FR2621913A1 - PROCESS AND DEVICE FOR THE PRODUCTION OF CHLORINATED CHLOROFORMIATES - Google Patents

Abstract

The invention relates to a process for the production of monochloromethylchloroformate and trichloromethylchloroformate by chlorination of methyl ester of chloroformic acid. According to the process is chlorinated in a first step at 60-70 degree (s) C until the ester is converted to 50% at most, then the reaction mixture is separated by rectification and the methyl ester of Unconverted chloroformic acid is returned to the reactor. In the reactor, the molar ratio between ester and chlorine gas is between 3/1 and 2/1. The monochloromethylchloroformate produced during the rectification as a bottom product is either discharged as a finished product, or else introduced in whole or in part into another photoreactor in which the molar ratio between the monochloromethylchloroformate and the chlorine gas is 1/2 to 1/3 and the temperature 90 to 110 degree (s) C. The reaction product is separated by rectification, the overhead product is returned to the second reactor while the trichloromethylchloroformate which is produced at the bottom of the column is discharged as the finished product. The invention further relates to an installation suitable for carrying out the process continuously.

Description

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  METHOD AND DEVICE FOR MANUFACTURING

CHLOROFORMIATES CHLORES.

  The invention relates to a method that can be used industrially for

  the manufacture of chlorinated chloroformates by photochlorination of

  ter methyl chloroformic acid. The invention furthermore relates to

  a device for executing the method.

  Chlorinated formates have been described for the first time

  is just one hundred years old in the specialized literature (W. Hentschel, J. Prakt.

  Chemie (2) 36, 99/1887). Then we did not publish anything for a long time on these compounds, because they carried out researches on these especially for military purposes. After the First World War, more publications about them were published, especially the results of the research of Grignard et al (Rend, 169, 1074-1076).

  1919) as well as A. Kling et al (Appraisal 169, 1046-1047 / 1919).

  These publications have described the physical and chemical properties of

  These compounds are mono-, di- and trichloromethylchloroformates, manufactured in the laboratory by chlorination of the methyl group, as well as the resistance to decomposition, in particular hydrolysis, of these compounds. Photochlorination of the chloroformate was carried out under conditions

  laboratory, with use of light.

  Photochloration was studied in the 1950s by T. L Bakt et al. at room temperature and using tetrachloride

  carbon as solvent (J. Chem Phys 17, 566-573 / 1949).

  The manufacture of chlorinated chloroformates and the study of their

  reactions until the sixties mainly

  and it was only then that the first articles appeared

  first patents which were directed towards an industrial exploitation

compounds.

  Hungarian Patent No. 176083 describes the manufacture of isocyanates from chloromethylchloroformate, and according to Hungarian Patent No. 190681 chloromethylchloroformate is used for the manufacture of

chloracetanilides.

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  It is natural that, in parallel with this, active research has been carried out on the manufacture of chlorinated chloroformates, and several patents concern this object. As in photochemical chlorination

  chloroformate, as described in the literature.

  According to the cited specification, the three chlorinated derivatives, the monochlorinated derivative, the dichlorinated derivative and the trichloro derivative are formed, and the separation of these three compounds is rather difficult because of their boiling points, which are hardly distinguishable from one another. on the other hand,

  research was done in other directions.

  DE-PS 3241 568 describes the manufacture of

  poses obtained by the reaction of formaldehyde and phosgene in the gas phase at the temperature of -10 to + 60 C. The essential prerequisite for this process is the use of a formaldehyde monomer gaseous dry. For the reaction, substituted amides or tetrasubstituted ureas or thioureas are recommended as

  catalyst. With the process, a yield of 60 to 70% can be obtained.

  The preparation of the anhydrous monomeric formaldehyde, which for descriptive purposes can be derived from paraformaldehyde by means of a depolymerizer, presents

difficulties.

  The manufacture of a large number of chlorinated chloroformates is described in Hungarian Patent No. 191179. The o-chlorinated derivatives are

  obtained by a transformation, intervening in a solvent medium, of alde-

  substituted and phosgene hydes in the presence of an organic or inorganic catalyst / which is capable of forming a pair of ions, one of which is a halogen ion and the other a nucleophilic cation. The two processes described are not essentially suitable for industrial manufacture. Thanks to its own tests, it has studied in depth the

  process of chlorination of methyl ester of chloroformic acid.

  The process of thermal chlorination, photochlorination, film

  of the formation of monochlorinated, dichlorinated and trichlorinated derivatives, the

  their formation, the conversion of chloroformate, the selec-

  The transformation and thermal decomposition of the three derivatives have been extensively researched. Since, of the three-chlorinated derivatives, the dichlorinated derivative is the least important for the subsequent implementation, and moreover the least stable, the object of the invention was to find an industrially usable process by means of which

  monochloromethylchloroformate, trichloro-

  methylchloroformate or both.

  The invention is based on the observation that photochromic

  the methyl ester of chloroformic acid must be

  at a temperature in the immediate vicinity of the boiling point

  approximately 60 to 70 C, and that chlorination should not be

  followed beyond a 50% conversion of the methyl ester. The

  reaction mixture produced in this manner is then separated by recom-

  tification and the methyl ester of chloroformic acid is introduced

  in the reactor after separation of the gaseous and liquid phases

  performed in an absorber, together with the methyl ester of fresh chloroformic acid. The amount of methyl ester

  fresh chloroformic acid introduced, and methyl ester of the

  recycled chloroform is about 1/1 to 1 / 1.5. In the reactor

  a molar ratio of 3/1 to 2/1 must be maintained between the methyl ester

  chloroformic acid and chlorine.

  Monochloromethylchloroformate is recovered at the outlet of

  the rectification unit after cooling to room temperature

  ature. If the trichloro derivative is to be manufactured, the monochloro-

  methylchloroformate is conducted in a photochloration reactor arranged subsequently, and is transformed therein by means of chlorine in the vicinity

  boiling point, at a temperature of 90 to 110 C. In this reaction,

  the molar ratio of monochloromethylchloroformate to

  Chlorine gas should be maintained between 1/2 and 1/3.

  From the photochlorination reactor, the reaction mixture is

  in the rectification unit, o, at a head temperature of 110 to 120 ° C, a mixture which contains dichloromethylchloroformate

  and trichloromethylchloroformate in approximately equal portions.

  In a cooled absorber which follows the rectification column the gas exiting the photochlorination reactor is washed with the top product of the column, i.e., the cited mixture. Then this

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  washing liquid is reintroduced at the same time as monochloromethyl-

  chloroformate in the reactor, the product collected at the bottom of the rectification unit is cooled; it is trichloromethylchloroformate

practically pure.

  With the process according to the invention, monochloromethylchloroformate and trichloromethylchloroformate can be produced as well.

  in a discontinuous way that also continuously.

  The object of the invention is also a device by means of which the two chlorinated chloroformates can be manufactured separately.

  on the other or simultaneously, continuously and on an industrial scale.

  The device is described in more detail by means of the appended drawing.

  The device according to the invention contains two photoreactors equipped with a heating body and an illumination body for the treatment

  by light radiation, to which are connected

  disposal, recycling and disposal of materials. The device is further provided with grinding units for the separation of

  reaction mixtures and connected in series to the reactors, and

  coolers for separating gas and liquid.

  In photoreactor 3 for producing monochloromethyl

  chloroformate, equipped with heating and illumination

  formate arrives through the piping 1, chlorine gas through the pipe-

  2. The photoreactor 3 the reaction mixture is brought by the con-

  5 in the rectification unit 6, the top product of which reaches the cooled absorber 8 via the pipe 7. The vapors and the gases

  from reactor 3 are also fed through the tubular conduit.

  4, in the absorber 8, in which the vapors condense,

  and from which the gaseous hydrochloric acid leaves via the conduit 21.

  The condensate coming from the absorber 8 is introduced via the pipe 9 into the pipe I and reintroduced into the photoreactor 3 in

  same time as the fresh methyl chloroformate being fed. -

  The monochloromethylchloroformate is withdrawn from the rectification column 6 via the pipe 10. It is either evacuated as a product

  finished, either in whole or in part brought by the line II in the

  toreactor 13 equipped with heating body and illumination body, in

  which chlorine gas is introduced via line 12.

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  the reaction mixture is conducted in the rectification unit

  16 through the tubular conduit 15. The top product of this

  through the conduit 17 into the cooled absorber 18, in the

  the vapors in the condenser from the reactor

  13 through line 14 are condensed and wherein the liquid is separated from gaseous hydrochloric acid. The condensate is brought back

  by the duct 19 in the duct 11 and from there reintroduced into the

  toruator 13 together with monochloromethylchloroformate. The trichloromethylchloroformate is withdrawn from the system via the tubular conduit 20, while the gaseous hydrochloric acid which is evolved as a by-product is fed through line 21 into a system.

  adiabatic absorption of hydrochloric acid.

  Two tubular circulation duct circuits 22,

  23 whereby the liquid-gas ratio can be regulated in the absorbers are connected to the two absorbers; this is

  important, especially when starting the installation.

  The continuous execution and discontinuous execution of the method according to the invention is explained in more detail, in correspondence with the following examples of execution: however, the invention is not limited to these examples. For batch operation, three-necked flasks equipped with 500 ml volume heating and cooling devices were used in which the illumination was carried out by means of a mercury vapor lamp of a volume of 500 ml. power of 100 W. Chlorine gas was introduced into the bottom of the balloon through a tubular conduit, while a neck of the balloon was used for evacuation

  gas and that the second was used to supply chloroformate.

Example 1

  Comparative Example for Photochloration at Ambient Temperature

  ature. About 90 ml of methyl chloroformate are introduced into the flask and the temperature is set at 30 ° C. and maintained at this value until the end of the introduction of the gas. The gas supply speed is 45.6 g / h. Samples are taken from the reaction mixture and the conversion of methyl chloroformate and the selectivity and yield of the formation of monochloromethylchloroformate, dichloromethylchloroformate and trichloromethylchloroformate are determined. The results are presented in the following table by which it can be clearly seen that the speed of the transformation is not sufficient at the chosen temperature. Parameters O min. 30 min. 150 min. Conversion of chloroformate,% 0 24.1 96.0

Monochlorine derivative -

  Selectivity,% - 92.1 63.8 Yield,% 0 22.2 61.2 Dichloro derivative Selectivity,% - 7.9 33.9 Yield,% O 1.9 32.5 Trichloro derivative Selectivity,% - 0 2 , 4 Yield,% O 0 2,3

Example 2

  The device of Example 1 is used, 90 ml of

  methyl formate in the flask, the temperature is maintained at 70 ° C. and 124.1 g of chlorine gas are introduced per hour. The parameters are

gathered as in Example 1.

  Parameters O min. 45 min. 120 min. Chloroformate conversion,% 0 87.9 100 Monochlorine derivative Selectivity,% - 70.5 0 Yield,% 0 61.9 0 Dichlorinated derivative Selectivity,% - 29.6 0.2 Yield,% 0 26.0 0.2 Trichloride derivative Selectivity,% - O 99.8 Yield,% 0 0 99.8

Example 3

  As described in Example 2, 90 ml of chloroformate -7-

  of methyl are converted to 70 C with chlorine gas which is

  troduced at a speed of 124.1 g / h. However, the reaction is interrupted

  stinks after 40% of the starting compound has been converted. It lasts minutes. Then the reaction mixture is separated by fractional distillation. Monochloromethylchloroformate was formed with a selectivity of 99.7%. 58.9 g of monochlorinated derivative were obtained, which

  relative to the transformed chloroformate, corresponds to a yield of 98%.

Example 4

  The 58.9 g of monochloromethylchloroformate obtained according to the example

  3 are placed in the flask and further chlorinated at 120 C until

  complete transformation. 90.4 g of trichloromethylchloroform are obtained

  miate, which corresponds, with methyl chloroformate, to a yield of 98%.

Example 5

  The continuous process is carried out in a laboratory device mounted in correspondence with the drawing, made of glass. The device consists of two cylindrical glass reactors (3, 13) 400 mm high, 40 mm in diameter, two glass rectification units (6, 16) and two absorbers (8, 18). glass. In the reactor is suspended the mercury vapor lamp with a power of 80 W surrounded by a glass envelope 35 mm in diameter as a light source. Chlorine gas arrives in the reactor through glass pipes (2, 12), chloroformic acid methyl ester through a tube

  of glass (1), with the non-trans-form chloroformic acid methyl ester

  formed, brought back from the absorber by the glass tube (9). From the upper end of the reactor a glass tube (6, 16) for discharging vapors and gases leads to the absorber (8, 18). The reaction mixture exits the reactor via line (5, 15) and enters the respective rectification unit (6, 16). The unit of

  rectification consists of a heated boiling flask whose volume

  me is 500 ml, a column filled with Raschig rings placed

  above it, and a straight tube cooler connected to this column. The top product reaches via ducts (7, 17) in

  absorber (8, 18), which is a straight tube cooler

  50 cm long, whose lower end is connected to the tube --8--

  glass (6, 16) which discharges the gas-vapor mixture out of the reactor.

  In this device, and indeed in the first photo reactor

  chlorination is introduced 114 g per hour (1.2 Mok) of methyl ester of fresh chloroformic acid and 170 g (1.8 MoI of methyl ester

  chloroformic acid, as well as 86 g (1.2 Mok) of chlorine

  gaseous. The temperature of the reactor is set at 70 C and one branch

the illumination lamp.

  From the reactor 324 g of reaction mixture (which is constituted by 47% of monochloromethylchloroformate and 53% of methyl ester of chloroformic acid), which pass into the boiling flask of the rectification unit, are discharged per hour. . From this g of overhead product at a temperature of 70.4 ° C are passed into and out of the absorber and back into the reactor. As a bottoms product, 155 g per hour is withdrawn.

  of monochloromethylchloroformate which is purified by distilling

keep on going. Yield: 152 g (98%).

Example 6

  The 155 g / h of monochloromethylchloroformate manufactured according to

  Example 5 are conducted in the second reactor which is simultaneously

  supplied with 170 g per hour (2.4 Me) of chlorine gas.

  The temperature of the reactor is set at 100 ° C. From the reactor are

  in the boiling flask of the grinding unit 310 g

  reaction mixture (which is 90% trichloromethane).

  thylchloroformate and 10% by dichloromethylchloroformate) simul-

  73 g of a mixture at a temperature of 112 ° C are withdrawn as overhead product (the mixture is constituted at 45% by

  dichloromethylchloroformate and 55% by trichloromethylchloroform

  miate) and leads to the absorber, then from the latter to the reaction

  tor. The absorbers used for the separation of the gas phase and

  They operate at temperatures between 0 and 10 ° C. At the bottom of the rectification unit, 238 g per hour of product are withdrawn.

  which is batch distilled. 233 g per hour (98%) of trituration are obtained.

chlorométhylchloroformiate.

Example 7

  In the photoreactor of the laboratory device according to the

  The glass fabric is charged with 142 g per hour (1.5 mol) of fresh methyl chloroformate, 140 g of recycled methyl chloroformate from the absorber and 107 g (1.5 mol) of chlorine. gaseous. The temperature of the reactor is set at 70 ° C. 336 g of reaction mixture (consisting of 43% of methyl chloroformate and 57% of monochloromethylchloroformate) are withdrawn per hour.

  which is sent into the boiling flask of the rectification unit.

  141 grams of head product are withdrawn from the rectification unit at a temperature of 70.6 ° C., which is cooled in the absorber at 0 ° C. and from there is returned to the reactor. As a unit bottom product

  of rectification 193 g of monochloromethylchloro are withdrawn per hour

  formate which is purified by batch distillation. yield:

  188 g (97%) of monochloromethylchloroformate.

Example 8

  The 193 g of monochloromethylchloroformate produced according to Example 7 are introduced into the photoreactor operating at 100 ° C. and 214 g (3 MolU of chlorine gas) are introduced per hour.

  per hour 478 g of reaction mixture (consisting of 17% dichloromethane

  methylchloroformate and 83% trichloromethylchloroformate) from the reactor to the rectification unit. From this unit 181 g of liquid

  at the head temperature of 112 C (constituted by 45% of dichloro-

  methylchloroformate and 55% trichloromethylchloroformate)

  are sent into the absorber and thence they are recycled in the reactor.

  The absorber is cooled to 10 C. The rectification unit is

  drawn per hour 292 g of crude product which is distilled in batches. yield

  285 g (96%) of trichloromethylchloroformate.

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Claims (2)

  Process for the production of chlorinated chloroformates by photochlorination of methyl chloroformate, characterized in that the photochlorination is carried out at a temperature of 50 to 70 ° C. and with a molar ratio of methyl chloroformate / chlorine gas of between 3: 1. and 2/1, that the reaction mixture is separated by fractionation and that an overhead product having a temperature between 70 and 80 ° C is returned to the reactor after being brought into contact with the gas-vapor mixture leaving the reactor, a ratio of 1/1 to 1 / 1.5 being maintained between the methyl chloroformates   fresh and recycled, that after separation the monochloromethylchloro-   formate is evacuated or reduced in whole or in part   photochloration agent operating at a temperature of 90 to 110 C, a molecular ratio of between 1/2 and 1/3 being maintained between the monochloromethylchloroformate and the chlorine gas, then the reaction mixture is fractionated, a product of head having a temperature of 110 to 120 C is contacted with the gas-vapor mixture leaving the reactor and then the mixture consisting at least half of trichloromethylchloroformiate is returned to the reactor and that the trichloromethylchloroformiate which is removed   is produced as a bottom product.   2. Device for the production of chlorinated chloroformates, consisting of photoreactors connected in series, rectification units and absorbers, characterized in that a tubular conduit (2) for the introduction of the photoreactor (3) is connected to the photoreactor (3). chlorine gas, a tubular duct (5) for discharging the reaction mixture and a tubular duct (4) for discharging the gas-vapor mixture, the rectification unit (6) for fractionating the mixture of reaction is connected to a tubular conduit (7) for discharging the overhead product and the absorber (8) for separating the gas-liquid mixture is connected to a tubular conduit (9) for recycling, and   the grinding unit (6) comprises a duct (10) for   evacuation of the bottom of column, to which is connected another 2621 9 13   A photochlorination reactor (13) having a conduit (11) for supplying monochloromethylchloroformate, a conduit (12) for supplying chlorine gas, a conduit (14) for   vapor evacuation and a conduit (15) for the evacuation   cuation of the reaction product, that the conduit (15) leads to a second rectification unit (16) which is connected via a   conduit (17) for discharging the overhead product to another   separator (18) for phase separation, which is connected to the reactor (13) via a recycle line   and has a conduit (21) for discharging chlorhydric acid   gaseous distillation, and that the grinding unit (16) has a   duit (20) for the disposal of the finished product (bottom product).