# Patent

## Title
Stabilization of 1-chloro-3,3,3-trifluoropropene

## Abstract

The use of a C3 to C6 alkene compound including a sole double bond, for limiting or preventing, for example, the isomerization of trans-1-chloro-3,3,3-trifluoropropene to cis-1-chloro-3,3,3-trifluoropropene. Also, a composition including 1-chloro-3,3,3-trifluoropropene and a C3 to C6 alkene compound including a sole double bond, and also to various uses of this composition.

## Background
FIELD OF THE INVENTION
The present invention relates to compounds which make it possible to stabilize 1-chloro-3,3,3-trifluoroproprene and more specifically to limit or prevent isomerization of the trans form to the cis form. The invention also relates to the use of such stabilizers in heat-transfer applications.
TECHNICAL BACKGROUND
Trans-1-chloro-3,3,3-trifluoroproprene (HCFO-1233zdE) is a product with a low global warming potential (GWP). It has thermodynamic and thermophysical properties that are very favorable for use as a heat-transfer fluid in cooling, air-conditioning, electricity production (in particular by means of organic Rankine cycles) and high-temperature heat pump applications.
HCFO-1233zdE has an instability which manifests itself especially at relatively high temperature. This instability consists of an isomerization of a fraction of the initial feedstock resulting in the formation of cis-1-chloro-3,3,3-trifluoroproprene (HCFO-1233zdZ).
As it happens, HCFO-1233zdZ is a less volatile product than HCFO-1233zdE. The boiling point is about 40° C. for the Z isomer, and about 18.3° C. for the E isomer. This difference implies a change in the thermodynamic and thermophysical properties of the product in facilities, and a loss of performance level, when the isomerization occurs.
Document WO 2009/003165 describes the risks of degradation of hydrofluoroolefins and hydrochlorofluoroolefins, and also stabilizers for combating this degradation. These stabilizers comprise free radical scavenger compounds, acid scavenger compounds, oxygen scavenger compounds and polymerization inhibitors. Mention is in particular made of: 1,2-epoxybutane, glycidyl methyl ether, d-l-limonene oxide, 1,2-epoxymethylpropane, nitromethane, alpha-methylstyrene, isoprene, phenol, hydroquinones and hydrazine.
Document U.S. Pat. No. 7,795,480 describes a process for producing 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf). A phenomenon of polymerization of the compound is mentioned (but not an isomerization phenomenon). Proposed stabilizers are p-tap(4-tert-amylphenol), methoxyhydroquinone, 4-methoxyphenol, triethylamine, diisopropylamine, butylated hydroxyanisole and thymol.
Document U.S. Pat. No. 8,217,208 describes the phenomenon of isomerization of HFO-1233zdE under the effect of temperature, but it does not teach stabilizers which make it possible to limit this isomerization.
Document US 2012/0226081 describes the risks of degradation of hydrochloroolefins and of hydrochloroalkanes, and proposes a set of possible stabilizers: alpha-methylstyrene, alpha-pineneoxide, beta-pineneoxide, 1,2-epoxybutane, 1,2-hexadecene oxide and oxygen scavenger compounds such as diethylhydroxylamine, hydroquinone, methylethylketooxime and p-methoxyphenol.
Document US 2015/0034523 describes the risks of degradation of hydrochloroolefins and proposes two families of stabilizers, namely morpholines or trialkyl phosphates.
Virtually all of the stabilizers proposed in the prior art are solid products, or liquid products with a high boiling point. For example, the boiling point of alpha-methylstyrene is 165° C., the boiling point of limonene oxide is greater than 200° C., etc.
Isoprene, mentioned in document WO 2009/003165, is for its part a product that is unstable in itself, and that must generally be combined with a compound such as 4-tert-butylpyrocatechol in order to prevent it from being polymerized.
The characteristics described above make the stabilizers unsuitable for certain applications in which HCFO-1233zdE is liable to be used. This is in particular the case with applications using flooded evaporators (in particular with compressors without lubricating oil). In such applications, the prior art stabilizers, with a high boiling point, are ineffective since they concentrate in the evaporator and do not migrate with the heat-transfer fluid to the condenser.
There is therefore a need to provide stabilizers which make it possible to limit or prevent the isomerization of HCFO-1233zdE to HCFO-1233zdZ, in particular in vapor compression systems such as air-conditioning, refrigeration, heat-pump and organic Rankine cycle systems, and quite particularly systems comprising a flooded evaporator.
SUMMARY OF THE INVENTION
The invention relates firstly to the use of a C3 to C6 alkene compound comprising a sole double bond, for limiting or preventing the isomerization of trans-1-chloro-3,3,3-trifluoropropene to cis-1-chloro-3,3,3-trifluoropropene.
According to one embodiment, the alkene compound is a butene or a pentene.
According to one embodiment, the alkene compound has:

    
    
        a boiling point less than or equal to 100° C., preferably less than or equal to 75° C., and more particularly preferably less than or equal to 50° C.; and/or
        a solidification temperature less than or equal to 0° C., preferably less than or equal to −25° C., and more particularly preferably less than or equal to −50° C.
    
    


According to one embodiment, the alkene compound is 2-methylbut-2-ene.
According to one embodiment, the alkene compound is 3-methylbut-1-ene.
A subject of the invention is also a composition comprising 1-chloro-3,3,3-trifluoropropene and a C3 to C6 alkene compound comprising a sole double bond.
According to one embodiment, the alkene compound is a butene or a pentene.
According to one embodiment, the alkene compound has:

    
    
        a boiling point less than or equal to 100° C., preferably less than or equal to 75° C., and more particularly preferably less than or equal to 50° C.; and/or
        a solidification temperature less than or equal to 0° C., preferably less than or equal to −25° C., and more particularly preferably less than or equal to −50° C.
    
    


According to one embodiment, the alkene compound is 2-methylbut-2-ene.
According to one embodiment, the alkene compound is 3-methylbut-1-ene.
According to one embodiment, the compound comprises from 0.01% to 5%, preferably from 0.1% to 2% and more particularly from 0.2% to 1%, by weight, of alkene compound.
According to one embodiment, the 1-chloro-3,3,3-trifluoropropene is in trans form in a weight proportion greater than or equal to 90%, preferably greater than or equal to 95%, more particularly preferably greater than or equal to 98%, even more particularly preferably greater than or equal to 99%, and ideally greater than or equal to 99.5%, or even greater than 99.9%.
According to one embodiment, the composition also comprises one or more heat-transfer compounds other than 1-chloro-3,3,3-trifluoropropene and/or one or more additives chosen from stabilizers other than the alkene compound, lubricants, surfactants, tracers, fluorescent agents, odorous agents, solubilizing agents, and mixtures thereof.
A subject of the invention is also the use of the above composition as a heat-transfer fluid in a vapor compression system.
According to one embodiment, the vapor compression system is:

    
    
        an air-conditioning system; or
        a refrigeration system; or
        a freezing system; or
        a heat pump system.
    
    


According to one embodiment, the above use is a use as a heat-transfer fluid in a thermal engine.
According to one embodiment, the heat-transfer fluid is at a temperature greater than or equal to 100° C., preferably greater than or equal to 140° C., more particularly preferably greater than or equal to 180° C., for at least one fraction of the duration of its use.
According to one embodiment, the heat-transfer fluid is evaporated in a flooded evaporator.
A subject of the invention is also a heat-transfer facility comprising a circuit containing the above composition as a heat-transfer fluid.
According to one embodiment, the facility is chosen from mobile or stationary facilities for heating via a heat pump, for air-conditioning, for refrigeration, or for freezing and thermal engines.
According to one embodiment, the facility comprises a flooded evaporator.
A subject of the invention is also a process for heating or cooling a fluid or a body by means of a vapor compression system containing a heat-transfer fluid, said process comprising successively the evaporation of the heat-transfer fluid, the compression of the heat-transfer fluid, the condensation of the heat-transfer fluid and the expansion of the heat-transfer fluid, in which the heat-transfer fluid is the composition described above.
A subject of the invention is also a process for producing electricity by means of a thermal engine, said process comprising successively the evaporation of the heat-transfer fluid, the expansion of the heat-transfer fluid in a turbine which makes it possible to generate electricity, the condensation of the heat-transfer fluid and the compression of the heat-transfer fluid, in which the heat-transfer fluid is the composition described above.
The present invention makes it possible to overcome the drawbacks of the prior art. It provides more particularly stabilizers which make it possible to limit or prevent the isomerization of HCFO-1233zdE to HCFO-1233zdZ, in particular in vapor compression systems such as air-conditioning, refrigeration, heat pump and thermal engine systems, and quite particularly the systems comprising a flooded evaporator.


DESCRIPTION OF EMBODIMENTS OF THE INVENTION
The invention is now described in greater detail and in a nonlimiting manner in the description which follows.
Unless otherwise mentioned, throughout the application, the proportions of compounds indicated are given as weight percentages.
The invention is based on the discovery that C3 to C6 alkene compounds comprising a sole double bond make it possible to stabilize HCFO-1233zdE, i.e. to limit or prevent the isomerization thereof to HCFO-1233zdZ, in particular at high temperatures.
The stabilizing compounds of the invention are therefore propene, butenes, pentenes and hexenes. Butenes and pentenes are preferred. Pentenes are even more particularly preferred.
The stabilizing compounds of the invention may comprise a linear or branched chain and preferably a branched chain.
Preferably, they have a boiling point less than or equal to 100° C., more preferably less than or equal to 75° C., and more particularly preferably less than or equal to 50° C.
The term “boiling point” is intended to mean the boiling point at a pressure of 101.325 kPa, as determined according to standard NF EN 378-1 from April 2008.
Likewise preferably, they have a solidification temperature less than or equal to 0° C., preferably less than or equal to −25° C., and more particularly preferably less than or equal to −50° C.
The solidification temperature is determined according to Test No. 102: Melting point/Melting range (OECD guidelines for the testing of chemicals, Section 1, OECD publications, Paris, 1995, available at the web address http://dx.doi.orq/10.1787/9789264069534-fr).
Stabilizing compounds of the invention are in particular:

    
    
        but-1-ene;
        cis-but-2-ene;
        trans-but-2-ene;
        2-methylprop-1-ene;
        pent-1-ene;
        cis-pent-2-ene;
        trans-pent-2-ene;
        2-methylbut-1-ene;
        2-methylbut-2-ene; and
        3-methylbut-1-ene.
    
    


Among the preferred compounds are in particular 2-methylbut-2-ene, of formula (CH3)2C═CH—CH3 (boiling point of approximately 39° C.), and 3-methylbut-1-ene, of formula CH3—CH(CH3)—CH═CH2 (boiling point of approximately 25° C.).
Two or more than two of the above compounds may also be used in combination.
The stabilizing compounds according to the invention are thus advantageously used in combination with HCFO-1233zd, and more particularly with HCFO-1233zdE, in heat-transfer applications.
Thus, the invention provides a composition, in particular of use for heat-transfer applications, comprising at least HCFO-1233zd and a stabilizing compound described above.
The weight proportion of the stabilizing compounds above in the composition may in particular be: from 0.01% to 0.05%; or from 0.05% to 0.1%; or from 0.1% to 0.2%; or from 0.2% to 0.3%; or from 0.3% to 0.4%; or from 0.4% to 0.5%; or from 0.5% to 0.6%; or from 0.6% to 0.7%; or from 0.7% to 0.8%; or from 0.8% to 0.9%; or from 0.9% to 1%; or from 1% to 1.2%; or from 1.2% to 1.5%; or from 1.5% to 2%; or from 2% to 3%; or from 3% to 4%; or from 4% to 5%. 
The composition may comprise HCFO-1233zdE and optionally HCFO-1233zdZ. Advantageously, the proportion of HCFO-1233zdE, relative to the total HCFO-1233zd, is greater than or equal to 90%, or greater than or equal to 91%, or greater than or equal to 92%, or greater than or equal to 93%, or greater than or equal to 94%, or greater than or equal to 95%, or greater than or equal to 96%, or greater than or equal to 97%, or greater than or equal to 98%, or greater than or equal to 99%, or greater than or equal to 99.1%, or greater than or equal to 99.2%, or greater than or equal to 99.3%, or greater than or equal to 99.4%, or greater than or equal to 99.5%, or greater than or equal to 99.6%, or greater than or equal to 99.7%, or greater than or equal to 99.8%, or greater than or equal to 99.9%, or greater than or equal to 99.91%, or greater than or equal to 99.92%, or greater than or equal to 99.93%, or greater than or equal to 99.94%, or greater than or equal to 99.95%, or greater than or equal to 99.96%, or greater than or equal to 99.97%, or greater than or equal to 99.98%, or greater than or equal to 99.99%.
The presence of the stabilizing compound makes it possible to limit or prevent an increase in the proportion of HCFO-1233zdZ in the composition over time and/or in the event of the application of relatively high temperatures.
The composition of the invention may also comprise various additives. When it is a heat-transfer composition, the additives may in particular be chosen from lubricants, nanoparticles, stabilizers (other than the stabilizing compounds of the invention), surfactants, tracers, fluorescent agents, odorous agents and solubilizing agents.
The stabilizer(s), when it (they) is (are) present, preferably represent(s) at most 5% by weight in the heat-transfer composition. Among the stabilizers, mention may in particular be made of nitromethane, ascorbic acid, terephthalic acid, azoles such as tolutriazole or benzotriazole, phenolic compounds such as tocopherol, hydroquinone, t-butylhydroquinone, 2,6-di-tert-butyl-4-methylphenol, epoxides (alkyl optionally fluorinated or perfluorinated or alkenyl or aromatic) such as n-butyl glycidyl ether, hexanediol diglycidyl ether, allyl glycidyl ether, or butyl phenyl glycidyl ether, phosphites, phosphonates, thiols and lactones.
By way of lubricants, use may in particular be made of oils of mineral origin, silicone oils, paraffins of natural origin, naphthenes, synthetic paraffins, alkylbenzenes, poly-alpha-olefins, polyalkene glycols, polyol esters and/or polyvinyl ethers.
According to one advantageous embodiment of the invention, the composition of the invention is, however, free of lubricant.
By way of nanoparticles, use may in particular be made of carbon nanoparticles, metal (copper, aluminum) oxides, TiO2, Al2O3, MoS2, etc.
By way of tracers (capable of being detected), mention may be made of deuterated or non-deuterated hydrofluorocarbons, deuterated hydrocarbons, perfluorocarbons, fluoroethers, brominated compounds, iodinated compounds, alcohols, aldehydes, ketones, nitrous oxide and combinations thereof. The tracer is other than the heat-transfer compound(s) making up the heat-transfer fluid.
By way of solubilizing agents, mention may be made of hydrocarbons, dimethyl ether, polyoxyalkylene ethers, amides, ketones, nitriles, chlorocarbons, esters, lactones, aryl ethers, fluoroethers and 1,1,1-trifluoroalkanes. The solubilizing agent is other than the heat-transfer compound(s) making up the heat-transfer fluid.
By way of fluorescent agents, mention may be made of naphthalimides, perylenes, coumarins, anthracenes, phenanthracenes, xanthenes, thioxanthenes, naphthoxanthenes, fluoresceins and derivatives and combinations thereof.
By way of odorous agents, mention may be made of alkyl acrylates, allyl acrylates, acrylic acids, acrylesters, alkyl ethers, alkyl esters, alkynes, aldehydes, thiols, thioethers, disulfides, allylisothiocyanates, alkanoic acids, amines, norbornenes, norbornene derivatives, cyclohexene, heterocyclic aromatic compounds, ascaridol, o-methoxy(methyl)phenol and combinations thereof.
The composition according to the invention may also comprise at least one other heat-transfer compound, in addition to the HCFO-1233zd. Such other optional heat-transfer compound may in particular be a hydrocarbon, ether, hydrofluoroether, hydrofluorocarbon, hydrochlorofluorocarbon, hydrofluoroolefin, hydrochloroolefin or hydrochlorofluoroolefin compound.
By way of example, said other heat-transfer compound may be chosen from 1,1,1,4,4,4-hexafluorobut-2-ene (HFO-1336mmz, E or Z isomer), 3,3,4,4,4-pentafluorobut-1-ene (HFO-1345fz), 2,4,4,4-tetrafluorobut-1-ene (HFO-1354mfy), 1,1,1,3,3-pentafluoropropane (HFC-245fa), 2,3,3,3-tetrafluoropropene (HFO-1234yf), 1,3,3,3-tetrafluoropropene (HFO-1234ze), difluoromethane (HFC-32), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,2,2-tetrafluoroethane (HFC-134), 1,1-difluoroethane (HFC-152a), pentafluoroethane (HFC-125), 1,1,1,3,3-pentafluorobutane (HFC-365mfc), methoxynonafluorobutane (HFE7100), butane (HC-600), 2-methylbutane (HC-601a), pentane (HC-601), ethyl ether, methyl acetate and combinations thereof.
In the composition of the invention, the HCFO-1233zd may represent in particular from 1% to 5% of the composition; or from 5% to 10% of the composition; or from 10% to 15% of the composition; or from 15% to 20% of the composition; or from 20% to 25% of the composition; or from 25% to 30% of the composition; or from 30% to 35% of the composition; or from 35% to 40% of the composition; or from 40% to 45% of the composition; or from 45% to 50% of the composition; or from 50% to 55% of the composition; or from 55% to 60% of the composition; or from 60% to 65% of the composition; or from 65% to 70% of the composition; or from 70% to 75% of the composition; or from 75% to 80% of the composition; or from 80% to 85% of the composition; or from 85% to 90% of the composition; or from 90% to 95% of the composition; or from 95% to 99% of the composition; or from 99% to 99.5% of the composition; or from 99.5% to 99.9% of the composition; or more than 99.9% of the composition. The HCFO-1233zd content may also vary within several of the above ranges: for example, from 50% to 55% and from 55% to 60%, i.e. from 50% to 60%, etc.
The composition of the invention can be used in a heat transfer process.
The heat transfer process according to the invention is based on the use of a facility comprising a vapor compression system which contains the composition of the invention as heat-transfer fluid. The heat transfer process may be a process for heating or cooling a fluid or a body.
The composition of the invention may also be used in a process for producing mechanical working or electricity, in particular in accordance with a Rankine cycle.
For the heating and cooling applications, the vapor compression system comprises at least one evaporator, one compressor, one condenser and one expansion valve, and also lines for transporting heat-transfer fluid between these components. The evaporator and the condenser comprise a heat exchanger making it possible to exchange heat between the heat-transfer fluid and another fluid or body.
By way of compressor, use may in particular be made of a centrifugal compressor having one or more stages or of a centrifugal mini-compressor. Rotary compressors, spiral compressors, reciprocating compressors or screw compressors may also be used. The compressor may be driven by an electric motor or by a gas turbine (for example fed by the exhaust gases of a vehicle, for mobile applications) or by gearing.
The vapor compression system then operates according to a conventional vapor compression cycle. The cycle comprises the change of state of the heat-transfer fluid from a liquid phase (or liquid/vapor phase state) to a vapor phase at a relatively low pressure, then the compression of the fluid in the vapor phase up to a relatively high pressure, the change of state (condensation) of the heat-transfer fluid from the vapor phase to the liquid phase at a relatively high pressure, and the reduction of the pressure so as to recommence the cycle.
The facility may also optionally comprise at least one circuit of heat-transfer fluid used to transmit the heat (with or without change of state) between the heat-transfer fluid circuit and the fluid or body to be heated or cooled.
The facility may also optionally comprise two (or more) vapor compression systems, containing identical or distinct heat-transfer fluids. For example, the vapor compression systems may be coupled to one another.
The cooling processes and facilities according to the invention comprise processes and facilities for air-conditioning (with mobile facilities, for example in vehicles, or stationary facilities), for refrigeration (with mobile facilities for example in containers, or stationary facilities) and for freezing or for cryogenics.
The heating facilities according to the invention comprise heat pumps.
For the applications for producing mechanical working or electricity, the facility is a thermal engine, which comprises at least one evaporator, one turbine, one condenser and one pump, and also lines for transporting heat-transfer fluid between these components. The facility can then operate according to a Rankine cycle.
It is possible to use any type of heat exchanger for the implementation of the heat-transfer fluids according to the invention, and in particular concurrent heat exchangers, or, preferably, countercurrent heat exchangers.
In particular, the evaporator used in the context of the invention may be a superheating evaporator or a flooded evaporator. In a superheating evaporator, all of the heat-transfer fluid is evaporated at the evaporator outlet, and the vapor phase is superheated.
In a flooded evaporator, the heat-transfer fluid in liquid form does not completely evaporate. A flooded evaporator comprises a liquid phase/vapor phase separator.
The invention is particularly of use when such an evaporator is used. This is because the prior art stabilizers with a high boiling point are ineffective when such an evaporator is used, since they concentrate in the evaporator and do not migrate with the heat-transfer fluid to the condenser.
The invention is also particularly of use when a high temperature exists at at least one point of the fluid circuit, and more particularly a temperature greater than or equal to 100° C., or greater than or equal to 110° C., or greater than or equal to 120° C., or greater than or equal to 130° C., or greater than or equal to 140° C., or greater than or equal to 150° C., or greater than or equal to 160° C., or greater than or equal to 170° C., or greater than or equal to 180° C., or greater than or equal to 190° C., or greater than or equal to 200° C. This is because it is under these conditions that HCFO-1233zdE is most likely to be converted into HCFO-1233zdZ.
In particular, in air-conditioning equipment, the general operating temperature is less than 100° C.; however, hot points at the compressor outlet may reach temperatures greater than 100° C., affecting the heat-transfer fluid over the course of a small proportion of its complete circulation time (for example less than 1%).
In heat pumps, the condensation temperature may reach approximately 140° C. In this case, the heat-transfer fluid may be at a temperature of approximately 140° C. over the course of a large proportion of its complete circulation time (for example approximately 50%). Furthermore, hot points between 150 and 200° C. may also be noted at the compressor outlet. The impact of a long residence time at temperatures greater than 100° C. and the existence of points at temperatures which may be in the region of 200° C. therefore require a stabilizer.
Likewise preferably, in the facility according to the invention, the temperature of the composition used as heat-transfer fluid remains greater than the solidification temperature of the stabilizing compound, in order to prevent any deposit of solid material in the circuit.
The composition according to the invention may also be of use as a blowing agent, a propellant (for example for an aerosol), a cleaning agent or solvent, or a dielectric gas, in addition to its use as a heat-transfer fluid.
As a propellant, the composition according to the invention may be used alone or in combination with known propellants. The propellant comprises, preferably consists of, a composition according to the invention. The active substance that must be propelled can be mixed with the propellant and inert compounds, solvents or other additives, so as to form a composition to be propelled. Preferably, the composition to be propelled is an aerosol.
As a blowing agent, the composition according to the invention may be included in a blowing composition, which preferably comprises one or more other compounds capable of reacting and of forming a foam or cellular structure under appropriate conditions, as is known to those skilled in the art.
In particular, the invention provides a process for preparing an expanded thermoplastic product comprising, first, the preparation of a polymeric blowing composition. Typically, the polymeric blowing composition is prepared by plasticizing a polymer resin and by mixing in the compounds of a blowing agent composition at an initial pressure. The plasticizing of the polymer resin can be carried out under the effect of heat, by heating the polymer resin in order to soften it sufficiently to mix in a blowing agent composition. Generally, the plasticizing temperature is close to the glass transition temperature or to the melting point for the crystalline polymers.
Other uses of the composition according to the invention comprise uses as a solvent, cleaning agent or the like. Mention may, for example, be made of vapor degreasing, precision cleaning, the cleaning of electronic circuits, dry cleaning, abrasive cleaning, solvents for the deposition of lubricants and release agents, and other solvent or surface treatments.
EXAMPLES
The following examples illustrate the invention without limiting it.
Example 1 (Comparative)—Instability of HCFO-1233zdE in the Absence of Stabilizer
The tests for thermal stability of HCFO-1233zdE are carried out according to the standard ASHRAE 97-2007 entitled “Sealed glass tube method to test the chemical stability of materials for use within refrigerant systems”. 
The compositions are determined by gas chromatography on a CP-sil8-CB column.
A first series of tests is carried out at 150° C. for times of between 10 minutes and 14 days. The results show a slight formation of the HFO-1233zdZ isomer, up to a content of 0.14% being reached at 14 days.
A second series of tests is carried out at 200° C. for a time of 24 hours. The results show a slight formation of the HCFO-1233zdZ isomer up to a content of approximately 1% being reached.
Finally, a third series of tests is also carried out at 250° C. for a time of 24 hours. The results show a formation of the HCFO-1233zdZ isomer of between 6% and 9%.
Example 2 (Invention)—Stabilization of HCFO-1233zdE
Thermal stability tests similar to those of example 1 are carried out, while adding 0.5% of stabilizer to the HCFO-1233zdE (weight content relative to the sum of the stabilizer and of the HCFO-1233zdE). The stabilizers tested are 2-methylbut-2-ene (2m2b) and 3-methylbut-1-ene (3mlb).
A first series of tests is carried out at 150° C. for a time of 14 days. The tests with 3m1 b show a formation of the HCFO-1233zdZ isomer of about 0.08% at the end of the period. In the tests with 2m2b, no HFO-1233zd-Z formation is measured.
A second series of tests is carried out at 200° C. for a time of 24 hours. The tests with 3m1b show a slight formation of the HFO-1233zdZ isomer of about 0.3%, and those with 2m2b show an HCFO-1233zdZ formation of about 0.07% at the end of this period.
The following table summarizes the stabilization effect observed:















HCFO-1233zdE
HCFO-1233zdE +
HCFO-1233zdE +



alone
3m1b
2m2b



















14 days at
0.14% of
0.08% of
HCFO-1233zdZ


150° C.
HCFO-1233zdZ
HCFO-1233zdZ
undetectable


24 hours at
1% of
0.3% of
0.07% of


200° C.
HCFO-1233zdZ
HCFO-1233zdZ
HCFO-1233zdZ

## Claims

1. A method of limiting or preventing the isomerization of trans-1-chloro-3,3,3-trifluoropropene to cis-1-chloro-3,3,3-trifluoropropene, comprising adding a C3 to C6 alkene compound selected from the group consisting of but-1-ene, cis-but-2-ene, trans-but-2-ene, 2-methylprop-1-ene, pent-1-ene, cis-pent-2-ene, trans-pent-2-ene, 2-methylbut-1-ene, 2-methylbut-2-ene, and 3-methylbut-1-ene to 1-chloro-3,3,3-trifluoropropene.

2. The method as claimed in claim 1, wherein the alkene compound has:
a boiling point less than or equal to 100° C.; and/or
a solidification temperature less than or equal to 0° C.

3. The method as claimed in claim 1, wherein the alkene compound is 2-methylbut-2-ene.

4. The method as claimed in claim 1, wherein the alkene compound is 3-methylbut-1-ene.

5. A composition comprising 1-chloro-3,3,3-trifluoropropene and a C3 to C6 alkene compound selected from the group consisting of but-1-ene, cis-but-2-ene, trans-but-2-ene, 2-methylprop-1-ene, pent-1-ene, cis-pent-2-ene, trans-pent-2-ene, 2-methylbut-1-ene, 2-methylbut-2-ene, and 3-methylbut-1-ene.

6. The composition as claimed in claim 5, wherein the alkene compound has:
a boiling point less than or equal to 100° C.; and/or
a solidification temperature less than or equal to 0° C.

7. The composition as claimed in claim 5, wherein the alkene compound is 2-methylbut-2-ene.

8. The composition as claimed in claim 5, wherein the alkene compound is 3-methylbut-1-ene.

9. The composition as claimed in claim 5, comprising from 0.01% to 5% of alkene compound.

10. The composition as claimed in claim 5, wherein the 1-chloro-3,3,3-trifluoropropene is in trans form in a weight proportion greater than or equal to 90%.

11. The composition as claimed in claim 5, also comprising one or more heat-transfer compounds other than 1-chloro-3,3,3-trifluoropropene and/or one or more additives chosen from stabilizers other than the alkene compound, lubricants, surfactants, tracers, fluorescent agents, odorous agents, solubilizing agents, and mixtures thereof.

12. A vapor compression system comprising a composition as claimed in claim 5.

13. The vapor compression system as claimed in claim 12, wherein the vapor compression system is:
an air-conditioning system; or
a refrigeration system; or
a freezing system; or
a heat pump system.

14. A thermal engine comprising a composition as claimed in claim 5.

15. The vapor compression system as claimed in claim 12, wherein the heat-transfer fluid is at a temperature greater than or equal to 100° C. for at least one fraction of the duration of its use.

16. The vapor compression system as claimed in claim 12, wherein the heat-transfer fluid is evaporated in a flooded evaporator.

17. A heat transfer facility comprising a circuit containing a composition as claimed in claim 5 as a heat-transfer fluid.

18. The facility as claimed in claim 17, chosen from mobile or stationary facilities for heating via a heat pump, for air-conditioning, for refrigeration or for freezing and thermal engines.

19. The facility as claimed in claim 17, comprising a flooded evaporator.

20. A process for heating or cooling a fluid or a body by means of a vapor compression system containing a heat-transfer fluid, said process comprising successively the evaporation of the heat-transfer fluid, the compression of the heat-transfer fluid, the condensation of the heat-transfer fluid and the expansion of the heat-transfer fluid, wherein the heat-transfer fluid is a composition as claimed in claim 5.

21. A process for producing electricity by means of a thermal engine, said process comprising successively the evaporation of the heat-transfer fluid, the expansion of the heat-transfer fluid in a turbine which makes it possible to generate electricity, the condensation of the heat-transfer fluid and the compression of the heat-transfer fluid, wherein the heat-transfer fluid is a composition as claimed in claim 5.