Organic compounds -- part of the class 532-570 series – Organic compounds – Halogen containing
Reexamination Certificate
1997-04-24
2002-08-20
Siegel, Alan (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Halogen containing
C570S165000, C570S166000, C570S167000, C570S168000
Reexamination Certificate
active
06437201
ABSTRACT:
This invention relates to a process for the production of hydrofluoroalkanes, particularly 1,1,1,2-tetrafluoroethane and pentafluoroethane.
Several processes have been proposed for the production of 1,1,1,2-tetrafluoroethane, otherwise known as HFC 134a, and pentafluoroethane, otherwise known as HFC 125 which are employed as or as components of replacements for chiorofluorocarbons in the many applications in which chlorofluorocarbons are employed. Amongst such processes is the fluorination of the corresponding chlorine-containing starting material by reacting the starting material with hydrogen fluoride in the liquid or the vapour phase, usually in the presence of a fluorination catalyst.
Thus it has been proposed in United Kingdom Patent Specification No. 1,589,924 to produce HFC 134a by the vapour phase fluorination of 1,1,1-trifluoro-2-chloroethane (HCFC 133a) which is itself obtainable by the fluorination of trichioroethylene as described in United Kingdom Patent Specification No. 1,307,224.
The formation of HFC 134a as a minor product of the fluorination or trichloroethylene is described in United Kingdom Patent Specification No 819,849, the major reaction product being HCFC 133a.
More recently, processes for the production of HFC 134a from trichloroethylene based on a combination of the reaction of trichloroethylene with hydrogen fluoride to produce HCFC 133a and the reaction of HCFC 133a with hydrogen fluoride to produce HFC 134a have been proposed.
In WO 90/08755, the contents of which are incorporated herein by reference, there is described the conversion of trichloroethylene to HFC 134a wherein the two reactions steps are carried out in a single reaction zone with recycle of part of the product stream containing HCFC 133a.
In EP 0 449 614, the contents of which are also incorporated herein by reference, there is described a process for the manufacture of HFC 134a which comprises the steps of:
(A) contacting a mixture of trichloroethylene and hydrogen fluoride with a fluorination catalyst under superatmospheric pressure at a temperature in the range from about 200° C. to about 400° C. in a first reaction zone to form a product containing 1,1,1-trifluoro-2-chloroethane and hydrogen chloride together with unreacted starting materials,
(B) passing product of step A together with hydrogen fluoride to a second reaction zone containing a fluorination catalyst at a temperature in the range from about 280° C. to about 450° C. but higher than the temperature in step A to form a product containing 1,1,1-trifluoro-2-chloroethane, 1,1,1,2-tetrafluoroethane and hydrogen chloride,
(C) treating product of step B to separate 1,1,1,2-tetrafluoroethane and hydrogen chloride from 1,1,1-trifluoro-2-chloroethane and unreacted hydrogen fluoride, and
(D) feeding 1,1,1-trifluoro-2-chloroethane obtained from step C together with trichloroethylene and hydrogen fluoride to said first reaction zone (step A).
In EP 0 449 617, the contents of which are also incorporated herein by reference, there is described a process for the production of BFC 134a which comprises the steps of:
(A) contacting a mixture of 1,1,1-trifluoro-2-chloroethane and hydrogen fluoride with a fluorination catalyst at a temperature in the range from about 280° C. to about 450° C. in a first reaction zone to form a product containing 1,1,1,2-tetrafluoroethane and hydrogen chloride together with unreacted starting materials,
(B) passing product of step A together with trichloroethylene to a second reaction zone containing a fluorination catalyst at a temperature in the range from about 200° C. to about 400° C. but lower than the temperature in step A to form a product containing 1,1,1-trifluoro-2-chloroethane, 1,1,1,2-tetrafluoroethane, hydrogen chloride and unreacted trichloroethylene and hydrogen fluoride,
(C) treating product of step B to separate 1,1,1,2-tetrafluoroethane and hydrogen chloride from 1,1,1-trifluoro-2-chloroethane, unreacted trichioroethylene and hydrogen fluoride, and
(D) feeding 1,1,1-trifluoro-2-chloroethane obtained from step C together with hydrogen fluoride to said first reaction zone (step A).
However, a problem which is encountered with processes for the production of 1,1,1,2-tetrafluoroethane based on the hydrofluorination of 1-chloro-2,2,2-trifluoroethane and/or trichioroethylene, is that the conversion of 1-chloro-2,2,2-trifluoroethane to 1,1,1,2-tetrafluoroethane is equilibrium limited, there being a maximum conversion of 1-chloro-2,2,2-trifluoroethane to 1,1,1,2-tetrafluoroethane of only about 20% under typical operating conditions.
It has also been proposed to produce pentafluoroethane (HFC 125) by the catalysed fluorination with hydrogen fluoride of chlorotetrafluoroethane (HCFC 124) and/or dichlorotrifluoroethane (HCFC 123) which are themselves obtainable by the fluorination of perchioroethylene with hydrogen fluoride.
The present invention resides in a process for the production of hydrofluoroalkanes, particularly 1,1,1,2-tetrafluoroethane and pentafluoroethane from hitherto unused starting materials, which process in the case of production of 1,1,1,2-tetrafluoroethane is not subject to the aforementioned equilibrium limitation problem.
According to the present invention there is provided a process for the production of a hydrofluoroalkane which comprises contacting a hydrochlorofluoroethane having the formula CClXYCFHZ or a(hydro)chlorofluoroethene having the formula CClA═CFZ in which X and Y are each independently chlorine or fluorine, Z is chlorine or hydrogen and A is chlorine or fluorine provided that where each of X and Y is fluorine then Z is hydrogen in the vapour phase with hydrogen fluoride and a fluorination catalyst and recovering a hydrofluoroalkane from the resulting products.
In a particular embodiment of the process for producing 1,1,1,2-tetrafluoroethane, the hydrochlorofluoroethane has the formula CClXYCFH
2
and the (hydro)chlorofluoroethene has the formula CClA═CFH.
We have found that the product gases from the process for producing 1,1,1,2-tetrafluoroethane comprise a greater molar proportion of 1,1,1,2-tetrafluoroethane than is obtained when 1-chloro-2,2,2-trifluoroethane is used as the starting material.
The starting materials for the process are CCl
3
CFH
2
, CCl
2
FCFH
2
, CClF
2
CFH
2
, CCl
2
FCClFH, CCl
3
CHFCl, CCl
2
═CFH, CClF═CFH, CCl
2
═CFCl and CClF═CFCl. We prefer to employ CCl
2
═CFH or CCl
2
FCFH
2
, especially CCl
2
═CFH for the production of 1,1,1,2-tetrafluoroethane and CCl
2
FCClFH or CClF═CFCl for the production of pentafluoroethane since these materials are more readily available.
Processes for the production of the starting materials of the present invention are known. Thus for example CCl
2
═CFH may be produced from trichloroethylene, as described in the Journal of Organic Chemistry 28, 112 (1963), or from tetrachloroethane as described in EP 537560.
Suitable fluorination catalysts are those which yield the desired hydrofluoroalkane as a product of the reaction with a yield of greater than 20%, preferably greater than 25%, based on the starting material processed and include catalysts based on chromia or chromium oxyfluoride, and the fluorides or oxyfluorides of other metals, for example magnesium and aluminium. Activity promoting amounts of other metals, for example zinc and nickel may also be present; we particularly prefer to employ a catalyst comprising zinc on chromia as described fully in published European Patent Application No. 502605, the contents of which are incorporated herein by reference.
The relative proportion of hydrogen fluoride to starting material which is employed may vary within wide limits although it is generally preferred to employ a stoichiometric excess of hydrogen fluoride. The stoichiometrically required molar ratio depends upon the particular starting material. Where the starting material is the preferred 1,1-dichloro-2-fluoroethene, the stoichiometrically required molar ratio of hydrogen fluoride to 1,1-dichloro-2-fluoroethene is 3:1. The molar ratio of hydrogen fluorid
Davies Michael Anthony
Ewing Paul Nicholas
Powell Richard Llewellyn
Skinner Christopher John
Cook Alex McFarron Manzo Cummings & Mehler, Ltd.
Ineos Fluor Holdings Limited
Siegel Alan
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