Organic compounds -- part of the class 532-570 series – Organic compounds – Halogen containing
Reexamination Certificate
1998-02-17
2001-09-18
Siegel, Alan (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Halogen containing
Reexamination Certificate
active
06291727
ABSTRACT:
FIELD OF THE INVENTION
The instant invention relates to azeotropic or azeotrope-like compositions of hydrofluoric acid with at least one of 1,1-dichloroethane, 1-chloro-1-fluoroethane and 1,1-difluoroethane. The invention also relates to processes for separating hydrofluoric acid from a mixture comprising hydrofluoric acid and one or more 1,1-dihaloethane.
BACKGROUND OF THE INVENTION
Dihaloethanes can be manufactured by using a wide range of processes. Examples of such processes are described in Golubev et al. (Union of Soviet Socialist Republics Inventor Certificate No. 341788). Golubev used hydrofluoric acid to separate 1,1-difluoroethane from vinyl chloride by reacting vinyl chloride with hydrofluoric acid, and then distilling 1,1-difluoroethane. Guofei et al. (Chinese Patent Application Publication No. 1069019a) use both a water scrubber and caustic scrubber to remove acid from a 1,1-difluoroethane product stream. There is no disclosure of separating the dihaloethanes from each other.
Tatsuya et al. (Japanese Patent Publication Kokoku JP-48-16487) describe a method for purifying 1-chloro-1- fluoroethane by absorbing and dissolving the absorbed material in a chlorinated hydrocarbon.
Mao et al (Canadian Patent Application Publication No. 1,074,434 A) use a photochlorination reaction to purify 1,1-difluoroethane.
Brock et al. (U.S. Pat. No. 3,190,930) discloses a process for producing 1-1-difluoroethane from acetylene.
The disclosure of the above-identified documents is hereby incorporated by reference.
SUMMARY OF THE INVENTION
Difluoroethane (CHF
2
CH
3
or HFC-152a) may be used either alone or in blends with other fluorocarbons as a refrigerant, blowing agent, propellant, an aerosol, as an intermediate product in the manufacture of other fluorinated compounds including vinyl fluoride, among other applications. Hydrofluorocarbons (HFCs) such as 1,1- difluoroethane are environmentally acceptable replacements for certain chlorofluorocarbons (CFCs) and hydrocarbons.
A difluoroethane containing mixture can be made by any suitable method such as by reacting chloroethene (CH
2
═CHCl or vinyl chloride) with hydrofluoric acid, e.g., a method described in the aforementioned U.S. and non-U.S. Patents. Intermediates or by-products to this reaction may include 1-chloro-1-fluoroethane (CHClFCH
3
or HCFC-151a) and 1,1- dichloroethane (CHCl
2
CH
3
or HCC-150a). HCFC-151a and HCC-150a are also potential intermediate products in the manufacture of other fluorocarbon compounds, e.g., vinyl fluoride.
One aspect of the present invention relates to the discovery of azeotropic or azeotrope-like compositions containing effective amounts of hydrofluoric acid with at least one of 1,-dichloroethane, 1-chloro-1-fluoroethane and 1,1-difluoroethane.
The aforementioned azeotropic or azeotrope-like compositions can be employed in another aspect of the invention which relates to a process for separating HF from first mixture comprising HF and at least one compound selected from the group of 1,1-dichloroethane, 1-chloro-1-fluoroethane, and 1,1-difluoroethane. This process broadly comprises (1) distilling the first mixture to substantially remove all materials that have either (a) a lower boiling point than the lowest boiling azeotrope composition containing HF and said at least one compound or (b) a higher boiling point than the highest boiling azeotrope composition containing HF and said at least one compound thereby forming a second mixture; and (2) distilling the second mixture to recover HF as an azeotropic or azeotrope-like composition containing HF and said at least one compound. This aspect of the instant invention solves problems associated with conventional practices by providing an expedient process for obtaining purified HFC-152a.
If desired the HF can be recovered or separated from the azeotropic or azeotrope-like composition, e.g., by decantation. Depending upon the composition of the dihaloethane component of the azeotrope, the dihaloethane can be recovered as a useful product or employed as a precursor of another fluorocarbon.
REFERENCES:
patent: 715612 (1965-08-01), None
Englin et al Soviet Inventions Illustrated, 163599, Feb. 1965.
Beug-Deeb Maria U. D.
Mahler Barry Asher
Miller Ralph Newton
E. I. Du Pont de Nemours and Company
Shipley James E.
Siegel Alan
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