Formula and preparation method of efficient environment-friendly low-GWP air conditioner refrigerant

Abstract

The invention relates to the technical field of refrigeration air conditioners, in particular to an efficient environment-friendly low-GWP air conditioner refrigerant formula and a preparation method thereof. The technical problem that an existing low-GWP refrigerant is high in flammability is solved. According to the refrigerant formula prepared by the invention, a high-energy-efficiency natural working medium and an ultralow-GWP fourth-generation refrigerant are taken as main components, a small amount of phosphorus-nitrogen hybrid compound is added as a flame-retardant additive, and the main components are mixed under the conditions of low temperature and high pressure. The flame-retardant additive adopted by the invention has excellent flame retardance, and can capture free radicals and release inert gas to inhibit combustion chain reaction during combustion. Nanoscale dispersion of the additive is realized through a low-temperature ultrasonic-assisted microjet homogenization technology, and the stability of the components is ensured by utilizing online monitoring. According to the refrigerant prepared by the invention, the combustibility is greatly reduced while the refrigeration performance is ensured, and both low GWP and low combustibility are realized.

Description

Technical Field

[0001] This invention relates to the field of refrigeration and air conditioning technology, specifically to a high-efficiency, environmentally friendly, low-GWP air conditioning refrigerant formulation and its preparation method. Background Technology

[0002] With growing concern about global warming, environmental requirements for refrigerants are becoming increasingly stringent. While traditional refrigerants do not deplete the ozone layer, they have high global warming potential (GWP). Two main candidate categories have emerged as alternatives to high GWP refrigerants: natural refrigerants such as hydrocarbons, CO2, and ammonia, and next-generation fluoroolefin refrigerants. Among these, hydrocarbons like R-290 (propane) and R-1270 (propylene), as natural refrigerants, possess excellent thermodynamic properties and extremely low GWP values, but their A3 flammability rating (highly flammable) severely limits their large-scale application in air conditioning systems, necessitating charge quantity restrictions and explosion-proof measures. To address the flammability issue of low GWP refrigerants, industry and academia have proposed various suppression methods, including blending with inert or flame-retardant substances. For example, a common approach is to add a small amount of non-flammable high GWP refrigerant as a "flame suppressant," such as adding R-125 (pentafluoroethane) to a flammable refrigerant to reduce its combustion tendency. R-125 itself has a high GWP of approximately 3500. Adding a small amount can effectively improve the ignition energy of the working fluid mixture and suppress flame propagation, but this will significantly increase the GWP of the mixture, contradicting the original intention of reducing the greenhouse effect. If a small amount of non-flammable hydrofluorocarbons such as R-134a and R-227ea are added to the refrigerant as flame retardants, it can also expand the flammability limit range and reduce the combustion rate to some extent; however, these substances still have high GWPs, and excessive addition will reduce refrigeration performance. Another more environmentally friendly method of flame suppression is to add physical or chemical flame retardants. Trifluoroiodomethane has attracted attention due to its strong chemical flame retardant effect and low GWP, but it has problems such as toxicity and slight ozone depletion potential, and excessively high concentrations may affect the refrigeration cycle performance. It is not yet widely used in commercial air conditioning systems.

[0003] In general, existing methods for reducing the flammability of low-GWP refrigerants either sacrifice environmental friendliness, introduce new risks such as toxicity and corrosion, or increase system complexity and cost. Therefore, there is an urgent need for an innovative technological solution that can maintain the refrigerant's ultra-low greenhouse effect value, significantly reduce its flammability risk, and without sacrificing refrigeration performance. Summary of the Invention

[0004] The purpose of this invention is to provide a high-efficiency, environmentally friendly, low-GWP air conditioning refrigerant formulation and its preparation method, aiming to solve the contradiction between high flammability and reduced energy efficiency faced by low-GWP refrigerants in practical applications. This invention uses a high-efficiency natural working fluid and an ultra-low GWP fourth-generation refrigerant as the main components, and introduces a small amount of phosphorus-nitrogen hybrid "molecular cage" compound as a flame-retardant additive. Nanoscale dispersion of the additive is achieved through low-temperature ultrasonic-assisted microfluidic homogenization technology, and online monitoring technology ensures component stability, thus preparing a high-efficiency, environmentally friendly, low-GWP air conditioning refrigerant. This significantly improves the safety of the refrigerant and reduces its flammability level while maintaining its low GWP.

[0005] The specific technical solution is as follows: A high-efficiency, environmentally friendly, low-GWP air conditioning refrigerant formulation and its preparation method, comprising the following steps: The composition and mass percentage of the high-efficiency and environmentally friendly low-GWP air conditioner refrigerant are as follows: 40% to 60% high-efficiency natural working fluid, 38.5% to 55% fluorinated olefin refrigerant, and 1.5% to 5% flame retardant additives.

[0006] S1: Under nitrogen protection and at -40℃, a high-efficiency natural working fluid and a fluorinated olefin refrigerant are mixed in proportion and added to a pressure-resistant stainless steel reactor with a stirring and ultrasonic transducer interface. The ultrasonic oscillation device is started, and the transducer probe is inserted into the liquid phase inside the reactor to allow it to act on the liquid continuously, thus preparing the main refrigerant mixture. Furthermore, for high-efficiency natural working fluids, R-290 (propane) or R-1270 (propylene) are selected, and for fluorinated olefin refrigerants, R-1234yf (2,3,3,3-tetrafluoropropylene) or R-1234ze(E) (1,3,3,3-tetrafluoropropylene) are selected.

[0007] Furthermore, the ultrasound parameters were set to an ultrasound frequency of 25kHz and a power of 50W.

[0008] S2: The flame retardant additive and POE lubricating oil are mixed in a dispersion vessel and initially dispersed by high-speed shearing to prepare a concentrated flame retardant slurry.

[0009] Furthermore, the flame retardant additive chosen is hexaphenoxycyclotriphosphazene.

[0010] Furthermore, the amount of POE lubricating oil added is 1% to 3% of the total mass of the main refrigerant.

[0011] Furthermore, the high-speed shearing parameters were 5000 rpm and 30 minutes.

[0012] S3: The concentrated slurry prepared in step S2 is slowly added to the reactor containing the main refrigerant mixture in step S1 at -40℃; then it is transported to a high-pressure micro-jet homogenizer, the high-pressure micro-jet circulation pump is started, and the circulation flow rate is 5L / min under a high pressure of 60MPa. The ultrasonic and micro-jet processes are combined for 15 minutes to fully pulverize and uniformly disperse the flame retardant solid in the refrigerant liquid, thus preparing a nanoscale suspension solution. The reactor temperature is maintained at -40℃ throughout the mixing process.

[0013] S4: Use an online FTIR probe to monitor the infrared spectrum changes of the nanoscale suspension prepared above in real time, focusing on the intensity of the characteristic absorption peaks of each major component; take a sample of the suspension every 5 minutes through the sampling valve, and analyze its composition and particle size using GC (gas chromatography)-MS (mass spectrometry). If the error between the sampled component ratio and the initial feed ratio is less than 5%, and the error between two consecutive sampling analysis results is less than 3%, it indicates that the mixing has reached a uniform and stable state. At this point, stop the ultrasonic and jetting devices, and a high-efficiency, environmentally friendly, low-GWP air conditioning refrigerant is prepared.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention uses a high-efficiency natural working fluid, which has the advantages of high latent heat and high energy efficiency, and can significantly improve the coefficient of performance and cooling capacity of the refrigeration cycle.

[0015] 2. The flame retardant additive used in this invention has excellent flame retardant properties. During combustion, it can capture free radicals and release inert gases to inhibit the combustion chain reaction, which greatly reduces the combustion heat and flame propagation rate of the mixed refrigerant.

[0016] 3. This invention achieves nanoscale dispersion of additives through low-temperature ultrasonic-assisted microfluidic homogenization technology and utilizes online monitoring to ensure component stability. Attached Figure Description

[0017] Figure 1 This is a process flow diagram for preparing a high-efficiency, environmentally friendly, low-GWP air conditioning refrigerant according to the present invention.

[0018] Figure 2 The infrared spectrum of the high-efficiency, environmentally friendly, low-GWP air conditioning refrigerant prepared in Example 1 is shown.

[0019] Figure 3 This is a data comparison chart of the lower flammability limit test results for Experiment Example 1. Detailed Implementation

[0020] The following embodiments further explain and illustrate the technical solutions of the present invention. It should be specifically noted that each specific embodiment is a concretization and explanation of the technical solution and should not be considered as a limitation on the scope of protection of the present invention. Those skilled in the art still have the right to modify the technical solutions of these embodiments and make equivalent substitutions for some or all of the technical features, and these modifications or substitutions do not change the essence of the corresponding technical solutions, nor do they cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions described in the present invention.

[0021] like Figure 1 The diagram shows a preparation process for a high-efficiency, environmentally friendly, low-GWP air conditioning refrigerant. The detailed preparation steps are as follows: The composition and mass percentage of the high-efficiency and environmentally friendly low-GWP air conditioner refrigerant are as follows: 40% to 60% high-efficiency natural working fluid, 38.5% to 55% fluorinated olefin refrigerant, and 1.5% to 5% flame retardant additives.

[0022] 1. Main refrigerant mixing Under nitrogen protection and at -40℃, a high-efficiency natural working fluid and a fluorinated olefin refrigerant are mixed in proportion and added to a pressure-resistant stainless steel reactor with a stirring and ultrasonic transducer interface. The ultrasonic oscillation device is started, the transducer probe is inserted into the liquid phase inside the reactor, the ultrasonic frequency is set to 25kHz and the power to 50W, and it is allowed to act on the liquid continuously to prepare the main refrigerant mixture. For high-efficiency natural working fluids, choose R-290 (propane) or R-1270 (propylene). For fluorinated olefin refrigerants, choose R-1234yf (2,3,3,3-tetrafluoropropylene) or R-1234ze(E) (1,3,3,3-tetrafluoropropylene).

[0023] High-efficiency natural working fluids have the advantages of high latent heat and high energy efficiency, which can significantly improve the performance coefficient (coefficient of performance) and cooling capacity of the refrigeration cycle. However, their use alone poses a safety hazard due to their high flammability. R-1234yf and R-1234ze(E) have much lower heat of combustion and burning rate than hydrocarbons, which can dilute the flammability of high-efficiency natural working fluids to a certain extent.

[0024] 2. Flame retardant pre-dispersion Hexaphenoxycyclotriphosphazene flame retardant additive was mixed with POE (polyether ester) lubricating oil in a dispersion vessel. The amount of lubricating oil added was 1-3% of the total mass of the main refrigerant. Then, it was initially dispersed by high-speed shearing at 5000 rpm for 30 minutes to prepare a concentrated flame retardant slurry. This step can prevent the flame retardant from agglomerating due to excessively large particle size or high surface energy when added directly.

[0025] Cyclic phosphazene compounds containing phosphorus and nitrogen are selected as flame-retardant additives for refrigerants. These compounds possess a unique cage-like molecular structure, high thermal stability, and release phosphorus-containing free radicals and inert gases under combustion conditions, inhibiting flame propagation from both the gas and condensed phases. The flame retardant has a PN six-membered ring skeleton, with each phosphorus atom bonded to organic groups such as aryloxy groups, forming a cage-like three-dimensional structure. These compounds are structurally stable, halogen-free, and environmentally friendly, and as additive flame retardants, they effectively suppress smoke and fire; they release almost no toxic gases during combustion and do not cause secondary disasters. Utilizing these properties, a small amount is introduced into the refrigerant system, where it can inhibit the combustion reaction through free radical capture and heat absorption when a flame appears, thereby reducing the overall flammability risk of the refrigerant.

[0026] 3. High-pressure homogenization The concentrated slurry prepared above was slowly added to a reactor containing the main refrigerant mixture at -40°C; then it was transported to a high-pressure micro-jet homogenizer, and the high-pressure micro-jet circulation pump was started. Under a high pressure of 60MPa and a circulation flow rate of 5L / min, the ultrasonic and micro-jet processes were combined for 15 minutes to fully pulverize and uniformly disperse the flame retardant solid in the refrigerant liquid, thus preparing a nanoscale suspension solution. The reactor temperature was maintained at -40°C throughout the mixing process.

[0027] Utilizing extremely high shear force and cavitation effect, flame retardant particles are broken down and uniformly dispersed to the nanoscale with a particle size <100nm, forming a thermodynamically stable colloidal dispersion system. This completely solves the sedimentation and separation problems that may occur during long-term storage or operation. Low-temperature operation aims to prevent the polymerization or decomposition of fluorinated olefin components due to localized overheating.

[0028] 4. Online monitoring The infrared spectrum changes of the nanoscale suspension prepared above were monitored in real time using an online FTIR probe, focusing on the intensity of the characteristic absorption peaks of each major component. The suspension was sampled every 5 minutes through a sampling valve, and its composition and particle size were analyzed by GC (gas chromatography)-MS (mass spectrometry). The results showed that the error between the sampled component ratio and the initial feed ratio was less than 5%, and the error between two consecutive sampling analyses was less than 3%, indicating that the mixing had reached a homogeneous and stable state. At this point, the ultrasonic and jetting devices were stopped, and a high-efficiency, environmentally friendly, low-GWP air conditioning refrigerant was prepared.

[0029] Example 1, Table 1 Raw Material Information

[0030] A high-efficiency, environmentally friendly, low-GWP air conditioning refrigerant formulation and its preparation method are described below: The composition and mass percentage of the high-efficiency and environmentally friendly low-GWP air conditioning refrigerant are: R-290 50%, R-1234yf 47.5%, and hexaphenoxycyclotriphosphazene flame retardant additive 2.5%.

[0031] S1: Under nitrogen protection and at -40℃, R-290 and R-1234yf are mixed and added to a pressure-resistant stainless steel reactor with a stirrer and an ultrasonic transducer interface. The ultrasonic oscillation device is started, and the ultrasonic parameters are set to an ultrasonic frequency of 25kHz and a power of 50W. The transducer probe is inserted into the liquid phase in the reactor and allowed to act on the liquid continuously to prepare the main refrigerant mixture. S2: Mix hexaphenoxycyclotriphosphazene flame retardant additive with POE lubricating oil in a dispersion vessel. The amount of POE lubricating oil added is 2% of the total mass of the main refrigerant. The mixture is initially dispersed by high-speed shearing at a speed of 5000 rpm for 30 minutes to prepare a concentrated slurry of flame retardant.

[0032] S3: The concentrated slurry prepared in step S2 is slowly added to the reactor containing the main refrigerant mixture in step S1 at -40℃; then it is transported to a high-pressure micro-jet homogenizer, the high-pressure micro-jet circulation pump is started, and the circulation flow rate is 5L / min under a high pressure of 60MPa. The ultrasonic and micro-jet processes are combined for 15 minutes to fully pulverize and uniformly disperse the flame retardant solid in the refrigerant liquid, thus preparing a nanoscale suspension solution. The reactor temperature is maintained at -40℃ throughout the mixing process.

[0033] S4: Use an online FTIR probe to monitor the infrared spectrum changes of the nanoscale suspension prepared above in real time, focusing on the intensity of the characteristic absorption peaks of each major component; take samples of the suspension every 5 minutes through the sampling valve, and analyze its composition and particle size using GC-MS. If the error between the sampled component ratio and the initial feed ratio is less than 5%, and the error between two consecutive sampling analysis results is less than 3%, it indicates that the mixing has reached a uniform and stable state. At this point, stop the ultrasonic and jetting devices, and a high-efficiency, environmentally friendly, low-GWP air conditioning refrigerant is prepared.

[0034] Example 2, prepared using the same method as Example 1, but with the following differences: The composition and mass percentage of the high-efficiency and environmentally friendly low-GWP air conditioning refrigerant are: R-1270 40% (industrial grade), R-1234ze(E) (electronic grade) 55%, and hexaphenoxycyclotriphosphazene flame retardant additive 5%.

[0035] The amount of POE lubricating oil added in step S2 is 1% of the total mass of the main refrigerant.

[0036] Example 3, prepared using the same method as Example 1, but with the following differences: The composition and mass percentage of the high-efficiency and environmentally friendly low-GWP air conditioning refrigerant are: R-290 60%, R-1234yf 38.5%, and hexaphenoxycyclotriphosphazene flame retardant additive 1.5%.

[0037] The amount of POE lubricating oil added in step S2 is 3% of the total mass of the main refrigerant.

[0038] Comparative Example 1 was prepared using the same method as in Example 1, but with the use of the conventional flame retardant R-134a (tetrafluoroethane) (industrial grade). All other steps were the same.

[0039] Comparative Example 2 was prepared using the same method as in Example 1, but without the addition of a flame retardant. All other steps were the same.

[0040] Comparative Example 3 was prepared using the same method as in Example 1, but without high-pressure averaging; only simple physical mixing was performed, with a stirring speed of 500 rpm and a stirring time of 2 hours. All other steps were the same.

[0041] Comparative Example 4 was prepared using the same method as in Example 1, but the composition and mass percentage of the high-efficiency, environmentally friendly, low-GWP air conditioning refrigerant were: R-290 48%, R-1234yf 46%, and flame retardant additive 6%. All other steps were the same.

[0042] Experimental Example 1: The high-efficiency, environmentally friendly, low-GWP air conditioning refrigerant prepared in Example 1 was subjected to infrared spectroscopy testing, with parameters set to a spectral range of 4000-500 cm⁻¹. -1 4cm resolution -1 The sample was scanned 16-32 times, and the measured spectrum is as follows. Figure 2 As shown, it can be seen that the R-290 at 3000cm -1 The CH stretching vibration peaks around 1800 cm⁻¹, and R-1234yf at 1800 cm⁻¹ -1 The nearby C=C double bond peak, and the hexaphenoxycyclotriphosphazene additive at 1200–1000 cm⁻¹ -1 The vibrational peaks of the P=N and PO bonds, the infrared absorption peaks of each component should remain stable and consistent with the positions of the pure substance spectrum, and there should be no new absorption peaks, indicating that no side reactions produce new substances.

[0043] Example 2 compares the comprehensive performance of high-efficiency, environmentally friendly, low-GWP air conditioning refrigerants prepared in Examples 1-3 and Comparative Examples 1-4. The GWP value was calculated according to the method described in the IPCC AR6C Sixth Evaluation Report. GWP is a relative value, defined as the cumulative radiative forcing (i.e., contribution to global warming) produced by 1 kg of a greenhouse gas relative to 1 kg of carbon dioxide over a 100-year timescale. Flammability testing was conducted according to ASTM E681-09 (2023), "Standard Test Methods for Flammability Concentration Limits of Chemicals (Vapor and Gas)". The coefficient of performance (COP) was determined according to AHRI 540-2015, "Performance Rating of Positive Displacement Refrigerant Compressors and Compressor Units," with a COP of 3.25 for pure R-290 refrigerant under the same operating conditions as a benchmark. Specific test comparison results are shown in Table 2. Figure 3 As shown: Table 2. Comparison of overall performance between Examples 1-3 and Comparative Examples 1-4

[0044] The comparison results above show that, in Comparative Example 1, the use of a traditional flame retardant resulted in a higher GWP value than that of Example 1, and the refrigerant was able to burn in the ignition test; in Comparative Example 2, no flame retardant was added, and although the GWP value was lower, there were significant safety and convenience risks, resulting in a high flammability rating; in Comparative Example 3, the lack of high-pressure averaging resulted in uneven refrigerant dispersion and precipitation, thus causing the refrigerant to malfunction; in Comparative Example 4, the flame retardant content was increased, and although the refrigerant was completely unignitable in the combustion test and had no lower flammability limit, exhibiting no combustion, the high flame retardant content increased the refrigerant viscosity, affecting heat exchange performance and leading to a decrease in the coefficient of performance (COP).

[0045] In summary, the above experiments demonstrate that the high-efficiency, environmentally friendly, low-GWP air conditioning refrigerant formulation provided by this invention significantly reduces the flammability of the refrigerant while maintaining excellent refrigeration performance, ensuring extremely low GWP.

Claims

1. A high-efficiency, environmentally friendly, low-GWP air conditioning refrigerant formulation, characterized in that, The high-efficiency, environmentally friendly, low-GWP air conditioning refrigerant has the following composition and mass percentage: 40%–60% high-efficiency natural working fluid, 38.5%–55% fluorinated olefin refrigerant, and 1.5%–5% flame retardant additive.

2. The high-efficiency, environmentally friendly, low-GWP air conditioning refrigerant formulation as described in claim 1, characterized in that, The high-efficiency natural working fluid is selected from R-290 or R-1270.

3. The high-efficiency, environmentally friendly, low-GWP air conditioning refrigerant formulation as described in claim 1, characterized in that, The fluorinated olefin refrigerant is selected from 2,3,3,3-tetrafluoropropylene or 1,3,3,3-tetrafluoropropylene.

4. The high-efficiency, environmentally friendly, low-GWP air conditioning refrigerant formulation as described in claim 1, characterized in that, The flame retardant additive is selected from hexaphenoxycyclotriphosphazene.

5. The preparation method of a high-efficiency, environmentally friendly, low-GWP air conditioning refrigerant formulation as described in any one of claims 1-4, characterized in that, Includes the following steps: S1: Under nitrogen protection, high-efficiency natural working fluid and fluorinated olefin refrigerant are mixed in proportion and added to a pressure-resistant stainless steel reactor with a stirring and ultrasonic transducer interface. The ultrasonic oscillation device is started, and the transducer probe is inserted into the liquid phase in the reactor to allow it to act on the liquid continuously, thus preparing the main refrigerant mixture. S2: The flame retardant additive is mixed with POE lubricating oil in a dispersion vessel and initially dispersed by high-speed shearing to prepare a concentrated flame retardant slurry; S3: Add the concentrated slurry prepared in step S2 to the reaction vessel containing the main refrigerant mixture in step S1; then transfer it to the high-pressure micro-jet homogenizer, start the high-pressure micro-jet circulation pump, and use ultrasound and micro-jet combined action for 15 minutes to fully crush and uniformly disperse the flame retardant solid in the refrigerant liquid to prepare a nano-scale suspension solution. S4: Use an online FTIR probe to monitor the infrared spectrum changes of the nanoscale suspension prepared above in real time, focusing on the intensity of the characteristic absorption peaks of each major component; take samples of the suspension every 5 minutes through the sampling valve, and analyze its composition and particle size using GC-MS. If the error between the sampled component ratio and the initial feed ratio is less than 5%, and the error between two consecutive sampling analysis results is less than 3%, it indicates that the mixing has reached a uniform and stable state. At this point, stop the ultrasonic and jetting devices, and a high-efficiency, environmentally friendly, low-GWP air conditioning refrigerant is prepared.

6. The preparation method of a high-efficiency, environmentally friendly, low-GWP air conditioning refrigerant formulation as described in claim 5, characterized in that, The ultrasound described in step S1 has the following parameters: frequency 25kHz and power 50W.

7. The preparation method of a high-efficiency, environmentally friendly, low-GWP air conditioning refrigerant formulation as described in claim 5, characterized in that, The POE lubricating oil mentioned in step S2 is added at a rate of 1% to 3% of the total mass of the main refrigerant.

8. The preparation method of a high-efficiency, environmentally friendly, low-GWP air conditioning refrigerant formulation as described in claim 5, characterized in that, The high-speed shearing described in step S2 is set with a rotation speed of 5000 rpm and a time of 30 minutes.

9. The preparation method of a high-efficiency, environmentally friendly, low-GWP air conditioning refrigerant formulation as described in claim 5, characterized in that, The high-pressure micro-jet circulating pump mentioned in step S3 has the following parameters: high pressure 60MPa, circulation flow rate 5L / min.

10. A method for preparing a high-efficiency, environmentally friendly, low-GWP air conditioning refrigerant formulation as described in any one of claims 1-4, 6-9, characterized in that, In the preparation method described above, the temperature is maintained at -40℃ throughout the entire preparation process.

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