Method for producing dichloroethane

A method for producing dichloroethane (EDC) by reacting ethylene and chlorine in a liquid reaction medium composed mainly of EDC at a temperature of not less than the boiling point of EDC measured at ordinary pressure, characterized by leading the vapor of the reaction medium generated in a reactor from the top of the reactor to a heat exchanger so as to recover and utilize the latent heat resulting from condensation of the vapor in the heat exchanger. According to the present invention, high heat utilization efficiency can be attained with advantages as compared with conventional EDC production methods.

BACKGROUND OF THE INVENTION 
The present invention relates to a method of producing dichloroethane 
(ethylene dichloride) (hereinafter referred to as "EDC") by reacting 
ethylene and chlorine in a liquid phase at a temperature not lower than 
83.degree. C. More particularly, the invention relates to a method of 
producing EDC wherein the heat of reaction is recovered for efficient 
utilization. 
EDC is industrially important as a starting material in the production of 
vinyl chloride monomer. Since disclosure in U.S. Pat. No. 2,929,852, a 
method of reacting ethylene with chlorine at a temperature not lower than 
83.degree. C. by feeding the reactants into a liquid reaction medium 
composed mainly of EDC is known as the so-called high temperature method. 
The method is advantageous as compared with the low-temperature method in 
that the heat of reaction can be utilized more efficiently. In accordance 
with the method proposed in the above U.S. patent, a reaction-distillation 
scheme is adopted, namely the liquid reaction medium is vaporized by the 
heat of reaction and the vapor generated is introduced for purification 
into a distillation column connected with the upper part of the reactor, 
so that the heat of reaction can be efficiently utilized as a source of 
energy required for purification of EDC. 
In British Patent No. 1,231,127, it is proposed that the heat of reaction 
should be efficiently utilized by purifying, according to the above 
reaction-distillation technique, not only EDC produced by the above 
reaction but also EDC obtained from the oxychlorination step in a vinyl 
chloride monomer production plant and the unreacted EDC obtained from the 
cracking step. In U.S. Pat. No. 4,172,099, an improvement is proposed 
which comprises supplying the EDC from the oxychlorination step to the 
above-mentioned reaction-distillation step after washing, neutralization, 
dehydration, low-boiling fraction elimination and like steps and, for the 
EDC from the cracking step, supplying it to the reaction-distillation step 
after passing through a step of chlorination. In Japanese patent 
Publication Kokai No. 90206/78, an improved method is proposed which 
comprises supplying the EDC recovered from the cracking step to the above 
reaction-distillation step after passing through a step of chlorination 
and then a step of removing high-boiling chlorinated components by 
distillation. 
The heat of reaction in the production of EDC by reacting ethylene with 
chlorine is about 50 kcal/mol. This is about 7 times the quantity of heat 
required for vaporizing the EDC produced in this reaction. Therefore, when 
the reaction-distillation is conducted using this heat, a sufficient 
quantity of vapor can be produced for purifying the EDC from the 
oxychlorination step and the unreacted EDC from the cracking step as well 
as the EDC formed from ethylene and chlorine. However, as pointed out in 
Japanese Patent Publication Kokai No. 90206/78, if the unreacted EDC from 
the cracking step is fed to the reaction-distillation step, chloroprene 
and chlorinated derivatives thereof contained in the unreacted EDC exert 
an adverse influence on the reaction to decrease the selectivity of 
reaction and, as a result, the yield is markedly decreased. Feeding of the 
EDC from the oxychlorination step, which contains impurities such as 
water, ethylene chlorohydrin and chloral, to the reaction-distillation 
step is also unfavorable since such impurities cause significant corrosion 
of materials of construction and adversely influence the selectivity of 
reaction. 
For the reasons mentioned above, only the EDC formed from ethylene and 
chlorine is applicable to the reaction-distillation technique for 
purification by distillation. For the removal of impurities in the 
unreacted EDC or the EDC from the oxychlorination step, some other energy 
source is required, as explained in Japanese Patent Publication Kokai No. 
90206/78 or U.S. Pat. No. 4,172,099. Thus, in the prior art, the heat of 
reaction is not utilized efficiently and energy saving is insufficient. 
Another drawback of the conventional reaction-distillation technique is 
that the content of low-boiling impurities in the purified EDC is high as 
compared with the case where low-boiling fraction removal and high-boiling 
fraction removal are conducted in order. In the process comprising taking 
out high-boiling impurities from the column bottom, low-boiling impurities 
from the column top and the purified EDC from the middle of the column, 
the content, in the purified EDC, of low-boiling impurities such as ethyl 
chloride is significant and these impurities exert an unfavorable 
influence on the cracking step for vinyl chloride monomer production. 
A further drawback is that, in the reaction-distillation method, 
high-boiling impurities are concentrated in the reactor and cause a 
boiling point elevation, hence a rise in the reaction temperature, so that 
it is difficult to maintain the selectivity of reaction favorably. It is 
also a drawback that, in extracting high-boiling impurities from the 
column bottom, catalysts, such as ferric chloride, generally used and 
present in the reaction mixture flow out and make it difficult to maintain 
the catalyst concentration in the reaction mixture at an adequate level. 
Furthermore, it is necessary to treat the iron-containing discharge 
liquid. 
As a method of efficient utilization of the heat of reaction which is other 
than the reaction-distillation method, Japanese Patent Publication Kokai 
No. 74624/83 proposes a liquid circulation technique which comprises 
leading the liquid reaction medium in the reactor to a heat exchanger so 
that the sensible heat possessed by the medium can be utilized 
efficiently. In sensible heat utilization, a larger quantity of liquid has 
to be circulated as compared with the case where the latent heat of 
condensation of a vapor is utilized, thus the power cost for liquid 
circulation is increased. In addition, the cost of equipment is increased 
because of necessity of a larger heat exchanger due to a smaller heat 
transfer coefficient as compared with the heat transfer upon condensation 
or, in using the liquid as the heat source for a distillation column 
reboiler, unfavorable operations are required, for instance, operation to 
increase the temperature difference in the heat exchanger by operating the 
distillation column under reduced pressure to thereby lower the 
distillation temperature. 
For keeping a favorable selectivity of reaction in the above 
high-temperature process, it is effective to use ethylene in excess 
relative to chlorine, as proposed in British Patent No. 1,184,576. When 
ethylene is used in excess, unreacted ethylene is discharged. Therefore, 
for securing a high raw-material-based yield, it is important to recover 
the unreacted ethylene discharged. On the other hand, the chlorine used in 
this process is mostly produced on a commercial scale by electrolysis of 
sodium chloride. The chlorine produced by mercury process contains about 
0.2 to 0.5% of oxygen, and the chlorine produced by diaphragm process 
contains about 1 to 2% or more of oxygen. As described in Japanese Patent 
Publication Kokai No. 177928/83, oxygen is effective for maintaining the 
selectivity of the reaction on a good level and, for producing this 
effect, the oxygen contained in the chlorine or an additional quantity of 
oxygen can be utilized. The oxygen thus supplied to the reactor goes with 
and is contained in the discharge gas together with the unreacted ethylene 
and, therefore, it is important to take into consideration the risk that 
the discharge gas might form an explosive mixture composition. 
Among the known methods of recovering the unreacted ethylene, the method 
disclosed in British Patent No. 1,184,576 comprises cooling the reaction 
medium vapor generated by the heat of reaction in a high-temperature 
process, separating the resulting EDC by condensation and supplying the 
uncondensed gas to a second reactor to thereby attain recovery of the 
unreacted ethylene. For this method, it is described that an inert gas is 
added to the uncondensed gas, and accordingly formation of explosive 
mixture compositions can be avoided. However, when an inert gas such as 
nitrogen is added to the unreacted ethylene discharge, the concentration 
of ethylene to be supplied to the second reactor is lowered by dilution 
with the inert gas and, as a result, ethylene absorption becomes 
difficult. 
As an alternative, Japanese Patent Publication Kokai No. 57906/73 (Societa 
Italiana) proposes a method comprising carrying out the reaction in two 
steps by supplying at most 88% of ethylene to a second reactor in the 
unreacted state. Since the ethylene content in the discharge is high, 
formation of an explosive mixture can be avoided. When the load onto the 
second reactor is great, however, the above method is disadvantageous in 
that the heat recovery for efficient utilization of the heat of reaction 
as generated by the high-temperature reaction in the first reactor is 
decreased. 
It is one of the problems encountered by the high-temperature method that 
the selectivity and the yield of the desired EDC are decreased, because 
by-products, including 1,1,2-trichloroethane, are formed in increased 
amounts as compared with the low-temperature method. 
As methods proposed for inhibiting a side reaction which gives 
1,1,2-trichloroethane in the high-temperature process, there are 
mentioned, for instance, a two-step reaction method disclosed in Japanese 
Patent Publication Kokai No. 57906/73 wherein the high-temperature 
reaction conducted using a large excess of ethylene and the 
low-temperature reaction for converting the excess ethylene are combined, 
a method of inhibiting side reactions chemically using an additive, such 
as a cresol (Japanese Patent Publication Kokai No. 40620/81), benzene or 
the like (Japanese Patent Publication Kokai No. 50203/83), or an amine 
(Japanese Patent Publication Kokai No. 104636/83). 
A primary object of the present invention is to provide a method for 
producing EDC which is higher in heat utilization efficiency than the 
conventional reaction-distillation method and has no problems in 
selectivity of reaction and quality of product as encountered by the 
reaction-distillation technique and which is more efficient in recovery 
and utilization of reaction heat than the liquid circulation method. 
The above and other objects of the present invention will become apparent 
from the description hereinafter. 
SUMMARY OF THE INVENTION 
It has now been found that the heat of reaction can be recovered and 
utilized more efficiently than conventional methods by recovering the 
latent heat of the reaction medium vapor using a heat exchanger. 
In accordance with the present invention, there is provided a method of 
producing dichloroethane which comprises feeding ethylene and chlorine 
into a liquid reaction medium containing dichloroethane as a main 
component in a reactor, reacting the ethylene and chlorine at a 
temperature which is not lower than the boiling point of dichloroethane at 
ordinary pressure, to produce dichloroethane, leading the vapor of the 
reaction medium generated in the reactor from the top of the reactor to a 
heat exchanger, and recovering the latent heat resulting from condensation 
of the vapor in the heat exchanger.

DETAILED DESCRIPTION 
The reactor to be used in the practice of the invention may be of the tower 
type, of the vessel type or further of the loop- or double pipe-shaped 
liquid circulation type. The reactor is charged with a liquid reaction 
medium in which EDC (dichloroethane) is the main component, and thereto 
are fed ethylene and chlorine and the reaction is allowed to proceed at a 
temperature not lower than 83.degree. C. to produce EDC. The ethylene and 
chlorine are preferably fed in amounts such that ethylene is 
stoichiometrically in excess. Thus, the ethylene/chlorine ratio can be 
from 1.001 to 1.200. Iron chloride or known other catalytically active 
substances may be used as catalysts for the reaction. Oxygen is also 
preferred for improving the selectivity of reaction. Oxygen is supplied to 
the reactor generally in admixture with chlorine, the oxygen content in 
chlorine in that case being usually from 0.1% to 10% by mole. Also, known 
side reaction inhibitors such as benzene or derivatives thereof, cresol or 
derivatives thereof and amine compounds, or a chlorinated aliphatic 
unsaturated hydrocarbon of the formula: 
##STR1## 
wherein n is an integer of 1 to 3, may be included in the liquid reaction 
medium. The chlorinated aliphatic unsaturated hydrocarbon is, for example, 
tetrachloroethylene (when n=1) or hexachloro-1,3-butadiene (when n=2), and 
is caused to exist in the reaction medium in an amount of not less than 
0.001% by weight, preferably within the range of 0.005 to 0.1% by weight. 
When the amount is less than 0.001% by weight, the side reaction 
inhibiting effect cannot be produced. On the other hand, at concentrations 
above 0.05% by weight, the effect remains nearly constant in spite of 
further increase in concentration and, therefore, the use in an amount of 
at most about 0.1% by weight is practical. 
Tetrachloroethylene or hexachloro-1,3-butadiene can be assayed by gas 
chromatography or other means. Therefore, such an additive can be 
maintained at a preferable concentration by analyzing its concentration in 
the reaction medium at need and, if deficient, supplementing it. In the 
case where such a additive is discharged from the system together with the 
produced EDC, or in similar cases, the additive may be added continuously 
to the reactor. In cases where such a chlorinated aliphatic unsaturated 
hydrocarbon is formed as a reaction product in a small amount, the 
intended object can be attained by concentrating this product to a desired 
concentration. It is also possible to use both the concentration and 
addition operations. 
The heat generated by the reaction of ethylene and chlorine is partly or 
wholly consumed for the vaporization of the liquid reaction medium and, as 
a result, the reactor temperature is maintained at a constant level. 
The most characteristic feature of the present invention resides in that 
the reaction medium vapor is introduced into a heat exchanger connected 
with the upper part of the reactor and condensed there for recovery of the 
latent heat, thereby efficiently utilizing the reaction heat. Since a 
higher condensation temperature in the heat exchanger enables efficient 
utilization of the heat recovered, the reaction temperature is set at 
83.degree. C. or above, more preferably at 100.degree. to 160.degree. C. 
In the distillation for purifying EDC, the operation for removing 
high-boiling impurities requires a particularly large quantity of heat 
energy. Therefore, the heat recovered in the heat exchanger is most 
preferably used as a heat source for a reboiler of a distillation column 
used for removing high boiling impurities (this distillation column being 
hereinafter referred to as "high-boiling column"). This is effective in 
simultaneously distilling together the unreacted EDC from the cracking 
step and/or the EDC from the oxychlorination step, because it is not 
required to pass through steps of chlorination, etc. 
In case where the quantity of heat required for the reboiler of the 
high-boiling column is excessively larger than the heat of reaction or in 
case where the distillation column operation temperature is too high as 
compared with the reaction temperature, it is possible to provide a side 
reboiler, thereby applying the recovered heat to the middle of the 
high-boiling distillation column, while supplying some other energy to the 
distillation column bottom. 
Alternatively, taking into consideration the energy utilization in the 
whole vinyl chloride monomer plant, it is also possible to utilize the 
heat recovered by the heat exchanger as a heat source for preheating or 
evaporating the liquid EDC, a heat source for elevating temperature or 
evaporating liquefied ethylene or hydrogen chloride, or a heat source for 
a distillation column for EDC, hydrogen chloride or vinyl chloride 
monomer. In this manner, diversified approaches can be made for efficient 
energy utilization. 
The heat exchanger to be used may be a shell-and-tube heat exchanger of the 
thermosiphon type, kettle type or falling film type, and other heat 
exchangers. A preferable type is selected from the viewpoints of the heat 
transfer coefficient of heat-receiving side, scale adhesion, site area, 
cleaning method and so on. 
It is possible to provide a gas-liquid contact device in the upper part of 
the reaction column, in other words, between the top of the reactor and 
the heat exchanger so that droplets of the reaction mixture are prevented 
from flowing out of the reactor by bringing the reaction medium vapor into 
contact with the condensate liquid formed in the heat exchanger, whereby 
the catalyst in the reaction mixture is also prevented from flowing out. 
Furthermore, such device can also serve to concentrate the chlorinated 
aliphatic hydrocarbon used for preventing a side reaction, thereby 
maintaining it in the liquid reaction medium. Usual multiplate columns or 
packed columns may be used as the gas-liquid contact device. In case of 
not using such a gas-liquid contact column, an increased amount of the 
side reaction inhibitor is discharged together with the reaction medium. 
It is not preferable to distill and purify EDC in the gas-liquid contact 
column connected with the top of the reactor, since the side reaction 
inhibitor is also discharged when a high-boiling impurity concentrate 
liquid is drawn out of the column at a site near the bottom. 
It has been found that hexachloro-1,3-butadiene, which is one of the side 
reaction inhibitors usable in the invention, is formed in a trace amount 
in the reactor. Therefore, when hexachloro-1,3-butadiene is concentrated 
in the reaction mixture by connecting a gas-liquid contact column to the 
top of the reactor in accordance with a preferred embodiment of the 
invention, the hexachloro-1,3-butadiene concentration can be maintained at 
a preferred level without particular addition of a side reaction 
inhibitor. 
In the above case, the condensate liquid formed in the heat exchanger is 
mostly returned to the reactor, while a part thereof is taken out of the 
reactor as a product EDC. The product EDC thus drawn out is supplied to a 
distillation column where low-boiling impurities in the EDC are separated 
by simple distillation and drawn out from the distillation column top. The 
impurity fraction can be introduced into the gas-liquid contact section of 
the reactor column. Even if steam or the like is used as the heat energy 
for the above simple distillation, the steam drawn out from the column top 
can be introduced into the upper part of the reactor and arrives at the 
heat exchanger with the reaction medium vapor, whereby the heat of steam 
can be recovered. 
After removal of low-boiling impurities by simple distillation, the product 
EDC drawn out from the reactor can be sent together with the EDC produced 
by oxychlorination process and/or the unreacted EDC from the thermal 
cracking step, to the high-boiling column wherein the heat of reaction is 
utilized, for further purification of the EDC. In this way, the heat of 
reaction can be recovered and utilized for removing low-boiling and 
high-boiling impurities, whereby highly pure EDC can be obtained. 
Since the reaction medium vapor generated from the reactor contains, in 
addition to low-boiling impurities, also unreacted ethylene, oxygen and so 
on, uncondensed components may remain if the condensation temperature in 
the heat exchanger is high. Such uncondensed components may be further 
subjected to deep cooling so that useful components can be recovered. It 
is preferable, however, to take out the uncondensed components together 
with the EDC vapor and introduce the mixture into a second reactor in 
which the unreacted ethylene is recovered. If accompanied by a sufficient 
quantity of the EDC vapor, the ethylene and oxygen in the uncondensed 
components can be prevented from constituting an explosive mixture 
composition, thus the process can be operated safely. 
The region of explosive mixture composition for the case in which an 
incombustible gas, such as nitrogen, is used for dilution is shown in FIG. 
3. On the contrary, when the EDC obtained in the form of the reaction 
medium vapor is used as a third component for avoiding formation of an 
explosive mixture, the safety region is wide, as shown in FIG. 2. This is 
a further advantageous feature of the invention. 
The quantity of the vapor to be kept uncondensed in the heat exchanger can 
be selected within the range of 0.05 to 1.0 mole per mole of the chlorine 
fed to the first reactor. In ordinary reactor operation, the quantity of 
excess ethylene and/or the oxygen content are determined in most cases 
based on the number of moles of the feed chlorine. Therefore, it is 
convenient for process control for avoiding formation of an explosive 
mixture to determine the quantity of the uncondensed vapor on the same 
basis, since the proportions of the oxygen, ethylene and EDC in the 
discharge gas can be determined. If the quantity of uncondensed vapor is 
too small, there is a risk that an explosive mixture composition might be 
constituted and, if the quantity is excessive, the quantity of the 
condensate to be returned to the first reactor becomes insufficient, which 
makes it difficult to maintain the quantity of the liquid in the reactor, 
or the quantity of heat recovered in the condenser (heat exchanger) 
becomes small. To avoid these and other disadvantages, it is preferable to 
select an appropriate quantity of uncondensed vapor. It is in particular 
preferable to select the above quantity within the range such that the 
proportion of EDC in the uncondensed gas discharge is maintained at 30% by 
volume or more. This range falls within the safety region as shown in FIG. 
2 which illustrates the explosive mixture composition. It is also possible 
to operate within the safety region by maintaining the oxygen 
concentration low. 
In order to confirm that the discharge gas has not an explosive mixture 
composition but is safe, it is preferable, for example, to measure the 
rate of flow of the discharge gas or to analyze the composition of the 
discharge gas. Based on the results of such a detection, a more 
appropriate quantity of the uncondensed gas can be selected. 
If oxygen is concentrated in the uncondensed gas, there is a risk of 
formation of an explosive mixture composition. On the contrary, dilution 
to a sufficient quantity of vapor in accordance with the invention keeps 
the oxygen concentration at low levels, so any explosive mixture 
composition cannot result at all. 
The adjustment of the uncondensed vapor quantity required in the practice 
of the invention can be attained, for instance, by controlling the 
condensation temperature or pressure. Thus, by knowing the relationship 
between the temperature and vapor pressure of EDC which is the main 
component of the reaction medium, it becomes possible to maintain in the 
uncondensed state the vapor of the quantity which corresponds to the 
partial pressure of EDC vapor at the condensation temperature under a 
given pressure. 
The unreacted ethylene discharged from the reactor (first reactor) together 
with the reaction medium vapor as adjusted in the above manner is supplied 
to the second reactor. By using as the second reactor an absorption column 
in which a liquid reaction medium containing EDC as the main component is 
maintained at a lower temperature as compared with the first reactor, the 
reaction medium vapor obtained from the first reactor is condensed 
rapidly, and accordingly the unreacted ethylene is absorbed rapidly and 
thus recovered. As the second reactor, a liquid-phase chlorination reactor 
used for the low-temperature process in a vinyl chloride monomer 
production plant may be used, or an oxychlorination reactor be used as 
well. 
If the quantity of the unreacted ethylene discharged from the first reactor 
is too large, the recovery and utilization of heat becomes less 
advantageous, namely the condensation temperature lowers or the heat 
transfer coefficient lowers in latent heat recovery from the reaction 
medium vapor in the heat exchanger. Whereas the quantity of the feed 
ethylene should preferably be excessive with respect to chlorine so that 
the quantity of the unreacted chlorine discharged can be suppressed to a 
low level, the quantity of the unreacted ethylene discharged from the 
reactor should preferably be maintained at 5.0% or lower based on the 
quantity of ethylene fed to the reactor. The use as the reactor of a 
liquid circulation type one, such as a loop type or double pipe type one, 
is preferable because good mixing can be attained by the stirring effect 
produced by the circulating current, but results in increase of unreacted 
ethylene as a result of decrease in gas absorption efficiency. In case of 
using a liquid circulation reactor, the quantity of unreacted ethylene can 
be reduced by constructing only the lower part of the reactor to a 
circulation type, thereby preventing ethylene from passing through the 
reactor without reacting with chlorine. 
According to the process of the present invention, advantages as mentioned 
below can be obtained. A high heat utilization efficiency can be attained 
by recovering and utilizing the heat of reaction in accordance with the 
present invention, thereby saving the heat energy, such as steam, required 
in the prior art by a quantity of heat approximately corresponding to the 
heat of reaction. The heat utilization is not so limited and can be 
utilized for various purposes. Even in case of using as a heat source for 
distillation of EDC, an existing distillation column can be used as it is 
and the quality of the product EDC is not affected adversely, since the 
heat is utilized indirectly through the heat exchanger. Also, the heat 
transfer efficiency in heat exchange is good, since the latent heat of 
condensation of the reaction medium vapor is recovered. 
In accordance with the invention, the liquid in the reactor need not be 
drawn out and, therefore, it is not necessary to adjust the catalyst 
concentration by adding the catalyst from the outside or to treat an 
iron-containing high-boiling fraction. Since the condensation temperature 
in the heat exchanger is high and therefore the unreacted ethylene and 
oxygen in the uncondensed gas are in a state diluted with the EDC vapor, 
the invention produces the effect of allowing safe operation while 
avoiding explosive mixture compositions. In particular, when the 
uncondensed gas is introduced into the second reactor for the production 
of EDC from the unreacted ethylene, the method according to the invention 
is advantageous in that particularly pressurized nitrogen as needed in the 
prior art is no more necessary. The safety region forming no explosive 
mixture composition in the case where EDC is used as a third component to 
be added to oxygen and ethylene is wide as compared with the case where 
nitrogen is used as the third component in accordance with the prior art. 
Therefore, the allowable range of load variation in the reactor or 
variation in the operational condition becomes wide and this is 
advantageous from the operational procedure viewpoint. A further advantage 
is that since the quantity of gas required for dilution to attain a 
composition within the safety region is smaller in the case where EDC is 
used as the diluent gas as compared with the case where nitrogen is used, 
the scale of equipment can be reduced. When the unreacted ethylene in the 
discharge gas to be fed to the second reactor is diluted with nitrogen in 
accordance with the prior art, the ethylene concentration is low and 
therefore the ethylene is absorbed into the solvent slowly and can hardly 
be recovered. On the contrary, in accordance with the method of the 
invention, EDC is condensed rapidly in the second reactor which is 
maintained at a lower temperature, and accordingly the unreacted ethylene 
is concentrated significantly and absorbed rapidly, hence can be recovered 
with ease. 
When a large excess of ethylene is fed in accordance with the prior art, 
the proportion of ethylene which undergoes the high-temperature reaction 
in the first reactor is small, so the heat utilization efficiency is low 
even if utilization of the heat of high-temperature reaction is desired. 
On the contrary, the method according to the invention is advantageous in 
that since it is not necessary to increase the unreacted ethylene content 
to an excessive level, the rate of heat recovery and utilization can be 
increased, and also from the equipment cost standpoint, it is advantageous 
in that the load on the second reactor is light. 
When a chlorinated aliphatic unsaturated hydrocarbon, such as 
hexachloro-1,3-butadiene or tetrachloroethylene, is used as a side 
reaction inhibitor in accordance with a particularly preferred embodiment 
of the invention, by-product can be used as it is as an inhibitor with 
advantage. By reacting ethylene and chlorine in a liquid reaction medium 
containing EDC as the main component in the presence of the side reaction 
inhibitor, the amounts of side reaction products, such as 
1,1,2-trichloroethane, can be reduced to a significant extent, and even in 
the high-temperature reaction, EDC can be produced in high yields. In this 
manner, the invention produces a further, but not less, effect of enabling 
commercial practice of the high-temperature process which has many 
advantages with respect to efficient utilization of the heat of reaction, 
EDC purification, etc. 
The present invention is more specifically described and explained by means 
of the following Examples. It is to be understood that the present 
invention is not limited to the Examples, and various changes and 
modifications may be made in the invention without departing from the 
spirit and scope thereof. 
EXAMPLE 1 
EDC was prepared according to an embodiment of the present invention by 
using the apparatus shown in FIG. 1. 
Reactor column A having an effective height of 6 m and equipped with a 
3-meter circulation loop at the lower portion thereof was charged with 
liquid dichloroethane (EDC) and further with ferric chloride at a 
dissolved concentration of about 0.1% by weight. Ethylene was fed at a 
flow rate of about 2.04 ton/hr from near the bottom of the column through 
conduit 2, and chlorine containing about 2.0% by volume of oxygen which 
was divided into 2 portions, was fed at a flow rate of about 5.02 ton/hr 
to the lower part of the column through two conduits 1 provided at 
different heights. The reaction was conducted at 135.degree. C. The 
reaction medium gone to boil due to the heat of reaction, thereby 
generating about 50 ton/hr of vapor. This vapor was fed to heat exchanger 
C through gas-liquid contact zone B via a conduit 3. The heat exchanger C 
was a side reboiler of a distillation column (high-boiling column) F for 
purification by removal of high-boiling fractions from EDC. Most of the 
reaction medium vapor was condensed to liquefy at about 125.degree. C. and 
returned to the gas-liquid contact zone B via a conduit 4. The main 
components of the uncondensed gas discharged from the heat exchanger C 
into a conduit 7 were about 32 Nm.sup.3 /hr of oxygen, about 48 Nm.sup.3 
/hr of ethylene, about 240 Nm.sup.3 /hr of EDC vapor, and other 
low-boiling impurities, and this gas was fed to second reactor G. The 
second reactor was a liquid-phase reactor operated at about 60.degree. C. 
in which EDC containing about 200 wt. ppm of dissolved ferric chloride was 
charged. In the second reactor, the EDC vapor introduced through the 
conduit 7 was quickly condensed to liquefy, while ethylene was reacted 
with separately supplied chlorine. 
The product EDC was withdrawn from the middle part of the gas-liquid 
contact zone B at a rate of about 6.5 ton/hr and fed to distillation 
column D through conduit 5. In the column D, the product EDC was distilled 
under the heat of steam supplied at a rate of about 0.1 ton/hr from 
reboiler H, and the vapor (low boiling components) from the column top was 
fed again to the gas-liquid contact zone B through conduit 6. The EDC 
obtained via the conduit 8 was fed to distillation column E in which 
low-boiling impurities were further removed through conduit 12. To the 
distillation column E, EDC obtained from the oxychlorination step and EDC 
recovered from the cracking step were also fed simultaneously for 
purification through conduits 9 and 10. The EDC withdrawn from the bottom 
of distillation column E was fed through conduit 11 to the distillation 
column F where high-boiling impurities were removed through conduit 14 and 
the purified EDC was obtained from the column top through conduit 13. The 
distillation column F had heretofore been operated by supplying steam to 
reboiler I to give the energy necessary for purification, but by utilizing 
the heat exchanger C as a side reboiler for recovery and re-utilization of 
the heat of reaction according to the present invention, there could be 
realized saving of about 7.0 ton/hr of steam in the purification of the 
conventional order. 
EXAMPLE 2 
EDC was produced by using the apparatus shown in FIG. 4. First reactor A 
was charged with EDC liquid and about 1,500 wt. ppm of ferric chloride was 
dissolved therein as a catalyst. Chlorine was fed from conduit line 2 at a 
rate of 700 kg/hr, while ethylene was fed from conduit line 1 at a rate of 
287 kg/hr, and the reaction was conducted at about 2% by mole excess of 
ethylene. The chlorine contained 2% by mole of oxygen. With the reactor 
column top pressure maintained at 4 atm, the liquid reaction medium was 
boiled at 135.degree. C. to maintain the temperature constant. The vapor 
of the reaction medium gasified by the heat of reaction was fed to heat 
exchanger B through the conduit line 3. The condensation temperature in 
the heat exchanger B was controlled at 124.degree. C. by adjusting heat 
medium 7. A portion of the condensate was withdrawn as a product through 
conduit 5, while the remainder was returned to the reactor A through 
conduit 4. The vapor pressure of EDC at 124.degree. C. was about 3.08 
atm, which was about 75% of the total pressure. The components withdrawn 
as uncondensed gases from conduit 6 to feed to second reactor C were about 
4,400 Nl/hr of oxygen, about 4,400 Nl/hr of ethylene, about 33,200 Nl/hr 
of EDC and about 2,000 Nl/hr of other components. Since this composition 
was within the safety region indicated in FIG. 2, it was not explosive. 
The total amount of gas flowing through the conduit 6 was measured and the 
condensation temperature was adjusted to ensure an appropriate flow rate. 
The second reactor C charged with EDC and connected to an external heat 
exchanger D was maintained at 60.degree. C. The fraction from the conduit 
6 was fed to the reactor C and reacted with chlorine from conduit line 2, 
the amount of chlorine fed corresponding to the amount of unreacted 
ethylene. In this stage, the load on the first reactor was about 98% of 
the total load, and the heat of reaction in the first reactor was 
recovered by the heat medium 7 of the heat exchanger B for re-use. The 
load on the second reactor was about 2% of the total load, and the 
ethylene concentration after liquefaction of EDC was about 45%, thus 
recovery by absorption was quite easy. The total volume of discharge gas 
was about 44,000 Nl/hr. The heat of reaction was efficiently recovered to 
the amount of 98%. 
EXAMPLE 3 
The reaction was conducted in the same manner as in Example 2 except that 
ethylene was fed at 290 kg/hr, the ethylene excess being about 3%, and the 
oxygen content in chlorine was 2%. When the reaction temperature and the 
condensation temperature were maintained at 135.degree. C. and 100.degree. 
C., respectively, the components discharged as uncondensed gases from the 
conduit 6 were about 4,400 Nl/hr of oxygen, about 17,600 Nl/hr of 
ethylene, about 16,200 Nl/hr of EDC, and about 2,000 Nl/hr of others. This 
composition was within the safety region shown in FIG. 2. 
The volume of discharge gas under the above conditions was about 40,000 
Nl/hr. Compared with the first reactor, the ethylene loading for the 
second reactor C was as low as about 8% and the ethylene concentration 
after liquefaction of EDC was as high as about 75%. Therefore, recovery by 
absorption was easy. The heat of reaction was efficiently recovered to the 
amount of 92%. 
EXAMPLE 4 
The reaction was conducted in the same manner as in Example 2 except that 
chlorine was fed at 200 kg/hr, the oxygen content in the chlorine was 3%, 
and ethylene was fed at a rate of 80 kg/hr with an excess of about 1%. 
When the reaction temperature and the condensation temperature were 
maintained at 110.degree. C. and 97.degree. C., respectively, the EDC 
vapor pressure at this condensation temperature was 1.50 atm against the 
total pressure of 2.16 atm. The components discharged as uncondensed gases 
from the conduit 6 were about 1,900 Nl/hr of oxygen, about 630 Nl/hr of 
ethylene, about 6,100 Nl/hr of EDC, and about 100 Nl/hr of other gases. 
Thus, this composition was within the safety region shown in FIG. 2. 
In this operation, the volume of the discharge gas was about 8,700 Nl/hr. 
The ethylene load on the first reactor was about 99% and the heat of 
reaction could be recovered. The load on the second reactor was as small 
as about 1% and the ethylene concentration after liquefaction of EDC was 
about 25%, thus recovery by absorption was easy. 
EXAMPLE 5 
The reaction was conducted in the same manner as in Example 2 except that 
chlorine was fed at a flow rate of 500 kg/hr, the oxygen content in the 
chlorine was 1.5%, and ethylene was supplied at a flow rate of 207 kg/hr 
with an excess of about 5% based on the chlorine. When the reaction 
temperature and the condensation temperature were maintained at 
130.degree. C. and 120.degree. C., respectively, and the EDC vapor 
pressure at the condensation temperature was 2.7 atm against the total 
pressure of 3.7 atm, the components discharged as uncondensed gases were 
about 2,300 Nl/hr of oxygen, about 7,800 Nl/hr of ethylene, about 36,000 
Nl/hr of EDC and about 1,500 Nl/hr of other gases. This composition was 
within the safety region shown in FIG. 2. The total volume of discharge 
gases was about 47,000 Nl/hr. The ethylene load on the second reactor was 
about 5% of the total load and the ethylene concentration after 
liquefaction of EDC was about 70%, thus permitting easy recovery by 
absorption. The heat of reaction was efficiently recovered to the amount 
of 95%. 
EXAMPLE 6 
The reaction was conducted in the same manner as in Example 2 except that 
chlorine was fed at a rate of 800 kg/hr, the oxygen content in the 
chlorine was 2.0%, and ethylene was fed at a rate of 121 kg/hr. The excess 
percentage of ethylene was about 2%. When the reaction temperature and the 
condensation temperature were maintained at 120.degree. C. and 95.degree. 
C., respectively, and the EDC vapor pressure at the condensation 
temperature was 1.42 atm against the total pressure of 2.80 atm, the 
components discharged as uncondensed gases were about 1,900 Nl/hr of 
oxygen, about 1,900 Nl/hr of ethylene, about 4,200 Nl/hr of EDC and about 
300 Nl/hr of other gases. This composition was within the safety region 
shown in FIG. 2. The total volume of discharge gas under the above 
conditions was about 8,300 Nl/hr. The load on the second reactor was as 
small as about 2% of the total ethylene load and the ethylene 
concentration after liquefaction of EDC was about 50%, thus permitting 
easy recovery by absorption. The heat of reaction was efficiently 
recovered to the amount of 98%. 
COMATIVE EXAMPLE 1 
The reaction was conducted in the same manner as in Example 2 except that 
the condensation temperature was set at 50.degree. C. The EDC vapor 
pressure at 50.degree. C. was 0.308 atm relative to the total pressure of 
4.018 atm. To avoid the explosive composition, ethylene feed was set at 
325 kg/hr, which represented an excess of about 35%. The components 
discharged as uncondensated gases were about 4,400 Nl/hr of oxygen, about 
76,600 Nl/hr of ethylene, about 6,800 Nl/hr of EDC and about 200 Nl/hr of 
other gases. Thus, the discharge gas formed a composition within the 
safety region with a large excess of ethylene, as shown in FIG. 2, and 
accordingly such a composition was safe irrespective of dilution with EDC. 
The volume of discharge gas was about 88,000 Nl/hr, which was greater than 
in Example 2. Since the load on the second reactor was as high as 26% of 
the total ethylene load, the equipment size had to be increased as 
compared with the one Example 2. Moreover, the recovery of heat produced 
by the high-temperature reaction in the first reactor was 74% of the total 
heat of reaction and this percentage was lower than the percentage that 
could be realized in accordance with Example 2. 
COMATIVE EXAMPLE 2 
The reaction was conducted in the same manner as in Example 2 except that 
the condensation temperature was set at 50.degree. C. The EDC vapor 
pressure at this condensation temperature was 0.308 atm against the total 
pressure of 4.018 atm. To avoid the explosive composition, nitrogen gas 
was fed at a rate of about 72,200 Nl/hr. Under the above conditions, the 
components discharged as uncondensed gases were about 4,400 Nl/hr of 
oxygen, about 4,400 Nl/hr of ethylene, about 6,800 Nl/hr of EDC, about 
72,000 Nl/hr of nitrogen and about 200 Nl/hr of other gases. This was 
within the safety region shown in FIG. 3, owing to dilation by nitrogen 
gas. 
In the above operation, nitrogen pressurized to at least 4.018 atm had to 
be fed. Moreover, the volume of discharge gas was about 88,000 which was 
about twice as large as the volume in Example 2. The load on the second 
reactor was about 2% of the total ethylene load, which was the same as in 
Example 2, but since the ethylene concentration was as low as about 5%, 
absorption was much delayed as compared with Example 2 and thus, recovery 
was difficult. 
EXAMPLE 7 
A stainless steel reactor A having a column diameter of 20 cm, shown in 
FIG. 5, was charged with liquid EDC to the level of 6 m and anhydrous 
ferric chloride was added thereto so that the concentration of dissolved 
ferric chloride was about 5 wt. ppm, followed by addition of 
hexachloro-1,3-butatiene at the level of 200 wt. ppm as dissolved. From 
near the bottom of the reactor, ethylene 1 and chlorine 2 were 
respectively fed at a flow rate of 40 Nm.sup.3 /hr. The chlorine contained 
about 1.5 mole % of oxygen. When the reactor top pressure was maintained 
at about 2.9 kg/cm.sup.2 G, the reaction temperature became about 
135.degree. C. Thus, the operation was feasible under boiling of the 
reaction medium. The EDC vapor gasified by the heat of reaction was 
withdrawn from the top, and fed to through conduit 5 and condensed in heat 
exchanger B. The condensate was guided into receptor C and a portion 
thereof was recycled through conduit 3 so as to maintain the liquid level 
in the reactor A, while the remainder was withdrawn as a product EDC 
through conduit 4. The heat of reaction could be recovered from the heat 
exchanger B. After about 50 hours of reaction, when the steady state had 
been established, the product EDC was sampled and analyzed by gas 
chromatography. The by-products were as shown below. 
______________________________________ 
1,1,2-Trichloroethane 
0.36 wt. % 
Ethyl chloride 0.02 wt % 
1,1,2-Tetrachloroethane 
0.04 wt. % 
Others 0.06 wt % 
______________________________________ 
The reaction selectivity for EDC was about 99.61% based on ethylene. 
The above procedure was repeated except that hexachloro-1,3-butadiene was 
not added at all. About 50 hours after initiation of the reaction, the 
liquid within the reactor was sampled and analyzed by gas chromatography. 
Hexachloro-1,3-butadiene was not detected. The product EDC was also 
sampled and analyzed by gas chromatography. The by-products in the product 
were as follows: 
______________________________________ 
1,1,2-Trichloroethane 
0.93 wt. % 
Ethyl chloride 0.02 wt. % 
1,1,2-Tetrachloroethane 
0.11 wt. % 
Others 0.10 wt. % 
______________________________________ 
The reaction selectivity for EDC under the above conditions was about 
99.11% based on ethylene. 
EXAMPLE 8 
The reaction was carried out in the same manner as in Example 7 except that 
tetrachloroethylene (concentration of tetrachloroethylene dissolved: 300 
wt. ppm) was used instead of hexachloro-1,3-butadiene, the reactor top 
pressure was about 2.7 kg/cm.sup.3 G and the reaction temperature was 
about 130.degree. C. 
About 50 hours after initiation of the reaction, the product EDC was 
sampled and analyzed. The by-products in the product EDC were as follows: 
______________________________________ 
1,1,2-Tetrachloroethane 
0.25 wt. % 
Ethyl chloride 0.02 wt. % 
1,1,2-Tetrachloroethane 
0.02 wt. % 
Others 0.03 wt. % 
______________________________________ 
The reaction selectivity for EDC was about 99.74% based on ethylene. 
The above procedure was repeated except that tetrachloroethylene was not 
added at all. 
About 50 hours after initiation of the reaction, the product EDC was 
sampled and analyzed. The by-products in the product EDC were as follows: 
______________________________________ 
1,1,2-Trichloroethane 
0.87 wt. % 
Ethylene chloride 0.02 wt. % 
1,1,2-Tetrachloroethane 
0.09 wt. % 
Others 0.11 wt. % 
______________________________________ 
The reaction selectivity for EDC was about 99.16% based on ethylene. 
EXAMPLE 9 
The reaction was conducted in the same manner as in Example 7 except that 
hexachloro-1,3-butadiene was added so that the concentration of 
hexachloro-1,3-butadiene dissolved was 60 wt. ppm, the column top pressure 
was set at 1.8 kg/cm.sup.3 G and the temperature was held at 120.degree. 
C. 
About 50 hours after initiation of the reaction, the product EDC was 
sampled and analyzed. The by-products in the product EDC were as follows: 
______________________________________ 
1,1,2-Trichloroethane 
0.19 wt. % 
Ethyl chloride 0.02 wt. % 
1,1,2-Tetrachloroethane 
0.02 wt. % 
Others 0.03 wt. % 
______________________________________ 
The reaction selectivity for EDC was about 99.79% based on ethylene. 
The above procedure was repeated except that hexachloro-1,3-butadiene was 
not added at all. 
About 50 hours after initiation of the reaction, the product EDC was 
sampled and analyzed. The by-products in the product EDC were as follows: 
______________________________________ 
1,1,2-Trichloroethane 
0.68 wt. % 
Ethyl chloride 0.02 wt. % 
1,1,2-Tetrachloroethane 
0.08 wt. % 
Others 0.10 wt. % 
______________________________________ 
The reaction selectivity for EDC was about 99.31% based on ethylene. 
EXAMPLE 10 
A stainless steel reactor A equipped with a circulation path, shown in FIG. 
6, was charged with liquid EDC, and anhydrous ferric chloride was added at 
a concentration of 600 wt. ppm as dissolved. From near the bottom of the 
reactor, ethylene 1 and chlorine 2 were respectively fed at a rate of 50 
Nm.sup.3 /hr. The feed chlorine contained about 1.0 mole % of oxygen. The 
reaction temperature was maintained at 135.degree. C. and the reaction 
medium vapor generated by the heat of reaction was led into a gas-liquid 
contact section D connected to the top of the reactor A and brought into 
continuous counter-flow contact with the condensate of the column top 
vapor introduced through conduit 3. The heat of reaction was recovered by 
a heat exchanger (condensor) B disposed on and connected with the top of 
the gas-liquid contact section D through conduit 5. The condensate was led 
to a tank C, and the uncondensed gases were discharged from the tank C. 
The EDC produced by the reaction was continuously withdrawn from near the 
intermediate position of the gas-liquid contact section D through conduit 
4. The liquid reaction mixture was not withdrawn. 
After about 10 days of continuous operation, the composition of impurities 
included in the liquid in the reactor and those included in the product 
EDC became constant. The reaction mixture was sampled and analyzed by gas 
chromatography, whereby it was detected that about 250 wt. ppm of 
hexachloro-1,3-butadiene was dissolved. The product EDC contained the 
following by-products. 
______________________________________ 
1,1,2-Trichoroethane 
0.39 wt. % 
Ethyl chloride 0.02 wt. % 
1,1,2,2-Terachloroethane 
0.05 wt. % 
Hexachloro-1,3-butadiene 
0.0002 wt. % 
Others 0.05 wt. % 
______________________________________ 
The reaction selectivity for EDC was about 99.60% based on ethylene. 
The above procedure was repeated except that, in order to obtain 
high-purity EDC by distillation of the product EDC, the reaction mixture 
was continuously withdrawn. 
The rate of withdrawal of the liquid reaction mixture was about 10% based 
on the amount of the product EDC, that was about 20 kg/hr. 
The amount of EDC obtained by distillation for purification was about 200 
kg/hr. Since the reaction mixture withdrawn entrained some of dissolved 
ferric chloride, the corresponding amount of anhydrous ferric cloride was 
added so as to maintain its concentration. 
After 10 days of continuous operation, the liquid withdrawn from the 
reactor was sampled and analyzed for by-products. The results are as 
follows: 
______________________________________ 
1,1,2-Trichloroethane 
8.25 wt. % 
Ethyl chloride 0.005 wt. % 
1,1,2,2-Tetrachloroethane 
2.31 wt. % 
Hexachloro-1,3-butadiene 
0.002 wt. % 
Others 1.56 wt. % 
______________________________________ 
The concentrations of impurities in the product EDC obtained after 
purification by distillation were as follows: 
______________________________________ 
1,1,2-Trichloroethane 
0.01 wt. % 
Ethyl chloride 0.02 wt. % 
1,1,2,2-Tetrachloroethane 
0.001 wt. % 
Hexachloro-1,3-butadiene 
not detected 
Others 0.04 wt. % 
______________________________________ 
The reaction selectivity for EDC calculated from the total amount of these 
by-products was about 99.0% on the ethylene basis.