CA1080752A - Process for the continuous manufacture of o- and p-chlorotoluene - Google Patents
Process for the continuous manufacture of o- and p-chlorotolueneInfo
- Publication number
- CA1080752A CA1080752A CA259,016A CA259016A CA1080752A CA 1080752 A CA1080752 A CA 1080752A CA 259016 A CA259016 A CA 259016A CA 1080752 A CA1080752 A CA 1080752A
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- Canada
- Prior art keywords
- toluene
- chlorine
- chlorination
- catalyst
- reaction
- Prior art date
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C17/00—Preparation of halogenated hydrocarbons
- C07C17/093—Preparation of halogenated hydrocarbons by replacement by halogens
- C07C17/10—Preparation of halogenated hydrocarbons by replacement by halogens of hydrogen atoms
- C07C17/12—Preparation of halogenated hydrocarbons by replacement by halogens of hydrogen atoms in the ring of aromatic compounds
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- Organic Chemistry (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)
Abstract
PROCESS FOR THE CONTINUOUS MANUFACTURE OF O- AND P-CHLOROTOLUENE
Abstract of the disclosure:
o- and p-chlorotoluene is obtained at practically quantitative yields and excellent quality by continuous chlorination of toluene at a molar number ratio of chlorine to toluene of about 0.4 to 1 and at a temperature of about 5 -70°C, in the presence of at least one catalyst being known for such nuclear chlorination reactions, in a parallel current while mixing thoroughly; after completion of the reaction the reaction mixture is freed by distillation from hydrochloric acid and from non-reacted toluene, and the remaining distillation residue is separated immediately to yield the isomeric o- and p-chlorotoluenes.
Side-chain chlorination is practically avoided at all by this process, so that cumbersome purification operations such as the removal of chlorine linked to the side chain by boiling under pressure with alkali base may be dispensed with. The chlorotoluenes are partially utilized as solvents, partially as intermediate products e.g. for the manufacture of plant protection agents.
Abstract of the disclosure:
o- and p-chlorotoluene is obtained at practically quantitative yields and excellent quality by continuous chlorination of toluene at a molar number ratio of chlorine to toluene of about 0.4 to 1 and at a temperature of about 5 -70°C, in the presence of at least one catalyst being known for such nuclear chlorination reactions, in a parallel current while mixing thoroughly; after completion of the reaction the reaction mixture is freed by distillation from hydrochloric acid and from non-reacted toluene, and the remaining distillation residue is separated immediately to yield the isomeric o- and p-chlorotoluenes.
Side-chain chlorination is practically avoided at all by this process, so that cumbersome purification operations such as the removal of chlorine linked to the side chain by boiling under pressure with alkali base may be dispensed with. The chlorotoluenes are partially utilized as solvents, partially as intermediate products e.g. for the manufacture of plant protection agents.
Description
~ ~ HOE 75/F 751 ~ '7t~
Little is known so far about test results of the manufacture of o- and p-chlorotoluene on an industrial scale. It is Xnown however, that o- and p-chlorotoluene may be prepared hy reacting toluene and chLorine, and various catalysts for this nuclear ~hl^ri..ation ~eactio.. have ke2n descr ~ed, lor exar,plc erlous halides. The purpose of influencing the ratio of o- and p-isomers obtainable upon chlorination of toluene may further be served by adding sulfur or inorganic and organic sulfur eompounds. In order to reach high portions of o-chlorotoluene in the chlorination mixture, there have also been used as cata-lysts chlorides of various metals, e.g. Ti, Tl, Sn, Zr and W.
Also known is the chlorination of toluene in the counter-eurrent, as well as the chlorination at elevated temperature (up to 150C) and the chlorination in the presence of an aqueous phase.
All industrial processes hitherto known are based essen-tlally on applying discountinuous chlorination methods. Accord-ing to Houben Weyl, Methoden der Organischen Chemie, Vol. V/3 (1962) 658, for example, the chlorination of toluene with 2Q- chlorine at a temperature of from 15 to 25C as a charge yields about 76 % of a mixture of o- and p~chlorotuluene. The crude product is advantageously washed with highly concentrated aqueous sodium hydroxide solution (at 43 %), an operation step which allows for dispensing with a separate drying of the ehlorination mixture prior to an optionally subsequent fractional distallationl -~hough this latter step is otherwise necessary for avoiding corrosion of industrial fractionating plants. More-over, so as to eliminate chlorine linked to the side chain, the 29 crude product has to be boiled thoxoughly under pressure with ' .. _ . ... , . . ~
~ 7~2 HO~ 75/F i51 alkali base.
Furthermore, according to BIOS Final Repor~ no. 1145 toluene is chlorinated discontinuously at 30C up t~ a densit~
of 1.~6, a batch of from 4 to 5 to needing a reaction time of about 50 hours. At ~h~ com.ple'ion of the chlorinat~.on re~c'ion , the reaction mixture is freed from the dissolved hydrogen chloride to a large extent by blowing off with air. Prior to fractionation to yield the isomeric chlorotoluenes, the crude product h~s to be kept in an autoclave for 2~ hours with sodium hydroxide solution ana heated to 120C, in order to eliminate the content in chlorine linked to the side chain, an operational step which is appropriate for avoiding resinifica-tions of the product and damages due to corrosion during thedistillation.
Continuous toluene-chlorination processes could not avoid either the formation of side-chain chlorinated by-products (cf. German Auslegeschrift 1 543 020).
The state of the art shows that an economically reason-able processing method of crude chlorotoluene, which had been 20- prepared according to know~ processes, to yield pure isomeric o- and p-chlorotoluenes cannot be achieved on an industrial scale without washing and purifying operations for eliminating hydrogen chloride from the c~ude chlorination mixture, nor without washing under pressure with alk.ali base for eliminating chlorine lirl~ed to the side chain. Tnus, the separation of isomers hy fractional distillation on an industrial scale may be carried out only in case of crude chlorination mixtU~es which have been pre-purified in the above described manner, 29 after the first runnings consisting of polluted toluene have , .
.. .
, ` , , ' ~ '.
, ~ HOE 75/F 751 Z
been evacuated, the mixtùre is slowly separated in o- resp.
p-chlorotoluene-ric~ fractio~s which finally allow for isolating the individual components. The first runnings cannot be recycled into the chlorination. According to the statements given in llmann, ~nzyklopadie der Technischen Chemie, 3rd edition ~ol. 5, page 468, the separation of isomeric chlorotoluenes is described as difficult on an industrial scale.
; It has now been found, surprisingly, that toluene and chlorine may be reacted continuously in the presence of catalysts to yield chlorotoluenes without any formation of by-products, - which presence could hamper a later processing of the crude chlorination mixture to yield the pure isomeric chlorotoluenes, so that such by products would necessitate to submit the ; chlorination mixture to additional washing and purifying operations and/or to boiling under pressure with aqueous alkali hydroxide.
There~ore, the present invention is related to a process for the continuous manufacture of o- and p-chlorotoluene by nuclear chlorination of toluene with chlorine in the presence 20- of catalysts, compr~sing the reaction of toluene and chlorine at a molar number ratio of chlorine: toluene or 0.4 to 1.0, preferably of 0.6 to 0.9, at a temperature of from 5 to 70C, preferably from 15 to 4~C, in the presence of at least one catalyst in a parallel current while mixing thoroughly in a reaction zone, after co~pletion of the reaction ~he chlorina-tion mi~ture is submitted to distillation to eliminate hydrogen chloride and non-reacted toluene and to separate the sump product by distillation to yield immediate]y the isomeric o-29 and p-chlorotoluenes.
--~ HOE 75/F 751 As catalysts are employed the nuclear chlorinatiGn catalysts usually utilized for the chlorination of toluene, as well as catalysts which help influence the isomer ratio of the chlorotoluenes which are formed dwring the chlorination reaction.
There are also utilized combinations of these catalysts, e.g.
metal halides, preferably ferrous halides and especially ferrous chloride (FeCl3). Same may either be added immediately to the reaction mixture or they are added already to the toluene.
Furthermore, it is possible to utilize e.g. sulfur or~ sulfur ~ S~/~S
1 ~ compounds for increasing the p-isomer portion, eul~srouc~
chloride (S2Cl2) being preferred, especially as co-catalyst combined with a ferrous chloride - catalyst. Upon utilization of catalyst combinations the components may be added separately or as a mixture.
The process according to the invention provides for utilizing the catalysts and the co-catalysts at rates of ; generally from about 5 to about 100 ppm, preferably from 10 to 40 ppm, especially from 15 to 30 ppm. calculated on the quantity of toluene employed. The ratio of o~/p- chlorotoluene, which can be achieved according to the invention, may vary within the usual limits, for example from about 2 : 1 to about 1 : 1.
An especially preferred embodiment of the process according to the invention comprises that the ferrous chloride catalyst i5 prepared continuously of iron and the components of the reaction mixture in situ immediately in the reaction mixture, preferably in the reaction zone, proportionally to the con-sumption. This operation is easily carried out by the simple presence of metallic iron in the reaction mixture, for example 29 by utilizing iron wall panels and/or preferably lron fillers in ', ', ` '' `, `
37S~
the reactor which is formin~ the reaction zone, p~eferably making sure that the humidity in the reaction mixture is kept very low so as to avoid any corrosion and increased formation of ferrous chloride, which could possibly hamper the further treatment of the chlorination mixture. According to the invention the necessary low water content in the reaction mixture may be achieved by maintaining the water content of the toluene employed for the chlorination at a maximum of 0.03 weight %, preferably at from 0.001 to 0.025 and especially from 0.01 to 0.02 weight %, at the exclusion of further humidity factors.
Since industrial toluene may contain variable quantities of moisture, for example generally from about 0.05 to about 0.07 weight %, and since the solubility of water in toluene within the temperature range of the chlorination reaction according to the invention surpasses already the low water content required as per the invention and increases further with increasing temperature, it is recommendable to dry toluene prior to its use for the chlorination. Such a drying step may be carried out by adding dehydrating salts, or prefer-ably by dry hydrogen chloride gas such as it occurs as by-product during chlorination reactions. In the present case of a continuous chlorination of toluene it is possible to utilize the hydrogen chloride, being obtained continuously upon processing the chlorination mixture as per the invention, immediately for drying toluene, a preferred embodiment establishing an intimate contact between toluene and the dry hydrogen chloride gas in a countercurrent, so that dry toluene may be obtained, the water content of which corresponds to the 29 requirement of the invention. The water possibly included in the .. -- 6 --108V ~5Z HOE ?5!F 751 crude toluene is forming hydrochloric acid with the hydrogen chloride, this hydrochloric acid being either evacuated or separated together with the excessive hydrogen chloride gas, which latter may be transformed subsequently, e.g. with water, by m.ean~ of adiaba~ic absurption to yieid saieable conce~trated hydrochloric acid of industrial quality.
The operations of drying toluene and separating the crude reaction mixture freed from hydroyen chloride and non--reacted toluene may be carried out discountinuously as well. However, in both cases preference is given to carrying out said process-ing steps in a continuous manner.
The process according to the invention is illustrated by the following scheme and the Example: -Crude toluene is introduced, possibly being pre-cooled to about 0 to 10C, through the feed-line (1) into the toluene dryer (2), through which dry hydrogen chloride gas possibly charged with toluene vapor is flowing through the feed-line (3~, the hydrogen chloride binding the water optionally contained in the crude toluene. Via the line (4) dry toluene, the water content of which amounts to maximum 0.03 weight %, reaches the chlorination device (5) which is forming the reaction zone, while simultaneously through feed-line (6) in a parallel current chlorine is metered into the chlorination device (S) at a molar number ratio to toluene according to the invention, this chlorine being preferably in the gaseous state and as such taking care of simultaneously mixing thoroughly the reaction mixture.
Inside the chlorination device toluene and chlorine, in the presence of the catalyst - pre~erably iron-(III) chloride - and 29 possibly of co-catalysts, are reacting within the temperature .,.. - ~ .
' , ~
:: " ' '~ . ' ' . ' ' ' .:
, ~ 5~ }IOE 75/F 751 ; range of the invention while ~orming crude chlorotoluene and hydrogen chloride, the chlorine being practically reacted quantitatively, so that the reaction mixture does not contain any free chlorine after h~ving left the reaction zone.
The react i on he;-.t may be remo~.7ed h~" _ Sll i t?hl e cool i ng system in the chlorination device and/or by evaporation of toluene. Reaction temperatures above 70C are also possible, but they do not contribute any special advantage, since such elevated temperatures may favor the formation of undesirable by-products. As well may be conceived temperatures below 5C, but the reaction speed becomes very slow in that case.
The catalyst and/or the co-catalyst are possibly metered into the chlorination device through the feed-line (7). A
preferred embodiment of the process according to the invention which utilizes ferrous chloride as a catalyst, does not provide for metering same in as a substance, but to produce same continuously directly from iron and from components of the ; reaction mixture in situ in the chlorination device. The necessary iron may be charged, for example, either as a loose charge of Raschig rings or as iron wire spirals or as steel sheets inside the chlorination device, wherein the iron is slowly reacting to FeCl3 and providing continuously the required nuclear chlorination catalyst. The iron content, such as it is absorbed by the reaction mixture e.g. from the iron Raschig rings pre-charged into the chlorination device, while forming ferrous chloride, may reach e.g. about 15 to 20 ppm. The iron contènt may possibly be completed by an additional supply of co-catalysts, such as S2Cl2. The sulfur content in the reaction 29 mixture resulting from S2Cl2 may amount e.g. to about 15 to ~. .. .
- .
: .
'' : ' ~ , . :' ' . ' ': ' ~ 7S~ HOE 75/F 751, 20 ppm.
The simplest form of chlorination device (5) may consist of a flow tube with a cooling device. Industrial plants preferr however, the use of column-like double-casing reactors. As a suLficien~ly corrosion-resisiant material for the chlorlnation device may be employed preferably standard steel such as e.g.
St 35 or boiler plate HI. In some cases the reactor walls may advantageously be lined with different corrosion resistant materials in certain areas of the iron filler charge. An efficient removal of the reaction heat being important for maintaining the reaction temperature according to the invention, the required residence time of the reaction mixture in the chlorination device may be essentially influenced by the way of heat removal. Thus, in the case of industrial chlorination 1~ devices with jacket cooling, the residence time may reach, e.g.
in a 10 cbm reactor, up to 15 hours, especially from 8 to 12 hours.
After completion of the reaction the crude chlorination mixture and the newly formed hydrogen chloride gas are conducted through the line (8) into the distillin~ column ~
wherein the not yet chlorinated toluene - together with the hydrochloric acid gas - is distilled off on top (10) and where-in the crude chlorotoluene in the sump including possibly present by-products and dissolved catalyst portions are evacuated through line (11) and fed into a vacuum column (12).
The top product of the distilling column (9) is condensed in a cooling device (13), possibly in various steps, the toluene being partially fed back through line (1~) into the 29 distillation (9) resp. through line (3) - together wit~ hydro-... .. .
'~'., ' - ~ ' ':
- . .
~ HOE 75/F 7~1 chloric acid gas - into the toluene dryer (2), where the hydrochloric acid gas is utilized in the above described manner for drying the crude toluene, reaching subsequently the absorber (16) through line (15) for being then transformed wi~h water (17) to yield saleable hydrochloric acid ~18! h~ mean.s of adiabatic absorption. The vaporous mixture of water and toluene, which is evacuated from the absorption column (16) on top, is condensend in a heat-exchanger (19) , the components of the condensate are separated in a separating device (20), and the isolated toluene fed back into the toluene dryer 12), whilst the water is fed back into the absorber (16).
In a vacuum column t12) the isomeric chlorotoluene mixture is isolated from the sump product of the distilling column (9) of the higher boiling and solid residues being evacuated as sump product through the line (21), then possibly liquified in a condensor (22) and/or, optionally without any intermediary condensation, introduced into a o-/p- chlorotoluene vacuum fractionating column (23), wherein p-chlorotoluene (24) is evacuated from the sump, and on top of which o-chlorotoluene 20 ~ (26) can be removed through a condensor l25). Isolativn and thorough purification of p-chlorotoluene can also be carried out by crystallization.
The pressure during the chlorination reaction according to the invention is not critical; preference is, however, given to atmospherical pressure. Pressures above or below this level are possible, but generally do not contribute any advantage. Most usefully the pressure should be adjusted in such a W~r that the chlorine is maintained in gaseous state at the given reaction 29 temperature.
, : :
.
- : . , , , : .
.
.
.: .: , ~ . . ' :.
- HOE 7~/F 751 As described above, the reaction of the chlorine utilized according to the invention is practically quantitative. The yields in monoch]orotoluene - calculated on the quantity of chlorine employed - are extremely high. If the molar number ratio of chlorine: toluene and/or the reaction temperature are maintained each in the lower area according to the invention, there occurs practically no formation of dichlorotoluene at all and the formation of monochlorotoluene reaches almost the theoretical quantities, calculated on the chlorine employed.
The process of the present invention requires furthermore surprisingly low catalyst quantities. Thus, the present inven-tion enables for the first time to manufacture continuously and by surprisingly simple technology very good yields of high-~uality o- and p-chlorotoluene. The highly economical and doubtlessly very progressive technology of the continuous process according to the invention resides especially in the fact that there may be surprisingly dispensed with the following disadvatages of known processing methods.Purification steps were required prior to separating the crude chlorination 20 ~ mixture,such as elimination of possibly non-reacted chlorine, washing out hydrogen chloride, removal of unstable chlorine ~inked to the side-chain by means of boiling under pressure with alkali base, drying the crude product with solid drying a~ents prior to fractionating and possibly the use of an expensive ma-terial for the chlorination device which may be necessary for preventing corrosion.
Moreover, the complete absence of any emission problems recommends the process of the invention for its lack of stress 29 on the environment.
~ . . . . . . .
'. ' ' - ' ' . ~ ', ~ ' ' : ,. . .
.
. . ' ' ~ ~
` HOE 75/F 751 The monochlorotoluenes submitted to nuclear chlorination are partially utilized as solvents, partially as startiny or intermediary products, e.g. for the manufacture of plant protec-; tion agents.
E X A_M P L E
The chlorination is carried out in a scheme corresponding to the industrial chlorination plant as per the illustration with a cylinder-shaped reactor (5) about 8 m high and having a diameter of about 1.4 m, being charged with about 5 cbm of cylindrical hollow steel bodies (measuring about 35 mm length, 35 mm dia-meter and 1 mm thickness), toluene and chlorine gas being continuously fed into the reactor and the crude reaction product flowing continuously off the reactor through line (8) proportionally to the supply of the starting products. The reactor is supplied with 13.66 to/day of toluene (water content less than 0.03 weight %j 2862 Ncbm/day "chlorine gas and abt. 700 g/day" S2C12 The temperatureinside the reactor is about 30C. The quantity of chlorine supplied amounts to approximately 80 % of the stolchiometrically necessary quantity of chlorine. The ` residence time of the reaction mixture in the reactor reaches about 15 hours.
The liquid crude reaction product flowing off the reactor at the rate of 17.78 to/day consists of 2.73 to/day of non~
reacied toluene and of 15.0 to/day of crude chlorotoluene;
additionally are formed 2862 Ncbm/day of h~-drochloric acid.
The crude chlorotoluene freed from hydrogen chloride and ~9 non-reacted toluene has the following composition (in weight ~):
, . , ' : : ' :
. .
. . . . .
~ 7 ~ HOE 75/~ 751 :
o-chlorotoluene 49.0 weight %
m-chlorotoluene~ 0.2 weight %
p-chlorotoluene 48.0 weight %
benzyl chloride 0 weight %
dichlorotoluenes2.8 weight %
The analytical definition of the products was carried out by gas chromatography, the yield was determined by weighing.
The total yield of o-and p-chlorotoluene, calculated on reac~ed toluene, surpasses 97 % of the theoretical yield. The chlorine fed in undergoes a practically quantitative reaction.
.
,--.
~- ,, ' ' . . ' .
.
' . ~ ,
Little is known so far about test results of the manufacture of o- and p-chlorotoluene on an industrial scale. It is Xnown however, that o- and p-chlorotoluene may be prepared hy reacting toluene and chLorine, and various catalysts for this nuclear ~hl^ri..ation ~eactio.. have ke2n descr ~ed, lor exar,plc erlous halides. The purpose of influencing the ratio of o- and p-isomers obtainable upon chlorination of toluene may further be served by adding sulfur or inorganic and organic sulfur eompounds. In order to reach high portions of o-chlorotoluene in the chlorination mixture, there have also been used as cata-lysts chlorides of various metals, e.g. Ti, Tl, Sn, Zr and W.
Also known is the chlorination of toluene in the counter-eurrent, as well as the chlorination at elevated temperature (up to 150C) and the chlorination in the presence of an aqueous phase.
All industrial processes hitherto known are based essen-tlally on applying discountinuous chlorination methods. Accord-ing to Houben Weyl, Methoden der Organischen Chemie, Vol. V/3 (1962) 658, for example, the chlorination of toluene with 2Q- chlorine at a temperature of from 15 to 25C as a charge yields about 76 % of a mixture of o- and p~chlorotuluene. The crude product is advantageously washed with highly concentrated aqueous sodium hydroxide solution (at 43 %), an operation step which allows for dispensing with a separate drying of the ehlorination mixture prior to an optionally subsequent fractional distallationl -~hough this latter step is otherwise necessary for avoiding corrosion of industrial fractionating plants. More-over, so as to eliminate chlorine linked to the side chain, the 29 crude product has to be boiled thoxoughly under pressure with ' .. _ . ... , . . ~
~ 7~2 HO~ 75/F i51 alkali base.
Furthermore, according to BIOS Final Repor~ no. 1145 toluene is chlorinated discontinuously at 30C up t~ a densit~
of 1.~6, a batch of from 4 to 5 to needing a reaction time of about 50 hours. At ~h~ com.ple'ion of the chlorinat~.on re~c'ion , the reaction mixture is freed from the dissolved hydrogen chloride to a large extent by blowing off with air. Prior to fractionation to yield the isomeric chlorotoluenes, the crude product h~s to be kept in an autoclave for 2~ hours with sodium hydroxide solution ana heated to 120C, in order to eliminate the content in chlorine linked to the side chain, an operational step which is appropriate for avoiding resinifica-tions of the product and damages due to corrosion during thedistillation.
Continuous toluene-chlorination processes could not avoid either the formation of side-chain chlorinated by-products (cf. German Auslegeschrift 1 543 020).
The state of the art shows that an economically reason-able processing method of crude chlorotoluene, which had been 20- prepared according to know~ processes, to yield pure isomeric o- and p-chlorotoluenes cannot be achieved on an industrial scale without washing and purifying operations for eliminating hydrogen chloride from the c~ude chlorination mixture, nor without washing under pressure with alk.ali base for eliminating chlorine lirl~ed to the side chain. Tnus, the separation of isomers hy fractional distillation on an industrial scale may be carried out only in case of crude chlorination mixtU~es which have been pre-purified in the above described manner, 29 after the first runnings consisting of polluted toluene have , .
.. .
, ` , , ' ~ '.
, ~ HOE 75/F 751 Z
been evacuated, the mixtùre is slowly separated in o- resp.
p-chlorotoluene-ric~ fractio~s which finally allow for isolating the individual components. The first runnings cannot be recycled into the chlorination. According to the statements given in llmann, ~nzyklopadie der Technischen Chemie, 3rd edition ~ol. 5, page 468, the separation of isomeric chlorotoluenes is described as difficult on an industrial scale.
; It has now been found, surprisingly, that toluene and chlorine may be reacted continuously in the presence of catalysts to yield chlorotoluenes without any formation of by-products, - which presence could hamper a later processing of the crude chlorination mixture to yield the pure isomeric chlorotoluenes, so that such by products would necessitate to submit the ; chlorination mixture to additional washing and purifying operations and/or to boiling under pressure with aqueous alkali hydroxide.
There~ore, the present invention is related to a process for the continuous manufacture of o- and p-chlorotoluene by nuclear chlorination of toluene with chlorine in the presence 20- of catalysts, compr~sing the reaction of toluene and chlorine at a molar number ratio of chlorine: toluene or 0.4 to 1.0, preferably of 0.6 to 0.9, at a temperature of from 5 to 70C, preferably from 15 to 4~C, in the presence of at least one catalyst in a parallel current while mixing thoroughly in a reaction zone, after co~pletion of the reaction ~he chlorina-tion mi~ture is submitted to distillation to eliminate hydrogen chloride and non-reacted toluene and to separate the sump product by distillation to yield immediate]y the isomeric o-29 and p-chlorotoluenes.
--~ HOE 75/F 751 As catalysts are employed the nuclear chlorinatiGn catalysts usually utilized for the chlorination of toluene, as well as catalysts which help influence the isomer ratio of the chlorotoluenes which are formed dwring the chlorination reaction.
There are also utilized combinations of these catalysts, e.g.
metal halides, preferably ferrous halides and especially ferrous chloride (FeCl3). Same may either be added immediately to the reaction mixture or they are added already to the toluene.
Furthermore, it is possible to utilize e.g. sulfur or~ sulfur ~ S~/~S
1 ~ compounds for increasing the p-isomer portion, eul~srouc~
chloride (S2Cl2) being preferred, especially as co-catalyst combined with a ferrous chloride - catalyst. Upon utilization of catalyst combinations the components may be added separately or as a mixture.
The process according to the invention provides for utilizing the catalysts and the co-catalysts at rates of ; generally from about 5 to about 100 ppm, preferably from 10 to 40 ppm, especially from 15 to 30 ppm. calculated on the quantity of toluene employed. The ratio of o~/p- chlorotoluene, which can be achieved according to the invention, may vary within the usual limits, for example from about 2 : 1 to about 1 : 1.
An especially preferred embodiment of the process according to the invention comprises that the ferrous chloride catalyst i5 prepared continuously of iron and the components of the reaction mixture in situ immediately in the reaction mixture, preferably in the reaction zone, proportionally to the con-sumption. This operation is easily carried out by the simple presence of metallic iron in the reaction mixture, for example 29 by utilizing iron wall panels and/or preferably lron fillers in ', ', ` '' `, `
37S~
the reactor which is formin~ the reaction zone, p~eferably making sure that the humidity in the reaction mixture is kept very low so as to avoid any corrosion and increased formation of ferrous chloride, which could possibly hamper the further treatment of the chlorination mixture. According to the invention the necessary low water content in the reaction mixture may be achieved by maintaining the water content of the toluene employed for the chlorination at a maximum of 0.03 weight %, preferably at from 0.001 to 0.025 and especially from 0.01 to 0.02 weight %, at the exclusion of further humidity factors.
Since industrial toluene may contain variable quantities of moisture, for example generally from about 0.05 to about 0.07 weight %, and since the solubility of water in toluene within the temperature range of the chlorination reaction according to the invention surpasses already the low water content required as per the invention and increases further with increasing temperature, it is recommendable to dry toluene prior to its use for the chlorination. Such a drying step may be carried out by adding dehydrating salts, or prefer-ably by dry hydrogen chloride gas such as it occurs as by-product during chlorination reactions. In the present case of a continuous chlorination of toluene it is possible to utilize the hydrogen chloride, being obtained continuously upon processing the chlorination mixture as per the invention, immediately for drying toluene, a preferred embodiment establishing an intimate contact between toluene and the dry hydrogen chloride gas in a countercurrent, so that dry toluene may be obtained, the water content of which corresponds to the 29 requirement of the invention. The water possibly included in the .. -- 6 --108V ~5Z HOE ?5!F 751 crude toluene is forming hydrochloric acid with the hydrogen chloride, this hydrochloric acid being either evacuated or separated together with the excessive hydrogen chloride gas, which latter may be transformed subsequently, e.g. with water, by m.ean~ of adiaba~ic absurption to yieid saieable conce~trated hydrochloric acid of industrial quality.
The operations of drying toluene and separating the crude reaction mixture freed from hydroyen chloride and non--reacted toluene may be carried out discountinuously as well. However, in both cases preference is given to carrying out said process-ing steps in a continuous manner.
The process according to the invention is illustrated by the following scheme and the Example: -Crude toluene is introduced, possibly being pre-cooled to about 0 to 10C, through the feed-line (1) into the toluene dryer (2), through which dry hydrogen chloride gas possibly charged with toluene vapor is flowing through the feed-line (3~, the hydrogen chloride binding the water optionally contained in the crude toluene. Via the line (4) dry toluene, the water content of which amounts to maximum 0.03 weight %, reaches the chlorination device (5) which is forming the reaction zone, while simultaneously through feed-line (6) in a parallel current chlorine is metered into the chlorination device (S) at a molar number ratio to toluene according to the invention, this chlorine being preferably in the gaseous state and as such taking care of simultaneously mixing thoroughly the reaction mixture.
Inside the chlorination device toluene and chlorine, in the presence of the catalyst - pre~erably iron-(III) chloride - and 29 possibly of co-catalysts, are reacting within the temperature .,.. - ~ .
' , ~
:: " ' '~ . ' ' . ' ' ' .:
, ~ 5~ }IOE 75/F 751 ; range of the invention while ~orming crude chlorotoluene and hydrogen chloride, the chlorine being practically reacted quantitatively, so that the reaction mixture does not contain any free chlorine after h~ving left the reaction zone.
The react i on he;-.t may be remo~.7ed h~" _ Sll i t?hl e cool i ng system in the chlorination device and/or by evaporation of toluene. Reaction temperatures above 70C are also possible, but they do not contribute any special advantage, since such elevated temperatures may favor the formation of undesirable by-products. As well may be conceived temperatures below 5C, but the reaction speed becomes very slow in that case.
The catalyst and/or the co-catalyst are possibly metered into the chlorination device through the feed-line (7). A
preferred embodiment of the process according to the invention which utilizes ferrous chloride as a catalyst, does not provide for metering same in as a substance, but to produce same continuously directly from iron and from components of the ; reaction mixture in situ in the chlorination device. The necessary iron may be charged, for example, either as a loose charge of Raschig rings or as iron wire spirals or as steel sheets inside the chlorination device, wherein the iron is slowly reacting to FeCl3 and providing continuously the required nuclear chlorination catalyst. The iron content, such as it is absorbed by the reaction mixture e.g. from the iron Raschig rings pre-charged into the chlorination device, while forming ferrous chloride, may reach e.g. about 15 to 20 ppm. The iron contènt may possibly be completed by an additional supply of co-catalysts, such as S2Cl2. The sulfur content in the reaction 29 mixture resulting from S2Cl2 may amount e.g. to about 15 to ~. .. .
- .
: .
'' : ' ~ , . :' ' . ' ': ' ~ 7S~ HOE 75/F 751, 20 ppm.
The simplest form of chlorination device (5) may consist of a flow tube with a cooling device. Industrial plants preferr however, the use of column-like double-casing reactors. As a suLficien~ly corrosion-resisiant material for the chlorlnation device may be employed preferably standard steel such as e.g.
St 35 or boiler plate HI. In some cases the reactor walls may advantageously be lined with different corrosion resistant materials in certain areas of the iron filler charge. An efficient removal of the reaction heat being important for maintaining the reaction temperature according to the invention, the required residence time of the reaction mixture in the chlorination device may be essentially influenced by the way of heat removal. Thus, in the case of industrial chlorination 1~ devices with jacket cooling, the residence time may reach, e.g.
in a 10 cbm reactor, up to 15 hours, especially from 8 to 12 hours.
After completion of the reaction the crude chlorination mixture and the newly formed hydrogen chloride gas are conducted through the line (8) into the distillin~ column ~
wherein the not yet chlorinated toluene - together with the hydrochloric acid gas - is distilled off on top (10) and where-in the crude chlorotoluene in the sump including possibly present by-products and dissolved catalyst portions are evacuated through line (11) and fed into a vacuum column (12).
The top product of the distilling column (9) is condensed in a cooling device (13), possibly in various steps, the toluene being partially fed back through line (1~) into the 29 distillation (9) resp. through line (3) - together wit~ hydro-... .. .
'~'., ' - ~ ' ':
- . .
~ HOE 75/F 7~1 chloric acid gas - into the toluene dryer (2), where the hydrochloric acid gas is utilized in the above described manner for drying the crude toluene, reaching subsequently the absorber (16) through line (15) for being then transformed wi~h water (17) to yield saleable hydrochloric acid ~18! h~ mean.s of adiabatic absorption. The vaporous mixture of water and toluene, which is evacuated from the absorption column (16) on top, is condensend in a heat-exchanger (19) , the components of the condensate are separated in a separating device (20), and the isolated toluene fed back into the toluene dryer 12), whilst the water is fed back into the absorber (16).
In a vacuum column t12) the isomeric chlorotoluene mixture is isolated from the sump product of the distilling column (9) of the higher boiling and solid residues being evacuated as sump product through the line (21), then possibly liquified in a condensor (22) and/or, optionally without any intermediary condensation, introduced into a o-/p- chlorotoluene vacuum fractionating column (23), wherein p-chlorotoluene (24) is evacuated from the sump, and on top of which o-chlorotoluene 20 ~ (26) can be removed through a condensor l25). Isolativn and thorough purification of p-chlorotoluene can also be carried out by crystallization.
The pressure during the chlorination reaction according to the invention is not critical; preference is, however, given to atmospherical pressure. Pressures above or below this level are possible, but generally do not contribute any advantage. Most usefully the pressure should be adjusted in such a W~r that the chlorine is maintained in gaseous state at the given reaction 29 temperature.
, : :
.
- : . , , , : .
.
.
.: .: , ~ . . ' :.
- HOE 7~/F 751 As described above, the reaction of the chlorine utilized according to the invention is practically quantitative. The yields in monoch]orotoluene - calculated on the quantity of chlorine employed - are extremely high. If the molar number ratio of chlorine: toluene and/or the reaction temperature are maintained each in the lower area according to the invention, there occurs practically no formation of dichlorotoluene at all and the formation of monochlorotoluene reaches almost the theoretical quantities, calculated on the chlorine employed.
The process of the present invention requires furthermore surprisingly low catalyst quantities. Thus, the present inven-tion enables for the first time to manufacture continuously and by surprisingly simple technology very good yields of high-~uality o- and p-chlorotoluene. The highly economical and doubtlessly very progressive technology of the continuous process according to the invention resides especially in the fact that there may be surprisingly dispensed with the following disadvatages of known processing methods.Purification steps were required prior to separating the crude chlorination 20 ~ mixture,such as elimination of possibly non-reacted chlorine, washing out hydrogen chloride, removal of unstable chlorine ~inked to the side-chain by means of boiling under pressure with alkali base, drying the crude product with solid drying a~ents prior to fractionating and possibly the use of an expensive ma-terial for the chlorination device which may be necessary for preventing corrosion.
Moreover, the complete absence of any emission problems recommends the process of the invention for its lack of stress 29 on the environment.
~ . . . . . . .
'. ' ' - ' ' . ~ ', ~ ' ' : ,. . .
.
. . ' ' ~ ~
` HOE 75/F 751 The monochlorotoluenes submitted to nuclear chlorination are partially utilized as solvents, partially as startiny or intermediary products, e.g. for the manufacture of plant protec-; tion agents.
E X A_M P L E
The chlorination is carried out in a scheme corresponding to the industrial chlorination plant as per the illustration with a cylinder-shaped reactor (5) about 8 m high and having a diameter of about 1.4 m, being charged with about 5 cbm of cylindrical hollow steel bodies (measuring about 35 mm length, 35 mm dia-meter and 1 mm thickness), toluene and chlorine gas being continuously fed into the reactor and the crude reaction product flowing continuously off the reactor through line (8) proportionally to the supply of the starting products. The reactor is supplied with 13.66 to/day of toluene (water content less than 0.03 weight %j 2862 Ncbm/day "chlorine gas and abt. 700 g/day" S2C12 The temperatureinside the reactor is about 30C. The quantity of chlorine supplied amounts to approximately 80 % of the stolchiometrically necessary quantity of chlorine. The ` residence time of the reaction mixture in the reactor reaches about 15 hours.
The liquid crude reaction product flowing off the reactor at the rate of 17.78 to/day consists of 2.73 to/day of non~
reacied toluene and of 15.0 to/day of crude chlorotoluene;
additionally are formed 2862 Ncbm/day of h~-drochloric acid.
The crude chlorotoluene freed from hydrogen chloride and ~9 non-reacted toluene has the following composition (in weight ~):
, . , ' : : ' :
. .
. . . . .
~ 7 ~ HOE 75/~ 751 :
o-chlorotoluene 49.0 weight %
m-chlorotoluene~ 0.2 weight %
p-chlorotoluene 48.0 weight %
benzyl chloride 0 weight %
dichlorotoluenes2.8 weight %
The analytical definition of the products was carried out by gas chromatography, the yield was determined by weighing.
The total yield of o-and p-chlorotoluene, calculated on reac~ed toluene, surpasses 97 % of the theoretical yield. The chlorine fed in undergoes a practically quantitative reaction.
.
,--.
~- ,, ' ' . . ' .
.
' . ~ ,
Claims (14)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for the continuous preparation of o- and p-chlorotoluene by nuclear chlorination of toluene with chlorine in the presence of a catalyst in which toluene and chlorine are reacted at a molar number ratio of chlorine to toluene of 0.4 to 1.0 at a temperature of from 5 to 70°C in the presence of at least one catalyst in a parallel current, the toluene, chlorine and catalyst are thoroughly mixed in a reaction zone, the re-action is completed, the chlorination mixture is freed from hydrogen chloride and from non-reacted toluene by distillation and the sump product resulting from the distillation is separated immediately to yield the isomeric o- and p-chlorotoluenes.
2. A process as claimed in claim 1 in which the molar number ratio of chlorine to toluene is 0.6 to 0.9.
3. A process as claimed in claim 1 in which the reaction is carried out at a temperature of from 15 to 40°C.
4. A process as claimed in claim 1, claim 2 or claim 3 in which the catalyst is utilized at a rate of from 5 to 100 ppm, calculated on the employed quantity of toluene.
5. A process as claimed in claim 1, claim 2 or claim 3 in which the catalyst is utilized at a rate of from 15 to 30 ppm, calculated on the employed quantity of toluene.
6. A process as claimed in claim 1, claim 2 or claim 3 in which the catalyst is ferrous chloride.
7. A process as claimed in claim 1, claim 2 or claim 3 in which the catalyst is a mixture of ferrous chloride and sulfurous chloride.
8. A process as claimed in claim 1, claim 2 or claim 3 in which ferrous chloride is formed in situ in the reaction zone of toluene and chlorine.
9. A process as claimed in claim 1, claim 2 or claim 3 in which the water content of toluene does not surpass a maximum of 0.03 weight %.
10. A process as claimed in claim 1, claim 2 or claim 3 in which the water content of toluene does not surpass a maximum of 0.001 to 0.025 weight %.
11. A process as claimed in claim 1, claim 2 or claim 3 in which the water content of toluene does not surpass a maximum from 0.01 to 0.02 weight %.
12. A process as claimed in claim 1, claim 2 or claim 3 in which gaseous hydrogen chloride which is formed during the re-action is used for drying toluene prior to reaction with the chlorine.
13. A process as claimed in claim 1, claim 2 or claim 3 in which any unreacted toluene is fed back into the reaction mixture.
14. A process as claimed in claim 1, claim 2 or claim 3 in which the reaction is carried out under atmospheric pressure.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE2536261A DE2536261C3 (en) | 1975-08-14 | 1975-08-14 | Process for the continuous production of o- and p-chlorotoluene |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1080752A true CA1080752A (en) | 1980-07-01 |
Family
ID=5953986
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA259,016A Expired CA1080752A (en) | 1975-08-14 | 1976-08-13 | Process for the continuous manufacture of o- and p-chlorotoluene |
Country Status (13)
| Country | Link |
|---|---|
| JP (1) | JPS601289B2 (en) |
| BE (1) | BE845239A (en) |
| BR (1) | BR7605246A (en) |
| CA (1) | CA1080752A (en) |
| CH (1) | CH619914A5 (en) |
| DD (1) | DD126297A5 (en) |
| DE (1) | DE2536261C3 (en) |
| FR (1) | FR2320926A1 (en) |
| GB (1) | GB1497015A (en) |
| IE (1) | IE43288B1 (en) |
| IL (1) | IL50249A (en) |
| IT (1) | IT1064920B (en) |
| NL (1) | NL7608831A (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4138243A1 (en) * | 1991-11-21 | 1993-05-27 | Bayer Ag | IMPROVED METHOD FOR THE NUCLEAR HORIZATION OF AROMATIC HYDROCARBONS |
| JP2002154995A (en) * | 2000-11-21 | 2002-05-28 | Toray Ind Inc | Method for producing chlorinated aromatic compounds |
| CN103724159B (en) * | 2014-02-02 | 2016-02-03 | 安徽八一化工股份有限公司 | Acid chlorization liquid deacidifying process in benzene chloride production |
| CN105174217A (en) * | 2014-06-20 | 2015-12-23 | 唐慧建 | Method for purifying chlorotoluene byproduct hydrogen chloride gas and regenerating absorbent |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3226447A (en) * | 1960-12-22 | 1965-12-28 | Union Carbide Australia | Directed nuclear substitution-chlorination of aromatic hydrocarbons and halogenated aromatic hydrocarbons |
| FR1446139A (en) * | 1964-09-02 | 1966-07-15 | Hooker Chemical Corp | Chlorination of toluene |
| FR1491144A (en) * | 1965-09-03 | 1967-08-04 | Tenneco Chem | Process for the production of chlorotoluenes containing a relatively high proportion of para-chlorotoluene |
-
1975
- 1975-08-14 DE DE2536261A patent/DE2536261C3/en not_active Expired
-
1976
- 1976-08-06 DD DD194235A patent/DD126297A5/xx unknown
- 1976-08-09 NL NL7608831A patent/NL7608831A/en not_active Application Discontinuation
- 1976-08-11 BR BR7605246A patent/BR7605246A/en unknown
- 1976-08-11 CH CH1021676A patent/CH619914A5/en not_active IP Right Cessation
- 1976-08-11 GB GB33372/76A patent/GB1497015A/en not_active Expired
- 1976-08-12 IL IL50249A patent/IL50249A/en unknown
- 1976-08-12 IT IT26261/76A patent/IT1064920B/en active
- 1976-08-13 CA CA259,016A patent/CA1080752A/en not_active Expired
- 1976-08-13 JP JP51096187A patent/JPS601289B2/en not_active Expired
- 1976-08-13 IE IE1801/76A patent/IE43288B1/en unknown
- 1976-08-16 FR FR7624862A patent/FR2320926A1/en active Granted
- 1976-08-16 BE BE169853A patent/BE845239A/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| DE2536261C3 (en) | 1979-06-21 |
| CH619914A5 (en) | 1980-10-31 |
| FR2320926A1 (en) | 1977-03-11 |
| IL50249A0 (en) | 1976-10-31 |
| NL7608831A (en) | 1977-02-16 |
| BE845239A (en) | 1977-02-16 |
| DE2536261B2 (en) | 1977-09-22 |
| FR2320926B1 (en) | 1982-07-02 |
| JPS5253822A (en) | 1977-04-30 |
| IE43288B1 (en) | 1981-01-28 |
| IL50249A (en) | 1980-10-26 |
| IE43288L (en) | 1977-02-14 |
| DD126297A5 (en) | 1977-07-06 |
| JPS601289B2 (en) | 1985-01-14 |
| BR7605246A (en) | 1977-08-09 |
| GB1497015A (en) | 1978-01-05 |
| DE2536261A1 (en) | 1977-02-24 |
| IT1064920B (en) | 1985-02-25 |
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