2 to 5 wt % as compared to the total weight of the recovery fluid.
8. The process of claim 1 , wherein the contacting is conducted at a temperature of 20 to 80° C.
9. The process of claim 1 , wherein the % wt of the water-miscible solvent to the total weight of the recovery fluid is 50 wt % to 99 wt %.
10. The process of claim 1 , further comprising: removing the water and water-miscible solvent from the eluate to provide a concentrate; acidifying the concentrate to generate the free acid form of the fluorinated emulsifier; and distilling the free acid form of the fluorinated emulsifier.
11. The process of claim 1 , further comprising distilling eluate, concentrate, and/or the free acid form of the fluorinated emulsifier.
12. The process of claim 1 , further comprising regenerating the fluorinated emulsifier back to its original form.
13. The process of claim 1 , further comprising removing the water and water-miscible solvent from the eluate to provide a concentrate.