METHOD FOR IMPROVING THE STABILITY OF A COMPOSITION CONTAINING A HYDROFLUOROLEFIN

Description

Technical Field

[0001] The present invention relates to a method for improving the stability of a composition comprising a hydrofluoroolefin (HFO) .Background Art

[0002] Hydrofluoroolefins (HFOs) of e.g. the formulae CF 3 (CX 2 ) n CF=CH 2 and CF 3 (CX 2 ) n CH=CHF are useful compounds as, for example, various functional materials, solvents, refrigerants, foaming agents, monomers for functional polymers or starting materials of such monomers. For example, HFOs are used as monomers for modifying ethylene-tetrafluoroethylene copolymers.

[0003] Of the above HFO compounds, CF 3 CF=CH 2 (HFO-1234yf), CF 3 CH=CHF (E- / Z-) (HFO-1234ze), and CF 3 CF=CHF (E- / Z-) (HFO-1225ye) have recently gained attention as they offer promising prospects as refrigerants with low global warming potential (GWP).

[0004] As an example of methods for producing the above HFO compounds, a method has been reported in which a chlorine-containing alkane or chlorine-containing alkene starting material having the same number of carbon atoms as that of a target fluoroolefin is reacted with a fluorinating agent, such as an anhydrous hydrogen fluoride, in the presence of a catalyst (see, for example, US-A-2011 / 0160497).

[0005] Examples of compositions used as heat transfer medium, foaming agent or propellant and comprising a HFO compound, a chlorine-containing compound and, in some cases, water and / or an HFC-compound are disclosed in e.g. WO 2014 / 150889, US-A_2007 / 112227, WO 2014 / 102478, US-A-2012 / 203037, US-A_2006 / 185972, WO 2009 / 137658, WO 2012 / 067980 and US-A-2015 / 008357.

[0006] However, HFO compounds, which contain a double bond, have low stability, compared with e.g. hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs), which have been used as heat transfer media (refrigerants). Therefore, for example, an HFO compound when used as a heat transfer medium for an air-conditioning system may react with entrained air or oxygen, may react inside the air-conditioning system with a part or parts that are in contact with the heat transfer medium, or may result in decomposition of the HFO compound itself, depending on the operating conditions. In these cases, the performance of the air-conditioning system problematically decreases; thus, an improvement in the stability of the HFO compound is necessary.

[0007] Although the performance of air-conditioning systems has been improved in accordance with an improvement of the systems, there is a limit to improving the performance with the improvement of the systems, and an attempt has been made to improve, for example, the refrigerating capacity by adding an additive to an HFO compound used as a heat transfer medium.Summary of InventionTechnical Problem

[0008] An object of the present invention is to provide a method for improving the stability of a composition comprising an HFO compound, the composition having excellent stability with decomposition and oxidation of the HFO compound being inhibited, the composition having improved refrigerating capacity when used as a heat transfer medium, compared with the case in which an HFO compound is used alone, and having excellent stability in a heat transfer medium, foaming agent or propellant, a fire extinguisher, and thus can be suitably used in these applications.Solution to Problem

[0009] The present inventors conducted extensive research to achieve the above objects, and found that a composition comprising a specific HFO compound and a specific chlorine-containing compound can achieve the above objects. The present invention has thus been accomplished.

[0010] More specifically, the present invention relates to a method for improving the stability of a composition comprising (i) a HFO compound, (ii) a chlorine-containing compound, (iii) water and (iv) an HFC-compound, wherein (1) the HFO compound is at least one selected from HFO-1234yf, (E- / Z-)HFO-1234ze and (E- / Z-)HFO-1225ye; (2) the chlorine-containing compound is at least one selected from CH 2 =CHCl, CHF=CHCl, CH 2 =CFCl, CF 3 Cl, CH 3 Cl, CF 3 CH 2 Cl, CClF=CHCl and CHF=CCl 2 , (3) the chlorine-containing compound is contained in an amount of 1-500,000 mass ppm, and (4) the water is contained in an amount of ≤ 1000 mass ppm, (5) the HFC compound is at least one selected from HFC-32, HFC-134a, HFC-125, HFC-143a, and HFC-23; and (6) the HFC compound is contained in an amount of ≤ 40 mass% per 100 mass% of the total of the HFO compound and the HFC compound; comprising adding water to the composition so that the water is contained in an amount of ≤ 1000 mass ppm, based on the composition.

[0011] Preferred embodiments of the invention are as defined in the appended dependent claims and / or in the following detailed description.Advantageous Effects of Invention

[0012] The composition of the method of the present invention (also referred to as "the present composition" herein) comprises a specific HFO compound, 1-500,000 mass ppm of a specific chlorine-containing compound, water in an amount of ≤ 1000 mass ppm, and ≤ 40 mass% of a specific HFC compound per 100 mass% of the total of the HFO compound and the HFC compound. Accordingly, the composition has excellent stability with decomposition and oxidation of the HFO compound being inhibited, and additionally, the refrigerating capacity when used as a heat transfer medium is improved, compared with the case in which an HFO compound is used alone. Therefore, the present composition is suitably used as heat transfer medium, foaming agents or propellant.Brief Description of Drawings

[0013] Fig. 1 is a graph showing the results of simulation evaluation performed with respect to the refrigerating capacity of a composition comprising a mixture of HFO-1234yf and CH 2 =CHCl (vinyl chloride) in a car air conditioner (Example 1). In Fig. 1, R1140 refers to vinyl chloride. Fig. 2 is a graph showing the measurement results of the vapor-liquid equilibrium of a composition comprising a mixture of HFO-1234yf and CH 2 =CHCl (vinyl chloride) (Example 2). In Fig. 2, R1140 refers to vinyl chloride. Description of Embodiments

[0014] The present composition comprises at least one HFO compound selected from HFO-1234yf, (E- / Z-)HFO-1234ze, and (E- / Z-)HFO-1225ye; and a chlorine-containing compound, wherein (1) the chlorine-containing compound is at least one selected from CH 2 =CHCl, CHF=CHCl, CH 2 =CFCl, CF 3 Cl, CH 3 Cl, CF 3 CH 2 Cl, CClF=CHCl, and CHF=CCl 2 ; and (2) the chlorine-containing compound is contained in an amount of 1-500,000 mass ppm. The amount of the chlorine-containing compound refers to the amount in the entire composition.

[0015] The numerical range as used in this specification includes its lower limit and upper limit unless the term "<" or ">" is used.

[0016] The present composition comprises a specific HFO compound and a specific chlorine-containing compound, and the amount of the chlorine-containing compound is 1-500,000 mass ppm. Accordingly, the composition has excellent stability with decomposition and oxidation of the HFO compound being inhibited, and additionally, the refrigerating capacity when used as a heat transfer medium is improved, compared with the case in which an HFO compound is used alone. Therefore, the present composition is suitably used as heat transfer medium, foaming agent or propellant.

[0017] The present composition uses at least one HFO compound selected from HFO-1234yf, (E- / Z-)HFO-1234ze, and (E- / Z-)HFO-1225ye. Here, the "(E- / Z-)" indicates that one or both geometrical isomers, i.e., E- and Z-isomers, are included. Further, the term "HFO" refers to hydrofluoroolefin, and is distinguished from HFC (hydrofluorocarbon) or HCFC (hydrochlorofluorocarbon).

[0018] The above HFO compounds may be obtained by known production methods. Examples of the production methods include a method comprising subjecting fluoroalkane to a dehydrofluorination reaction in the presence of a catalyst (e.g., the method disclosed in JP-A-2012-500182).

[0019] More specifically, if the HFO compound is 2,3,3,3-tetrafluoropropene (HFO-1234yf), then 1,1,1,2,3-pentafluoropropane or 1,1,1,2,2-pentafluoropropane used as a starting material is subjected to a dehydrofluorination reaction in the presence of a catalyst to thus yield HFO-1234yf. If the HFO compound is 1,3,3,3-tetrafluoropropene ((E- / Z-)HFO-1234ze), then 1,1,1,3,3-pentafluoropropane used as a starting material is subjected to a dehydrofluorination reaction in the presence of a catalyst to thus yield (E- / Z-)HFO-1234ze. Further, if the HFO compound is 1,2,3,3,3-pentafluoropropene ((E- / Z-)HFO-1225ye), then 1,1,1,2,3,3-hexafluoropropane or 1,1,1,2,2,3-hexafluoropropane used as a starting material is subjected to hydrogenation, fluorination, and dehydrofluorination sequentially or simultaneously depending on the conditions, in the presence of a catalyst to thus yield (E- / Z-)HFO-1225ye.

[0020] In the above production methods, a chromium catalyst, such as chromium oxide or fluorinated chromium oxide, or other metal catalysts may be used as a catalyst. The reaction may be performed usually at a temperature of 200-500°C. Additionally, the production of the HFO compound may be performed in accordance with known methods.

[0021] The present composition comprises at least one chlorine-containing compound selected from CH 2 =CHCl (vinyl chloride = R1140), CHF=CHCl (HCFC-1131), CH 2 =CFCl (HCFC-1131a), CF 3 Cl (CFC-13), CH 3 Cl (methyl chloride), CF 3 CH 2 Cl (HCFC-133a), CClF=CHCl (HCFC-1121), and CHF=CCl 2 (HCFC-1121a) in an amount of 1-500,000 mass ppm. Of these, as a preferable mode, the present composition comprises at least one chlorine-containing compound selected from CF 3 Cl (CFC-13), CH 3 Cl (methyl chloride), CF 3 CH 2 Cl (HCFC-133a), CClF=CHCl (HCFC-1121), and CHF=CCl 2 (HCFC-1121a) in an amount of 1-500,000 mass ppm.

[0022] Incorporation of the above chlorine-containing compound allows the double bond in the molecule of the HFO compound to be present stably within the composition, thus inhibiting decomposition and oxidation of the HFO compound. This effect is presumably based on the fact that chlorine-containing compounds, which have higher reactivity than HFO compounds, react preferentially with air or oxygen, inhibiting decomposition and oxidation of the HFO compounds.

[0023] Incorporation of the above chlorine-containing compound also improves the refrigerating capacity when used as a heat transfer medium, compared with the case in which an HFO compound is used alone.

[0024] The above chlorine-containing compounds may together form oligomers, such as di- to decamers. Further, the chlorine-containing compound may form such oligomers with a portion of the HFO compound. In these cases, if used as a heat transfer medium, the composition can also improve the slidability within a refrigerator, leading to an improvement of the performance of the refrigerator.

[0025] As in CH 2 =CHCl (vinyl chloride), some of the above chlorine-containing compounds have a characteristic odor (e.g., CH 2 =CHCl has a chloroform odor). Thus, if a chlorine-containing compound with an odor is used, it is also possible to achieve the function of a tracer for detecting the leakage of the composition.

[0026] The chlorine-containing compound may be externally added to the HFO compound. The chlorine-containing compound may also be a compound that is obtained as a by-product in the course of the production process of the HFO compound. If the latter is the case, the amount of the chlorine-containing compound is adjusted to be within 1-500,000 mass ppm by adjusting the amount of the by-product.

[0027] The amount of the chlorine-containing compound in the composition is preferably 10,000-400,000 mass ppm, and more preferably 100,000-300,000 mass ppm.

[0028] If the chlorine-containing compound is at least one selected from CH 2 =CHCl, CHF=CHCl and CH 2 =CFCl, the amount of the chlorine-containing compound is preferably > 6 to 500,000 mass ppm, more preferably 10,000-400,000 mass ppm, and most preferably 100,000-300,000 mass ppm.

[0029] If the chlorine-containing compound is at least one selected from CF 3 Cl, CH 3 Cl, CF 3 CH 2 Cl, CClF=CHCl, and CHF=CCl 2 , the amount of the chlorine-containing compound is preferably 1-10,000 mass ppm.

[0030] Of these chlorine-containing compounds, it is preferable to select a chlorine-containing compound that forms an azeotrope or azeotrope-like mixture with the HFO compound. For example, at least one member of CH 2 =CHCl, CHF=CHCl, and CH 2 =CFCl is suitably used. The use of a combination that forms an azeotrope or azeotrope-like mixture lowers the boiling point, compared with the use of a combination that forms a non-azeotropic mixture, leading to an improvement in the refrigerating capacity when used as a heat transfer medium.

[0031] In addition to the HFO compound and chlorine-containing compound, the present composition comprises an HFC compound, and may comprise a HCFC compound and CO 2 , which are known as existing heat transfer media. The HFC compound is at least one selected from HFC-32, HFC-134a, HFC-125, HFC-143a and HFC-23. These additives may be used together so as to adjust the refrigerating capacity, GWP, and flammability of the present composition, to an extent that the effects of the present invention are not hindered. The amount of these additives is preferably≤ 40 mass% per 100 mass% of the total amount of the HFO compound and these additives.

[0032] For use as a heat transfer medium, the present composition may further comprise at least one lubricant selected from polyalkylene glycols, esters, polyvinyl ethers, and alkylbenzenes. The lubricant can be incorporated in an amount of 10-50 mass% into the composition. However, the amount is not limited to this range, and can vary depending on the specification of the oil tank of a refrigerator. If the amount is within this range, it is unlikely that the stability of the HFO compound will be impaired.

[0033] The present composition further comprises water. The amount of water is ≤ 1000 mass ppm, preferably ≤ 200 mass ppm. When water is contained in an amount of ≤ 1000 mass ppm, the stability of the HFO compound further improves, compared with the case where water is not contained.

[0034] The type of water is not particularly limited, and e.g. purified water, such as distilled water, ion exchange water, filtered water, tap water, and ultrapure water obtained by a commercially available device for generating pure water can be used. Water may possibly be mixed in the process of producing the HFO compound, and the water mixed at this time may be used as water to be incorporated into the composition. As a matter of course, it is possible to once remove the water generated in the production process, and use separately prepared water as water to be incorporated into the composition. The pH of the water is not particularly limited, and is usually 6-8.Examples

[0035] The present invention is described in more detail below with reference to Examples.Example 1

[0036] A simulation evaluation was performed with respect to the refrigerating capacity of a composition comprising a mixture of HFO-1234yf and CH 2 =CHCl (vinyl chloride = R1140) in a car air conditioner. Fig. 1 shows the results.

[0037] Fig. 1 reveals that the coefficient of performance (COP) improves with the addition of vinyl chloride even when it is a small amount added, compared with when HFO-1234yf is used alone. Fig. 1 also reveals that the refrigerating capacity is more excellent when the composition ratio of vinyl chloride is > 0 to 0.55, compared with when HFO-1234yf is used alone, and that the refrigerating capacity is maximal when the vinyl chloride composition ratio is about 0.2.Example 2

[0038] The vapor-liquid equilibrium of a composition comprising a mixture of HFO-1234yf and CH 2 =CHCl (vinyl chloride = R1140) was measured. Fig. 2 shows the results.

[0039] Fig. 2 reveals that when the composition ratio of HFO-1234yf:vinyl chloride is 1:0 to 0.8:0.2, the composition is an azeotropic composition or azeotrope-like composition.

[0040] The results of Figs. 1 and 2 reveal that the composition comprising a mixture of HFO-1234yf and vinyl chloride has an excellent refrigerating capacity at a composition ratio of > 0 to 0.55, and that it is more preferable when the composition ratio of vinyl chloride is 0.1-0.3.

Claims

1. Method for improving the stability of a composition comprising (i) a HFO compound, (ii) a chlorine-containing compound, (iii) water and (iv) an HFC-compound, wherein (1) the HFO compound is at least one selected from HFO-1234yf, (E- / Z-)HFO-1234ze and (E- / Z-)HFO-1225ye; (2) the chlorine-containing compound is at least one selected from CH2=CHCl, CHF=CHCl, CH2=CFCl, CF3Cl, CH3Cl, CF3CH2Cl, CClF=CHCl and CHF=CCl2, (3) the chlorine-containing compound is contained in an amount of 1-500,000 mass ppm, and (4) the water is contained in an amount of ≤ 1000 mass ppm, (5) the HFC compound is at least one selected from HFC-32, HFC-134a, HFC-125, HFC-143a, and HFC-23; and (6) the HFC compound is contained in an amount of ≤ 40 mass% per 100 mass% of the total of the HFO compound and the HFC compound; comprising adding water to the composition so that the water is contained in an amount of ≤ 1000 mass ppm, based on the composition.

2. The method of claim 1, wherein the compound (2) (i) is at least one of CH2=CHCl, CHF=CHCl and CH2=CFCl and (ii) is contained in the composition in an amount of > 6 to 500,000 mass ppm.

3. The method of claim 2, wherein the compound (2) is contained in the composition in an amount of 10,000-400,000 mass ppm, preferably 100,000-300,000 mass ppm.

4. The method of any of claims 1-3, wherein a mixture of compound (1)and the compound (2) is an azeotrope or azeotrope-like mixture.

5. The method of any of claims 1-4, wherein a mixture of compound (1) and at least one compound (2) selected from CH2=CHCl, CHF=CHCl and CH2=CFCl is an azeotrope or azeotrope-like mixture.

6. The method of claim 1, wherein the compound (2) (i) is at least one of CF3Cl, CH3Cl, CF3CH2Cl, CClF=CHCl and CHF=CCl2, and (ii) is contained in the composition in an amount of 1-10,000 mass ppm.

7. The method of any of claims 1-6, wherein the composition further comprises at least one lubricant selected from polyalkylene glycols, esters, polyvinyl ethers, and alkylbenzenes.