Note: Descriptions are shown in the official language in which they were submitted.
PROCES~ FOR PRODUCING p-CHLOROBENZENES
The present inven-tion relates to a process Eor
producing a p-chlorobenzene such as p-chlorotoluene or
p-dichlorobenzene which is useful as a starting material
for the production of medicines and agricultural
chemicals. More particularly, it relates to a process
for producing a p-chlorobenzene such as p-chlorotoluene
or p-dichlorobenzene with a high selectivity by
chlorinating a benzene with use of a novel catalyst.
1~ Chlorobenzenes are useful as starting materials for
medicines and agricultural chemicals. Particularly,
there are strong demands for p-chlorobenzenes such as
p-chlorotoluene and p-dichlorobenzene among them.
Accordingly, there have been various studies to improve
the selectivity ~or p-chlorobenzenes~
Namely, as a process for producing p-chlorobenzenes
by chlorinating benzenes in a liquid phase in the
presence of a catalyst, there have been proposed, for
instance, a method wherein toluene is chlorinated by
using a catalyst comprising a Lewis acid and sulfur or
selenium to obtain p-chlorotoluene with a selectivity of
~q
~;292~
-- 2 --
from 45 to 52~, a method wherein toluene is chlorinated
by using a catalyst comprising a Lewis acid and
thianthrene to obtain p-chlorotoluene wi-th a selectivity
of from 55 to 60% (U.S. Patent 4,031,147), a method
wherein toluene is chlorinated by using a catalyst
comprising a Lewis acid and a phenoxathiin compound to
obtain p-chlorotoluene with a selectivity of from 52 to
60~ (U.S. Patent 4,4~4,983), a method wherein
chlorobenzene is chlorinated by using iron sulfide as a
1~ catalyst to obtain p-dichlorobenzene with a selectivity
of from 60 to 70% (U.K. Patent 1,476,39~), and a method
wherein chlorobenzene is chlorinated by using selenium or
a selenium compound as a catalyst to obtain
p-dichlorobenzene ~ith a selectivity as high as about 72
1~ (Japanese Examined Patent Publication No. 34010/1975).
Further, as an improvement over these conventional
methods, the present inventors have earlier proposed a
method wherein toluene is chlorinated by using L-type
zeolite as a catalyst t.o obtain p-chlorotoluene with a
selectivity of about 65% (EP 112,722A1), or a metho,d
wherein chlorobenzene is chlorinated by using L-type
zeolite as a catalyst to obtain p-dichlorobenzene with a
selectivity of about 86~ (EP 118, 851A1) ~
However, none of these methods provid~s a sufficient
selectivity for p-chlorobenzenes, and is not necessarily
satisfactory as a process for producing p-chlorobenzenes~
Under the circumstances, it has been desire.d to develop a
method which is capable of producing p-chlorobenzenes
~2~
-- 3 --
with a better selectivity and less production of
b~-products.
Accordingly, it is an object of the present invention
to provide a process for producing p-chlorobenzenes with
a high selectivity by the chlorination of substituted
benzenes in a liquid phase in the presence oE a catalys-t.
The present inventors have conducted extensive
researches to overcome the above-mentioned drawbacks
inherent to the conventional methods and to develop a
process capable of producing p-chlorobenzenes with a high
selectivity. As a result, they have found that the
object can be attained by using a combination of a
certain selected zeolite and a certain selected aliphatic
alcohol, as a catalyst. The present invention has been
accomplished on the basis of this discovery.
Namely, the present invention provides a process for
producing a p-chlorobenzene having the formula:
R ~ Cl ~I)
wherein R is a lower al]cyl group, a lower alkoxy group or
a halogen atom, which comprises chlorinating a benzene
having the Eormula:
R ~ (II)
wherein R is as defined above. in a liquid phase in the
presence of a catalyst, characterized in that the
catalyst is a combination of an aliphatic alcohol having
the formula~
R'OH (III)
wherein R' is a lower alkyl group or a lower haloalk
-- 4
group, and a zeolite having a SiO2/A12O3 molar ratio of
from 3 to 8 and a pore siæe of Erom 6 to 10 A.
Now, the present invention will be described in
further detail with reference to -the preferred
embodiments.
The feature of the present invention is to use a
combination of a certain selected zeolite and a certain
selected aliphatic alcohol, as a catalyst, as a means to
solve the conventional problems.
Namely, in the process of the present invention, it
is essential to use, as a catalyst, a combination of a
zeolite having a SiO2/A12O3 molar ratio of from 3 to 8
and a pore size of from 6 to lO A, and an aliphatic
alcohol having the formula III.
The zeolite which satisfies such conditions, includes
L-type zeolite which is a crystalline aluminosilicate
having a SiO2/A12O3 molar ratio of from 4 to 8 and a pore
size of from 7 to lO A, and Y-type zeolite having a
SiO2/A12O3 molar ratio of fxom 3 to 7 and a pore size of
from 6 to 9 A. It is also possible to employ a synthetic
zeolite having the same X-ray diffraction spectrum as the
above-mentioned L~type or Y-type zeolite. Further, the
ion exchangeable cations contained in such zeolite are
usually sodium or po-tassium, but may further include
other cations. ~s such cations, there may be mentioned
metal ions or protons belonging to Group IA, Group IIA,
Group IIIA, Group IV~ or Group VA of the periodic table.
These cations may be of the same type or of two or more
different types.
If a zeolite having a SiO2/A12O3 molar ra-tio or a
pore size outside the above ranges, i.e. a zeolite other
than L-type zeolite and Y-type zeolite, is used as the
zeolite, the selectivity for p-chlorobenzenes will be
substantially reduced, and it is thereby impossible to
achieve the object of the present invention.
The aliphatic alcohol of the ~ormula III used as a
catalyst in the process o the present invention, may be
a C2 or C3 alkanol or haloalkanol, such as ethanol,
propanol, 2-chloroethanol, 2,2-dichloroethanol,
2,2,2-trichloroethanol, 2-bromoethanol, 2-fluoroethanol,
2,2,2-trifluoroethanol, 3 chloro-l-propanol,
2,3-dichloro-l-propanol, 3,3,2,2-tetrafluoro-l-propanol,
3,3,3,2,2-pentafluoro-1-propanol, or
1,1,1,3,3,3-hexafluoro-2-propanol. Particularly
preferred among them are 2-chloroethanol,
2,2-dichloroe-thanol, 3-chloro-1-propanol and
2,3-dichloro-1-propanol. The aliphatic alcohol is used
in an amount of at least 1% by weight relative to the
above-mentioned zeolite, and preferably in an amount oE
from 3 to 30% by weight relative to the zeolite.
If an alcohol other than the aliphatic alcohol of the
formula III, such as 6-chloro-l-hexanol, 2-chlorocyclo-
hexanol or phenol is used, the object oE the present
invention can hardly be accomplished ~see Comparative
Examples 2, 3 and ~ given hereinafter).
12~;2~2~
~n the present invention, a combination of the
above mentioned zeolite and the above-mentioned aliphatic
alcohol is employed. This combination may be made by
mixing the above-mentioned zeolite and the
above-mentioned aliphatic alcohol prior to the
chlorination reaction, or by adding the aliphatic alcohol
and the zeolite simultaneously to the reaction system at
the time of the chlorination reaction.
The preparation of the catalyst prior to the
chlorination may be conducted, for instance, by
suspending the above zeoli-te in a solvent, adding the
aliphatic alcohol thereto, distilling off the solvent and
any excess amount of the aliphatic alcohol and then
drying the residue under reduced pressure. In this case,
the zeolite may directly be added to the aliphatic
alcohol without using a solvent, followed by distilling
off the e~cess amount of the alcohol.
Whereas, in the case where the catalyst is prepared
at the time of the reaction, a predetermined amount oE
the zeolite is suspended in the startiny material benzene
charged in the chlorination apparatus, and then the
aliphatic alcohol is added thereto, and the mixture is
stirred at a temperature of not higher than the boiling
point, preferably from room temperature to lOQC, more
preferably from ~0 to 90 C, for about 30 minutes. Then,
a chlorinating agent is added, and the chlorination
reaction is conducted.
The benzene of the formula II used as the startiny
material in the process of the present invention,
includes compounds of the Eormula II wherein the
substituent R is a straight or branched lower alkyl such
as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl,
t-butyl or s~butyl or lower al~oxy group such as methoxy~
ethoxy or n-propoxy or a halogen atom such as a fluorine
atom, a chlorine atom or a bromine atom. It is
particularly preferred to employ a compound wherein R is
a methyl group or a chlorine atom, whereby the effects of
the present invention are most remarkable.
To conduct the chlorination of the benzene of the
formula II by the process of the presen-t invention, the
catalyst i.e. the combination of the aliphatic alcohol
and the zeolite, is added usually in an amount of from
0.01 to 10 g, preferably from 0.1 to 7 g, per mol of the
benzene of the formula II, and then a chlorinating agent
is introduced to conduct the reaction in a liquid phase
at a temperature of not higher than the boiling point of
the mixture, preferably from room temperature to 100C,
more preferably from 40 to 90C, under stirringO For
this reaction, a solvent may be employed, as the case
requires. However, no solvent is usually employed.
The chlorinating agent may be an agent which is
col~nonly used for the chlorination of an aromatic ring.
Preferably, chlorine or sulfuryl chloride is employed.
Particularly preferred is chlorine. Such a chlorinating
agent may be employed by diluting it with an inert gas
such as nitrogen, as the case requires.
The chlorination reaction may be conducted under
reduced pressure or under elevated pressure, bu-t is
usually conducted under atmospheric pressure.
According to the process of the present invention, it
is possible to selectively and efficiently chlorinate the
p-position of the benzene of the formula II while
supressing the chlorination at the o-position, and to
minimize the formation of by-products such as side chain-
chlorinated products or polychlorinated products, whereby
a highly useful p-chlorobenzene of the formula I can be
obtained in a high selectivity as compared with the
conventional methods, for instance, in a selectivity of
75% for p-chloroto~uene, or in a selectivity of 92% for
p-dichlorobenzene.
Further, according to the process of the present
invention, in a case where p-dichlorobenzene is to be
produced from chlorobenzene as the starting material, it
is possible to advantageously conduct the productlon o-f
chlorobenzene from benzene and the step of chlorinating
the chlorobenzene to p-dichlorobenzene, continuously in
the same reactor.
Furthermore, according to the process of the present
invention, the operation of the reaction and the
subsequent after-trea-tment are simple, and it is possible
to reuse the ca-talyst. Thus, the process of the present
invention is suitable as an industrial process for the
production of p-chlorobenzenes.
- 9 -
Now, the present invention will be described in
further detail with reference to Examples. However, it
should be understood that the present inven-tion is by no
means restricted by these specific Examples.
EXAMPLE l
Into a lO0 ml reaction flask equipped with a
condenser, a thermome-ter, a stirrer and a gas supply
tube, 2.5 g of L-type zeolite ~TSZ-506, trade~am~,
manufactured by Toyo Soda Manufacturing Co., Ltd.) and
46.1 g (0.5 mol) of toluene were introduced, and 0.5 g of
2-chloroethanol was added thereto. The mixture was
maintained at 70C, and stirred for 30 minutes while
supplying nitrogen gas. Then, chlorine gas was supplied
at a rate of 0.125 mol/hr for 3.6 hours to conduct the
reaction while maintaining the reaction temperature at
70C. After the completion of the reaction, the reaction
product thereby obtained, was analyzed by gas
chromatography, whereby it was found that the conversion
oE toluene was 87.6~, the production ratio of
o-chlorotoluene/p~chlorotoluene (hexeinafter referred to
simply as "o/p ratio") was 0.298, and the selectivity for
p-chlorotoluene relative to the total amount of the
reaction product was 75~.
EXAMPLE 2
The reaction as in Example l was repeated by using
the same catalyst again, whereby the conversion of
toluene was 88.2~ and the o~p ratio was 0.299.
- 10 ~
EXAMPLRS 3 to 6 and COMPARATIVE EXAMPLES 1 to 4
The haLogenation was conducted a-t 70C in the same
manner as in Example l except that various alcohols were
used instead of 2-chloroethanol. The results are shown
in Table 1.
For the purpose of comparison, the results obtained
in the ca~e where L-type zeolite was used alone as the
so]e catalyst, are also given.
Table l
Conver- O/P Selectivity
Alcohols sion ratio for p-chloro-
(%) _benzene (%)
Example 3 2,3-Dichloro-l 89.4 0.387 70
propanol
Example 4 2,2-Dichloroethanol 89.6 0.342 73
Example 5 3~Chloro-l-propanol 87.4 0.341 69
Example 6 Propanol B8.5 0.453 67
Compara-
tive None 87.9 0.5 63
Exarnple 1
_ I
Compara-
tive 6-Chloro-l-hexanol 87.7 0~522 60
Example 2
Compara-
tive 2-Chlorocyclo- 82.6 0.440 61
Example 3 hexanol
Compara-
tive Phenol 85.0 0.510 62
Example 4 __ _
~26~Z~
-- 11 --
E~AMPLES 7 to 9
The chlorination was conducted in the same manner as
in Example l except that the reaction temperature was
changed. The results are shown in Table 2.
Table 2
_ Conver- o/p Selectiv-
E~a ~ Aliphatic alcohols Te~p slon ratio ~ ne
2-Chloroethanol 50 C 89.8 0.317 69.3
8 2-Chloroethanol 65C 89.6 0.301 74.3
_
2-Chloroethanol 90C 89.5 0.350 71.3
EXAMPLES 10 to 13 and COMPARATIVE EXAMPLES 5 to 8
The chlorination was conducted in the same manner as
in Example 1 excep-t that toluene was changed to other
benzenes. For the purpose of comparison, the results
obtained in the case where L-type zeolite was used alone
as the sole catalyst, are also given.
- 12 ~
Table 3
_ Conver- /P Selectivity
Benzene sion ratio for p-chloro-
(%) benzene (%)
. _
Example 10 Chlorobenzene 74.7 0.076 93
__
Comparative Chlorobenzene 73.5 0.12 87
Example 5
_ __
Example 11 Cumene 81.5 0.215 77
Comparative Cumene 81.0 0.26 72
Example 6
_ _ _
Example 12 Anisole 89.5 0.194 '78
Comparative Anisole 88.7 0.21 75
Example 7
Example 13 t-Butylbenzene 84.1 0.031 91
_
Comparative t-Butylbenzene 83.5 0.06 82
Example 8 _
