Note: Descriptions are shown in the official language in which they were submitted.
HOE 78/F 194
8980
This invention relates to a process for the continuous
manufacture of octachlorocyclopentene by a one-stage chlor-
ination of cyclopentadiene in inert solvents and under ele-
vated pressure. The reaction proceeds according to the
5 equation
5H6 + 7 Cl2 = CsCl8 ~ 6 HC]
Octachlorocyclopentene is used as intermediate for the
manufacture of dyestuffs, plastic materials and insecti-
cides. It is particularly suitable as starting material ;
for making hexachlorocyclopentadiene (cf. US-PS 2,742,506)
which can be used for the manufacture of cyclodiene insec-
ticides.
Since the first manufacture of octachlorocyclopentene
in 1877, numerous ways of synthesis have been proposed of
15 which only the chlorination of aliphatic and cyclic C5-
hydrocarbons has gained a certain industrial importance ?
(cf. Ungnade, McBee, Chem. Rev. 58, page 289 (1958)).
According to US-PS 2,714,124 chlorinated C5-hydrocar-
bons having at least two chlorine atoms in the molecule
20 are reacted with chlorine on porous, surface-active cata-
lysts at a temperature of from 280 to 500 C to give octa-
chlorocyclopentene. Preferred starting compounds for this
reaction are polychloropentanes having more than 5 chlorine
atoms, which have to be prepared by photochlorination of
25 pentanes, for example by the process described in US-PS
2,473,162.
Another two-stage synthesis is described in US-PS
2,900,420 in which a product mixture defined as "tetra-
chlorocyclopentane" is first produced by chlorination of
cyclopentadiene in liquid phase at a temperature of
., .
.
HOR 78/F 194
from -50 to ~80 C, which mixture is then reacted with
further ch]orine at temperatures rising from 170 to 275~ C
to give octachlorocyclopentene. By adding a catalyst, for
example arsenic trioxide, the reaction time can be reduced
from 39 hours to 11 hours with the use of 0.7 to 0.8 kg of
tetrachlorocyclopentane. To increase the chlorinc concen-
tration in the liquid phase pressures of up to 35 bar are
recommended. In this patent specification it is expressly
stated iII column 6, lines 30 to 64, that the reaction of
cyclopentadiene with chlorine to give octachlorocyclopen-
tene has to be carried out in two stages. The first reac-
tion stage, i.e. the chlorination of cyclopentadiene to
tetrachlorocyclopentane is strongly exothermal and, there-
fore, the temperature has to be maintained below 80 C by
cooling in order to avoid secondary reactions. This can be
done without any adverse effect since the reaction proceeds
very r~pidly even at a temperature of 0 C. As compar~d
therewith, the chlorination of tetrachlorocyclopentane to
octachlorocyclopentene takes place relatively slowly even at
the initial boiling temperature of the organic mixture of
170 C. A combination of these two reaction stages, which
have to be carried out at very different temperatures, for
the purpose of a continuous manufacture of octachlorocyclo-
pentene is difficuIt and expensive.
Another two-stage synthesis is proposed in US-PS
3,723,272. The first stage comprises the thermal splitting
of dicyclopentadiene to give cyclopentadiene which is then
reacted, after *ilution by chlorinated cyclopentanes,with
an excess amount of chlorine, preferably at a temperature
`
, '
; ' ~ ' .
HOE 78/F 194
8g~30
o~ 60 to 1~0 C, with or without ultraviolet light, to give
a polychlorocyclopentane having g or 5 chlorine atoms in
the molecule. In the second stage this product is chlorin-
ated at 160 C while being exposed to ultraviolet light to
give octachloroeyclopentene.
The present invention provides a process or the con-
tinuous manufacture of octachlorocyclopentene from cyclo-
pentadiene and chlorine, whieh comprises combining eyclo-;
pentadiene, an inert diluent and an at least stoichiometric
amount of chlorine under a pressure of 20 to 300 bar at
temperatures of the three liquid components of at most 60 C
and limiting the maximum temperature of the following exo-
thermal reaetion to 200 to 500 C.
The organic starting compound in the process of the
invent'ion is eyelopentadiene. In prineiple eyelopentene
and eyelopentane eouId also ~e used, but they are notavail-
able as raw material in the s~me measure as cyclopentadiene
and do not offer any advantage over eyelopentadiene.
Chlorine is used in an at least stoiehiometrie amount.
In order to avoid the formation of carbon black 110 to 800 %
of the stoichiometric ehlorine amount, preferably 110 to
400'%,and more preferably 110 to 200'%, will generally be
- used.
- Cyelopentadiene is reaeted with ehlorine in the pre-
senee of one or several diluents to avoid the formation of
earbonization products in the strongly exothermal reaction.
The diluents should not react with cyclopentadiene since
otherwise the yield of oetaehloroeyelopentene would be re-
dueed and disturbing by-produets would be formed. The di-
-- 4 --
~., , . , ~ ,, .
. . ' ' . :, ~
' ' ' ":'.' ~ :'"-" ' ,'
,. . '' .: ' ,' ' ' , . : ~ ' '
.
. .
.
~IOE 78/F 194
luents should also be inert to chlorine in order not to in-
crease the reaction entl1alpy set free and the chlorine de~
mand. Compounds that comply with these requirements are,
for example perchlorinated hydrocarbons such as tetrachloro-
methane and octachlorocyclopentene. The latter can be usedin pure form but also in the form of a crude product of the
instant process substantially freed from chlorine, which is
much more economical. The proportion by weight of diluent
to cyclopentadiene is generally in the range of from 60 : 40
to 99 : 1, preferably 70 : 30 to 99 : 1, and more preferably
80 : 20 to 99 : 1.
Cyclopentadiene and the diluent are combined either
individua]ly or in the form of a mixture, under a pressure
of from 20 to 300 bar, with an at least stoichiometric
amount of chlorine, all three components being in theliquid
state and having a temperature of from their respective
melting point to ~60 C. Cyclopentadiene tmelting point
-97 C) and chlorine (melting point -101 C) are preferably
used at a temperature of from -50 to +30 C, more prefer-
ably -30 to ~10 C. These two components react spontane-
ously with each other with heating of the reaction mixture
to high temperatures. At a temperature above 500 C chloro-
lysis of the C5-ring to tetrachloromethane, hexachloro-
ethane and hexachlorobutadiene takes place to an increasing
extent and, therefore, the temperature should not exceed
500 C anywhere in the reactor. On the other hand, it should
not fall below 200 C at all places inside of the reactor.
To adjust the maximum temperature in the reactor in the
range of from 200 to 500 C a sufficient excess of chlorine
-- 5 --
,
::
HOE 78/F 194
1~8~
is preferably used which acts as coolant. It is obvious,
of course, that under otherwise identical conditions a
higher chlorine excess is required to adjust a maximum ten-
perature of 200 C than for adjusting a maximum temperature
of 500 C. The total amount of chlorine used for reaction
and cooling is at most 800 ~ of the stoichiometric amount.
Besides this adiabatic mode of operation, the surplus of
reaction enthalpy can be transferred to an external cooling
medium via a heat exchanger.
In the process of the invention catalysts and high
energy radiation such as ultraviolet light need not be used.
Hence, no problems arise concerning the separation and re-
generation of catalytically effective substances or the de-
posit of carbon black on the windows of the light sources.
The reaction is carried out under a pressure of from
20 to 300 bar, a range o~ from 50 to 250 bar being prefer-
red.
In spite of the dilution of the cyclopentadiene, a
space-time-yield of up to 30 kg of octachlorocyclopentene
is obtained per liter of reaction space and hour. Conse-
~uently, a reactor having very small dimensions can be used
for the continuous process of the invention.
In general, the selectivity for octachloro~ycloFentene is
considerably above 90 %. Small amounts of tetrachlorome-
~
thane, hexachloroethane, hexachlorobutadiene and hexachloro-
benzene are formed as by-products but no chlorinated cyclo-
pentadiene oligomers which, according to literature (cf.for
example Burmakin et al., J. Appl. Chem. (UdSSR) 40, page
1536 (1967)), would have to be expected to a considerable
-- 6 --
' ' : .
,- : :' : '
HOE 78/F 194
extent in the chlorination of cyclopentadiene in the liquid
phase at a temperature above 50 C.
In contradistinction to the aforesaid multi-stage chlo-
rination processes, in the process according to the inven-
tion the total amount of hydrogen chloride resulting fromthe reaction of cyclopentadiene with chlorine is obtained
in one stage and at elevated pressure. Hydrogen chloride
can be separated more easily under elevated pressure and
isolated in dry and pure form in which it can be further
used directly in hydrochlorination or oxychlorination re-
actions or inHCl electrolysis processes. Correspondingly,
the excess of chlorine can be obtained under pressure in a
form that is easy to liquefy and which can be used again
without difficuIty for the chlorination of cyclopentadiene.
It is, therefore, preferred to work up the reaction mixture
under ~levated pressure, although working up under atmos-
pheric pressure is likewise possible.
The present process is thus excellently suitable for
the continuous manufacture of octachlorocyclopentene from
cyclopentadiene and chlorine. The advantages for a commer-
cial use are especiaily the one-stage reaction, the very
high space-time-yield and the relatively easy separation
of the products obtained under pressure.
As reactor a high pressure tube with nickel lining
proved to be suitable which is provided at the inlet side
with a two substance nozzIe for the intense mixing of the
reaction components. Other reactor designs and other mix-
ing means are likewise possible.
The following examples illustrate the invention:
.
--7--
:' - . . . .
HOE 78/F 19~
980
E x a m p l e s
The chl~rination of cyclopentadiene was carried out in
a vertical high pressure tube of high temperature stainless
steel and provided with a nickel lining. The tube had a
length of 2200 mm, an outer diameter of 48 mm, an inner dia-
meter of 25 mm and was closed at the ends with a nickel lens
each. Prior to the beginning of the reaction the reactor
was heated to an internal temperature of 200 C by means of
4 jacket heatings. Dilute cyclopentadiene and chlorine
were introduced by means of membrane pumps in liquid form
through a two substance nozzle at the lower end of the re-
actor at the temperatures indicated in the following table.
The maximum internal temperature in the reactor was measur-
ed by shifting a thermoelement in a stainless steel tube
enclosed in a nickel tube (outer diameter 10 mm), which tube
pro~ected from above into the reactor over a length of 2100
mm. The respective temperature was adjusted by variation
of the amount of chlorine added. The jacket heatings were
switched off as soon as the desired maximum internal reac- -
tor temperature had been reached. At the upper end of the
reactor the pressure of the products was released to atmo-
spheric in a high pressure valve in order to determine the
selectivities and space-time-y,ields of octachlorocyclopen-
tene while renouncing the recovery of hydrogen chloride and
chlorine. To this end the product mixture was passed into
a separator cooled with a mixture of butanol and dry ice
in which mainly hydrogen chloride and part of the chlorine
were not condensed. The condensate was freed from chlorine
by distillation and analyzed. The space-time-yields were
. ~
:
, .
HOE 78/F 194
~89~30
calculated on a free reactor volume of 0.9 liter. No
forma,ion o carbon black was observed.
. . .
'' :
,
~8980
N ~ N
C5~ ~ ' '
Ln a~ o u~ o t~
_ ,
- ~ S~
~0 ~0 ~ o o~ .'
S . O O O O O O '
. U~ O O Lr) U~ o
~ '
~) O O O O O O
.~ ~ 1 .,
. .
~ ~ ~ .
. ~ ~ . ~ .
W~ ~ ' ,. .
m .Y ~ " er
,~
E-~ ~ ~ ~ er ~ ~ .
.
~d ~ ~ ~ 1~ oo O
el ~ ~d ~ a~ o ~ 3'
: n. _ ~ S~
~1 ~ a ~ I O ~ = . . N I ~
~ ~ ~ r __
X
..... . . . .
. .
`
