CA2024796C - Process for producing chlorosulfonyl isocyanate - Google Patents
Process for producing chlorosulfonyl isocyanate Download PDFInfo
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- CA2024796C CA2024796C CA 2024796 CA2024796A CA2024796C CA 2024796 C CA2024796 C CA 2024796C CA 2024796 CA2024796 CA 2024796 CA 2024796 A CA2024796 A CA 2024796A CA 2024796 C CA2024796 C CA 2024796C
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- sulfur trioxide
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- chlorosulfonyl isocyanate
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Abstract
Provided is a process for producing chlorosulfonyl isocyanate by reacting sulfur trioxide with cyanogen chloride, which comprises feeding sulfur trioxide and cyanogen chloride simultaneously to the reaction zone and maintaining the temperature of the reacting zone at 10 to 50°C. This is a commercially very simple process and can produce chlorosulfonyl isocyanate with high purity in high yield.
Description
~'~~~~~~a PROCESS FOR PRODUCING~CHLOROSULFONYL ISOCYANATE
BACKGROUND OF TTiE INVENTION
1. Field of the Invention The present invention relates to a process for producing chlorosulfonyl isocyanate. More specifically, the present invention relates to a process for producing chlorosulfonyl isocyanate with high purity in a high yield.
BACKGROUND OF TTiE INVENTION
1. Field of the Invention The present invention relates to a process for producing chlorosulfonyl isocyanate. More specifically, the present invention relates to a process for producing chlorosulfonyl isocyanate with high purity in a high yield.
2. Description of the Prior Art Ctalorosulfonyl: isocyanate, also called N-carbonylsul-famoyl chloride, has a chemical formula of 0= C= NSOZ C1 and is a useful compound attracting, particularly in recent years, much attention as intermediate raw materials for the production of medicines, agricultural chemicals, sweetners and the like and improving agents for synthetic fibers, synthetic resins and like materials.
It has been known for long that chlorosulfonyl isocyanate is obtained by reacting sulfur trioxide with cyanogen chloride. See far example Org. Synth. Coll. ~, 226-231; Angew. Chem. Internet. Edit. 7,' No. 3, 172-173 (1968);
Chem. ger. 89, 1071-1079, (1956), German Pat. 928,896 (1955) and British Pat. 77A,276 (1957). .
The former two of the above literature disclose a pro-cess for producing chlorosulfonyl isocyanate which comprises adding sulfur trioxide to liquid cyanogen chloride at a low temperature of -5°C or below. This process, however, has problems in that it must use as large an amount of liquid ~~~w'~~~
cyanogen chloride as 1.5-3, times that of sulfur trioxide, thereby being not suited for commercial production both economically and from the viewpoint of safety, that the yield is as low as about 60 to 62~, and that the obtained S product is not of satisfactory qualities to meet the demands of market.
The latter three disclose a process which comprises mixing sulfur trioxide with cyanogen chloride at a tempera-tuts above 100'C, e.g. 100-200°C. This process also has problems of d'i'fficulty in providing the ..product with satisfactory qualities, since the flow rates of sulfur trioxide and eyanogen chloride are difficult to control and there form large amounts of byproducts depending on the reaction conditions employed.
On the other hand, U.S.P. 3,375,088 discloses a process for obtaining a high-purity chlorosul.fonyl isocyanate, which.
comprises treating the crude chl,orosulfonyl isocyanate obtained by reacting sulfur trioxide with cyanogen chloride with benzonitrile or its derivatives. However, in employing this process it is necessar to se aratel y p y provide the process of reacting sulfur trioxide with cyanogen chloride and that of purifying the crude chlorosulfonyl isocyanate, and to further provide a process for recovering arid purify-I
ing the treating agent including benzonitrile. Accordingly, i the whole process is complexed, thereby requiring high equipment cost and time-consuming operation, and hence this process has not been fully satisfactory for commercial _, production.
In view of the foregoing, we have proposed, for the purpose of solving the problems encountered in the above processes, a pracess for producing chlorosulfonyl isocyanate which comprises adding cyanogen chloride to liquid sulfur trioxide and reacting them while maintaining the tempera-tore of the reaction system at 20 to 50°C (Japanese Patent Application Laid-open No. 77855/1988). This process has made it possible to commercially produce in a simple manner chlorosulfanyl ~isocyanate with a relatively high purity in a relatively high yield, and to salve to some extent the pro-blems of conventional processes, i.e. low yield and purity resulting from formation of byproducts. However, with ever enhancing demands from the market, there has been desired development of a process which can provide chlorasulfonyl isocyanate with a still higher pux:ity in a still higher yield.
SUMMARY OF THE INVENTION
Accordin 1 an ob ect of the g y, j present invention is to provide a novel process for producing chlorosulfonyl isocyanate which can solve the shove problems.
Another object of the present invention is to provide a process for producing high-purity chlorosulfonyl isocyanate economically and in high yield by reacting sulfur trioxide with cyanogen chloride.
These objects can be achieved by a process for produc-ing chlorosulfonyl isocyanate by reacting sulfur trioxide with cyanogen chloride, which comprises feeding sulfur trioxide and cyanogen chloride at the same time to the reaction zone and maintaining the temperature of the reacting zone at 10 to 50°C:
DESCRIPTION OF PREFERRED EMEODIMENTS
Any liquid sulfur trioxide can be used in the present invention, but particularly preferred is the r type in view of its high reactivity." The sulfur trioxide_.may incorporate a stabilizer to prevent polymerization in a small amount, e.g. 0.0001 to 5~ by weight, preferably 0.001 to 1$ by weight. Examples of the stabilizer generally used are organosilicnn compounds, carbon tetrachloride, dimethyl sulfate, boron compounds, phosphorus compounds, aromatic hydrocarbons and aromatic sulfonic acids.
The cyanogen chloride used in the process of the present invention may either be in the gaseous form or liquid, of which the gaseous form is preferred. Cyanogen chloride is commercially produced from hydrocyanic acid and chlorine and generally has a purity of 96 to 99$ by weight, one with a purity of at least 95$ being also usable.
The most particular feature of the present invention lies in the simultaneous feeding of sulfur trioxide and cyanogen chloride to the reaction zone. The simultaneous feeding may be conducted either continuously or inter-mittently, but generally employed is a continuous feeding.
_4_ 9~ ;r,. ~..~ .a .r s t~
More concretely, for example, a reaction vessel is equipped with a stirrer and/or a circulation circuit, and gaseous or liquid cyanogen chloride and liquid sulfur trioxide: are simultaneously fed through separate feed ports into the reaction vessel and/or circulation circuit. Here, gaseous cyanogen chloride may for example be fed through a gas inlet tube so fitted that its end reaches near the bottom of the reaction vessel, or into the circulation circuit while sulfur trioxide or a reaction solution containing chloro-sulfonyl isocyanate~ i:s being circulated therein. Liquid cyanogen chloride may for example be fed through a inlet tube similar to the above, or be added dropwise from the tog of the reaction vessel. Liquid sulfur trioxide is prefer-ably added dropwise from the tog, of the reaction vessel.
In the present invention, the temperature of the reaction zone to which cyanogen chloride and sulfur trioxide are simultaneously added is maintained at 10 to 50°C, preferably at 15 to 35°C and it i.s necessary that the reaction be effected at this temperature range. If the temperature of the reaction zone is below 10°C or higher than 50°C, there will form large'amounts of byproducts such as chloropyrosulfonyl isocyanate and 2,6-dichloro-1,4,3,5-oxathiadiazine-4,4-dioxide, thereby lowering both the yield and purity of the obtained chlorosulfonyl isocyanate, which is not preferred.
In the reaction of the present invention, it is preferred that cyanogen chloride be fed per unit tame in a c~ 3 :~ ~ ,_l :1 ~~
!d ~t t~~ ~_~c 3 .J ~~
mole ratio based on the mole of sulfur trioxide of 0.6 to 1.1, more preferably 0.8 to 1.0 and most preferably 0.9 to 1Ø rf the feed mole ratio based on the mole of sulfur trioxide per unit time is less than 0.6 or more than 1.1, byproducts will tend to form in larger amounts, whereby both the yield and purity of the product decreases.
Tha feed rates of cyanogen chloride and sulfur trioxide are appropriately adjusted in such ranges that can keep the temperature of the reaction zone within the range of from 10 to 50°C, preferably from.15 to 35°C.
In the reaction of the present invention, while the feed of cyanogen chloride and sulfur trioxide are generally started simultaneously, the feed of sulfur trioxide may first be started with that of cyanc>gen chloride started a little later. I3owever, the feed of c;yanogen chloride should not first be started, because, then, formation of byproducts sometimes becomes more marked to thereby lower the yield and purity.
Tn the present invention, the reaction zone can previ-ously be charged with sulfur trioxide or a liquid containing chlorosulfonyl isocyanate, before the start of feeding cyanogen chloride and sulfur trioxide. Tn this case prefer-ably employed for the purpose of achieving higher yield is a method of starting the feeding~.of cyanogen chloride and sulfur trioxide while the above precharged liquid is being stirred or circulated. For,instance, a preferred embodiment of this method comprises, while circulating the precharged ~ --- g -f ~ ~3 liquid in a circulation circuit mounted on the reaction vessel, continuously feeding cyanogen chloride into the circulation circuit and, at the same time, continuously feeding sulfur trioxide into the reaction vessel.
The liquid containing chlorosulfonyl isocyanate refer-red to in the present invention means any liquid containing and dissolving chlorosulfonyl isocyanate in an amount of, preferably, at least d0$ by weight, more preferably at least 60~ by weight. This liquid may further contain at least one member selected' from the group consisting o.f sulfur tri-oxide, chloropyrosulfonyl isocyanate, pyrosulfuryl chloride, sulfonyl diisocyanate, sulfur dioxide and chlorine.
The overall amount of the cyanogen chloride used in the reaction of the present invention is generally in a mole ratio based on the total moles of sulfur trioxide used of 0.8 to 1.3, preferably 0.9 to 1.1.
Also in the case where the feeding of sulfur trioxide is startad prior to that of cyanogen chloride or where a liquid containing chlorosulfonyl isocyanate is charged beforehand, it is preferred that, for the time period during which, cyanogen chloride and sulfur trioxide are simultane-ously fed, cyanogen chloride be fed per unit time in a mole ratio based on the mole of sulfur trioxide of 0.6 to 1.1, more preferably 0.8 to 1.0 and most preferably 0.9 to 1Ø
Where the feeding of sulfur trioxide is ended prior to that of cyanogen chloride, cyanogen chloride alone can further be fed in such an amount that the total amount of cyanogen will _7_ be in a mole ratio based on the total moles of sulfur trioxide used of 0.8 to 1.3, preferably 0.9 to 1.1.
The chlorosulfonyl isocyanate prepared by the above process is purified by distillation. The distillation can be conducted through a conventional distillation column, while the reaction mixture in the reaction zone is being continuously withdrawn ar after the total amount thereof has been withdrawn batch-wise, under atmospheric pressure or reduced pressure.
The bottoms' remaining after the above distillation can then be heated under atmospheric pressure at 130°C or above to decompose, and the resulting decomposition mixture can, in the same manner as the afore-described suflur trioxide or the liquid containing chlorosulfonyl isocyanate, be charged in the reaction zone beforehand, to which, with stirring or during circulation, cyanogen chloride and sulfur trioxide are fed at the same time to effect r~:ac~tion.
Other features of the invention will become apparent in the course of the following descriptions of the exemplary embodiments which are given for illustration of the invention and are not intending to be limiting thereof.
EXAMPLES
Example 1 A d-necked flask having a capacity of 200 ml was fitted with a stirrer, a thermometer, a reflux condenser and a gas inlet which was a glass tuba having an inside diameter of 6 _g_ mm and a length that nearly reached the bottom of the flask.
The 4-necked flask thus prepared was charged with 8 g of a liquid sulfur trioxide of r type (NISSO SULFAN, made by Nippon Soda Co., Ltd.) and, then, the feeding of cyanogen chloride gas and sulfur trioxide was started at the same time with stirring. The cyanogen chloride gas (correspond-ing to 61.5 g) was fed over 5 hours and the liquid sulfur trioxide (corresponding to 73.1 g) was fed over 4 hours.
While they were being fed, the temperature of the reaction zone was kept at' 25 ~to 35°C by using an external bath.
After the feeding of cyanogen chloride had been completed, the reaction zone was stirred for 1 hour at a temperature of 25 to 30°C. After completion of the reaction, the reflux condenser and the gas inlet were taken off from the 4-necked flask, and then a distillation column packed with glass helices and having an inside diameter and a height of 1.5 cm and 17 cm respectively was mounted on the flask. The reac-tion mixture was distilled with the apparatus thus prepared under atmospheric pressure to give 127 g of chlorosulfonyl isocyanate (purity: 97~) as a fraction at a boiling point of 106 to 107°C/760 mmIig. The yield based on the amount of cyanogen chloride used was 87~.
Example 2 A 4-necked flask was charged with 18.6 g of chloro-sulfonyl isocyanate and 1.4 g of a liquid sulfur trioxide of r type. Then, using 61.5 g of cyanogen chloride gas and 80.1 g of the liquid sulfur trioxide, reaction was effected _g_ in the same manner as in.Example 1, to obtain 143 g of chlorosulfonyl isocyanate (purity: 99~) as a fraction at a boiling point of 55 to 56°C/100 mmFIg. The yield based on the amount of cyanogen chloride used was 87~.
Example 3 A 4-necked flask was charged with 20 g of a decomposi-tion mixture obtained by distillation by heating at 130°C or above of the bottoms having remained after distilling off of the chlorosulfonyl isocyanate which had been the product of reaction of sulfur~.trioxide with cyanogen chloride. Then, reaction was effected in the same manner as in Example 1 using 61.5 g of cyanogen chloride gas and 80.1 g of a liquid sulfur trioxide of r type, to obtain 123 g of chlorosulfonyl isocyanate (purity 95$).
Examgle 4 A 4-necked flask having a capaca.ty of 200 ml was fitted with a circulation circuit connecting the bottom to the neck of the flask, a stirrer, a thermometer, a dropping funnel and a reflex condenser. The circulation circuit, having an intra-circuit cagacity of 40 ml, was fitted with a circula-Lion pump and a cyanogen chloride gas inlet.
The 4-necked flask thus prepared was charged with 62.4 g of chlorosulfonyl isocyanate and 120.1 g of sulfur trioxide and, then, the feeding of cyanogen chloride gas (corresponding to 97.0 g) and 120.1 g of an liquid sulfur trioxide of r type was started at the same time, with stirring and circulating. The cyanogen chloride gas was fed over 5.5 hours, while the liquid sulfur trioxide was added dropwise over 5 hours. During the feeding, the temperature of the reaction gone was kept at 20 to 25°C by using an external bath. After the reaction had been completed, the reaction mixture was distilled under atmospheric pressure through a distillation column packed with glass helices and having an inside diameter. and a height of 1.5 cm and 17 cm respectively, to give 267 g of chlorosulfonyl isocyanate (purity: 96~) as a fraction at a boiling point of 106 to 107°C/760 mmFig... T.~e _yield based on the amount of cyanogen chloride used was 88~.
Example 5 A reaction vessel with a jacket and having a capacity of 100 ~ was mounted with a circulatian circuit having an infra-circuit capacity of 18 ~, a stirrer, a thermometer, a sulfur .trioxide feed port. The circulation circuit was fitted with a heat exchanger for cooling, a circulation pump and a cyanogen chloride gas inlet.
The reaction vessel thus prepared was charged first w~-th 33.3 kg of a crude chlorosulfonyl isocyanate solution ,.
containing 57~ by weight of chlorosulfonyl isocyanate, 19~ , by weight of sulfur trioxide and 221f by weight of chloro-pyrosulfonyl isocyanate, and then the feeding of a liquid sulfur trioxide of r type and cyanogen chloride gas was started at the same time under circulation of the solution.
The liquid sulfur trioxide was fed in an amount of 69 kg at a rate of 11.3 kg/hr and the cyanogen chloride gas in an ~~~~'v' - amount of SS kg at a rate of 8.9 kg/hr. During the feeding of the sulfur trioxide and the cyanogen chloride, the temperature of the reaction zone was kept at 15 to 22°C by using an external heat exchanger and the jacket.
After the reaction had been completed, the reaction mixture was distilled under reduced pressure through a distillation column packed with porcelain ~taschig rings and having an inside diameter and a height of 20 cm and 2 m, respecti~rely, to give 137 kg of chlorosulfonyl isocyanate (purity: 98~) as "~ fraction at a boiling poi~xt of 56°C/100 mmHg. The yield based on the amount of cyanogen chloride used was 91~.
Example 6 The same reaction vessel as used in Example 5 was charg-ed with 30.0 kg of a liquid sulfur trioxide of r type and, then, the feed of a cyanogen chloride gas (corresponding to 65.6 kg) and the liquid sulfur trioX:ide in an amount of 70.0 kg was started at the same time under circulation. The cyanogen chloride gas was fed over 7.5 hours, while the sulfur trioxide over 4.8 hours. During the feed the tempera-ture of the reaction zone was kept at 15 to 25°C by cooling.
After the reaction has been completed, the reaction mixture was distilled in the same manner as in Example 5, to obtain 135 kg of chlorosulfonyl isocyanate (purity: 95$) as a fraction at a boiling point of 55 to 56°C/100 mmHg. The yield based on the amount of cyanogen chloride used was 84$.
Comparative Example 1 °12-A 4-necked flask having a capacity of 200 ml was fitted with a stirrer, a thermometer, a reflux condenser and a drop-ping funnel. The 4-necked flask thus prepared was charged with 61 .5 g of a liquid cyanogen chloride and the contents was cooled to 0°C. To the contents 80.1 g of sulfur trioxide was added from the dropping funnel over about 1.5 hours. During the addition, the temperature of the reaction zone was kept at 0°C or below by using an external bath.
After the addition, the reaction zone was stirred for 2 hour at a temperaturewof~25~ to 30°C. After completion of the reaction, the reaction mixture was distilled with the same distillation column as used in Example 1 under atmospheric pressure to give 28.3 g of chlorasulfonyl isocyanate (purity: 72~) as a fraction at a boiling point of 10a to 108'C/760 mmFig. The yield based on the amount of cyanogen chloride used was 15~, Comyoarative Example 2 To 61.5 g of the liquid cyanogen chloride was added 80.1 g of the sulfur trioxide in the same manner as in Com parative Example 1. After the addition has been completed, the reaction zone was stirred for 2 hours at a temperature of 25 to 30°C. Then, the dropping funnel and the reflux condenser were taken off from the flask and the flask was fitted with a gas inlet of a glass tube having an inside diameter of 6 mm and such a length as to nearly reach the bottom of the flask and the same distillation column as used in Example 1.
:~ is r ~i~~~~ ~~ ~~
While the reaction mixture was being heated at a temperature of 100 to 130'C, about 60 g of cyanogen chloride was streamed into the reaction zone at a rate of about 0.01 mole/min to obtain crude chlorosulfonyl isocyanate as a dis--fillets withdrawn from the top of the distillation column.
When the amount of the bottoms in the flask reached about 5 ml, the introduction of eyanogen chloride gas was stopped and the distillation terminated. The crude product obtained was distilled under reduced pressure through the same distillation columil used in hxampie 2, to give 77.9 g of chlorosulfonyl isocyanate {purity: 87~) as a fraction at a boiling point of 52 to 56°C/100 mmHg. The yield based on the amount of cyanogen chloride used was 48~.
Comparative Example 3 A 4-necked flask having a capacity of 200 ml was fitted with a stirrer, a thermometer, a reflux condenser and a gas inlet of a glass tube having an inside diameter of 6 mm and a length nearly reaching the bottom of the flask. The 4-necked flask thus prepared was charged with 79.5 g of a liq-uid sulfur trioxide of r type and, then, cyanogen chloride gas (corresponding to 62.9 g) was introduced oust 2 hours with stirring. During the addition, the temperature of the 1 0 reaction zone was-kept ~ at 25 to 35°C by using an external bath. After the addition has been completed, the reaction zone was stirred for 0.5 hour at a temperature of 25 to 30°C. After completion of the reaction, the reflux condens-er and the gas inlet tube were removed from the 4-necked flask, and a distillation column packed with glass helices and having an inside diameter and a height of 1.5 cm and 10 cm respectively was fitted to they flask. The reaction mixture was distilled under atmospheric pressure to give 119.1 g of chlorosulfonyl isocyanate (purity: 90$) as a fraction at a boiling point of 106 to 107°C/760 mmHg. The yield based on the amount of cyanogen chloride used was 76$.
Com~arativca Example 4 The same apparatus as used in Comparative Example 3 was used. The flask was charged with 79.5 g of a liquid sulfur trioxide of r type and, then, 68.0 g of cyanogen chloride gas was introduced over 7 hour with stirring. During the addition the temperature of the reaction zone was controlled to be within a range of 20 to 48°C by using an external bath. After the addition the reaction zone was stirred for 1 hour at 30°C. Then, the reaction mixture was distilled under a reduced pressure of 100 mmHg through the same distil-lation column as in Comparative Example 3, to give 104.2 g of chlorosulfonyl isocyanate (purity: 95~~) as a fraction at a boiling point of 55 to 56°C/100 mmHg. The yield based on the amount of cyanogen chloride used was 70$.
Comparative Example 5 The same appax'atus as used in Comparative.Example 3 was used. The flask was charged with 117.6 g of a liquid sulfur trioxide of r type and, then, 89.7 g of cyanogen chloride 5~as was introduced over 6 hour with stirring. During the ad-dition the temperature of the reaction zone was adjusted to be 25 to 30°C by using an external bath. After the addition the reaction zone was stirred for 0.5 hour at 25 to 30°C.
Then, the reaction mixture was distilled under atmospheric pressure through the same distillai=ion column as used in 'Comparative Examgle 3, to give 91.2 g of chlorosulfonyl isocyanate (purity: 85$) as a fraction at a boiling point of 106 to 108°C/760 mmHg. The yield based on the amount of cyanogen chloride used was 38$.
Com ap rative Example 6 The same apparatus as in Comparative Example 3 was us-ed. The flask was charged with 79.5 g of a liquid sulfur trioxide of r type and, then, 89.7 g of cyanogen chloride gas was introduced over 10 seconds with stirring. During " the addition, the temperature of the reaction zone was adjusted to be within a range of 20 to 48°C by using an external bath. After the addition, the reaction zone was stirred for 1 hour at 25 to 30°C. Then, the reaction S mixture was distilled under atmospheric pressure through the same distillation column as used in Comparative Example 3, to give 68.8 g of chlorosulfonyl isocyanate (purity: 96~) as a fraction at a boiling point of 106 to 107°C/760 mmHg. The yield based on the amount of cyanogen chloride used was 47~.
. . .., . . ...- .
Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced 1S otherwise than as specifically descr:i.bed herein.
It has been known for long that chlorosulfonyl isocyanate is obtained by reacting sulfur trioxide with cyanogen chloride. See far example Org. Synth. Coll. ~, 226-231; Angew. Chem. Internet. Edit. 7,' No. 3, 172-173 (1968);
Chem. ger. 89, 1071-1079, (1956), German Pat. 928,896 (1955) and British Pat. 77A,276 (1957). .
The former two of the above literature disclose a pro-cess for producing chlorosulfonyl isocyanate which comprises adding sulfur trioxide to liquid cyanogen chloride at a low temperature of -5°C or below. This process, however, has problems in that it must use as large an amount of liquid ~~~w'~~~
cyanogen chloride as 1.5-3, times that of sulfur trioxide, thereby being not suited for commercial production both economically and from the viewpoint of safety, that the yield is as low as about 60 to 62~, and that the obtained S product is not of satisfactory qualities to meet the demands of market.
The latter three disclose a process which comprises mixing sulfur trioxide with cyanogen chloride at a tempera-tuts above 100'C, e.g. 100-200°C. This process also has problems of d'i'fficulty in providing the ..product with satisfactory qualities, since the flow rates of sulfur trioxide and eyanogen chloride are difficult to control and there form large amounts of byproducts depending on the reaction conditions employed.
On the other hand, U.S.P. 3,375,088 discloses a process for obtaining a high-purity chlorosul.fonyl isocyanate, which.
comprises treating the crude chl,orosulfonyl isocyanate obtained by reacting sulfur trioxide with cyanogen chloride with benzonitrile or its derivatives. However, in employing this process it is necessar to se aratel y p y provide the process of reacting sulfur trioxide with cyanogen chloride and that of purifying the crude chlorosulfonyl isocyanate, and to further provide a process for recovering arid purify-I
ing the treating agent including benzonitrile. Accordingly, i the whole process is complexed, thereby requiring high equipment cost and time-consuming operation, and hence this process has not been fully satisfactory for commercial _, production.
In view of the foregoing, we have proposed, for the purpose of solving the problems encountered in the above processes, a pracess for producing chlorosulfonyl isocyanate which comprises adding cyanogen chloride to liquid sulfur trioxide and reacting them while maintaining the tempera-tore of the reaction system at 20 to 50°C (Japanese Patent Application Laid-open No. 77855/1988). This process has made it possible to commercially produce in a simple manner chlorosulfanyl ~isocyanate with a relatively high purity in a relatively high yield, and to salve to some extent the pro-blems of conventional processes, i.e. low yield and purity resulting from formation of byproducts. However, with ever enhancing demands from the market, there has been desired development of a process which can provide chlorasulfonyl isocyanate with a still higher pux:ity in a still higher yield.
SUMMARY OF THE INVENTION
Accordin 1 an ob ect of the g y, j present invention is to provide a novel process for producing chlorosulfonyl isocyanate which can solve the shove problems.
Another object of the present invention is to provide a process for producing high-purity chlorosulfonyl isocyanate economically and in high yield by reacting sulfur trioxide with cyanogen chloride.
These objects can be achieved by a process for produc-ing chlorosulfonyl isocyanate by reacting sulfur trioxide with cyanogen chloride, which comprises feeding sulfur trioxide and cyanogen chloride at the same time to the reaction zone and maintaining the temperature of the reacting zone at 10 to 50°C:
DESCRIPTION OF PREFERRED EMEODIMENTS
Any liquid sulfur trioxide can be used in the present invention, but particularly preferred is the r type in view of its high reactivity." The sulfur trioxide_.may incorporate a stabilizer to prevent polymerization in a small amount, e.g. 0.0001 to 5~ by weight, preferably 0.001 to 1$ by weight. Examples of the stabilizer generally used are organosilicnn compounds, carbon tetrachloride, dimethyl sulfate, boron compounds, phosphorus compounds, aromatic hydrocarbons and aromatic sulfonic acids.
The cyanogen chloride used in the process of the present invention may either be in the gaseous form or liquid, of which the gaseous form is preferred. Cyanogen chloride is commercially produced from hydrocyanic acid and chlorine and generally has a purity of 96 to 99$ by weight, one with a purity of at least 95$ being also usable.
The most particular feature of the present invention lies in the simultaneous feeding of sulfur trioxide and cyanogen chloride to the reaction zone. The simultaneous feeding may be conducted either continuously or inter-mittently, but generally employed is a continuous feeding.
_4_ 9~ ;r,. ~..~ .a .r s t~
More concretely, for example, a reaction vessel is equipped with a stirrer and/or a circulation circuit, and gaseous or liquid cyanogen chloride and liquid sulfur trioxide: are simultaneously fed through separate feed ports into the reaction vessel and/or circulation circuit. Here, gaseous cyanogen chloride may for example be fed through a gas inlet tube so fitted that its end reaches near the bottom of the reaction vessel, or into the circulation circuit while sulfur trioxide or a reaction solution containing chloro-sulfonyl isocyanate~ i:s being circulated therein. Liquid cyanogen chloride may for example be fed through a inlet tube similar to the above, or be added dropwise from the tog of the reaction vessel. Liquid sulfur trioxide is prefer-ably added dropwise from the tog, of the reaction vessel.
In the present invention, the temperature of the reaction zone to which cyanogen chloride and sulfur trioxide are simultaneously added is maintained at 10 to 50°C, preferably at 15 to 35°C and it i.s necessary that the reaction be effected at this temperature range. If the temperature of the reaction zone is below 10°C or higher than 50°C, there will form large'amounts of byproducts such as chloropyrosulfonyl isocyanate and 2,6-dichloro-1,4,3,5-oxathiadiazine-4,4-dioxide, thereby lowering both the yield and purity of the obtained chlorosulfonyl isocyanate, which is not preferred.
In the reaction of the present invention, it is preferred that cyanogen chloride be fed per unit tame in a c~ 3 :~ ~ ,_l :1 ~~
!d ~t t~~ ~_~c 3 .J ~~
mole ratio based on the mole of sulfur trioxide of 0.6 to 1.1, more preferably 0.8 to 1.0 and most preferably 0.9 to 1Ø rf the feed mole ratio based on the mole of sulfur trioxide per unit time is less than 0.6 or more than 1.1, byproducts will tend to form in larger amounts, whereby both the yield and purity of the product decreases.
Tha feed rates of cyanogen chloride and sulfur trioxide are appropriately adjusted in such ranges that can keep the temperature of the reaction zone within the range of from 10 to 50°C, preferably from.15 to 35°C.
In the reaction of the present invention, while the feed of cyanogen chloride and sulfur trioxide are generally started simultaneously, the feed of sulfur trioxide may first be started with that of cyanc>gen chloride started a little later. I3owever, the feed of c;yanogen chloride should not first be started, because, then, formation of byproducts sometimes becomes more marked to thereby lower the yield and purity.
Tn the present invention, the reaction zone can previ-ously be charged with sulfur trioxide or a liquid containing chlorosulfonyl isocyanate, before the start of feeding cyanogen chloride and sulfur trioxide. Tn this case prefer-ably employed for the purpose of achieving higher yield is a method of starting the feeding~.of cyanogen chloride and sulfur trioxide while the above precharged liquid is being stirred or circulated. For,instance, a preferred embodiment of this method comprises, while circulating the precharged ~ --- g -f ~ ~3 liquid in a circulation circuit mounted on the reaction vessel, continuously feeding cyanogen chloride into the circulation circuit and, at the same time, continuously feeding sulfur trioxide into the reaction vessel.
The liquid containing chlorosulfonyl isocyanate refer-red to in the present invention means any liquid containing and dissolving chlorosulfonyl isocyanate in an amount of, preferably, at least d0$ by weight, more preferably at least 60~ by weight. This liquid may further contain at least one member selected' from the group consisting o.f sulfur tri-oxide, chloropyrosulfonyl isocyanate, pyrosulfuryl chloride, sulfonyl diisocyanate, sulfur dioxide and chlorine.
The overall amount of the cyanogen chloride used in the reaction of the present invention is generally in a mole ratio based on the total moles of sulfur trioxide used of 0.8 to 1.3, preferably 0.9 to 1.1.
Also in the case where the feeding of sulfur trioxide is startad prior to that of cyanogen chloride or where a liquid containing chlorosulfonyl isocyanate is charged beforehand, it is preferred that, for the time period during which, cyanogen chloride and sulfur trioxide are simultane-ously fed, cyanogen chloride be fed per unit time in a mole ratio based on the mole of sulfur trioxide of 0.6 to 1.1, more preferably 0.8 to 1.0 and most preferably 0.9 to 1Ø
Where the feeding of sulfur trioxide is ended prior to that of cyanogen chloride, cyanogen chloride alone can further be fed in such an amount that the total amount of cyanogen will _7_ be in a mole ratio based on the total moles of sulfur trioxide used of 0.8 to 1.3, preferably 0.9 to 1.1.
The chlorosulfonyl isocyanate prepared by the above process is purified by distillation. The distillation can be conducted through a conventional distillation column, while the reaction mixture in the reaction zone is being continuously withdrawn ar after the total amount thereof has been withdrawn batch-wise, under atmospheric pressure or reduced pressure.
The bottoms' remaining after the above distillation can then be heated under atmospheric pressure at 130°C or above to decompose, and the resulting decomposition mixture can, in the same manner as the afore-described suflur trioxide or the liquid containing chlorosulfonyl isocyanate, be charged in the reaction zone beforehand, to which, with stirring or during circulation, cyanogen chloride and sulfur trioxide are fed at the same time to effect r~:ac~tion.
Other features of the invention will become apparent in the course of the following descriptions of the exemplary embodiments which are given for illustration of the invention and are not intending to be limiting thereof.
EXAMPLES
Example 1 A d-necked flask having a capacity of 200 ml was fitted with a stirrer, a thermometer, a reflux condenser and a gas inlet which was a glass tuba having an inside diameter of 6 _g_ mm and a length that nearly reached the bottom of the flask.
The 4-necked flask thus prepared was charged with 8 g of a liquid sulfur trioxide of r type (NISSO SULFAN, made by Nippon Soda Co., Ltd.) and, then, the feeding of cyanogen chloride gas and sulfur trioxide was started at the same time with stirring. The cyanogen chloride gas (correspond-ing to 61.5 g) was fed over 5 hours and the liquid sulfur trioxide (corresponding to 73.1 g) was fed over 4 hours.
While they were being fed, the temperature of the reaction zone was kept at' 25 ~to 35°C by using an external bath.
After the feeding of cyanogen chloride had been completed, the reaction zone was stirred for 1 hour at a temperature of 25 to 30°C. After completion of the reaction, the reflux condenser and the gas inlet were taken off from the 4-necked flask, and then a distillation column packed with glass helices and having an inside diameter and a height of 1.5 cm and 17 cm respectively was mounted on the flask. The reac-tion mixture was distilled with the apparatus thus prepared under atmospheric pressure to give 127 g of chlorosulfonyl isocyanate (purity: 97~) as a fraction at a boiling point of 106 to 107°C/760 mmIig. The yield based on the amount of cyanogen chloride used was 87~.
Example 2 A 4-necked flask was charged with 18.6 g of chloro-sulfonyl isocyanate and 1.4 g of a liquid sulfur trioxide of r type. Then, using 61.5 g of cyanogen chloride gas and 80.1 g of the liquid sulfur trioxide, reaction was effected _g_ in the same manner as in.Example 1, to obtain 143 g of chlorosulfonyl isocyanate (purity: 99~) as a fraction at a boiling point of 55 to 56°C/100 mmFIg. The yield based on the amount of cyanogen chloride used was 87~.
Example 3 A 4-necked flask was charged with 20 g of a decomposi-tion mixture obtained by distillation by heating at 130°C or above of the bottoms having remained after distilling off of the chlorosulfonyl isocyanate which had been the product of reaction of sulfur~.trioxide with cyanogen chloride. Then, reaction was effected in the same manner as in Example 1 using 61.5 g of cyanogen chloride gas and 80.1 g of a liquid sulfur trioxide of r type, to obtain 123 g of chlorosulfonyl isocyanate (purity 95$).
Examgle 4 A 4-necked flask having a capaca.ty of 200 ml was fitted with a circulation circuit connecting the bottom to the neck of the flask, a stirrer, a thermometer, a dropping funnel and a reflex condenser. The circulation circuit, having an intra-circuit cagacity of 40 ml, was fitted with a circula-Lion pump and a cyanogen chloride gas inlet.
The 4-necked flask thus prepared was charged with 62.4 g of chlorosulfonyl isocyanate and 120.1 g of sulfur trioxide and, then, the feeding of cyanogen chloride gas (corresponding to 97.0 g) and 120.1 g of an liquid sulfur trioxide of r type was started at the same time, with stirring and circulating. The cyanogen chloride gas was fed over 5.5 hours, while the liquid sulfur trioxide was added dropwise over 5 hours. During the feeding, the temperature of the reaction gone was kept at 20 to 25°C by using an external bath. After the reaction had been completed, the reaction mixture was distilled under atmospheric pressure through a distillation column packed with glass helices and having an inside diameter. and a height of 1.5 cm and 17 cm respectively, to give 267 g of chlorosulfonyl isocyanate (purity: 96~) as a fraction at a boiling point of 106 to 107°C/760 mmFig... T.~e _yield based on the amount of cyanogen chloride used was 88~.
Example 5 A reaction vessel with a jacket and having a capacity of 100 ~ was mounted with a circulatian circuit having an infra-circuit capacity of 18 ~, a stirrer, a thermometer, a sulfur .trioxide feed port. The circulation circuit was fitted with a heat exchanger for cooling, a circulation pump and a cyanogen chloride gas inlet.
The reaction vessel thus prepared was charged first w~-th 33.3 kg of a crude chlorosulfonyl isocyanate solution ,.
containing 57~ by weight of chlorosulfonyl isocyanate, 19~ , by weight of sulfur trioxide and 221f by weight of chloro-pyrosulfonyl isocyanate, and then the feeding of a liquid sulfur trioxide of r type and cyanogen chloride gas was started at the same time under circulation of the solution.
The liquid sulfur trioxide was fed in an amount of 69 kg at a rate of 11.3 kg/hr and the cyanogen chloride gas in an ~~~~'v' - amount of SS kg at a rate of 8.9 kg/hr. During the feeding of the sulfur trioxide and the cyanogen chloride, the temperature of the reaction zone was kept at 15 to 22°C by using an external heat exchanger and the jacket.
After the reaction had been completed, the reaction mixture was distilled under reduced pressure through a distillation column packed with porcelain ~taschig rings and having an inside diameter and a height of 20 cm and 2 m, respecti~rely, to give 137 kg of chlorosulfonyl isocyanate (purity: 98~) as "~ fraction at a boiling poi~xt of 56°C/100 mmHg. The yield based on the amount of cyanogen chloride used was 91~.
Example 6 The same reaction vessel as used in Example 5 was charg-ed with 30.0 kg of a liquid sulfur trioxide of r type and, then, the feed of a cyanogen chloride gas (corresponding to 65.6 kg) and the liquid sulfur trioX:ide in an amount of 70.0 kg was started at the same time under circulation. The cyanogen chloride gas was fed over 7.5 hours, while the sulfur trioxide over 4.8 hours. During the feed the tempera-ture of the reaction zone was kept at 15 to 25°C by cooling.
After the reaction has been completed, the reaction mixture was distilled in the same manner as in Example 5, to obtain 135 kg of chlorosulfonyl isocyanate (purity: 95$) as a fraction at a boiling point of 55 to 56°C/100 mmHg. The yield based on the amount of cyanogen chloride used was 84$.
Comparative Example 1 °12-A 4-necked flask having a capacity of 200 ml was fitted with a stirrer, a thermometer, a reflux condenser and a drop-ping funnel. The 4-necked flask thus prepared was charged with 61 .5 g of a liquid cyanogen chloride and the contents was cooled to 0°C. To the contents 80.1 g of sulfur trioxide was added from the dropping funnel over about 1.5 hours. During the addition, the temperature of the reaction zone was kept at 0°C or below by using an external bath.
After the addition, the reaction zone was stirred for 2 hour at a temperaturewof~25~ to 30°C. After completion of the reaction, the reaction mixture was distilled with the same distillation column as used in Example 1 under atmospheric pressure to give 28.3 g of chlorasulfonyl isocyanate (purity: 72~) as a fraction at a boiling point of 10a to 108'C/760 mmFig. The yield based on the amount of cyanogen chloride used was 15~, Comyoarative Example 2 To 61.5 g of the liquid cyanogen chloride was added 80.1 g of the sulfur trioxide in the same manner as in Com parative Example 1. After the addition has been completed, the reaction zone was stirred for 2 hours at a temperature of 25 to 30°C. Then, the dropping funnel and the reflux condenser were taken off from the flask and the flask was fitted with a gas inlet of a glass tube having an inside diameter of 6 mm and such a length as to nearly reach the bottom of the flask and the same distillation column as used in Example 1.
:~ is r ~i~~~~ ~~ ~~
While the reaction mixture was being heated at a temperature of 100 to 130'C, about 60 g of cyanogen chloride was streamed into the reaction zone at a rate of about 0.01 mole/min to obtain crude chlorosulfonyl isocyanate as a dis--fillets withdrawn from the top of the distillation column.
When the amount of the bottoms in the flask reached about 5 ml, the introduction of eyanogen chloride gas was stopped and the distillation terminated. The crude product obtained was distilled under reduced pressure through the same distillation columil used in hxampie 2, to give 77.9 g of chlorosulfonyl isocyanate {purity: 87~) as a fraction at a boiling point of 52 to 56°C/100 mmHg. The yield based on the amount of cyanogen chloride used was 48~.
Comparative Example 3 A 4-necked flask having a capacity of 200 ml was fitted with a stirrer, a thermometer, a reflux condenser and a gas inlet of a glass tube having an inside diameter of 6 mm and a length nearly reaching the bottom of the flask. The 4-necked flask thus prepared was charged with 79.5 g of a liq-uid sulfur trioxide of r type and, then, cyanogen chloride gas (corresponding to 62.9 g) was introduced oust 2 hours with stirring. During the addition, the temperature of the 1 0 reaction zone was-kept ~ at 25 to 35°C by using an external bath. After the addition has been completed, the reaction zone was stirred for 0.5 hour at a temperature of 25 to 30°C. After completion of the reaction, the reflux condens-er and the gas inlet tube were removed from the 4-necked flask, and a distillation column packed with glass helices and having an inside diameter and a height of 1.5 cm and 10 cm respectively was fitted to they flask. The reaction mixture was distilled under atmospheric pressure to give 119.1 g of chlorosulfonyl isocyanate (purity: 90$) as a fraction at a boiling point of 106 to 107°C/760 mmHg. The yield based on the amount of cyanogen chloride used was 76$.
Com~arativca Example 4 The same apparatus as used in Comparative Example 3 was used. The flask was charged with 79.5 g of a liquid sulfur trioxide of r type and, then, 68.0 g of cyanogen chloride gas was introduced over 7 hour with stirring. During the addition the temperature of the reaction zone was controlled to be within a range of 20 to 48°C by using an external bath. After the addition the reaction zone was stirred for 1 hour at 30°C. Then, the reaction mixture was distilled under a reduced pressure of 100 mmHg through the same distil-lation column as in Comparative Example 3, to give 104.2 g of chlorosulfonyl isocyanate (purity: 95~~) as a fraction at a boiling point of 55 to 56°C/100 mmHg. The yield based on the amount of cyanogen chloride used was 70$.
Comparative Example 5 The same appax'atus as used in Comparative.Example 3 was used. The flask was charged with 117.6 g of a liquid sulfur trioxide of r type and, then, 89.7 g of cyanogen chloride 5~as was introduced over 6 hour with stirring. During the ad-dition the temperature of the reaction zone was adjusted to be 25 to 30°C by using an external bath. After the addition the reaction zone was stirred for 0.5 hour at 25 to 30°C.
Then, the reaction mixture was distilled under atmospheric pressure through the same distillai=ion column as used in 'Comparative Examgle 3, to give 91.2 g of chlorosulfonyl isocyanate (purity: 85$) as a fraction at a boiling point of 106 to 108°C/760 mmHg. The yield based on the amount of cyanogen chloride used was 38$.
Com ap rative Example 6 The same apparatus as in Comparative Example 3 was us-ed. The flask was charged with 79.5 g of a liquid sulfur trioxide of r type and, then, 89.7 g of cyanogen chloride gas was introduced over 10 seconds with stirring. During " the addition, the temperature of the reaction zone was adjusted to be within a range of 20 to 48°C by using an external bath. After the addition, the reaction zone was stirred for 1 hour at 25 to 30°C. Then, the reaction S mixture was distilled under atmospheric pressure through the same distillation column as used in Comparative Example 3, to give 68.8 g of chlorosulfonyl isocyanate (purity: 96~) as a fraction at a boiling point of 106 to 107°C/760 mmHg. The yield based on the amount of cyanogen chloride used was 47~.
. . .., . . ...- .
Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced 1S otherwise than as specifically descr:i.bed herein.
Claims (6)
1. In a batch process for producing chlorosulfonyl isocyanate by reacting sulfur trioxide with cyanogen chloride, the improvement which comprises: feeding sulfur trioxide and cyanogen chloride simultaneously to the reaction zone and maintaining the temperature of the reacting zone at 10° to 50°C.
2. A process for producing chlorosulfonyl isocyanate according to claim 1, wherein the reaction zone is charged with sulfur trioxide or an inert liquid containing chlorosulfonyl isocyanate prior to the start of the simultaneous feeding of sulfur trioxide and cyanogen chloride.
3. A process for producing chlorosulfonyl isocyanate according to claim 2, wherein said liquid containing chlorosulfonyl isocyanate contains chlorosulfonyl isocyanate in an amount of at least 40% by weight.
4. A process for producing chlorosulfonyl isocyanate according to claim 1, wherein the reaction zone is charged beforehand with a distilled mixture obtained by heating and decomposing the bottoms remaining after distillation of crude chlorosulfonyl isocyanate obtained by reaction of sulfur trioxide with cyanogen chloride.
5. A process for producing chlorosulfonyl isocyanate according to any one of claims l through 4, wherein cyanogen chloride is fed per unit time in a mole ratio based on the mole of sulfur trioxide of 0.6 to 1.1 during the simultaneous feeding of sulfur trioxide and cyanogen chloride.
6. A process for producing chlorosulfonyl isocyanate according to claim 5, wherein cyanogen chloride is fed per unit time in a mole ratio based on the mole of sulfur trioxide of 0.8 to 1Ø
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2024796 CA2024796C (en) | 1990-09-06 | 1990-09-06 | Process for producing chlorosulfonyl isocyanate |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2024796 CA2024796C (en) | 1990-09-06 | 1990-09-06 | Process for producing chlorosulfonyl isocyanate |
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| CA2024796C true CA2024796C (en) | 2001-02-27 |
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