Method for suppressing disproportionation reaction of working medium for refrigeration cycles, working medium for refrigeration cycles, and refrigeration cycle device

Abstract

Disclosed is a method for suppressing a disproportionation reaction of a working medium for refrigeration cycles, with which, in a refrigeration cycle where a working medium for refrigeration cycles containing a refrigerant component that undergoes a disproportionation reaction, is circulated, a carbene that is generated by a disproportionation reaction of the refrigerant component is captured by a carbene capturing agent that has a higher reactivity with the carbene than substances other than the carbene which are present in the refrigeration cycle, and the disproportionation reaction of the refrigerant component is suppressed.

Description

Method for inhibiting disproportionation reaction of working fluid for refrigeration cycle, working fluid for refrigeration cycle, and refrigeration cycle device

[0001] The present invention relates to a method for inhibiting a disproportionation reaction of a working fluid for a refrigeration cycle, which can effectively inhibit or mitigate the disproportionation reaction of a fluoroolefin (fluoroalkene) such as 1,1,2-trifluoroethylene, and to a working fluid for a refrigeration cycle using the same.

[0002] Recently, the use of fluoroolefins, particularly hydrofluoroolefins (HFOs), which have an ozone depletion potential (ODP) of zero and a smaller global warming potential (GWP), has been proposed as working fluids (refrigerants or heat transfer media) for refrigeration cycles. Typical HFOs include 1,1,2-trifluoroethylene (HFO1123) and difluoroethylene (HFO1132). HFOs are less stable than conventional HFCs (hydrofluorocarbons) and are therefore less likely to remain in the atmosphere.

[0003] However, it is also known that HFOs are prone to self-polymerization reactions known as disproportionation reactions (hereinafter referred to as disproportionation reactions) due to their low stability. Disproportionation reactions are likely to occur due to heat generated during use of the working fluid for a refrigeration cycle, and since the occurrence of a disproportionation reaction is accompanied by a large heat release, it is also known that disproportionation reactions can occur in a chain reaction. As a result, a large amount of soot is generated, which may reduce the reliability of the refrigeration cycle system or the compressors that constitute the system.

[0004] Therefore, for example, Patent Document 1 proposes the use of a radical scavenger as a component (disproportionation inhibitor) for suppressing the disproportionation reaction of 1,1,2-trifluoroethylene when 1,1,2-trifluoroethylene is used as a refrigerant component of a working fluid for a refrigeration cycle. Patent Document 1 lists as specific radical scavengers: [1] a compound having a C-X (X is Cl, Br, or I) bond, in which the C-X bond energy is equal to or less than the energy of other bonds in the molecule; [2] CX4 (X is Cl, Br, or I, and the four Xs are the same); and [3] Rf-X (Rf is a perfluoroalkyl group having 1 to 6 carbon atoms, and X is Cl, Br, or I).

[0005] Patent No. 6455506

[0006] However, further investigations by the present inventors have revealed that the use of a radical scavenger as described in Patent Document 1 may not be able to effectively suppress or mitigate the disproportionation reaction of fluoroolefins such as 1,1,2-trifluoroethylene.

[0007] The present invention has been made to solve the above problems, and an object of the present invention is to provide a novel method for effectively suppressing or mitigating the disproportionation reaction of fluoroolefins in a working fluid for a refrigeration cycle containing a fluoroolefin as a refrigerant component.

[0008] As a result of intensive investigations to solve the above-mentioned problems, the present inventors have independently found that, among the substances produced in the disproportionation reaction of fluoroolefins, carbenes, which have not received much attention until now, may be involved in the chain progression of the disproportionation reaction, and have thus completed the present invention.

[0009] In order to solve the above-mentioned problems, the method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to the present disclosure is configured to, in a refrigeration cycle in which a working fluid for a refrigeration cycle containing a refrigerant component that undergoes a disproportionation reaction circulates, capture the carbene produced by the disproportionation reaction of the refrigerant component using a carbene scavenger that is more reactive with the carbene than with substances other than the carbene present in the refrigeration cycle, thereby suppressing the disproportionation reaction of the refrigerant component.

[0010] According to the above-described configuration, carbene, which has been found to be involved in the progression of a chain reaction of disproportionation reactions of refrigerant components, is trapped by the carbene scavenger, thereby effectively suppressing an increase in carbene in the refrigeration cycle, thereby making it possible to suppress or alleviate the disproportionation reactions of refrigerant components.

[0011] In particular, it has been found that in the disproportionation reaction of a refrigerant component, carbenes are gradually generated and accumulated in the induction stage, immediately before the self-decomposition of the refrigerant component begins to proceed in a chain reaction. When the concentration of carbenes exceeds a predetermined upper limit, which is a critical condition, the chain reaction proceeds. According to the above configuration, the carbene scavenger is more reactive with carbenes than with substances other than carbene (e.g., radicals) present in the refrigeration cycle, and therefore can effectively capture carbenes that accumulate in the induction stage. As a result, it is possible to effectively prevent or suppress the concentration of carbene from exceeding the critical condition, thereby making it possible to suppress or alleviate the chain reaction of the disproportionation reaction of the refrigerant component.

[0012] The present disclosure also includes a method for capturing carbene present in a refrigeration cycle, wherein the composition for a refrigeration cycle contains a carbene scavenger that is more reactive with the carbene than substances other than the carbene present in the refrigeration cycle, and the carbene scavenger is reacted with the carbene present in the refrigeration cycle to capture the carbene present in the refrigeration cycle.

[0013] The present disclosure also includes a refrigeration cycle composition containing a carbene scavenger that is more reactive with the carbene than with substances other than the carbene, and a refrigeration cycle device containing the refrigeration cycle composition.

[0014] The above and other objects, features, and advantages of the present invention will become apparent from the following detailed description of preferred embodiments, which proceeds with reference to the accompanying drawings.

[0015] The present invention, with the above-mentioned configuration, has an effect of providing a new method for effectively suppressing or mitigating the disproportionation reaction of a fluoroolefin in a working fluid for a refrigeration cycle containing a fluoroolefin as a refrigerant component.

[0016] 4A and 4B are schematic block diagrams showing an example of a refrigeration cycle system to which a refrigeration cycle according to an embodiment of the present disclosure is applied.

[0017] The method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to the present disclosure is configured to, in a refrigeration cycle in which a working fluid for a refrigeration cycle containing a refrigerant component that undergoes a disproportionation reaction is circulated, capture the carbene produced by the disproportionation reaction of the refrigerant component using a carbene scavenger that is more reactive with the carbene than with substances other than the carbene present in the refrigeration cycle, thereby suppressing the disproportionation reaction of the refrigerant component.

[0018] According to the above-described configuration, carbene, which has been found to be involved in the progression of a chain reaction of disproportionation reactions of refrigerant components, is trapped by the carbene scavenger, thereby effectively suppressing an increase in carbene in the refrigeration cycle, thereby making it possible to suppress or alleviate the disproportionation reactions of refrigerant components.

[0019] In particular, it has been found that in the disproportionation reaction of a refrigerant component, carbenes are gradually generated and accumulated in the induction stage, immediately before the self-decomposition of the refrigerant component begins to proceed in a chain reaction. When the concentration of carbenes exceeds a predetermined upper limit, which is a critical condition, the chain reaction proceeds. According to the above configuration, the carbene scavenger is more reactive with carbenes than with substances other than carbene (e.g., radicals) present in the refrigeration cycle, and therefore can effectively capture carbenes that accumulate in the induction stage. As a result, it is possible to effectively prevent or suppress the concentration of carbene from exceeding the critical condition, thereby making it possible to suppress or alleviate the chain reaction of the disproportionation reaction of the refrigerant component.

[0020] In the method for suppressing the disproportionation reaction of a working fluid for a refrigeration cycle having the above-described configuration, the carbene is selected from the group consisting of CF, CHF, and C n F2 (where n is an integer of 2, 3, or 4).

[0021] In the method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle having the above configuration, capturing the carbene may include reacting the carbene with the carbene scavenger to convert the carbene into a singlet ground state molecule having no unpaired electron.

[0022] In the method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle having the above configuration, capturing the carbenes may include reacting the carbene scavenger with the carbene to cause the carbene scavenger to act as a catalyst, thereby converting two or more of the carbenes into singlet ground state molecules having no unpaired electrons.

[0023] In the method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle having the above configuration, suppressing the disproportionation reaction of the refrigerant components may be configured to suppress an increase in the carbene in the refrigeration cycle, and the suppression of the increase in the carbene may include reducing the carbene concentration below a predetermined upper limit value or making the carbene concentration substantially zero.

[0024] Furthermore, in the method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle having the above configuration, the refrigeration cycle may be configured to include a compressor, the compressor including a discharge region where discharge may occur and a sliding region having sliding parts where a plurality of sliding members slide on each other with their sliding surfaces in contact with each other, and suppressing the disproportionation reaction of the refrigerant components may be configured to suppress an increase of the carbene present in at least one of the discharge region and the sliding region.

[0025] In the method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle having the above configuration, the molar fraction of the carbene present in at least one of the discharge region and the sliding region may be set to 0.35 or less.

[0026] In the method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle having the above configuration, an increase in the carbene may be suppressed by controlling the temperature in at least one of the discharge region and the sliding region to 700 K or less.

[0027] In the method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle having the above configuration, the increase of the carbene may be suppressed by controlling the pressure in at least one of the discharge region and the sliding region from a high-temperature, high-pressure state to 2 MPa or less.

[0028] The present disclosure also includes a method for capturing carbene present in a refrigeration cycle, wherein the composition for a refrigeration cycle contains a carbene scavenger that is more reactive with the carbene than substances other than the carbene present in the refrigeration cycle, and the carbene scavenger is reacted with the carbene present in the refrigeration cycle to capture the carbene present in the refrigeration cycle.

[0029] The present disclosure also includes a composition for a refrigeration cycle that contains a carbene scavenger that is more reactive with the carbene than with substances other than the carbene.

[0030] In the composition for a refrigeration cycle having the above configuration, the carbene scavenger may be a singlet ground state molecule containing π electrons or an unshared electron pair.

[0031] The composition for a refrigeration cycle having the above-described configuration may further contain an ethylene-based fluoroolefin.

[0032] In the composition for a refrigeration cycle having the above configuration, the ethylene-based fluoroolefin may be 1,1,2-trifluoroethylene, trans-1,2-difluoroethylene, cis-1,2-difluoroethylene, 1,1-difluoroethylene, tetrafluoroethylene, or monofluoroethylene.

[0033] The composition for a refrigeration cycle having the above-described configuration may further contain difluoromethane.

[0034] The composition for a refrigeration cycle according to claim 11, further comprising a saturated hydrocarbon.

[0035] In the composition for a refrigeration cycle having the above-described configuration, the saturated hydrocarbon may contain n-propane.

[0036] The composition for a refrigeration cycle having the above-mentioned configuration may also contain a haloalkane having 1 or 2 carbon atoms.

[0037] Furthermore, the present disclosure also includes a refrigeration cycle device containing the refrigeration cycle composition having the above-described configuration.

[0038] Hereinafter, a representative embodiment of the method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to the present disclosure and a representative application thereof will be specifically described.

[0039] [Fluoroolefin] The working fluid for a refrigeration cycle according to the present disclosure, which is the target of the method for suppressing a disproportionation reaction according to the present disclosure, uses, as a refrigerant component, at least a fluoroolefin (fluoroalkene) in which a disproportionation reaction occurs.

[0040] Specific examples of fluoroolefins that undergo such a disproportionation reaction include, but are not limited to, ethylene-based fluoroolefins such as 1,1,2-trifluoroethylene (CF₂=CHF, HFO1123), trans-1,2-difluoroethylene (CHF₂=CHF(E), HFO1132(E)), cis-1,2-difluoroethylene (CHF₂=CHF(Z), HFO1132(Z)), 1,1-difluoroethylene (CF₂=CH₂, HFO1132a), tetrafluoroethylene (CF₂=CF₂, FO1114), and monofluoroethylene (CFH₂=CH₂). These fluoroolefins may be used alone or in combination as a refrigerant component.

[0041] These fluoroolefins have a backbone ethylene structure, i.e., a double bond between carbon atoms, and have a chemical structure in which at least one of the two hydrogen atoms bonded to one carbon atom is substituted with a fluorine atom, or at least one of the four hydrogen atoms bonded to both carbon atoms is substituted with a fluorine atom. Note that in fluoroolefins, some of the hydrogen atoms may be substituted with other atoms or other substituents.

[0042] For example, 1,1,2-trifluoroethylene has a structure in which both of the two hydrogen atoms bonded to one carbon atom (the carbon atom at position 1) of the ethylene structure are substituted with fluorine atoms, and one of the two hydrogen atoms bonded to the other carbon atom (the carbon atom at position 2) is substituted with a fluorine atom.

[0043] Alternatively, trans-1,2-difluoroethylene has a structure in which one of the two hydrogen atoms bonded to the carbon atom at position 1 of the ethylene structure is substituted with a fluorine atom, and of the two hydrogen atoms bonded to the carbon atom at position 2, only the hydrogen atom at the position opposite to the fluorine atom bonded to the carbon atom at position 1 across the double bond, rather than the hydrogen atom adjacent to it, is substituted with a fluorine atom.

[0044] As mentioned above, such fluoroolefins contain an ethylene skeleton, i.e., a carbon-carbon double bond, and this double bond is easily decomposed. That is, atmospheric ozone generates hydroxyl radicals (OH radicals) through photochemical reactions, and these hydroxyl radicals can undergo addition reactions with double bonds, making fluoroolefins easily decomposed. Therefore, fluoroolefins have little impact on ozone layer depletion and global warming.

[0045] Here, fluoroolefins are also known to cause rapid disproportionation reactions due to the aforementioned good decomposition properties. Taking 1,1,2-trifluoroethylene as a typical example of fluoroolefins, this disproportionation reaction involves an autolysis reaction in which 1,1,2-trifluoroethylene molecules decompose, and subsequent to this autolysis reaction, a polymerization reaction occurs in which active radicals or carbenes (hereinafter collectively referred to as active species) produced by the decomposition react with surrounding 1,1,2-trifluoroethylene, or a sooting reaction occurs in which carbon fragments produced by dissociation polymerize to form soot. When active species are generated due to heat generation or the like under high temperature and high pressure conditions, these active species and 1,1,2-trifluoroethylene undergo a polymerization reaction or a sooting reaction, or both, repeatedly, resulting in a disproportionation reaction. Since this disproportionation reaction is exothermic, active radicals are generated by this heat generation, and these active radicals further induce the disproportionation reaction. In this way, the generation of active radicals and the occurrence of disproportionation reactions are linked together, and the spontaneous self-decomposition reaction propagates to other 1,1,2-trifluoroolefins, causing the disproportionation reaction to rapidly proceed.

[0046] Previous intensive research by the present applicant has revealed that the active radicals that induce the disproportionation reaction of 1,1,2-trifluoroethylene are primarily fluorine radicals (F radicals) and trifluoromethyl radicals (CF3 radicals).

[0047] Therefore, the applicant of the present application has independently discovered that it is possible to suppress or mitigate the rapid disproportionation reaction by adding a substance capable of efficiently capturing these active radicals as a "disproportionation inhibitor" to the working fluid for a refrigeration cycle. Furthermore, as disclosed in the above-mentioned Patent Document 1, it is also known to suppress or mitigate the disproportionation reaction by using a radical scavenger.

[0048] However, further intensive studies by the present inventors have revealed that the use of a radical scavenger may not be able to effectively suppress or alleviate the disproportionation reaction of fluoroolefins such as 1,1,2-trifluoroethylene.

[0049] [Carbene Scavenger] The process in which the disproportionation reaction of fluoroolefins progresses rapidly can be divided into an initial stage, an induction stage, and a chain reaction stage. In the initial stage, for example, the occurrence of discharge in a compressor is triggered, and the initial self-decomposition of the fluoroolefin occurs. At this time, active radicals are likely to be generated. The induction stage occurs immediately after the initial stage and immediately before the chain reaction stage, i.e., immediately before the self-decomposition of the fluoroolefin progresses explosively. At this stage, carbenes such as CF2 are gradually generated and accumulate. If the carbene concentration exceeds an upper limit in this induction stage, it is thought that the self-decomposition reaction of the fluoroolefin will progress rapidly.

[0050] Therefore, even if the active radicals are captured and eliminated by a radical scavenger in the initial stage, the carbene will slowly accumulate in the induction stage, and if its concentration exceeds a certain value (critical condition), the process will transition to a chain reaction stage, and the self-decomposition of the fluoroolefin will proceed explosively.

[0051] Here, Patent Document 1, based on the premise that the autolysis reaction pathway of 1,1,2-fluoroolefin (HFO1123) has not been fully elucidated, predicts, based on research using computational chemistry, the generation of carbene species due to cleavage of a carbon-carbon double bond and the generation of radical species accompanied by halogen atom migration in the initial stage of the reaction (paragraph

[0022] of Patent Document 1).

[0052] Based on this prediction, Patent Document 1 considers that it is possible to prevent a chain reaction of autolysis (disproportionation reaction) by capturing the radical species and carbene species that are expected to be generated in the initial stage of the autolysis process at the initial stage of the reaction (paragraph

[0027] of Patent Document 1). As a result, Patent Document 1 proposes radical scavengers of [1] compounds having a C-X (X is Cl, Br, or I) bond, where the C-X bond energy is equal to or lower than the energy of other bonds in the molecule, [2] CX4 (X is Cl, Br, or I, and all four Xs are the same), and [3] Rf-X (Rf is a perfluoroalkyl group having 1 to 6 carbon atoms, and X is Cl, Br, or I).

[0053] However, as their names suggest, these "radical scavengers" are intended to capture active radicals, not carbenes. That is, all of these radical scavengers [1] to [3] are molecules having radical cleavage sites, and are thought to react easily with radicals but have low reactivity with carbenes. In other words, although Patent Document 1 suggests that carbenes are produced in association with the self-decomposition of fluoroolefins, it is thought that the main cause of the progression of chain-like self-decomposition is active radicals.

[0054] In contrast, the inventors' studies have revealed that, as described above, the generation of active radicals is dominant in the initial stage of the self-decomposition of fluoroolefins, and that carbenes are gradually generated in the subsequent induction stage. Therefore, in the present disclosure, the inventors have independently found that, in order to suppress the chain reaction of the self-decomposition of fluoroolefins, it is important to keep the amount of carbenes remaining in the induction stage at or below a predetermined value.

[0055] Therefore, in the present disclosure, a carbene scavenger that is more reactive with carbene than substances other than carbene present in the refrigeration cycle is added to the working fluid for the refrigeration cycle. Thus, the carbene generated in the induction step is captured by the carbene scavenger. As a result, it is possible to suppress the increase of carbene in the refrigeration cycle, and the disproportionation reaction of fluoroolefins can be effectively suppressed or alleviated.

[0056] The method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to the present disclosure can be schematically illustrated, for example, as shown in Fig. 1. In Fig. 1, a compressor 16 is schematically illustrated as a large circle, and a discharge occurrence site, which is one of the triggers for a disproportionation reaction (autolysis reaction of fluoroolefins) within the compressor 16, is schematically illustrated as a discharge region 201 located in the center of the schematic compressor 16.

[0057] The temperature of the discharge region 201 is expected to be approximately 3,000 K to 10,000 K, and a region 201a, shown by the shaded area in FIG. 1 , is generated around the discharge region 201, where the temperature is approximately 400 K to 1,000 K. In this region 201a, products generated by the autolysis of the fluoroolefin accumulate. These products can be considered as "intermediates" rather than final products of the autolysis reaction. Therefore, for ease of explanation, this region 201a is referred to as the reaction intermediate accumulation region 201a. Carbene 31 gradually accumulates in this reaction intermediate accumulation region 201a.

[0058] Therefore, in the present disclosure, the working fluid for a refrigeration cycle contains a carbene scavenger 32. The carbene scavenger 32 is highly reactive with carbene 31 but is relatively less reactive with other substances present in the refrigeration cycle, including the reaction intermediate retention region 201a. Therefore, the carbene scavenger 32 captures the carbene 31 and converts it into a singlet ground state molecule 33 that does not have an unpaired electron. As a result, the progression of chain-like self-decomposition of the fluoroolefin is suppressed or avoided, and the disproportionation reaction can be effectively suppressed or alleviated.

[0059] The carbene scavenger according to the present disclosure may be any substance that is more reactive with carbene than with substances other than carbene present in the refrigeration cycle, and typically may be a singlet ground state molecule containing a π electron or an unshared electron pair. Such a carbene scavenger can be said to react with carbene to convert the carbene into a singlet ground state molecule that does not have an unpaired electron.

[0060] The singlet ground state molecule, which does not have an unpaired electron, is a stable molecule with sufficiently low reactivity, and has an energy difference of 200 kJ / mol or more from the first triplet excited state. By converting the carbene into such a stable molecule, the chain reaction of the self-decomposition of the fluoroolefin is substantially prevented, and the disproportionation reaction can be effectively suppressed or alleviated.

[0061] In the present disclosure, singlet ground state molecules containing π electrons or lone electron pairs, which are cited as typical examples of carbene scavengers, can also be said to have no radical cleavage site, unlike, for example, "radical scavengers" as disclosed in Patent Document 1. An example of a bond that can serve as a radical cleavage site is a dissociative sigma bond with a bond energy of 300 kJ / mol or less. Therefore, the carbene scavengers in the present disclosure can be said to be molecules that do not have a dissociative sigma bond with a bond energy of 300 kJ / mol or less.

[0062] In the present disclosure, the specific type of carbene to be captured by the carbene scavenger is not particularly limited, and may be any carbene generated by the self-decomposition of a fluoroolefin. Representative examples include CF, CHF, and C n and F2 (where n is an integer of 2, 3, or 4). Of these, a representative carbene is CF2.

[0063] The carbene scavenger according to the present disclosure is a substance highly reactive with, for example, CF2, and more specifically, the following substances [1] or [2] can be mentioned.

[0064] [1] A compound having a lowest unoccupied molecular orbital (LUMO) energetically close to the highest occupied molecular orbital (HOMO: ionization energy 11.4 eV) of CF2, i.e., a compound having a high electron affinity and a high Lewis basicity.

[0065] [2] A molecule having a HOMO that is energetically close to the LUMO (electron affinity 0.2 eV) of CF2, that is, a molecule characterized by a small ionization energy.

[0066] Specific examples of such carbene scavengers include ketones having an unshared electron pair. Representative ketones include, but are not limited to, 1,1,1-trifluoroacetone (1,1,1-trifluoro-2-propanone, CF3-CO-CH3), 1,1,1,3,3-pentafluoroacetone (1,1,1,3,3-pentafluoro-2-propanone, CF3-CO-CHF2), 1,1,1,3-tetrafluoroacetone (1,1,1,3-tetrafluoro-2-propanone, CF3-CO-CH2F), and acetone (2-propanone, CH3-CO-CH3).

[0067] Alternatively, the carbene trap according to the present disclosure may act as a catalyst rather than reacting with and trapping the carbene, i.e., in the present disclosure, the carbene trap may be a substance that acts as a catalyst to convert two or more carbenes into singlet ground state molecules with no unpaired electrons.

[0068] The schematic diagram of the method for suppressing a disproportionation reaction shown in Figure 1 illustrates the process of generating singlet ground state molecules from carbene by reacting a carbene with a carbene. In contrast, the schematic diagram of the method for suppressing a disproportionation reaction shown in Figure 2 illustrates the process of generating singlet ground state molecules from carbene by using a carbene trap as a catalyst.

[0069] 2 , when carbene 31 is generated by the self-decomposition of fluoroolefin, carbene 31 is adsorbed (or bound, etc.) to carbene trap 34, which is a "catalyst," to form "metastable state 1." Furthermore, another carbene 31 is adsorbed (or bound, etc.) to the catalyst (carbene trap 34) in this metastable state 1 to form "metastable state 2." In this metastable state 2, two carbenes 31 remain in a state in which they are adsorbed (or bound, etc.) to the catalyst (carbene trap 34). Thereafter, due to the catalytic action of carbene trap 34, two carbenes 31 react to bond with each other, and these carbenes 31 are converted to singlet ground state molecules 33 that do not have unpaired electrons.

[0070] Furthermore, the inventors' intensive studies have revealed that carbenes are likely to be generated not only in the discharge region 201 but also in regions where sliding parts exist within the compressor. The "sliding parts" herein refer to areas where multiple sliding members slide against each other with their sliding surfaces in contact with each other.

[0071] When the likelihood of carbene generation is evaluated over time, as mentioned above, carbene is likely to be generated immediately after the occurrence of discharge that triggers self-decomposition, after the disappearance of radicals generated by self-decomposition, or immediately before the progression of chain reaction self-decomposition. Furthermore, when the likelihood of carbene generation is evaluated in regions within the compressor, carbene is naturally likely to be generated in regions where discharge that triggers self-decomposition may occur, i.e., the discharge region (see Figure 1). Furthermore, it was revealed that carbene is likely to be generated in and near areas that are subject to high temperatures and pressures within the compressor, such as sliding parts.

[0072] In the present disclosure, the region in the compressor where such a sliding part exists is referred to as the “sliding region.” In the method for suppressing a disproportionation reaction according to the present disclosure, it is sufficient if the increase of carbene is suppressed in at least one of the discharge region and the sliding region, or in both the discharge region and the sliding region.

[0073] A typical example of the discharge region and sliding region in a compressor will be specifically described with reference to Fig. 3. Fig. 3 illustrates a rotary (or scroll) compressor. For convenience of explaining the discharge region and sliding region, Fig. 3 illustrates only the essential components related to these regions, and does not illustrate all of the main components of a typical compressor.

[0074] Furthermore, the refrigeration cycle to which the method for suppressing a disproportionation reaction according to the present disclosure is applicable is not limited to a configuration including a rotary (or scroll) compressor as shown in Fig. 3. It goes without saying that the refrigeration cycle to which the present disclosure is applicable may include a reciprocating compressor or any other known type.

[0075] Similarly, in the present disclosure, regardless of whether the compressor is of a rotary type (or scroll type), the components of the compressor are not limited to the essential configuration schematically shown in Fig. 3. In various known types of compressors, the area where discharge can occur and its surroundings may be referred to as the "discharge area," and the area where high temperature and high pressure occur and its surroundings may be referred to as the "sliding area" (or high temperature and high pressure area).

[0076] 3 includes an electric motor unit 162 and a compression mechanism unit 163 housed within a sealed container 161. The electric motor unit 162 and the compression mechanism unit 163 are connected by a shaft 166. The electric motor unit 162 is composed of at least a stator 164 fixed to the inner surface of the sealed container 161 and a rotor 165 that rotates within the stator 164.

[0077] An airtight power supply terminal 173 is hermetically welded to the sealed container 161. The airtight power supply terminal 173 is electrically connected to an external power supply, and is also electrically connected to the stator 164 of the electric motor unit 162 via wiring 174 inside the sealed container 161. This allows power to be supplied from the external power supply to the electric motor unit 162.

[0078] The compressor 16 includes a compression mechanism 163, which includes a first compression mechanism 163A and a second compression mechanism 163B. The first compression mechanism 163A includes a first piston 169A disposed within a first cylinder and a vane that divides the first cylinder. The first piston 169A revolves within the first cylinder, thereby drawing in and compressing low-pressure refrigerant gas (a working medium for the refrigeration cycle). The first piston 169A is disposed within the first cylinder so as to be capable of revolving, thereby forming a first compression chamber 172A.

[0079] Similar to the first compression mechanism 163A, the second compression mechanism 163B also includes a second piston 169B disposed within a second cylinder and a vane that divides the second cylinder. The second piston 169B revolves within the second cylinder, thereby drawing in and compressing low-pressure refrigerant gas (a working medium for the refrigeration cycle). The second piston 169B is disposed within the second cylinder so as to be capable of revolving, thereby forming a second compression chamber 172B.

[0080] The shaft 166 has the rotor 165 fixed thereto, and is rotatably supported by a main bearing 167 and a sub-bearing 168. A first piston 169A and a second piston 169B are also fixed to the shaft 166 with a phase difference of 180 degrees from each other.

[0081] Lubricating oil is stored at the bottom of the sealed container 161, and this lubricating oil is passed through an oil supply passage formed in the shaft 166 to lubricate the sliding part formed by the shaft 166 and the main bearing 167, or the sliding part formed by the shaft 166 and the auxiliary bearing 168.

[0082] A first suction pipe 171A and a second suction pipe 171B are connected to the side of the sealed container 161. The first suction pipe 171A is connected to the first compression chamber 172A, and the second suction pipe 171B is connected to the second compression chamber 172B. An accumulator 170 is provided upstream of the first suction pipe 171A and the second suction pipe 171B. The accumulator 170 separates the refrigerant in a gas-liquid mixed state that has returned from the refrigeration cycle into liquid refrigerant and gas refrigerant. Gas refrigerant flows through the first suction pipe 171A and the second suction pipe 171B.

[0083] As the shaft 166 rotates, the first piston 169A and the second piston 169B revolve within the first compression chamber 172A and the second compression chamber 172B. The gas refrigerant is drawn into the first compression chamber 172A and the second compression chamber 172B from the first suction pipe 171A and the second suction pipe 171B by the orbital motion of the first piston 169A and the second piston 169B, is compressed in the first compression chamber 172A and the second compression chamber 172B, and then discharged into the sealed container 161. The gas refrigerant separates from the lubricating oil while passing through the electric motor unit 162 and rising, and is then discharged out of the sealed container 161 from the discharge pipe.

[0084] 3, discharge regions 201A and 201B are areas surrounded by dashed lines, and the sliding region is an area surrounded by a dotted line frame within compressor 16. Of these, discharge region 201A is the winding portion of stator 164 constituting motor section 162 and its surroundings, and discharge region 201B is airtight power supply terminal 173 and its surroundings.

[0085] On the other hand, in the configuration example shown in FIG. 3, examples of sliding parts (parts where multiple sliding members are combined and slide with their sliding surfaces in contact with each other) that are likely to become high temperature and high pressure within the compressor 16 include the space between the first piston 169A or the second piston 169B and the vane, the space between the main bearing 167 and the shaft 166, and the space between the rotor 165 and the main bearing 167.

[0086] 3, for example, the area between and around the first piston 169A and the vane, and the area between and around the second piston 169B and the vane are defined as sliding areas 202A surrounded by dotted lines. Similarly, the area between and around the main bearing 167 and the shaft 166 is defined as sliding area 202B (area surrounded by dotted lines), and the area between and around the rotor 165 and the main bearing 167 is defined as sliding area 202C (area surrounded by dotted lines).

[0087] In the present disclosure, it is sufficient that an increase in carbenes can be suppressed by a carbene scavenger in a refrigeration cycle including the compressor 16. Furthermore, it is sufficient that an increase in carbenes can be suppressed by a carbene scavenger in at least one of the discharge regions 201A and 201B and the sliding regions 202A to 202C in the compressor 16 of the refrigeration cycle.

[0088] In particular, if the carbene scavenger can suppress the increase of carbenes in the discharge regions 201A and 201B, the allowable discharge energy value, i.e., the discharge energy value at which the self-decomposition of fluoroolefins does not proceed in a chain reaction, becomes higher, and the disproportionation reaction can be further suppressed or alleviated.

[0089] Note that, although the example shown in FIG. 3 illustrates two discharge regions and three sliding regions within compressor 16, the number of discharge regions and sliding regions in the present disclosure is not limited to the example shown in FIG. 3. There may be multiple discharge regions within compressor 16, or there may be only one sliding region. In the present disclosure, "at least one of a discharge region and a sliding region" refers to at least one region among multiple discharge regions and multiple sliding regions within compressor 16. Furthermore, "at least one of a discharge region and a sliding region" includes cases where there is only one or multiple discharge regions, cases where there are one or multiple sliding regions, and also includes all discharge regions and sliding regions.

[0090] In the method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to the present disclosure, the increase of carbenes in the refrigeration cycle can be suppressed by the carbene scavenger, and as a result, the disproportionation reaction of the fluoroolefin contained in the working fluid for a refrigeration cycle can be suppressed or alleviated. Therefore, in the present disclosure, to suppress the increase of carbenes, an upper limit of the carbene concentration in the refrigeration cycle is set in advance, and when the carbene concentration falls below the upper limit due to the carbene scavenger, it can be determined that the increase of carbenes has been suppressed.

[0091] Alternatively, in the present disclosure, it may be determined that an increase in carbene has been suppressed when it is confirmed that the carbene concentration in the refrigeration cycle is substantially 0. That is, when the carbene concentration in the refrigeration cycle has decreased to a level that can be regarded as an impurity in the working fluid for the refrigeration cycle and the working fluid is in a state in which it does not substantially contain carbene, it may be determined that the carbene concentration has become substantially 0 and that the carbene concentration has been suppressed.

[0092] The upper limit of the carbene concentration is appropriately set depending on various conditions including the specific configuration of the refrigeration cycle or the compressor, and is not particularly limited. A typical upper limit may be set such that the molar fraction of carbene is 0.35 (mol / mol) or less in at least one of the discharge region and the sliding region.

[0093] As is clear from the simulation results (Table 1) of the Examples described later, when the molar fraction of carbene was 0.4 (Comparative Example), the disproportionation reaction was not successfully inhibited at any of the initial pressures of 0.6 MPa, 2.0 MPa, and 6.0 MPa at an initial temperature of 423 K. On the other hand, when the molar fraction of carbene was 0.3, the disproportionation reaction was successfully inhibited at any of the initial pressures of 0.6 MPa, 2.0 MPa, and 6.0 MPa at an initial temperature of 423 K.

[0094] As will be described later, by comprehensively examining the results of the examples, it can be determined that the disproportionation reaction can be suppressed if the carbene molar fraction is 0.35 or less. As described above, since carbenes are likely to be generated in the discharge region or the sliding region, by setting the upper limit of the carbene concentration in at least one of the discharge region and the sliding region to 0.35 or less in molar fraction and adding a carbene scavenger so that the concentration is below this upper limit, it is possible to effectively suppress or mitigate the disproportionation reaction of fluoroolefins.

[0095] Furthermore, in the present disclosure, not only the upper limit of the carbene concentration but also the temperature or pressure at which carbene is likely to be generated by the self-decomposition of the fluoroolefin can be lowered to suppress an increase in carbene.

[0096] For example, in the present disclosure, the increase in carbene may be suppressed by controlling the temperature in at least one of the discharge region and the sliding region to 700 K or less. Alternatively, the increase in carbene may be suppressed by controlling the pressure in at least one of the discharge region and the sliding region from a high-temperature, high-pressure state to 2 MPa or less.

[0097] If the upper temperature limit in the discharge region or the sliding region is set to 700 K or less, or if the upper pressure limit is set to 2 MPa or less, either of the high-temperature and high-pressure conditions for the occurrence of the fluoroolefin self-decomposition reaction and the propagation of the spontaneous self-decomposition reaction will not be fully satisfied. As a result, even if the fluoroolefin self-decomposes, the generation of carbene will be significantly suppressed. As a result, the increase of carbene can be effectively suppressed in the discharge region or the sliding region.

[0098] In the method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to the present disclosure, the specific method for capturing the carbene is not necessarily limited to the above-described configuration. In the present disclosure, capturing the carbene may include reacting the carbene with the carbene to convert the carbene into a singlet ground state molecule having no unpaired electron. Alternatively, in the present disclosure, capturing the carbene may include reacting the carbene with the carbene to convert two or more carbenes into singlet ground state molecules having no unpaired electrons by using the carbene trap as a catalyst.

[0099] Therefore, the present disclosure includes not only a method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle, but also a method for capturing carbenes present in the refrigeration cycle. Specifically, the carbene capturing method according to the present disclosure may be configured such that, in a refrigeration cycle containing a composition for a refrigeration cycle, the composition for a refrigeration cycle described below contains a carbene scavenger that is more reactive with carbene than substances other than carbene present in the refrigeration cycle, and the carbene scavenger is reacted with the carbene present in the refrigeration cycle to capture the carbene present in the refrigeration cycle.

[0100] [Configuration Example of Refrigeration Cycle System] Next, a refrigeration cycle to which the method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to the present disclosure is applied will be described with reference to a representative "refrigeration cycle system (refrigeration cycle device)" shown in FIGS. 4A and 4B .

[0101] The specific configuration of the refrigeration cycle system according to the present disclosure is not particularly limited as long as components such as a compressor, a condenser, an expansion means, and an evaporator are connected by piping. Specific application examples of the refrigeration cycle system according to the present disclosure are also not particularly limited, and examples include air conditioners, refrigerators (for home and commercial use), dehumidifiers, showcases, ice makers, heat pump water heaters, heat pump washer-dryers, and vending machines.

[0102] An air conditioner will be described as a typical application example of the refrigeration cycle system according to the present disclosure. Specifically, as shown in the block diagram of Fig. 4A, an air conditioner 10 according to this embodiment includes an indoor unit 11, an outdoor unit 12, and piping 13 connecting these. The indoor unit 11 includes a heat exchanger 14, and the outdoor unit 12 includes a heat exchanger 15, a compressor 16, and a pressure reducing device 17.

[0103] The heat exchanger 14 of the indoor unit 11 and the heat exchanger 15 of the outdoor unit 12 are connected in a ring shape by piping 13, thereby forming a refrigeration cycle according to the present disclosure. Specifically, the heat exchanger 14 of the indoor unit 11, the compressor 16, the heat exchanger 15 of the outdoor unit 12, and the pressure reducing device 17 are connected in this order by piping 13 in a ring shape. The piping 13 connecting the heat exchanger 14, the compressor 16, and the heat exchanger 15 is provided with a four-way valve 18 for switching between heating and cooling. The indoor unit 11 is equipped with a blower fan, a temperature sensor, an operating unit, etc. (not shown), and the outdoor unit 12 is equipped with a blower, an accumulator, etc. (not shown). The piping 13 is also provided with various valve devices (including the four-way valve 18), a strainer, etc. (not shown).

[0104] The heat exchanger 14 provided in the indoor unit 11 exchanges heat between indoor air drawn into the indoor unit 11 by the blower fan and the refrigerant flowing inside the heat exchanger 14. During heating, the indoor unit 11 blows air heated by heat exchange into the room, and during cooling, it blows air cooled by heat exchange into the room. The heat exchanger 15 provided in the outdoor unit 12 exchanges heat between outside air drawn into the outdoor unit 12 by the blower and the refrigerant flowing inside the heat exchanger 15.

[0105] The specific configurations of the indoor unit 11 and the outdoor unit 12, or the specific configurations of the heat exchanger 14 or heat exchanger 15, compressor 16, pressure reducing device 17, four-way valve 18, blower fan, temperature sensor, operating unit, blower, accumulator, other valve devices, strainer, etc. are not particularly limited, and known configurations can be suitably used.

[0106] An example of the operation of the air conditioner 10 shown in Figure 4A will be described in detail. First, during cooling operation or dehumidification operation, the compressor 16 of the outdoor unit 12 compresses and discharges gas refrigerant, which is then sent to the heat exchanger 15 of the outdoor unit 12 via the four-way valve 18. The heat exchanger 15 exchanges heat between the outside air and the gas refrigerant, causing the gas refrigerant to condense and liquefy. The liquefied liquid refrigerant is depressurized by the pressure reducing device 17 and sent to the heat exchanger 14 of the indoor unit 11. In the heat exchanger 14, the liquid refrigerant evaporates into gas refrigerant through heat exchange with the indoor air. This gas refrigerant returns to the compressor 16 of the outdoor unit 12 via the four-way valve 18. The compressor 16 compresses the gas refrigerant and discharges it again to the heat exchanger 15 via the four-way valve 18.

[0107] Furthermore, during heating operation, the compressor 16 of the outdoor unit 12 compresses and discharges gas refrigerant, which is then sent to the heat exchanger 14 of the indoor unit 11 via the four-way valve 18. In the heat exchanger 14, the gas refrigerant condenses and liquefies through heat exchange with the indoor air. The liquefied liquid refrigerant is decompressed by the pressure reducing device 17 to become a two-phase gas-liquid refrigerant and is sent to the heat exchanger 15 of the outdoor unit 12. As the heat exchanger 15 exchanges heat between the outside air and the two-phase gas-liquid refrigerant, the two-phase gas-liquid refrigerant evaporates and becomes gas refrigerant, which returns to the compressor 16. The compressor 16 compresses the gas refrigerant and discharges it again via the four-way valve 18 to the heat exchanger 14 of the indoor unit 11.

[0108] Furthermore, a refrigerator will be described as another typical application example of the refrigeration cycle system (refrigeration cycle device) according to the present disclosure. Specifically, as schematically shown in the block diagram of Fig. 4B, refrigerator 20 according to this embodiment includes compressor 21, condenser 22, pressure reducing device 23, evaporator 24, and piping 25. Refrigerator 20 also includes a housing, a blower, an operation unit, a control unit, and the like, which are not shown.

[0109] The compressor 21 compresses refrigerant gas to produce a high-temperature, high-pressure gas refrigerant. The condenser 22 cools the refrigerant to liquefy it. The pressure reducing device 23, which is formed, for example, by a capillary tube, reduces the pressure of the liquefied refrigerant (liquid refrigerant). The evaporator 24 evaporates the refrigerant to produce a low-temperature, low-pressure gas refrigerant. The compressor 21, condenser 22, pressure reducing device 23, and evaporator 24 are connected in this order in a ring shape by piping 25 that circulates the refrigerant gas, thereby forming a refrigeration cycle.

[0110] The configurations of compressor 21, condenser 22, pressure reducing device 23, evaporator 24, piping 25, main body housing, blower, operation unit, control unit, etc. are not particularly limited, and known configurations can be suitably used. Furthermore, refrigerator 20 may have known configurations other than those described above.

[0111] An example of the operation of refrigerator 20 shown in Fig. 4B will be described in detail. Compressor 21 compresses gas refrigerant and discharges it to condenser 22. Condenser 22 cools the gas refrigerant to liquid refrigerant. The liquid refrigerant is reduced in pressure by passing through pressure reducing device 23 and sent to evaporator 24. In evaporator 24, the liquid refrigerant absorbs heat from the surroundings and is vaporized as gas refrigerant, which returns to compressor 21. Compressor 21 compresses the gas refrigerant and discharges it again to condenser 22.

[0112] Such an air conditioner 10 or refrigerator 20 is equipped with a refrigeration cycle (refrigeration cycle system) configured using the working fluid for the refrigeration cycle described above. The fluoroolefin used in the working fluid for the refrigeration cycle has good properties as a refrigerant component and has small ODP and GWP. Moreover, as described above, the working fluid for the refrigeration cycle contains a carbene scavenger.

[0113] Therefore, the carbene generated in the self-decomposition of the fluoroolefin is captured by the carbene scavenger. This effectively suppresses the increase of the carbene in the refrigeration cycle, thereby suppressing or avoiding the chain reaction of the self-decomposition of the fluoroolefin. This makes it possible to suppress or alleviate the disproportionation reaction of the fluoroolefin.

[0114] [Working fluid for refrigeration cycle and composition for refrigeration cycle] The present disclosure also includes a working fluid for a refrigeration cycle containing the above-mentioned carbene scavenger. Specifically, the working fluid for a refrigeration cycle according to the present disclosure may contain, as a refrigerant component, a fluoroolefin that undergoes a disproportionation reaction, as described above, and may also contain a carbene scavenger to capture the carbene generated in the disproportionation reaction. As described above, a specific carbene scavenger may be a component that is more reactive with carbene than with substances other than carbene. Representative examples of the carbene scavenger include singlet ground state molecules containing π electrons or lone electron pairs, and more specific examples of such compounds include ketones.

[0115] The working fluid for a refrigeration cycle according to the present disclosure may contain, as a refrigerant component, difluoromethane (HFC32, R32, chemical formula: CHF) in addition to the fluoroolefin. In this case, if the fluoroolefin is considered to be the "main component" of the refrigerant component in the working fluid for a refrigeration cycle according to the present disclosure, the difluoromethane is considered to be the "secondary component" of the refrigerant component in the working fluid for a refrigeration cycle according to the present disclosure.

[0116] As mentioned above, difluoromethane has an ozone depletion potential (ODP) of 0 and has good refrigerant performance compared to the HCFCs (hydrochlorofluorocarbons) that have been used up to now.

[0117] The working fluid for a refrigeration cycle according to the present disclosure may contain a refrigerant component other than difluoromethane as a secondary refrigerant component. Examples of such a secondary refrigerant component include, but are not limited to, hydrofluorocarbons (HFCs) such as difluoroethane, trifluoroethane, tetrafluoroethane, pentafluoroethane, pentafluoropropane, hexafluoropropane, heptafluoropropane, pentafluorobutane, and heptafluorocyclopentane; and hydrofluoroolefins (HFOs) such as monofluoropropene, trifluoropropene, tetrafluoropropene, pentafluoropropene, and hexafluorobutene.

[0118] In addition, as the secondary refrigerant component, saturated hydrocarbons such as ethane, n-propane, cyclopropane, n-butane, cyclobutane, isobutane (2-methylpropane), methylcyclopropane, n-pentane, isopentane (2-methylbutane), neopentane (2,2-dimethylpropane), methylcyclobutane, etc., or carbon dioxide, etc. can also be used.

[0119] These secondary refrigerant components are known to have little impact on ozone layer depletion and global warming, and can therefore be used in combination with fluoroolefins, or with fluoroolefins and difluoromethane, as refrigerant components. The aforementioned secondary refrigerant components may be used alone or in appropriate combination of two or more.

[0120] The content of the secondary refrigerant component is not particularly limited. In the present disclosure, it is sufficient that the fluoroolefin is the main refrigerant component, and therefore, in the working fluid for a refrigeration cycle according to the present disclosure, the content of the fluoroolefin is sufficient to be higher than the content of the secondary refrigerant component.

[0121] However, in the working fluid for a refrigeration cycle according to the present disclosure, it is important to make the GWP as small as possible. Specifically, the GWP is desirably 200 or less (GWP≦200), and more desirably 150 or less (GWP≦150). When a fluoroolefin is used as the main refrigerant component and, for example, difluoromethane is used as the secondary refrigerant component, the upper limit of the difluoromethane content may be 30% by mass or less, or may be 25% by mass or less, or may be 20% by mass or less, of the total amount of refrigerant-related components.

[0122] When the difluoromethane content is 30% by mass or less, the GWP of the working fluid for a refrigeration cycle can be set to 200 or less, and when it is 20% by mass or less, the GWP of the working fluid for a refrigeration cycle can be set to 150 or less. The lower limit of difluoromethane is not particularly limited. The working fluid for a refrigeration cycle according to the present disclosure does not need to contain difluoromethane, so the difluoromethane content may be 0% by mass or more.

[0123] Furthermore, in the present disclosure, the working fluid for a refrigeration cycle may contain a disproportionation inhibitor in addition to the carbene scavenger. Examples of such disproportionation inhibitors include saturated hydrocarbons and haloalkanes.

[0124] Examples of saturated hydrocarbons include those having 2 to 5 carbon atoms, such as ethane, n-propane, cyclopropane, n-butane, cyclobutane, isobutane (2-methylpropane), methylcyclopropane, n-pentane, isopentane (2-methylbutane), neopentane (2,2-dimethylpropane), and methylcyclobutane. These saturated hydrocarbons may be used alone or in appropriate combination of two or more. Among these saturated hydrocarbons, n-propane is a representative example.

[0125] The haloalkane used as the disproportionation inhibitor is not particularly limited as long as it has a disproportionation inhibitory effect, but representative examples include haloalkanes having 1 or 2 carbon atoms. Specific examples include haloalkanes having 2 carbon atoms, i.e., haloethanes (halogenated ethanes), and haloalkanes having 1 carbon atom, i.e., halomethanes (halogenated methanes).

[0126] Among the haloalkanes having 1 or 2 carbon atoms, the halomethane may specifically be one having the structure of the following formula (1): CH m X n ... (1)

[0127] In formula (1), X is a halogen atom selected from the group consisting of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I), m is an integer of 0 or greater, n is an integer of 1 or greater, the sum of m and n is 4, and when n is 2 or greater, X is the same or different halogen atom.

[0128] That is, the halomethane shown in formula (1) may be at least one of the monohalomethane shown in formula (11), the dihalomethane shown in formula (12), the trihalomethane shown in formula (13), and the tetrahalomethane shown in formula (14). X in these halomethanes shown in formulas (11) to (14) 1 , X2 , X 3 , and X 4 Each independently represents one halogen atom. 1 ~X 4 may be different types of halogen atoms, or at least two may be the same type and the others may be different types of halogen atoms, or all may be the same type of halogen atom. 1 ... (11) CH2X 1 X 2 ... (12) CHX 1 X 2 X 3 ... (13) CX 1 X 2 X 3 X 4 ... (14)

[0129] Specific examples of the halomethane represented by formula (1) include, but are not limited to, (mono)iodomethane (CH3I), diiodomethane (CH2I2), dibromomethane (CH2Br2), bromomethane (CH3Br), dichloromethane (CH2Cl2), chloroiodomethane (CH2ClI), dibromochloromethane (CHBr2Cl), tetraiodomethane (CI4), carbon tetrabromide (CBr4), bromotrichloromethane (CBrCl3), dibromodichloromethane (CBr2Cl2), tribromofluoromethane (CBr3F), difluoroiodomethane (CHF2I), fluorodiiodomethane (CHFI2), difluorodiiodomethane (CF2I2), dibromodifluoromethane (CBr2F2), and trifluoroiodomethane (CF3I). These halomethanes may be used alone or in combination of two or more.

[0130] Among the haloalkanes having 1 or 2 carbon atoms, the haloethane may specifically be one having the structure of the following formula (2): CH p X q... (2) However, in formula (2), X is a halogen atom selected from the group consisting of F, Cl, Br, and I, similar to the halomethanes described above, p is an integer of 0 or greater, and q is an integer of 1 or greater, the sum of p and q is 6, and when q is 2 or greater, X is the same or a different type of halogen atom.

[0131] That is, the haloethane shown in formula (2) may be at least one of a monohaloethane shown in the following formula (21), a dihaloethane shown in the following formula (22), a trihaloethane shown in the following formula (23), a tetrahaloethane shown in the following formula (24), a pentahaloethane shown in the following formula (25), and a hexahaloethane shown in the following formula (26).

[0132] X in the haloethanes shown in formulas (21) to (26) 1 , X 2 , X 3 , X 4 , X 5 , and X 6 Each independently represents one halogen atom. 1 ~X 6 may be different types of halogen atoms, or at least two may be the same type and the others may be different types of halogen atoms, or all may be the same type of halogen atom. 1 CH3... (21) CHX 1 X 2 CH3... (22) CX 1 X 2 X 3 CH3... (23) CX 1 X 2 X 3 CH2X 4 ... (24) CX 1 X 2 X 3 CHX 4 X 5 ... (25) CX 1 X 2 X 3 CX 4 X 5 X 6... (26)

[0133] The specific haloethane represented by formula (2) is not particularly limited, and examples thereof include 1,1,1-trifluoro-2-iodoethane (CFCHI), monoiodoethane (CHCHI), monobromoethane (CHCHBr), 1,1,1-triiodoethane (CHCI), etc. These haloethanes may be used alone or in appropriate combination of two or more.

[0134] The working fluid for a refrigeration cycle according to the present disclosure is used in a refrigeration cycle system, and therefore can be used in combination with a lubricating oil (refrigerating machine oil) that lubricates a compressor provided in the refrigeration cycle system.

[0135] As described above, the working fluid for a refrigeration cycle according to the present disclosure may contain, as refrigerant components, a fluoroolefin (e.g., 1,1,2-trifluoroethylene) that undergoes a disproportionation reaction and difluoromethane in combination, and may further contain a carbene scavenger. Furthermore, in the present disclosure, when the working fluid for a refrigeration cycle is used in combination with a lubricating oil, the refrigeration cycle composition (or working fluid-containing composition) can be considered to be composed of the refrigerant component, the carbene scavenger, the lubricating oil component, and other components. In the working fluid for a refrigeration cycle according to the present disclosure, the carbene scavenger may be mixed with the refrigerant component, but may also be mixed with the lubricating oil component depending on the circumstances.

[0136] The lubricating oil component contained in the refrigeration cycle composition (used together with the working fluid for the refrigeration cycle) can suitably be any of various lubricating oils known in refrigeration cycle systems. Specific examples of the lubricating oil include, but are not limited to, ester-based lubricating oils, ether-based lubricating oils, glycol-based lubricating oils, alkylbenzene-based lubricating oils, fluorine-based lubricating oils, mineral oils, and hydrocarbon-based synthetic oils. These lubricating oils may be used alone or in combination of two or more.

[0137] In addition, various known additives other than disproportionation inhibitors may be added to the refrigeration cycle composition. Specific additives include, but are not limited to, various stabilizers, antioxidants, moisture scavengers, metal deactivators, anti-wear agents, antifoaming agents, and leak detection substances. Antioxidants are used to improve the thermal stability, oxidation resistance, chemical stability, etc. of refrigerant components or lubricating oils. Moisture scavengers are used to remove moisture when it enters the refrigeration cycle system, particularly to suppress changes in the properties of lubricating oils. Metal deactivators are used to suppress or prevent chemical reactions caused by the catalytic action of metal components. Anti-wear agents are used to reduce wear on sliding parts in compressors, especially during high-pressure operation. Antifoaming agents are used, particularly, to suppress the generation of bubbles in lubricating oils.

[0138] The specific types of these additives are not particularly limited, and known compounds can be suitably used depending on various conditions. Furthermore, as these additives, only one type of compound or an appropriate combination of two or more types of compounds can be used. Furthermore, the amounts of these additives added are not particularly limited, and they can be added within known ranges as long as they do not impair the properties of the working fluid for a refrigeration cycle according to the present disclosure or the composition for a refrigeration cycle containing the same.

[0139] In other words, the composition for a refrigeration cycle according to the present disclosure may contain a carbene scavenger that is more reactive with carbenes than substances other than carbenes, as described above, and the carbene scavenger may be a singlet ground state molecule that contains π electrons or an unshared electron pair, as described above.

[0140] The refrigeration cycle composition according to the present disclosure may further contain an ethylene-based fluoroolefin, which may be, but is not limited to, 1,1,2-trifluoroethylene, trans-1,2-difluoroethylene, cis-1,2-difluoroethylene, 1,1-difluoroethylene, tetrafluoroethylene, or monofluoroethylene.

[0141] Furthermore, the refrigeration cycle composition according to the present disclosure may further contain difluoromethane, or may further contain a saturated hydrocarbon. The saturated hydrocarbon may be any hydrocarbon containing n-propane. Furthermore, the refrigeration cycle composition according to the present disclosure may contain a haloalkane having one or two carbon atoms. Furthermore, the above-mentioned refrigeration cycle system (refrigeration cycle device) can be said to contain (be equipped with) the above-mentioned refrigeration cycle composition.

[0142] The present invention will be described in more detail based on examples and comparative examples, but the present invention is not limited thereto. Those skilled in the art can make various changes, modifications, and alterations without departing from the scope of the present invention. In addition, the simulation of the disproportionation reaction of fluoroolefins in the following examples was carried out as follows.

[0143] (Simulation of Disproportionation Reaction) In the disproportionation reaction of 1,1,2-trifluoroethylene, a fluoroolefin, the equilibrium structures of all reactants and products were calculated by density functional theory, and the reaction path and intrinsic reaction path were determined by the global reaction route mapping (GRRM) method.

[0144] For the determined intrinsic reaction path, the forward and reverse reaction rates at various temperatures were calculated using transition state theory, and the temperature dependence of the calculated reaction rates was fitted by the extended Arrhenius equation.

[0145] Based on the obtained fitting parameters of the reaction rate, the reaction time evolution in a closed homogeneous vessel (CHR) was calculated using the multiphysics analysis platform ChemkinPro (product name, manufactured by Ansys Inc.).

[0146] Example 1 Using the above-described CHR method, a simulation was performed under the conditions of an initial temperature of 423 K, initial pressures of 0.6 MPa, 2.0 MPa, and 6.0 MPa, and a carbene concentration at a molar fraction of 0.1 (mol / mol), while varying the molar fraction of 1,1,2-trifluoroethylene molecules and carbene generated by the thermal decomposition thereof, and the reaction progress over 60 seconds was confirmed.

[0147] At each initial pressure, if all reactants were converted to final products (carbon, CF4, HF) within a specified time (within 60 seconds) and a rapid increase in pressure and temperature (a characteristic of spontaneous reaction propagation) was observed, the suppression was evaluated as unsuccessful (×), and if some reactants were converted to products but no rapid increase in pressure and temperature was observed, the suppression was evaluated as successful (◯). The results are shown in Table 1.

[0148] Example 2 A simulation was performed in the same manner as in Example 1, except that the carbene concentration was set to a molar fraction of 0.2 (mol / mol), and the failure or success of suppression was evaluated at each initial pressure. The results are shown in Table 1.

[0149] Example 3 A simulation was performed in the same manner as in Example 1, except that the carbene concentration was set to a molar fraction of 0.3 (mol / mol), and the failure or success of suppression was evaluated at each initial pressure. The results are shown in Table 1.

[0150] Comparative Example A simulation was performed in the same manner as in Example 1, except that the carbene concentration was set to a molar fraction of 0.4 (mol / mol), and the failure or success of suppression was evaluated at each initial pressure. The results are shown in Table 1.

[0151]

[0152] (Comparison of Examples 1 to 3 and Comparative Example 1) As is clear from the results in Table 1, when the carbene concentration is 0.1 to 0.3 (mol / mol) in terms of molar fraction, the disproportionation reaction can be effectively suppressed regardless of the initial pressure. On the other hand, when the carbene concentration is 0.4 (mol / mol) in terms of molar fraction, the disproportionation reaction cannot be suppressed regardless of the initial pressure.

[0153] In particular, in the simulations of Examples 1 to 3 and Comparative Example 1, even when the most severe initial pressure of 6.0 MPa was used as the standard, successful suppression results were obtained as long as the carbene concentration was 0.35 or less in mole fraction. Therefore, in the present disclosure, it is found to be effective to set the upper limit of the carbene concentration to 0.35 or less in the refrigeration cycle, particularly in the compressor.

[0154] (Experimental system for disproportionation reaction) A pressure sensor for measuring the internal pressure in the pressure-resistant vessel (internal volume 50 mL), a thermocouple for measuring the internal temperature in the pressure-resistant vessel, and a discharge device for generating a discharge in the pressure-resistant vessel were attached to a sealed pressure-resistant vessel (internal volume 50 mL).

[0155] Furthermore, a gas cylinder (HFO1123 gas cylinder) of the refrigerant component 1,1,2-trifluoroethylene (containing 5% limonene (liquid phase) as a stabilizer) was connected to the pressure-resistant vessel so that the pressure could be adjusted. The pressure sensor and thermometer attached to the pressure-resistant vessel were connected to a data logger. In this way, an experimental system for the disproportionation reaction was constructed.

[0156] Comparative Example 2 In the experimental system, 1,1,2-trifluoroethylene was introduced into the pressure vessel from a gas cylinder of HFO1123. Therefore, the content of 1,1,2-trifluoroethylene in the working fluid for the refrigeration cycle in the pressure vessel was 100% by mass.

[0157] To induce the disproportionation reaction of 1,1,2-trifluoroethylene, a discharge was generated by a discharge device at a discharge voltage of 100 V under conditions of 25°C and an internal pressure of 1.3 MPa. After that, when the inside of the pressure vessel was checked after the internal pressure and temperature had sufficiently decreased, a considerable amount of soot was found to have been generated, confirming the occurrence of the disproportionation reaction of 1,1,2-trifluoroethylene.

[0158] Example 4 In the above-described experimental system, 1,1,2-trifluoroethylene was introduced into a pressure-resistant vessel from an HFO1123 gas cylinder, and 1,1,1-trifluoroacetone (CF3-CO-CH3) was added as a disproportionation inhibitor so that the content was 9.7% by mass.

[0159] Except for this, a discharge was generated in the pressure vessel in the same manner as in Comparative Example 2, but no significant increase in pressure or temperature was observed. After that, the inside of the pressure vessel was checked, but no occurrence of a disproportionation reaction of 1,1,2-trifluoroethylene was confirmed.

[0160] The present invention is not limited to the description of the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments or multiple modified examples are also included in the technical scope of the present invention.

[0161] Furthermore, many modifications and other embodiments of the present invention will be apparent to those skilled in the art from the above description. Therefore, the above description should be construed as illustrative only and is provided for the purpose of teaching those skilled in the art the best mode for carrying out the present invention. Details of the structure and / or function thereof may be substantially changed without departing from the spirit of the present invention.

[0162] (Additional Notes) Based on the descriptions of the above embodiments, the present specification discloses the following technologies: (Technology 1) A method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle, in which a working fluid for a refrigeration cycle containing a refrigerant component that undergoes a disproportionation reaction circulates, comprising: capturing the carbene produced by the disproportionation reaction of the refrigerant component using a carbene scavenger that is more reactive with the carbene than substances other than the carbene present in the refrigeration cycle, thereby suppressing the disproportionation reaction of the refrigerant component.

[0163] (Technique 2) The carbene is CF2, CHF, and C n 2. The method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to claim 1, wherein the working fluid contains at least one selected from the group consisting of F2 (where n is an integer of 2, 3, or 4).

[0164] (Technology 3) The method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to Technology 1 or Technology 2, wherein capturing the carbene includes reacting the carbene with the carbene to convert the carbene into a singlet ground state molecule having no unpaired electron.

[0165] (Technology 4) The method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to Technology 1 or Technology 2, wherein capturing the carbene includes reacting the carbene with the carbene and causing the carbene scavenger to act as a catalyst to convert two or more of the carbenes into singlet ground state molecules having no unpaired electrons.

[0166] (Technology 5) The method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to any one of Technology 1 to Technology 4, wherein suppressing the disproportionation reaction of the refrigerant components means suppressing an increase of the carbene in the refrigeration cycle, and the suppression of the increase of the carbene includes making the carbene concentration lower than a predetermined upper limit value or making the carbene concentration substantially zero.

[0167] (Technology 6) The method for suppressing a disproportionation reaction of a working medium for a refrigeration cycle according to any one of Technology 1 to Technology 5, wherein the refrigeration cycle includes a compressor, the compressor including a discharge region where discharge can occur and a sliding region having sliding parts where a plurality of sliding members slide on each other with their sliding surfaces in contact with each other, and suppressing the disproportionation reaction of the refrigerant components is to suppress an increase of the carbenes present in at least one of the discharge region and the sliding region.

[0168] (Technology 7) The method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to Technology 6, wherein the molar fraction of the carbene present in at least one of the discharge region and the sliding region is set to 0.35 or less.

[0169] (Technology 8) The method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to Technology 7, wherein an increase in the carbene is suppressed by controlling a temperature in at least one of the discharge region and the sliding region to 700 K or less.

[0170] (Technology 9) The method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to Technology 7 or Technology 8, wherein the pressure in at least one of the discharge region and the sliding region is controlled from a high-temperature, high-pressure state to 2 MPa or less, thereby suppressing an increase in the carbene.

[0171] (Technology 10) A method for capturing carbene present in a refrigeration cycle, the method comprising: a refrigeration cycle composition; the composition for a refrigeration cycle containing a carbene scavenger having a higher reactivity with the carbene than substances other than the carbene present in the refrigeration cycle; and the carbene scavenger reacting with the carbene present in the refrigeration cycle to capture the carbene present in the refrigeration cycle.

[0172] (Technology 11) A composition for a refrigeration cycle, comprising a carbene scavenger that is more reactive with the carbene than with substances other than the carbene.

[0173] (Technology 12) The composition for a refrigeration cycle according to Technology 11, wherein the carbene scavenger is a singlet ground state molecule containing π electrons or an unshared electron pair.

[0174] (Technology 13) The composition for a refrigeration cycle according to Technology 11 or Technology 12, further comprising an ethylene-based fluoroolefin.

[0175] (Technology 14) The composition for a refrigeration cycle according to Technology 13, wherein the ethylene-based fluoroolefin is 1,1,2-trifluoroethylene, trans-1,2-difluoroethylene, cis-1,2-difluoroethylene, 1,1-difluoroethylene, tetrafluoroethylene, or monofluoroethylene.

[0176] (Technology 15) The composition for a refrigeration cycle according to any one of Technology 11 to Technology 14, further comprising difluoromethane.

[0177] (Technology 16) The composition for a refrigeration cycle according to any one of Technology 11 to Technology 15, further comprising a saturated hydrocarbon.

[0178] (Technology 17) The composition for a refrigeration cycle according to Technology 16, wherein the saturated hydrocarbon includes n-propane.

[0179] (Technology 18) The composition for a refrigeration cycle according to any one of Technology 11 to Technology 17, which contains a haloalkane having 1 or 2 carbon atoms.

[0180] (Technology 19) A refrigeration cycle device comprising the composition for a refrigeration cycle according to any one of Technology 11 to Technology 18.

[0181] The present invention can be suitably used in the field of working fluids used in refrigeration cycles, and can also be suitably used widely in the field of refrigeration cycle systems such as air conditioners, refrigerators (for home and commercial use), dehumidifiers, showcases, ice makers, heat pump water heaters, heat pump washer-dryers, and vending machines.

[0182] DESCRIPTION OF SYMBOLS 10: Air conditioner (refrigeration cycle system) 11: Indoor unit 12: Outdoor unit 13: Piping 14: Heat exchanger 15: Heat exchanger 16: Compressor 17: Pressure reducing device 18: Four-way valve 20: Refrigerator (refrigeration cycle system) 21: Compressor 22: Condenser 23: Pressure reducing device 24: Evaporator 25: Piping 31: Carbene 32: Carbene scavenger (carbene direct reaction type) 33: Singlet ground state molecule 34: Carbene scavenger (catalytic type) 161: Sealed container 162: Motor section 163: Compression mechanism section 163A: First compression mechanism section 163B: Second compression mechanism section 164: Stator 165: Rotor 166: Shaft 167: Main bearing 168: Auxiliary bearing 169A: First piston 169B: Second piston 170: Accumulator 171A: First suction pipe 171B: Second suction pipe 172A: First compression chamber 172B: Second compression chamber 173: Airtight power supply terminal 174: Wiring 201: Discharge area 201a: Reaction intermediate retention area 201A: Discharge area 201B: Discharge area 202A: Sliding area 202B: Sliding area 202C: Sliding area

Claims

1. In a refrigeration cycle in which a working fluid for a refrigeration cycle containing a refrigerant component that causes a disproportionation reaction circulates, This method is characterized by using a carbene scavenger that has a higher reactivity with the carbene than other substances present in the refrigeration cycle, thereby capturing the carbene generated by the disproportionation reaction of the refrigerant components and suppressing the disproportionation reaction of the refrigerant components. A method for suppressing the disproportionation reaction of the working fluid in a refrigeration cycle.

2. The aforementioned carbene is CF 2 CHF, and C n F 2 (where n is an integer of 2, 3, or 4) including at least one selected from the group, A method for suppressing the disproportionation reaction of a working fluid for a refrigeration cycle according to claim 1.

3. In a refrigeration cycle in which a working medium for a refrigeration cycle containing a refrigerant component that causes a disproportionation reaction is circulated, The carbene scavenger, which has a higher reactivity with the carbene than other substances present in the refrigeration cycle, captures the carbene generated by the disproportionation reaction of the refrigerant components and suppresses the disproportionation reaction of the refrigerant components. The capture of the carbene includes the reaction of the carbene scavenger with the carbene to convert the carbene into a singlet ground state molecule that does not have unpaired electrons. A method for suppressing the disproportionation reaction of the working fluid in a refrigeration cycle.

4. In a refrigeration cycle in which a working medium for a refrigeration cycle containing a refrigerant component that causes a disproportionation reaction is circulated, The carbene scavenger, which has a higher reactivity with the carbene than other substances present in the refrigeration cycle, captures the carbene generated by the disproportionation reaction of the refrigerant components and suppresses the disproportionation reaction of the refrigerant components. The capture of the carbene includes the reaction of the carbene scavenger with the carbene, causing the carbene scavenger to act as a catalyst to convert two or more of the carbenes into singlet ground state molecules that do not have unpaired electrons. A method for suppressing the disproportionation reaction of the working fluid in a refrigeration cycle.

5. Suppressing the disproportionation reaction of the refrigerant components suppresses the increase of the carbene within the refrigeration cycle. The suppression of the increase in the carbene includes lowering the concentration below a predetermined upper limit of the carbene, or making the carbene concentration substantially zero. A method for suppressing disproportionation reactions in a working fluid for a refrigeration cycle according to claim 1 or 2.

6. The aforementioned refrigeration cycle includes a compressor, Inside the compressor, Discharge region where discharge can occur, A sliding region having a sliding portion in which multiple sliding members slide while in contact with each other's sliding surfaces, Includes, Suppressing the disproportionation reaction of the refrigerant component means suppressing the increase of the carbene present in at least one of the discharge region and the sliding region. A method for suppressing disproportionation reactions in a working fluid for a refrigeration cycle according to claim 1 or 2.

7. In a refrigeration cycle in which a working medium for a refrigeration cycle containing a refrigerant component that causes a disproportionation reaction is circulated, The carbene scavenger, which has a higher reactivity with the carbene than other substances present in the refrigeration cycle, captures the carbene generated by the disproportionation reaction of the refrigerant components and suppresses the disproportionation reaction of the refrigerant components. The aforementioned refrigeration cycle includes a compressor, Inside the compressor, Discharge region where discharge can occur, A sliding region having a sliding portion in which multiple sliding members slide while in contact with each other's sliding surfaces, Includes, Suppressing the disproportionation reaction of the refrigerant component means suppressing the increase of the carbene present in at least one of the discharge region and the sliding region. The mole fraction of the carbene present in at least one of the discharge region and the sliding region is set to 0.35 or less. A method for suppressing the disproportionation reaction of the working fluid in a refrigeration cycle.

8. By controlling the temperature in at least one of the discharge region and the sliding region to 700K or less, the increase in carbene is suppressed. A method for suppressing the disproportionation reaction of a working fluid for a refrigeration cycle according to claim 7.

9. By controlling the pressure in at least one of the discharge region and the sliding region from a high-temperature, high-pressure state to 2 MPa or less, the increase in carbene is suppressed. A method for suppressing the disproportionation reaction of a working fluid for a refrigeration cycle according to claim 7.

10. In a refrigeration cycle containing a composition for refrigeration cycles, The refrigeration cycle composition contains a carbene scavenger that has a higher reactivity with the carbene than other substances present in the refrigeration cycle, The carbene scavenger reacts with the carbene present in the refrigeration cycle, A method characterized by capturing carbenes present in the aforementioned refrigeration cycle, A method for capturing carbenes present in a refrigeration cycle.

11. The refrigeration cycle contains a carbene scavenger that is more reactive with the carbene than other substances present in the refrigeration cycle, Composition for refrigeration cycles.

12. A carbene scavenger that has a higher reactivity with the carbene than other substances present in the refrigeration cycle, The carbene scavenger is a singlet ground state molecule containing π electrons or a lone pair of electrons. Composition for refrigeration cycles.

13. Further containing ethylene-based fluoroolefins, The composition for a refrigeration cycle according to claim 11.