Method for the manufacture of fluorinated compounds

Abstract

A method for the manufacture of perfluorinated compounds is herein disclosed. In particular, the method is useful for the manufacture of perfluorooxyalkyl carboxylic acid salts which can be used as surfactants. The method envisages the fluorination or a fluoroformate of an alcohol comprising a CH.sub.2OCH.sub.2-moiety at a temperature equal to or higher than 20 C. and allows obtaining high yields and selectivity.

Claims

1. A method for manufacturing a fluorinated compound, the method comprising: fluorinating a fluoroformate (I) with elemental fluorine, optionally in the presence of a (per)haloolefin, at a temperature of at least 20 C., to obtain the corresponding perfluorinated fluoroformate (III) and, optionally, cleaving the perfluorinated fluoroformate (III); wherein fluoroformate (I) is the fluoroformate of an alcohol (II) comprising at least one CH.sub.2OCH.sub.2 moiety.

2. The method according to claim 1 wherein alcohol (II) complies with formula (II-A):
R.sup.1CH.sub.2OH (II-A) wherein R.sup.1 is an optionally fluorinated straight or branched alkyl group comprising at least one ethereal oxygen atom comprised in a CH.sub.2OCH.sub.2 moiety and, optionally, one or more further ethereal oxygen atoms and/or cycloalkylene moieties.

3. The method according to claim 2 wherein alcohol (II) complies with formula (II-B):
R.sup.2CH.sub.2OCH.sub.2(CH.sub.2).sub.nOH (II-B) wherein: R.sup.2 is an optionally fluorinated straight or branched alkyl group, optionally comprising at least one ethereal oxygen atom and/or cycloalkylene moiety and n is an integer ranging from 1 to 10.

4. The method according to claim 3 wherein n ranges from 1 to 4.

5. The method according to claim 4 wherein alcohol (II) is selected from the group consisting of: CH.sub.3OCH.sub.2CH.sub.2OH CH.sub.3CH.sub.2OCH.sub.2CH.sub.2OH CH.sub.3CH.sub.2CH.sub.2OCH.sub.2CH.sub.2OH CH.sub.3CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2OCH.sub.2CH.sub.2OH CH.sub.3OCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OH CH.sub.3CH.sub.2OCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OH CH.sub.3CH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OH CH.sub.3CH.sub.2CH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OH CH.sub.3OCH.sub.2CH.sub.2CH.sub.2OCH.sub.2CH.sub.2OH CH.sub.3OCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OH CH.sub.3CH.sub.2OCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OH CH.sub.3CH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OH and CH.sub.3CH.sub.2CH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OH.

6. The method according to claim 1, wherein the temperature ranges from 20 C. to 100 C.

7. The method according to claim 6 wherein the temperature ranges from 20 C. to 50 C.

8. The method according to claim 1, wherein cleaving the perfluorinated fluoroformate (III) is carried out by thermolysis in the presence of metal fluorides.

9. The method according to claim 1, wherein cleaving the perfluorinated fluoroformate (III) is carried out by treatment with a hydroxide.

10. The method according to claim 9 wherein the hydroxide complies with formula (f-1):
M.sup.+OH.sup.(f-1) wherein M represents a metal of group (I) of the periodic table or an ammonium group of formula NR.sup.N.sub.4, wherein R.sup.N, equal to or different at each occurrence, is hydrogen or a C.sub.1-C.sub.6 hydrocarbon group.

11. The method according to claim 1, wherein fluorinating the fluoroformate (I) is carried out in a microreactor.

12. The method according to claim 6, wherein cleaving the perfluorinated fluoroformate (III) is carried out by thermolysis in the presence of metal fluorides.

13. The method according to claim 6, wherein cleaving the perfluorinated fluoroformate (III) is carried out by treatment with a hydroxide.

14. The method according to claim 6, wherein fluorinating the fluoroformate (I) is carried out in a microreactor.

15. The method according to claim 3, wherein the temperature ranges from 20 C. to 100 C.

16. The method according to claim 15, wherein the temperature ranges from 20 C. to 50 C.

17. The method according to claim 3, wherein cleaving the perfluorinated fluoroformate (III) is carried out by thermolysis in the presence of metal fluorides.

18. The method according to claim 3, wherein cleaving the perfluorinated fluoroformate (III) is carried out by treatment with a hydroxide.

19. The method according to claim 18 wherein the hydroxide complies with formula (f-1):
M.sup.+OH.sup.(f-1) wherein M represents a metal of group (I) of the periodic table or an ammonium group of formula NR.sup.N.sub.4, wherein R.sup.N, equal to or different at each occurrence, is hydrogen or a C.sub.1-C.sub.6 hydrocarbon group.

20. The method according to claim 3, wherein fluorinating the fluoroformate (I) is carried out in a microreactor.

Description

EXPERIMENTAL SECTION

(1) Materials and Methods

(2) Commercially available diethylenglycol monoethyl ether (CH.sub.3CH.sub.2OCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OH), 1,2,3,4-tetrachloro hexafluorobutane, hexafluoropropene (CF.sub.3CFCF.sub.2), KOH and any other chemicals were used as received by the manufacturer.

(3) A Falling Film Microreactor (FFMR) supplied by Fraunhofer Institute for Chemical Technology ITC, Branch IC-IMM (Institut fr Mikrotechnik Mainz GmbH) was used, having a surface to volume ratio of about 20000 m.sup.2/m.sup.3 and comprising five U-shaped trenches (each having a volume of about 80 microliters) and a sealed gas chamber located on the top of the trenches. The microreactor was exercised in co-current, i.e. the reactants were flowed from the top inlet to the bottom outlet. Also, the inlets of the microreactor were connected to gas feed line and to a liquid feed line. The microreactor was properly cooled or heated as disclosed in detail in the following examples using a heat transfer fluid. In addition, before entering the microreactor, both the gas and the liquid were properly cooled or heated using two heat exchangers. The exhaust coolant and the biphasic flow containing the products left the microreactor via two separate ports.

(4) .sup.19F-NMR and .sup.1H-NMR analyses were carried out on a Varian Mercury 300 MHz spectrometer using tetramethylsilane (TMS) as internal standard. .sup.19F-NMR analyses were performed on a Varian Mercury 300 MHz spectrometer using CFCl.sub.3 as internal standard.

Example 1Synthesis of CF.SUB.3.CF.SUB.2.OCF.SUB.2.CF.SUB.2.OCF.SUB.2.COO.SUP..K.SUP.+

(5) Step a Synthesis of C.sub.2H.sub.5OC.sub.2H.sub.4OC.sub.2H.sub.4OC(O)F

(6) In a 250 ml stainless steel reactor equipped with a mechanical stirrer, 100 g diethylenglycol monoethyl ether (CH.sub.3CH.sub.2OCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OH) were loaded and maintained at 0 C. by an external cooling bath. 4.0 NI/h Carbonyl difluoride (COF.sub.2), synthesized by reaction between 4.0 NI/h of F.sub.2 and 5.0 NI/h CO in a tubular reactor at 150 C., diluted with 10 NI/h He were fed in the reactor through an inlet tube. COF.sub.2 conversion was checked by gas chromatography (GC) analysis. After 5 h, the feeding of COF.sub.2 was stopped and the excess dissolved in the crude reaction product was vented away by inert gas. The crude product was analysed by .sup.19F-NMR and .sup.1H-NMR; the analyses showed complete conversion of the starting alcohol and a selectivity in the desired fluoroformate higher than 98%.

(7) Steps b and cSynthesis of CF.sub.3CF.sub.2OCF.sub.2CF.sub.2OCF.sub.2COO.sup.K.sup.+

(8) Step b. In a 250 ml stainless steel reactor equipped with a mechanical stirrer, two inlet tubes (tube A for fluorine and tube B for the fluoroformate from Step 1) and a condenser kept at 40 C., 100 ml 1,2,3,4-tetrachloro hexafluorobutane were loaded and maintained at 40 C. by an external heating bath; then elemental fluorine (5.0 NI/h) diluted with He (15.0 NI/h) was fed into the reactor by inlet tube A. After 30 minutes, 3.1 g/h of the fluoroformate from Step 1 (equivalent to 2.8 g/h pure fluoroformate) were fed in the reactor through inlet tube B. After 6 hours the feeding of the fluoroformate was interrupted and the reactor was cooled to 0 C. When this temperature was reached, 0.3 NI/h CF.sub.3CFCF.sub.2, diluted with 1.5 NI/h He, were fed into the reactor through inlet tube B for 30 minutes, to convert all residual hydrogen atoms.

(9) Step c. The resulting crude mixture was discharged in 400 g of 10% aqueous KOH to convert the perfluoroformate in the desired carboxylate and to neutralize all residual acidity. The two resulting phases were separated and the aqueous one was quantitatively analysed via .sup.19F-NMR with an internal standard. CF.sub.3CF.sub.2OCF.sub.2CF.sub.2OCF.sub.2COO.sup.K.sup.+ was obtained with a 71% yield.

Example 2 (Comparative Example)Synthesis of CF.SUB.3.CF.SUB.2.OCF.SUB.2.CF.SUB.2.OCF.SUB.2.COO.SUP..K.SUP.+ at Low Temperature

(10) Example 1 was repeated, with the difference that in Step b) the temperature was kept at 20 C. for the whole reaction time. Quantitative .sup.19F-NMR analysis of the aqueous phase showed a CF.sub.3CF.sub.2OCF.sub.2CF.sub.2OCF.sub.2COO.sup.K.sup.+ yield of 28%.

Example 3Synthesis of CF.SUB.3.CF.SUB.2.OCF.SUB.2.CF.SUB.2.OCF.SUB.2.COO.SUP..K.SUP.+ in a Falling Film Microreactor (FFMR) in the Presence of a Solvent

(11) The formate of formula C.sub.2H.sub.5OC.sub.2H.sub.4OC.sub.2H.sub.4OC(O)F was synthesised according to Example 1, Step a).

(12) Step b) was carried out in a FFMR, according to the following procedure. Fluorine (5.0 NI/h), diluted with He (15.0 NI/h) in a 1:3 volume ratio was fed into the reactor by an inlet tube (tube A), while 3.1 g/h of the formate from Example 1, Step a), mixed with 100 g/h 1,2,3,4-tetrachloro hexafluorobutane were fed in the reactor through an inlet tube B. The reactor was kept at a temperature of 40 C. by means of an external heating bath. The reaction product was condensed in a condenser cooled at 40 C. and the resulting liquid product was collected in a 500 ml stainless steel reactor equipped with a mechanical stirrer. After 6 hours the feeding of fluoroformate was interrupted, and the stainless steel reactor was cooled to 0 C. After this temperature was reached, 0.3 NI/h CF.sub.3CFCF.sub.2 diluted with 1.5 NI/h He were fed into the reactor by an inlet tube C and 5 NI/h F.sub.2 diluted with He were fed by inlet tube D for 30 minutes to convert all residual hydrogen atoms. The resulting crude product was discharged in 400 g of 10% aqueous KOH to convert the perfluoroformate in the desired carboxylate and to neutralize all residual acidity. The two resulting phases were separated and the aqueous one was quantitatively analyzed via .sup.19F-NMR with an internal standard. CF.sub.3CF.sub.2OCF.sub.2CF.sub.2OCF.sub.2COO.sup.K.sup.+ was obtained with a 80% yield.

Example 4Synthesis of CF.SUB.3.CF.SUB.2.OCF.SUB.2.CF.SUB.2.OCF.SUB.2.COO.SUP..K.SUP.+ in a Falling Film Microreactor (FFMR) in the Absence of Solvent

(13) Example 3 was repeated, with the difference that fluorine (5.0 NI/h), diluted with He (15.0 NI/h) in a 1:3 volume ratio, was fed in the microreactor through inlet tube A, while 3.1 g/h of the fluoroformate from Example 1, Step a) was fed in the reactor through an inlet tube B. At the end of the reaction, the resulting mixture was worked-up in the same way as in Example 3, then 0.3 NI/h CF.sub.3CFCF.sub.2, diluted with 1.5 NI/h He were fed in the reactor through an inlet tube C and 5 NI/h F2 diluted with 5.0 NI/h was fed through an inlet tube D for 30 minutes until complete fluorination. After treatment with 10% aqueous KOH, CF.sub.3CF.sub.2OCF.sub.2CF.sub.2OCF.sub.2COO.sup.K.sup.+ was obtained with a 75% yield.