Process for producing fluorinated aliphatic compounds

Details Process for producing fluorinated aliphatic compounds Process for producing fluorinated aliphatic compounds

2001-03-14

2003-12-16

Richter, Johann (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Halogen containing

C570S153000, C526S243000, C526S915000

Reexamination Certificate

active

06664431

ABSTRACT:

FIELD OF THE ART
The present invention relates to the fluoroorganic chemistry, particularly to a process for producing fluorinated aliphatic compounds by pyrolysis of perfluoro- and poly-fluorocarboxylic acids and their derivatives—halides and esters. The products of the pyrolysis, depending on the conditions under which it is carried out, are fluorinated olefins, perfluoroalkylvinyl ethers and polyfluoroalkanes. Fluorinated olefins and perfluoroalkylvinyl ethers are used as starting materials for obtaining polymer materials with improved operational characteristics, lubricating oils, elastomers, ion-exchange membranes for the electrolysis of aqueous solutions of alkali metal halides, etc. Polyfluoroalkanes, owing to their chemical inertness and thermal stability, find application as components of mix coolants, actuating fluids of thermocompressors, porophores in manufacturing foamed plastics and polyurethane foams, gas dielectrics, propellants, inert solvents, reagents for dry etching in manufacturing integrated circuits, and also in formulations of fire-extinguishing means.
At present a necessity is felt in the provision of an industrial process for producing fluorinated olefins, polyfluoroalkanes, perfluoroalkylvinyl ethers from different available organofluorine compounds under relatively mild reaction conditions with a high yield.
PRIOR ART
It is known that polyfluoroalkanes, particularly such as promising ozone-safe Freons 125, 227ea, are produced mainly by the hydrofluorination of perfluoroolefins—tetrafluoroethylene (TFE) and hexafluoropropylene (HFP), the production of which involves definite difficulties. TFE is explosion-hazardous, highly toxic, and self-polymerizes. TFE and HFP are produced by the high-temperature pyrolysis of chlorine- and fluorine-containing hydrocarbons, whose production in accordance with the decision of the Montreal Protocol concerning substances destroying the ozone layer is reduced because they deteriorate considerably the ecological situation. Therefore the possibility of obtaining polyfluoroalkanes (Freon 125, 227ea and the like) and olefins as such (TFE, HFP) from other available starting materials, namely, perfluoro- and polyfluorocarboxylic acids and their derivatives by a more simple process is a very urgent problem. The claimed process solves this problem.
It is known that in the pyrolysis of esters of perfluoro-alkoxycarboxylic acids of the formula
ICF
2
CF
2
OQCF(CF
3
)COOR,
where
Q is OCF
2
CF(CF
3
)[OCF(CF
3
)CF
2
]
m
, [OCF(CF
3
)CF
2
]
n
;
m is 0 to 7;
n is 1 to 4;
R is (C
1
-C
6
) alkyl
vinyl ethers are formed above a layer of carbonate, phosphate, sulfite, sulfate of an alkali or alkali-earth metal (U.S. Pat. No. 4,594,458, C07C 43/16, publ. 10.06.86). In this process, from an ester first a salt is obtained by treating NaHCO
3
in a methanol solution, and then the salt is subjected to pyrolysis at 140-260° C. In accordance with this process, perfluoro (8-iodo-4-methyl-3,6-dioxaoctene-1) is obtained with a yield of 71.8%.
A disadvantage of this process is the necessity of carrying out the intermediate step of obtaining an alkali metal salt and the necessity of drying this salt thoroughly, because the presence of moisture leads to the formation of by-products. Furthermore, toxic, fire- and explosion-hazardous methanol is used for carrying out the reaction.
In the pyrolysis of ethyl esters of pentafluoropropionic and heptafluorobutyric acid at 350-413° C. and a pressure of about 8-80 gPa tetrafluoroethylene and hexafluoropropylene are formed, respectively, with a yield of about 30%, as well as an insignificant amount of pentafluorethane and heptafluoropropane (Int. J. Chem. Kinet., 1982, 14, No. 3, 291).
Known in the art is pyrolysis of polyfluoroalkoxyperfluoropropionic acid fluorides on sodium carbonate at 200-220° C., which gives polyfluoroalkylperfluorovinyl ethers with a yield of 85-91% (Zhurnal Organicheskoi Khimii, 1978, 14, No. 3, 487). The pyrolysis proceeds in accordance with the following scheme:
R
f
CF(CF
3
)OCF(CF
3
)COF→R
f
CF(CF
3
)OCF═CF
2
,
where R
f
is CF
3
CF
2
, CF
3
(CF
2
)
3
, CICF
2
CF
2
.
Na
2
CO
3
is a reagent which is consumed in the process of the synthesis, forming NaF.
In the pyrolysis of polyfluorocarboxylic acid halides of the formula XC
n
F
2n
COI (wherein X is H, F; n>1; I is a haloid) at 200-500° C., fluorolefins of the formula XC
n
F
2n−1
are formed (U.S. Pat. No. 3,020,321, 260-653.3, publ. 06.02.62). The reaction is carried out with oxides of Group IIA metals and silicon or with oxygen-containing salts of Group IA and Group IIA metals of the Periodic System.
The disadvantages of this process are a high reaction temperature (mainly 380° C.) and direct participation of oxides and oxygen-containing salts in the process with the formation of inorganic fluorides, which makes the process unstable.
Decarbonylation of polyfluorocarboxylic acid fluorides is known in the art, which leads to obtaining polyfluoroalkanes in accordance with the following scheme:
H(CF
2
)
n
COF→H(CF
2
)
n
F.
The reaction proceeds in the presence of a catalyst: anhydrous aluminum oxide (RU 659555, C07C 19/08, publ. 30.04.79) or under heating acyl fluoride with antimony pentafluoride (U.S. Pat. No. 3,555,100, C07C 19/08, publ. 12.01.71). As a result, 1-hydroperfluorohexane was obtained with a yield of 87-93%.
The prior-art processes cited above depend on starting materias, because monohydroperfluoroalkanes can be produced only from corresponding monohydroperfluorocarboxylic acid fluorides, which are not always available. They do not allow selective introduction of hydrogen into the carbon chain either.
High-temperature decarboxylation (620° C. and 120 mm Hg) of 2-hydroperfluorobutyric acid gives 2-hydropentafluoropropylene with the yield of 92% (2-Hydropentafluoro propylene. Khim. Promyshl. Ser. Prikladnaya Khimiya, Moscow, NIITEK-hiM, 1979, pp. 1-2). The reaction proceeds in accordance with the following scheme:
CF
3
CHFCF
2
COOH→CF
3
CH═CF
2
.
Decarboxylation of &agr;-hydrohexafluoroisobutyric acid in dimethyl formamide gives 2,2-dihydrohexafluoropropane with the yield of 65% (Izv. AN SSSR, Ser. Khimiya, 1977, No. 5, 1112).
The reaction proceeds in accordance with the following scheme:
(CF
3
)
2
CHCOOH→CF
3
CH
2
CF
3
.
With the help of this process only dihydroperfluoroalkanes can be produced.
It is known that decarboxylation of fluorocarboxylic acids of the formula R(CFR
1
)
n
(CFR
2
)
m
OCF(CF
2
X)COOH, where R is SO
2
Z, POZ
2
, COZ; Z is OR
3
, F, Cl, Br, I; R
3
is alkyl or aryl; R
1
and R
2
each are F, Cl, perfluoro- or chlorofluoroalkyl; X is Cl, Br, I; n is from 0 to 3; m is from 0 to 3, in the presence of an activator Na
2
CO
3
, ZnO or SiO
2
in an organic solvent (mono-, di- or tetraglyme) at 50-150° C. makes it possible to obtain corresponding vinyl ethers of the following formula: R(CFR
1
)
n
(CFR
2
)
m
OCF═CF
2
(U.S. Pat. No. 4,358,412, C07F 9/113, publ. 09.11.82).
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide a universal industrial process for producing fluorinated aliphatic compounds with a high yield from available starting materials.
Another object of the present invention is to provide a process for producing fluorinated aliphatic compounds that are fluorinated olefins and perfluoroalkylvinyl ethers, by pyrolysis of perfluoro- and polyfluorocarboxylic acids, their halides and esters.
Still another object of the present invention is to provide a process for producing fluorinated aliphatic compounds that are polyfluoroalkanes, by pyrolysis of perfluoro- and polyfluorocarboxylic acids, their halides and esters in the presence of hydrogen fluoride.
Said objects are accomplished by the present invention, wherein a process for producing fluorinated aliphatic compounds is disclosed, consisting in carrying out pyrolysis of perfluoro- and polyfluorocarboxylic acids and their derivatives selected from the acid halides and esters, on a catalyst consisting of a carrier, most preferably selected from the series comp

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