Process for preparing ethylene dichloride

Method of producing ethylene dichloride characterized by reaction of ethylene and chlorine in a reaction zone containing a circulating medium and maintained below the vaporization point of the medium, and utilization of the heat from the reaction to vaporize and rectify a portion of the circulating medium in another zone to recover the product.

BACKGROUND OF THE INVENTION 
The present invention relates to the preparation of ethylene dichloride by 
the addition chlorination of ethylene. In its preferred form, the 
invention relates to an improved process for preparing 1,2-dichloroethane 
by addition chlorination, wherein heat generated by the exothermic 
reaction of chlorine and ethylene is used to vaporize and rectify the 
ethylene dichloride produced. 
The preparation of dichloroalkanes by the chlorination of an appropriate 
olefin in the liquid phase under suitable conditions is well known. U.S. 
Pat. No. 2,929,852, British Pat. No. 1,231,127, British Pat. No. 760,308, 
and DT No. 2224253 disclose methods of preparing dichloroalkanes wherein 
an olefin is addition chlorinated (with chlorine) in the liquid phase at 
suitable temperatures. According to these patents, the dichloroalkane 
formed is distilled or vaporized, and is passed to further treatment. In 
the case of U.S. Pat. No. 2,929,852 and British Pat. No. 1,231,127, the 
vaporized dichloroalkane is passed to a closely related fractional 
distillation column where the heat of reaction of chlorine and ethylene is 
used to fractionate the vaporized dichloroalkane. British Pat. No. 
1,231,127 also provides for the fractionation of dichloroalkane obtained 
from at least one other source. According to this patent, the heat of 
reaction contained in the vaporized dichloroalkane is sufficient to 
rectify the dichloroalkane vapor, and because of the large excess of heat 
present, may be used additionally to rectify crude dichloroalkane from 
another source, e.g., crude dichloroalkane obtained from the 
oxychlorination of an olefin, and/or unconverted recycle dichloroalkane 
from a pyrolysis system in which dichloroalkane is pyrolyzed to a given 
monochloroalkene. 
The procedures outlined in these patents suffer from a number of 
disadvantages. For example, a number, if not all, of these procedures 
employ a boiling liquid medium for carrying out the chlorination reaction. 
One difficulty with such a system is that if vaporization occurs at the 
site of reaction, the vapor that is formed acts as a stripping gas to 
strip unreacted chlorine and ethylene before they can react or dissolve. 
Poor conversions and selectivity may result. 
An additional problem associated with at least one of the prior art 
processes relates to bubble formation. In this prior art process, ethylene 
and chlorine are introduced at a slow rate into the bottom of a tank 
reactor which is partially filled with ethylene dichloride and catalyst. 
The ethylene dichloride formed is vaporized from the tank and conducted to 
a fractionation column where it is purified. However, if attempts are made 
to increase the rate of addition of ethylene and chlorine, all of the 
ethylene does not dissolve, and tends to form gas bubbles which pass, 
unreacted or partially-reacted, up the liquid and out of the tank. Thus, 
this prior art process is limited in terms of throughput, and must be 
maintained at relatively slow rates of addition of reactants. 
Moreover, if feed rates are increased, and more chlorine and ethylene do 
react, the increased heat given off promotes increased boiling, and may 
result in a safety problem as well as in the formation of by-products. In 
another prior art process, where increased rates of addition of ethylene 
and chlorine are maintained, an external heat exchange system is required 
in order to regulate bubble size. 
SUMMARY OF THE INVENTION 
The present invention overcomes these problems by providing a closely 
controlled reaction system in which the reaction of chlorine and ethylene 
is carried out in a rapidly circulating liquid medium in a zone of 
increased pressure, at a temperature which is below the vaporization 
temperature of the medium at the pressure in the zone, and in which the 
product is rapidly conveyed to a zone of reduced pressure wherein at least 
a portion of the medium, now including the product ethylene dichloride, 
vaporizes and is passed to recover ethylene dichloride. 
More particularly, the present invention relates to a process comprising 
introducing ethylene and chlorine into a reaction zone of increased 
pressure containing a circulating liquid medium maintained at a 
temperature below the vaporization point of the medium at the pressure in 
the reaction zone, and forming crude liquid ethylene dichloride; passing 
the crude liquid ethylene dichloride as a part of the circulating liquid 
medium to a zone of reduced pressure maintained at a pressure and 
temperature at which at least a portion of the circulating liquid medium 
is vaporized by means of the heat of reaction of the chlorine and the 
ethylene, passing the vapor containing ethylene dichloride to a 
rectification or fractionation zone and rectifying the ethylene dichloride 
containing vapor by means of the heat of reaction of the chlorine and 
ethylene, recovering purified ethylene dichloride from the rectification 
zone; while simultaneously returning the remainder of the circulating 
liquid medium from the zone of reduced pressure to the reaction zone. In 
its preferred form, the present invention provides a method wherein 
ethylene and chlorine are reacted in a circulating liquid medium in a zone 
of increased pressure, as indicated, and in the presence of a catalyst at 
a temperature of from about 85.degree. C. to about 180.degree. C. to 
produce crude liquid ethylene dichloride, the crude liquid ethylene 
dichloride produced is passed as a part of the circulating liquid medium 
to a zone of reduced pressure where at least a portion of the circulating 
liquid medium is vaporized by the heat of reaction and is passed to a 
fractionation or rectification zone to recover ethylene dichloride, the 
circulating liquid medium being returned to the reaction zone. Preferably, 
the fractionation zone is also supplied with an ethylene 
dichloride-containing stream from another source, such as the ethylene 
dichloride separation section of an ethylene dichloride pyrolysis zone. 
The ethylene dichloride-containing vapor and the ethylene 
dichloride-containing stream are fractionated by the heat of reaction to 
produce a purified ethylene dichloride product. 
In its most preferred form, the invention comprises a process for producing 
ethylene dichloride wherein ethylene and chlorine are reacted in a 
circulating liquid reaction medium in a zone of increased pressure, as 
indicated, and at a temperature of from about 85.degree. C. to about 
160.degree. C. in the presence of a catalyst to produce crude liquid 
ethylene dichloride, the crude ethylene dichloride is passed as a part of 
the circulating liquid medium to a zone of reduced pressure wherein at 
least a portion of the circulating medium is vaporized by the heat of 
reaction of the chlorine and ethylene, the ethylene dichloride-containing 
vapor is passed to a fractionation zone to which is also fed an ethylene 
dichloride-containing stream from the ethylene dichloride separation 
section of an ethylene dichloride pyrolysis zone, the ethylene 
dichloride-containing vapor and the ethylene dichloride-containing stream 
are fractionated utilizing the heat generated by the reaction of chlorine 
and ethylene to produce a purified ethylene dichloride product; while 
concomitantly returning the circulating liquid medium from the zone of 
reduced pressure to the reaction zone. The invention also provides for the 
chlorination of the ethylene dichloride-containing stream, prior to its 
entry into the fractionation zone, to chlorinate impurities, such as 
chloroprene, to heavier boiling impurities which may be removed in the 
fractionation zone.

DETAILED DESCRIPTION OF THE INVENTION 
In order to describe the invention in greater detail, reference is made to 
FIG. 1 of the accompanying drawings. Ethylene and chlorine are introduced, 
for example, as gases, via lines 1 and 2 into circulating loop reactor 3, 
which contains a circulating liquid medium containing, e.g., ethylene 
dichloride, and a catalyst, e.g., ferric chloride. The chlorine and 
ethylene need not be pure. The chlorine, for example, may contain from 1 
to 10 percent air, small amounts of hydrogen, as well as other components. 
Similarly, the ethylene may, and often does, contain minor amounts of 
other materials. The chlorine may be introduced as a liquid, wholly or 
partially, if desired. 
The ratios of reactants supplied to the circulating liquid reaction medium 
may be varied to considerable extent. Preferably, the reactants are 
supplied in such proportions that there is a slight excess of ethylene 
over and above the stoichiometric amount required to react with the 
chlorine. A preferred ratio is from about 1.01 mols to about 1.10 mols of 
ethylene per mol of chlorine. However, a small excess of chlorine may be 
employed. Feed rates may vary greatly, and depend to a large extent on 
equipment size, output desired, circulation rates desired, etc. Those 
skilled in the art can readily adjust feed rates to achieve good results. 
The reaction of ethylene and chlorine is generally conducted in the 
presence of a catalyst. In the process of the invention, any of the well 
known catalysts generally associated with this reaction may be employed. 
For example, metal chlorides, such as ferric chloride, antimony chloride, 
and copper chloride, may be used. Ferric chloride is preferred. The 
specific catalyst employed is a matter of choice, and constitutes no part 
of the invention. Generally, the catalyst is present in an amount of from 
about 50 parts per million to about 6000 parts per million, although the 
specific amount used is largely a matter of choice. 
The temperatures at which the chlorination reaction is carried out include 
those temperatures at which the circulating liquid medium, into which the 
ethylene and chlorine are introduced, will not vaporize in the area or 
zone of reaction under the pressure conditions employed. Thus, where 
ethylene dichloride is the desired product, the reaction of ethylene and 
chlorine is carried out in a circulating liquid medium maintained at a 
temperature of from about 85.degree. C. to about 180.degree. C., under 
sufficient system pressure so that the ethylene dichloride, which normally 
boils at about 83.5.degree. C., will not vaporize in the reaction zone. 
Temperatures of from about 85.degree. C. or 90.degree. C. to about 
160.degree. C. are preferred. 
The pressures employed in the reaction zone may be varied considerably, 
provided they are sufficient to prevent the vaporization of the ethylene 
dichloride formed in the reaction zone at the temperature of the reaction 
zone, and satisfy other conditions, to be mentioned presently. Those 
skilled in the art will recognize that a pressure differential exists 
between the top and bottom of leg 4 of reactor 3. This pressure 
differential is provided primarily by the static pressure of the 
circulating liquid medium in leg 4, and will vary with the height of the 
leg. For purposes of this invention, the differential must be sufficient 
to maintain the ethylene dichloride formed in the reaction zone in the 
liquid phase until it has passed out of the reaction area or zone. The 
pressure and temperature in chamber 5 are maintained at levels which will 
cause at least a portion of the circulating medium to flash or vaporize. 
Chamber 5 is in effect an extension of leg 4. Once the ethylene dichloride 
formed is removed from the reaction zone, by means of the circulating 
medium, and passed up leg 4 and into chamber 5, the combination of the 
reduction in pressure with the presence of the heat of reaction causes a 
portion of the circulating liquid medium, which includes the crude 
ethylene dichloride formed, to vaporize. Some of the circulating medium 
may, depending on conditions, vaporize in the upper portion of leg 4. 
In general, the pressure differential between the reaction zone and the 
vaporization zone need be sufficient only to maintain the ethylene 
dichloride formed in the liquid state until it is circulated out of the 
reaction zone. Thus, the pressure differential may comprise quite low 
amounts to great differences. In practice, the pressure differential 
between the reaction zone (considered to include the area of entry of the 
reactants up to a point where the reaction is essentially complete) and 
the vaporization zone (considered to begin where a portion of the medium 
tends to vaporize) may range from about 1.0 pounds per square inch to 
about 25.0 pounds per square inch or greater. A pressure differential of 
from about 2.0 pounds per square inch to about 20 pounds per square inch 
is preferred. Those skilled in the art will recognize that between the 
reaction zone and the vaporization zone there exists a "quiet" zone in 
which essentially no reaction or vaporization takes place. This zone will 
vary in size, depending, for example, on the height of leg 4, the velocity 
of the liquid, etc. Where excellent control is maintained, the "quiet" 
zone can be much reduced in size. 
In general, pressures in chlorinator 3 may vary from atmospheric (in the 
vaporization zone) to as much as 50 pounds per square inch (gauge) or 
greater, in the reaction zone. For example, pressures in the vaporization 
zone will normally range from atmospheric pressure to about 40 pounds per 
square inch, with the pressures of atmospheric to about 30 pounds per 
square inch being preferred. In the reaction zone, pressures will range 
from about 2 pounds per square inch (gauge) to about 50 or 60 pounds per 
square inch, with a range of from about 10 to about 45 pounds per square 
inch being preferred. 
Those skilled in the art will also recognize that a temperature 
differential, though slight, exists between the top and bottom of leg 4 
(and chamber 5). As a portion of the circulating liquid begins to flash at 
the top of leg 4, absorption of heat by the flashed vapor occurs, thus 
creating a slightly cooler area than the reaction zone, where the highly 
exothermic reaction is occurring. The circulating medium, now slightly 
cooler, is returned through outlet 6 via leg 7 to the reaction zone. In 
general, a temperature differential of from about 0.5.degree. C. to about 
10.0.degree. C. is maintained, with a range of from about 1.5.degree. C. 
to 6.5.degree. C. being preferred. 
Actual temperatures in the vaporization zone may be adjusted considerably 
by those skilled in the art, and will depend, in the given situation, on a 
number of factors including the composition of the liquid medium. 
Normally, temperatures in the vaporization zone will range from about 
83.5.degree. C. to about 180.degree. C., with a range of from about 
83.5.degree. C. to about 160.degree. C. being preferred. 
The velocity of the circulating liquid medium in the area of the entry of 
the reactants is significant, if not critical, in achieving the results of 
the invention. The medium must be maintained in a state of turbulence by 
the use of a circulation rate, which when taken in conjunction with vessel 
size, liquid density, and liquid viscosity, will achieve substantial 
dissolution or reaction of the chlorine and ethylene and will achieve 
rapid distribution of the heat of reaction so that vaporization of the 
ethylene dichloride formed does not occur under pressure and temperature 
conditions employed. This circulation rate will vary to some extent based 
on reactor configuration and size. In general, a circulation rate of from 
0.5 feet per second to about 15.0 feet per second in the area of 
introduction of the reactions is appropriate, with a rate of from about 
1.0 feet per second to about 10.0 feet per second being preferred. A 
circulation rate of from about 2.0 feet per second to about 8.0 feet per 
second is most preferred. 
Preferably, circulation of the liquid medium in chlorinator 3 is achieved 
primarily by gas-lift, although a minor motivating force occurs from 
density differences in leg 4 of chlorinator 3 because of the temperature 
differentials mentioned previously. Gas-lift is provided chiefly by the 
ethylene (and chlorine, if admitted as a vapor) before the ethylene 
bubbles collapse or react. Additional lift may be supplied, if desired, 
provided proper temperature and pressure conditions are employed. More 
particularly, as the ethylene and chlorine bubbles dissolve or react, and 
collapse, the liquid ethylene dichloride formed is passed through a quiet 
zone in which no bubbles (or substantially none) are present. As the 
liquid ethylene dichloride formed, now a part of the circulating medium, 
rises still further in leg 4 of chlorinator 3, the reduction in pressure, 
coupled with appropriate temperature conditions, will cause a portion of 
the liquid medium to vaporize and provide lift. Those skilled in the art 
can readily adjust the height of leg 4 to achieve this additional lift. 
External means of circulation, such as a pump or pumps, may be provided, 
but is not usually necessary. 
Any suitable composition of reaction liquids may be employed, provided the 
circulating medium can be operated under suitable conditions, as outlined 
above, to vaporize a portion thereof, in the zone of reduced pressure. The 
circulating liquid medium will generally comprise a liquid chlorinated 
hydrocarbon of two carbon atoms, such as 1,2-dichloroethane, 
1,1,2-trichloroethane, 1,1,1,2- or 1,1,2,2-tetrachloroethane, and 
pentachloroethane, and mixtures of these materials (hexachloroethane is a 
solid, although often present as an impurity in solution). Normally, one 
of these materials will be present in major amounts, with ethylene 
dichloride or 1,1,2-trichloroethane being preferred. For example, the 
circulating liquid medium may contain from 50 percent to approximately 100 
percent ethylene dichloride, the balance being various proportions of the 
other materials mentioned plus chlorinated hydrocarbon impurities, their 
reaction products, oxygenated impurities, the impurities from the 
oxychlorination effluent, and any materials refluxing from the 
fractionation column. Or the medium may, for example, comprise chiefly 
1,1,2-trichloroethane, e.g., up to 65 percent, the balance being ethylene 
dichloride and/or the other materials mentioned, impurities, etc. 
Returning to FIG. 1, the vaporized chlorinated hydrocarbons from chamber 5 
pass via line 8 to fractionation zone or column 9, wherein the heat 
generated by the reaction between chlorine and ethylene is utilized to 
fractionate the chlorinated hydrocarbons and produce a purified ethylene 
dichloride product. The ethylene dichloride may be taken off as a liquid 
or as a vapor, by techniques known to those skilled in the art, although 
the drawing indicates removal through line 10 as a liquid. Light-ends, 
such as air, HCl, H.sub.2, Cl.sub.2, C.sub.2 H.sub.4, and minor amounts of 
miscellaneous chlorinated hydrocarbons, as well as some ethylene 
dichloride, are removed as overhead from fractionation zone 9 through line 
11, cooled in exchanger 12, and passed through line 13 to 
collector-separator 14. In separator 14 the ethylene dichloride and 
condensible light-ends are largely separated from the other materials, and 
a non-condensable stream containing light-ends is removed to further 
recovery or waste through line 15. A portion or all of the cooled 
condensed materials collected in unit 14 from the light-ends overhead is 
returned to fractionation zone 9 via line 16 to provide reflux, and some 
may be recovered, via line 17, if desirable. Reflux rates in column 9 are 
within the skill of the art, and form no part of the invention. Liquid may 
be returned to chamber 5 (or leg 7) via line 18, and a draw-off line 19 
may be provided for impurity removal. 
Fractionation zone 9 may be supplied also with an ethylene 
dichloride-containing stream through line 20 from another source, such as 
ethylene dichloride pyrolysis zone 21. More particularly, ethylene 
dichloride, e.g., that obtained from product line 10, is 
dehydrochlorinated or "cracked" in zone 21, under conditions and 
procedures known to those skilled in the art, to produce, after 
separation, crude vinyl chloride, hydrogen chloride, and a stream 
containing uncracked ethylene dichloride. The particular process employed 
in "cracking" the ethylene dichloride forms no part of the present 
invention, and any suitable procedure may be employed, as long as a stream 
containing residual or uncreacked ethylene dichloride is characteristic of 
the process. In general, such streams will contain from about 90 mol 
percent to about 99.8 mol percent ethylene dichloride, the balance being 
random amounts of heavier chlorinated hydrocarbons, trichloroethylene, 
1,1-dichloroethane, and other miscellaneous materials. Again, in most such 
processes, the ethylene dichloride-containing stream often contains 
significant minor amounts of chloroprene, for example, from 0.01 mol 
percent to about 0.3 mol percent chloroprene. This chloroprene tends to 
polymerize further along in the process. The ethylene 
dichloride-containing stream may be chlorinated in pipe or line 22, or, as 
shown, in chlorinator 23. The stream is chlorinated under appropriate 
conditions to convert most of the chloroprene and part of the 
trichloroethylene in the stream to heavy-boiling chlorinated compounds. 
Any conventional method of chlorinating the stream may be employed, so 
long as the method chosen does not significantly affect the other desired 
components in the stream or introduce other undesirable impurities. 
More particularly, the stream may be chlorinated, using chlorine as the 
chlorinating agent, at a temperature of from about 0.degree. C. to about 
165.degree. C., preferably at a temperature of from about 0.degree. C. to 
about 120.degree. C. The chlorine may be supplied at mol ratios of from 
about 0.7 mol of chlorine to about 3.0 mols of chlorine per mol of 
chloroprene present. A mol ratio of from about 1.0 mol of chlorine to 
about 2.5 mols of chlorine per mol of chloroprene is preferred. Catalysts 
may be added, although this is not normally necessary. The particular 
catalyst, if chosen, is within the knowledge of the art, and forms no part 
of the present invention. Atmospheric, sub-atmospheric, or super 
atmospheric pressures may be employed. After the chlorination of the 
chloroprene in the stream, the stream is then passed via line 20 to 
fractionation zone 9 wherein the heavy- and light-boiling impurities are 
easily removed. The heat from the reaction of the chlorine and ethylene in 
reactor 3 is sufficient to accomplish the fractionation of this added 
stream, as well as of the vaporized crude ethylene dichloride produced by 
the reaction. If desired, fractionation zone 9 may contain a reboiler (not 
shown) for start-up purposes and flexibility. 
Concomitantly, an impure (or partially purified) and dry ethylene 
dichloride may be introduced from an oxychlorination zone into the 
chlorinator 3 through line 24. More particularly, ethylene, oxygen (e.g., 
as air), and HCl, are contacted in zone 25 in the presence of a catalyst 
under appropriate conditions, known to those skilled in the art, to 
produce an effluent containing, inter alia, ethylene dichloride, HCl, 
ethylene, oxygen, N.sub.2, small amounts of oxygenated compounds, and 
other chlorinated hydrocarbons and materials. The particular 
oxychlorination procedure used is not critical, and any conventional 
oxychlorination process may be employed. For example, the oxychlorination 
procedure used in Belgian Pat. No. 718,777 may be employed. Temperatures 
may range, for example, from about 180.degree. C. to about 400.degree. C., 
a range of from about 200.degree. C. to about 375.degree. C. being 
preferred. Pressures may be atmospheric or greater, and will normally 
range from about 1 atmosphere to about 50 atmospheres. Pressures of from 1 
to about 30 atmospheres are preferred. Those catalysts normally used in 
oxychlorination procedures may be employed, the preferred catalysts being 
those containing copper chloride. 
The effluent from the oxychlorination zone is passed through line 26 to a 
variety of treatment procedures, including cooling or quench zone 27 and 
neutralization zone 29. In cooling zone 27, the oxychlorination effluent 
(e.g., at a temperature of from about 180.degree. C. to about 400.degree. 
C.) is cooled to yield a liquid mixture comprising impure ethylene 
dichloride, water, and HCl. The temperature of the effluent is lowered in 
the cooling zone to a range of from about -40.degree. C. to about 
80.degree. C., and preferably will be from about -25.degree. C. to about 
50.degree. C. After separation of at least the bulk of the water and HCl, 
the crude ethylene dichloride is then passed by line 28 to zone 29 where 
it is contacted with a base, normally an inorganic base, such as an alkali 
metal hydroxide. The basic material neutralizes the residual HCl present 
in the effluent, and reacts with chloral to effect removal thereof. Sodium 
hydroxide, as a dilute caustic solution, is the preferred neutralizing and 
chloral removing agent. The basic material, e.g., NaOH, is preferably 
supplied in the form of a caustic solution containing from 1 percent to 20 
percent by weight caustic, with a solution of from 2 percent to 10 percent 
by weight being preferred. The caustic and water soluble reaction products 
are easily separated from the crude effluent by phase separation. 
The cooled, neutralized effluent is then forwarded by line 30 to a drying 
zone 31, and then preferably to a light-ends removal zone 32, or a 
combination light-ends removal/drying column (not shown) may be employed. 
Where a separate drying zone is employed, the drying may be accomplished 
by fractionation, as indicated, according to well established principles, 
or may be accomplished by drying agents, such as CaCl.sub.2, or molecular 
sieves. In any event, the effluent (crude ethylene dichloride) fed to 
chlorinator 3 should contain quite limited amounts of water, e.g., not 
more than about 10 to 100 parts per million. Although greater amounts may 
be present, corrosion begins to appear in direct relation to the amount of 
water present. Accordingly, as little water as possible should be present 
in the crude ethylene dichloride supplied to the chlorinator 3. If drying 
agents are employed, the light-ends recovery may be eliminated and the 
light-ends are recovered, as will be apparent, in column 9. 
The preferably neutral, dried, and partially purified oxychlorination 
effluent is forwarded from zone 32 via line 24 to chlorinator 3. The 
effluent is preferably introduced as a liquid into chlorinator 3, although 
it may be admitted as a vapor, if desired. The temperature and pressure 
will depend on a variety of factors, such as the temperature and pressure 
of column 32. If desired, the partially purified effluent may be 
heat-exchanged before introduction into chlorinator 3. The temperature of 
the effluent introduced will preferably be from about 85.degree. C. to 
about 130.degree. C., although, as indicated wide variations may be 
employed. In chlorinator 3 the ethylene dichloride in the oxychlorination 
effluent may form a part of the circulating medium or may be vaporized by 
the heat of reaction of the chlorine and ethylene and passed together with 
the impure ethylene dichloride obtained from the chlorination reaction to 
fractionation zone 9. As indicated, product ethylene dichloride, including 
the now fractionated oxychlorination effluent ethylene dichloride, may be 
removed through line 10. High-boiling impurities from the direct 
chlorination reaction, as well as those from the ethylene 
dichloride-containing stream from the ethylene dichloride pyrolysis zone 
and the impure oxychlorinatiion effluent, are removed from the bottom of 
chlorinator 3 through line 33. As indicated previously, a portion of the 
high-boiling impurities may be removed by line 19 from the liquid stream 
exiting the bottom of column 9. 
Although preferred, the oxychlorination effluent need not be sent to 
chlorinator 3. For example, a portion (or all) may be sent to 
fractionation column 9. However, problems associated with 
trichloroethylene buildup will tend to occur in proportion to the amount 
sent to the column. The oxychlorination effluent may contain added crude 
ethylene dichloride from other sources in minor amounts, e.g., up to 10 
mol percent and even 20 mol percent. For example, minor amounts of crude 
ethylene dichloride from other sources may be added to the oxychlorination 
effluent in or prior to the caustic treatment step. 
FIG. 2 illustrates another type of apparatus which may be employed in the 
process of the invention. Ethylene and chlorine are introduced by lines 1 
and 2 into chlorinator 3 near the entrance of draft tube 4. Chlorinator 3 
contains a circulating liquid medium, as described, and a catalyst such as 
ferric chloride. The ethylene and chlorine provide gas lift for the 
liquid, as indicated in the embodiment of FIG. 1. As in the embodiment of 
FIG. 1, the circulating medium is maintained at circulation rates which 
will achieve substantial solution or reaction of the chlorine and 
ethylene, and also achieve rapid distribution of the heat of reaction so 
that vaporization of the ethylene dichloride formed does not occur under 
the pressure and temperature conditions employed. 
As the ethylene and chlorine dissolve or react in the liquid circulating 
medium, the liquid ethylene dichloride formed passes from the reaction 
zone near the lower end of draft tube 4 and up the tube to a zone of 
reduced pressure, normally close to the top or just above draft tube 4. 
Pressure differential considerations are similar to those of the 
embodiment of FIG. 1. The overall pressure and temperature of the system 
are maintained at appropriate levels so that at least a portion of the 
circulating medium, now including the ethylene dichloride formed, 
vaporizes in this zone of reduced pressure. The remainder of the 
circulating liquid medium returns to the reaction zone via the path 
indicated by the arrows. Elements 8, 9, 10, 11, 16, 18, 19, 20, 24 and 33, 
correspond to those described in FIG. 1. 
FIG. 3 illustrates another type of design which may be employed. In this 
unit, fractionation column 9 is closely associated with chlorinator 3. Leg 
5 is provided as shown so that chamber 6 and column 9 are integrally 
connected and mounted to the side of chlorinator 3. Other numerals in the 
figure indicate elements corresponding to those described previously. 
Although three types of apparatus have been described, the invention is not 
limited to those illustrated. Any suitable apparatus which can provide the 
necessary circulating requirements and two zones of pressure can be 
employed. For example, concentric tubes or a baffled tank can be employed. 
Nor is it necessary that chlorinator 3 comprise an integral unit; the 
zones of increased pressure and decreased pressure may be different units 
provided the circulatory requirements and other limitations, as set forth 
herein, are met. 
In order to describe the invention with greater specificity, the following 
non-limiting examples are given. 
EXAMPLE I 
Gaseous chloride and ethylene are introduced at rates of 1690 pounds per 
square foot per hour and 671 pounds per square foot of cross section per 
hour, respectively, into the reaction system of FIG. 1. The superficial 
velocity of each of the gases is about 1.17 feet per second. The 
circulating liquid medium contains about 40 percent, by weight, 
1,1,2-trichloroethane, about 50 percent, by weight, 1,2-dichloroethane, 
about 8 percent tetrachloroethane, and about 2 percent pentachloroethane. 
The medium also contains a catalyst of FeCl.sub.3, in the amount of about 
5000 parts per million. The temperature of the circulating liquid medium 
in the reaction zone is about 130.7.degree. C., and the superficial 
velocity of the circulating medium at the point of introduction of the 
reactants is about 3.5 feet per second. The pressure in the area of entry 
of the reactants is about 30 pounds per square inch (gauge). 
At the top of leg 4, the temperature is about 127.5.degree. C., and the 
pressure is about 20 pounds per square inch (gauge). The reduction in 
pressure, at this temperature level, allows a portion of the olefin 
dichloride medium to flash, particularly in chamber 5. The vapors enter 
column 9, and are fractionated to produce ethylene dichloride of high 
purity in line 10. Light-ends are recovered in collector 14, and a portion 
are returned to column 9 for reflux. An internal reflux ratio of 1.0 is 
maintained in column 9 above the product line 10, and 0.75 below line 10. 
The unvaporized portion of the circulating liquid medium in chamber 5, 
together with reflux from column 9, is returned to the reaction zone via 
leg 7 at a rate of about 3.5 feet per second. 
EXAMPLE II 
Chlorine and ethylene are introduced by lines 1 and 2 into the reaction 
system of FIG. 2 at rates of 4907 pounds per square foot per hour and 1951 
pounds per square foot per hour, respectively. The superficial entry 
velocity of each of the gases is about 3.4 feet per second. The 
composition of the circulating liquid medium approximates that of the 
medium in Example I. The medium also contains about 1000 parts per million 
FeCl.sub.3. The temperature of the circulating liquid medium in the 
reaction zone is about 132.5.degree. C., and the superficial velocity of 
the medium at the point of introduction of the reactants is about 6.5 feet 
per second. The pressure in the reaction zone, i.e., near the bottom of 
draft tube 4, is about 30 pounds per square inch (gauge). 
At the top of draft tube 4, the temperature of the medium is about 
127.5.degree. C., and the pressure is about 20 pounds per square inch 
(gauge). As in Example I, a portion of the circulating liquid medium 
vaporizes, and the vapors are treated in column 9. The unvaporized portion 
of the circulating liquid medium, together with reflux from column 9, is 
returned to the reaction zone on the outside of draft tube 4 at a rate of 
about 4.5 feet per second. 
EXAMPLE III 
The procedure of Example I is repeated, except that a recycle stream from 
an ethylene dichloride pyrolysis unit is supplied to column 9 in addition 
to the vapors from chlorinator 3. An internal reflux ratio of 1.31 is 
maintained near the point of addition of the recycle stream. Product 
ethylene dichloride is removed in line 10. 
EXAMPLE IV 
The procedure of Example I is approximated utilizing the apparatus of FIG. 
3. The circulating medium contains about 60 percent 1,1,2-trichloroethane, 
about 35 percent 1,2-dichloroethane, and about 5 percent combined of 
tetrachloroethane and pentachloroethane. FeCl.sub.3 concentration is 
maintained at about 250 P.P.M. Circulation rates and pressures are similar 
to those of Example I.