Process for producing 1,1,2-tetrafluoroethane

A process for producing 1,1,1,2-tetrafluoroethane from trichloroethylene and HF, which comprises introducing products of a reaction of trichloroethylene with HF, and products of a reaction of 1,1,1-trifluoro-2-chloroethane with HF into a first distillation column either separately or as a mixture thereof, recovering HCl as a distillate from the top of the first distillation column, and introducing the remainder into a second distillation column.

FIELD OF THE INVENTION 
The present invention relates to a process for the production of 
1,1,1,2-tetrafluoroethane (hereinafter referred to as "CF.sub.3 --CH.sub.2 
F" or "HFC-134a") in which HFC-134a can be produced efficiently by 
reacting trichloroethylene (hereinafter referred to as "CHCl.dbd.CCl.sub.2 
" or "trichlene") with HF using simple equipment. 
BACKGROUND OF THE INVENTION 
In a conventionally known process for producing HFC-134a, trichlene is 
reacted with HF. The process is not accomplished in a single step, but 
effected by a two-step reaction in which the respective steps use 
different reaction conditions. This process comprises a first step 
reaction for reacting trichlene with HF to form 
1,1,1-trifluoro-2-chloroethane (hereinafter referred to as "CF.sub.3 
--CH.sub.2 Cl" or "HCFC-133a") and a second step reaction for reacting the 
HCFC-133a with HF to form HFC-134a. 
The first step reaction represented by the following scheme (1): 
EQU CHCl.dbd.CCl.sub.2 +3HF.fwdarw.CF.sub.3 --CH.sub.2 Cl+2HCl (1) 
is carried out, for example, under conditions of a pressure of 4 
kg/cm.sup.2 G, a temperature of 250.degree. C., and an HF/trichlene molar 
ratio of 6/1. 
The second step reaction represented by the following scheme (2 ): 
EQU CF.sub.3 --CH.sub.2 Cl+HF.fwdarw.CF.sub.3 --CH.sub.2 F+HCl (2) 
is carried out, for example, under conditions of a pressure of 4 
kg/cm.sup.2 G, a temperature of 350.degree. C., and an HF/HCFC-133a molar 
ratio of 4/1. 
In consequence, the prior art process comprises the steps of conducting the 
first step reaction under the above-described conditions, purifying the 
product to separate the HCl, re-adjusting the reaction conditions, 
conducting the second step reaction to yield HFC-134a, and then purifying 
and recovering the HFC-134a. This process has had a disadvantage that the 
distillation and separation steps are time-consuming, resulting in poor 
energy efficiency, due to the two reactions conducted under different 
conditions and each requiring its own distillation/separation step. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a simplified process for 
producing HFC-134a through reaction of trichloroethylene with HF, which 
comprises: 
reacting trichloroethylene with HF in a first reactor to form HCFC-133a, 
reacting HCFC-133a with HF in a second reactor to form HFC-134a, 
introducing the products from the first and second reactors into a first 
distillation column either separately or as a mixture thereof, 
recovering HCl as a distillate from the top of the first distillation 
column, and 
introducing the remainder into a second distillation column to obtain 
1,1,1,2-tetrafluoroethane.

DETAILED DESCRIPTION OF THE INVENTION 
One referred embodiment of the process of the present invention comprises 
reacting trichloroethylene with HF in a first reactor to form HCFC-133a, 
reacting HCFC-133a with HF in a second reactor to form HFC-134a, 
introducing the products from the first and second reactors into a first 
distillation column to separate the products into a column top distillate 
comprising HCl and a bottom liquid containing HFC-134a, HCFC-133a, and HF 
as main components and a small amount of trichloroethylene, and 
introducing the bottom liquid into a second distillation column to 
separate it into (i) a column top distillate comprising HFC-134a 
containing small amounts of HCFC-133a and HF, (ii) a side-cut fraction 
containing HCFC-133a and HF as main components, and (iii) a bottom liquid 
containing HF as a main component and a small amount of trichloroethylene. 
The term "side-cut fraction" herein used means a fraction discharged from 
a portion of the second distillation column located above the bottom 
portion but below the portion at which the first column bottom liquid is 
introduced. 
The second distillation column top distillate is introduced into a 
separately arranged purification step to recover the HFC-134a. The second 
distillation column side-cut fraction is fed to the second reactor while 
the bottom liquid is fed to the first reactor. If desired, the side-cut 
fraction may be mixed with HF to adjust their molar ratio before it is fed 
to the second reactor, and the bottom liquid may also be mixed with 
trichloroethylene and HF to adjust their molar ratio before it is fed to 
the first reactor. 
The presence of HCl which has a very high specific volatility makes it 
difficult to operate distillation to separate HFC-134a, HCFC-133a and HF. 
According to the process of the present invention, however, HCl is 
eliminated from the top of the first distillation column so that the 
subsequent distillation(s) for separation of HFC-134a, HCFC-133a and HF 
can be stably and effectively conducted. 
In another embodiment of the process, the above-described side-cutting in 
the second distillation column is not conducted and the first column 
bottom liquid introduced into the second distillation column is separated 
into (i) a second column top distillate containing HFC-134a as a main 
component and small amounts of HCFC-133a, HF, etc. and (ii) a bottom 
liquid containing HCFC-133a and HF as main components and a small amount 
of trichloroethylene. The column top distillate is introduced into a 
separately arranged purification step to recover the HFC-134a. On the 
other hand, the bottom liquid is introduced into a third distillation 
column to separate it into a column top distillate containing HCFC-133a as 
a main component and further containing HF and a bottom liquid containing 
a small amount of trichloroethylene, and the column top distillate is fed 
to the second reactor (after HF is added thereto and their molar ratio is 
adjusted if desired), while the bottom liquid is fed to the first reactor 
(after trichloroethylene and HF are added thereto and their molar ratio 
and amounts are adjusted if desired). 
In still another embodiment which also does not conduct the side-cutting, 
the first column bottom liquid introduced into the second distillation 
column is separated into a column top distillate containing HFC-134a, 
HCFC-133a, and HF as main components and a bottom liquid containing HF as 
a main component and a small amount of trichloroethylene. The column top 
distillate is introduced into a third distillation column to separate it 
into a column top distillate containing HFC-134a as a main component and 
small amounts of HCFC-133a, HF, etc. and a bottom liquid containing 
HCFC-133a as a main component and further containing HF, and the third 
distillation column top distillate is introduced into a separately 
arranged purification step to recover the HFC-134a. The second 
distillation column bottom liquid is fed to the first reactor (after 
trichloroethylene and HF are added thereto and their molar ratio and 
amounts are adjusted if desired), while the third distillation column 
bottom liquid is fed to the second reactor (after HF is added thereto and 
their molar ratio is adjusted if desired). 
FIG. 1 is a flow sheet showing one embodiment of the process of the present 
invention for producing HFC-134a. In FIG. l, numeral 1 denotes a first 
reactor and 2 denotes a second reactor. 
The reaction in first reactor 1 may be carried out under a pressure of from 
0 to 6 kg/cm.sup.2 G, preferably from 0 to 4 kg/cm.sup.2 G at a 
temperature of from 200.degree. to 350.degree. C., preferably from 
250.degree. to 300.degree. C. with the HF/trichloroethylene mol ratio of 
from 4/1 to 20/1, preferably from 6/1 to 10/1, for example, under a 
pressure of 4 kg/cm.sup.2 G, at a temperature of 250.degree. C. and with 
an HF/trichloroethylene mol ratio of 6/1. The reaction in second reactor 2 
may be carried out under a pressure of from 0 to 6 kg/cm.sup.2 G, 
preferably from 0 to 4 kg/cm.sup.2 G, at a temperature of from 300.degree. 
to 380.degree. C., preferably from 300.degree. to 360.degree. C. with the 
HF/HCFC-133a mol ratio of from 2/1 to 10/1, preferably from 4/1 to 8/1, 
for example, under a pressure of 4 kg/cm.sup.2 G, at a temperature of 
350.degree. C. and with an HF/HCFC 133a mol ratio of 4/1. 
Reaction products from the first and second reactors are introduced as 
reaction products 15, either separately or as a mixture thereof, into 
first distillation column 3. 
In the first distillation column, reaction products 15 are separated into 
first column top distillate 16 and first column bottom liquid 17. First 
column top distillate 16, which contains HCl as a main component, is put 
to other use. First column bottom liquid 17, which contains HFC-134a, 
HCFC-133a, and HF as main components and a small amount of 
trichloroethylene, is introduced into second distillation column 4. 
The first distillation is generally carried under the following conditions: 
pressure of from 2 to 10 kg/cm.sup.2 G, preferably from 4 to 6 kg/cm.sup.2 
G; top temperature of from -65.degree. to -30.degree. C. preferably from 
-52.degree. to -43.degree. C.; bottom temperature of from 25.degree. to 
68.degree. C., preferably from 41.degree. to 52.degree. C.; and relux 
ratio of from 10 to 30, preferably from 14 to 20. 
In the second distillation column, first column bottom liquid 17 is 
separated into second column top distillate 18, second column side-cut 
fraction 19, and second column bottom liquid 20. Second column top 
distillate 18, which comprises HFC-134a containing small amounts of 
HCFC-133a, HF, etc., is introduced into a separately arranged purification 
step 5 to recover the HFC-134a. The HCFC-133a and HF contained in second 
column top distillate 18 are separated in this step and optionally used as 
feed material 13 for 14 for the first or second reactor, respectively. 
Purification step 5 may be conducted using another distillation column. 
Second column side-cut fraction 19, which contains HCFC-133a and HF as main 
components, is fed as feed material 14 to the second reactor after HF is 
added thereto and their molar ratio is adjusted. Second column bottom 
liquid 20 consists mainly of HF containing a small amount of 
trichloroethylene. Although a part of the bottom liquid may be used for 
the adjustment of the feed material for the second reactor, most of the 
bottom liquid is used as feed material 13 for the first reactor after 
fresh HF and trichloroethylene are added thereto and their molar ratio and 
amounts are adjusted. 
The second distillation is generally carried out under the following 
conditions: pressure of from 2 to 10 kg/cm.sup.2 G, preferably from 4 to 6 
kg/cm.sup.2 G; top temperature of from 2.degree. to 43.degree. C., 
preferably from 16.degree. to 27.degree. C.; temperature at side-cut 
portion of from 25.degree. to 67.degree. C., preferably from 41.degree. to 
52.degree. C.; bottom temperature of from 54.degree. to 100.degree. C., 
preferably from 71.degree. to 84.degree. C.; and reflux ratio of from 5 to 
20, preferably from 8 to 15. 
Numerals 11 and 12 denote HF and trichloroethylene, respectively, to be 
introduced into the system. 
Due to the above-described construction of the equipment for the present 
invention, the products from the first and second reactors are introduced, 
either separately or as a mixture thereof, into the distillation columns, 
i.e., the first and second distillation columns, where they are separated 
into HFC-134a as the desired product, HCl as a by-product, an HF fraction 
containing a small amount of trichloroethylene usable for feed material 
adjustment, and a side-cut fraction to be used as a feed material for the 
second reactor. These fractions are subjected to the reaction and 
distillation/separation steps in combination with fresh trichloroethylene 
and HF as supplementary materials. Therefore, HFC-134a can be produced 
efficiently using a small number of apparatuses. 
FIGS. 2 and 3 illustrate the other embodiments of the present invention, in 
both of which side-cutting is not conducted in the second distillation 
column. 
In the embodiment of FIG. 2, an HFC-134a fraction containing small amounts 
of HCFC-133a, HF, etc. is taken out from the top of the second 
distillation column, while the remainder is drawn off from the bottom and 
introduced into a third distillation column where a fraction consisting 
mainly of HCFC-133a containing HF is taken out from the top and a liquid 
consisting mainly of HF containing a small amount of trichloroethylene is 
drawn off from the bottom. 
In this embodiment, the second distillation conditions are the same as 
those in the previous embodiment and the third distillation conditions 
are: pressure of from 2 to 10 kg/cm.sup.2 G, preferably from 4 to 6 
kg/cm.sup.2 G; top temperature of from 25.degree. to 67.degree. C., 
preferably from 41.degree. to 52.degree. C.; bottom temperature of from 
54.degree. to 100.degree. C., preferably from 71.degree. to 84.degree. C.; 
and reflux ratio of from 0.5 to 10, preferably from 1.5 to 5. 
In the embodiment of FIG. 3, a liquid consisting mainly of HF containing a 
small amount of trichloroethylene is drawn off from the bottom of the 
second distillation column, while the remainder is taken out from the top 
and introduced into a third distillation column where an HFC-134a fraction 
containing small amounts of HCFC-133a, HF, etc. is taken out from the top 
and a liquid consisting mainly of HCFC-133a containing HF is drawn off 
from the bottom. 
In this embodiment, the second distillation conditions are: pressure of 
from 2 to 10 kg/cm2G, preferably from 4 to 6 kg/cm.sup.2 G; top 
temperature of from 25.degree. to 67.degree. C., preferably from 
41.degree. to 52.degree. C.; bottom temperature of from 54.degree. to 
100.degree. C., preferably from 71.degree. to 84.degree. C.; and reflux 
ratio of from 0 to 10, preferably from 0 to 5. The third distillation 
conditions are: pressure of from 2 to 10 kg/cm.sup.2 G, preferably from 4 
to 6 kg/cm.sup.2 G; top temperature of from 2.degree. to 43.degree. C., 
preferably from 16.degree. to 27.degree. C.; bottom temperature of from 
25.degree. to 67.degree. C. preferably from 41.degree. to 52.degree. C.; 
and reflux ratio of from 5 to 20, preferably from 8 to 15. 
In FIG. 2 and 3, numeral 6 denote a third distillation column; 21 a second 
distillation column bottom liquid; 22 a third distillation column top 
distillate; 23 a third distillation column bottom liquid; 25 a second 
distillation column top distillate; 26 a second distillation column bottom 
liquid; 27 a third distillation column top distillate; 28 a third 
distillation column bottom liquid; and 5' a purification step, for 
example, using another distillation column and/or involving a purification 
treatment as described in U.S. patent application Ser. No. 08/056783 filed 
May 4, 1993. 
Although the embodiments shown in FIGS. 2 and 3 each additionally 
necessitates the third distillation column, the stability of operation is 
improved because of elimination of the side-cutting in the second 
distillation column. 
The present invention is explained in more detail with reference to the 
following Examples which were conducted in accordance with the flow sheets 
shown in FIGS. 1 to 3. In these Examples, the component amounts in each 
part are given in terms of percent by weight, and the flow rate of each 
component in each part is shown as a relative value with the flow rate of 
the reaction products discharged from the first and second reactors and to 
be introduced into the first distillation column either separately or as a 
mixture thereof being taken as 100. 
EXAMPLE 1 
A test run was conducted in accordance with the flow sheet of FIG. 1. The 
results obtained are shown in Table 1, in which the Nos. correspond to the 
respective numerals in FIG. 1. 
TABLE 1 
__________________________________________________________________________ 
Component 
11 12 13 14 15 16 17 18 19 20 
__________________________________________________________________________ 
Flow Rate: 
HFC-134a 
-- -- -- -- 8.8 
-- 8.8 
8.8 
-- -- 
HCFC-133a 
-- -- -- 44.1 
44.8 
-- 44.8 
0.8 
44.0 
-- 
HF 7.2 
-- 11.1 
29.7 
33.8 
-- 33.8 
0.2 
7.5 
26.1 
HCl -- -- -- -- 8.7 
8.7 
-- -- -- -- 
Trichlene 
-- 11.6 
12.2 
0.8 
1.4 
-- 1.4 
-- -- 1.4 
Others -- -- 0.2 
1.8 
2.5 
-- 2.5 
0.5 
0.9 
1.1 
Total 7.2 
11.6 
23.5 
76.4 
100 
8.7 
91.3 
10.3 
52.4 
28.6 
Component 
HFC-134A 
-- -- -- -- 8.8 
-- 9.64 
85.44 
-- -- 
Proportion: 
HCFC-133a 
-- -- -- 57.72 
44.8 
-- 49.07 
7.77 
83.97 
-- 
by weight (%) 
HF 100 
-- 47.23 
38.87 
33.8 
-- 37.02 
1.94 
14.31 
91.25 
HCl -- -- -- -- 8.7 
100 
-- -- -- -- 
Trichlene 
-- 100 
51.92 
1.05 
1.4 
-- 1.53 
-- -- 4.90 
Others -- -- 0.85 
2.36 
2.5 
-- 2.74 
4.85 
1.72 
3.85 
Total 100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
__________________________________________________________________________ 
As evident from Table 1, the reaction products introduced either separately 
or as a mixture thereof are separated by the two distillation columns, and 
the feed materials for the first and second reactors are adjusted by 
combining these fractions with supplementary trichlene and HF, while the 
by-product HCl is recovered and the desired HFC-134a is concentrated. 
EXAMPLE 2 
A test run was conducted in accordance with the flow sheet of FIG. 2. The 
results obtained are shown in Table 2, in which the Nos. correspond to the 
respective numerals in FIG. 2. 
TABLE 2 
__________________________________________________________________________ 
Component 
11 12 13 14 15 16 17 18 21 22 23 
__________________________________________________________________________ 
Flow Rate: 
HFC-134a 
-- -- -- -- 8.8 
-- 8.8 
8.8 
-- -- -- 
HCFC-133a 
-- -- -- 44.1 
44.8 
-- 44.8 
0.8 
44.0 
44.0 
-- 
HF 7.2 
-- 11.1 
29.7 
33.8 
-- 33.8 
0.2 
33.6 
7.5 
26.1 
HCl -- -- -- -- 8.7 
8.7 
-- -- -- -- -- 
Trichlene 
-- 11.6 
12.2 
0.8 
1.4 
-- 1.4 
-- 1.4 
-- 1.4 
Others -- -- 0.2 
1.8 
2.5 
-- 2.5 
0.5 
2.0 
0.9 
1.1 
Total 7.2 
11.6 
23.5 
76.4 
100 
8.7 
91.3 
10.3 
81.0 
52.4 
28.6 
Component 
HFC-134A 
-- -- -- -- 8.8 
-- 9.64 
85.44 
-- -- -- 
Proportion: 
HCFC-133a 
-- -- -- 57.72 
44.8 
-- 49.07 
7.77 
54.32 
-- -- 
by weight (%) 
HF 100 
-- 47.23 
38.87 
33.8 
-- 37.02 
1.94 
41.48 
83.97 
91.25 
HCl -- -- -- -- 8.7 
100 
-- -- -- 14.31 
-- 
Trichlene 
-- 100 
51.92 
1.05 
1.4 
-- 1.53 
-- 1.73 
-- 4.90 
Others -- -- 0.85 
2.36 
2.5 
-- 2.74 
4.85 
2.47 
1.72 
3.85 
Total 100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
__________________________________________________________________________ 
EXAMPLE 3 
A test run was conducted in accordance with the flow sheet of FIG. 3. The 
results obtained are shown in Table 3, in which the Nos. correspond to the 
respective numerals in FIG. 3. 
TABLE 3 
__________________________________________________________________________ 
Component 
11 12 13 14 15 16 17 25 26 27 28 
__________________________________________________________________________ 
Flow Rate: 
HFC-134a 
-- -- -- -- 8.8 
-- 8.8 
8.8 
-- 8.8 
-- 
HCFC-133a 
-- -- -- 44.1 
44.8 
-- 44.8 
44.8 
-- 0.8 
44.0 
HF 7.2 
-- 11.1 
29.7 
33.8 
-- 33.8 
7.7 
26.1 
0.2 
7.5 
HCl -- -- -- -- 8.7 
8.7 
-- -- -- -- -- 
Trichlene 
-- 11.6 
12.2 
0.8 
1.4 
-- 1.4 
-- 1.4 
-- -- 
Others -- -- 0.2 
1.8 
2.5 
-- 2.5 
1.4 
1.1 
0.5 
0.9 
Total 7.2 
11.6 
23.5 
76.4 
100 
8.7 
91.3 
62.7 
28.6 
10.3 
52.4 
Component 
HFC-134a 
-- -- -- -- 8.8 
-- 9.64 
14.04 
-- 85.44 
-- 
Proportion: 
HCFC-133a 
-- -- -- 57.72 
44.8 
-- 49.07 
71.45 
-- 7.77 
83.97 
by weight (%) 
HF 100 
-- 47.23 
38.87 
33.8 
-- 37.02 
12.28 
91.25 
1.94 
14.31 
HCl -- -- -- -- 8.7 
100 
-- -- -- -- -- 
Trichlene 
-- 100 
51.92 
1.05 
1.4 
-- 1.53 
-- 4.90 
-- -- 
Others -- -- 0.85 
2.36 
2.5 
-- 2.74 
2.23 
3.85 
4.85 
1.72 
Total 100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
__________________________________________________________________________ 
As described above, in the HFC-134a production process of the present 
invention, reaction products from the first and second reactors are 
subjected together to distillation and separation either separately or as 
a mixture thereof and the feed materials for the reactors are adjusted by 
combining the resulting fractions with supplementary trichlene and HF, 
whereas in the prior art process, the reaction products from the first 
reactor and those from the second reactor are separately treated in 
respective distillation and separation steps and the feed materials for 
the reactors are adjusted by combining the resulting fractions with 
supplementary trichlene and HF. Because of the above-inventioned 
difference, the process of the invention has advantages in that the 
distillation step is simple and the energy unit is small. 
While the invention has been described in detail and with reference to 
specific embodiments thereof, it will be apparent to one skilled in the 
art that various changes and modifications can be made therein without 
departing from the spirits and scope thereof.