Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
MD 29573
This invention relates to a process for the manufacture
of tetrafluoroethane.
According to the present invention we provide a process
for the manufacture of tetrafluoroethane having the formula
:: 5 CHF2CHF2 or CF3CH2F characterised in that a
~ haloethane having four or five fluorine atoms of
: formula CF2 X CFYZ where X is fluorine or chlorine and
when X is fluorlne, Y is chlorine or fluorine and when Y
is chlorine Z is chlorine, fluorine or hydrogen and
~: 10 when Y is fluorine Z is hydrogen and when X is chlorine
Y is fluorine and Z is either chlorine or hydrogen is
: reacted with hydrogen at elevated temperature in the
presence of a hydrogenation catalyst.
3~:
The or~anic starting materials of the present
invention consist of :-
1,2-dichloro-1,1,2,2-tetrafluoroethane (CClF2 CClF2)
l,l-dichloro 1,2,2,2-tetrafluoroethane (CC12F CF3)
1-chloro-1,1,2,2,2-pentafluoroethane (CClF2 CF3)
l-chloro-1,2,2,2-tetrafluoroethane (CHClFCF3)
2-chloro-1,1,2,2-tetrafluoroethane (CHF2 CClF2)
1,1,2,2,2-pentafluoroethane (CHF2 CF3)
Mixtures of said organic starting materials may
be employed. Two very suitable starting materials are
1,2-dichloro-1,1,2,2-tetrafluoroethane (the sym isomer
of dichloro-tetrafluoroethane, CClF2CClF2) and 1,1-
dichloro-1,2,2,2-tetrafluoroethane (the asym isomer of
dichloro-tetrafluoroethane, CC12FCF3). 1,2-dichloro-
1,1,2,2-tetrafluoroethane containing a small proportion
(e.g. up to 10% by wt) of 1,1-dichloro-1,2,2,2-tetrafluoro-
ethane) as produced commercially may be used as organic
starting materials. Alternatively mixtures of said dichloro-
tetrafluoroethanes in any proportions may be employed.
3~
Hydro~enation catalysts are in themselves known.
In the present process there is removal of two chlorine
atoms or a chlorine and/or a fluorine atom feom the
haloethane starting material and substitution oE hydrogen
therefor. Examples of hydrogenation catalysts include nickel
or metals of Group VIIIa of the Periodic Table or oxides or
salts thereof.
In use a compound of such a metal is reduced at
least in part to the metal. One very useful metal
which can be employed in the process of the present
invention is palladium. The metal may be carried on
a suitable support, for example, alumina or activated
carbon.
The proportion of hydrogen to organic feed is
capable of considerable variation. Usually at least
the stoichiometric amount of hydrogen is employed to
remove the halogen atom or atoms. Considerably
greater than said stoichiometric amounts for example
4 or more moles of hydrogen may be employed per total
mole of starting material. When the organic
starting materials consists of essentially pure 1,2-
dichloro-1,1,2,2-tetrafluoroethane (CClF2CClF2) or l,l-
dichloro-1,2,2,2-tetrafluoroethane (CCl2FCF3~ it is
preferred to employ at least two moles of hydrogen
(the stoichiometric amount) per mole of organic
starting material. When a mixture of CClF2CClF2
and CC12FCF3 is employed as organic feed there
may be employed at least the stoichiometric amount of
hydrogen per mole of CC12FCF3. This can mean that
there is sometimes less tha:n the stoichiometric
amount of hydrogen with respect. to total mole
fluorochloroethane feed. Thus with a mixture containing
3 moles CClF2CClF2 and 1 mole CC12FCF3 there
may be employed 2 to 3 moles of hydrogen per mole
CClF2CF3 and this corresponds to a molar ratio of
hydrogen to total mole fluorochloroethane feed of
0.5:1 to 0.75:1 respectively. Similarly when there
is employed an equimolar mixture of CClF2CClF2 and
CC12FCF3 there may be employed 2 to 3 moles of
hydrogen per mole CC12FCF3 and thus corresponds
to a molar ratio of hydrogen to total mole fluorochloro-
ethane feed of 1:1 to 1.5:1. On the other hand with a
mixture of 3 moles CF2ClCF2Cl and 1 mole CC12FCF3
there may be employed 3 moles H2 per total mole of total
fluoroethane and this corresponds to 12 moles H2
per mole C12FCF3.
~- Atmospheric or superatmospheric pressures may be
employed.
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6.
The reactiorl temperature is suitably carried out ~n
the vapour phase at a temperature which is at least 200C
and not greater than 450C. Preferably the reaction
temperature is in the range 225C to 40~ac.
Contact times are usually in the ~ange 5 to 60 seconds
especially 5 to 30 seconds when the reaction is carried out
in the vapour phase.
The tetraEluoroethane product obtained depends to a
considerable extent on the choice of starting material.
When the organic starting material is 1,l~dic~loro-1,2,2j2-
tetrafluoroethane, l,1,1,2-tetrafluoroethane (asym tetra-
fluoroethane; CF3CH2F) is obtained almost to the
exclusion of 1,1,2,2-tetrafluoroethane tsym tetrafluoro-
e~hane, CHF2.CHF2). When the organic stàrting material
is 1,2-dichloro-1,1,2,2-tetra~luoroethane the reactian
, ~ product usually comprises a mixture o the twa isomers of
tetrafluoroethane. As the proportion of l,l-dichloro-
1,Z,2¦2-tetrafluoroethane with respect to 1,2-dichloro-
1,1,2,2-tetrafluoroethane is increased in a mixture thereof
increased amounts of the asymmetrical isomer CF3CH2F is
formed. Also an alumina support is especially useful for the
manufacture of CF3CH2F while an activated carbon support
is especially useful~in the manufacture of a mixture of
CF3CH2F and CHF2FHF2.
',
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7.
In the present process hydrogen and organic by-
prod~cts, for example, 2-chloro-1,1,1,2-tetrafluoro-
ethane may be recycled to the process. The desired
products of the present invention may be separated by
conventional means e.g. by fractional distillation.
Unreacted 1,2-dichloro-1,1,2,2-tetrafluoroethanè may if
desired be tapped off and used as a refrigerant.
The present process has the advantages that the
desirable l,1,1,2-tetraEluoroethane, 1,1,2,2-
tetrafluoroethane or mixtures thereo~ in variousproportions can be obtained by a simple and convenient
method. Desired products can be obtained in high
degree of purity with good conversions of the fluoro-
chloroethane starting material.
The following Examples illustrate the invention:-
EXAMPLE 1
Into a heat-resistant glass tube 30 cms long and
2.5 cms internal diameter, surrounded by an electric
furnace, were centrally placed 40 mls o~ a particulate
catalyst consisting of palladium supported on
charcoal~ This catalyst was intimately mixed with
40 mls glass helices to prevent clogging of the
catalyst. The palladium was present in the proportion
5% by weight with reference to the charcoal.
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~1~17
a.
Hydro~en and dichlorotetrafluoroethane (96.5~ hy
weight, 1,2-dichloro-1,1,2,2-tetra1uoroethane; 3.5~
by weight, l,l-dichloro-1,2,2,2-tetrafluoroethane) at
a molar ratio of 2:1 were passed through the heated
tube, the catalyst bed being maintained at various
reaction temperatures. The flow rates of organic
material and hydrogen were 50 cc/min and 100 cc/min,
respectively. The % v/v of organic materials in the
exit gas was determined by gas liauid chromatography.
The other reaction conditions and composition of
the organic products were as shown in Table 1.
TABLE I
.. . ._
Temperature C
Product
% v/v I ~ . ' 1---
240 300 1 330 1370
_
Contact time (secs.)
e
17.916.3 15.614.6
. . _____e-- _ __ __
CF3 CH2F 6.1 9.2 9.811.4
CHF2 CHF2 4.4 8.911.7
CHF CClF /
CHC~FCF32 3.620.1 21.321.4
:: .__ - . .... __
CClF CClF2i .
CCl2~Cp3 ~ 89.264.8 57.3 146.2
CF3CH3 0.6 1.5 1 2.2 3.3
Othe~- 0 5 5 9
EXAMPLE 2
The procedure of Example 1 was essentially
repeated but with a molar ratio of H2:organic
. starting material of 3:1. The flow rates of organic
material and hydrogen were 50 cc/min and 150 cc/min,
respectively. The other reaction conditions and composition
of the organic products were as shown in Table II.
TABLE II
_ . _I
Temperature C
Product
~ v/v 240 1 255 1 300 ~ 325
Contact time (secs.)
_ 12 8 12.-4 ~~ 11 4 ll.o
CF3.cH2F 11.3 9.9 9.7 8.1
: CHF2CHF2 7.4 17.6 29.6 35.9
.. ___ ..
:1 : CHF CClF2/
~1 CHC~FCF3 - 40.548.9 40.1 39.5
CClF .CClF2/
: CC12FCF3 . 39.421.4 17.3 10.8
:~ CF3.CH3 1.4 11.8 1 2.1 3.1
._ ~ - ~ !
I Others I ¦ 0.3 1.2 l 2.6
:
:~
10 .
EXAMPLE 3
.
The general proceclure of Example 2 was repeated
but with l,l-clichloro-1,2,2,2-tetrafluoroethane as
organic starting material. The other reaction conditions
and composition of the organic products were as
indicated in Table III.
TABLE III
. . . _
Temperature C
Product
%v/v .. _
. 285 310
Contact time (secs.)
.
: 1205 12.0
_
CF3.CH2F 71.7 72.0
- . ~ ........ . ___
CHF2.CHF2 0.9 ¦ 0.3
C~ClFCF /
:~ CF2ClCF32H 8.1 6.1
:~ .. .
lS ~ CClb2'C~1~2 11.
. CF3.CH3 1 8.3 1509
EXAMPLE 4
The general procedure of Example 2 was repeated
but with a mixture of 1,2-dichloro-1,1,2,2~tetra-
fluoroethane, (72% by weight) and l,l-dichloro-
S 1,2,2,2-tetrachloroethane (28~ by weight) as organic
starting material. The molar ratio of N2:the mixed
organic starting material WclS 3:1. The flow rates of
hydrogen and organic starting material were
150 cc/min and 50 cc/min, respectively. The reaction
temperature was 300C. The contact time was 12 seconds.
The composition of the organic product was as
given in Table IV.
TABLE IV
Product ~ v/v
;~ 15 CF3.CH2F l 37.6
.. _ ~._
CHF2CH~2 14.9
2CClF2/C~ClFCF3 26.8
CF3.CH3 13.0
. .
2 2/cFcl2cF3 7.7
, _
: ' ~
:
12.
ÆXAMPLE 5
The general procedure o~ Example 4 was repeated
except that the flow rate of hydrogen and the mixed organic
starting material and h~drogen was 100 cc/min and
33 cc/min, respectively, and the contact time
was 18 seconds.
The composition of the organic product was as
given in Table V.
TABLE V
I Product % v/v
_ _
. CF3 CH2F 46.2
~ .
CHF2CHF2 8.0
CHF CClF2/
CHC~FCF3 26
_
F3 CH3 ~8.2
.~ .
: : CClF2 CClF2/
2CF3 11.3
, . . .__ . ___
EXAMPLE 6
The general procedure of Example 5 was repeated
~:: except that the f~low rates:of hydrogen and organic starting
material were 90 cc/mln and 30 cc/min, respectively,
the contact time was l9 seconds and the reaction
temperature was 350C.
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:~
11~17~g~4
13.
The composition o~ the organic product was as given
in Table VI.
TABLE VI
Product % v/v
CF3 CH2F 41.~ ¦
.
CHF2 CHF2 16.3
.. _ , _
CHF CClF2/
CHC~FCF3 24.8
: . 3 3 11.8
¦ CClF2 CClF2/ 5.3
, CFC12CF3
~ ~ .
EXAMPLE 7
The general procedure of Example 2 was~repeated
but with 2-chloro-1,1,1,2-tetrafluoroethane as
starting material. The other reaction conditions and
composition of the organic product were as indicated
; 15 in Table VII.
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TABLE VII
,
Temperature C
Product
% v/v ~
280 1350 1420
Contact time (secs.)l
13 11 1 10
CF3 CH2F 82.0 94.1 95.8
CHF2 CHF2 0.8 0.8 0
CF3 CH3 1.4 2.9 3.3
.
CHClFCF3 15.7 2.3 0
C~F4 0 0.9
EXAMPLE 8
The apparatus comprised a heat-resistant glass tube
30 cms long and 2.5 cms internal diameter surrounded by
an electric furnace. Two part.culate catalysts were
employed which consisted of palladium (2% w/w and 5~ w/w)
~ supported on alumina.
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15.
Hydrogen and a mixture of 1,2-dichloro-1,1,2,2
tetrafluoroethane ~72~ by weight) and l,l-dichloro-
1,2,2,2-tetrafluoroethane (28% by weight) were passed
over the catalyst under various reaction conditions
as disclosed in Table VIII. The molar ratios of
hydrogen with respect to total dichlorotetrafluoroethane
starting material for Runs 1,2 and 3 were O.S:l, 0.5:1
of 0.75:1, respectively. The flow rates of H2 and
CC12FCF3 for these Runs were 50 and 25 cc/min,
50 and 25 cc/min, and 63 cc/min and 21 cc/min, respectively.
Thé % v/v of organic materials in the exit gas was
determined by gas liquid chromatography.
.
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TA~LE VI I I
j
Run 1 ¦Run 2 I Run 3
ff . . . I
Temperature C f
3~)0 ~ 2g5 1 300
Product Contact timfef ( secs)
~ v/v
. 10.6 1 10.3 I 16.3 ~ Pf~ in catalyst (w/w)
2 1- 5 1 2
Molar Ratio H2: CFC12CF3
.
2 1 2 1 1 3 1
.. ,
CF3CH2F 20 18 . 8 24 . 9
._. .. . : .
CHF2CHF2 _
. .. ~ .
I ~ ICHC1FCF /
~ CHF2CC1~2 2.6 0.4 ~ 0.3
~. I ~------
jCF3CH3 ~ 0.4 0.5 ¦0. 3
- ~_ - __ _ .
CC1F2CC1F2/ I I
j 15 CFC12CF3 62.5 171.9 I64.4
~: f . __ I ,
I ~1: Other fluoro~
chlor water C
;: compounds 2 j 10.9 5 . 7 f8 .0
- . . . ~ ,
,,
.
.
.
.
n~ 9L 4
17.
EXAMPLE 9
The apparatus comprised a vertical 'Inconel' tube
('Inconel' is a Registered Trade Mark) of 7.5 cms
internal diameter. The tube was packed to a height
of 90 cm with a catalyst in the form of spheres
(3 mm diameter) consisting of 2% w/w Pd supported on
alumina.
: Hydrogen and a mixture of l,2-dichloro-1,1,2,2-
tetrafluoroethane (50% by weight) and l,l-dichloro-
l,2,2,2-tetrafluoroethane (50% by weight) were passed
upwardly through the static catalyst under various
process conditions as disclosed in Table IX. The
molar ratios of hydrogen with respect to total
dichlorotetrafluoroethane starting material for Runs
1,2 and 3 were l.45:1, 1.6:l and l.6:l, respectively.
The flow rates of H2: CFC12CF3 for these runs
were 3.14 1 and 0.98 l/min, 3.81 l and l.lS l/min and
3.8 l and 1.15 1/min, respectively.
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TABLE IX
. . _ _ . . _ . . i , . _ ~ . _ _ . _
! I Run 1 I Run 2 ~ Run 2
~ --- I
, Temperature C
Product ~ ¦
v/v ~ ..... _
250 1 275 ~ 330
_ . .
Contact time (secs)
. ,~ .. _I
1 20 20
Molar ratio H2:CFCl2CF3
,. _ .
3.2:1 1 3.2:1 3.3:1
... ... _ 1 .. . _
CF3CH2F 46.l ~ 35.5 26.8
:.. _.. _ =_.___ _ __ - !
CHF2CHF2 _ _
~ . __
CHClFCF /
CHF2CC1~2 3.4 5.4 2.0
~ __ .
: : CF3CH3 l.6 1.9 1.2
_ ~............ ...... ............... ... .... .
CClF2CClF2/
:~ CFCl2CF3 45.8 54.6 69
.__~
:~ Other fluoro- I I
chloro C ' ¦
~: : 15 compound~ 0.5 1 0.5 0.4
1,1,1,2-tetrafluoroethane was recovered from the crude
reaction product by distillation in a glass apparatus
: consisting of a boiler, surmounted by a fractionation
column having 40 theoretical plates, a reflux divlder
and condenser. The apparatus was operated at atmospheric
' ~
144
19 .
pressure and after removal of lights boiling at
- 40C to -27C said 1,1,1,2 tetrafluoroethane was
eecovered as a top-product boiling at -26C.
EXAMPLE 10
The apparatus comprised a mild steel tube (5 cms
diameter) packed through 300 cms of its length with a
catalyst in the form of spheres (3 mm diameter) consisting
of 2% w/w Pd supported on alumlna.
5 Kgs per hour of a mixture of 1,2-dichloro-1,1,2,2-
tetrafluoroethane (50% by weight) and 1,1-dichloro-1,2,2,2-
tetrafluoroethane (50% by weight) and 770 l/hour of hydrogen
were passed upwardly through the static catalyst. The
pressure was 5 Bars gauge. The temperature of the catalyst
bed was maintained by a molten salt bath at 340C. The
contact time was 51 seconds. The molar ratio of
hydrogen with respect to total dichlorotetrafluoroethane
starting material was 1.1:1, the molar ratio of hydrogen
; ~ with respect to 1,1-dichloro-1,2,2,2-tetrafluoroethane
being 2.2:1.
The organic reaction product after washing with dilute
caustic soda solution and drying over calcium chloride was
condensed at -70C and comprised (v/v):
25% CF3CH2F
5% CF3CH3
5% CHClFCF3
65~ CF2ClCF2Cl/CF3CFC12
.
