Method for producing difluoromethane and 1,1,1,2-tetrafluoroethane

According to the method for producing difluoromethane and 1,1,1,2-tetrafluoroethane, having the steps of: (1) reacting methylene chloride and 1,1,2-trichloroethylene with hydrogen fluoride in a vapor phase In the presence of a fluorinating catalyst and 1,1,1,2-tetrafluoroethane in a first reactor; and (2) reacting 1,1,1-trifluorochloroethane with hydrogen fluoride in a vapor phase in the presence of a fluorinating catalyst in a second reactor, and supplying the reaction mixture from the second reactor to the first reactor, HFC-32 can be obtained in high conversion and high selectivity by fluorinating HCC-30 using commonly a large (excess) amount of HF which is required for producing HFC-134a.

CROSS REFERNCE 
This application is a 371 of PCT/IP94/02070 filed Dec. 09, 1994. 
FIELD OF THE INVENTION 
The present invention relates to a method for producing difluoromethane and 
1,1,1,2-tetrafluoroethane. Difluoromethane and 1,1,1,2-tetrafluoroethane 
are alternative fluorocarbons, and are useful as a cooling medium and the 
like. 
DESCRIPTION OF RELATED ART 
As the method for producing difluoromethane (CH.sub.2 F.sub.2, HFC-32), a 
liquid phase synthesis process (cf. U.S. Pat. No. 2,749,373) and vapor 
phase synthesis process (cf. Japanese Patent Publication Nos. 3004/1967 
and 2251321/1984) comprising using methylene chloride (CH.sub.2 Cl.sub.2, 
HCC-30) as a raw material are known. 
It is a known fact that it is difficult to react methylene chloride in good 
conversion according to the vapor phase synthesis process (cf. "Chemistry 
and Industry of Fluorine Compound", page 267, published on December 1977 
and Japanese Patent Publication No. 3004/1967). It is possible to increase 
the conversion of methylene chloride by using excess HF relative to 
methylene chloride. However, a large amount of HF must be disposed or 
recovered and, therefore, an economical disadvantage arises (cf. Japanese 
Patent Kokai Publication No. 2251321/1984). 
Japanese Patent Kokai Publication No. 2942371/1991 discloses a process 
comprising reacting 1,1,1-trifluorochloroethane (HCFC-133a) with HF to 
obtain 1,1,1,2-tetrafluoroethane (HFC-134a), adding 
1,1,2-trichloroethylene (HCC-1120) to a crude reaction gas to conduct the 
reaction from HCC-1120 into HCFC-133a in another reactor without exerting 
an influence on the other gas and recycling the formed 133a and a HF, as a 
process for producing efficiently 1,1,1-trifluorochloroethane (HCFC-133a) 
and 1,1,1,2-tetrafluoroethane (HFC-134a). 
The conversion reaction from HCC-1120 into HCFC-133a is a largely 
exothermic reaction, and it is suggested that the prevention of a heat 
spot formation in a catalyst layer by the reaction is useful to prolong 
the catalytic life. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a method for effectively 
and simultaneously producing difluoromethane and 1,1,1,2-tetrafluoroethane 
in one apparatus. 
The present invention provides a method for producing difluoromethane and 
1,1,1,2-tetrafluoroethane, comprising the steps of: 
(1) reacting methylene chloride with hydrogen fluoride in a vapor phase at 
a reaction temperature of 180.degree. to 320.degree. C. in the presence of 
a fluorinating catalyst and 1,1,1,2-tetrafluoroethane to give 
difluoromethane, and reacting 1,1,2-trichloroethylene with hydrogen 
fluoride to give 1,1,1-trifluorochloroethane, in a first reactor, 
(2) reacting 1,1,1-trifluorochloroethane with hydrogen fluoride in a vapor 
phase at a reaction temperature of 280.degree. to 400.degree. C., which is 
higher than the reaction temperature of the first reactor, in the presence 
of a fluorinating catalyst to give 1,1,1,2-tetrafluoroethane in a second 
reactor, and supplying the reaction mixture from the second reactor to the 
first reactor; 
(3) recovering difluoromethane, 1,1,1,2-tetrafluoroethane and hydrogen 
chloride from the reaction mixture of the first reactor; and 
(4) supplying the remainder of the reaction mixture containing 
1,1,1-trifluorochloroethane from the first reactor to the second reactor 
after recovering in the step (3). 
In addition, the present invention provides a method for producing 
difluoromethane and 1,1,1,2-tetrafluoroethane, comprising the steps of: 
(1) reacting methylene chloride with hydrogen fluoride in a vapor phase at 
a reaction temperature of 180.degree. to 320.degree. C. in the presence of 
a fluorinating catalyst and 1,1,1,2-tetrafluoroethane to give 
difluoromethane, and reacting 1,1,2-trichloroethylene with hydrogen 
fluoride to give 1,1,1-trifluorochloroethane, in a first reactor, 
(2) reacting 1,1,1-trifluorochloroethane with hydrogen fluoride in a vapor 
phase at a reaction temperature of 280.degree. to 400.degree. C. which is 
higher than the reaction temperature of the first reactor in the presence 
of a fluorinating catalyst to give 1,1,1,2-tetrafluoroethane in a second 
reactor, and supplying the reaction mixture from the second reactor to the 
first reactor; 
(3) reacting the reaction mixture from the first reactor with hydrogen 
fluoride in a vapor phase at a reaction temperature of 150.degree. to 
240.degree. C., which is lower than the reaction temperature of the first 
reactor, in the presence of a fluorinating catalyst to reduce an amount of 
methylene chloride existing in the reaction mixture, in a third reactor; 
(4) recovering difluoromethane, 1,1,1,2-tetrafluoroethane and hydrogen 
chloride from the reaction mixture of the third reactor; and 
(5) supplying the remainder of the reaction mixture containing 
1,1,1-trifluorochloroethane from the third reactor to the second reactor 
after recovering in the step (4). 
Further, the present invention provides a method for producing 
difluoromethane and 1,1,1,2-tetrafluoroethane, comprising the steps of: 
(1) reacting methylene chloride with hydrogen fluoride in a vapor phase at 
a reaction temperature of 180.degree. to 320.degree. C. in the presence of 
a fluorinating catalyst and 1,1,1,2-tetrafiuoroethane to give 
difluoromethane, and reacting 1,1,2-trichloroethylene with hydrogen 
fluoride to give 1,1,1-trifluorochloroethane, in a first reactor; 
(2) reacting 1,1,1-trifluorochloroethane with hydrogen fluoride in a vapor 
phase at a reaction temperature of 280.degree. to 400.degree. C., which is 
higher than the reaction temperature of the first reactor, in the presence 
of a fluorinating catalyst to give 1,1,1,2-tetrafluoroethane in a second 
reactor, and supplying the reaction mixture from the second reactor to the 
first reactor; 
(3) reacting the reaction mixture from the first reactor with hydrogen 
fluoride in a vapor phase at a reaction temperature of 150.degree. to 
240.degree. C., which is lower than the reaction temperature of the first 
reactor, in the presence of a fluorinating catalyst to reduce an amount of 
methylene chloride existing in the reaction mixture, in a third reactor; 
(4) reacting the reaction mixture from the third reactor with hydrogen 
fluoride in a vapor phase at 100.degree. to 190.degree. C., which is lower 
than te reaction temperature of the third reactor, in the presence of a 
fluorinating catalyst, in at least one fourth reactor; 
(5) recovering difluoromethane, 1,1,1,2-tetrafluoroethane and hydrogen 
chloride from the reaction mixture from the fourth reactor; and 
(6) supplying the remainder of the reaction mixture containing 
1,1,1-trifluorochloroethane from the fourth reactor to the second reactor 
after recovering in the step (5). 
The present invention further provides a method for producing 
difluoromethane and 1,1,1,2-tetrafluoroethane, comprising the steps of: 
(1) reacting methylene chloride with hydrogen fluoride in a vapor phase at 
a reaction temperature of 180.degree. to 320.degree. C. in the presence of 
a fluorinating catalyst and 1,1,1,2-tetrafluoroethane to give 
difluoromethane, and reacting 1,1,2-trichloroethylene with hydrogen 
fluoride to give 1,1,1-trifluorochloroethane, in a first reactor; 
(2) reacting 1,1,1-trifluorochloroethane with hydrogen fluoride in a vapor 
phase at a reaction temperature of 280.degree. to 400.degree. C., which is 
higher than the reaction temperature of the first reactor, in the presence 
of a fluorinating catalyst to give 1,1,1,2-tetrafluoroethane in a second 
reactor, and supplying the reaction mixture from the second reactor to the 
first reactor; 
(3) recovering difluoromethane, 1,1,1,2-tetrafluoroethane and hydrogen 
chloride from the reaction mixture of the first reactor; and 
(4) reacting the remainder of the reaction mixture containing 
1,1,1-trifluorochloroethane from the first reactor with hydrogen fluoride 
in a vapor phase at a temperature of 170.degree. to 320.degree. C. in the 
presence of a fluorinating catalyst in a fifth reactor after recovering in 
the step (3), and supplying the reaction mixture from the fifth reactor to 
the second reactor. 
The present invention further provides a method for producing 
difluoromethane and 1,1,1,2-tetrafluoroethane, comprising the steps of: 
(1) reacting methylene chloride with hydrogen fluoride in a vapor phase at 
a reaction temperature of 180.degree. to 320.degree. C. in the presence of 
a fluorinating catalyst and 1,1,1,2-tetrafluoroethane to give 
difluoromethane, and reacting 1,1,2-trichloroethylene with hydrogen 
fluoride to give 1,1,1,-trifluorochloroethane, in a first reactor; 
(2) reacting 1,1,1-trifluorochloroethane with hydrogen fluoride in a vapor 
phase at a reaction temperature of 280.degree. to 400.degree. C., which is 
higher than the reaction temperature of the first reactor, in the presence 
of a fluorinating catalyst to give 1,1,1,2-tetrafluoroethane in a second 
reactor, and supplying the reaction mixture from the second reactor to the 
first reactor; 
(3) reacting the reaction mixture from the first reactor with hydrogen 
fluoride in a vapor phase at 150.degree. to 240.degree. C., which is lower 
than the reaction temperature of the first reactor, in the presence of a 
fluorinating catalyst to reduce an amount of methylene chloride existing 
in the reaction mixture, in a third reactor; 
(4) recovering difluoromethane, 1,1,1,2-tetrafluoroethane and hydrogen 
chloride from the reaction mixture of the third reactor; and 
(5) reacting the remainder of the reaction mixture containing 
1,1,1-trifluorochloroethane from the third reactor with hydrogen fluoride 
in a vapor phase at a temperature of 170.degree. to 320.degree. C. in the 
presence of a fluorinating catalyst in a fifth reactor after recovering in 
the step (4), and supplying the reaction mixture from the fifth reactor to 
the second reactor. 
The present invention further provides a method for producing 
difluoromethane and 1,1,1,2-tetrafluoroethane, comprising the steps of: 
(1) reacting methylene chloride with hydrogen fluoride in a vapor phase at 
a reaction temperature of 180.degree. to 320.degree. C. in the presence of 
a fluorinating catalyst and 1,1,1,2-tetrafluoroethane to give 
difluoromethane, and reacting 1,1,2-trichloroethylene with hydrogen 
fluoride to give 1,1,1-trifluorochloroethane, in a first reactor; 
(2) reacting 1,1,1-trifluorochloroethane with hydrogen fluoride in a vapor 
phase at a reaction temperature of 280.degree. to 400.degree. C., which is 
higher than the reaction temperature of the first reactor, in the presence 
of a fluorinating catalyst to give 1,1,1,2-tetrafluoroethane in a second 
reactor, and supplying the reaction mixture from the second reactor to the 
first reactor; 
(3) reacting the reaction mixture from the first reactor with hydrogen 
fluoride in a vapor phase at 150.degree. to 240.degree. C., which is lower 
than the reaction temperature of the first reactor, in the presence of a 
fluorinating catalyst to reduce an amount of methylene chloride existing 
in the reaction mixture, in a third reactor; 
(4) reacting the reaction mixture from the third reactor with hydrogen 
fluoride in a vapor phase at 100.degree. to 190.degree. C., which is lower 
than the reaction temperature of the third reactor, in the presence of a 
fluorinating catalyst, in at least one fourth reactor; 
(5) recovering difluoromethane, 1,1,1,2-tetrafluoroethane and hydrogen 
chloride from the reaction mixture of the fourth reactor; and 
(6) reacting the remainder of the reaction mixture containing 
1,1,1-trifluorochoroethane from the fourth reactor with hydrogen fluoride 
in a vapor phase at a temperature of 170.degree. to 320.degree. C. in the 
presence of a fluorinating catalyst in a fifth reactor after recovering in 
the step (5), and supplying the reaction mixture from the fifth reactor to 
the second reactor.

DETAILED DESCRIPTION OF THE INVENTION 
In the present invention, it is preferred to recover the unreacted 
methylene chloride (HCC-30) and/or chlorofluoromethane (HCFC-31, CH.sub.2 
FCl) existing in the reaction mixture obtained from (a) the first reactor 
when no third reactor exists, (b) the third reactor when the first and 
third reactors exist or (c) the fourth reactor when the first, third and 
fourth reactor exists, and to recycle the recovered HCC-30 and/or HCFC-31 
to the first or third reactor. These gases can be recovered from the 
reaction mixture by operations such as an extraction, a two phase 
separation, a fractional distillation, etc. When the reaction mixture is 
fed to the second reactor without recovering HCC-30 and HCFC-31, the 
following reactions can arise in the second reactor. 
HCC-30+2HF.fwdarw.HFC-32+2HCl 
HCFC-31+HF.fwdarw.HFC-32+HCl 
It is supposed that the resultant HCl decreases the conversion from 
HCFC-133a into HFC-134a. However, a decrease in conversion becomes small 
by decreasing the amount of the unreacted HCC-30 and HCFC-31 which are fed 
to the second reactor, so that the production efficiency of HFC-134a is 
increased. 
The method of the present invention uses 
(a) the first and second reactors, 
(b) the first to third reactors, 
(c) the first to fourth reactors, 
(d) the first, second and fifth reactors, 
(e) the first, second, third and fifth reactors, or 
(f) the first to fifth reactors. 
FIG. 1 is a schematic diagram illustrating an apparatus for conducting the 
method of the present invention using first and second reactors. This 
apparatus has a first reactor 11, a second reactor 12, and a separator 16 
for recovering HFC-134a, HFC-32 and hydrogen chloride. 
FIG. 2 is a schematic diagram illustrating another embodiment of an 
apparatus for conducting the method of the present invention using first 
and second reactors. In this apparatus, the unreacted HCC-30 and/or 
HCFC-31 in the mixture obtained from the first reactor 11 are separated, 
and then the unreacted HCC-30 and/or HCFC-31 are supplied to the first 
reactor 11. 
FIG. 3 is a schematic diagram illustrating an apparatus for conducting the 
method of the present invention using first to third reactors. This 
apparatus has a first reactor 21, a second reactor 22, a third reactor 23, 
and a separator 26 for recovering HFC-134a, HFC-32 and hydrogen chloride. 
FIG. 4 is a schematic diagram illustrating an apparatus for conducting the 
method of the present invention using first to fourth reactors. This 
apparatus has a first reactor 31, a second reactor 32, a third reactor 33, 
a fourth reactor 34, and a separator 36 for recovering HFC-134a, HFC-32 
and hydrogen chloride. 
FIG. 5 is a schematic diagram illustrating an apparatus for conducting the 
method of the present invention using first, second and fifth reactors. 
This apparatus has a first reactor 41, a second reactor 42, a fifth 
reactor 45 and a separator 46 for recovering HFC-134a, HFC-32 and hydrogen 
chloride. 
FIG. 6 is a schematic diagram illustrating a apparatus for conducting the 
method of the present invention using first to fifth reactors. This 
apparatus has a first reactor 101, a second reactor 102, a third reactor 
103, a fourth reactor 104, a fifth reactor 105, and a separator 106 for 
recovering HFC-134a, HFC-32 and hydrogen chloride. It is also possible to 
use an embodiment wherein no fourth reactor 104 exists. 
In the first reactor, methylene chloride (HCC-30) is reacted with hydrogen 
fluoride in a vapor phase at a reaction temperature of 180.degree. to 
320.degree. C. in the presence of a fluorinating catalyst and 
1,1,1,2-tetrafluoroethane (HFC-134a) to give difluoromethane (HFC-32), and 
then 1,1,2-trichloroethylene (HCC-1120) is reacted with hydrogen fluoride 
to give 1,1,1-trifluorochloroethane (HCFC-133a). HFC-134a acts as a 
diluting agent for reducing a concentration of HCC-1120 and hydrogen 
fluoride. 
In the first reactor, the following reactions arise. 
EQU HCC-1120+3HF=HCFC-133a+2HCl+.DELTA.29 kcal (exothermic) (1) 
EQU HCC-30+2HF=HFC-32+2HCl-.DELTA.2 kcal (endothermic) (2) 
It is also possible that the following reaction arises. 
EQU HFC-134a+HCl.fwdarw.HCFC-133a+HF (3) 
HCl is generated according to the formula (1) and (2). It is supposed that 
the generated HCl gives an adverse influence on HFC-134a formation because 
.DELTA.G (Gibbs energy) of the reaction from HCFC-133a into HFC-134a is 
smaller than that of the formula (1). In the present invention, however, 
the actual conversion from HFC-134a into HCFC-133a is smaller than an 
expected value derived from a relationship of the equilibrium constant and 
the concentration of the raw material and the resulting system. 
Accordingly, it is possible to produce efficiently HCFC-133a and HCFC-32 
without disadvantageous reaction from HFC-134a into HCFC-133a. The 
exothermic reaction (formula (1)) and the endothermic reaction (formula 
(2)) are combined and, therefore, the efficiency of energy is good and it 
contributes to prevent the formation of heat spot in the reactor. 
In the first reactor, HCFC-133a and HFC-32 can be produced efficiently. 
Since HFC-134a acts as a diluting agent for reducing the concentration of 
HCC-1120 and HF which are the raw material, the control of the reaction 
heat becomes easier and more efficient. Similarly, an excess amount of HF 
reduces the concentration product of HCC-1120 and HF and acts as a heat 
remover and, therefore, the control of the reaction heat becomes easy. In 
the first reactor, the amount of 1,1-dichloro-2,2-difluoroethylene 
(CFC-1122) is also reduced (CFC-1122+HF.fwdarw.HCFC-133a). 
Since the reaction (HCC-30+2HF.fwdarw.HFC-32+2HCl) in the first reactor can 
proceed in the presence of excess HF, the good conversion can be obtained. 
In this reaction, while the amount of HF may be stoichiometrically two 
equivalents, an excess amount of HF can give higher conversion. In a 
system where a single reaction (the conversion from HCC-30) is conducted, 
there is a limitation of using the excess amount of HF in view of the cost 
of the apparatus. In a system which also include a reaction from HCC-1120, 
the stoichiometrically excess amount of HF is required in the second 
reactor, and the amount of HF can be easily set to an excess amount so as 
to supply the reaction mixture from the second reactor to the first 
reactor. This is advantageous for simultaneous production. 
The reaction temperature of the first reactor is usually from 180.degree. 
to 320.degree. C., preferably from 200.degree. to 300.degree. C., more 
preferably from 230.degree. to 270.degree. C. When it is lower than 
180.degree. C., the conversion of HCC-1120 is lowered. When it is higher 
than 320.degree. C., the catalyst is remarkably deteriorated and an amount 
of HFC-134a decreases. The contact time is usually from 0.5 to 60 seconds, 
preferably from 2 to 10 seconds. The reaction pressure is not specifically 
limited unless the raw material and product are liquefied. The reaction 
pressure is usually from 1 to 20 atm, preferably from 1 to 10 atm, in view 
of simplification, economy, etc. In the first reactor, a fluorinating 
catalyst is usually used, but its type and production method are not 
specifically limited. Examples of the fluorinating catalyst include 
fluorinated chromium oxide obtained by fluorinating a heat-treated hydrate 
of chromium (III) hydroxide with hydrogen fluoride; chromium (III) 
trifluoride; fluorinated aluminum oxide obtained by fluorinating aluminum 
oxide with hydrogen fluoride; catalyst obtained by supporting at least one 
element selected from Ti, V, Zr, Mo, Ge, Sn and Pb on alumina, fluorinated 
alumina or partially fluorinated alumina; etc. 
The raw material supplied to the first reactor may be HCC-1120, HCC-30 and 
HF, and contains HFC-134a. It may also contain compounds such as hydrogen 
chloride (HCl), HCFC-133a, 1,1-dichloro-2,2-difluoroethylene (CFC-1122), 
etc. 
In the raw material supplied to the first reactor, a molar ratio of 
HCC-1120 to HCC-30 is not specifically limited, but is usually from 10:1 
to 1:2, preferably from 5:1 to 1:1. In the first reactor, the amount in 
mole of HF is usually from 1 to 50 times, preferably from 2 to 20 times, 
based on the total value of a 3-fold value of the mole amount of 
1,1,2-trichloroethylene and 2-fold value of mole amount of methylene 
chloride. The amount of HFC-134a is usually from 0.2 to 5 mol (e.g. about 
equimol) per 1 mol of HCC-1120. 
In the second reactor, 1,1,1-trifluorochloroethane (HCFC-133a) is reacted 
with hydrogen fluoride in a vapor phase at a reaction temperature of 
280.degree. to 400.degree. C., which is higher than the reaction 
temperature of the first reactor, in the presence of a fluorinating 
catalyst to produce 1,1,1,2-tetrafluoroethane (HFC-134a). The reaction 
temperature is usually from 280.degree. to 400.degree. C., preferably from 
290.degree. to 350.degree. C. When the temperature is lower than 
280.degree. C., the amount of the generated HFC-134a is lowered. When the 
temperature is higher than 400.degree. C., the deterfiFaion of the 
catalyst is remarkable. The temperature of the first reactor is set at a 
temperature lower than that of the second reactor. For example, a 
difference between the temperatures of the first and second reactors is 
from 30.degree. to 120.degree. C. The reaction pressure is usually from 1 
to 20 atm, preferably from 1 to 10 atm. The contact time is usually from 
0.5 to 60 seconds, preferably from 2 to 10 seconds. Examples of the 
fluorinating catalyst are the same as those described in the first 
reactor. The amount of hydrogen fluoride is usually from 0.9 to 15 mol, 
preferably from 3 to 6 mol, based on 1 mol of HCFC-133a. The raw material 
supplied to the second reactor contains HCFC-133a and HF, and it may 
contain trichloroethylene, HCFC-132b (CF.sub.2 ClCHCl.sub.2), HCFC-124 
(CF.sub.3 CFHCl), etc. 
In the third reactor, the reaction mixture obtained from the first reactor 
is reacted with hydrogen fluoride in a vapor phase at 150.degree. to 
240.degree. C., which is lower than the reaction temperature of the first 
reactor, in the presence of a fluorinating catalyst. In the third reactor, 
the unreacted HCC-30 existing in the first reactor is converted into 
HFC-32 so that the amount of HCC-30 is reduced. Furthermore, the residual 
CFC-1122 is converted into HCFC-133a so that the amount of CFC-1122 is 
reduced. HCC-30 may be introduced into the third reactor without 
introducing into the first reactor, because it is possible to set the 
reaction condition which is more suitable for the fluorinating reaction of 
HCC-30 in the third reactor. The reaction temperature of the third reactor 
is lower by usually from 30.degree. to 170.degree. C., preferably from 
50.degree. to 120.degree. C. than the reaction temperature of the first 
reactor. The reaction pressure is usually from 1 to 20 atm, preferably 
from 1 to 10 atm. The contact time is usually from 0.5 to 60 seconds, 
preferably from 2 to 10 seconds. Examples of the fluorinating catalyst are 
the same as those described in the first reactor. When the reaction 
temperature is lower than 150.degree. C., a size of the third reactor 
becomes large. On the other hand, when the reaction temperature is higher 
than 240.degree. C., CFC-1122 does not react sufficiently. 
In a fourth reaction zone having at least one fourth reactor, the reaction 
mixture obtained from the third reactor is reacted with hydrogen fluoride 
in a vapor phase at 100.degree. to 190.degree. C., which is lower than the 
reaction temperature of the third reactor. The reaction temperature of the 
fourth reactor is lower by usually from 20.degree. to 140.degree. C., 
preferably from 40.degree. to 70.degree. C., than that of the third 
reactor. The reaction pressure is usually from 1 to 20 atm, preferably 
from 1 to 10 atm. The contact time is usually from 0.5 to 60 seconds, 
preferably from 2 to 10 seconds. When a plurality of fourth reactors exist 
in the fourth reaction zone, they are connected in a series, and a 
temperature of a last reactor in this zone which is far from the first 
reactor is lower than that of a leading reactor in this zone which is near 
the first reactor. Examples of the fluorinating catalyst are the same as 
those described in the first reactor. In the fourth reactor, the residual 
CFC-1122 is converted into HCFC-133a so that the amount of CFC-1122 is 
reduced. A total volume of the reactor which is required for the reaction 
of removing CFC-1122 can be reduced by separating into two zones, i.e. 
third and fourth reactors, in comparison with the case of one zone. 
In the fifth reactor, the reaction mixture containing HCFC-133a is reacted 
with hydrogen fluoride in a vapor phase at a temperature of 170.degree. to 
320.degree. C. The reaction temperature of the fifth reactor is usually 
from 180.degree. to 300.degree. C., preferably from 190.degree. to 
280.degree. C. The reaction pressure is usually from 1 to 20 atm, 
preferably from 1 to 10 atm. The contact time is usually from 0.1 to 30 
seconds, pfetefaly from 0.5 to 5 seconds. Examples of the fluorinating 
catalyst are the same as those described in the first reactor. The 
presence of HCC-30 and HCC-1120 can give a significant influence on the 
catalytic life in the second reactor and, therefore, the amount of HCC-30 
and HCC-1120 can be decreased in the fifth reactor. Thereby, the catalytic 
life in the second reactor becomes longer. 
In the first to fifth reactors, as a contact system between the catalyst 
and the raw material, both fluidized and fixed bed types can be used. In 
addition, a reactor having an insulating type or multi-tube type heating 
system can be used. In the first reactor, a fixed bed multi-tube type 
reactor is preferable. The raw material supplied to the first to fifth 
reactors is preferably introduced into the reactor after previously 
converting into a gas using an evaporator and the like. 
In the method of the present invention, the raw material supplied from the 
exterior may be HCC-30, HCC-1120 and HF. The supply position of HCC-30 and 
HCC-1120 supplied from the exterior is not specifically limited. It is 
preferred to mix the raw material with the reaction mixture fed from the 
second reactor to the first reactor, or the reaction mixture fed from the 
first reactor to the third reactor when supplying to the third reactor, 
because It is effective for the reaction to supply the raw material to the 
reactor in a state in which the raw material is sufficiently preheated and 
mixed. As the premixing method, for example, there is a spray-mixing 
method comprising spraying a cold liquid and mixing it with a heat gas. 
The supply position of HF supplied from the exterior is not specifically 
limited, but HF may be supplied in a step of recycling HCFC-133a and HF 
after removing HFC-32 and HFC-134a. It may also be supplied in several 
positions, e.g. before the first reactor. 
The reaction mixture obtained from the first, third or fourth reactor 
contains HFC-32, HFC-134a and HCl, and further contain HF, HCFC-133a, 
HCC-1120, HCC-30, CFC-1122, CH.sub.2 FCl (HCFC-31), CF.sub.2 ClCH.sub.2 Cl 
(HCFC-132b), etc. It is preferred to remove products (e.g. HFC-32, 
HFC-134a, HCl, etc.) from the system before feeding to the fifth reactor. 
The reason why HCl is removed before feeding to the fifth reactor is that 
the fluorination of HCFC-133a in the fifth and second reactors is 
prevented by the presence of HCl. These gases can be separated and removed 
as an liquefied component by the cooling or the cooling under pressure. 
Since HFC-32, HFC-134a and HCl are contained in the recovered substance 
wherein the product is removed, these are fed to a fractional distillation 
column and separated into the above product, the unreacted product and the 
intermediate raw material. In this case, a separation using a two phase 
separation may be conducted. 
The remainder of the reaction mixture wherein HFC-32, HFC-134a and HCl are 
removed is optionally separated into a phase which is rich in HCFC-133a 
and HF and a phase which is rich in HCC-30 and HF by a fractional 
distillation. It is preferred that the phase which is rich in HCFC-133a 
and HF is fed to the second reactor and the phase which is rich in HCC-30 
and HF is fed to the first reactor so that they are reused. 
PREFERRED EMBODIMENT OF THE INVENTION 
The following Examples further illustrate the present invention. 
COMATIVE EXAMPLE 1 
The reaction was conducted using a reaction tube (A) (made of Hastelloy C) 
having a double-tube type heating device and an inner diameter of 25 mm, 
which was packed with 1500 g of a fluorinating catalyst (chromium 
oxyfluoride), and a reaction tube (B) packed with 1500 g of a fluorinating 
catalyst (chromium oxyfluoride). 
1,1,1-Trifluorochloroethane (HCFC-133a) and HF in a flow rate (gas flow 
rate in a standard state, the same in the following) of 28 L/min and 112 
L/min, respectively, were introduced into the reaction tube (A) heated to 
320.degree. C. and the reaction was conducted to generate 
1,1,1,2-tetrafluoroethane (HFC-134a). To the resultant gas, 
1,1,2-trichloroethylene (HCC-1120) was added in a flow rate of 4.48 L/min 
and the reaction was conducted at 240.degree. C. in the reaction tube (B) 
(made of Hastelloy C) having a double-tube type heating device and an 
inner diameter of 25 mm, which is packed with 1500 g of a fluorinating 
catalyst. 
The gas evolved from the reaction tube (B) was subjected to GC analysis 
after deacidificaton. As a result, the efflux rate of HFC-134a was 4.40 
L/min, and the conversion of HCC-1120 was 99.2%. 
A heat spot at 255.degree. C. was formed at the position which is about 30 
cm away from the inlet of an catalyst layer in the reaction tube (B). 
Example 1 
The same manner as in Comparative Example 1 was repeated except that 
1,1,2-trichloroethylene (HCC-1120) was mixed with methylene chloride 
(HCC-30) having a flow rate of 2.24 L/min and the mixture was introduced 
into the reaction tube (B). 
As a result of the GC analysis, the conversion of HCC-1120 was 98.9% and 
the efflux rate of HFC-134a was 4.37 L/min. It has been found that the 
conversion of HCC-1120 and efflux rate of HFC-134a are almost the same as 
those of Comparative Example 1. 
Simultaneously HFC-32 was formed from HCC-30. As a result of the reaction, 
the conversion of HCC-30 was 92.0% and the selectivity of HFC-32 was 
94.4%. 
EXAMPLE 2 
The same manner as in Example 1 was repeated except that the gas generated 
in the reaction tube (B) was introduced into the reaction tube (C), which 
was packed with 1500 g of a fluorinating catalyst (chromium oxyfluoride) 
and previously heated to 170.degree. C. 
As a result of the reaction at the outlet of the reactor (C), the 
conversion of HCC-30 was 92.1% and the selectivity of HFC-32 was 94.4%, 
based on the amount of HCC-30 introduced into the reaction tube (B). 
At the outlet of the reaction tube (B), CFC-1122 existed in an amount of 
about 500 ppm based on HFC-134a, but the amount thereof was deceased to 15 
ppm at the outlet of the reaction tube (C). 
Comparative Example 2 
The same manner as in Comparative Example 1 was repeated except that the 
reaction was conducted by adding 1,1,2-trichloroethylene and methylene 
chloride in a flow rate of 0.1 L/min and 0.2 L/min, respectively, to an 
inlet gas of the reaction tube (A). 
The efflux rate of HFC-134a from the reaction tube (A) was 4.46 L/min at 
the beginning of the reaction, but was gradually decreased to 3.35 L/min 
after 300 hours. 
EXAMPLE 3 
The same manner as in Comparative Example 2 was repeated except that, after 
eaeting the above gas In the reaton tube (C) heated previously to 
300.degree. C. in which 300 g of a fluorinating catalyst was charged, the 
reaction gas was further introduced into the reaction tubes (A) and (B) 
and then reacted. 
The gas evolved from the reaction tube (A) was subjected to GC analysis 
after deacidification. As a result, the efflux rate of HFC-134a from the 
reaction tube (A) was 4.50 L/min at the beginning of the reaction, and was 
4.08 L/min even after 300 hours. 
At this time, methylene chloride was hardly detected at the outlet of the 
reaction tube (C). 
EFFECT OF THE INVENTION 
The effects of the present invention are as follows. 
HCl is generated in the first reactor, and it is supposed that the 
generated HCl gives a deleterious influence on HFC-134a. In the present 
invention, however, the practical conversion from HFC-134a into HCFC-133a 
is smaller than an expected value derived from a relationship of the 
equilibrium constant and the concentration of the raw material and the 
generated system. Accordingly, it is possible to produce HCFC-133a and 
HFC-32 efficiently without causing disadvantageous conversion from 
HFC-134a into HCFC-133a. The efficiency of energy is good and the 
formation of a heat spot in the reactor is inhibited. 
In the present invention, HCFC-134a and HFC-32 can be produced efficiently. 
When HFC-134a is used as a diluting agent and excess HF is supplied, HF 
acts as a heat remover and, therefore, the control of the reaction heat 
becomes easier and more efficient. In the first reactor, the amount of 
1,1-dichloro-2,2-difluoroethylene (CFC-1122) is also reduced. 
It as possible to proceed the reaction in the first reactor in the presence 
of excess HF without causing a problem on the cost of the apparatus and, 
therefore, the reaction (HCC-30+2HF.fwdarw.HFC-32+2HCl) proceeds in good 
conversion. 
According to the present invention, it is possible to give HFC-32 and 
HFC-134a in good yield without causing a deleterious Influence such as the 
decrease in conversion of HCC-1120, the decease in amount of HFC-134a, 
etc.