Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~2Z~708 HOE 81/H 040
The present invention relates to a process for making
1,2-dichloroethane by reacting ethylene and chlorine in it-
quid 1,2-dichloroethane in the presence of a customary cay
Tolstoy, technically beneficial use being made of the react
lion heat which is evolved during the reaction and the us-
desirable formation ox higher chlorinated products 9 such as
in-, twitter and pentachloroethane, inside the reactor being
extensively avoided as well as the accumulation of such pro-
ducts therein.
The chlorination of olefins by means of chlorine is
known to tare place as exothermal reaction. In the event
of ethylene being chlorinated with chlorine 2200 kJ heat
is evolved per kg 1,2-dichloroethane. This means in other
words that a quantity of heat sufficient for the generation
of about 1 ton steam is evolved upon the production of 1 ton
1,2-dichloroethane. It the processes or making dichloro-
ethanes described heretofore, the reaction heat was either
abstracted by cooling the reactor or used partially for
directly evaporating and expelling the dichloroethane formed
during the reaction from the reaction mixture or reactor, and
in some case or other partially or completely but exclusively
for rectifying 1,2-dichloroethane made by another process.
me process described in DEEPS 15 43 108, for example,
provides or the combined abstraction of the reaction heat
which is evolved during the chlorination of ethylene with
chlorine. More especially, the iron reactor used for carry-
in out the reaction is provided with a cooling means which
is supplied with cooling water permitting the neat evolved
during the reaction to be abstracted and a predetermined
reaction temperature of 50 up to 70C to be maintained.
The reaction temperature is lower than the boiling point
of 1,2-dichloroethane and is controlled during the react
lion so as to ensure continuous removal ox the 1,2-dichlo-
Raytheon formed in vapor Norm from the reaction chamber,
While no higher chlorinated products accumulate in this
process inside the reactor, the fact remains that 3.3 %
trichloroethane is being formed and that the reaction heat
remains unutilized as it is necessary or condensed Dow-
chloroethane to be freed from the byproduct just specified.
A process basically the same as that described in
DEEPS 15 43 108 has been disclosed in DEMOS 29 35 8849 this
latter process comprising: during the reaction, circulating
the material placed in the reactor through an annular con-
dull communicating with the reactor and separating vaporous
products issuing at the head of the reactor in a rectifying
column with recovery of 1,2-dichloroethane. Higher boiling
by-products are recycled from the base portion of the fee-
tidying column to the reactor; this however is disadvant-
ages as reaction product which is removed discontinuously
from the column base portion is required Jo be worked up so-
portly and as the reaction heat evolved can be utilized
partially only
A further process for making ethylene chloride (cf.
DEMOS 24 27 045) provides:
a) or ethylene and chlorine to be introduced into a
reaction zone maintained under elevated pressure and
having a liquid medium containing chlorinated C2 ho
~2~2~7~1~
drocarbons or mixtures thereon circulated therein,
the medium being kept at a temperature lower than
its evaporation temperature under the pressure pro-
veiling inside the reaction zone with formation of
crude liquid ethylene dichlorides
b) or the crude liquid ethylene dichlorides to be intro-
duped together with the circulated medium into a zone
maintained under lower pressure than the reaction zone,
i.e. under a pressure and at a temperature at which
the crude ethylene dichlorides becomes evaporated under
the action ox the reaction heat set tree during the
reaction ox chlorine with ethylene, and
c) for vaporous crude ethylene dichlvride to be intro
duped into a rectifying zone and to be rectified there-
in with the aid of the reaction heat set tree during
the reaction of chlorine with ethylene, purified ethyl
tone dichlorides being removed from the rectifying zone,
and product obtained in the base portion of the recta-
vying column being recycled to the above zone main-
twined under lower pressure, and combined with the
medium circulated therein.
Recycling the base product into the reactor is disk
advantageous inasmuch as the circulated liquid medium be-
comes enriched with higher boiling chlorination products
which must successively be removed therefrom. As indicated
in Example 4 of DEMOS 24 27 045 the circulated medium con
twins about 60 % 1,1,2-trichloroethane. This means in other
words that the chlorination reaction described heretofore
is accompanied by the formation ox considerable proportions
I
of undesirable by-products.
It has therefore been desirable to improve the processes
described heretofore so as to extensively avoid the formation of
by-products and provide for an optimum utilization of the
evolved reaction heat. This is extensively achieved by a
process for making 1,2-dichloroethane by reacting ethylene and
chlorine in a reaction zone having a liquid medium containing
chlorinated C2-hydrocarbons circulated therein at a temperature
lower than the evaporation temperature of said medium under the
pressure prevailing inside the reaction zone, in the presence of
a customary chlorination-inducing catalyst and optionally an
inhibitor reducing the formation of by-products so as to obtain
crude 1,2-dichloroethane, removing the crude dichloroethane from
the reaction zone and purifying it in a separate downstream
fractionating zone, the process comprising:
a introducing approximately equimolar proportions of ethylene
and chlorine into the circulated liquid medium; intensively
mixing the whole in a mixing zone and then reacting the mix-
lure in a reaction zone at a temperature of about 75 up to
200C under a pressure of about 1 up to 15 bars, the mean
sojourn time of the reaction mixture in the mixing zone and
reaction zone being equal to about 1 to 15 hours;
b) removing a portion of the liquid reaction mixture from the
reaction zone and subdividing said portion into two partial
streams, passing one of these partial streams through a heat
Lo 8
exchanger for abstraction of calorific energy therefrom and
for reduction of its initial temperature and recycling it
to the mixing and reaction zone; introducing the second
partial stream in-to an expansion vessel and evaporating
therein a quantity of reaction product corresponding to the
quantity of reaction product formed in the reaction zone and
optionally also a proportion of 1,2-dichloroethane original-
in from a third source and being introduced into the reaction
zone, introducing resulting vaporous matter into a fraction-
cling column and recycling unevaporated liquid matter of the
second partial stream into the liquid medium circulated in
the mixing and reaction zone; and
c) separating distillatively 1,2-dichloroethane from the vapor-
out matter introduced into the fractionating column with the
use of a portion of the heat energy transferred inside the
heat exchanger and removing the 1,2-dichloroethane overhead,
higher chlorinated products being obtained in the columns
base portion from which they are removed and worked up
separately. The present invention now provides an improved
form of carrying out the process as discussed above which is
effected in a double loop reactor.
The improved process of -the present invention for
making 1,2-dichloroethane by reacting ethylene and chlorine in
a reaction zone having a liquid medium containing
chlorinated C2-hydrocarbons circulated therein in the
presence of a customary chlorination-inducing catalyst and
optionally an inhibitor reducing the formation ox by pro-
ducts, wherein
a) approximately equimolar proportions of ethylene and
chlorine are introduced into the circulated squid
medium, the whole is mixed in a mixing zone and the
mixture is reacted in a reaction zone at a temperature
of about 75 up to 200C under a pressure of about 1
up to 15 bars, the mean sojourn time of the reaction
mixture in the mixing zone and reaction zone being
equal to about 1 to 15 hours; and wherein
b) a portion of the liquid reaction mixture is removed
from the reaction zone and subdivided into two partial
streams, of which one is passed through a heat
exchanger for abstraction of caloric energy there-
from and for reduction of its initial temperature, and
then recycled to the mixing and reaction zone whilst
the second partial stream is introduced into an expand
soon vessel and a proportion of reaction product
corresponding to the quantity ox reaction product
formed in the reaction zone is evaporated from said
second partial stream, the resulting vaporous matter
is introduced into a fractionating column and 1,2-
dichloroethane is distillatively separated, and
unevaporated liquid matter of the second partial
stream is recycled into the liquid medium circulated
in the mixing and reaction zone, comprises: preparing
~2~L70~3
the 1,2-dichloroethane inside a double loop reactor
by
A) introducing ethylene through line (1) and chlorine
gas through line (2) in-to the ascending portion ox
loop (I) at a level below the mixing zone (3) form-
in part of the ascending polo boon and finely
distributing them in the liquid medium circulated
through loop (I), and by reacting the reaction
components in reaction zone (4) and sojourn zone
(5), respectively upstream ox the mixing zone (3)
and
B) removing from loop (I) two partial streams of reaction
mixture, of which one is introduced through line (8)
into heat exchanger (10) for abstraction of calorific
energy therefrom and recycled through line (9) into
the descending portion of loop (I) whilst top second
partial stream is introduced into loop (II) integrally
connected to loop (I) and into expansion zone (6)
forming part of loop cycle (II), in which a proportion
of reaction product corresponding to the quantity of
reaction product formed in reaction zone (4) is
evaporated from said second partial stream, the
resulting vaporous matter is delivered through line
(7) to the fractionating column, and unevaporated
, 25 liquid matter of the second partial stream is recycled
through the descending portion of loop (II) into the
mixing zone (~) and reaction zone (4), respectively
of loop (I).
A preferred feature of the present process provides
or inert gases or low-boiling hydrocarbons such as ethyl
chloride being contained in the reaction mixture to be
removed from sojourn zone (5) through line (11) or from
the descending portion ox loop (I) through line (12).
The following statements are intended further to ill-
strata the process of this invention.
It is possible for the chlorine and ethylene reactants
to be diluted with inert gases. The chlorine can be intro-
duped into the mixing zone in the form of liquid or gaseous matter, liquid chlorine being preferably evaporated ahead
of the reactor in a heat exchanger with the aid of a port
lion of the reaction enthalpy. Iron-III chloride should
preferably be used as a catalyst and oxygen should preferably
be used as an agent inhibiting the formation of byproducts.
The liquid medium is circulated through the reactor in
accordance with the principle underlying a thermosiphon or
mammoth pump. Inside the mixing zone, the liquid medium
should conveniently be circulated with a velocity of at
least 0.1 m/second. The circulation for effecting ova-
proration of product can also be effected in accordance
with the principle underlying a thermosiphon. The heat
exchanger may be arranged so as to form an integral part of
the product cycles, or can be fed separately by means ox a
pump.
The process of this invention will now be described
with reference to the accompanying drawing.
Liquid 1,2-dichloroethane it introduced into a double
loop reactor comprising loop cycles I and II. Next, ethylene
is introduced through line 1 and chlorine gas is introduced
through line 2 to effect circulation of the 1,2-dichloro-
ethanes in accordance with the principle underlying a
mammoth pump. Once the ethylene has commenced reacting
with the chlorine gas, the reaction being started inside
packed mixing zone 3 and completed inside reaction zone 4
and sojourn zone 5, additional buoyant forces occur in the
ascending portion of loop I, which originate from the react
lion heat set free. The temperature prevailing in loop
cycle I is slightly lower than the boiling temperature of
1,2-dichloroethane inside the reactor under the pressure
prevailing. Inert gases which may be found to be present
in loop I are removed through lines 11 and 12, and cooled
in a cooler (not shown in the drawing) in order to condense
vaporous 1,2-~ichloroethane which may have been carried
along. Uncondensed gay is allowed to escape and worked up
in known fashion. By regulating the flow of inert gas and
the quantity of gas which is removed it is possible to
establish the pressure desired to prevail in loop I.
To remove produced 1,2-dichloroethane from loop I,
the stream ox liquid matter is subdivided into two partial
streams; one of these two partial streams is passed
through line 8 into heat exchanger 10 for abstraction of
heat energy therein and is then recycled through line 9 into
the descending portion of loop I, whilst the other is
introduced into loop II which is integrally connected to
loop I and into an expansion zone 6, in which a quantity
of reaction product corresponding to the quantity of react
lion product formed in reaction zone 4 is evaporated, the
~.~2~L70~
resulting vaporous matter being introduced through line 7 into
a fractionating column (not shown in the drawing), whilst
unevaporated liquid matter of the second partial stream is
recycled through the descending portion of loop II into mixing
zone 3 and reaction zone 4, respectively. Inert gases or low-
boiling hydrocarbons, such as ethyl chloride, are taken from
sojourn zone 5 through line 11 or from the descending portion of
loop I through line 12.
The process of this invention offers technically
beneficial effects which are the same as those offered by the
process discussed above. They originate from the continuous
removal of a portion of liquid matter from the reactor and its
division into two partial streams of which one permits reaction
heat to be continuously recovered, and the other is partially
evaporated, the evaporated portion being worked up in the
fractionating column; as a result, it is ensured that catalyst-
free crude dichloroethane is introduced into the fractionating
column, which however also receives the higher chlorinated by-
products together with the evaporated matter. In other words,
by-products are substantially not liable to accumulate in loop
I. In the processes described heretofore, such by-product
accumulation gives rise to the concentration of higher chlorinated
by-products which ultimately must invariably be removed from the
reactor Needless to say catalyst losses are associated therewith
which naturally affect the economy of these processes. Under
the reaction conditions used in accordance with this invention,
~L22~ 8
the mean sojourn -time of all reactants inside the reactor is
shortened so that undesirable side-reactions involving by-
product formation are extensively avoided.
The present process also permits use to be made of
feed materials contaminated with inert gases which normally entail
difficulties in the decontamination of dichloroethane in the
fractionating column. In accordance with this invention, the
inert gases are already removed from loop I via inert gas removal
lines 11 and 12 so that they are definitely prevented from
affecting the work-up of the reaction mixture.
The present process finally compares favorably with
that discussed above by the use of a double loop reactor in which
the reaction mixture is continuously circulated through loops I
and II in accordance with the principle underlying a thermosiphon
or mammoth pump. In other words, no special pumps permitting
the reaction mixture to be introduced into, or to be taken from !'
the reactor have to be used which naturally means an economy of
energy.
Example
A reactor such as that shown in the drawing with a
capacity of about 15 1 contained about 15 kg 1,2-dichloroethane
and 0.1 % iron chloride as a catalyst. 110 l/h ethylene
was introduced through line 1 and about 110 l/h chlorine and
10 l/h air were admitted through line 2. The temperature in the
reactor was about 115C, the pressure
7~3
prevailing in sojourn zone 5 was about 3 bars and the
pressure difference between sojourn zone 5 and expansion
zone 6 was about 0.6 bar.
The gas coming from the reactor was taken prom sojourn
zone 5 through line 11. In a cooling trap, it was freed at
-30C from condensable matter. 480.1 g/h vaporous dip
chloroethane was taken from the expansion vessel 6 through
line 7 and condensed.
About 200 l/h reactor liquid was pumped through lines
8 and 9 for abstraction of reaction heat. Heat abstracted
in heat exchanger 10 was used for distilling dichloroethane
at a base temperature of the respective column of 80 to
85C.
After an operation period of 48 hours, the Dow-
chloroethane removed was analyzed and found to contain:
C2H5Cl 0.0024 wit
1,1-EDC 00002 wit %
1,2-EDC 99.86 wit %
1,1,2-ETC 0.13 wit %
