WO2019220463A1

WO2019220463A1 - Preparation of 2,3,3,3-tetrafluoropropene, intermediate and composition thereof

Info

Publication number: WO2019220463A1
Application number: PCT/IN2019/050394
Authority: WO
Inventors: Sarathy IYENGAR; Maheshwaran CHELLAIAH; Thirupathi ARUMUGAM; Vignesh Loganathan; Ramudu Dilli Babu GOTTUMUKALA; Jasmin Glory KIRUBA; Nathan Rajamani; Anurag Jain
Original assignee: Srf Limited
Priority date: 2018-05-18
Filing date: 2019-05-16
Publication date: 2019-11-21

Abstract

The present invention provides a process for preparation of 2,3,3,3-tetrafluoropropene, intermediate and composition thereof. Fluoro olefins play an important role as refrigerants. In recent years a fluoro olefin viz. 2,3,3,3-tetrafluoropropene (HFO-1234yf) has attracted attention as a new refrigerant to replace another fluorinated refrigerants.

Description

PREPARATION OF 2,3,3,3-TETRAFLUOROPROPENE,

INTERMEDIATE AND COMPOSITION THEREOF

FIELD OF THE INVENTION

The present invention relates to a process for preparation of 2, 3,3,3- tetrafluoropropene and composition thereof.

BACKGROUND OF THE INVENTION

Fluoro olefins play an important role as refrigerants. In recent years a fluoro olefin viz. 2,3,3,3-tetrafluoropropene (HFO-l234yf) has attracted attention as a new refrigerant to replace another fluorinated refrigerants.

U.S. Patent No. 2,931,840 describes a process for preparation of HFO-l234yf by heating and decomposing a mixture of methyl chloride and chlorodifluoromethane or tetrafluoroethylene at a temperature from 700 to 950°C by a common heating means such as an electric heater in a reactor.

The said patent has followed free radical mechanism, therefore, the said process results in low yield due to formation of several by-products.

There are several other patents available in literature which avoid the free radical mechanism process and most of references utilize l, l,l,2,3-pentafluoropropane (245eb) as a key intermediate for synthesizing HFO-l234yf.

U.S. Patent No. 6,548,719 discloses a process for producing fluoro olefins by dehydrofluorinating a hydrofluorocarbon in the presence of a phase transfer catalyst without using any solvent or diluent.

U.S. Patent No. 7,560,602 discloses a process for producing 2, 3,3,3- tetrafluoropropene by catalytic dehydrofluorination of 1 , 1 , 1 ,2,3 -pentafluoropropane (245eb) in the presence of alumina and chromium oxide catalysts.

U.S. Patent No. 8710282 discloses a process for producing 2, 3,3,3- tetrafluoropropene by dehydrofluorination of l, l, l,2,3-pentafluoropropane (245eb) in the presence of potassium hydroxide.

Fluorocarbon based fluids have found widespread use in many commercial and industrial applications. For example, fluorocarbon based fluids are frequently used as a working fluid in systems such as air conditioning, heat pump and refrigeration applications.

Certain fluorocarbons have been a preferred component in many heat exchange fluids, such as refrigerants, for many years in many applications. For, example, fluoroalkanes, such as chlorofluorome thane and chlorofluoroe thane derivatives, have gained widespread use as refrigerants in applications including air conditioning and heat pump applications owing to their unique combination of chemical and physical properties. Many of the refrigerants commonly utilized in vapor compression systems are either single components fluids or azeotropic mixtures. Flammability is another important property for many applications. That is, it is considered either important or essential in many applications, including particularly in heat transfer applications, to use compositions, which are non-flammable. Thus, it is frequently beneficial to use such compositions compounds, which are nonflammable. As used herein, the term "nonflammable" refers to compounds or compositions, which are determined to be nonflammable as determined in accordance with ASTM standard E-681 , dated 2002, which is incorporated herein by reference. Unfortunately, many hydrofluorocarbons(HFCs), which might otherwise be desirable for used in refrigerant compositions are not nonflammable.

Bromofluoromethane and bromochlorofluoromethane derivatives, particularly bromotrifluoromethane (Halon 1301) and bromochlorodifluoromethane (Halon 1211) have gained widespread use as fire extinguishing agents in enclosed areas such as airplane cabins and computer rooms. However, the use of various halons is being

phased out due to their high ozone depletion. Moreover, as halons are frequently used in areas where humans are present, suitable replacements must also be safe to humans at concentrations necessary to suppress or extinguish fire.

Applicants have thus come to appreciate a need for compositions, and particularly heat transfer compositions, fire extinguishing/suppression compositions, blowing agents, solvent compositions, and compatabilizing agents, that are potentially useful in numerous applications, including vapor compression heating and cooling systems and methods, while avoiding one or more of the disadvantages noted above.

Inventors of the present invention has discovered a novel intermediate namely“2- bromo-l, l,l,2-tetrafluoropropane” for synthesizing 2,3,3,3-tetrafluoropropene. The said novel intermediate can also be used as a refrigerant.

Inventors of the present invention has also discovered a composition of 2,3,3,3- tetrafluoropropene with the novel intermediate i.e., “2-bromo- 1 , 1 , 1 ,2- tetrafluoropropane” .

OBJECT OF THE INVENTION

The object of the present invention is to provide a process for preparation of 2,3,3,3- tetrafluoropropene, intermediate and composition thereof. SUMMARY OF THE INVENTION

A first aspect of the present invention provides a process for preparation of 2,3,3,3- tetrafluoropropene comprising the step of de-hydrobrominating 2-bromo- 1 , 1 , 1 ,2- tetrafluoropropane to 2,3,3,3-tetrafluoropropene.

A second aspect of the present invention provides a process for preparation of 2,3,3,3-tetrafluoropropene comprising the steps of:

i) fluorinating 2-bromo-3,3,3-trifluoropropene to obtain 2-bromo- 1,1, 1,2- tetrafluoropropane; and

ii) de-hydrobrominating 2-bromo-l,l,l,2-tetrafluoropropane to obtain 2, 3,3,3- tetrafluoropropene.

A third aspect of the present invention provides a novel intermediate namely 2-bromo- 1,1,1 ,2-tetrafluoropropane.

A fourth aspect of the present invention provides a process for preparation of

2-bromo- 1 , 1 , 1 ,2-tetrafluoropropane comprising the step of fluorinating 2-bromo-

3.3.3-trifluoropropene to obtain 2-bromo- l,l,l,2-tetrafluoropropane.

A fifth aspect of the present invention provides a composition consisting of about 1 to about 60 wt. % 2-bromo- 1,1, 1 ,2-tetrafluoropropane and about 40 to about 99 wt. % of 2,3,3,3-tetrafluoropropene.

DETAILED DESCRIPTION

The term“about” as used herein indicates 10% deviation in both sides from the specified parameter.

A second aspect of the present invention provides a process for preparation of

2.3.3.3-tetrafluoropropene comprising the steps of:

ii) de-hydrobrominating 2-bromo- l,l,l,2-tetrafluoropropane to obtain 2,3,3,3- tetrafluoropropene.

A third aspect of the present invention provides a novel intermediate namely 2- bromo- 1, 1,1, 2-tetrafluoropropane .

A fourth aspect of the present invention provides a process for preparation of 2- bromo- 1, 1,1 ,2-tetrafluoropropane comprising the step of fluorinating 2-bromo-3,3,3- trifluoropropene to obtain 2-bromo- 1,1,1 ,2-tetrafluoropropane.

As disclosed herein, the step of fluorination is carried out using hydrogen fluoride optionally in the presence of a catalyst.

The fluorination is carried out either in gas or liquid phase.

The fluorination is carried out at a pressure of about 5 Kg/cm² to about 20Kg/cm² The catalyst used for fluorination is based on a metal including a transition metal or an oxide or halide or oxyhalide derivative of such a metal. Preferably, antimony halide is used as a catalyst for fluorination.

The antimony halide may be selected from a group consisting of antimony pentachloride, antimony chlorofluoride, or the like.

The fluorination is carried out at a temperature range of 40°C to l00°C, preferably at a temperature range of 70°C and 90°C for 1 to 50 hours.

The unreacted hydrogen fluoride was recycled back to the reactor.

The step of de-hydrobromination is carried out either using an alkali metal hydroxide or using hydrogen fluoride in presence of a catalyst.

The alkali metal hydroxide used for de-hydrobromination is selected from potassium hydroxide, sodium hydroxide, lithium hydroxide, or the like.

In an embodiment of the present invention the step of de-hydrobromination is carried out using alkali metal hydroxide in presence of a phase transfer catalyst.

The phase transfer catalyst is selected from a group consisting of Trioctylmonomethylammonium chloride, benzyltriethylammonium chloride, methyltrioctylammonium chloride, tetra-n-butylammonium chloride, tetra-n- butylammonium bromide, tetra-n-butylphosphonium chloride, bis[tris(dimethylamino)phosphine]iminium chloride and

tetratris[tris(dimethylamino)phosphinimino]phosphonium chloride, polyethylene glycol, crown ethers or the like.

The reaction of 2-bromo- 1 , 1 , 1 ,2-tetrafluoropropane with alkali metal hydroxide is carried out at a temperature in the range of 30°C to l20°C and at a pressure in the range of 0-30Kg/cm² for few minutes to several hours till the reaction completion.

In one embodiment, the reaction is carried out at a temperature in the range of 50°C to 90°C for 12 hours to 24 hours.

After completion of the reaction, the reaction mixture is cooled at a suitable temperature in the range of -5°C to lO°C and gas phase is collected from reactor to super cooled vessel(-78°C). The outlet crude gas may further be purified to get a pure

2,3,3,3-tetrafluoropropene having purity at least 95% or atleast 99% or atleast 99.5%. The catalyst used for de-hydrobromination is selected from zirconium catalyst, chromium containing catalyst, or the like.

After completion of the reaction, 2-bromo- l, l,l,2-tetrafluoropropane may be isolated by using any suitable technique known in the art such as layer separation, extraction, distillation and alike or combination thereof.

The present invention provides a novel intermediate namely 2-bromo- 1,1, 1,2- tetrafluoropropane .

In one embodiment, 2-bromo- 1 , 1 , 1 ,2-tetrafluoropropane characterized by purity greater than 98% and yield not less than 80%.

The reaction may be conducted in a suitable reaction vessel or reactor. Preferably the vessel is comprised of materials which are resistant to corrosion as Hastelloy, Inconel, Monel and/or fluoropolymers linings. The vessel may contain catalyst, for example a fixed or fluid catalyst bed, packed with a suitable catalyst, with suitable means to heat the reaction mixture to the desired reaction temperature.

2-Bromo-3,3,3-trifluoropropene either can be obtained commercially or can be prepared by any methods known in the art.

In one embodiment, 2-bromo-3,3,3-trifluoropropene can be prepared by the method; wherein ethene and tetrachloromethane are reacted to give 1, 1, 1,3- tetrachloropropane followed by the reaction with chromia-alumina-zinc in the presence of hydrogen fluoride to give 3,3,3-trifluoropropene. Finally, 3,3,3- trifluoropropene is brominated to give 2,3-dibromo-l,l, l-trifluoropropane which upon de-hydrobromination gives 2-bromo-3,3,3-trifluoropropene.

The crude gaseous mixture may further be purified with any type of distillation or with any known techniques based on adsorption or absorption to get a pure 2, 3,3,3- tetrafluoropropene .

The completion of the reaction can 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), gas chromatography-mass spectroscopy (GC-MS) and the like.

In fifth aspect, the present invention provides a composition consisting of about 1 to about 60 wt. % 2-bromo- 1,1,1 ,2-tetrafluoropropane and about 40 to about 99 wt. % of 2,3,3,3-tetrafluoropropene.

In one embodiment of this aspect, the present invention provides a refrigerant composition comprising about 1 to about 60 wt. % 2-bromo- 1 , 1 , 1 ,2- tetrafluoropropane and about 40 to about 99 wt. % of 2,3,3,3-tetrafluoropropene.

In another embodiment of this aspect, the present invention provides a method of recharging a refrigeration system that contains a refrigerant to be replaced and a lubricant comprising the steps of: (a) removing the refrigerant to be replaced from the refrigeration system while retaining a substantial portion of the lubricant in said system; and (b) introducing into the refrigeration system a refrigerant of a composition consisting of about 1 to about 60 wt. % 2-bromo- 1,1, 1,2- tetrafluoropropane and about 40 to about 99 wt. % of 2,3,3,3-tetrafluoropropene.

In another embodiment of this aspect, the present invention provides a blowing agent composition comprising about 1 to about 60 wt. % 2-bromo- 1 , 1 , 1 ,2- tetrafluoropropane and about 40 to about 99 wt. % of 2,3,3,3-tetrafluoropropene.

In another embodiment of this aspect, the blowing agent is mixed with polyol. In another embodiment of this aspect, the present invention provides a closed cell foam prepared by using a blowing agent composition comprising about 1 to about 60 wt. % 2-bromo- 1 , 1 , 1 ,2-tetrafluoropropane and about 40 to about 99 wt. % of 2,3,3,3- tetrafluoropropene.

In another embodiment of this aspect, the closed cell foam comprises polyurethane, polyisocyanurate, polystyrene, polyethylene, and mixtures thereof.

It is convenient in many applications to provide the components for polyurethane or polyisocyanurate foams in pre -blended formulations. Most typically, the foam formulation is pre -blended into two components. The isocyanate and optionally certain surfactants and blowing agents comprise the first component, commonly referred to as the "A" component. The polyol or polyol mixture, surfactant, catalysts, blowing agents, flame retardant, and other isocyanate reactive components comprise the second component, commonly referred to as the "B" component. Accordingly, polyurethane or polyisocyanurate foams are readily prepared by bringing together the A and B side components either by hand mix for small preparations and, preferably, machine mix techniques to form blocks, slabs, laminates, pour-in-place panels and other items, spray applied foams, froths, and the like. Optionally, other ingredients such as fire retardants, colorants, auxiliary blowing agents, and even other polyols can be added as a third stream to the mix head or reaction site. Most preferably, however, they are all incorporated into one B -component as described above.

It is also possible to produce thermoplastic foams using the compositions of the invention. For example, conventional polystyrene and polyethylene formulations

may be combined with the compositions in a conventional manner to produce rigid foams.

In another embodiment of this aspect, the present invention provides cleaning composition comprising about 1 to about 60 wt. % 2-bromo- 1 , 1 , 1 ,2- tetrafluoropropane and about 40 to about 99 wt. % of 2,3,3,3-tetrafluoropropene.

In another embodiment of this aspect, the present invention provides a flame suppressant composition comprising about 1 to about 60 wt. % 2-bromo- 1,1, 1,2- tetrafluoropropane and about 40 to about 99 wt. % of 2,3,3,3-tetrafluoropropene. The present invention further provides methods of suppressing a flame, said methods comprising contacting a flame with a fluid comprising a compound or composition of the present invention. Any suitable methods for contacting the flame with the present composition may be used. For example, a composition of the present invention may be sprayed, poured, and the like onto the flame, or at least a portion of the flame may be immersed in the composition. In light of the teachings herein, those of skill in the art will be readily able to adapt a variety of conventional apparatus and methods of flame suppression for use in the present invention.

In another embodiment of this aspect, the present invention provides an aerosol composition comprising a composition consisting of about 1 to about 60 wt. % 2- bromo-l, l,l,2-tetrafluoropropane and about 40 to about 99 wt. % of 2, 3,3,3- tetrafluoropropene.

The aerosol composition contains medicament or cosmetic component to be delivered.

Other uses of the present compositions include use as solvents, cleaning agents, and the like. Those of skill in the art will be readily able to adapt the present compositions for use in such applications without undue experimentation.

Other uses of the present azeotrope-like compositions include use as solvents, cleaning agents, and the like. Those of skill in the art will be readily able to adapt the present compositions for use in such applications without undue experimentation. It is against this and other backgrounds, which shall be filed in a detailed manner in complete specifications, in due course, the present invention is brought out and explained in following non-limiting examples.

EXAMPLES

Example 1: Process for preparing 1,1 ,1 ,3-tetrachloropropane

l300g of (8.452mol) Carbon tetrachloride, H5g of (0.63 lmol) Triethylphosphate, l5.5g of (0.278mol) Iron, 0.4g of Iron chloride were charged in a 2 Litre Hastalloy pressure reactor. The reaction mass was flushed with nitrogen gas at a pressure of 2Kg/cm² for two times and ethylene was flushed one time at a pressure of 2Kg/cm². After that reactor was pressurized with ethylene at a pressure of 4Kg/cm². Then heating and stirring was started, temperature was gradually increased and exothermicity was observed at 90°C. Temperature was raised to l20°C. Ethylene pressure was dropped; when temperature reached to l20°C, ethylene pressure maintained at a pressure of 8Kg/cm². After 12 hours reaction was stopped and unreacted ethylene was vented, the reaction mass was unloaded and was taken for distillation. Distillation was done under vacuum. Initially unreacted carbon tetrachloride was collected, then product cut H85g was collected, the catalyst was recycled back for next reaction.

Purity (By GC): 98%

Yield: 77%

Example 2: Process for preparing 3,3,3-trifluoropropene.

The inconnel Y type tubular reactor was charged with 400 to 500g of Chromia- Alumina-Zinc catalyst. The catalyst was first dried by heating under nitrogen atmosphere at 250°C for 24 hour. Next the pre-fluorination of the catalyst was begun by introducing HF along with nitrogen stream and the temperature was increased to 300°C for 16 hours. During the last 5 hours the nitrogen flow was gradually cut off. Finally, the temperature was reduced to 25 °C.

The starting material l,l,l,3-tetrachloropropane was charged at a rate of 60 ml per hour using dosing pump. On the other side hydrogenfluoride gas was passed at a rate of 2g per min. The reactor temperature was maintained 225 °C to 250°C. The gases exiting the reactor were scrubbed with potassium hydroxide solution to remove acid vapours and the gas was analyzed by GC-MS and GC. The major product was identified as 3,3,3-trifluoropropene.

Purity (By GC): 98%

Yield: 90%

Example 3: Process for preparing 2,3-dibromo-l ,1,1 -trifluoropropane

200g ( 1.25mol) bromine was charged in a three neck round bottom flask, the centre neck equipped with double condenser. Primary condenser was maintained at 0°C and the secondary condenser was maintained at -80°C, side necks were equipped with thermopocket and gas purging tube. Agitation and Cooling was started, at a temperature of 0-3°C. The l26g (1.31) 3,3,3-trifluoroprop-l-ene purging was started. After decolourisation of bromine, reaction was stopped. The product was analyzed using GC-MS and GC.

Purity by GC: 98%

Yield: 95%

Example 4: Process for preparing 2-bromo-3,3,3-trifluoropropene

60g (0.39Mol) of 26.5% Sodium hydroxide solution was charged in a three neck round bottom flask, the centre neck was equipped with reflux divider with condenser, side necks were equipped with thermopocket and addition funnel. Then 3g (0.00742Mol) of trioctylmethylammoniumchloride was added. The reaction mass was agitated and heated to 50°C. At 50°C , the 50g (0.l953Mol) of 2, 3-dibromo-l, 1, l-trifluoropropane addition was started. After completion of addition the temperature was raised to 70°C. The low boiling product refluxed at vapour temperature of 33-34°C in the reflux divider. The 27.5g (0.1571 Mol) 2-bromo-3, 3, 3-trifluoroprop-l-ene product was collected in the reflux divider. The collected product was analysed using GC-MS and GC.

Purity (By GC): 99.20%

Yield: 80.46% Example 5: Process for preparing 2-bromo- 1,1,1 ,2-tetrafluoropropane

A freshly prepared SbCl₅ (350g), anhydrous hydrogen fluoride (400g) and 2-bromo- 3,3,3-trifluoropropene (lOOg) were charged in a 2 lit Hastalloy reactor and slowly heated and maintained at 85 °C for 4 hours. After 4 hours the hot reaction mixture was slowly vented off into ice water. After completion of venting, the aqueous layer was separated. The bottom layer consisting of crude organic of about l08g with the area composition of 85% of 2-bromo-l,l,l,2-tetrafluoropropane and 13% of 2- bromo-3,3,3,-trifluoropropene by GC. The crude was further distilled to obtain pure 2-bromo- 1,1,1 ,2-tetrafluoropropane.

Purity(by GC):98%

Yield: 80%

Example 6: Process for preparing 2,3,3,3-tetrafluoropropene (HFO-1234yf)

2-bromo- 1,1,1 ,2-tetrafluoropropane (80g) was added to a mixture of aqueous sodium hydroxide (l25g; 45%) and polyethylene glycol (3ml) in a 450ml Hastelloy reactor equipped with a mechanical agitator and coupled with a thermowell. The reaction mixture was slowly heated to 85°C and maintained for 24 hours. After 24 hours, the reactor was cooled to lO°C. The gas phase was collected from the reactor to a super cooled vessel (-78°C). The output crude gas was analyzed by GC. The crude material was further distilled to get pure HFO-l234yf.

Purity (by GC): 99.7%

Yield: 85%

Example 7: Preparation of composition comprising 2-bromo-2, 3,3,3- tetrafluoropropane and 2,3,3,3-tetrafluoropropene.

An ASTM-E681 apparatus was used to measure the flammability of the mixtures of 2,3,3,3-tetrafluoropropene and 2-bromo- l,l,l,2-tetrafluoropropane. The procedure described in the ASHRAE-34 was used to judge the flammability of the mixtures at 60° C. and at 100° C. Accordingly it was found that at 60° C., the critical flammability ratio (CFR) of the mixture was 10 mol % 2-bromo- 1 , 1 , 1 ,2- tetrafluoropropane and 90 mol % 2,3,3,3-tetrafluoropropene. Similarly it was also found that at 100° C., the critical flammability ratio (CFR) of the mixture was 12 mol % 2-bromo- 1, 1,1, 2-tetrafluoropropane and 88 mol % 2,3,3,3-tetrafluoropropene.

Claims

WE CLAIM

1. A process for preparation of 2,3,3,3-tetrafluoropropene, comprising the step of de-hydrobrominating 2-bromo- 1 , 1 , 1 , 2-tetrafluoropropane to obtain 2,3,3,3- tetrafluoropropene.

2. A process for preparation of 2,3,3,3-tetrafluoropropene comprising the steps of: i) fluorinating 2-bromo-3,3,3-trifluoropropene to obtain 2-bromo- 1 , 1 , 1 ,2- tetrafluoropropane; and

ii) de-hydrobrominating 2-bromo- 1,1,1, 2-tetrafluoropropane to obtain 2,3,3,3-tetrafluoropropene.

3. A novel compound of formula 1,

2-bromo- 1, 1,1, 2-tetrafluoropropane (formula 1).

4. A process for preparation of 2-bromo- 1,1,1, 2-tetrafluoropropane, comprising the step of fluorinating 2-bromo-3,3,3-trifluoropropene to obtain 2-bromo- 1,1, 1,2- tetrafluoropropane.

5. The process as claimed in claim 1 & 2, wherein the step of de-hydrobromination is carried out using alkali metal hydroxide, preferably potassium hydroxide, sodium hydroxide or lithium hydroxide or using hydrogen fluoride with a catalyst, preferably zirconium or chromium containing catalyst.

6. The process as claimed in claim 1 & 2, wherein the step of de-hydrobromination is carried out using alkali metal hydroxide in presence of phase transfer catalyst, selected from a group consisting of trioctylmonomethylammonium chloride, benzyltriethylammonium chloride, me thy ltrioctyl ammonium chloride, tetra-n- butylammonium chloride, tetra-n-butylammonium bromide, tetra-n- butylphosphonium chloride, bis[tris(dimethylamino)phosphine]iminium chloride, tetratris[tris(dimethylamino)phosphinimino]phosphonium chloride, polyethylene glycol and crown ethers.

7. The process as claimed in claim 1 & 2, wherein de-hydrobromination is carried out at a temperature in the range of 30°C to l20°C and at a pressure in the range of 0-30Kg/cm².

8. The process as claimed in claim 2 & 4, wherein the step of fluorination is carried out using hydrogen fluoride.

9. The process as claimed in claim 2 & 4, wherein the fluorination is carried out at a pressure in the range of 5 Kg/cm² to 20Kg/cm² and at a temperature in the range of 40°C to l00°C.

10. The process as claimed in claim 2 & 4, wherein the unreacted hydrogen fluoride was recycled back to the reactor.

11. A composition consisting of 1 to 60 wt. % 2-bromo- 1,1,1 ,2-tetrafluoropropane and 40 to 99 wt. % of 2,3,3,3-tetrafluoropropene.

12. A method of recharging a refrigeration system that contains a refrigerant to be replaced and a lubricant comprising the steps of:

(a) removing the refrigerant to be replaced from the refrigeration system while retaining a substantial portion of the lubricant in said system; and

(b) introducing into the refrigeration system a refrigerant of a composition consisting of 1 to 60 wt. % 2-bromo- 1,1,1 ,2-tetrafluoropropane and 40 to 99 wt. % of 2,3,3,3-tetrafluoropropene.

13. The composition as claimed in claim 1, wherein the composition is used in blowing agents, closed cell foams, thermoplastic foams, cleaning compositions, flame suppressant compositions or aerosol compositions.

14. The composition as claimed in claim 1 , wherein at 60°C., the critical flammability ratio (CFR) of the composition is 10 mol % 2-bromo- l,l,l,2-tetrafluoropropane and 90 mol % 2,3,3,3-tetrafluoropropene.

15. The composition as claimed in claim 1, wherein at 100° C., the critical flammability ratio (CFR) of the composition is 12 mol % 2-bromo- 1,1, 1,2- tetrafluoropropane and 88 mol % 2,3,3,3-tetrafluoropropene.