Organic compounds -- part of the class 532-570 series – Organic compounds – Halogen containing
Reexamination Certificate
2003-02-06
2004-03-16
Richter, Johann (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Halogen containing
C570S169000
Reexamination Certificate
active
06706935
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the preparation of halogen substituted hydrocarbons and more particularly to the use of equilibrium reactions for preparing halogen substituted hydrocarbons containing fluorine.
BACKGROUND OF THE INVENTION
There has been considerable recent interest in halogen substituted ethanes containing fluorine and hydrogen. Many of these materials can be used not only as blowing agents and refrigerants, but also as starting materials for preparing other useful compounds.
U.S. Pat. No. 4,766,260 discloses an improved gas-phase process for the manufacture of 1,1,1-trifluorodichloroethane (i.e., HCFC-123) and 1,1,1,2-tetrafluorochloroethane (i.e., HCFC-124) by contacting a suitable tetrahaloethylene with hydrogen fluoride in the presence of a selected metal on a high fluorine content alumina support, the reaction being conducted under controlled conditions whereby the production of pentafluoroethane (i.e., HFC-125) is minimized. U.S. Pat. No. 4,766,260 discloses that intermediates formed during the course of the invention, such as CHF
2
CClF
2
, CHClFCClF
2
, CHCl
2
CClF
2
, CClF═CCl
2
and CHCl
2
CCl
2
F can be recycled to the reactor for the production of additional 1,1,1-trifluorodichloroethane and 1,1,1,2-tetrafluorochloroethane; and that 1,1,1-trifluorodichloroethane can be recycled to the reactor for the production of additional 1,1,1,2-tetrafluorochloroethane when this is desired. It is often desirable to avoid the use and production of unsaturated materials, and there is thus a need for additional techniques which selectively yield saturated halogen substituted hydrocarbons containing fluorine and hydrogen such as HCFC-123, HCFC-124 and HFC-125.
Chromium-containing catalysts have been used in conjunction with disproportionations and other reactions involving halogen-substituted ethanes. For example, U.S. Pat. No. 4,145,368 discloses a process for manufacturing 1,1,1-trifluoro-2,2-dichloroethane by reaction of 1,1,1-trifluoro-2,2,2-trichloroethane with 1,1,1-trifluoro-2-chloroethane over a solid catalyst such as Cr
2
O
3
. The use of catalysts containing chromium in a valence state of three to six and either oxide alone or oxide and fluoride is disclosed. U.S. Pat. No. 3,787,331 discloses use of a chromium-containing catalyst in disproportionating and isomerizing CF
2
Cl—CFCl
2
; and U.S. Pat. No. 3,651,156 exemplifies the disproportionation reaction of C
2
F
3
Cl
3
passed over a catalyst obtained by fluorination of chromium hydroxide.
U.S. Pat. No. 4,605,798 discloses a process for the preparation of trichlorotrifluoroethanes, dichlorotetrafluoroethanes, and monochloropentafluoroethane utilizing three reactors, one of which is used for a fluorination-dismutation reaction. The catalysts used in these reactors comprise supported or non-supported oxides or halides of chromium among others.
SUMMARY OF THE INVENTION
We have found that catalysts selected from the group of catalysts consisting of catalysts containing chromium in a valence state of three to six as an oxide, a halide, or as halided oxide and supported catalysts containing at least one metal selected from cobalt, copper, iron, manganese, nickel and zinc are effective in equilibrating CF
3
CFHCl with its disproportionation products CF
3
CHCl
2
and CF
3
CF
2
H; and that the equilibration constant for the disproportionation varies with temperature over the range of 50° C. to 500° C., with the formation of CF
3
CFHCl becoming more favored as the temperature increases.
The present invention involves at least partial equilibration of the halohydrocarbon CF
3
CFHCl (HCFC-124) with halohydrocarbons CF
3
CHCl
2
(HCFC-123) and CF
3
CF
2
H (HFC-125) using a vapor phase reaction. In this equilibration the halogens on the carbon containing the hydrogen exchange. All the compounds involved in the interconversion contain exactly two carbons and one hydrogen.
A method is provided in accordance with this invention for increasing in a composition the mole fraction of a selected compound of the formula CF
3
CHF
x
Cl
2−x
where x is an integer from 0 to 2 relative to the total mole fraction of the other two compounds having said formula which comprises the steps of: (a) providing a gaseous composition comprising at least one compound of said formula provided that (i) if the selected compound is either CF
3
CHCl
2
or CF
3
CHF
2
, said gaseous composition comprises CF
3
CHFCl and the mole fraction of the selected compound relative to the other two compounds in said gaseous composition is less than its equilibrium amount at 50° C., and (ii) if the selected compound is CF
3
CHFCl, said gaseous composition comprises CF
3
CHCl
2
and CF
3
CHF
2
and the mole fraction of the selected compound relative to the other two compounds in said gaseous composition is less than its equilibrium amount at 500° C.; (b) contacting said gaseous composition with a catalyst selected from the group of catalysts consisting of catalysts comprising chromium as an oxide, as a halide or as a halided oxide, in a valence state of three to six, and supported catalysts containing at least one metal selected from cobalt, copper, iron, manganese, nickel and zinc, for a time sufficient to provide substantial interconversion among the three compounds having said formula; and (c) providing during said catalyst contact a temperature within the range of about 50° C. to 500° C. at which the mole fraction of the selected compound relative to the other two compounds increases.
The method, preferably supplemented by the steps of separating at least a portion of the selected compound from the interconverted composition of step (c); and contacting at least a portion of the compounds remaining after said separation with a catalyst selected from said group of catalysts at a temperature within the range of about 50° C. to 500° C. and for a time sufficient to produce an additional quantity of said selected compound by providing substantial interconversion; can be advantageously included in a process for preparing halogen substituted ethanes to increase the yield of the selected compound relative to the total yield of the other two compounds having the above-referenced formula.
DETAILS OF THE INVENTION
The invention deals with processes employing the interconversion of CF
3
CFHCl (HCFC-124) with CF
3
CHCl
2
(HCFC-123) and CF
3
CF
2
H(HFC-125) using selected catalysts. The preferred catalysts of this invention comprise chromium in a valence state of three to six as an oxide (e.g., Cr
2
O
3
), as a halide (e.g., CrX
3
where each X is selected from chlorine and fluorine) or as a halided oxide (e.g., Cr
2
O
3
treated with CCl
3
F or CCl
4
). The chromium catalysts of this invention can be supported or unsupported. Other catalysts which may be used for the interconversion of this invention include supported catalysts containing at least one metal selected from cobalt, copper, iron, manganese, nickel and zinc.
A method is provided in accordance with this invention for increasing in a composition the mole fraction of a selected compound of the formula CF
3
CHF
x
Cl
2−x
where x is an integer from 0 to 2 relative to the total mole fraction of the other two compounds having said formula comprising the steps of: (a) providing a gaseous composition comprising at least one compound of said formula provided that (i) if the selected compound is either CF
3
CHCl
2
or CF
3
CHF
2
, said gaseous composition comprises CF
3
CHFCl and the mole fraction of the selected compound relative to the other two compounds in said gaseous composition is less than its equilibrium amount at 50° C., and (ii) if the selected compound is CF
3
CHFCl, said gaseous composition comprises both CF
3
CHCl
2
and CF
3
CHF
2
and the mole fraction of the selected compound relative to the other two compounds in said gaseous composition is less than its equilibrium amount at 500° C.; (b) contacting said gaseous composition, with a catalyst selected from the group of catalysts consisting of catalysts comprising chromium as an oxide, as a halide or as a halided oxide, in
Manzer Leo Ernest
Weigert Frank Julian
E. I. du Pont de Nemours and Company
Price Elvis O.
Richter Johann
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