Pentaerythritol ester lubricating oil, working fluid composition and application thereof

Abstract

The invention belongs to the technical field of refrigerating machine oil, and particularly relates to pentaerythritol ester lubricating oil, a working fluid composition and application of the pentaerythritol ester lubricating oil, the pentaerythritol ester lubricating oil comprises pentaerythritol ester, and the pentaerythritol ester is synthesized by pentaerythritol, C4-C10 monobasic fatty acid and C5-C18 unsaturated acid. A working fluid composition formed by the prepared pentaerythritol ester lubricating oil and R410A, R32 or R454B has an oil-rich layer and a lean oil layer at-15 DEG C to-30 DEG C. In the process of heating to 30 DEG C, the mass ratio variation of the lubricating oil in the oil-rich layer is less than or equal to 0.5 wt% / DEG C, and the lubricating oil in the lean oil layer is less than or equal to 0.5 wt% / DEG C. Therefore, the phenomena of oil injection and a large number of bubbles of the compressor in the low-temperature heating starting state of the air conditioner are avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of refrigeration oil, and in particular relates to a pentaerythritol ester lubricating oil, a working fluid composition and applications thereof. Background Art

[0002] In low-temperature environments between -15°C and -30°C, during the low-temperature heating startup of the air conditioner, the temperature inside the compressor can rapidly rise to 40°C to 50°C. This can cause a large amount of lubricating oil to spray out, accompanied by the formation of numerous bubbles within the compressor. This can lead to oil starvation in the initial startup phase (1-6 minutes after startup). This can cause wear and tear in the compressor due to oil starvation, shortening its lifespan.

[0003] Common solutions include increasing heat pipe insulation, accelerating compressor oil return, and reducing the power consumption during the initial startup phase of the air conditioner to cool first and then heat. However, these methods all have drawbacks. Increasing heat pipe insulation increases energy consumption, accelerating compressor oil return only shortens the duration of oil shortage, and reducing the power consumption during the initial startup phase of the air conditioner can prolong the initial cooling air flow during low-temperature heating, reducing the user experience.

[0004] Some undisclosed lubricants incompatible with R32 refrigerant can alleviate the oil shortage problem during the initial low-temperature heating startup of air conditioners by minimizing the oil ratio fluctuation in the oil-rich layer. However, a new problem arises: certain lubricants suitable for HFC systems with R32 refrigerant are not suitable for HFO systems such as R454B. Even with the denser HFC system R410A, their effectiveness is reduced. Other lubricants suitable for R454B refrigerant are not suitable for R32 or R410A refrigerants. Different lubricants must be developed and produced for different refrigerant systems, significantly increasing production costs.

[0005] Therefore, a pentaerythritol ester lubricant, a working fluid composition and its application are proposed, so that the lubricant can be adapted to R410A, R32 and R454B refrigerants at the same time, so that it is particularly important to prevent oil injection and a large number of bubbles in the compressor during the initial low-temperature heating start-up of the air conditioner. Summary of the Invention

[0006] The present invention aims to address at least one of the technical problems existing in the aforementioned prior art. To this end, the present invention provides a pentaerythritol ester lubricant, a working fluid composition, and their use. The method enables the lubricant to be compatible with R410A, R32, and R454B refrigerants, and the working fluid composition prevents oil injection and excessive bubbling in the compressor during the initial low-temperature heating startup of an air conditioner.

[0007] The inventive concept of the present invention is that when an air conditioner is started in low-temperature heating mode, the temperature inside the compressor rises rapidly, causing the proportion of lubricating oil in the oil-rich layer in the compressor to fluctuate significantly, inducing flash evaporation to produce a large number of bubbles, which in turn causes lubricating oil to spray out of the compressor, resulting in oil shortage. Therefore, the synthesis method and raw materials are adjusted to synthesize a lubricating oil in which the proportion of lubricating oil in the oil-rich layer of the stratified mixture formed with R410A, R32, or R454B decreases more slowly during temperature increase. This ensures that the working fluid composition formed by the lubricating oil and R410A, R32, or R454B, respectively, does not spray oil or produce a large number of bubbles in the compressor during the low-temperature heating mode of the air conditioner.

[0008] A first aspect of the present invention provides a pentaerythritol ester lubricating oil.

[0009] Specifically, a pentaerythritol ester lubricant comprises pentaerythritol ester, which is synthesized from pentaerythritol, C4-C10 monobasic fatty acid, and C5-C18 unsaturated acid.

[0010] The pentaerythritol ester accounts for more than 95 wt % of the pentaerythritol ester lubricating oil.

[0011] Compared with the prior art, the beneficial effects of the pentaerythritol ester lubricant provided in the first aspect are as follows: the working fluid composition formed by the pentaerythritol ester lubricant and R410A, R32 or R454B respectively has an oil-rich layer and an oil-poor layer at -15°C to -30°C. During the process of heating to 30°C, the change in the mass proportion of the lubricating oil in the oil-rich layer is less than or equal to 0.5wt% / °C, further preventing oil injection and a large number of bubbles from appearing in the compressor when the air conditioner is started in low-temperature heating mode.

[0012] Preferably, the pentaerythritol ester is synthesized from pentaerythritol, isobutyric acid, isononanoic acid, and oleic acid.

[0013] Preferably, based on the amount of substance, the pentaerythritol ester is synthesized from 10 parts of pentaerythritol, 4-6 parts of isobutyric acid, 2-3 parts of isononanoic acid, and 2-3 parts of oleic acid; further preferably, the pentaerythritol ester is synthesized from 10 parts of pentaerythritol, 4.5-5.5 parts of isobutyric acid, 2-3 parts of isononanoic acid, and 2-3 parts of oleic acid; further preferably, the amount of pentaerythritol is equal to the sum of the amount of the isobutyric acid, the isononanoic acid, and the oleic acid.

[0014] Preferably, the synthesis method of the pentaerythritol ester comprises the following steps: (1) 10 parts of pentaerythritol and 2-3 parts of oleic acid are mixed and heated under inorganic acid conditions to produce a first intermediate compound; (2) The first intermediate compound is mixed with 2-3 parts of isononanoic acid and heated under inorganic acid conditions to react to obtain a second intermediate compound; (3) The second intermediate compound is mixed with 4-6 parts of isobutyric acid, heated under the condition of an inorganic acid for reaction, and then purified to obtain the pentaerythritol ester.

[0015] Preferably, the inorganic acid comprises SO4 2- / M x O y Type solid acid catalyst; further preferably, the solid acid catalyst includes SO4 2- / Al2O3 or SO4 2- / TiO2 type solid acid catalyst.

[0016] Preferably, the addition amount of the solid acid catalyst is 0.1-0.5 wt % of the total mass of the substrate in the reaction system.

[0017] Preferably, the temperature of the heating reaction is 200-240° C., and the reaction time is 6-24 hours; further preferably, the atmosphere of the heating reaction is a nitrogen atmosphere.

[0018] Preferably, in step (3), the purification step includes at least one of adsorption filtration, alkali washing, water washing, and reduced steaming; preferably, the adsorption filtration includes adsorption filtration at 80-100°C for 3-5 times, and the reduced steaming temperature is 180°C-250°C.

[0019] Preferably, the acid value of the pentaerythritol ester lubricant oil is less than or equal to 0.05 mgKOH / g; further preferably, the acid value of the pentaerythritol ester lubricant oil is less than or equal to 0.02 mgKOH / g.

[0020] Preferably, the water content of the pentaerythritol ester lubricant is less than or equal to 100 ppm; further preferably, the water content of the pentaerythritol ester lubricant is less than or equal to 50 ppm.

[0021] Preferably, the pentaerythritol ester lubricant further comprises an antioxidant, an acid scavenger and an anti-wear agent, wherein the antioxidant comprises a phenolic compound, the acid scavenger comprises an epoxy compound, and the anti-wear agent comprises a phosphite compound.

[0022] Preferably, the antioxidant comprises a phenolic antioxidant, the acid scavenger comprises octyl glycidyl ether, and the anti-wear agent comprises tris(2,4-di-tert-butylphenyl)phosphite; preferably, the phenolic antioxidant comprises BASF Irganox L101, and the anti-wear agent comprises BASF Irgafos 168. The CAS number of tris(2,4-di-tert-butylphenyl)phosphite is 31570-04-4.

[0023] Preferably, the working fluid composition formed by the pentaerythritol ester lubricant and the R410A, R32 or R454B refrigerant has a dissolution viscosity greater than or equal to 1.2 cP at a temperature of 80° C. and an absolute pressure of 2.25 MPa.

[0024] Preferably, the mixture (working fluid composition) formed by mixing the pentaerythritol ester lubricant with R410A, R32 or R454B respectively has an oil-rich layer and an oil-poor layer at -15°C to -30°C. During the process of heating from -15°C to 30°C, the change in the mass proportion of the pentaerythritol ester lubricant in the oil-rich layer is less than or equal to 0.5wt% / °C and greater than or equal to 0.001wt% / °C; further preferably, during the process of heating from -15°C to 30°C, the instantaneous change in the mass proportion of the pentaerythritol ester lubricant in the oil-rich layer is less than or equal to 0.4wt% / °C and greater than or equal to 0.001wt% / °C.

[0025] It should be noted that the change in the mass percentage of pentaerythritol ester lubricant is the absolute value of the change in the mass percentage of lubricant in the oil-rich layer within a certain temperature increase range, divided by the temperature change, expressed in "wt% / °C." It can also be expressed as the absolute value of the derivative of the solubility curve corresponding to the oil-rich layer in the two-layer separation temperature curve of pentaerythritol ester lubricant and refrigerant, with temperature as the horizontal axis. When the temperature increase range approaches zero, the instantaneous change in the mass percentage of pentaerythritol ester lubricant at that temperature is recorded, and the value is equal to the absolute value of the slope of the temperature point on the solubility curve corresponding to the oil-rich layer in the two-layer separation temperature curve, with temperature as the horizontal axis.

[0026] It should be noted that the second-layer separation temperature curve is measured and mapped with reference to SH / T 0699-2000 "Test method for compatibility of refrigeration oil and refrigerant".

[0027] In the mixture, the content of the pentaerythritol ester lubricant is 15-30 wt %.

[0028] A second aspect of the present invention provides a working fluid composition.

[0029] A working fluid composition comprises any one of the pentaerythritol ester lubricating oils and at least one refrigerant selected from the group consisting of R410A, R32, and R454B.

[0030] Preferably, the working fluid composition has an oil-rich layer and an oil-poor layer at -15°C to -30°C, and during the process of heating from -15°C to 30°C, the change in the mass proportion of the pentaerythritol ester lubricant in the oil-rich layer is less than or equal to 0.5wt% / °C; further preferably, the working fluid composition has an oil-rich layer and an oil-poor layer at -15°C to -30°C, and during the process of heating from -15°C to 30°C, the change in the mass proportion of the pentaerythritol ester lubricant in the oil-rich layer is less than or equal to 0.4wt% / °C.

[0031] Preferably, in the working fluid composition, the content of the pentaerythritol ester lubricant is 15-30 wt %.

[0032] A third aspect of the present invention provides a use of any one of the pentaerythritol ester lubricants in an air-conditioning system using R410A, R32 or R454B refrigerant.

[0033] Preferably, the air-conditioning system includes a cooling and heating dual-purpose system, and the compressor used includes a rotary compressor or a scroll compressor.

[0034] Compared with the prior art, the present invention has the following beneficial effects: The working fluid composition formed by pentaerythritol ester lubricant and R410A, R32 or R454B respectively has an oil-rich layer and an oil-poor layer at -15°C to -30°C. During the process of heating to 30°C, the change in the mass proportion of lubricating oil in the oil-rich layer is less than or equal to 0.5wt% / °C, so that oil injection and a large number of bubbles in the compressor will not occur when the air conditioner is started in low-temperature heating mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a two-layer separation curve diagram of the working fluid composition formed by the pentaerythritol ester lubricant in Example 1 and R410A, R32 and R454B respectively when the mass proportion of the pentaerythritol ester lubricant is greater than 40 wt %. DETAILED DESCRIPTION

[0036] In order to make the technical solution of the present invention more clearly understood by those skilled in the art, the following examples are given for illustration. It should be noted that the following examples do not limit the scope of protection claimed by the present invention.

[0037] Unless otherwise specified, the raw materials, reagents, or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0038] The test method for the dissolution viscosity of the present invention is as follows: 100 g of pentaerythritol ester lubricating oil is added to a 250 mL autoclave equipped with an online viscometer. The entire container is first devacuated, and then 100 mL of refrigerant (R410A, R32, or R454B) is injected at low temperature to form a fluid mixture. The dissolution viscosity is then measured at 80°C and 2.25 MPa.

[0039] The low-temperature heating start-up performance test method for air conditioners in this invention involves adding equal amounts of pentaerythritol ester lubricant to the twin-bar compressors of 3P heating and cooling air conditioners using R410A, R32, or R454B refrigerants, respectively, for identical indoor units. After adding the corresponding amounts of refrigerant, the air conditioner is started at -15°C with heating enabled. Window windows (including upper and lower windows) are installed at the same height on the upper and lower bars of each twin-bar compressor. The maximum oil level drop percentage and the maximum bubble thickness are recorded. The maximum oil level drop percentage is calculated by dividing the maximum oil level drop height at the window by the window height × 100%. Note that the oil level is just below the upper window before startup.

[0040] The change in the mass percentage of pentaerythritol ester lubricant in the oil-rich layer is calculated as the absolute value of the change in the mass percentage of lubricant (oil ratio) in the oil-rich layer over the temperature range of -15°C to 30°C, divided by the temperature change. The unit is "wt% / °C." Alternatively, it can be expressed as the absolute value of the derivative of the solubility curve segment of the pentaerythritol ester lubricant and refrigerant separation curve, with temperature as the horizontal axis. When the temperature range approaches zero, the instantaneous change in the mass percentage of pentaerythritol ester lubricant at that temperature is recorded. This value is equal to the absolute value of the slope of the solubility curve segment of the oil-rich layer, with temperature as the horizontal axis. It should be noted that the separation temperature curve is measured and drawn in accordance with SH / T 0699-2000, "Test Method for Compatibility of Refrigerator Oils and Refrigerants." Example 1

[0041] In Example 1, the pentaerythritol ester lubricant oil was synthesized from 10 mol (1361 g) of pentaerythritol, 5 mol (440 g) of isobutyric acid, 2.5 mol (395 g) of isononanoic acid, and 2.5 mol (706 g) of oleic acid (CAS: 112-80-1). The preparation steps are as follows: (1) 10 mol (1361 g) of pentaerythritol was mixed with 2.5 mol (706 g) of oleic acid in 2.1 g of SO4 2- / Al2O3 type solid acid catalyst under nitrogen atmosphere, heating to 220 ° C for esterification reaction for 12 hours to obtain a first intermediate compound; (2) The first intermediate compound was mixed with 2.5 mol (395 g) of isononanoic acid and added to 2.1 g of SO4 2- / Al2O3 type solid acid catalyst under nitrogen atmosphere, heating to 220 ° C for esterification reaction for 12 hours to obtain a second intermediate compound; (3) The second intermediate compound was mixed with 5 mol (440 g) of isobutyric acid and 2.1 g of SO4 2- The reaction was carried out at 220°C in a nitrogen atmosphere under the condition of a / Al2O3 solid acid catalyst for esterification for 12 hours, followed by adsorption filtration at 80°C for 5 times, alkali washing, water washing, and water removal by distillation, and finally purification to obtain pentaerythritol ester lubricating oil.

[0042] After testing, the pentaerythritol ester lubricant of Example 1 has a solubility viscosity of 1.465 cP at 80°C and 2.25 MPa, and a kinematic viscosity of 43.65 mm at 40°C. 2 / s, acid value 0.01mgKOH / g, moisture content less than 50ppm.

[0043] After supplementation with 0.2 wt % antioxidant BASF Irganox L101, 0.3 wt % acid scavenger octyl glycidyl ether (CAS No. 2461-15-6), and 0.3 wt % anti-wear agent BASF Irgafos 168, the low-temperature heating startup performance (maximum percentage drop in the oil level in the upper and lower windows, maximum oil bubble thickness) of air conditioners composed of refrigeration oil lubricants composed of the pentaerythritol ester lubricant of Example 1 and R410A, R32, or R454B were tested. The change in the mass percentage of the pentaerythritol ester lubricant in the oil-rich layer during the temperature increase from -15°C to 30°C (wt % / °C) was experimentally measured and recorded in Table 1.

[0044] Figure 1 This is a two-layer separation curve diagram of a working fluid composition composed of pentaerythritol ester lubricant and R410A, R32, and R454B, respectively, in Example 1, when the mass percentage of the pentaerythritol ester lubricant is 40 wt % or greater. The abscissa represents temperature (°C), and the ordinate represents the mass percentage of the pentaerythritol ester lubricant. The unit is simplified from "wt %" to "%." This figure can also be viewed as the corresponding curve segment of the solubility of the oil-rich layer in the two-layer separation temperature curve of the pentaerythritol ester lubricant and refrigerant with temperature as the abscissa. The area above the curve represents the single-phase region. The working fluid composition composed of pentaerythritol ester lubricant and R410A has a lubricant content of 46.7 wt% in the oil-rich layer at -15°C and 45 wt% at 30°C. The average change in the mass proportion of the pentaerythritol ester lubricant in the oil-rich layer during the temperature increase from -15°C to 30°C is (46.7 wt% - 45 wt%) / (|-15°C - 30°C|) = 0.0378 wt% / °C. Furthermore, the instantaneous change in the mass proportion of the pentaerythritol ester lubricant in the oil-rich layer during the temperature increase from -15°C to 30°C is less than 0.4 wt% / °C. The working fluid composition composed of pentaerythritol ester lubricant and R454B has a lubricant content of 52.5 wt% in the oil-rich layer at -15°C and 46.7 wt% at 30°C. The average change in the mass fraction of the pentaerythritol ester lubricant in the oil-rich layer during the temperature increase from -15°C to 30°C is (52.5 wt% - 46.7 wt%) / (|-15°C - 30°C|) = 0.129 wt% / °C. Furthermore, the instantaneous change in the mass fraction of the pentaerythritol ester lubricant in the oil-rich layer during the temperature increase from -15°C to 30°C is less than 0.4 wt% / °C. The working fluid composition composed of pentaerythritol ester lubricant and R32 has a lubricant proportion of 60wt% in the oil-rich layer at -15℃ and 53wt% at -30℃. The average change in the mass proportion of pentaerythritol ester lubricant in the oil-rich layer during the temperature increase from -15℃ to 30℃ is (60wt%-53wt%) / (|-15℃-30℃|)=0.156 wt% / ℃, and the instantaneous change in the mass proportion of pentaerythritol ester lubricant in the oil-rich layer during the temperature increase from -15℃ to 30℃ is less than 0.4wt% / ℃.

[0045] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that oleic acid is replaced by an equimolar amount of isononanoic acid.

[0046] After supplementation with 0.2 wt % of the antioxidant BASF Irganox L101, 0.3 wt % of the acid scavenger octyl glycidyl ether, and 0.3 wt % of the anti-wear agent BASF Irgafos 168, the low-temperature heating startup performance (maximum percentage drop in the oil level in the upper and lower windows, maximum oil bubble thickness) of air conditioners composed of refrigeration oil lubricants composed of the pentaerythritol ester lubricant from Example 1 and R410A, R32, or R454B were tested. The change in the mass percentage of the pentaerythritol ester lubricant in the oil-rich layer during the temperature increase from -15°C to 30°C (wt % / °C) was experimentally measured and recorded in Table 1.

[0047] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that oleic acid is replaced by an equal molar amount of octadecanoic acid.

[0048] After supplementation with 0.2 wt % of the antioxidant BASF Irganox L101, 0.3 wt % of the acid scavenger octyl glycidyl ether, and 0.3 wt % of the anti-wear agent BASF Irgafos 168, the low-temperature heating startup performance (maximum percentage drop in the oil level in the upper and lower windows, maximum oil bubble thickness) of air conditioners composed of refrigeration oil lubricants composed of the pentaerythritol ester lubricant from Example 1 and R410A, R32, or R454B were tested. The change in the mass percentage of the pentaerythritol ester lubricant in the oil-rich layer during the temperature increase from -15°C to 30°C (wt % / °C) was experimentally measured and recorded in Table 1.

[0049] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that step (1) and step (3) of Example 1 are swapped.

[0050] After supplementation with 0.2 wt % of the antioxidant BASF Irganox L101, 0.3 wt % of the acid scavenger octyl glycidyl ether, and 0.3 wt % of the anti-wear agent BASF Irgafos 168, the low-temperature heating startup performance (maximum percentage drop in the oil level in the upper and lower windows, maximum oil bubble thickness) of air conditioners composed of refrigeration oil lubricants composed of the pentaerythritol ester lubricant from Example 1 and R410A, R32, or R454B were tested. The change in the mass percentage of the pentaerythritol ester lubricant in the oil-rich layer during the temperature increase from -15°C to 30°C (wt % / °C) was experimentally measured and recorded in Table 1.

[0051] The results of Comparative Example 3 are quite different from those of Example 1. After liquid phase analysis, it is found that the mixtures generated by Example 1 and Comparative Example 3 are quite different. It can be determined that the generated mixtures are quite different.

[0052] Maximum percentage of oil level drop in upper window Maximum percentage of oil level drop in lower window Maximum oil bubble thickness Change in the mass percentage of pentaerythritol ester lubricant in oil-rich layers (wt% / ℃) Example 1 R410A 14% 0 0 0.0378 Example 1 R32 9% 0 0 0.156 Example 1 R454B 16% 0 0 0.129 Comparative Example 1 R410A 24% 0 0 0.373 Comparative Example 1 R32 16% 0 0 0.251 Comparative Example 1 R454B 100% 24% 4mm 0.632 Comparative Example 2 R410A 100% 8% 3mm 0.541 Comparative Example 2 R32 100% 21% 7mm 0.615 Comparative Example 2 R454B 26% 0 0 0.382 Comparative Example 3 R410A 100% 12% 3mm 0.571 Comparative Example 3 R32 100% 26% 5mm 0.584 Comparative Example 3 R454B 16% 0 0 0.132 As can be seen from Table 1, only the pentaerythritol ester lubricant of Example 1 can simultaneously form a working fluid composition with R410A, R32, and R454B, respectively, so that the phenomenon of "no oil injection and large amounts of bubbles in the compressor during low-temperature heating startup of the air conditioner" is avoided. Example 2

[0053] The difference between Example 2 and Example 1 is that the amount of raw materials is different: pentaerythritol ester lubricant is synthesized from 10 mol pentaerythritol, 5 mol isobutyric acid, 2 mol isononanoic acid, and 3 mol oleic acid, and the other components and steps are the same.

[0054] The effects of the prepared pentaerythritol ester lubricating oil and working fluid composition are similar to those of Example 1.

Claims

1. A pentaerythritol ester lubricating oil, characterized in that: The pentaerythritol ester lubricating oil comprises pentaerythritol ester, and the pentaerythritol ester is synthesized from pentaerythritol, C4-C10 monobasic fatty acid and C5-C18 unsaturated acid.

2. The pentaerythritol ester lubricating oil according to claim 1, characterized in that The pentaerythritol ester is synthesized from 10 parts of pentaerythritol, 4-6 parts of isobutyric acid, 2-3 parts of isononanoic acid, and 2-3 parts of oleic acid, based on the amount of the substance.

3. The pentaerythritol ester lubricating oil according to claim 2, characterized in that: The synthetic method of the pentaerythritol ester comprises the following steps: (1) 10 parts of pentaerythritol and 2-3 parts of oleic acid are mixed and heated under inorganic acid conditions to produce a first intermediate compound; (2) mixing the first intermediate compound with 2-3 parts of isononanoic acid, and heating them under inorganic acid conditions to react to obtain a second intermediate compound; (3) The second intermediate compound is mixed with 4-6 parts of isobutyric acid, heated under inorganic acid conditions for reaction, and then purified to obtain the pentaerythritol ester.

4. The pentaerythritol ester lubricating oil according to claim 3, characterized in that The temperature of the heating reaction is 200-240° C., and the reaction time is 6-24 hours.

5. The pentaerythritol ester lubricating oil according to claim 3, characterized in that: In step (3), the purification includes at least one of adsorption filtration, alkali washing, water washing, and reduced steam.

6. The pentaerythritol ester lubricating oil according to claim 1, characterized in that The pentaerythritol ester lubricant has a dissolving viscosity greater than or equal to 1.2 cP in R410A, R32 or R454B refrigerant at a temperature of 80° C., an absolute pressure of 2.25 MPa and a content of 25 wt %.

7. The pentaerythritol ester lubricating oil according to claim 1, characterized in that The mixture of the pentaerythritol ester lubricant and R410A, R32 or R454B refrigerant has an oil-rich layer and an oil-poor layer at -15°C to -30°C. During the process of heating from -15°C to 30°C, the change in the mass proportion of the pentaerythritol ester lubricant in the oil-rich layer is less than or equal to 0.5wt% / °C.

8. The pentaerythritol ester lubricating oil according to claim 1, characterized in that The pentaerythritol ester lubricant also includes an antioxidant, an acid scavenger and an anti-wear agent; the antioxidant includes a phenolic compound, the acid scavenger includes an epoxy compound, and the anti-wear agent includes a phosphite compound.

9. A working fluid composition, comprising the pentaerythritol ester lubricant oil according to any one of claims 1 to 8, and at least one refrigerant selected from the group consisting of R410A, R32, and R454B.

10. Use of the pentaerythritol ester lubricant according to any one of claims 1 to 8 in an air conditioning system using R410A, R32 or R454B refrigerant.

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