U.S. patent application number 08/817735 was filed with the patent office on 2002-04-04 for production of hydrofluoroalkanes.
Invention is credited to DAVIES, MICHAEL ANTHONY, EWING, PAUL NICHOLAS, POWELL, RICHARD LLEWELLYN, SKINNER, CHRISTOPHER JOHN.
Application Number | 20020040171 08/817735 |
Document ID | / |
Family ID | 26305874 |
Filed Date | 2002-04-04 |
United States Patent
Application |
20020040171 |
Kind Code |
A1 |
EWING, PAUL NICHOLAS ; et
al. |
April 4, 2002 |
PRODUCTION OF HYDROFLUOROALKANES
Abstract
A process for the production of a hydrofluoroalkane,
particularly 1,1,1,2-tetrafluoroethane or pentafluoroethane, which
comprises contacting a hydrochlorofluoroethane or a
hydrochlorofluoroethene with hydrogen fluoride and a fluorination
catalyst and recovering a hydrofluoroalkane from the resulting
products, the hydrochlorofluoroethane having the formula CClXYCFHZ
and the hydrochlorofluoroethene having the formula CClA-CFZ wherein
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. A preferred embodiment
of the process is the production of 1,1,1,2-tetrafluoroethane from
the hydrochlorofluoroethene CCl.sub.2.dbd.CFH.
Inventors: |
EWING, PAUL NICHOLAS;
(CHESHIRE, GB) ; POWELL, RICHARD LLEWELLYN;
(CHESHIRE, GB) ; DAVIES, MICHAEL ANTHONY;
(CHESIRE, GB) ; SKINNER, CHRISTOPHER JOHN;
(DURHAM, GB) |
Correspondence
Address: |
ANDREW G. KOLOMAYETS
COOK ALEX MCFARRON MANZO CUMMINGS & MEHLER, LTD.
200 WEST ADAMS STREET.
SUITE 2850
CHICAGO
IL
60606
US
|
Family ID: |
26305874 |
Appl. No.: |
08/817735 |
Filed: |
April 24, 1997 |
PCT Filed: |
October 23, 1995 |
PCT NO: |
PCT/GB95/02491 |
Current U.S.
Class: |
570/169 |
Current CPC
Class: |
C07C 17/206 20130101;
C07C 17/21 20130101; C07C 19/08 20130101; C07C 17/206 20130101 |
Class at
Publication: |
570/169 |
International
Class: |
C07C 017/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 27, 1994 |
GB |
9421619.9 |
Dec 22, 1994 |
GB |
9425929.8 |
Claims
1. A process for the production of a hydrofluoroalkane which
comprises contacting a hydrochlorofluoroethane having the formula
CClXYCFHZ or a hydrochlorofluoroethene having the formula
CClA.dbd.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.
2 A process as claimed in claim 1 for the production of
1,1,1,2-tetrafluoroethane wherein the hydrochlorofluoroethane has
the formula CClXYCFH.sub.2 and the hydrochlorofluoroethene has the
formula CClZ.dbd.CFH.
3. A process as claimed in claim 1 or claim 2 wherein the hydrogen
fluoride is present in stoichiometric excess relative to the
hydrochlorofluoroethane or hydrochlorofluoroethene.
4 A process as claimed in claim 3 wherein the molar ratio of
hydrogen fluoride to the hydrochlorofluoroethane
hydrochlorofluoroethene is at least 4:1.
5. A process as claimed in claim 2 wherein the molar ratio of
hydrogen fluoride to the hydrochlorofluoroethane
hydrochlorofluoroethene is at least 4:1.
6. A process as claimed in any one of the preceding claims wherein
the temperature is from 180.degree. C. to 350.degree. C.
7. A process as claimed in any one of the preceding claims which is
carried our under superatmospheric pressure.
8. A process as claimed in any one of the preceding claims wherein
the fluorination catalyst is based on chromia or chromium
oxyfluoride or the fluorides and oxyfluorides of other metals.
9. A process as claimed in any one of the preceding claims for the
production of 1,1,1,2-tetrafluoroethane wherein the
hydrochlorofluoroethene is CCl.sub.2.dbd.CFH.
10. A process as claimed in any one of the preceding claims wherein
the hydrochlorofluoroethane or hydrochlorofluoroethene is fed as a
second starting material together with trichloroethylene in a
process for the production of 1,1,1,2-tetrafluoroethane by the
fluorination of trichloroethylene.
Description
[0001] This invention relates to a process for the production of
hydrofluoroalkanes, particularly 1,1,1,2-tetrafluoroethane and
pentafluoroethane.
[0002] 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 chlorofluorocarbons 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.
[0003] 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 trichloroethylene as
described in United Kingdom Patent Specification No. 1,307,224.
[0004] 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.
[0005] 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.
[0006] 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.
[0007] In EP 0 449 614, the contents of which are also incorporated
herein by reference, there is described a process for the
manufacture of HPA 134a which comprises the steps of:
[0008] (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.degree. C. to
about 400.degree. 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,
[0009] (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.degree. C. to
about 450.degree. 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,
[0010] (C) treating product of step B to separate
1,1,1,2-tetrafluoroethan- e and hydrogen chloride from
1,1,1-trifluoro-2-chloroethane and unreacted hydrogen fluoride,
and
[0011] (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).
[0012] In EP 0 449 617, the contents of which are also incorporated
herein by reference, there is described a process for the
production of HFC 134a which comprises the steps of:
[0013] (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.degree. C. to about 450.degree. C. in a
first reaction zone to form a product containing
1,1,1,2-tetrafluoroethane and hydrogen chloride together with
unreacted starting materials,
[0014] (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.degree. C. to about 400.degree. 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,
[0015] (C) treating product of step B to separate
1,1,1,2-tetrafluoroethan- e and hydrogen chloride from
1,1,1-trifluoro-2-chloroethane, unreacted trichloroethylene and
hydrogen fluoride, and
[0016] (D) feeding 1,1,1-trifluoro-2-chloroethane obtained from
step C together with hydrogen fluoride to said first reaction zone
(step A).
[0017] 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
trichloroethylene, 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.
[0018] 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
perchloroethylene with hydrogen fluoride.
[0019] 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.
[0020] 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 hydrochlorofluoroethene 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.
[0021] In a particular embodiment of the process for producing
1,1,1,2-tetrafluoroethane, the hydrochlorofluoroethane has the
formula CClXYCFK and the A hydrochlorofluoroethene has the formula
CClZ=CFH.
[0022] 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-trifluoroe- thane is used as the starting
material.
[0023] he starting materials for the process are
CCl.sub.3CFH.sub.2, CCl.sub.2FCFH.sub.2, CClF.sub.2CFH.sub.2,
CCl.sub.2FCClFH, CCl.sub.3CHFCl, CCl.sub.2.dbd.CFH, CClF.dbd.CFH,
CCl2.dbd.CFCl and CClF.dbd.CFCl. We prefer to employ
CCl.sub.2.dbd.CFH or CCl.sub.2FCFH.sub.2, especially
CCl.sub.2.dbd.CFH for the production of 1,1,1,2-tetrafluoroethane
and CCl.sub.2FCClFH or CClF.dbd.CFCl for the production of
pentafluoroethane since these materials are more readily
available.
[0024] Processes for the production of the starting materials of
the present invention are known. Thus for example CCl.sub.2.dbd.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.
[0025] 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.
[0026] 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
fluoride to the starting material, for example
1,1-dichloro-2-fluoroethene, will usually be at least 2:1, and
preferably is at least 4:1 and especially at least 6:1 and
substantially greater excesses of hydrogen fluoride, for example up
to 50:1, may be employed if desired.
[0027] The temperature at which the process is carried out is
preferably at least 180.degree. C. and more preferably at least
200.degree. C. or 220.degree. C. but may be significantly lower
than the temperatures typically employed for the conversion of
1-chloro-2,2,2-trifluoroethane to 1,1,1,2-tetrafluoroethane.
Preferably the temperature is not greater than 350.degree. C.,
especially not greater than 330.degree. C.
[0028] The process may be carried out at atmospheric pressure
although superatmospheric pressure,-say up to about 30 bar is
preferred.
[0029] The contact time is preferably in the range from about 0.1
seconds to about 10 seconds, preferably in the range from about 0.5
seconds to about 5 seconds at atmospheric pressure.
[0030] As described previously, hydrofluorination of
trichloroethylene via the intermediate
1-chloro-2,2,2-trifluoroethane is used for the production of
1,1,1,2-tetrafluoroethane. If desired the process of the present
invention may be combined with processes for the production of
1,1,1,2-tetrafluoroethane based on
trichloroethylene/1-chloro-2,2,2-trifl- uoroethane.
[0031] Thus and according to a preferred embodiment of the
invention, a hydrochlorofluoroalkane and/or a
hydrochlorofluoroalkene as hereinbefore defined, for example
1,1-dichloro-2-fluoroethene is fed as a second starting material to
processes for the production of 1,1,1,2-tetrafluoroethane employing
trichloroethylene as the starting material.
[0032] The co-feeding of trichloroethylene and the second starting
material such as 1,1-dichloro-2-fluoroethene may be effected in the
processes described in our published European Patent Applications
Nos 0 449 617, and 0 449 614, the contents of which are
incorporated herein by reference.
[0033] The invention is illustrated but not limited by the
following Examples.
[0034] The 1,1-dichloro-2-fluoroethene (HCFC 1121 a) used in the
Examples was synthesised via the ethanolic potassium hydroxide
dehydrochlorination of trichlorofluoroethane (HCFC 131) as
described in J. Am. Chem. Soc., 1936, 58, 402. The resulting crude
product was washed with water, dried with magnesium sulphate and
then fractionally distilled with the fraction boiling between
32.degree. C. and 34.degree. C. being collected; this fraction was
analysed and found to be pure HCFC 1121 a.
[0035] The 1,1-dichloro-1,2-difluoroethane (HCFC 132c) used in the
Examples was synthesised by oxyfluorination of 1,1-dichloroethane
(vinylidene chloride) using lead (IV) oxide in anhydrous hydrogen
fluoride as described in J. Am. Chem. Soc., 1945, 67, 1639. The
reaction was carried out in a Hastalloy C autoclave and yielded a
considerable amount of the co-product 1,1-dichloro-1-fluoroethane
(HCFC 14 1b). The resulting reaction mixture was fractionally
distilled and a fraction comprising 60% HCFC 141b and 40% HCFC 132c
by weight was collected; it was not feasible to separate the HCFC
132c from the HCFC 141 b by distillation.
[0036] The 1,1,2-trichloro-1,2-difluoroethane (HCFC 122a) used in
the Examples was synthesised by oxyfluorination of
trichloroethylene using lead (IV) oxide in anhydrous hydrogen
fluoride as described in J. Am. Chem. Soc., 1945, 67, 1639 in a
Hastalloy C autoclave. The reaction mixture contained unreacted
trichloroethylene which was removed by treatment with bromine to
form 1,2-dibromo-1,1,2-trichloroethane followed by fractional
distillation. A fraction comprising HCFC 122a was collected and
analysis showed it to be pure HCFC 122a.
EXAMPLE 1.
[0037] 2 ml of a catalyst comprising 8% by weight of zinc on
chromia was charged to a 1/4" I.D. Inconel reactor tube and the
catalyst was pre-fluorinated by passing hydrogen fluoride over the
catalyst at 300.degree. C. for 24 hours. After this time, hydrogen
fluoride and 1,1-dichloro-2-fluoroethene (in ethanol) were passed
over the catalyst at 275.degree. C. and at flow rates of 25
ml/minute and 6 ml/minute respectively giving a contact time with
the catalyst of 1.4 seconds.
[0038] The reactor off-gases were sampled and the samples analysed
by Gas Chromatography. The conversion of
1,1-dichloro-2-fluoroethene was 55.8% and selectivity to
1,1,1,2-tetrafluoroethane was 67.6% respectively.
EXAMPLE 2
[0039] 2.5 gm of a catalyst comprising 8% by weight of zinc on
chromia was charged to a 1/4" I.D. Inconel reactor tube and the
catalyst was dried at 300.degree. C. for 1 hour in a stream of 10
ml/minute of nitrogen gas. The dried catalyst was then fluorinated
by heating at 300.degree. C. for 2 hours in a stream of 10
ml/minute of hydrogen fluoride and nitrogen delivering
approximately 41 m mole of hydrogen fluoride per hour.
[0040] A sample of 1,1-dichloro-2-fluoroethene (0.64 gm) in
hydrogen fluoride previously prepared by introducing the
1,1-dichloro-2-fluoroethe- ne into a hydrogen fluoride purged
Whitey bomb and comprising a mole ratio of hydrogen fluoride:
sample of 8:1 was fed over the catalyst by diverting the hydrogen
fluoride/nitrogen flow, the catalyst temperature being maintained
throughout at 300.degree. C. The mole ratio of hydrogen fluoride:
1,1-dichloro-2-fluoroethene in the flow was approximately 4:1.
[0041] After a period of 5 minutes from diversion of the hydrogen
fluoride/nitrigen flow to entrain the sample of
1,1-dichloro-2-fluoroethe- ne, samples of the products stream,
after scrubbing with sodium carbonate solution, were analysed by
Gas Chromatography analysis and IR spectroscopy analysis.
[0042] Analysis determined that the major products were
1,1,1,2-tetrafluoroethane [HFC 134a], chloro-2,2,2-trifluoroethane
[HFC 133a] and chlorotetrafluoroethane [HCFC 124].
[0043] The results are shown in Table 1 and show that feeding
1,1-dichloro-2-fluoroethene instead of trichloroethylene produces a
higher yield of 1,1,1,2-tetrafluoroethane (HFC 134a) and is not
subject to the equilibrium restriction which is encountered using
trichloroethylene as the feed.
EXAMPLE 3
[0044] The procedure described in Example 2 was repeated except
that the flow of hydrogen fluoride/nitrogen was reduced to 2
ml/minute instead of 10 ml/minute so that the mole ratio of
hydrogen fluoride: 1,1-dichloro-2-fluoroethene in the feed to the
catalyst was halved to approximately 2:1.
[0045] Analysis showed that the major products were
1,1,1,2-tetrafluoroethane (HFC 134a) and
chloro-2,2,2-trifluoroethane (HFC 133a) in approximately equal
amounts. The results are shown in Table 1.
EXAMPLE 4
[0046] The procedure described in Example 2 was repeated to react
1,1-dichloro-2-fluoroethene (0.32 g) with hydrogen fluoride at
different catalyst temperatures. The initial mole ratio of hydrogen
fluoride: 1,1,-dichloro-2-fluoroethene fed to the catalyst was
approximately 8:1
[0047] Three runs were carried out at catalyst temperatures of
250.degree. C., 300.degree. C. and 350.degree. C. during the sample
feed. Samples of the product streams for analysis were taken after
4 minutes from diversion of the hydrogen fluoride/nitrogen flow to
entrain the sample. The results of analysis are shown in Table
1.
[0048] At 250.degree. C., the conversion of
1,1-dichloro-2-fluoroethene was 42.9% and 1,1,1,2-tetrafluoroethane
was the only major product.
[0049] At 300.degree. C., the conversion of
1,1-dichloro-2-fluoroethene was 81.6% and the major product was
again 1,1,1,2-tetrafluoroethane although a significant amount of
chloro-2,2,2-trifluoroethane [HCFC 133a] was also obtained.
[0050] At 350.degree. C., the conversion of
1,1,-dichloro-2-fluoroethene was 98.5% and the major products were
1,1,1,2-tetrafluoroethane and chloro-2,2,2-trifluoroethane in a
ratio of approximately 1:2.
1TABLE 1 Selectivity (%) Example No. Temp. (.degree. C.) Conversion
(%) 134a 133a 2 300 93.7 54.8 37.2 3 300 86.6 48.2 46.0 4 250 42.9
76.5 5.3 300 81.6 69.3 25.3 350 98.5 32.8 65.5
EXAMPLE 5
[0051] This example describes the conversion of
1,1-dichloro-1,2-difluoroe- thane (HCFC 132c) to
1,1,1,2-tetrafluoroethane.
[0052] The procedure described in Example 2 was used to react
1,1-dichloro-1,2-difluoroethane (0.3 g) with hydrogen fluoride at a
range of catalyst temperatures from 200.degree. C. to 333.degree.
C. Samples for analysis were taken after 4 minutes. Runs were
carried out at catalyst temperatures of 200.degree. C., 250.degree.
C., 290.degree. C. and 330.degree. C. The sample of
1,1-dichloro-1,2-difluoroethane was prepared as described
hereinbefore and contained 60% by weight of
1,1-dichloro-1-fluoroethane (HCFC 14 lb) and 40% by weight of HCFC
132c.
[0053] The major product observed in each run was
1,1,1-trifluoroethane (HFC 143a). It is assumed in interpreting the
results that (a) this major product is derived exclusively from the
1,1-dichloro-1-fluoroethane in the starting material and (b) the
1,1-dichloro-1-fluoroethane plays no other part in the process so
that all products other than 1,1,1-trifluoroethane are derived from
the 1,1-dichloro-1,2-difluoroethan- e.
[0054] The analysis results are shown in Table 2.
[0055] At 330.degree. C., the conversion of
1,1-dichloro-1,2-difluoroethan- e was 100% and the major products
were 1,1,1,2-tetrafluoroethane and
chloro-2,2,2-trifluoroethane.
[0056] At 290.degree. C., the conversion was 100% with
1,1,1,2-tetrafluoroethane and chloro-2,2,2-trifluoroethane being
the major products.
[0057] At 250.degree. C., the conversion was 100% with
1,1,1,2-tetrafluoroethane and chloro-2,2,2-trifluoroethane being
the major products.
[0058] At 200.degree. C., the conversion was 100% with
1,1,1,2-tetrafluoroethane being the major product.
[0059] It was observed in these runs that
1,1-dichloro-2-fluoroethene (HCFC 1121 a) was obtained as a by
product with % selectivities of 16.2% (at 330.degree. C.), 2.9% (at
290.degree. C.), 31.7% (at 250.degree. C.) and 55.6% (at
200.degree. C.). It was also observed that
1-chloro-2,2,2-trifluoroethane (HCFC 133b) was obtained at
250.degree. C. (5.1%) and at 200.degree. C. (23.6%).
2TABLE 2 Selectivity (%) Example No Temp. (.degree. C.) Conversion
(%) 134a 133a 5 200 100 17.2 1.3 250 100 54.8 6.2 290 100 26.9 65.0
330 100 22.5 52.6
Comparative Example
[0060] For purposes of comparison, the procedure described in
Example 2 was used to react chloro-2,2,2-trifluoroethane (HCFC
133a) (0.3 gm) with hydrogen fluoride at catalyst temperatures of
290.degree. C. (Run 1) and 330.degree. C. (Run 2).
[0061] In Run 1, at 290.degree. C., the conversion of HCFC 133a was
only about 7% and the yield of 1,1,1,2-tetrafluoroethane was
6.5%.
[0062] In Run 2, at 330.degree. C., the conversion of HCFC was
about 20% and the yield of 1,1,1,2-tetrafluoroethane was 18.7%.
[0063] The results are shown in Table 3.
3TABLE 3 Conversion (%) Selectivity (%) Example No. Temp. (.degree.
C.) [of 133a] [of 134a] Comparative Example 290 7.2 90.3 330 19.8
94.4
EXAMPLE 6
[0064] This example illustrates the conversion of
1,1,2-trichloro-1,2-difl- uoroethane (HCFC 122a) to
pentafluoroethane (HFC 125).
[0065] The procedure described in Example 2 was used to react
1,1,2-trichloro-1,2-difluoroethane (0.47 gm) with hydrogen fluoride
at a catalyst temperature of 340.degree. C. except that the
catalyst was fluorinated overnight instead of for 2 hours. The
results are shown in Table 4.
4TABLE 4 Selectivity (%) Example No. Temp. (.degree. C.) Conversion
(%) 125 123/a 124/a 1111 6 340 100 33.2 2.1 29.6 7.4
* * * * *