Processes for the purification and use of...

Details Processes for the purification and use of... Processes for the purification and use of...

1999-04-01

2004-01-13

Richter, Johann (Department: 1621)

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

Organic compounds

Halogen containing

C252S182110, C252S182120, C252S182320, C252S182130

Reexamination Certificate

active

06677493

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to the purification of 2-chloro-1,1,1,2,3,3,3-heptafluoropropane (i.e., CF
3
CClFCF
3
or CFC-217ba), its azeotropic compositions with hydrogen fluoride and their use in separation processes.
BACKGROUND
Hexafluoropropylene (i.e., CF
3
CF═CF
2
or HFP), a valuable fluoromonomer can be prepared by the hydrodehalogenation of CF
3
CClFCF
3
which itself can be prepared by the reaction of CF
3
CCl
2
CF
3
(CFC-216aa) with HF (see e.g., U.S. Pat. Nos. 5,057,634 and 5,068,472). Typically excess HF is used to obtain favorable reaction rates for the conversion of CFC-216aa to CFC-217ba. HF may be removed from the halogenated hydrocarbon components of the product mixture using conventional aqueous solution scrubbing techniques. However, the production of substantial amounts of scrubbing discharge can create aqueous waste disposal concerns.
There remains a need for processes that utilize HF in such product mixtures in an environmentally benign manner.
SUMMARY OF THE INVENTION
This invention provides a process for the separation of a mixture comprising HF and CF
3
CClFCF
3
. The process comprises placing the mixture in a separation zone at a temperature of from about −30° C. to about 100° C. and at a pressure sufficient to maintain the mixture in the liquid phase, whereby an organic-enriched phase comprising less than 50 mole percent HF is formed as the bottom layer and an HF-enriched phase comprising more than 90 mole percent HF is formed as the top layer.
The organic-enriched phase can be withdrawn from the bottom of the separation zone and subjected to distillation in a distillation column to recover essentially pure CF
3
CClFCF
3
. The distillate comprising HF and CF
3
CClFCF
3
can be removed from the top of the distillation column, while CF
3
CClFCF
3
which is essentially free of HF can be recovered from the bottom of the distillation column. If desired, the distillate can be recycled to the separation zone.
The HF-enriched phase can be withdrawn from the top of the separation zone and subjected to distillation in a distillation column. The distillate comprising HF and CF
3
CClFCF
3
can be removed from the top of the distillation column while essentially pure HF can be recovered from the bottom of the distillation column. If desired, the distillate can be recycled to the separation zone.
Also provided are compositions which comprise hydrogen fluoride in combination with an effective amount of CF
3
CClFCF
3
to form an azeotrope or azeotrope-like composition with hydrogen fluoride, said composition containing from about 38.4 to 47.9 mole percent CF
3
CClFCF
3
.
Also provided is a process for producing 1,1,1,2,3,3,3-heptafluoropropane from a mixture comprising HF and CF
3
CClFCF
3
. The process is characterized by preparing CF
3
CClFCF
3
which is essentially free of HF as indicated above, and reacting said CF
3
CClFCF
3
with hydrogen.
Also provided is another process for producing 1,1,1,2,3,3,3-heptafluoropropane. This process is characterized by contacting an azeotrope of CF
3
CClFCF
3
and HF as described above with hydrogen, and reacting the CF
3
CClFCF
3
with hydrogen in the presence of HF.
Also provided is a process for producing hexafluoropropene from a mixture of comprising HF and CF
3
CClFCF
3
. The process is characterized by preparing CF
3
CClFCF
3
which is essentially free of HF as indicated above, and dehalogenating the CF
3
CClFCF
3
.


REFERENCES:
patent: 4911792 (1990-03-01), Manzer et al.
patent: 5057634 (1991-10-01), Webster et al.
patent: 5068472 (1991-11-01), Webster et al.
patent: 5276225 (1994-01-01), Berthe
patent: 5364992 (1994-11-01), Manogue et al.
patent: 0 434 408 (1991-06-01), None
patent: 0 509 449 (1992-10-01), None
patent: 0 509 885 (1992-10-01), None
patent: 0 539 989 (1993-05-01), None
patent: 0 542 290 (1993-05-01), None
patent: WO 96/17813 (1996-06-01), None
The Condensed Dictionary, 8th edition, Van Nostrand Reinhold Co., p. 8 (1971).

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