Organic compounds -- part of the class 532-570 series – Organic compounds – Halogen containing
Patent
1997-10-08
1999-06-08
Siegel, Alan
Organic compounds -- part of the class 532-570 series
Organic compounds
Halogen containing
570159, C07C 1908
Patent
active
059106158
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to processes for the manufacture of hydrofluorocarbons (i.e., HFCs) and more particularly to processes for the production of 1,1,1,3,3,3-hexafluoropropane and/or 1,1,1,3,3-penta-fluoropropene.
BACKGROUND
Tetrafluoroethylene and hexafluoropropylene are commonly manufactured by high temperature pyrolysis. In these manufacturing processes, minor amounts of highly toxic perfluoroisobutylene are typically produced. This material can be reacted either with water (optionally in the presence of inert solvents for perfluoroisobutylene such as acetone or tetrahydrofuran) to form (CF.sub.3).sub.2 CHCOOH or with alkanols to form ethers. For example, perfluoroisobutylene may be reacted with methanol to convert it to two less toxic ether compounds, (CF.sub.3).sub.2 CHCF.sub.2 OCH.sub.3 (herein designated "ether A") and (CF.sub.3).sub.2 C.dbd.CFOCH.sub.3 (herein designated "ether B") (see, e.g., European Patent Publication No. 0 002 098). While (CF.sub.3).sub.2 CHCOOH, ether A and ether B are less hazardous than the perfluoro compound from which they are prepared, they still are generally disposed of as waste product. There is interest in developing means for productive use of (CF.sub.3).sub.2 CHCOOH and ether materials such as ether A and ether B.
SUMMARY OF THE INVENTION
A process is provided in accordance with this invention for producing 1,1,1,3,3,3-hexafluoropropane and/or 1,1,1,3,3-pentafluoropropene from at least one carboxy compound selected from (CF.sub.3).sub.2 CHCOOH and its water soluble salts (and optionally ether A, ether B, and/or certain of their alkyl analogs). The process comprises (1) providing a mixture comprising said at least one carboxy compound (and optionally said ether compound(s)) and water, said mixture having a pH of less than about 4, and (2) reacting the mixture provided in (1) at an elevated temperature of at least about 75.degree. C. The reaction of the mixture of said compound(s) and water may be employed in connection with a process for producing tetrafluoroethylene and/or hexafluoropropylene by pyrolysis, where by-product perfluoroisobutylene is reacted with water to produce .alpha.-hydroperfluoroisobutyric acid (and optionally an alkanol to produce the ether compound(s)).
DETAILED DESCRIPTION OF THE INVENTION
The present invention involves the discovery that (CF.sub.3).sub.2 CHCOOH and its water soluble salts can be effectively reacted with H.sub.2 O at acidic pH (i.e., pH less than about 4) to provide 1,1,1,3,3,3-hexafluoropropane (i.e., CF.sub.3 CH.sub.2 CF.sub.3 or HFC-236fa) and/or 1,1,1,3,3-penta-fluoropropene (i.e., CF.sub.3 CH.dbd.CF.sub.2 or HFC-1225zc). It has also been found that combinations of (CF.sub.3).sub.2 CHCOOH (and/or its water soluble salts) and ether compounds of the formula (CF.sub.3).sub.2 CHCF.sub.2 OR and of the formula (CF.sub.3).sub.2 C.dbd.CFOR where R is an alkyl group of the formula C.sub.n H.sub.2n-1 and n is an integer from 1 to 6 (e.g., CH3) can be effectively reacted with water at acidic pH to provide HFC-236fa and/or HFC-1225zc. Accordingly, HFC-236fa and/or HFC-1225zc are produced in accordance with this invention by the reaction of water and at least one carboxy compound selected from (CF.sub.3).sub.2 CHCOOH and its water soluble salts, or by the reaction of water and a combination of said carboxy compound(s) and one or more compounds of the formula (CF.sub.3).sub.2 CHCF.sub.2 OR (i.e., the alkylfluorobutyl ether reactants of this invention) and/or (CF.sub.3).sub.2 C.dbd.CFOR (i.e., the alkylfluorobutenyl ether reactants of this invention) wherein R is a C.sub.1 to C.sub.6 alkyl group as defined above (e.g., a mixture comprising the carboxy reactants, the alkylfluorobutyl ether reactants and the alkylfluorobutenyl ether reactants of this invention).
(CF.sub.3).sub.2 CHCF.sub.2 OR and (CF.sub.3).sub.2 C.dbd.CFOR can be produced by reacting perfluoroisobutylene with alkanols. A typical procedure for the production of alkylfluorobutyl ethers and alkylfluorobutenyl ethers is disclosed by R. J. Kos
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Jackson Scott C.
Resnick Paul Raphael
Swearingen Steven H.
E. I. Du Pont de Nemours and Company
Siegel Alan
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