Field of the invention
The present invention provides a process for preparation of trichlorodifluoro propane compound of Formula 1.

wherein X1 and X2 represents chlorine or fluorine; provided that X1 and X2 are not same.
Background of the invention
Trichlorodifluoropropane compounds are important intermediates in synthesis of various hydrofluoroalkenes. These hydrofluoro alkenes possess several applications e.g., 2,3,3,3-tetrafluoropropene and 1,3,3,3-tetrafluoropropene are used as refrigerants.
Various methods are known in the art which discloses use of hydro(halo)fluoroalkane as an intermediate in the synthesis of hydrofluoro alkenes in general. e.g., U.S. Patent No. 8,546,623 uses C1-3 (hydro)fluoroalkanes as intermediates for synthesis of various C1-3 hydro(halo)fluoroalkanes.
The inventors of the present invention provides an alternate process for preparation of trichlorodifluoropropanes.

Object of the invention
The object of the present invention is to provide a cost effective and improved process for preparation of trichlorodifluoro propane compound of Formula 1.

wherein X1 and X2 represents chlorine or fluorine; provided that X1 and X2 are not same.

Summary of the invention
In first aspect, the present invention provides a process for preparation of a compound of Formula 1,

wherein X1 and X2 represents chlorine or fluorine; provided that X1 is not same as X2,
comprising the steps of:
a) reacting carbon tetrachloride with ethylene in presence of a metallic catalyst to obtain reaction mixture 1 comprising 1,1,1,3-tetrachloropropane;
b) de-hydrohalogenating the reaction mixture 1 to obtain a reaction mixture 2, comprising trichloropropenes;
c) fluorinating the reaction mixture 2 to obtain the compounds of formula 1.
In second aspect, the present invention provides a process for preparation of compound of Formula 1,

wherein X1 and X2 represents chlorine or fluorine; provided that X1 is not same as X2,
comprising the steps of:
a) de-hydrohalogenating 1,1,1,3-tetrachloropropane to obtain a mixture comprising trichloropropenes;
b) fluorinating the mixture of step a) to obtain the compounds of formula 1.
In third aspect, the present invention provides a process for preparation of compound of formula 1,

wherein X1 and X2 represents chlorine or fluorine; provided that X1 is not same as X2,
comprising the step of fluorinating a mixture of trichloropropenes to obtain the compounds of formula 1.

Detailed description of the invention
As used herein, the “reaction mixture 1” comprises of 1,1,1,3-tetrachloropropane, ethylene and carbon tetrachloride.
As used herein, the “reaction mixture 2” comprises of 1,1,3-trichloroprop-1-ene and 3,3,3-trichloroprop-1-ene.
The compound of formula 1 refers to 1,1,3-trichloro-1,2-difluoropropane and 1,1,1-trichloro-2,3-difluoropropane.
As used herein, the term “catalyst” refers to the metallic catalysts and organic ligands that form suitable catalyst complexes.
As used herein, the term “metallic catalyst” refers to elemental powders, salts, and organometallic compounds of the transition metals. The preferred metallic catalysts include copper and iron. Exemplary cuprous salts and organometallic cuprous compounds include, without limitation, cuprous chloride, cuprous bromide, cuprous cyanide, cuprous sulfate, and cuprous phenyl. Exemplary iron salts and organometallic ferrous compounds include, without limitation, ferrous chloride, ferric chloride, Tris (2,2'-bipyridine) iron (II) hexafluorophosphate. Exemplary copper and iron powders preferably are fine, substantially pure powders having a particle size no greater than about 100 mesh, and preferably no greater than about 325 mesh. The more preferred metallic catalysts include cuprous chloride and iron powder.
As used herein, the term “The organic ligand” refers to the compound capable of forming a complex with a metallic catalyst having the properties and attributes as described above. Suitable organic ligands include amines, nitrites, amides, and phosphates. Examples of preferred nitrites include, for example, acetonitrile, pentanenitrile, benzonitrile, and tolunitriles. Examples of preferred amides, for example, N-ethylacetamide, acetanilide, aceto-p-toluidide, and hexamethlyenephosphomamide. Examples of preferred phosphates include, for example, trimethylphosphate, triethylphosphate, tributylphosphate, and triphenylphosphate. In a particular embodiment, the reaction between ethylene and carbon tetrachloride is carried out in presence of metallic catalyst and a phosphate ligand to produce 1,1,1,3-tetrachloropropane.
As used herein, the step of de-hydrohalogenating involves eliminating hydrogen chloride from tetrachloropropane and introducing a double bond to produce trichloropropene.
In an embodiment, the step of de-hydrohalogenation is carried out a base in presence of phase transfer catalyst.
Examples of base include an organic or an inorganic base or the mixtures thereof. Examples of inorganic base includes alkali metal hydroxides selected from lithium hydroxide, sodium hydroxide, potassium hydroxide and alkaline earth metal hydroxides selected from calcium hydroxide and magnesium hydroxide. The organic bases are selected from the group consisting of alkali metal alkoxides, and the like. Examples of alkali metal alkoxide includes sodium methoxide, sodium ethoxide, sodium propoxide, sodium isopropoxide, sodium butoxide, sodium tertiary butoxide or potassium methoxide, potassium ethoxide, potassium propoxide, potassium isopropoxide, potassium butoxide, potassium tertiary butoxide and the like.
Examples of phase transfer catalyst include crown ethers; cryptates; polyalkylene glycols or derivatives thereof; and onium salts. Examples of crown ethers includes 18-crown-6 and 15-crown-5. Examples of polyalkylene glycol includes polyethylene glycol and polypropylene glycol. Examples of onium salts includes benzyltriethylammonium chloride, methyltrioctylammonium chloride, tetra-nbutylammonium chloride, tetra-n-butylammonium bromide, tetranbutylphosphonium chloride, bis [tris(dimethylamino) phosphine] iminium chloride and tetratris [tris(dimethylamino) phosphinimino] phosphonium chloride.
The phase transfer catalyst is used in 1 to 10 mole percentage.
The phase transfer catalyst of the present invention can be easily recovered and reused.
On another embodiment, the step of de-hydrohalogenation is performed using a base in a non-aqueous, non-alcohol solvent therefor that is at least essentially miscible with the halopropane, wherein the reaction is performed at a temperature at which de-hydrohalogenation will occur and wherein de-hydrohalogenation is carried out with or without a phase transfer catalyst.
In another embodiment, the step of de-hydrohalogenation is performed thermally at a temperature of 35°C to 400°C.
In a particular embodiment, 1,1,1, 3-tetrachloropropene is de-hydrohalogenated using a base in presence of a phase transfer catalyst at a temperature of 15 °C to 45 °C to give a mixture of 1,1,3-trichloroprop-1-ene and 3,3,3-trichloroprop-1-1ene.
As used herein, the “fluorinating” refers to reacting with a fluorinating agent in hydrogen fluoride as a solvent.
Fluorinating agent is fluorine gas, optionally provided as fluorinating gaseous composition comprising fluorine and optionally one or more carrier gases (e.g. nitrogen or helium). Any carrier gases are suitably inert gases, suitably inert to fluorine and suitably also inert to any other starting materials, products, or reagents of the methods of the invention.
The fluorination reaction of the present invention is preferably carried out in a Hastelloy pressure reactor. The reactor is first passivated using a mixture of 8-12% of fluorine in nitrogen. The passivation of the reactor aids in fluorination reaction and it prevent corrosion of reactor and provides a safe process because sometimes explosion also possible with non-passivated metal surface with high flow rate.
The fluorinating agent is added at a flow rate of 40-110cc/ minute. The fluorination is carried out at a temperature selected in the range of -40 to -70oC.
The pressure used for fluorination is selected in the range of 0 to 0.5 kg/cm2.
In a particular embodiment, the electrophilic fluorinating gaseous composition comprises or consists essentially of 5 to 15 % fluorine and 85 to 95% nitrogen, most suitably 10% fluorine and 90% nitrogen.
Fluorinating gaseous composition is suitably provided to a reaction mixture as a constant flow.
The fluorination reaction is carried out in presence of hydrofluoric acid which is used as a solvent. Preferably anhydrous hydrofluoric acid is used as a solvent and 6 to 10 moles of anhydrous hydrofluoric acid are preferred. 0.4710 to 0.4750 moles of mixture of 1,1,3 trichloropropene and 3,3,3 trichloropropene are used. The mixture is fed at a flow rate of 3-7g/ hour.
In a particular embodiment, the fluorination is carried out using a gaseous composition comprising fluorine and nitrogen in hydrogen fluoride solvent.
In a particular embodiment, a mixture of 1,1,3-trichloroprop-1-ene and 3,3,3-trichloroprop-1-ene is fluorinated using a fluorinating gaseous composition comprises of 5 to 15 % fluorine and 85 to 95% nitrogen in hydrogen fluoride solvent, to give a mixture of 1,1,3-trichloro-1,2-difluoropropane and 1,1,1-trichloro-2,3-difluoropropane.
In an embodiment, the fluorination gives a mixture of 1,1,3-trichloro-1,2-difluoropropane and 1,1,1-trichloro-2,3-difluoropropane, having 1,1,3-trichloro-1,2-difluoropropane in an amount not less than 40% w/w of their total concentration.
In another embodiment, a mixture of 1,1,3-trichloro-1,2-difluoropropane and 1,1,1-trichloro-2,3-difluoropropane is separated by distillation.
In a particular embodiment, 1,1,3-trichloroprop-1-ene is fluorinated using a fluorinating gaseous composition comprises of 5 to 15 % fluorine and 85 to 95% nitrogen in hydrogen fluoride solvent, to give 1,1,3-trichloro-1,2-difluoropropane.
In a particular embodiment, 3,3,3-trichloroprop-1-1ene is fluorinated using a fluorinating gaseous composition comprises of 5 to 15 % fluorine and 85 to 95% nitrogen in hydrogen fluoride solvent, to give 1,1,1-trichloro-2,3-difluoropropane.
In another embodiment, mixture of 1,1,3-trichloro-1,2-difluoropropane and 1,1,1-trichloro-2,3-difluoropropane is used as such for preparation of 2,3,3,3-tetrafluoropropene (1234yf) and 1,1,1,3-etetrafluoropropene (1234ze).
The compound of Formula I is isolated by any method known in the art, for example, chemical separation, extraction, acid-base neutralization, distillation, evaporation, column chromatography and filtration or a mixture thereof.
The preferred means of isolation is quenching followed by distillation.
The distillation is performed at a pressure selected in the range of 5torr to 15torr and at a temperature selected in the range of 20oC to 30oC.
After completion of reaction, 80 to 90% of anhydrous hydrofluoric acid is recovered while the remaining is quenched using a base selected from a group consisting of sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate and aqueous ammonia.
The compounds of formula 1 as prepared by process of the present invention can be isolated or can be used as such without isolation for the preparation of hydrofluoro olefins.
The completion of the reaction may be monitored by any one of chromatographic techniques such as thin layer chromatography (TLC), high pressure liquid chromatography (HPLC), ultra-pressure liquid chromatography (UPLC), Gas chromatography (GC), liquid chromatography (LC) and alike.
Unless stated to the contrary, any of the words “comprising”, “comprises” and includes mean “including without limitation” and shall not be construed to limit any general statement that it follows to the specific or similar items or matters immediately following it.
Embodiments of the invention are not mutually exclusive, but may be implemented in various combinations. The described embodiments of the invention and the disclosed examples are given for the purpose of illustration rather than limitation of the invention as set forth in the appended claims.
The following example is given by way of illustration and therefore should not be construed to limit the scope of the present invention.

EXAMPLES
Example 1: Preparation of 1,1,1,3-tetrachloropropane
Carbon tetrachloride (8.452mol), triethylphosphate (0.631mol), iron (0.278mol), iron chloride (0.4g) was charged in hastalloy pressure reactor. Then the reaction mass was flushed with nitrogen gas at the rate of 2Kg/cm2 for two times and ethylene was flushed at the rate of 2Kg/cm2. After that reactor has been pressurized with 4Kg/cm2 of ethylene, the reaction mixture was gradually heated to a temperature of 90°C and subsequently raised to 120°C. Ethylene pressure was dropped when temperature reaches 120°C. The ethylene pressure was then maintained at the rate of 8Kg/cm2. After 12 hours reaction was stopped and unreacted ethylene was vented and recycled back to the reactor, the reaction mass was unloaded and taken for distillation. Distillation done under vacuum. Initially unreacted carbon tetrachloride was collected and recycled, then product cut 1185g was collected, the residue used for next reaction as catalyst (recycle the catalyst).
Purity: 98.5% by GC (Area %)
Yield: 77%

Example 2: Preparation of 1,1,1,3-tetrachloropropane
Carbon tetrachloride (8.452mol), tributylphosphate (0.631mol), iron (0.278mol), iron chloride (0.4g) was charged in hastalloy pressure reactor. Then the reaction mass was flushed with nitrogen gas at the rate of 2Kg/cm2 for two times and ethylene was flushed at the rate of 2Kg/cm2. After that reactor has been pressurized with 4Kg/cm2 of ethylene, the reaction mixture was gradually heated to a temperature of 90°C and subsequently raised to 120°C. Ethylene pressure was dropped when temperature reaches 120°C. The ethylene pressure was then maintained at the rate of 8Kg/cm2. After 12 hours reaction was stopped and unreacted ethylene was vented and recycled back to the reactor, the reaction mass was unloaded and taken for distillation. Distillation was done under vacuum. Initially unreacted carbon tetrachloride was collected and recycled, then product cut 1185g was collected, the residue used for next reaction as catalyst (recycle the catalyst).
Purity: 98.9% by GC (Area %)
Yield: 78%

Example 3: Preparation of 1,1,1,3-tetrachloropropane
Carbon tetrachloride (8.452mol), trimethylphosphate (0.631mol), iron (0.278mol), iron chloride (0.4g) was charged in hastalloy pressure reactor. Then the reaction mass was flushed with nitrogen gas at the rate of 2Kg/cm2 for two times and ethylene was flushed at the rate of 2Kg/cm2. After that rector has been pressurized with 4Kg/cm2 of ethylene, the reaction mixture was gradually heated to a temperature of 90°C and subsequently raised to 120°C. Ethylene pressure was dropped when temperature reaches 120°C. The ethylene pressure was then maintained at the rate of 8Kg/cm2. After 12 hours reaction was stopped and unreacted ethylene was vented and recycled back to the reactor, the reaction mass was unloaded and taken for distillation. Distillation done under vacuum. Initially unreacted carbon tetrachloride was collected and recycled, then product cut 1185g was collected, the residue used for next reaction as catalyst (recycle the catalyst).
Purity: 99% by GC (Area %)
Yield: 75%

Example 4: Preparation of trichloropropene
1,1,1,3-Tetrachloropropane (3.33mol) and methyltrioctylammonium chloride (0.0495mol) was charged into the glass reactor at 32°C and 1 atm pressure. An aqueous solution of sodium hydroxide (20%; 4mol) was added into the reaction mass drop-wise at 32 to 35 °C with agitation for 5 hours. After completion of addition, the reaction mixture was allowed to stir for 12 hours at 32°C. The reaction mass was unloaded and taken for distillation. Distillation done at reduced pressure. Initially low boiling impurities were separated and then 385grams of product was collected.
Purity: 98.4%
Yield: 80%

Example 5: Preparation of trichloropropene
1,1,1,3-Tetrachloropropane (3.33mol) and tetra-n-butylammonium bromide (0.05mol) was charged into the glass reactor at 32°C and 1 atm pressure. An aqueous solution of sodium hydroxide (20%; 4mol) was added into the reaction mass drop-wise at 32 to 35 °C with agitation for 5 hours. After completion of addition, the reaction mixture was allowed to stir for 12 hours at 32°C. The reaction mass was unloaded and taken for distillation. Distillation done at reduced pressure. Initially low boiling impurities were separated and then 385grams of product was collected.
Purity: 98.5%
Yield: 83%

Example 6: Preparation of trichloropropene
1,1,1,3-Tetrachloropropane (3.33mol) and tetranbutylphosphonium chloride (0.05mol) was charged into the glass reactor at 32°C and 1 atm pressure. An aqueous solution of sodium hydroxide (20%; 4mol) was added into the reaction mass drop-wise at 32 to 35 °C with agitation for 5 hours. After completion of addition, the reaction mixture was allowed to stir for 12 hours at 32°C. The reaction mass was unloaded and taken for distillation. Distillation done at reduced pressure. Initially low boiling impurities were separated and then 385grams of product was collected.
Purity: 98.6%
Yield: 82%

Example 7: Preparation of a mixture of trichlorodifluoropropane
Hastelloy pressure reactor was passivated using 10% F2/N2 mixture. The reactor was cooled to a temperature of -80°C and vaccumized. The pressure reactor was then charged with anhydrous hydrofluoric acid (6.5mol) at a temperature of -80°C to -40°C. The reactor was cooled to -60°C and 0.4722 moles of a mixture of 1,1,3 trichloropropene (formula 2a) and 3,3,3 trichloropropene (formula 2b) were fed through one dip tube with the flow of 7g/ hour and 20% F2/N2 mixture (0.6053mol) was purged through another dip tube as with the flow of 100cc/ minute at -60°C and 1atm pressure simultaneously. After completion of reaction, anhydrous hydrofluoric acid (100g) was recovered and 85 g crude product was unloaded with residual hydrofluoric acid. Then residual hydrofluoric acid was quenched using saturated potassium bicarbonate at 20°C and taken for boil off to get moisture free product (74g).
Purity (by GC): 95%
Yield: 70%

Example 8: Preparation of a mixture of trichlorodifluoropropane
Hastelloy pressure reactor was passivated using 10% F2/N2 mixture. The reactor was cooled to a temperature of -60°C and vaccumized. The pressure reactor was then charged with anhydrous hydrofluoric acid (6.5mol) at a temperature of -60°C to -40°C. The reactor was cooled to -40°C and 0.4722 moles of a mixture of 1,1,3 trichloropropene (formula 2a) and 3,3,3 trichloropropene (formula 2b) were fed through one dip tube with the flow of 7g/ hour and 20% F2/N2 mixture (0.6053mol) was purged through another dip tube as with the flow of 100cc/ minute at -60°C and 1atm pressure simultaneously. After completion of reaction, anhydrous hydrofluoric acid (100g) was recovered and 85 g crude product was unloaded with residual hydrofluoric acid. Then residual hydrofluoric acid was quenched using saturated potassium bicarbonate at 20°C and taken for boil off to get moisture free product.
Purity (by GC): 97%
Yield: 74%

Example 9: Preparation of a mixture of trichlorodifluoropropane
Hastelloy pressure reactor was passivated using 10% F2/N2 mixture. The reactor was cooled to a temperature of -80°C and vaccumized. The pressure reactor was then charged with anhydrous hydrofluoric acid (6.5mol) at a temperature of -80°C to -40°C. The reactor was cooled to -60°C and 0.4722 moles of a mixture of 1,1,3 trichloropropene (formula 2a) and 3,3,3 trichloropropene (formula 2b) were fed through one dip tube with the flow of 7g/ hour and 20% F2/N2 mixture (0.6053mol) was purged through another dip tube as with the flow of 100cc/ minute at -60°C and 1atm pressure simultaneously. After completion of reaction, anhydrous hydrofluoric acid (100g) was recovered and 85 g crude product was unloaded with residual hydrofluoric acid. Then residual hydrofluoric acid was quenched using saturated sodium bicarbonate at 20°C and taken for boil off to get moisture free product.
Purity (by GC): 96%
Yield: 73%

Comparative Example: Preparation of a mixture of trichlorodifluoropropane
Hastelloy pressure reactor was passivated using 10% F2/N2 mixture. The reactor was cooled to a temperature of -80°C and vaccumized. The reactor was cooled to -60°C and 0.4722 moles of a mixture of 1,1,3 trichloropropene (formula 2a) and 3,3,3 trichloropropene (formula 2b) were fed through one dip tube with the flow of 7g/ hour and 20% F2/N2 mixture (0.6053mol) was purged through another dip tube as with the flow of 100cc/minute at -60°C and 1atm pressure simultaneously. After completion of reaction, crude product was unloaded and was quenched using saturated potassium bicarbonate at 20°C and taken for boil off to get moisture free product.
Purity (by GC): 80%
Yield: 55%

We Claim:
1. A process for preparation of a compound of formula 1,

wherein X1 and X2 represents chlorine or fluorine; provided that X1 is not same as X2,
comprising the steps of:
a) reacting carbon tetrachloride with ethylene in presence of a metallic catalyst and organic legand to obtain a reaction mixture 1 comprising 1,1,1,3-tetrachloropropane;
b) de-hydrohalogenating the reaction mixture 1 to obtain a reaction mixture 2, comprising trichloropropenes;
c) fluorinating the reaction mixture 2 to obtain the compound of formula 1.

2. A process for preparation of a compound of formula 1,

wherein X1 and X2 represents chlorine or fluorine; provided that X1 is not same as X2,
comprising the steps of:
a) de-hydrohalogenating a reaction mixture 1 comprising 1,1,1,3-tetrachloropropane to obtain a reaction mixture 2 comprising trichloropropenes;
b) fluorinating the reaction mixture 2 to obtain the compound of formula 1.

3. A process for preparation of a compound of formula 1,

wherein X1 and X2 represents chlorine or fluorine; provided that X1 is not same as X2,
comprising the step of fluorinating a reaction mixture 2 of trichloropropenes to obtain the compounds of formula 1.

4. The process as claimed in claims 1-3, wherein the compound of formula 1 represents 1,1,3-trichloro-1,2-difluoropropane and 1,1,1-trichloro-2,3-difluoropropane.

5. The process as claimed in claims 1-3, wherein the “reaction mixture 2” comprises of 1,1,3-trichloroprop-1-ene and 3,3,3-trichloroprop-1-ene.

6. The process as claimed in claim 1, wherein the metallic catalyst is selected from a group consisting of cuprous chloride, cuprous bromide, cuprous cyanide, cuprous sulfate, ferrous chloride, ferric chloride, tris (2,2'-bipyridine) iron (II) hexafluorophosphate, iron powder; and the organic ligand is selected from a group consisting of amines, nitrites, amides, and phosphates.

7. The process as claimed in claims 1-2, wherein the de-hydrohalogenation reaction is carried out in presence of an organic base selected from alkali metal alkoxides or an inorganic base selected from alkali metal hydroxides and alkaline earth metal hydroxides or a mixture thereof.

8. The process as claimed in claims 1-2, wherein the de-hydrohalogenation reaction is carried out in presence of a phase transfer catalyst selected from crown ethers; cryptates; polyalkylene glycols or derivatives thereof; and onium salts.

9. The process as claimed in claims 1-3, wherein the fluorinating agent used is fluorine gas.

10. The process as claimed in claim 1, wherein the fluorination reaction is carried out in presence of hydrofluoric acid as a solvent.