Catalyst system and use for the preparation of 1,2-dichloroethane

A catalyst system for the preparation of 1,2-dichloroethane by reacting ethylene and chlorine in a solvent, if desired, in the presence of an inhibitor for reducing the formation of byproducts. The catalyst system comprises a phenolate/chlorine complex. The invention also relates to a process for the chlorination of ethylene using indicated catalyst system.

BACKGROUND OF THE INVENTION 
1) Field of the Invention 
The invention relates to a catalyst system for the preparation of 
1,2-dichloroethane by reacting ethylene and chlorine, if desired in the 
presence of an inhibitor for reducing the formation of by-products, and to 
a process for the preparation of 1,2-dichloroethane using this catalyst 
system. 
2) Description of the Related Art 
The preparation of 1,2-dichloroethane (EDC) by reacting ethylene with 
chlorine in 1,2-dichloroethane as the solvent and reaction medium is 
known. The catalysts used to accelerate the addition reaction of chlorine 
with the ethylene molecule are, besides the chlorides of elements of main 
groups 3 to 6 and subgroups 1,4 and 6 of the Periodic Table, in particular 
anhydrous iron (III) chloride, since the latter is readily accessible and 
inexpensive (CA-A 689991, DE-C 640827 and DE-B 1768367). The principal 
by-products produced in this reaction are ethyl chloride, from the 
competing hydrochlorination of ethylene, and, with evolution of hydrogen 
chloride, 1,1,2-trichloroethane as a consequence of ethylene-induced 
substitution of the EDC formed. 
the chlorination of ethylene is frequently also carried out in the presence 
of oxygen as a substitution inhibitor (US-A 2601322 and DE-A 1568583). 
The addition reaction of chlorine with ethylene is carried out in industry 
both at reaction temperatures around the atmospheric boiling point of EDC, 
the heat of reaction liberated being utilized to distill off and purify by 
rectification the reaction product and possibly also crude EDC from other 
origins, and at lower temperatures of from 30.degree. to 60.degree. C., as 
described in Ullmanns Encyclopadie der technischen Chemie [Ullmann's 
Encylclopaedia of Industrial Chemistry], Volume 9, page 427 (1975). In the 
latter case, however, the temperature level of the reaction is kept so low 
that the reaction enthalpy liberated cannot conveniently be utilized, but 
instead must be dissipated into the cooling water or into the air by 
circulating the reaction medium by pumping via a heat exchanger (DE-A 
1905517). 
The crude, catalyst-containing EDC prepared at lower temperatures is 
usually discharged from the reactor in liquid form and must be washed with 
acidulated water to remove the catalyst and subsequently with aqueous 
alkali metal hydroxide solutions in order to neutralize the crude product. 
The phases are separated by decanting and separating off the aqueous 
layer, and the water-saturated crude EDC which remains is subsequently 
worked up in a known manner by distillation; however, this is complex. 
In DE-A 2427045, ethylene is chlorinated at temperatures of from 
100.degree. to 130.degree. C. and appropriately high pressures in order to 
be able to carry out the reaction in the liquid phase, in the presence of 
iron(III) chloride as catalyst. The product is then fed, with the 
circulating reaction medium, to a zone under lower pressure, in which the 
crude EDC formed is evaporated by the heat of reaction liberated during 
the reaction of chlorine with ethylene and is rectified with recycling of 
high-boiling impurities into the reaction zone. The result is an 
accumulation of high-boiling compound sin the reaction circuit. Although 
this accumulation can be kept within the desired limits by batchwise 
removal of a liquid catalyst-containing circulation product from the 
bottom of the reactor, it is, however, necessary to occasionally add 
iron(III) chloride to the reaction medium in appropriate amounts in order 
to prevent catalyst depletion. In addition, disposal of the discharge from 
the reactor bottom presents difficulties. Moreover, the use of iron(III) 
chloride as catalyst at elevated reaction temperatures is also associated 
with certain disadvantages. Firstly, iron(III) chloride promotes, at 
increasing temperature, the decomposition of the formed EDC with 
deposition of tar-like, amorphous and carbon-rich deposits (J. Soc. Chem. 
Ind. 69 (1950) page 289), which causes increased formation of byproducts 
with increasing temperature and, in particular, a considerable decrease in 
the ethylene yield. Secondly, iron(III) chloride has a corrosive effect in 
the presence of traces of water on the materials usually used in reactor 
and apparatus construction, which very generally causes an 
overproportional increase in the rate of corrosive attack with increasing 
temperature. 
The corrosive behavior of iron(III) chloride is further increased by 
hydrogen chloride, which is virtually always present due to undesired side 
reactions, since the highly corrosive hydrogen tetrachloroferrate complex, 
which very easily releases aggressive protons, is thereby formed. For this 
reason, attempts have been made to carry out the reaction between ethylene 
and chlorine completely and selectively in the absence of metal salt 
catalysts by adding organic catalysts, such as, for example, 
hydroxyl-containing aromatic compounds (DE-B 1902843). However, this only 
succeeds for a short time, since, in particular at elevated temperatures, 
chlorination of the aromatic ring occurs with time and, on the other hand, 
the catalystic effectiveness of organic catalysts of this type drops 
drastically with increasing degree of chlorination. 
The process of EP-A 82342 (iron(III) chloride catalyst in the presence of 
nitrogen bases, such as ammonia, amines or salts of these bases) or of 
EP-A 111203 (alkali metal or alkaline earth metal tetrachloroferrate 
catalysts) can be used to considerably reduce, in particular in the medium 
temperature range form 90.degree. to 120.degree. C., the corrosion in 
reactors made of conventional metallic materials which is caused by 
iron(III) chloride as catalyst in the preparation of EDC, if the iron(III) 
chloride catalyst is charged with the additives mentioned therein. In 
addition, these additives also have an advantageous effect on the 
formation of byproducts, which are thereby reduced in amount. However, at 
elevated reaction temperatures, which are unavoidable for economical 
utilization of the reaction enthalpy liberated during the chlorination of 
ethylene, these corrosion-inhibiting and reaction selectivity-promoting 
effects are considerably diminished since the ammonium or alkali metal or 
alkaline earth metal tetrachloroferrates which form on addition of 
ammonium chloride or organic amine hydrochlorides or alkali metal or 
alkaline earth metal chlorides to iron(III) chloride, are thermally labile 
and decompose more and more with increasing temperature to form the 
starting components, from which in turn extremely corrosive hydrogen 
tetrachloroferrate is produced to an increasing extent in addition to the 
virtually inert ammonium alkali metal or alkaline earth metal chlorides, 
which are now present and isolated as separate species. In the case of 
ammonium or amine hydrotetrachloroferrate complexes, this is supplemented 
by the fact that the ammonium ions are Bronsted acids, which eliminate 
highly corrosive protons with increasing temperature with formation of 
amine bases. 
EP-A 113287 discloses a process in which about 85% of the heat of reaction 
liberated during the chlorination of ethylene in the presence of iron(III) 
chloride at temperature of from 140.degree. to 180.degree. C. can be 
utilized to generate steam. In this process, the EDC leaving the reaction 
zone is cooled by heat exchange with water before further work-up or 
recycling into the reaction zone. Apart from the negative corrosion 
behavior of bare iron(III) chloride, many byproducts are also produced. 
However, it is certainly the more correct way industrially to utilize the 
reaction enthalpy liberated to generate steam or to heat a heat-transfer 
medium, since this is more flexible and optimum recovery of the reaction 
enthalpy from the chlorination of ethylene can be achieved, even in the 
case of "unbalanced" conditions which occur during daily events or in 
general. 
In the process of EP-A 75742, the reaction mixture form the chlorination of 
ethylene is divided into two sub-streams, or which one is passed through a 
heat exchanger and then returns into the circuit, while the second 
sub-stream is depressurized and fed to a rectification column, which is 
heated via said heat exchanger. In this procedure, there is none of the 
flexibility just discussed, so that deviations from the "balanced 
process", due to the lack of sufficient heat of reaction to be liberated 
or due to production of EDC in excess of that from the "balanced process" 
mean that the high-boiling component column integrated into the reaction 
system must additionally be heated with steam or, in the reverse case, 
excess reaction enthalpy must be passed into the cooling water or into the 
air via a trim cooler. Deviations from the "balanced process" thus occur, 
for example, if, due to a temporary lack of chlorine, the chlorination of 
ethylene must be reduced or if, due to an oversupply of external hydrogen 
chloride, the oxychlorination of ethylene is enhanced or, in the normal 
direct chlorination procedure, the oxychlorination alternatively operates 
at a lower rate due to reduced production of vinyl chloride monomer. 
The object was therefore to develop a catalyst system for the preparation 
of 1,2-dichloroethane which ensures the highest possible selectivity and 
yield in all industrially important temperature ranges, i.e. from 
0.degree. C. to 300.degree. C., in the chlorination of ethylene, and a 
minimum of corrosion. 
A further object was to convert this catalyst system to a simple and 
economical process for the preparation of EDC by chlorinating ethylene, 
which process makes it possible, depending on the local conditions, either 
to sue at least some of the reaction enthalpy liberated for isolating pure 
EDC of cracking quality or to utilize virtually all the reaction enthalpy 
liberated to generate steam at an industrially useful pressure level; the 
catalyst system should remain in the reaction medium, and the EDC formed 
need only be freed from small amounts of high-boiling impurities before 
being used in a pyrolysis furnace. 
SUMMARY OF THE INVENTION 
The invention relates to a catalyst system for the preparation of 
1,2-dichlorethane by reacting ethylene and chlorine in a solvent, if 
desired in the presence of an inhibitor for reducing the formation of 
by-products, the catalyst system comprising a phenolate/chlorine complex 
of the formula 
EQU Me.sup.+n [Z.sup.+m Cl.sub.m.L]n 
in which 
n is an integer from 1 to 3, 
m is an integer from 1 to 6, 
Cl is a chloride anion, 
Me.sup.30 is a hydrogen proton and/or a metal cation of elements from the 
1st and/or 2nd main group or of the lanthanide group of the Periodic Table 
of the Elements (PTE), 
Z.sup.+ is a metal cation of elements of the 3rd, 4th, 5th or 6th main 
group or of the 1st, 4th, 6th or 8th sub-group of the PTE, and 
L is a phenolate anion of the formula: 
##STR1## 
in which X denotes 0 to 4 chlorine atoms, and 
R is a hydrogen atom and/or a hydroxyl group and/or a halogen and/or a 
linear or branched alkyl or chloroalkyl group having from 1 to 6 C atoms 
and/or an alkoxy or chloroalkoxy group having 1 to 6 C atoms in a linear 
or branched arrangement.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The catalyst system according to the invention is prepared by mixing the 
component Me.sup.+n Cl.sub.n, i.e., hydrogen chloride gas and/or alkali 
metal chlorides and/or alkaline earth metal chlorides, or chlorides of the 
lanthanides with components Z.sup.+m Cl.sub.m, i.e., with metal chlorides 
of elements of the 3rd,4th,5th, or 6th main group or of the 1st,4th,6th or 
8the sub-group of the Period Table of the Elements, and with the phenolic 
compounds of the above-described general formulae. 
The admixing is carried out in each case in virtually equimolar amounts of 
Z.sup.+m Cl.sub.m and the phenolic compound to each another, with a 
scattering range of in each case from 0.9 to 1.1:1 equivalent proportions, 
as a solution or suspension, preferably in 1,2-dichloroethane. The 
equivalence between Me.sup.+n Cl.sub.n and the phenolic compound may also 
have a scattering range of in each case from 0.5 to 1.5:1, but the 
scattering range is preferably likewise from 0.9 to 1.1:1. 
The preparation of catalysts Me.sup.+n [Z.sup.+m Cl.sub.m.L].sub.n 
according to the invention from the mixture of Z.sup.+m Cl.sub.m, 
Me.sup.+n Cl.sub.n and the phenolic compound may be carried out in a 
separate reaction step by mixing and, if necessary, heating the mixture 
under reflux for several hours, or in situ, in the reaction zone of the 
ethylene chlorination reactor, after addition of the mixture to the 
reaction medium. 
In the case of chlorinated phenolic ligands, the benzene ring chlorination 
can take place separately in the EDC solution before mixing with the other 
constituents of the catalyst system or in a separate catalyst batch mixer. 
The benzene ring chlorination is preferably carried out in situ in the 
reaction zone of the ethylene chlorination reactor after addition of the 
mixture of the individual catalyst components. 
Preferred alkali metal and alkaline earth metal chlorides are sodium 
chloride and calcium chloride. The preferred lanthanide is cerium(III) 
chloride. The metal chlorides providing the central atom Z of the 
phenolate/chlorine complex are preferably aluminum chloride, tin(IV) 
chloride, bismuth(III) chloride, tellurium(IV) chloride, gold(III) 
chloride, titanium(IV) chloride, tungsten(VI) chloride, thallium(I) 
chloride and iron(III) chloride. Particular preference is given to 
iron(III) chloride. Particularly suitable phenolic compounds are phenol; 
ortho-, meta- and para-cresol; ortho-, meta- and para-chlorophenol; 
2-sec-butylphenol, pyrocatechol, resorcinol, hydroquinone, guajacol, 
pyrogallol, oxyhydroquinone, phloroglucine and 
3,5-di-tert-butylhydroquinone. 
Particularly preferred catalyst are hydrogen meta-cresolate 
trichloroferrate, sodium ortho-cresolate trichloroferrate, calcium 
bis-para-cresolate trichloroaluminate and cerium tris-ortho-cresolate 
trichloroaluminate which, if desired, may be mono- or poly-chlorinated on 
the benzene ring. 
The invention furthermore relates to a process for the preparation of 
1,2-dichloroethane by reacting ethylene with chlorine, in a reaction zone 
which contains a circulating liquid medium comprising chlorinated 
hydrocarbons having 2 carbon atoms, at a temperature below the evaporation 
temperature of the medium, at the pressure prevailing in the reaction 
zone, if desired in the presence of oxygen as an inhibitor for preventing 
side reactions, wherein 
a) the concentration of the catalyst system Me.sup.+n [Z.sup.+m 
Cl.sub.m.L].sub.n, dissolved or suspended in the reaction medium is, 
calculated as Z.sup.+m Cl.sub.m, from 0.01 to 1.0% by weight, based on the 
amount of reaction medium, and the catalyst system is circulated with 
replenishment of the consumed ethylene and chlorine, where, 
b) at reaction temperatures of from 0.degree. to 300.degree. C. and at 
pressures which prevent the reaction medium boiling in the reaction space, 
with utilization of all or some of the reaction enthalpy liberated during 
the chlorination of ethylene to generate 1,2-dichloroethane vapor, 
vaporized 1,2-dichloroethane is removed from the reaction zone into a zone 
of lower pressure, and these vapors are introduced into the bottom of a 
rectification column, and, 
c) at reaction temperatures of from 0.degree. C. to 120.degree. C., the 
vapors at the head of the column are condensed by cooling with water or 
air, at reaction temperatures of from 120.degree. to 300.degree. C., the 
heat of condensation of the vapors is utilized by heat exchange of the 
vapors from the rectification column with a heat-exchange medium, and, 
d) while maintaining a minimum reflux ratio, expressed as the ratio by 
weight of the reflux to the product generated, of 2:1 parts by weight in 
the low-temperature procedure and of 1:1 parts by weight in the 
high-temperature procedure, the condensed vapors are fed back into the 
reaction space after more or less considerable cooling in the 
low-temperature procedure, but after cooling by a maximum of 5.degree. C. 
in the high-temperature procedure, based on the boiling or condensation 
temperature, and 
e) the 1,2-dichloroethane produced is removed in liquid form from the 
bottom of the rectification column. 
Suitable reactors for the chlorination of ethylene are loop reactors, as 
described, for example, in DE-A 2427045, or loop reactors as described 
DE-B 1768367 or in the enclosed FIG. 1, or tower reactors as described in 
the enclosed FIG. 2. The chlorination is carried out in a circulating 
liquid medium comprising chlorinated hydrocarbons having 2 carbon atoms. 
The reaction medium preferably employed is 1,2-dichloroethane. The speed 
of the circulated reaction medium is preferably between 0.1 and 5 m/s. The 
circulation of the liquid reaction medium in the reactor can be effected, 
for example, by means of a pump and/or by the thermosiphon or air-lift 
pump principle. 
The reactor is charged with ethylene and chlorine, molar ratio between 
ethylene and chlorine preferably being between 1:1 and 1.005:1. The gas 
flow rate in the reaction space is preferably form 0.01 to 1 m/s, based on 
the ethylene gas stream. 
The concentration of the catalyst system Me.sup.+n [Z.sup.+m 
Cl.sub.m.L].sub.n dissolved or suspended in the reaction medium is between 
0.01 and 1.0% by weight, preferably 0.2 to 0.7% by weight, which is based 
in each case on the amounts of reaction medium and calculated as Z.sup.+m 
Cl.sub.m. In a preferred embodiment, the catalyst system in the form of 
the individual components is dissolved or suspended in the reaction 
medium, the individual components preferably being employed in a molar 
ratio of from 0.9 to 1.1:1 to one another. 
Particularly preferred catalysts are hydrogen meta-cresolate 
trichloroferrate, sodium ortho-cresolate trichloroferrate, calcium 
bis-para-cresolate trichloroaluminate and cerium tris-ortho-cresolate 
trichloroaluminate, which may, if desired, be mono- or polychlorinated on 
the benzene ring. 
In particular, sodium ortho-cresolate trichloroferrate, preferably in a 
concentration of form 0.3 to 0.5% by weight, based on the reaction medium, 
is employed as the catalyst system. It is preferably formed in situ, after 
addition of an equimolar mixture, in said equivalence range, or NaCl, 
FeCl.sub.3 and o-cresol to the reaction medium. 
The catalyst system is circulated with the reaction medium with 
replenishment of the consumed ethylene and chlorine. 
In order to suppress side reactions, oxygen or air may be employed, if 
desired, as an inhibitor. The concentration is from 0.01 to 10% by volume, 
preferably from 0.8 to 1.5% by volume, in each case calculated as oxygen 
and based on the amount of chlorine gas. 
The mean residence time of the reactant mixture is from 0.2 to 2 minutes, 
based on the empty reaction, mixing and circulation space under standard 
conditions (0.degree. C. 1013 mbar). The reaction time of the reactants in 
the reaction space is preferably between 1.5 and 60 seconds. 
The chlorination reaction is carried out at reaction temperatures between 
0.degree. and 300.degree. C. and at pressures which prevent the reaction 
medium boiling in the reaction space. In the case of the low-temperature 
procedure, the reaction temperature is from 0.degree. to 120.degree. C., 
preferably from 40.degree. to 80.degree. C., and the pressure in the 
reaction space ire preferably between 1 and 5 bar absolute. In the 
high-temperature procedure, the reaction temperature is form 120.degree. 
to 300.degree. C., preferably from 140.degree. to 170.degree. C., and the 
pressure in the reaction space is preferably between 5 and 10 bar 
absolute. 
The 1,2-dichloroethane is removed from the reaction zone into a zone or 
lower pressure, and the resultant vapors are introduced into a 
rectification column. The rectification column is preferably a packed 
column or a tray column. The number of theoretical trays is preferably 
between 1 and 5. 
In the low-temperature ethylene chlorination procedure, the vapors at the 
head of the rectification column are condensed in a condenser by indirect 
heat exchange with water or air. The pressure at the column head is 
preferably from 0.2 to 0.9 bar abs. 
Some of the condensate is introduced into the rectification column as 
liquid reflux, and the remainder is fed to the circulated reaction medium 
after more or less considerable cooling, preferably at a temperature of 
from about 5.degree. to 50.degree. C. below the boiling temperature, and 
fed back into the reaction space. In the low-temperature procedure, the 
minimum reflux ratio, expressed as the ratio by weight between the reflux 
and the product generated, is preferably 2:1 parts by weight. The 
noncondensable components of the product from the head of the 
rectification column are discharged into the atmosphere or fed to a 
combustion plant. 
The 1,2-dichloroethane produced is removed from the bottom of the 
rectification column. The residual heat of reaction can be dissipated into 
the cooling water or into the air via a heat exchanger in the circuit. 
In the high-temperature ethylene chlorination procedure, the vapors at the 
head of the rectification column are condensed in a heat exchanger. The 
pressure at the column head is preferably from 4.5 to 8.3 bar abs. 
Feasible heat-exchange media are any heat carriers, for example mineral 
oils, which release the adsorbed heat elsewhere and, accordingly cooled, 
are fed back to the heat exchanger. The heat of condensation of the vapors 
is preferably utilized to generate saturated steam at a pressure of from 
2.25 to 6.0 bar abs., by heat exchange of the vapors from the 
rectification column with hot water of appropriate pressure. 
Some of the condensate is introduced into the rectification column as 
liquid reflux, and the remainder is fed to the circulated reaction medium 
and fed back into the reaction space; the temperature of the vapor 
condensate fed back into the reaction space should be cooled by a maximum 
of 5.degree. C., based on the boiling or condensation temperature. In the 
high-temperature procedure, the minimum reflux ratio, expressed as the 
ratio by weight of reflux to generated product, is preferably 1:1 parts by 
weight. The non-condensable components of the product from the head of the 
rectification column are discharged into the atmosphere or fed to a 
combustion plant. The 1,2-dichloroethane produced is removed from the 
bottom of the rectification column. 
By means of the process according to the invention, the reaction enthalpy 
liberated during the chlorination of ethylene can, in the low-temperature 
procedure, be utilized to the extend of at least 40% in the generation of 
the vapor-form 1,2-dichloroethane by depressurizing the reaction product 
from the chlorination of ethylene. 
In the high-temperature procedure according to the invention, it is 
possible to recover all the reaction enthalpy liberated during the 
chlorination of ethylene. All the heat of reaction is utilized to generate 
vaporized 1,2-dichloroethane by depressurizing the reaction product and 
can be recovered as heat of condensation of the vapors by heat exchange. 
The process according to the invention and an apparatus for the 
chlorination of ethylene by the low-temperature procedure are represented 
by way of example in FIG. 1 and Example 5. FIG. 2 and Example 6 describe 
the process according to the invention and an apparatus for the 
high-temperature procedure by way of example. 
Compared with the procedures known from the prior art, the process 
according to the invention offers a number of advantages: 
The removal of the reaction product from the reaction space in vapor form 
means that it is not necessary to top up the catalyst or remove the 
catalyst from the crude product. This is also the reason for the omission 
of the environmentally appropriate pretreatment of the washing water 
contaminated by EDC (for example removal of chlorohydrcarbon by steam 
stripping). The process gives high yields and extremely low formation of 
byproducts (high selectivity). Since the catalyst system according to the 
invention is virtually noncorrosive, meaning that exotic materials are not 
necessary and, in addition, the reaction apparatus is relatively simple 
and non-extensive, the apparatus costs are low, even for the 
high-temperature procedure. Since the EDC produced in the low-temperature 
procedure is already of cracking quality without additional purification 
steps, energy can be saved for the distillative purification of the EDC 
produced. The reaction enthalpy of the chlorination of ethylene can be 
recovered virtually quantitatively, in the form of saturated steam having 
a technically and economically interesting steam tension; in the 
high-temperature procedure with additionally reduced energy consumption 
for the distillative purification of the EDC produced, since the latter is 
free from low-boiling constituents. The procedure according to the 
invention gives the greatest possible flexibility between direct 
chlorination and oxychlorination of ethylene, corresponding to the 
boundary conditions prevailing in each case, with optimum energy 
utilization or energy saving in the process of the preparation of vinyl 
chloride. 
Surprisingly, it has also become apparent that the catalyst system 
according to the invention is clearly superior to all the catalyst 
mixtures known hitherto for the direct chlorination of ethylene, both with 
respect to selectivity and with respect to corrosion behavior, this 
superiority becoming very clearly apparent, in particular, at elevated 
reaction temperatures. Thus, even in the high-temperature procedure, 
virtually no ethyl chloride is formed, and also significantly less 
1,1,2-trichloroethane is formed than, for example, in DE-A 3148450 and 
European Patent 111203. Due to the fact that the catalyst system according 
to the invention is substantially less corrosive, both in the 
low-temperature and high-temperature procedures, than comparable catalyst 
mixtures of the prior art, it can be seen that the catalyst system 
according to the invention must, surprisingly, be very thermally stable. 
The examples below serve to further illustrate the invention: 
EXAMPLE 1 
Corrosion experiments were carried out at 84.degree. C. (boiling point of 
EDC) and at 212.degree. C. (boiling point of hexachlorobutadiene) using 
various catalyst mixtures. To this end, V4A stainless-steel plates 
measuring 40.times.20.times.2 mm were in each case immersed in liquid EDC 
or hexachlorobutadiene. The liquid in each case contained 5000 ppm by 
weight of iron(III) chloride or an equimolar mixture of ammonium chloride 
and iron(III) chloride or an equimolar mixture of sodium chloride and 
iron(III) chloride or an equimolar mixture of ortho-cresol and iron(III) 
chloride or an equimolar mixture of sodium chloride, ortho-cresol and 
iron(III) chloride, in each case in a concentration of 5000 ppm by weight, 
calculated as iron(III) chloride, in dissolved or suspended form. After 
refluxing for 24 hours in each case whilst simultaneously passing dry 
hydrogen chloride gas into the mixture, the corrosion rates were 
determined gravimetrically by differential weighing of the plates. The 
results are shown in Table 1. 
TABLE 1 
______________________________________ 
Weight loss in mg/mm.sup.2.a 
Catalyst system at 84.degree. C. 
at 212.degree. C. 
______________________________________ 
FeCl.sub.3 or HFeCl.sub.4 
0.123 19.630 
NH.sub.4 FeCl.sub.4 
0.062 9.985 
NaFeCl.sub.4 0.055 8.835 
H--FeCl.sub.3.o-cresolate 
0.034 2.803 
Na--FeCl.sub.3.o-cresolate 
0.025 2.020 
______________________________________ 
The results illustrate the superiority of the catalyst system according to 
the invention over the prior art with respect to corrosion behavior. Thus 
a corrosion rate of 2 mg/mm.sup.2 .multidot.a, corresponds, for example, 
approximately to a corrosion rate of 0.25 mm/a. A corrosion rate of &lt;1 
mm/a generally means that there are no material problems with respect to 
service life. By contrast, the catalyst systems ammonium 
tetracholoroferrate and sodium tetrachloroferrate give corrosion rates at 
212.degree. C. of&gt;1 mm/a, which means that material problems exist here 
with respect to service life. These results are all the more surprising if 
the catalyst complex H-FeCl.sub.3 o-cresolate is considered separately. It 
would be known to any person skilled in the art that protonolysis of this 
complex, and thus the corrosion rate, increases with the temperature. 
However, the opposite occurred, which clearly supports the experimental 
results. 
EXAMPLE 2 
Preparation of the catalyst system NaFeCl.sub.3 o-cresolate 
5 g (31 mmol) of anhydrous iron(III) chloride were dissolved or suspended 
in 500 cm.sup.3 of EDC in a glass flask, and 1.8 g (31 mmol) of sodium 
chloride and 3.3 g (31 mmol) of o-cresol were added. The mixture was then 
refluxed. The hydrogen chloride which formed was removed by means of a 
gentle stream of nitrogen passed through the flask, and was absorbed in 
water. After 15 hours, 0.7 l of hydrogen chloride had been liberated, 
determined by titration of the washing water, i.e. the complex 
##STR2## 
had been formed. 
Chlorine gas was subsequently passed in at around 50.degree. to 60.degree. 
C. until the evolution of hydrogen chloride ceased. 3 l of hydrogen 
chloride were liberated, i.e. the benzene ring chlorination of the complex 
was complete: 
##STR3## 
EXAMPLE 3 
The vertical glass reaction tower (internal diameter 50 mm, height 300 mm) 
was packed with 2-mm Raschig rings and surrounded by a twin jacket in 
which thermostatic water was circulated at a temperature of 84.degree. C. 
This additional heating was necessary, in spite of the exothermic reaction 
between chlorine and ethylene, to cover the heat loss due to radiation 
(unfavorable ratio between surface area and heat liberation), so that EDC 
was distilled off form the reactor. Reaction liquid at a rate of 0.6 cm/s 
in an amount of 40 l hr was circulated by means of a metering pump through 
the reactor packed with glass Raschig rings. 40 l (S.T.P.)/hr of chlorine 
and 250 cm.sup.3 (S.T.P.)/h of oxygen were passed into the circulating 
reaction medium and 40.2 l (S.T.P.)/hr of ethylene were blown into the 
reactor from below via a glass frit located in the reaction tower. 
The reactor was in each case charged with 500 cm.sup.3 of EDC containing 
various catalyst systems, prepared as in Example 2, in dissolved or 
suspended form in a concentration of 0.5% by weight, calculated as the 
metal chloride which forms the central atom of the particular catalyst 
complex. The EDC distilled off was condensed in a water condenser and 
collected. 175 g/hr of EDC produced were diverted off using a condensate 
divider and removed, while excess condensate was fed back into the 
reaction zone. A further portion of EDC was removed from the offgas 
stream--essentially oxygen, excess ethylene and nitrogen, which was fed in 
in an amount of 2 l (S.T.P.)/hr after the condenser for inertization--by 
means of a cold trap. The combined EDC produced was analyzed for purity by 
gas chromatography. The offgas from the cold trap was likewise analyzed 
for low-boiling byproducts by gas chromatography and chlorine. Chlorine 
was not found in any of the experiments, i.e. the conversion was always 
quantitative;. 
The following catalyst systems were investigated: 
A) HFeCl.sub.3 -m-cresolate, prepared by adding equimolar amounts of 
iron(III) chloride and m-cresol 
B) NaFeCl.sub.3 -o-cresolate, prepared by adding equimolar amounts of NaCl, 
FeCl.sub.3 and o-cresol 
C) Ca[FeCl.sub.3 -p-cresolate].sub.2, prepared by adding equivalent amounts 
of CaCl.sub.2 and of the equimolar mixture of FeCl.sub.3 and p-cresol 
D) NaFeCl.sub.4 -phenolate, prepared by adding equimolar amounts of NaCl, 
FeCl.sub.3 and phenol 
E) NaBiCl.sub.3 -resorcinate, prepared by adding equimolar amounts of NaCl, 
BiCl.sub.3 and resorcinol 
F) Ce[AlCl.sub.3 -o-cresolate].sub.3, prepared by adding equivalent amounts 
of CeCl.sub.3 and of the equimolar mixture of AlCl.sub.3 and o-cresol 
G) HFeCl.sub.4, prepared by adding FeCl.sub.3, HCl is produced during the 
reaction 
H) NH.sub.4 FeCl.sub.4, prepared by adding equimolar amounts of NH.sub.4 Cl 
and FeCl.sub.3 
I) KFeCl.sub.4, prepared by adding equimolar amounts of KCl and FeCl.sub.3 
The results are shown in Table 2. The experimental duration was 24 hours in 
each case. 
TABLE 2 
__________________________________________________________________________ 
Reaction medium 
Catalyst 
Distillate 1,1,2-trichloro- 
1,1,2-trichloro- 
system 
Ethyl chloride 
ethane ethane 
__________________________________________________________________________ 
A &lt;1 ppm by weight 
550 ppm by weight 
0.09 % by weight 
B &lt;1 ppm by weight 
290 ppm by weight 
0.06 % by weight 
C &lt;1 ppm by weight 
310 ppm by weight 
0.08 % by weight 
D &lt;1 ppm by weight 
350 ppm by weight 
0.08 % by weight 
E &lt;1 ppm by weight 
380 ppm by weight 
0.075 % by weight 
F &lt;1 ppm by weight 
480 ppm by weight 
0.086 % by weight 
G 650 ppm by weight 
2500 ppm by weight 
0.53 % by weight 
H 18 ppm by weight 
850 ppm by weight 
0.10 % by weight 
I 25 ppm by weight 
1430 ppm by weight 
0.22 % by weight 
__________________________________________________________________________ 
The results of Experiments A to F clearly demonstrate the superiority of 
the catalyst systems according to the invention over the prior art 
(Experiments G to I) with respect to selectivity. In particular, the 
absence of ethyl chloride is important since as is known, it forms 
butadiene on pyrolysis of EDC. 
EXAMPLE 4 
The procedure was analogous to Example 3. The following catalyst systems 
were prepared in situ by mixing in the experimental apparatus, in a 
concentration of in each case 0.4% by weight, calculated as FeCl.sub.3 : 
A) 1 mol of FeCl.sub.3 and 0.9 mol of o-cresol 
B) 1 mol of FeCl.sub.3 and 1.1 mol of o-cresol 
C) 1 mol of FeCl.sub.3 and 0.5 mol of o-cresol 
D) 1 mol of FeCl.sub.3 and 2 mol of o-cresol 
E) 1.5 mol of NaCl, 1 mol of FeCl.sub.3 and 0.9 mol of o-cresol 
F) 0.5 mol of NaCl, 1 mol FeCl.sub.3 and 1.1 mol of o-cresol. 
The results are shown in Table 3. 
TABLE 3 
______________________________________ 
Catalyst Distillate composition 
system Ethyl chloride 1,1,2-trichloroethane 
______________________________________ 
A &lt;1 ppm by weight 530 ppm by weight 
B &lt;1 ppm by weight 560 ppm by weight 
C 480 ppm by weight 2300 ppm by weight 
D 530 ppm by weight 2150 ppm by weight 
E &lt;1 ppm by weight 610 ppm by weight 
F &lt;1 ppm by weight 520 ppm by weight 
______________________________________ 
It can be seen from the results that a molar ratio between FeCl.sub.3 and 
o-cresol with a scattering range of from 0.9 to 1.1:1 is important for the 
selectivity, but the alkali metal chloride or alkaline earth metal 
chloride content is less crucial, even outside the amount equivalence to 
FeCl.sub.3. Nevertheless, the amount equivalence of the alkali metal or 
alkaline earth metal chlorides should be observed if at all possible since 
amounts above the respective equivalence can give considerable erosion 
problems as an inert material. 
EXAMPLE 5 
As shown in FIG. 1, 50 m.sup.3 /hr of EDC were circulated via line 5, the 
empty loop reactor R, the pump tank V and the water condenser K1 with the 
aid of the circulating pump P1. 
The circulation system was charged via line 4 with equimolar amounts of 
FeCl.sub.3, NaCl and o-cresol in a concentration of 0.5% by weight, 
calculated as FeCl.sub.3 and based on the amount of circulating EDC. 
Chlorine was reacted with ethylene at a reactor temperature of 70.degree. 
C. and a pressure of 3 bar absolute by feeding 45.1 m.sup.3 (S.T.P.)/hr of 
ethylene in via line 1, 45 m.sup.3 (S.T.P.)/hr of evaporated liquid 
chlorine via line 2 and 500 l (S.T.P.)/hr of oxygen via line 3. 
The diameter of the reactor was 100 mm and the length of the reaction tube 
was 1,600 mm. Some of the heat of reaction liberated was diverted off to 
generate EDC vapor in the pump tank V, where a pressure of about 0.67 bar 
absolute prevailed, and the remainder of the heat of reaction was 
dissipated into the cooling water in condenser K1 in order to keep the 
reaction temperature in the reactor R constant at 70.degree. C. The 
pressure was kept constant at 3 bar absolute in the reaction part via a 
pressure regulator PC. 250 kg/hr of EDC evaporated at a temperature of 
70.degree. C. via line 6 into the bottom of the rectification column F, 
which was packed to a level of 2000 mm with 1/2 inch ceramic rings. Bottom 
product from the rectification column F flowed, depending on the level in 
the pump tank V, via line 7. The vapors leaving the head of the 
rectification column in an amount of 650 kg/hr flowed via line 8 into the 
condenser K2 and they were condensed. The condensate produced flowed via 
line 9 into the collector S and from there was fed via lines 10 and 11 
with the aid of the pump P2 in an amount of 400 kg/hr kept constant by a 
flow controller FC, to the column F as liquid reflux, while the remainder 
of the distillate (about 51.5 kg/hr) was pumped, depending on the level in 
the collector S, and regulated via line 12, into the circulation system 5. 
In the bottom of the rectification column F, the EDC produced was removed, 
under level control, via line 19 in an amount of 198.5 kg/hr. 
The non-condensable constituents, essentially ethylene, oxygen and 
nitrogen, which was fed in at the gas-outlet connector of the collector S 
(not shown in the drawing), flowed via line 13, kept at a pressure of 0.66 
bar bar absolute by PC, into the liquid ring pump P3, operating with EDC 
as the operating medium and produced the necessary underpressure of about 
0.66 bar, measured in absolute terms, in the gas line 13. The offgas 
escaped at 18 via line 14 into the atmosphere or into a combustion plant. 
Fresh EDC could be introduced via line 20. Consumed EDC, carrying a low 
content of gases, was discharged via line 15 into the water-cooled tank B, 
which was vented to the offgas line 14 via line 17, buffered and released 
into the reaction system under level control via line 16. 
The EDC produced had the following quality: 
______________________________________ 
Ethyl chloride &lt;1 ppm by weight 
1,1,2-Trichloroethane- 
120 ppm by weight 
1,2-Dichloroethane 99.98 ppm by weight 
______________________________________ 
This EDC could be reacted directly, without further purification, in a 
cracking furnace to give vinyl chloride and hydrogen chloride without the 
cracking kinetics or the formation of byproducts and coke being impaired 
in any way, as an operating trial had proved, after prior collection of 
appropriate amounts of this EDC prepared by the process according to the 
invention. Even after a 4-months' trial, there were no quality problems 
for the EDC produced nor loss of catalyst. Neither was accumulation of 
high-boiling components in the reactor circuit observed. 
EXAMPLE 6 
The reactor R as shown in FIG. 2 comprised a vertical, packed tower 
(diameter 200 mm, height 4000 mm). 50 m.sup.3 /hr of EDC were circulated 
by means of the pump P1 via line 23 and the heat exchanger H, which was 
heatable by steam, n order to make the entire apparatus water-free by 
azeotropic distillation with EDC. This circulation stream contained 
dissolved or suspended FeCl.sub.3, NaCl and m-cresol in equimolar amounts 
to one another and in a concentration of 0.5% by weight, calculated as 
FeCl.sub.3.45.2 m.sup.3 (S.T.P.)/hr of ethylene were introduced via line 
1, 45 m.sup.3 (S.T.P.)/hr of chlorine as liquid chlorine via line 2 and 
400 l (S.T.P.)/hr of oxygen via line 27. The reaction between ethylene and 
chlorine was carried out at 165.degree. C. and a pressure of 7.3 bar 
absolute, the heat of reaction liberated being used to generate EDC vapor. 
1345 kg/hr of EDC evaporated at a pressure of about 7.1 bar via line 6 
into the bottom of the rectification column F, which was packed to a level 
of 2000 mm with 1/2 inch ceramic rings. 1545 kg/hr of EDC vapors at a 
temperature of about 162.degree. C. flowed via line 8 into the steam 
generator WT, in which, with condensation of the vapors and with level 
control, boiler feed water at 150.degree. C. fed in via line 29 in an 
amount of 200 kg/hr measured by the flow meter FQ, was accordingly 
converted into saturated steam at a pressure of 4.9 bar absolute, which, 
after phase separation in the steam drum DT under pressure control, was 
released into the steam network via line 32. Nitrogen was introduced at 26 
for inertization purposes. The condensed vapors flowed via line 28 into 
the separator A1, from where they were introduced into the column F as 
liquid reflux via line 24 with the aid of the pump P2, fixed 
value-regulated via FC, and line 25 in an amount of 200 kg/hr or pumped 
into the circulation system under level control via line 22. The 
non-condensable offgas flowed to the condenser K via line 30, and any 
condensate produced was collected in the separator A2 and flowed back to 
the separator A1 via line 31. The offgas was released into the open or fed 
to a combustion plant under pressure control at 7.05 bar absolute at 21. 
The offgas was analyzed for chlorine using the analyzer AR. Bottom product 
from the column F was diverted into the reaction system via line 7, 
regulated by the level in the reaction tower. Chlorine was not found in 
the analyzer AR, i.e. the conversion of chlorine was quantitative. 
198.5 kg/hr of EDC produced were removed via line 19 under level control. 
The EDC produced had the following composition: 
______________________________________ 
Ethyl chloride &lt;1 ppm by weight 
1,1,2-Trichloroethane 
3100 ppm by weight 
1,2-Dichloroethane 99.68 ppm by weight 
______________________________________ 
Due to the relatively high level of 1,1,2-trichloroethane, the crude EDC 
had to be freed from these high-boiling components in a conventional 
manner before being used for thermal cracking to give vinyl chloride and 
hydrogen chloride. 
Even after an experimental duration of 3 months, no catalyst deactivation 
or depletion had occurred, i.e. the catalyst system according to the 
invention as thermally stable.