Field of the invention:

The present invention relates to an improved process for the preparation of carbamoyl chloride and chloroformate by treating gaseous phosgene with respective gaseous amine and gaseous alcohol in continuous short path reactor (CSPR).

Background of the invention:

The gas phase process is a reactive diffusion of vapor and phosgene gas results in high level of exotherm in continuous cross flow pattern.

Higher the values of gas-gas diffusivity results in lower resistance to mass transfer, which make this reaction instantaneous hence possible to react in CONTINUOUS SHORT PATH REACTOR (CSPR).

As both the raw material (Amine or Alcohol with Phosgene) reacts in gas phase (Purest state of material) , Product produced by the method is having very high degree of GC purity (98-99 %) and high degree of molar yield which completely eliminates further purification steps. Present invention of process does not require any carrier solvent, chilling utility and agitation power for mixing.

Process can be carried out in a gas diffusion reaction chamber with a cross flow vapor – gas feed arrangement to avoid salt deposition. Product vapor leaves reaction chamber within less than 7 seconds and flow on shortest path i.e vertically down in tall falling film column where it cools down by natural convection and get condensate collection in bottom receiver. Non condensable vapor of generated HCl and excess phosgene gas leave from top of receiver to scrubbing system.
Various carbamoyl chloride and chloroformate are widely employed in a large number of applications in the agrochemical, pharmaceutical, and other allied industries. As a general Carbamoyl chlorides are produced by reacting various amines with phosgene in gas-liquid phase, while chloroformates are produced by reacting various alcohols with phosgene in gas liquid phase.

Carbamoyl Chloride:

As per reaction below, one mole of Amine (Primary or secondary Aliphatic, Aromatic, Al-Aryl) reacts with one mole of phosgene instantaneously and release a mole of hydrochloric acid and a mole of corresponding carbamoyl chloride. Reaction is highly exothermic. Processes generally require about 30-40 % molar excess amount of phosgene, for completion of reaction.

R-NH2 + COCl2 = R-CO-Cl + HCl

The process is very critical in terms of ratios of (Amine / Phosgene), for high ratios, product carbamoyl chlorides converts to urea.

R-COCl + R-NH2 = R-N-CO-N-R + HCl

Chloroformate:

As per reaction below, one mole of Alcohol (Primary or secondary Aliphatic, Aromatic, Alyl) reacts with one mole of phosgene instantaneously and release a mole of hydrochloric acid and a mole of corresponding chloroformate. Reaction is highly exothermic. Processes generally require about 20-35 % molar excess amount of phosgene, for completion of reaction.

R-OH + COCl2 = R-O-CO-Cl + HCl

The process is very critical in terms of ratios of (Alcohol / Phosgene), for high ratios, product chloroformate converts to carbonates.

R-O-CO-Cl + R-OH = R-O-CO-O-R + HCl

Normal Industrial methods are usually carried out in mild steel glass-lined reactors provided with reflux condensers, chilling jackets and mixing stirrers.

The prior art of various industrial scale methods for the production of carbamoyl chlorides & chloroformates have several disadvantages.
a. These include the fact that they are carried out necessarily batch operation mode.
b. It requires installations of large batch volume and large chilling capacity for the liquefaction of phosgene and for the chilling (0-5°C) of the reaction mass.
c. Furthermore, special costly construction materials (MSGL or Graphite or Hestalloy ) are necessitated by the corrosive character of the end product and of the hydrogen chloride by product.
d. The resulting crude product usually contains proportion of Urea and Carbonate impurities respectively in carbamoyl chlorides & chloroformate. which can generally be removed from the carbamoyl chlorides & chloroformates only by vacuum distillation.
e. Another disadvantage of the prior art processes is that , In batch process at any given time the reaction vessel contains a large amount of highly toxic phosgene which represents high hazardous potential in the case of any failure of equipment or unit operation.

Therefore there is a need of a process which overcome drawbacks associated with prior art processes.

Serendipitously, it is discovered that carbamoyl chlorides and chloroformate of desirably high purity can be produced by treating gaseous phosgene with respective gaseous amine and gaseous alcohol in continuous short path reactor (CSPR).

Object of the invention:

It is therefore an object of the present invention is to provide improved process for the preparation of carbamoyl chloride and chloroformate which gives high yield and purity without use of any power, utility and carrier solvent.

Another object of the present invention is to provide improved process for the preparation of carbamoyl chloride and chloroformate which is operationally simple, easy to handle and applicable at an industrial scale.

Another object of the present invention is to provide improved process for the preparation of carbamoyl chloride and chloroformate treating gaseous phosgene with respective gaseous amine and gaseous alcohol in continuous short path reactor (CSPR).

Another object of the present invention is to provide improved process for the preparation of carbamoyl chloride and chloroformate, the improvement which comprises treating gaseous phosgene with respective gaseous amine and gaseous alcohol in continuous short path reactor (CSPR).

Summary of the invention:

In one aspect, present invention provides improved process for the preparation of carbamoyl chloride and chloroformate treating gaseous phosgene with respective gaseous amine and gaseous alcohol in continuous short path reactor (CSPR).

In another aspect, present invention provides improved process for the preparation of carbamoyl chloride and chloroformate, the improvement which comprises treating gaseous phosgene with respective gaseous amine and gaseous alcohol in continuous short path reactor (CSPR).

Brief description of Figures:

Figure-1 is schematic sketch representation which discloses a process of the present Invention, where the gas phase reaction of Carbamoyl Chloride or Chloroformate was conducted in CSPR.

Part -1 of Figure- 1 indicates Gas Diffusion Chamber ( Figure -2 ) (150 mm diameter, 350 mm height and 5 mm thickness ) is facilitated with injection nozzles of vapors of Amines or Alcohols (25 mm) and Phosgene Gas (25 mm) in cross flow. A RTD is placed in gas mixing zone to measure the actual reaction temperature of vapor phase. As a specific design, the injection nozzle of Amines or Alcohols is ended in chamber wall instead opening into chamber, to avoid chock up in case of any salt formation due to HCl production in process.

Part – 2 of Figure-1 indicates a glass hollow vapor column (115 mm diameter and 2000 mm straight length, 5 mm thickness). Vertical vapor column provides sufficient gas phase residence time for natural draft ambient condensation. Product vapors of carbamoyl chlorides or chloro formats travels vertically downward and condensed to liquid phase in ambient conditions. However vapor of chloroformate sometimes required chilling utility to convert in liquid phase.

Part – 3 of Figure-1 indicates a spiral coil glass vaporizer which is used to vaporize Amine or alcohols in complete gas phase by using saturated steam as a heating medium. It operates in continuous counter current direction.

Part – 4 of Figure-1 indicates a peristaltic pump, which is used to pump amines or alcohols to vaporizer (3) from storage tank. It is a metering pump where flow is pre-calibrated

Part-5 of Figure-1 indicates a 50 Liters Glass receiver spherical tank, which collects all liquid product of carbamoyl chloride or chloroformate, produced after condensation.

Part – 6 of Figure-1 indicates a glass tube rota meter, which is used to measure the flow rate of phosgene gas charged to reaction chamber. It is pre-calibrated and can be used with accuracy of ± 0.1 kg/hr.

Part – 7 of Figure-1 indicates spiral coil glass condensers, which is used to trap and condense vapors of carbamoyl chloride or chloroformate lose from vent. Chilled water at temperature 5-10 °C is used as utility in vent condensers.

Detail description of the invention:

The “amine” used herein that includes but not limited to selected from substituted or unsubstituted amines such as primary amine, secondary amine, tertiary amine, triethyl amine, diethyl amine, methylamine, t-butylamine, di-N-propylamine, n-butylamine, isopropylamine and the like. The preferred amine is diethyl Amine.

The “alcohol” used herein that includes but not limited to selected from substituted or unsubstituted alcohols such as primary alcohol, secondary alcohol, tertiary alcohol, methanol, ethanol, butanol, isopropanol and the like. The preferred alcohol is methanol, ethanol and iso propyl alcohol.

The gas phase instantaneous reaction of carbamoyl chloride operates at high temperature e.g. Production of DECC - (Di-Ethyl Carbamoyl Chloride) at 180-240 °C, while the gas phase instantaneous reaction chloroformates operates at high temperature e.g. Production of MCF - (Di-Ethyl Carbamoyl Chloride) at 54-60 °C, so by product gas HCl vent off from process ( b.p. – 86 °C). ECF (Ethyl chloro formate) operates at 68-73 ° C, while IPCF (Iso propyl chloroformate) operates at 60-64 ° C.

Technology application novelty as a fact that the gas phase have highest values of inter diffusion parameters (gas-gas diffusivity), which is very large compare to any liquid- liquid or gas-liquid phases. Higher the values of gas-gas diffusivity results in lower resistance to mass transfer, which make reaction instantaneous in continuous mode reactor called as CONTINUOUS SHORT PATH REACTOR (CSPR). An additional advantage of the CSPR claims no agitator or stirrer or any mixing device required to mix gas phase.

CSPR have very short reaction residence time ( 5- 7 seconds) of the apparatus in accordance with the present invention allow good productivity when the starting ingredients are continuously introduced at one end and the finished carbonyl chloride or chloroformate is continuously recovered at the other. Being a continuous process, the production of these products claims low overhead requirements and raw material wastage.

The advantages of CSPR are,

1. It is continuous
2. It conducts instantaneous reaction
3. It doesn’t require any utility, power or solvent
4. Reaction vessel or complete set up is very small size and low cost.
5. It can be used with glass or compatible material
6. Hazardous potential: At any given time relatively small amounts of material are in the reactor, and even of these small amounts of material phosgene constitutes only a small proportion and since it immediately reacts with the amine or alcohol in the reaction zone only any stoichiometric excess which may have been employed is present in the free state. Therefore, if any malfunction of apparatus or accident occurs, the amount of phosgene which can escape is only very small.
7. Material inventory requirement will be minimum compared to conventional batch process

While the present invention has been described in terms of its specific embodiments, certain modifications and equivalents will be apparent to those skilled in the art and are intended to be included within the scope of the present invention.

The process of the present invention is described by the following examples, which are illustrative only and should not be construed so as to limit the scope of the invention in any manner.
EXAMPLE – 1
Preparation of Di-Ethyl Carbamoyl Chloride (DECC) in CSPR

Vapors of Di-Ethyl Amine (56 to 60 °C) at a rate of 3.4 kg/hr reacts in continuous cross flow with phosgene gas (25-30°C) at a rate of 6.3 kg/hr in gas phase. Reaction temperature ranges from 180-233 °C due to exothermic process. Product DECC vapor produced at a rate of 6.2 kg/hr, which is condensed atmospherically at ambient temperature (35-39 °C). Product DECC liquid have GC purity of 98.39 % and product have molar yield of 98.66 % based on Di-Ethyl Amine. About 38-40 % Excess phosgene gas is utilized for the completion of reaction and avoidance of Tetra Ethyl Urea impurity. However, A typical industrial process uses solvent (Toluene with DEA) to produce DECC. But the present invention uses, neat DEA is vaporized to react with phosgene gas. Which claims large amount of solvent to waive from process in production of DECC.

EXAMPLE – 2
Preparation of Methyl Chloro Formate (MCF) in CSPR

Vapors of Methanol (64-68 °C) at a rate of 3.4 kg/hr reacts in continuous cross flow with phosgene gas (25-30 °C) at a rate of 6.41 kg/hr in gas phase. Reaction temperature ranges from 54-58 °C due to exothermic process. Product MCF vapor produced at a rate of 5.5 kg/hr, which is condensed atmospherically at ambient temperature (35-39 °C) followed by chilled water (5-10 °C). Product MCF liquid has GC purity of about 98.39 % and product have molar yield of 98.66 % based on Methanol . About 20-30 % Excess phosgene gas is utilized for the completion of reaction and avoidance of Di-Methyl Carbonate.

EXAMPLE – 3
Preparation of Ethyl Chloro Formate (ECF) in CSPR

Vapors of Ethanol (80-85 °C) at a rate of 1.34 kg/hr reacts in continuous cross flow with phosgene gas (25-30 °C) at a rate of 4.0 kg/hr in gas phase. Reaction temperature ranges from 67.5-73.2 °C due to exothermic process. Product ECF vapor produced at a rate of 3.0 kg/hr, which is condensed atmospherically at ambient temperature (35-39 °C) followed by chilled water (5-10 °C). Product ECF liquid has GC purity of about 99.2 % and product have molar yield of 95.66 % based on Ethanol. About 30-40 % Excess phosgene gas is utilized for the completion of reaction and avoidance of Di-Ethyl Carbonate.

EXAMPLE – 4
Preparation of Iso Propyl Chloro Formate (IPCF) in CSPR
( with similar , scale down set up at lab scale )

Vapors of Iso Propyl Alcohol - IPA (85-88 °C) at a rate of 1.42 gm/min reacts in continuous cross flow with phosgene gas (25-30 °C) at a rate of 3.33 gm/min in gas phase. Reaction temperature ranges from 52-58 °C due to exothermic process. Product IPCF vapor produced at a rate of 2.77 gm/min, which is condensed atmospherically at ambient temperature (35-39 °C) followed by chilled water (5-10 °C). Product IPCF liquid has GC purity of about 96.6 % and product have molar yield of 95 % based on IPA. About 41.13 % Excess phosgene gas is utilized for the completion of reaction and avoidance of Di-Iso Propyl Carbonate.

A following data shows yield and purity of final product obtained according to process of present invention. This data is the best mode to illustrate utility of the invention.

Data for DECC (Diethyl chloro carbamoyl chloride):

TYPICAL VALUES:

Vapor Rate of Diethyl Amine : 4.0 kg/hr
Temperature of Diethyl Amine Vapor entering to Reaction : 54 – 56 ° C
Pressure of Diethyl Amine Vapor entering to Reaction : 1.0 kg/cm2 atmosphere
Phosgene Gas rate : 7.5 kg/hr
Temperature of Phosgene gas entering to Reaction : 25-35 ° C
Pressure of Phosgene gas entering to Reaction : 0.35 – 0.55 kg/cm2 gauge
% Excess Phosgene used in reaction over stoichiometry : 35-40 %
Temperature of Reaction zone : 180 to 240 ° C
Heat of Reaction : - 27.52 kcal/kg of DEA
Product rate of DECC liquid : 7.4 kg/hr
% Molar Yield (based on 100 % Purity) : 95 – 98 %
% GC Purity : 97 – 98 %

YIELD AND QUALITY DATA:

Sr. No. DEA
(kg/hr)
Avg. Phosgene
(kg/hr) DECC
(kg/hr) Phosgene
% Molar Excess % GC Purity % Molar Yield
DECC DEA 100 % Pure
1 1.85 3.50 3.39 40.00 98.18 0.00 97.07
2 2.35 4.58 4.33 44.36 98.36 0.26 97.86
3 1.55 3.00 2.83 43.36 98.27 0.02 98.30
4 3.34 6.30 6.56 39.72 97.92 0.02 97.40
5 3.40 6.41 7.67 39.65 98.39 0.01 97.07
6 18.36 34.55 32.73 39.35 98.52 - 94.90
7 21.89 41.05 39.63 38.89 98.74 - 96.60

Data for MCF (Methyl chloro formate):

TYPICAL VALUES:

Vapor Rate of Methanol : 1.85 kg/hr
Temperature of Methanol Vapor entering to Reaction : 54 – 56 ° C
Pressure of Methanol Vapor entering to Reaction : 1.0 kg/cm2 atmosphere
Phosgene Gas rate : 7.5 kg/hr
Temperature of Phosgene gas entering to Reaction : 25-35 ° C
Pressure of Phosgene gas entering to Reaction : 0.35 – 0.55 kg/cm2 gauge
% Excess Phosgene used in reaction over stoichiometry : 20-35 %
Temperature of Reaction zone : 54 - 60° C
Heat of Reaction : - 727.131 kcal/kg of Methanol
Product rate of MCF liquid : 5.4 kg/hr
% Molar Yield (based on 100 % Purity) : 97 – 98 %
% GC Purity : 98-99 %

YIELD AND QUALITY DATA:

Sr. No. Methanol
(kg/hr)
Avg. Phosgene
(kg/hr) MCF
(kg/hr) Phosgene
% Molar Excess % GC Purity % Molar Yield
MCF Methanol 100 % Pure
1 1.683 7.0 4.91 34.60 99.08 0.06 97.87
2 1.975 7.5 5.75 22.89 98.81 0.12 97.53
3 1.866 7.0 5.39 21.40 99.11 0.12 97.05

Data for IPCF (Iso Propyl chloro formate):

TYPICAL VALUES:

Vapor Rate of Iso Propyl Alcohol (IPA) : 3.0 gm/min
Temperature of IPA Vapor entering to Reaction : 85-88 ° C
Pressure of IPA Vapor entering to Reaction : 1.0 kg/cm2 atmosphere
Phosgene Gas rate : 6.75 gm/min
Temperature of Phosgene gas entering to Reaction : 25 - 35 ° C
Pressure of Phosgene gas entering to Reaction : 0.35 – 0.55 kg/cm2 gauge
% Excess Phosgene used in reaction over stoichiometry : 35-40 %
Temperature of Reaction zone : 60 -64 ° C
Heat of Reaction : - 134.319 kcal/kg of IPA
Product rate of IPCF liquid : 6.0 gm/min
% Molar Yield : 95.00 %
% GC Purity : 91-97 %

YIELD AND QUALITY DATA:

Sr. No. Iso Propyl alcohol
(gm/min)
Avg. Phosgene
(gm/min) IPCF
(gm/min) Phosgene
% Molar Excess % GC Purity % Molar Yield
IPCF IPA
1 2.96 6.66 5.30 36.36 95.84 2.8 87.97
2 3.14 7.00 5.43 35.11 91.54 3.37 89.77
3 1.42 3.33 2.77 42.13 96.6 2.19 95.00

Data for ECF (Ethyl Chloro Formate):

TYPICAL VALUES:

Vapor Rate of Ethanol : 1.5 kg/hr
Temperature of Ethanol Vapor entering to Reaction : 80 – 85 ° C
Pressure of Ethanol Vapor entering to Reaction : 1.0 kg/cm2 atmosphere
Phosgene Gas rate : 4.3 kg/hr
Temperature of Phosgene gas entering to Reaction : 25-35 ° C
Pressure of Phosgene gas entering to Reaction : 0.35 – 0.55 kg/cm2 gauge
% Excess Phosgene used in reaction over stoichiometry : 30-40 %
Temperature of Reaction zone : 67-73° C
Heat of Reaction : - 503.625 kcal/kg of Ethanol
Product rate of ECF liquid : 3.5 kg/hr
% Molar Yield : 91-96 %
% GC Purity : 96-99 %

YIELD AND QUALITY DATA:

Sr. No. Ethanol
(kg/hr)
Avg. Phosgene
(kg/hr) ECF
(kg/hr) Phosgene
% Molar Excess % GC Purity % Molar Yield
ECF Ethanol
1 1.34 4.0 2.99 40.54 99.2 0.05 95.66
2 3.04 8.0 6.81 23.90 96.16 1.75 96.78
3 1.78 5.12 4.11 35.17 99.10 0.01 91.77

The present invention by utilizing CSPR is further disclosed by following way of specific sketch for conducting gas-gas reaction, which is the best mode, contemplated for carrying out the invention.

Figure – 2: Gas Diffusion Chamber of CSPR