Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
to
HOE 82/H 047
It is known that 1,2-dichloroethane can be mode by react
tying ethylene with chlorine in 1,2-dichloroethane as a solvent
and reaction medium. To accelerate the chlorine addition, the
art provides for chlorides of the elements belonging to groups
IV to VI of the Periodic System and more especially for ashy-
dross iron(III)chlorlde, which is readily accessible and in-
expensive, to be used as catalysts, if desired in the presence
of oxygen. 1,1,2-trichloroethane which originates from a subset-
tuition reaction dichloroethane undergoes is obtained as the
principal by-product ox this reaction.
It industry 9 the additive combination of chlorine with
ethylene is effected at reaction temperatures of about 90 C,
the reaction product being in this case distilled off from the
reaction mixture with utilization OX the reaction heat set free,
but also at temperatures between 30 and 60C ( CAL . Ullmanns
Ency~lopadie don technician Chemise) volume 9, Thea edition,
1975, page inn this latter case, it is not possible for the
reaction heat to be used for rectifying crude dichloroethane;
it is rather necessary fur it to be abstracted by forced Clark-
lotion of the reaction medium through heat exchangers (cf.German Patent Specification DEMOS 19 05 517).
As regards crude catalyst-containing dichloroethane made
at the lower temperatures specified, the art provides for it to
be taken from the reactor, to be wasted with water or an aqueous
alkali metal solution so as to be freed from catalyst and hydra-
gun chloride, to be separated from the aqueous phase, and worked
up distillatively in known manner.
Toe use of Focal as a catalyst in the addition chlorination
of ethylene entails certain adverse effects. In the presence ox
water, Focal has corrosiveness for metallic materials such as
those normally used for making reactors, columns or heat ox-
changers. Needles to say commercially pure chlorine which is
normally used for effecting the chlorination always contains
traces o moisture; in addition to this, hydrogen chloride
originating from undesirable side-reactions is invariably ox-
twined.
In German Patent Specification DEMOS 31 48 450, it has
been disclosed that corrosion-sensitive reactors as used in the
production of 1,2-dichloroethane are considerably less corroded
by a catalyst mixture consisting of Focal and certain addends
than by Focal alone. These addends haze even been found favor-
ably to influence, namely to reduce the formation ox by-products.
German Patent Specification DEMOS 31 48 450 relates more
particularly to a catalyst mixture consisting of an hydrous iron
~III)chloride and a second mixing component, for mixing Dow
chloroethane by reacting ethylene with chlorine in a solvent at
atmospheric or increased pressure, the catalyst mixture being
characterized in that the said second mixing component is a
nitrogen base or salt thereof which is used in a proportion
approximately equivalent to the proportion of iron(III)chloride.
The nitrogen base may be selected from NX3, a primary,
secondary or tertiary alkyd, aralkyl, aureole or alicyclic amine
or polyamide. The salt of the nitrogen base preferably is a
halogen salt, ego ammonium chloride.
The catalyst mixture disclosed in German Patent Specific-
lion DYES I 48 450 is particularly useful for chlorinating
ethylene at increased temperature, the reaction heat being
utilized for removing freshly produced 1,2-dichloroethaIle in
vapor form prom the reactor. The catalyst is retained in the
I
reaction mixture so that Just minor quantities get lost
which must naturally be replaced by fresh catalyst, from
time to time.
In those chlorination processes however which are
effected at temperatures lower than the boiling range OX
1,2-dichloroethane, the catalyst is removed from the result-
in crude dichloroethane by scrubbing it, e.g. with water,
the catalyst becoming dissolved in the scrubbing water; in
other words, more catalyst is lost which has to be replaced
by fresh catalyst.
The catalyst-forminJ components used in the process ox
German Patent Specification 31 48 450, namely anh~-drous Focal
and a nitrogen base, undergo reaction in the chlorination
batch to give a catalyst of winch even minor proportions are
highly efficient so that it is desirable for said catalyst to
be recovered during the work up of the chlorination mixture,
depending on its concentration therein, and to be used again
in the chlorination of ethylene. To this end, the invention
provides Lo the catalyst containing chlorination mixture to
be worked up.
The present invention relates more particularly to a
process for making 1,2-dichloroethane by reacting ethylene
with chlorine in a solvent in the presence of z catalyst
mixture consisting of an hydrous iron(III)chloride and a
nitrogen base or a salt of said base and, optionally an agent
inhibiting the formation of by-products at a temperature lower
than the boiling point of 1,2-dichloroethane of about 20 to
100C at atmospheric or increased pressure, and separating
the 1,2-dichloroethane from thy chlorination mixture, which
30 comprises:
~.~Z7 ~96
a) introducing the chlorination mixture into a distilling
column, distillatively separating said 1,2-dichloro-
ethanes prom said mixture until the catalyst commences
precipitating from liquid base product, separating said
precipitated catalyst from said base product, and no-
using the catalyst so separated for reacting further
ethylene with chlorine in contact therewith, or
b) passing the chlorination mixture over an adsorbent,
adsorbing the catalyst contained in said mixture on the
adsorbent, distillatively separating 1,2-dichloroethane
from resulting filtrate and recovering the catalyst from
the adsorbent by extracting it with a solvent, or
c) subjecting the chlorination mixture to the processing
treatment set forth under a) and discarding base product
containing minor proportions of catalyst.
It is good practice to carry out the present process us-
in a reaction batch containing iron(III)chloride in a proper-
lion ox 0.001 to about 0~5 weight %, preferably 0.002 to 0.1
weight %, based on the quantity ox solvent. The quantity of
nitrogen base or salt thereof should preferably be equivalent
to the Focal quantity.
The solvent which should conveniently be used is Dow
chloroethane just as in the prior art methods for making 1,2-
dichloroethane.
In accordance with a preferred feature of the invention,
the adsorbent used for treating the chlorination mixture it
active carbon, a basic ion exchanger or Sue or aluminum
oxide. The catalyst should preferably be extracted with the
use of 1,2-dic~loroethane or another readily volatile sheller-
noted hydrocarbon or hydrochloric acid.
:12~'74~16
In the event ox thy base product containing not more
than about 0.001 weight catalyst, based on the liquid
matter constituents of the base product, where catalyst
separation would be difficult and commercially unattractive,
the invention provides for such separation to be dispensed
with and or the catalyst-containing base product to be
discarded.
With the exception of minor proportions of try-
chloroethane and hydrogen chloride, respectively, the present
catalyst permits the Russian of by-products to be suppressed
or substantially suppressed and compares favorably in this
respect with toe prior art. I addition to this, the reaction
solution remains clear even over prolonged reaction periods
in all those cases in which the chlorination batch has e.g.
ammonia as the nitrogen base admixed with it. Reaction mix-
lure which may have darkened during the reaction reassumes
a lighter coloration a short while aster the addition ox
ammonia. Finally, the conversion fate in the process of this
invention is almost quantitative and the space/time-yield is
high. This result it obtained even with the use of toe
catalyst in a concentration of less than 0.003 weight Jo
based on Focal.
The work up of the chlorination mixture as disclosed in
this invention would not appear to have been obvious in view
of the need first to discover that the chlorination mixture
which is to be worked up no longer contains Focal and nitrogen
base as individual catalyst components but their reaction
product as a catalytically active material whose catalytic
activity greatly excels that of Focal. In view ox this, it
has been found good practice to recover this particular gala-
lust in contrast with the Focal used in standard processes.
The process of this invention can for example, be
ejected in the loop reactor disclosed in DEMOS 24 27 045 or
any other suitable reactor.
Example 1
A cylindrical reactor which had a volume of about 25 my
was charged with 20.000 liters 1,2-dichloroethane and the
whole was admixed with 170 my iron(III)chloride per kg 1,2-
dichloroe-thane. Next,Othe resulting solution was admixed
with about 600 1 ammonia. Under a pressure of about 1.3
bars near the head of the reactor and at a temperature ox
the reaction mixture of about 40C, the reactor was fed per
hour with 1,008 I ethylene and 2,540 go chlorine gas which
contained about 4 vowel additional inert gas, arid with 8 my
air Toe chlorination batch was additionally admixed per
hour with about 80 1 ammonia and 170 my Focal.
3,542 kg/h crude dichloroethane was taxes from the
reactor and introduced into the base portion OX a distilling
column. The crude product had the hollowing composition:
C2H4 0.0069 wit 56
2 5 l 0.0081 wit I
1,2-EDC 99.8 wit %
1,l,2-~TC 0.15 wit
(ED = dichloroethane; ETCH = trichloroethane)
The column was operated under moderate o~erpressure
(about 0.7 bar absolute) near the column head. 95 % of
desirable reaction product was distilled of from the
reaction mixture. The 1,2-dichloroethane so purified was
composed as follows:
C2H~Cl 0.01 wit %
1~2-EDC 99.98 wit %
1,1,2-ETC 0.01 wit 76
The product obtained in the base of the column was
5 cooled and filtered, and the resulting filtrate was introduced
into a vacuum column and work-up was continued. Separated
catalyst was taken from the filter with exclusion of moisture
and introduced into a tank filled with a solution of 1,2-
dichloroethane. As the chlorination process went on, the
10 quantity of catalyst needed for the reaction was taken from
the recovered catalyst quantity, the supply ox iron)
chloride and ammonia being stopped.
Example 2
About 1.2 kg of the crude product of Example 1 was passed
15 per hour through a column which had a layer of 33~ g active
carbon placed therein over a length of 850 mm. After 6 day,
iron could not be detected in the adsorbed outlet. 1,2-dichloro-
ethanes was d~stillatively separated from the filtrate obtained.
The active carbon was regenerated with dilute hydrochloric
20 acid.
Example
A reaction mixture produced as in example 1, which contain-
Ed 0.275 wit 96 Fake and an equivalent proportion of ammonia
was passed through an absorption column having finely granular
25 Sue placed therein, to effect the-separation of the catalyst.
After absorption of a catalyst quantity which corresponded to
3.85 g Focal per 100 g Sue, the adsorbent was saturated. It
was extracted with hot 1~2-dichloroethane and 2.3 g Focal per
100 g Sue was recovered. The concentrated catalyst solution
30 was recycled into the chlorination reactor whereby it was
possible to maintain the necessary catalyst concentration in
the reactor, without further supply of Focal and NO
