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

2001-04-03

Gupta, Yogendra (Department: 1751)

Cleaning compositions for solid surfaces, auxiliary compositions

Cleaning compositions or processes of preparing

Liquid composition

C510S407000, C510S338000

Reexamination Certificate

active

06211135

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to the purification of 2,2-dichloro-1,1,1,3,3,3-hexafluoropropane (i.e., CF
3
CCl
2
CF
3
, or CFC-216aa), its azeotropic compositions with hydrogen fluoride and their use.
BACKGROUND
CFC-216aa can be used to prepare 1,1,1,3,3,3-hexafluoropropane (i.e., CF
3
CH
2
CF
3
or HFC-236fa) by hydrogenolysis (see e.g., PCT International Publication No. 96/17813). The product, CF
3
CH
2
CF
3
, has numerous uses including use as a refrigerant and fire extinguishant.
CFC-216aa can be prepared from an appropriately substituted three-carbon precursor (e.g., perchloropropene) by chlorofluorination. Typically excess HF is used to obtain favorable reaction rates for conversion of the precursors to CFC-216aa. 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
CCl
2
CF
3
. The process comprises placing the mixture in a separation zone at a temperature of from about 0° 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 69 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The organic-enriched phase can be withdrawn from the bottom of the separation zone and subjected to distillation in a distillation column to recover essentially pure CF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
CCl
2
CF
3
. The distillate comprising HF and CF
3
CCl
2
CF
3
can be removed from the top of the distillation column, while CF
3
CCl
2
CF
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
CCl
2
CF
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
CCl
2
CF
3
to form an azeotrope or azeotrope-like composition with hydrogen fluoride, said composition containing from about 13.8 to 31.3 mole percent CF
3
CCl
2
CF
3
.
Also provided is a process for producing 1,1,1,3,3,3-hexafluoropropane from a mixture comprising HF and CF
3
CCl
2
CF
3
. The process is characterized by preparing CF
3
CCl
2
CF
3
which is essentially free of HF as indicated above, and reacting said CF
3
CCl
2
CF
3
with hydrogen.
Also provided is another process for producing 1,1,1,3,3,3-hexafluoropropane. This process is characterized by contacting an azeotrope of CF
3
CCl
2
CF
3
and HF as described above, with hydrogen, and reacting the CF
3
CCl
2
CF
3
with hydrogen in the presence of HF.


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: 5171901 (1992-12-01), Gassen et al.
patent: 5220083 (1993-06-01), Webster et al.
patent: 5364992 (1994-11-01), Manogue et al.
patent: 5481051 (1996-01-01), Rao
patent: 5902911 (1999-05-01), Rao et al.
patent: 6127585 (2000-10-01), Duzick et al.
patent: 0542290A1 (1992-11-01), None
patent: 0434408 (1990-12-01), None
patent: 0 434 408 A1 (1991-06-01), None
patent: 0 736 508 A1 (1996-10-01), None
patent: 05909885 (1992-04-01), None
patent: 0509449A2 (1992-04-01), None
patent: WO 96/17813 (1996-06-01), None
patent: WO9951555 (1999-10-01), None
patent: WO9951556 (1999-10-01), None

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