DE19707285A1 - Phosgenation of acids and / or anhydrides under pressure to produce acid chlorides - Google Patents

Abstract

Process for the phosgenation of monocarboxylic acids and/or anhydrides, characterized in that the acid and/or the anhydride is treated, in the presence or absence of solvent, with a molar excess of phosgene, preferably 2 to 15 times as much phosgene as acid, at temperatures between 80 and 200{C and at pressures between 2 and 60 bar, with or without catalyst, preferably in the absence of any catalyst. Process furthermore characterized in that pressure is used to facilitate the separation of the hydrochloric acid, the carbon dioxide and the phosgene, in a column which is external to the reactor.

Description

The present invention relates to a new method for Production of acid chlorides by phosgenation of Monocarboxylic acids and / or corresponding anhydrides under Pressure with or without catalyst, preferably in the absence unit of a catalyst.

In the conventional processes with catalyst Phosgene as such or in solution at usual pressures and into the acid at temperatures between 80 and 150 ° C injected. An excess is generally added Phosgene used. The exhaust gases made up of a mixture There are phosgene, carbon dioxide and hydrochloric acid, are not separable at normal pressures, unless they are coolers operating at very low temperatures are used whatever leads to loss of phosgene.

The reaction takes place after the following reaction equations:

(1) RCOOH + COCl₂ → RCOCl + HCl + CO₂ (k1)

(2) RCOOH + RCOCl ↔ (RCO) ₂O + HCl (k-2 / k2)

(3) (RCO) ₂O + COCl₂ → 2RCOCl + CO₂ (k3)

At normal pressure, reaction (1) is caused by the phosgene Concentration which is a function of temperature limited. The acid therefore becomes relatively quick consumed, but the acid chloride formed reacts with the acid present according to reaction (2) to form the Anhydride, the subsequent conversion of this Anhydride in the acid chloride is slow (reaction (3)).

It is therefore necessary to use one or more catalysts to be used to activate the reaction (3). Hence there is an abundance of literature on such catalysts goals. However, the use of a catalyst has many Disadvantage. First of all, it's about their costs and then their influence on the choice of materials, because the catalysts often make the reaction system very make corrosive. They also promote the formation of By-products (e.g. ketenes) and color development. Finally, the cleaning of the Acid chloride by distillation or crystallization connected.

An example of such a method is an example the French patent application FR 2 585 351 (EP 213 976) mentions the production of acid chlorides by phosgenation of the corresponding carbon acids is described. According to this document, the Use of a catalyst required to acid chloride under economically acceptable conditions receive. One of the subjects of EP 213 976 relates therefore in particular the catalyst that is used to carry out the Phosgenation reaction is used.

Furthermore, the applicant in EP 213 976 as document of State of the art an American patent (US-PS  2 657 233), which the applicant believes is the application a high pressure in combination with a high tempe disclosed for the preparation of acid chlorides. At the Reading this document, however, reveals that the Erfin in this case a process for the production of Dicarboxylic acid chlorides by phosgenation of the corresponding dicarboxylic acids under high pressure and at high Temperature concerns. This document correctly teaches that for the production of acid monochlorides described above bene conventional method is completely satisfactory and that basically an improvement is only expected can be optimized by the catalysts used, what the document FR 2 585 351 and for example documents FR 2 254 547 or EP 545 774 is confirmed.

By the invention, the above disadvantages mentioned are avoided, in particular with the use of catalysts in the prior art Technology related.

The invention provides a method for phosgenation of Monocarboxylic acids and / or anhydrides prepared by this is characterized in that the acid and / or the anhydride, in Presence or absence of a solvent, with a molar excess phosgene, preferably 2 to 15 times (molar) as much phosgene as acid, at temperatures of 80 up to 200 ° C and at a pressure of 2 to 60 bar (1 bar ≈ 105 Pa), with or without catalyst, preferably in deviation of a catalyst is treated. The procedure is generally in a closed system (auto gener pressure) or in an open system (the pressure will e.g. B. adjusted by partial degassing) performed. In general, the process is continuous or carried out semi-continuously. Preferably that is Partial degassing process in an open system  carried out. The degassing is generally so carried out to ensure that there is an excess of Phosgene remains. This happens either through selective removal of hydrochloric acid and Carbon dioxide, while at the same time excess phosgene and some HCl are retained (so that no anhydride is formed, but not so much that the reaction ends up is slowed down too much) or by degassing, including phosgene, and the latter at the same time is fed again. The temperature becomes more advantageous as in the range of 100 to 150 ° C, preferably 110 to 130 ° C, selected, whereas the pressure is preferably in Range from 6 to 40 bar is selected. The temperature- and printing conditions are determined by the type of monocarbon acid and / or the anhydride and the corresponding Chloride, especially through the critical point and / or the decomposition point.

The phosgenation under pressure according to the invention has the Advantages that a) low temperature cooler and b) solvent and / or catalysts are unnecessary. This allows the Final cleaning of the acid chloride obtained can be avoided, and it's the simple breakup after finishing the Implementation possible, which reduces the installation costs and there will generally be benefits that already exist were discussed above when there was no catalyst is. From Example 1 it follows that the addition effect achieved by a catalyst practically canceled will, d. H. that the productivity increase, through Application of the method according to the invention with a catalyst compared to the same process without a catalyst taking into account the disadvantages associated with ver using such a catalyst, very much is low. It also follows that Ver  drive according to the invention is possible without a catalyst, all the acid used in the chloride in a shorter time convert than using a conventional method Catalyst would be required. After all, that enables Method according to the invention an increase in productivity compared to the semi-continuous, batchwise Process at normal pressure.

The method according to the invention is advantageous for the chlorination of acids of the formula RCOOH to the acid chloride RCOCl used, where R is the following:

• - a linear or branched, saturated or unsaturated aliphatic residue with up to 22 coals atoms which are optionally substituted with a) one or more identical or ver different halogen atoms, b) one or more nitro groups or c) one or more aryl (preferably Phenyl), aryloxy or arylthio groups, each are unsubstituted or substituted,
• - A cycloaliphatic radical with 3 to 8 carbons atoms of matter that are unsubstituted or with one or is substituted by several substituents selected are under a) halogen atoms, b) alkyl or halogen alkyl radicals, c) nitro groups and d) aryl, aryloxy and Arylthio radicals, these aryl (preferably phenyl) or aryl derivatives are unsubstituted or substituted,
• - an aromatic carbocyclic residue, the unsub substituted or with one or more substituents is substituted under halogen atoms, alkyl or Haloalkyl radicals (preferably CF₃) with 1 to 12 carbons atoms, alkylthio or haloalkylthio with  1 to 6 carbon atoms, alkylsulfinyl or Haloalkylsulfinyl radicals having 1 to 6 carbon atoms, Alkylsulfonyl or haloalkylsulfonyl radicals with 1 to 6 Carbon atoms, alkyloxy or haloalkyloxy with 1 to 6 carbon atoms, aryl, arylthio or Aryloxy radicals and the nitro group are selected,
• - an aromatic or non-aromatic 5- or 6- membered heterocyclic radical, one or more identical or different heteroatoms has that under oxygen, sulfur and stick atoms are selected, and the unsubstituted or is substituted with one or more substituents which among halogen atoms, nitro groups and alkyl, halogen alkyl, alkyloxy, haloalkyloxy, aryl, arylthio and Aryloxy radicals are selected, and / or the optionally is fused to an aromatic carbocycle which itself is unsubstituted or substituted.

In general, when an aryl group (or one of the Derivatives thereof, e.g. B. aryloxy or arylthio) or a aromatic carbocycle mentioned be that even if this occurs at an such rest is not immediately specified to the front abbreviate description, this group Substi tuenten can wear that under halogen atoms and alkyl, Haloalkyl, alkyloxy, haloalkyloxy, alkylthio, Haloalkylthio, alkylsulfinyl, haloalkylsulfinyl, Alkylsulfonyl, haloalkylsulfonyl, aryl, aryloxy, Arylthio and nitro residues are selected.

The method according to the invention is also advantageous for the chlorination of anhydrides of the formula (RCO) ₂O or mixed anhydrides (RCO) O (OCR ′) to the acid chloride RCOCl  and R'COCl applied, where R and R 'as R defined above are, and R and R 'are not the same remainder at the same time represent.

The method according to the invention is also suitable for Chlorination of mixtures of acids and anhydrides.

The method according to the invention is further characterized by this characterized in that the pressure is also applied to any hydrochloric acid, carbon dioxide and phosgene in a column outside the reactor without Easier to separate using cryogenic coolers, by which, as stated above, there is a loss comes to COCl₂. The separation is therefore easier and thus more economical than with known methods and results Phosgene, which can be easily recycled, and pure hydrochloric acid.

The following examples illustrate the invention. she show the advantages of the method according to the invention Has.

example 1 Preparation of stearoyl chloride by exposure of phosgene on stearic acid (experiment No. 413)

0.175 g (0.615 mmol, concentration 0.41 M) stearic acid and 0.920 g (8.171 mmol) of chlorobenzene was put out into a tube Sapphire crystal (1) with an outer or inner through Weighed out a knife of 10 or 8 mm. This tube is like that designed to withstand high pressures. Then was also a sealed tube (2) with a Diameter of 5 mm, which contained deuterated benzene, in the tube (1) inserted to the presence of an outer Locksignals ensure that for the subsequent  NMR analysis is required. The tube (1) was then sealed, in an acetone / dry ice bath (-78 ° C) immersed and then connected to a phosgene bottle. Then 0.606 g (6.127 mmol) of phosgene (Concentration 4.08 M) condensed into the tube (1). After the reaction medium was warm to room temperature Form of a suspension of stearic acid in a colorless, homogeneous liquid. The tube was then in the Cryomagnets of an NMR spectrometer preheated to 117 ° C introduced. The first spectrum was 11 min after the Introduction to the cryomagnet recorded, d. H. to the Tuning the spectrometer and stabilizing the Reactor to the desired temperature corresponding period. With an automatic program was then the recording of Spectra at regular intervals (typically all 5 min) possible.

The mol% of each compound was determined by integrating the the methylenic protons in the α-position to the carbonyl Function determined triplets.

The results were as follows:

By working as in the example above and by varying different parameters (temperature, pressure, etc.) in the tables below Results

a) Influence of temperature

b) the presence of the catalyst described in Example 1 of FR 2 585 351

As stated above, this is due to the addition effect of a catalyst practically canceled,  d. H. the productivity increase resulting from application of the method according to the invention with catalyst in Ver with the same process without catalyst, is very low.

c) Influence of the phosgene concentration

d) influence of the solvent

e) Influence of degassing

The influence of working with (test 417) or without (test 413) degassing is shown in FIG. 1. Experiment 413 has already been described, and experiment 417 is the same, but using 0.16 g (0.56 mmol) acid, 0.875 g chlorobenzene and 0.88 g (8.9 mmol) phosgene. In run 417, when 90% of the acid was converted (after about 45 minutes), the tube was allowed to cool to degas and then reheated to 117 ° C after 0.99 g of phosgene had been reintroduced.

It can also be seen from Fig. 1 that there is a 100% Conversion of stearic acid in less than 2 h (approx 75 min when degassing the process at 117 ° C (Experiment No. 417)) is carried out). This is comparison of the invention with that in FR 2 585 351 given results possible. In this document Stearic acid actually completely in the chloride converted when the process in the presence of 0.02 mol% Catalyst at a temperature of 120 to 125 ° C. is performed, but in 4 hours. It is clear that that with the method according to the invention without a catalyst the conversion of all acid used into the chloride in a shorter time than with a conventional method Catalyst required would be possible, what is already above was found.

Example 2 Phosgenation of pivalic acid

• a) A first approach was carried out by performing a phosgenation reaction with the pure acid under pressure. Working as in Example 1 with a 10 mm multinuclear probe, but using deuterated pyridine as a lock signal instead of deu tered benzene, showed that the phosgenation under pressure from pivalic acid to the acid chloride is a first order reaction. The following results were obtained:
  • a1) at 81 ° C a rate constant of 0.28 h ^{-1 was} found (conditions: 0.75 g acid (7.3 mmol) and 1.5 g phosgene (15.2 mmol)).
  • a2) at 115 ° C a rate constant of 3.00 h ^{-1 was} found (conditions: 0.692 g acid (6.78 mmol) and 1.25 g phosgene (12.7 mmol)).
• b) Then a second examination was carried out, the kinetics of the phosgenation reaction of pivalic acid in chlorobenzene instead of the pure acid. in the Contrary to the investigation on the pure acid it is no longer possible, the CH₃ protons of the acid and Distinguish chloride, and consequently it is impossible follow the course of the reaction in chlorobenzene.

However, attempts have been made to remove the acid and the chloride Carbon NMR differentiate because of chemical Shifts (based on tetramethylsilane, TMS) of the Carbon atoms of the carbonyl groups and the quaternary Carbon atoms of the tert-butyl groups very under are different. Chemical shifts resulted in 185.8 ppm for COOH, at 180.8 ppm for COCl, at 38.9 ppm for the quaternary carbon atom of the acid and at 49.5 ppm for the quaternary carbon atom of the acid chloride. It an AMX-300 spectrometer was used, which was used for coal substance-13 was operated at 75 MHz and with a 10 mm Multi-core probe was equipped. The chemical diff Exercises (8) of the carbon resonance lines are in proportion to tetramethylsilane (TMS). As in a) deuterated pyridine used (for external lure).

Thereafter, the observation was carried out, which showed that the acid chloride predominates at 80 ° C. after 1 h 45 min,  although some acid remains (conditions: 0.06 g acid (0.6 mmol), 0.943 g chlorobenzene and 0.735 g phosgene (7.43 mmol)).

Example 3 Phosgenation of pivalic anhydride

Proton NMR analysis under pressure was carried out with an AMX 300 spectrometer that operated for the proton at 300 MHz and with a 5 mm QNP-1H / 13C / 19F / 31P gradient z- Probe was equipped. The chemical Shifts (δ) of the proton resonance lines are in the Relationship to tetramethylsilane (TMS) expressed. Either here as well as in Examples 4 to 6 the tube had made of sapphire crystal an outer or inner through knife of 5 or 4 mm.

As for 1H NMR analysis of the phosgenation reaction below Pressure of the pure acid (cf. 2a) it was possible to remove the CH₃- Protons of pivalic anhydride (δ = 1.24 ppm) and Distinguish acid chloride (δ = 1.31 pm).

The reaction was carried out at 80 ° C with a 3 molar excess performed on phosgene with respect to the anhydride.

If the negative natural logarithm of the relative molar fraction of pivalic anhydride is plotted as a function of time, a straight line results. The apparent order of reaction for the formation of pivaloyl chloride from pivalic anhydride is therefore 1. The slope of this line is equal to the reaction rate constant: k = 1.6 · 10 ^-2 min ^-1 . The half-life t 1/2, which is the time required for the concentration of the anhydride to decrease by half, is equal to ln 2 / k (t 1/2 = about 40 min).

Example 4 Phosgenation of octanoic acid

The procedure was as in Example 2a) and it resulted that that the phosgenation under pressure of the pure octanoic acid to Acid chloride is a first order reaction. It turned out the following results:

• 1) At 79 ° C there was a rate constant of 0.25 h ^-1 (conditions: 0.79 g acid (6.9 mmol) and 1.68 g phosgene (17 mmol)).
• 2) At 124 ° C there was a rate constant of 1.68 h ^-1 (conditions: 0.78 g acid (6.85 mmol) and 1.35 g phosgene (13.7 mmol)).

Example 5 Phosgenation of trifluoroacetic acid

Fluorine NMR analysis under pressure was performed on an AMX-300 Spectrometer carried out for the proton at 300 MHz was operated and with a 5 mm QNP-1H / 13C / 19F / 31P- Gradient z probe was equipped. The chemical ver shifts in the fluorine resonance lines are in relation to Trifluoroacetic acid (TFA) expressed.

The implementation was through the appearance of a resonance line at 0.3 ppm, which corresponds to trifluoroacetyl chloride, tracked with the acid at 0 ppm since it is the reference.

The implementation was slow because of the degree of conversion to that Chloride after heating for 4 hours at 107 ° C about 20% scam. This phosgenation reaction under pressure with pure  However, acid did occur (conditions: 0.22 g acid (1.93 mmol) and 0.464 g phosgene (4.7 mmol)).

Example 6 Phosgenation of benzoic acid

13C NMR analysis under pressure was carried out with an AMX-300 Spectrometer performed using carbon-13 Was operated at 75 MHz and with a 5 mm QNP 1H / 13C / 19F / 31P gradient z probe was equipped. The chemical shifts (δ) of the carbon resonance lines are in relation to tetramethylsilane (TMS) expressed.

It is very difficult to isolate the benzoic acid from 1H-NMR Distinguish acid chloride. For this reason, the Experiment with benzoic acid carried out with carbon 13 was enriched (the carbon of the carbonyl group), the kinetics of the reaction under pressure and at 90 ° C to track pure acid by NMR of this carbon-13. The carbon resonance lines of acid and acid chloride are at δ = 170 ppm and δ = 167 ppm.

If the negative natural logarithm of the relative molar proportion of benzoic acid is plotted as a function of time, a straight line results (conditions: 0.077 g acid (0.63 mmol) and 0.422 g phosgene (4.27 mmol) - temperature: 90 ° C ). The apparent reaction order of the formation of benzoyl chloride from benzoic acid is therefore 1. The slope of this line is equal to the reaction rate constant: k = 0.28 h ^-1 . The half-life t 1/2, which is the time required for the concentration of the acid to decrease by half, is equal to ln 2 / k (t 1/2 = about 2 h 30).

General procedure for experiments on a larger scale than with the previous ones

The following experiments were carried out in a 2 liter autoclave reactor carried out with a cooler and a Pressure control system was equipped. The total volume of the Autoclave and accessories was 2.25 l. Monochlorobenzene and the organic acid were in the completely anhydrous Reactor that had been purged with argon, then phosgene was added at about 20 ° C. The air valve was closed, and the The target opening of the control valve was set to the desired one Pressure set. Then the reaction medium became so rapid brought to 120 ° C as possible.

The percentages of acid, anhydride and chloride in the Reaction media were monitored by proton NMR certainly.

Example 7 Phosgenation of pivalic acid

61.3 g (0.6 mol) of pivalic acid and 890 g of monochlorobenzene were introduced into the reactor and then for about 597 g (6 mol) of phosgene were added for 30 min, the Temperature of the reaction medium kept at a maximum of 25 ° C. has been. The target pressure was set to 10.5 bar relative and heated the reaction medium. In the first 30 min About 0.3% anhydride was formed. The anhydride formed was phosgenated. The reaction was after about 2 hours Completely. The residual amount of acid was less than 0.5 mol%, the remaining amount of anhydride was 0 and amount of pivaloyl chloride obtained was greater than 99.5 mol%.  

Example 8 Phosgenation of 2-ethylhexanoic acid

87 g (0.6 mol) of 2-ethylhexanoic acid and 890 g of monochlorobenzene were introduced into the reactor and then for about 607 g (6.14 mol) of phosgene were added for 30 min, the Temperature of the reaction medium kept at a maximum of 25 ° C. has been. The target pressure was set to 10.5 bar relative and heated the reaction medium. The implementation was after one hour and 30 minutes completely. The remaining amount Acid and anhydride was 0 and the amount of 2- Ethylhexanoyl chloride was greater than 99.8 mole percent.

Example 9 Phosgenation of octanoic acid

86.6 g (0.6 mol) octanoic acid and 890 g monochlorobenzene were introduced into the reactor and for about 30 min 600 g (6.07 mol) of phosgene were added, the temperature the reaction medium was kept at a maximum of 25 ° C. Of the Target pressure was set to 10.5 bar relative and that Reaction medium heated. After 2 hours, the remaining amount was on Acid about 1 mol%, the remaining amount of anhydride 0 and the amount of octanoyl chloride obtained 99 mol%.

Example 10 Phosgenation of stearic acid

170.4 g (0.6 mol) stearic acid and 890 g monochlorobenzene were introduced into the reactor and for about 30 min treated with 594 g (6 mol) of phosgene, the temperature the reaction medium was kept at a maximum of 25 ° C. Of the The target pressure was set to 10.5 bar relative. The Reaction medium was heated to 120 ° C and at 1 h 30 min maintained at this temperature, whereupon it heated to 150 ° C and was held at this new temperature for 1 h. The rest then the amount of acid was about 1.4 mol%, the remaining amount  Anhydride 0 and the amount of stearoyl chloride obtained 98.6 mol%. The maximum pressure reached was 9 bar relative.

Example 11 Phosgenation of oleic acid

200 g (0.7 mol) of oleic acid and 725 g of monochlorobenzene were in introduced the reactor and then with 574 g (5.8 mol) of phosgene transferred. The target pressure was relatively set to 11.2 bar provides and the reaction medium heated. The implementation was complete after i hour 30 minutes. The remaining amount Acid was 0.5 mol% and the amount of oleyl obtained chloride 99.5 mol%.

Example 12 Phosgenation of p-toluic acid

81.4 g (0.6 mol) of p-toluic acid and 892 g of monochlorobenzene were introduced into the reactor and then with 582 g (5.9 mol) of phosgene added. The target pressure was on 11.2 bar set relatively and the reaction medium heated. The reaction was complete after 3 hours. The Analysis of the reaction medium finally obtained was performed by gas chromatography. The remaining amount Acid was 0.3 mol% and the amount of toluyl obtained chloride 99.7 mol%.

Example 13 Phosgenation of 2-furoic acid

110 g (0.98 mol) 2-furoic acid and 900 g monochlorobenzene were introduced into the reactor and then at 615 g (6.2 mol) of phosgene added. The target pressure was on 11.2 bar set relatively and the reaction medium heated. The pressure was turned on by adding argon poses. The reaction was complete after 3 hours. The  The residual amount of acid was 5.5 mol% and the amount obtained of 2-furoyl chloride 94.5 mol%.

Claims (11)

1. A process for the phosgenation of monocarboxylic acids and / or anhydrides, characterized in that the acid and / or the anhydride, in the presence or absence of a solvent, with a molar excess of phosgene at a temperature of 80 to 200 ° C and at a pressure of 2 to 60 bar, with or without a catalyst, is treated to obtain a monocarboxylic acid chloride. 2. The method of claim 1, wherein a 2 to 15 times molar excess of phosgene, based on the acid, is used. 3. The method according to claim 1 or 2, wherein the implementation is carried out in the absence of a catalyst. 4. The method according to claim 1, 2 or 3, characterized, that the process by partial degassing in one open system. 5. The method according to any one of the preceding claims, characterized, that the temperature is 100 to 150 ° C.   6. The method of claim 5, wherein the temperature is 110 is up to 130 ° C. 7. The method according to any one of the preceding claims, characterized, that the pressure is 6 to 40 bar. 8. The method according to any one of the preceding claims, characterized in that a monocarboxylic acid of the formula RCOOH is converted into the acid chloride RCOCl, where R is the following:

• - A linear or branched, saturated or unsaturated aliphatic radical with up to 22 carbon atoms, which is optionally substituted with a) one or more identical or different halogen atoms, b) one or more nitro groups or c) one or more aryl (preferably Phenyl), aryloxy or arylthio groups, each of which is unsubstituted or substituted,
• - A cycloaliphatic radical with 3 to 8 carbon atoms, which is unsubstituted or substituted with one or more substituents, which are selected from a) halogen atoms, b) alkyl or haloalkyl radicals, c) nitro groups and d) aryl, aryloxy and Arylthio radicals, these aryl (preferably phenyl) or aryl derivatives being unsubstituted or substituted,
• - An aromatic carbocyclic radical which is unsubstituted or substituted by one or more sub-substituents, the halogen atoms, alkyl or haloalkyl radicals (preferably CF₃) having 1 to 12 carbon atoms, alkylthio or halogeno alkylthio radicals having 1 to 6 carbon atoms, alkyl sulfinyl or haloalkylsulfinyl radicals having 1 to 6 carbon atoms, alkylsulfonyl or haloalkyl sulfonyl radicals having 1 to 6 carbon atoms, alkyloxy or haloalkyloxy radicals having 1 to 6 carbon atoms, aryl, arylthio or aryloxy radicals and the nitro group,
• - An aromatic or non-aromatic 5- or 6-membered heterocyclic radical which has one or more identical or different heteroatoms selected from oxygen, sulfur and nitrogen atoms, and which is unsubstituted or substituted with one or more substituents is selected from halogen atoms, nitro groups and alkyl, haloalkyl, alkyloxy, haloalkyloxy, aryl, arylthio and aryloxy radicals, and / or which is optionally fused to an aromatic carbocycle which is itself unsubstituted or substituted.

9. The method according to any one of claims 1 to 7, characterized, that an anhydride of the formula (RCO) ₂O or a ge mixed anhydride (RCO) O (OCR ′) in the acid chloride RCOCl and R'COCl is converted, with R and R 'as R are defined in claim 8 and R and R 'are not represent the same rest at the same time. 10. The method according to any one of claims 1 to 7, characterized,  that a mixture of acid and anhydride in the Monocarboxylic acid chloride is converted. 11. The method according to any one of the preceding claims, characterized, that the separation of hydrochloric acid and Carbon dioxide formed by the reactions be carried out, and phosgene in a column which is located outside the reactor.