Process for the preparation of 1,1-dichloro-1-fluoroethane

The invention relates to a thermal process the production of 1,1-dichloro-1-fluoroethane by hydrofluorination of vinylidene chloride carried out in the absence of any catalyst.

The present invention relates to a process for the production of 
1,1-dichloro-1-fluoroethane from 1,1-dichloroethylene, also called 
vinylidene chloride (VC.sub.2), by reaction with hydrogen fluoride in 
liquid medium in the absence of catalyst(s) and at elevated temperature. 
1,1-dichloro-1-fluoroethane is a synthetic product carrying in its 
molecule, apart from chlorine, fluorine and carbon atoms, hydrogen atoms. 
The boiling point of this compound is 32.degree. C. under atmospheric 
pressure. It can be used by itself especially as a blowing agent or in a 
mixture with other chlorofluorinated hydrogen-containing or hydrogen-free 
compounds. 
The known industrial processes for obtaining 1,1-dichloro-1-fluoroethane 
all start with 1,1,1-trichloroethane, even though it has been known for a 
time that this product can be obtained by hydrotiuorination of vinylidene 
chloride. 
Thus, Journal of Am. Chem. Soc. 1943, 65, p. 1272 already describes that 
the reaction of 1 mol of vinylidone chloride with 4 mol of hydrogen 
fluoride carried out at 65.degree. C. for 3 hours makes it possible 
especially obtain 50% of 1,1-dichloro-1-fluoroethane, 5% of 
1,1,1-trichloroethane and 15% of tars. 
Furthermore, British Patent 627,773 discloses especially the reaction of 8 
mol of vinylidene chloride with about 8.7 mol of hydrogen fluoride in the 
presence of tin chloride at temperatures between 10.degree. C. and 
35.degree. C. for 1 hour 45 minutes, as a result of which 
1,1-dichloro-1-fluoroethane is obtained at a conversion rate of 32.7%, 
calculated with respect to the vinylidene chloride used. 
However, yields and purities of this kind were not high enough for 
justifying industrial exploitation, or even a continuation of the studies 
of the production of 1,1-dichloro-1-fluoroethane by hydrofluorination 
vinylidene chloride, and consequently this route was abandoned in favour 
of the one starting with 1,1,1-trichloroethane, which apparently did not 
have the same disadvantages. 
The applicant has now found a process for producing 
1,1-dichloro-1-fluoroethane by hydrofluorination of vinylidene chloride 
which no longer has the drawbacks of the abovementioned processes. 
Accordingly, the present invention relates to a process for the production 
of 1,1-dichloro-1-fluoroetnane by reaction of hydrogen fluoride with 
vinylidene chloride, in which the reaction is carried out in a liquid 
medium at a temperature above 70.degree. C. and in the absence of a 
catalyst. 
The hydrogen fluoride necessarily has to be used in the present process in 
anhydrous form and in a purity of greater than 95% and preferably greater 
than 99% by volume. It can be introduced into the reactor in gaseous or 
liquid form. 
The vinylidene chloride used must fulfil the same specifications as those 
described above for hydrogen fluoride, i.e. it has to be anhydrous and 
pure. 
The amounts of hydrogen fluoride and vinylidene chloride, respectively, 
which are introduced into the reactor, are without any great importance by 
themselves. In contrast, it is absolutely necessary that the molar ratio 
in which these two reactants are introduced into the reactor is between 
1.5 to 3 mol of HF per 1 mol of vinylidene chloride, if the advantageous 
results provided by the process of the invention are to be observed. 
The reaction mixture in the inside of the hydrofluorination reactor must be 
maintained in the liquid state for a favourable course of the process of 
the invention. This can be done by using any known method. A practical 
method which has given good results consists in operating in a reactor 
which is maintained under pressure. 
The reaction temperature is in general between 75.degree. C. and 
130.degree. C. and preferably between 80.degree. C. and 125.degree. C. 
Under these conditions, the pressure in the reactor is in general between 
2 and 30 bar and preferably between 5 and 25 bar. 
The selectivity of 1,1-dichloro-1-fluoroethane obtained in the process of 
the invention is very high and reaches, under operating conditions of 
100.degree. C. and for an initial VC.sub.2 /HF molar ratio of 1/2, as much 
as 85% when the conversion rate of VC.sub.2 is as high as 98.7%. 
When operating according to the process of the invention, the amount of 
oligomers and tars formed, which are an obstacle to industrial 
exploitation of the earlier known processes, is very low and can compete 
with that observed with the processes carried out starting with 
1,1,1-trichloroethane. 
Thus, when the reaction is carried out at temperatures above 70.degree. C., 
the total amount of oifgomers observed is less than 5 mol % of the total 
amount of vinylidene chloride used. It is even possible, by varying the 
reaction parameters, to obtain amounts of oligomers which are less than 1 
mol %, and indeed 0.2 mol %, of the amount of vinylidene chloride used. 
Although the process of the invention is carried out in the absence of any 
catalyst in a purely thermal manner with amounts of reactants and reaction 
products, such as detailed above, it is obvious that any variant in which 
a thermal process is used but in which excess reactants, such as 
vinylidene chloride, hydrogen fluoride, or excess products originating 
from the reaction, such as hydrogen chloride or 
1,[-difluoro-1-chloroethane, are introduced temporarily or continuously in 
higher or lower amounts than those specified above, are likewise part of 
the present invention. 
The reactors used in the process according to the invention can be made of 
different materials, such as steel, stainless steel or also different 
alloys, such as MONEL, INCONEL and HASTELLOY. It is likewise possible to 
use reactors in which the inside wall is lined with an inert lining, such 
as a resin layer which is inert under the reaction conditions, such as, 
for example, fluorinated resins. 
The reactors are advantageously equipped with technical devices by means of 
which the contact between the reactants can be improved. Thus, the 
reactors can be provided with stirrers, or devices for introducing the 
reactants can also be provided, thus achieving efficient dispersion of the 
reactants inside the reaction mixture. 
The means of introduction as well as the flow rates of the reactants at the 
entry of the reactors are regulated in such a manner that the desired 
proportions of the reactants are maintained inside the liquid reaction 
medium. Consequently, they are a function especially of the temperature, 
the filling level of the reactors, the residence time and the discharge 
rates applied. 
Under the conditions described above, the reaction can be operated 
batchwise or continuously. If it is operated batchwise, the reaction is 
usually carried out in stirred and sealed autoclaves, and when it is 
operated continuously, it is preferably carried out in reactors of the 
mixer type equipped with systems for the continuous introduction of 
reactants and discharge of products. 
No matter what the operating procedure of the reaction, batchwise or 
continuously, of the process of the invention, it is essential that the 
discharge means be regulated in such a way that all the hydrogen chloride 
produced by the process of the invention is substantially removed in 
gaseous phase, while the other products originating from the reaction or 
residual products whose boiling temperature is above that of hydrogen 
chloride are discharged in liquid phase. 
If desired, one of the reactants or both can be introduced at a single or 
at several points spaced around the reactors. Thus, especially several 
points equipped with means for the introduction of vinylidene chloride 
into the reactors can be provided, while observing however the molar 
ratios of the reactants introduced. 
The reaction can be carried out in a single reactor or in several reactors 
connected in series. In this case, it is likewise possible to provide 
various means for the introduction of the reactants. The two reactants can 
be introduced into the same reactor or the introduction of one of the 
reactants can be divided between each of the reactors. It is likewise 
possible to use several reactors which are fed with each of the reactants, 
respectively, where the mixtures formed in each of the reactors are 
circulated in the same direction or in countercurrent. 
The method of gas-phase removal of the hydrogen chloride formed by the 
reaction can be effected by any means known for this purpose. A means 
which has given good results consists in equipping the reactor with a 
reflux column. Depending on the efficiency of the reflux applied, the 
hydrogen chloride additionally contains light organic compounds as 
byproducts which can, if desired, be removed by conventional means, such 
as fractional distillation. 
The reactors are also advantageously equipped with means for recovering 
part of the liquid phase. In order to favour the liquid-phase recovery, 
the reaction is preferably carried out with a reaction medium maintained 
under a pressure of about 10 to 20 bar. 
Finally, the liquid mixture originating from the reactor can then be 
subjected to separation operations in one or more steps for recovering 
1,1-dichloro-1-fluoroethane. 
Some of the by-products and impurities can be easily eliminated by 
distillation. This is for instance the case for 
1-chloro-1,1-difluoroethane and 1,1,1-trifluoroethane, as well as for the 
oligomers formed during the reaction. However, the 
1,1-dichloro-1-fluoroethane usually contains impurities such as small 
quantities of undesired unsaturated chlorinated or chlorofluorinated 
compounds which can be difficultly separated by distillation, because 
their boiling points are close to the one of 1,1-dichloro-1-fluoroethane. 
Indeed, in addition to the unreacted vinylidene chloride, the main 
unsaturated impurities which may be present in the 
1,1-dichloro-1-fluoroethane to be purified are dichloroacetylene, 
1,2-dichloro-1-fluoroethylenes (cis and trans isomers), trans 
1,2-dichloroethylene traces of 1-chloro-1-fluoroethylene. 
The unsaturated chlorinated compounds such as vinylidene chloride, which 
may still be present in the reaction medium, can be removed by any 
chemical or physical method known for this. In the particular case 
vinylidene chloride, the methods which have given good results consist in 
bromination or chlorination of this compound, followed by separation of 
the saturated compounds obtained by distillation. 
If it is desired to recover the 1,1-dichloro-1-fluoroethane with a purity 
of greater than 99% volume, a procedure which has given good results 
consists in: 
first subjecting the organic liquid phase originating from the 
hydrofluorination reactor and previously separated from the liquid phase 
containing the inorganics, i.e. substantially hydrogen fluoride, to 
distillation so as to remove, in gaseous phase, the products whose boiling 
point is below that of 1,1-dichloro-1-fluoroethane, i.e. substantially in 
order to eliminate traces of 1-chloro-1,1-difluoroethane and 
1,1,1-trifluoroethane, 
subjecting the liquid phase originating from the preceding distillation to 
a chlorination operation so as to chlorinate the unsaturated products, 
such as vinylidene chloride remaining in the medium and finally, 
removing the chlorinated products formed in the previous step by 
distillation. 
However, if it is easy to eliminate the vinylidene chloride and the 
dichloroacetylene by any suitable method, this is not necessarily the case 
the unsaturated chlorinated compounds and more particularly for the cis 
and trans 1,2-dichloro-1-fluoroethylenes which are significantly less 
reactive. When the chlorination treatment is effected under more severe 
conditions to also chlorinate these less reactive unsaturated chlorinated 
compounds, a rather important amount 1,1-dichloro-1-fluoroethane may also 
react, inducing the formation of 1,1,2-trichloro-1-fluoroethane. This loss 
of output in 1,1-dichloro-1-fluoroethane has been noticed in all the tests 
effected under more drastic conditions, even by photochemical chlorination 
as in the presence of a Lewis acid. 
Furthermore, the elimination of the cis and trans 
1,2-dichloro-1-fluoroethylenes appears to be more difficult as it has been 
observed that, in some cases, after passing through a minimum, their 
concentration grows if the chlorination treatment is extended. 
A possible explanation for this phenomenon would be their formation by 
dehydrochlorination of 1,2,2-trichloro-1-fluoroethane produced at the 
expense of the 1,1-dichloro-1-fluoroethane. The Applicant however does not 
intend to be bound by this explanation. 
On the other hand, it has been further observed that the 
1,1-dichloro-1-fluoroethane may undergo an important degradation 
downstream of the chlorination stage of the unsaturated impurities, namely 
in the following distillation stages, when the chlorination is effected in 
the presence of equal or greater amounts about 10 ppm of Lewis acids or 
when there remains, after the chlorination reactor, equal or greater 
amounts about 10 ppm of Lewis acids and especially FeCl.sub.3. The 
chlorination reactor, as well as all the equipment downstream, are 
therefore preferably realized with corrosion resistant materials, such as 
MONEL, INCONEL and HASTELLOY, which are not likely to introduce in the 
medium between the chlorination stage and the end of the purification 
amounts of FeCl.sub.3 greater than or equal to 10 ppm. 
In a preferred embodiment of the process according to the invention, these 
disadvantages may be obviated while enabling the almost complete 
transformation of all the unsaturated chlorinated or chlorofluorinated 
impurities, by chlorinating these impurities in order to obtain products 
having boiling points which are sufficiently different from the boiling 
point of 1,1-dichloro-1-fluoroethane so as to be easily separated 
afterwards by distillation. 
In order to do this, the chlorination may be effected by reacting the 
liquid medium to be treated with an excess of chlorine, in the presence of 
very small amounts of a Lewis acid and preferably FeCl.sub.3, at a 
temperature, adjusted in function of the amount of FeCl.sub.3, 
sufficiently high to enable the almost complete elimination of the 
impurities in a reasonable lapse of time, not exceeding a few hours, but 
sufficiently low to avoid the chlorination of a part of the 
1,1-dichloro-1-fluoroethane. 
In a most preferred embodiment, before the chlorination stage, the 
1,1-dichloro-1-fluoroethane is freed from products having a boiling point 
higher than that of the 1,1-dichloro-1-fluoroethane, i.e. essentially the 
oligomers and tars. This separation may be effected by conventional 
distillation. 
The amount of FeCl.sub.3 used in the chlorination of this preferred 
embodiment of the invention, is necessarily lower than 10 ppm. Preferably, 
this amount is lower than or equal to about 6 ppm. Although FeCl.sub.3 is 
used in small amounts, its presence is however absolutely required to 
effect the chlorination of all the unsaturated impurities. The minimal 
amount of FeCl.sub.3 enabling a chlorination of the unsaturated impurities 
in a reasonable time is about 0,05 ppm. Preferably the amount of 
FeCl.sub.3 is greater than or equal to 1 ppm. Most preferrably, it is 
about 3 ppm. 
Owing to the low amounts of FeCl.sub.3 used, the process of the invention 
has in addition the advantage to avoid a tedious and delicate stage of 
elimination of FeCl.sub.3 from the medium by alcaline washing or by 
complexation, previously to any further treatment, stage which is 
absolutely necessary to avoid altering the purity of the 
1,1-dichloro-1-fluoroethane when the chlorination effected in the presence 
of more important amounts FeCl.sub.3. 
In practice, the FeCl.sub.3 may be introduced in the chlorinator by 
different means. A means which has given good results consists in 
saturating a fraction of the flow of 1,1-dichloro-1-fluoroethane to be 
purified by FeCl.sub.3. By way of example, the solubility of FeCl.sub.3 in 
1,1-dichloro-1-fluoroethane at room temperature is about 7 ppm. Other 
solvents, capable of dissolving a sufficient amount of FeCl.sub.3, which 
are inert in the chlorination conditions and easily recovered in a further 
separation stage, may also be used as far as it is understood that they 
are used in such amounts that the total amount of FeCl.sub.3 present in 
the reaction medium is not in excess of the values cited herebefore. 
Solvents corresponding to these criteria are for instance 
tetrachloromethane, tri-chloromethane and 1,2-dichloroethane. 
With the amounts of FeCl.sub.3 defined hereabove in the medium, a 
temperature of about 75.degree. C. already enables to effect the 
chlorination of the unsaturated impurities at a sufficient rate so as to 
enable an industrial application. A suitable chlorination rate is obtained 
when the temperature is greater than or equal to about 80.degree. C. 
However, at temperatures greater than about 120 .degree. C., the 
transformation of 1,1-dichloro-1-fluoroethane 
1,1,2-trichloro-1-fluoroethane reaches important amounts of Preferably, 
the chlorination is effected at a temperature lower than or equal to about 
110.degree. C. 
Chlorine is introduced in an amount in excess with respect to the 
impurities to be chlorinated. The molar ratio between the chlorine and the 
sum of the unsaturated impurities to be chlorinated may be varied within 
large ratios. A ratio greater than or equal to about 10 enables to reach 
an acceptable reaction rate; this ratio may also be much larger without 
therefore cause the degradation of 1,1-dichloro-1-fluoroethane. This ratio 
in general does not exceed 100. 
The chlorination may be effected at atmospheric pressure or at higher 
pressures. This pressure mall be either the autogeneous pressure, or a 
nigher pressure, induced by the introduction of an inert gas, e.g. 
nitrogen. Usually, the chlorination treatment is effected at a pressure of 
about 4 bar to about 15 bar. 
Under the conditions defined above, an almost complete chlorination of the 
unsaturated chlorinated and chlorofluorinated compounds is obtained with a 
treatment time of 1,1-dichloro-1-fluoroethane to be purified in the 
chlorinator varying from a few minutes to about 2 hours. On an industrial 
basis, the residence time of the 1,1-dichloro-1-fluoroethane in the 
chlorinator is of course adjusted in function of the required purity. 
Classically, a satisfactory purity is obtained with a residence time of 10 
to 60 minutes.

Examples 1 to 4 are given to illustrate the invention. Example 5 is given 
as a comparison. 
EXAMPLE 1 
Vinylidene chloride is first introduced with stirring into a cylindrical 
stainless steel 316 reactor (autoclave) of 0.5 litre which is equipped 
with a stirrer, cooled to -30.degree. C. and put under a vacuum 15 mbar, 
and allowed to adopt the temperature of the reactor for a few minutes so 
as to obtain a drop in pressure in the autoclave. 
Hydrogen fluoride which is maintained at ambient temperature in a stainless 
steel 316 cylinder is then introduced into the reactor by suction. 
The reactor is then immersed in a thermostat preheated to the desired 
temperature, and the pressure is regulated at a desired value, which is a 
function of the experimental temperature, in such a manner that only 
hydrogen chloride and the organic products which are lighter than 
1,1-dichloro-1-fluoroethane, i.e. substantially 
1-chloro-1,1-difluoroethane and possibly 1,1,1-trifluoroethane, are 
allowed to escape from the reactor. 
The moment at which the reactor is immersed in the preheated thermostat 
determines the beginning of the reaction. 
During the entire course of the reaction, the development of the pressure 
in the reactor is monitored while keeping the temperature constant. 
The gaseous effluent is collected and measured in a water meter after 
neutralisation and destruction of the discharged hydrochloric acid and 
hydrofluoric acid in a scrubber containing a dilute NaOH solution. 
After the desired reaction time, the reactor is finally abruptly cooled to 
0.degree. C. by means of a cooling bath, and the liquid and gaseous phases 
are removed from the reactor (via an NaOH gas-washing bottle connected to 
the gas meter) and analysed. 
Under the general conditions described above, three batchwise experiments 
were carried out at temperatures respectively of 75.degree. C. (experiment 
1), 100.degree. C. (experiment 2) and 125.degree. C. (experiment 3), the 
parameters and results of which are listed below. 
______________________________________ 
Experiment 1 
Temperature of the experiment 
75.degree. C. 
HF/VC.sub.2 molar ratio used 
2 mol/mol 
Amount of VC.sub.2 used 250 g 
Amount of HF used 103 g 
*Results in mol % after 5 h of reaction: 
Conversion rate of VC.sub.2 
98.7% 
Selectivity of 1,1-dichloro-1-fluoroethane 
88% 
Byproducts: 
1-chloro-1,1-difluoroethane 
4% 
1,1,1-trifluoroethane 3.3% 
total oligomers 4.7% 
(expressed as 
converted VC.sub.2) 
Experiment 2 
Temperature of the experiment 
100.degree. C. 
HF/VC.sub.2 molar ratio used 
2 mol/mol 
Amount of VC.sub.2 used 250 g 
Amount of HF used 103 g 
*Results in mol % after 2 h 30 min of reaction: 
Conversion rate of VC.sub.2 
98.7% 
Selectivity of 1,1-dichloro-1-fluoroethane 
83.5% 
Byproducts: 
1-chloro-1,1-difluoroethane 
10% 
1,1,1-trifluoroethane 3% 
total oligomers 2.5% 
(expressed as 
converted VC.sub.2) 
Experiment 3 
Temperature of the experiment 
125.degree. C. 
HF/VC.sub.2 molar ratio used 
2 mol/mol 
Amount of VC.sub.2 used 250 g 
Amount of HF used 103 g 
*Results in mol % after 3 h 30 min of reaction: 
Conversion rate of VC.sub.2 
99.3% 
Selectivity of 1,1-dichloro-1-fluoroethane 
78% 
Byproducts: 
1-chloro-1,1-difluoroethane 
16% 
1,1,1-trifluoroethane 4% 
total oligomers 1% 
(expressed as 
converted VC.sub.2) 
______________________________________ 
* = these results are obtained by GPC (gas phase chromatography) analysis 
by recovering all the organic compounds present in the gaseous phase and 
the liquid phase of the reactor. 
Thus, it can be seen from the batchwise results that hydrofluorination of 
VC.sub.2 at high temperature without catalyst(s) enables high conversion 
rates of VC.sub.2 to be obtained, which are close to 100% while the 
selectivities of 1,1-dichloro-1-fluoroethane observed are around 80%, or 
even 90%. 
EXAMPLE 2 
52 g/h of HF and 138 g/h of VC.sub.2, i.e. a HF/VC.sub.2 molar ratio of 1.7 
mol/mol at the reactor inlet, are introduced continuously into a stainless 
steel 316 stirred double-jacketed reactor of 200 cm.sup.3, which heated to 
120.degree. C. by circulation of oil and overflows into a discharge tube 
maintained at the same temperature the reactor. 
The pressure in this reactor is controlled at 18 bar so as to maintain the 
liquid reaction medium at 120.degree. C. 
After being kept in operation for 4 hours, samples of the gaseous phase and 
the liquid phase overflowing from the autoclave are taken. 
After letdown to atmospheric pressure, the effluent is neutralised in a 
scrubber containing dilute caustic lye (1/10 molar), and the gases then 
pass into a wet meter via a sampling system composed of two pyrex ampoules 
of 100 cm.sup.3, for measuring the throughput. traction of the aqueous 
phase from the scrubber with carbon tetrachloride is also carried out in 
order to obtain complete analysis of all the organic compounds present and 
formed in the reactor. 
The organic products are then analysed as Example 1 by gas-phase 
chromatography, the unconsumed HF is measured by ionometry by means of a 
specific electrode sensitive to F.sup.- ions, and the HCl formed is 
measured by potentiometry using silver nitrate. 
The operating conditions and results obtained under these conditions are 
listed in the table below. 
TABLE 
______________________________________ 
Temperature .degree.C. 
120 
Pressure bar 18 
Residence time hours 1 
Stirrer speed rpm 400 
HF throughput g/h 52 
VC.sub.2 throughput 
g/h 138 
HF/VC.sub.2 ratio mol/mol 1.7 
Conversion rate of VC.sub.2 
% 94.1 
Selectivities of: 
1,1-dichloro-1-fluoroethane 
% 91.2 
1-chloro-1,1-difluoroethane 
% 6.3 
1,1,1-trifluoroethane 
% 0.6 
1,1,1-trichloroethane 
% 1.6 
total oligomers % 0.2 
(expressed as 
converted VC.sub.2) 
______________________________________ 
From the results of this Example 2 in which the hydrofluorination reaction 
of VC.sub.2 is conducted continuously it can be deduced that the yields 
and selectivities can still be improved compared with the excellent 
results already observed in Example 1, where experiments carried out in a 
batchwise procedure are reproduced. 
EXAMPLE 3 
The organic phase of a preparation unit of 1,1-dichloro-1-fluoroethane (97 
% by weight of 1,1-di-chloro-1-fluoroethane), freed by distillation from 
the by-products which are more volatile and heavier than the 
1,1-dichloro-1-fluoroethane, is introduced in a reactor made of MONEL 
operating continuously. Simultaneously, FeCl.sub.3 is introduced in the 
reactor in such a ratio that in the chlorinator, the organic phase 
contains 0.6 ppm of FeCl.sub.3 and 80 g of chlorine per liter of organic 
phase. The chlorination reactor is maintained at a temperature of 100 
.degree. C..+-.3.degree. C. The pressure is adjusted at 9 bar by means of 
nitrogen. The residence time of the organic phase in the reactor is 1 
hour. Table II shows the initial and final contents of unsaturated 
chlorinated and chlorofluorinated compounds. 
TABLE II 
______________________________________ 
Contents at the 
Contents at the 
inlet of the 
outlet of the 
chlorinator (ppm) 
chlorinator (ppm) 
______________________________________ 
vinylidene chloride 
593 &lt;5 
dichloroacetylene 
173 &lt;1 
1,2-dichloro- 77 8 
fluoroethylene(cis) 
1,2-dichloro- 41 &lt;5 
fluoroethylene (trans) 
1,2-dichloro- 392 &lt;5 
ethylene (trans) 
1-chloro-1-fluoroethylene 
5 2 
______________________________________ 
EXAMPLE 4 
The organic phase of a preparation unit of 1,1-dichloro-1-fluoroethane (97% 
by weight of 1,1-dichloro-1-fluoroethane), freed by distillation from the 
by-products which are more volatile and heavier than the 
1,1-dichloro-1-fluoroethane, is introduced in a reactor made of MONEL 
operating continuously. In the reactor are also introduced FeCl.sub.3 in 
such a ratio that, in the chlorinator, the organic phase contains 3 ppm of 
FeCl.sub.3 and 80 g of chlorine per liter of organic phase. 
The chlorination reactor is maintained at a temperature of 80.degree. 
C..+-.3.degree. C. 
The pressure is adjusted at 9 bar by means of nitrogen. The residence time 
of the organic phase in the reactor is 45 minutes. Table III shows the 
initial and final contents of the main unsaturated chlorinated and 
chlorofluorinated compounds 
TABLE III 
______________________________________ 
Contents at the 
Contents at the 
inlet of the 
outlet of the 
chlorinator (ppm) 
chlorinator (ppm) 
______________________________________ 
vinylidene 431 &lt;5 
chloride 
dichloro- 17 &lt;1 
acetylene 
1,2-dichloro- 
38 &lt;5 
fluoroethylene(cis) 
1,2-dichloro- 
43 &lt;5 
fluoroethylene 
(trans) 
______________________________________ 
EXAMPLE 5 (COMISON) 
The organic phase of a preparation unit of 1,1-dichloro-1-fluoroethane (97% 
by weight of 1,1-dichloro-1-fluoroethane), freed by distillation from the 
by-products which are more volatile and heavier than the 
1,1-dichloro-1-fluoroethane, is introduced in a reactor made of MONEL 
operating continuously. In the reactor are also introduced FeCl.sub.3 in 
such a ratio that, in the chlorinator, the organic phase contains 40 ppm 
of FeCl.sub.3 and 80 g of chlorine per liter of organic phase. 
The chlorination reactor is maintained at a temperature of 80.degree. 
C..+-.3.degree. C. The pressure is adjusted at 9 bar by means of nitrogen. 
The residence time of the organic phase in the reactor is 45 minutes. 
Table IV shows the initial and final contents of the main unsaturated 
chlorinated and chlorofluorinated compounds. 
TABLE IV 
______________________________________ 
Contents at the 
Contents at the 
inlet of the 
outlet of the 
chlorinator (ppm) 
chlorinator (ppm) 
______________________________________ 
vinylidene 525 &lt;5 
chloride 
dichloro- 28 &lt;1 
acetylene 
1,2-dichloro- 
41 20 
fluoroethylene(cis) 
1,2-dichloro- 
12 10 
fluoroethylene 
(trans) 
______________________________________ 
The comparison of the results described in Tables III and IV enables to 
establish the extremely important influence of low amounts of FeCl.sub.3 
(Table III) on the elimination of impurities of the types cis and trans 
1,2-dichlorofluoroethylene and hence on the purity of the 
1,1-dichloro-1-fluoroethane finally obtained.