Method for measuring refrigerant ratio by gas chromatography
By using an alumina capillary column and a flame ionization detector in gas chromatography, the problem of requiring different instruments for the detection of R404 and R507 series refrigerants was solved, enabling efficient and accurate detection using the same gas chromatograph and improving the repeatability and sensitivity of the detection results.
Patent Information
- Application Number
- CN202511755610.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-27
- Publication Date
- 2025-12-26
AI Technical Summary
In the existing technology, the detection of R404 and R507 series refrigerants requires the use of different gas chromatographs and detectors, resulting in low instrument utilization and poor repeatability and accuracy of the detection results.
Using an alumina capillary column and a flame ionization detector, combined with specific chromatographic analysis conditions, the ratio of R404 and R507 series refrigerants can be simultaneously detected on the same gas chromatograph, and quantification is performed using the corrected area normalization method.
It improves the sensitivity and repeatability of detection, with a sensitivity of 10-11 g/mL, a wide linear range, and reduces the influence of air peaks on the analysis results, thus achieving efficient and accurate refrigerant ratio analysis.
Smart Images
Figure CN121208217A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of gas chromatography analysis technology for refrigerants, and specifically relates to a method for determining the refrigerant ratio by gas chromatography. Background Technology
[0002] The R404 series is a mixed refrigerant prepared by mixing 1,1,1-trifluoroethane (hereinafter referred to as R143a), pentafluoroethane (hereinafter referred to as R125), and 1,1,1,2-tetrafluoroethane (hereinafter referred to as R134a) in a certain mass ratio. The R507 series is a refrigerant prepared by mixing R143a and R125 in a certain mass ratio. Currently, when testing the quality of R404 and R507 series refrigerant products, the R404 series refrigerant ratio analysis method uses the packed column and thermal conductivity detector specified in the standard "HG / T5161-2017 Mixed Refrigerant R404 Series" for analysis, while the R507 series refrigerant uses the capillary column and thermal conductivity detector specified in the standard "HG / T6052-2022 Mixed Refrigerant R507 Series" for analysis. In the detection of R404 series refrigerants, the low column efficiency of packed columns and the increased mass transfer resistance due to irregular flow paths between packing particles can lead to peak broadening and poor separation. While the standard specifications for R507 series refrigerants specify capillary columns suitable for high-temperature analysis, low-boiling-point refrigerants do not require high-temperature-appropriate columns. Furthermore, the thermal conductivity detectors used for both series produce air peaks during analysis, and large air peaks can affect analytical repeatability. The determination of R404 and R507 series refrigerants requires different gas chromatographs, reducing instrument utilization. Therefore, it is necessary to develop a gas chromatographic method capable of simultaneously determining the ratios of R404 and R507 series refrigerants to maximize instrument utilization. Summary of the Invention
[0003] This invention provides a method for determining refrigerant ratio by gas chromatography, which solves the defects of existing standard testing methods and enables the same gas chromatograph to detect both R404 series refrigerants and R507 series refrigerants with the same parameters set.
[0004] The technical solution of this invention is as follows: The refrigerants were R404 and R507 series. Sampling was carried out using sampling cylinders. Standard samples were prepared according to HG / T5161-2017 and HG / T6052-2022. The content of R404 and R507 series refrigerants was determined by gas chromatography. The chromatographic columns were all alumina capillary columns, the detectors were all flame ionization detectors, and the carrier gas was nitrogen.
[0005] Preferably, the sampling cylinder is a dual-valve type cylinder with a working pressure greater than 4MPa.
[0006] Preferred chromatographic analysis conditions: injection port vaporization chamber temperature 110℃-180℃, column oven temperature 150℃-170℃, temperature programmed mode, detector temperature 210℃-280℃, split ratio (20-40):1; column flow rate 3mL / min-5mL / min, linear velocity 26cm / s-28cm / s.
[0007] Preferred chromatographic analysis conditions: injection port vaporization chamber temperature 150℃, column oven temperature 150℃, programmed temperature ramp mode, detector temperature 250℃, split ratio 30:1; column flow rate 3.55mL / min, linear velocity 27.3cm / s.
[0008] Preferably, the capillary column is a capillary column with aluminum oxide as the stationary phase.
[0009] Preferably, the capillary column is CP-Al2O3 / KCl.
[0010] Preferably, the capillary column has a length of 50m, a stationary phase liquid film thickness of 10μm, and an inner diameter of 0.53mm.
[0011] Preferably, the operation steps are as follows: 1) Samples were taken from the finished refrigerant tanks of R404 and R507 series using 500mL double-valve small steel cylinders and injected for chromatographic analysis; 2) Based on the peak results, the corrected area normalization method was used to quantify the results of each component of the refrigerant.
[0012] Preferably, the injection volume of R404 series and R507 series refrigerant samples is 0.2mL-0.3mL.
[0013] The R404 series refrigerant standard HG / T5161-2017 uses a thermal conductivity detector with a β,β'-oxodiacetonitrile packed column. In terms of sensitivity, the thermal conductivity detector has relatively low sensitivity, typically around 10. -6 ~10 -5 The peak shape of packed columns is not as sharp as that of capillary columns, and it is accompanied by tailing. The R507 series refrigerant standard HG / T6052-2022 uses an alumina capillary column with a small thermal conductivity detector and sodium sulfate deactivation. The detection limit of the small thermal conductivity cell is lower than that of the large thermal conductivity cell, which affects the accuracy of the analysis results. The sodium sulfate deactivation capillary column is characterized by high thermal stability and is suitable for high temperature analysis. However, the sulfur layer will gradually be lost during long-term use, causing the active sites to be re-exposed. At the same time, the shedding of the sulfur layer will cause contamination of the thermal conductivity detector.
[0014] Compared with the prior art, the present invention has the following advantages: This invention uses gas chromatography to determine the content of R404 and R507 series refrigerants in their proportions. The chromatographic columns used are all alumina capillary columns, and the detectors are all flame ionization detectors. Under specific chromatographic conditions, the same gas chromatograph can detect both R404 and R507 series refrigerants with pre-set parameters, exhibiting extremely high sensitivity and a detection limit of 10. -11 g / mL, with a wide linear range of 10 g / mL. 5 -10 7 Between these parameters, it responds well to hydrofluorocarbons, and FID does not respond to air introduced during sampling, reducing its impact on analytical results. Attached Figure Description
[0015] Figure 1 This is a chromatogram of the R404 series refrigerants detected by the method in Example 1 of the present invention.
[0016] Figure 2 The chromatogram is the result of testing for R404 series refrigerants in Comparative Example 1 according to standard HG / T5161-2017.
[0017] Figure 3 This is a chromatogram of the R507 series refrigerant detected by the method in Example 1 of the present invention.
[0018] Figure 4 The chromatogram is the result of testing for the R507 series refrigerant in Comparative Example 1 according to standard HG / T6052-2022.
[0019] Figure 5 This is a chromatogram of the R404 series refrigerants detected by the method in Example 2 of the present invention.
[0020] Figure 6 This is a chromatogram of the R507 series refrigerant detected by the method in Example 2 of the present invention.
[0021] Figure 7 This is a chromatogram of the R404 series refrigerants detected by the method in Example 3 of the present invention.
[0022] Figure 8 This is a chromatogram of the R507 series refrigerant detected by the method in Example 3 of the present invention. Detailed Implementation
[0023] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions will be clearly and completely described below in conjunction with the embodiments of this invention.
[0024] Example 1 A gas chromatography method for determining the refrigerant ratio, using R404 and R507 series refrigerants, is described below, along with the sampling and preparation containers and chromatographic conditions: The sampling cylinder used was a small double-valve cylinder with a volume of 500mL and a working pressure of 5MPa; The standard samples were prepared in accordance with HG / T5161-2017 and HG / T6052-2022. The chromatographic column used was a capillary column CP-Al2O3 / KCl; the column length was 50m, the stationary phase liquid film thickness was 10μm, and the inner diameter was 0.53mm. Inlet vaporization chamber temperature: 150℃; Column oven temperature: Initial temperature 60℃, hold for 1 min, then increase to 150℃ at 10℃ / min and hold for 4 min; Flow split ratio: 30:1; Column flow rate: 3.55 mL / min; Linear velocity: 27.3 cm / s; Hydrogen flame ionization detector temperature: 250℃; Injection volume: 0.2 mL; Carrier gas (nitrogen): flow rate 35 mL / min.
[0025] According to the above chromatographic conditions, R404 series refrigerants and R507 series refrigerants were injected and chromatographically analyzed. After the separation of each component, the corrected area normalization method was used to quantify each component of R404 series and R507 series refrigerants. The correction factor was prepared and calculated according to the above standard.
[0026] Five tests were conducted on the same R404 refrigerant sample under the same conditions using the same gas chromatograph. The results are shown in Table 1. The chromatograms of the R404 series refrigerants are shown in the figure below. Figure 1 As shown.
[0027] Table 1. Mass fraction of each component in R404 series refrigerants
[0028] Table 1 shows that in the R404 series, the mass fraction of R143a is 52.13%-52.25%, with an average of 52.18%, and the difference between its maximum and minimum values is 0.12%; the mass fraction of R125 is 44.44%-44.54%, with an average of 44.50%, and the difference between its maximum and minimum values is 0.10%; and the mass fraction of R134a is 3.31%-3.34%, with an average of 3.32%, and the difference between its maximum and minimum values is 0.03%. This indicates that the error of each component is very small and the results have good repeatability.
[0029] Five tests were conducted on the same R507 refrigerant sample under the same conditions using the same gas chromatograph. The results are shown in Table 2. The chromatograms of the R507 series refrigerants are shown below. Figure 3 As shown.
[0030] Table 2 Mass fraction of each component in R507 series refrigerants
[0031] As shown in Table 2, the mass fraction of R143a in the R507 series is 49.67%-49.83%, with an average of 49.76%, and the difference between its maximum and minimum values is 0.16%; the mass fraction of R125 is 50.17%-50.33%, with an average of 50.24%, and the difference between its maximum and minimum values is also 0.16%. This also indicates that the error of each component is very small and the results have good repeatability.
[0032] Comparative Example 1 According to the analytical method specified in R404 standard HG / T5161-2017, the chromatographic analysis of R404 series refrigerants uses packed column separation and thermal conductivity detector analysis. The chromatogram is shown below. Figure 2 As shown.
[0033] The sampling cylinder used was a small, double-valve cylinder with a volume of 500 mL and a working pressure of 5 MPa. The standard samples were prepared in accordance with HG / T5161-2017; A packed column was selected for the chromatographic column; the column length was 3m, the stationary phase was β,β´-oxadipropionitrile, and the inner diameter was 3mm. Inlet vaporization chamber temperature: 80℃; Column oven temperature: 55℃; Bridge current: 120mA; Carrier gas (H2) flow rate: 35 mL / min; Thermal conductivity detector temperature: 250℃; Injection volume: 1 mL.
[0034] Table 3 shows the results of five consecutive tests on the same sample under given conditions, according to the analytical method specified in R404 standard HG / T5161-2017.
[0035] Table 3 Mass fraction of each component in R404 series refrigerants
[0036] Table 3 shows that in the R404 series, the mass fraction of R143a is 52.11%-52.35%, with an average of 52.19%, and the difference between its maximum and minimum values is 0.24%; the mass fraction of R125 is 44.16%-44.62%, with an average of 44.43%, and the difference between its maximum and minimum values is 0.46%; and the mass fraction of R134a is 3.28%-3.56%, with an average of 3.38%, and the difference between its maximum and minimum values is 0.28%. This indicates that the repeatability of the errors of each component is not good compared with the results in Table 1.
[0037] According to the R507 standard HG / T6052-2022, the R507 series refrigerants are separated using capillary column separation and analyzed by a thermal conductivity detector. Their chromatograms are shown below. Figure 4 As shown.
[0038] The sampling cylinder used was a small, double-valve cylinder with a volume of 500 mL and a working pressure greater than 4 MPa; The standard samples were prepared in accordance with HG / T6052-2022; A packed column was selected for the chromatography; the column length was 50m, the stationary phase liquid film thickness was 15μm, and the inner diameter was 0.53mm. Inlet vaporization chamber temperature: 150℃; Column oven temperature: Initial temperature 80℃, hold for 5 min, then increase to 130℃ at 20℃ / min and hold for 6 min; Average linear velocity of carrier gas (H2): 44 cm / min; Flow split ratio: 15:1; Thermal conductivity detector temperature: 250℃; Bridge current: 80mA; Injection volume: 0.5 mL.
[0039] Table 4 shows the results of five consecutive tests on the same sample under given conditions, according to the analytical method specified in R507 standard HG / T6052-2022.
[0040] Table 4. Mass fraction of each component in R507 series refrigerants
[0041] As shown in Table 4, the mass fraction of R143a in the R507 series is 49.65%-49.93%, with an average of 49.80%, and the difference between its maximum and minimum values is 0.28%; the mass fraction of R125 is 50.07%-50.35%, with an average of 50.22%, and the difference between its maximum and minimum values is also 0.28%. This also indicates that the repeatability of the errors of each component is not good compared with the results in Table 2.
[0042] Table 5 shows a comparison of the RSDs of R404 series refrigerants under different testing methods.
[0043] Table 5 Comparison of RSD under different test methods for R404 series refrigerants.
[0044] As can be seen from the comparison in Table 5, the RSD value R143a calculated using the hydrogen flame ionization detector / Al2O3 / KCl capillary column data is 0.094%, while the RSD value of the packed column thermal / conductivity detector is 0.23%. The RSD value of R125 using the hydrogen flame ionization detector / Al2O3 / KCl capillary column is 0.085%, while the RSD of the packed column / thermal conductivity detector is 0.41%. The difference in R134a is even greater, with an RSD of 0.42% using the capillary column Al2O3 / KCl / hydrogen flame ionization detector and 3.55% using the packed column / thermal conductivity detector, which fully demonstrates that the repeatability of this method is better than the detection method specified in the standard.
[0045] Table 6 shows a comparison of the RSDs of R507 series refrigerants under different testing methods.
[0046] Table 6. Comparison of RSD under different test methods for R507 series refrigerants.
[0047] As can be seen from the comparison in Table 6, the RSD value R143a of the R507 series refrigerant calculated using data from a capillary column Al2O3 / KCl / hydrogen flame ionization detector is 0.12%, and the capillary column Al2O3 / Na S The RSD of the O4 / thermal conductivity detector is 0.26%; the RSD of R125 using a capillary column Al2O3 / KCl / hydrogen flame ionization detector is 0.12%, while the RSD of the capillary column Al2O3 / Na2SO4 / thermal conductivity detector is 0.26%; similarly, the repeatability of this method is better than that of the detection method specified in the standard.
[0048] Therefore, it is evident that when performing gas chromatographic analysis on R404 and R507 series refrigerants, using an Al2O3 / KCl capillary column and a more sensitive flame ionization detector yielded excellent testing results. In particular, the difference between the maximum and minimum values of parallel measurements was better than that of the standard-specified detection method, and the RSD value was also superior. This method is fully applicable to the proportioning analysis of R404 and R507 series refrigerants and can be used to determine the qualification of R404 and R507 series refrigerant samples, with accuracy and sensitivity meeting the requirements.
[0049] Example 2 A gas chromatography method for determining the refrigerant ratio, using R404 and R507 series refrigerants, is described below, along with the sampling and preparation containers and chromatographic conditions: The sampling cylinder used was a small, double-valve cylinder with a volume of 500 mL and a working pressure of 5 MPa. The standard samples were prepared in accordance with HG / T5161-2017 and HG / T6052-2022. The chromatographic column used was a capillary column CP-Al2O3 / KCl; the column length was 50m, the stationary phase liquid film thickness was 10μm, and the inner diameter was 0.53mm. Inlet vaporization chamber temperature: 110℃; Column oven temperature: Initial temperature 50℃, hold for 1 min, then increase to 160℃ at 10℃ / min and hold for 4 min; Flow split ratio: 20:1; Column flow rate: 3.0 mL / min; Linear velocity: 26.0 cm / s; Hydrogen flame ionization detector temperature: 210℃; Injection volume: 0.25 mL; Carrier gas (nitrogen): flow rate 35 mL / min.
[0050] According to the above chromatographic conditions, R404 series refrigerants and R507 series refrigerants were injected and chromatographically analyzed. After the separation of each component, the corrected area normalization method was used to quantify each component of R404 series and R507 series refrigerants. The correction factor was prepared and calculated according to the above standard.
[0051] Five tests were conducted on the same R404 refrigerant sample under the same conditions using the same gas chromatograph. The results are shown in Table 7. The chromatograms of the R404 series refrigerants are shown below. Figure 5 As shown.
[0052] Table 7 Mass fraction of each component in R404 series refrigerants
[0053] Table 7 shows that in the R404 series, the mass fraction of R143a is 52.12%-52.25%, with an average of 52.19%, and the difference between its maximum and minimum values is 0.13%; the mass fraction of R125 is 44.42%-44.55%, with an average of 44.47%, and the difference between its maximum and minimum values is 0.13%; and the mass fraction of R134a is 3.32%-3.35%, with an average of 3.34%, and the difference between its maximum and minimum values is 0.03%. This indicates that the errors of each component are very small, and the results have good repeatability. Five tests were conducted on the same R507 refrigerant sample under the same conditions using the same gas chromatograph. The results are shown in Table 8. The chromatograms of the R507 series refrigerants are shown below. Figure 6 As shown.
[0054] Table 8. Mass fraction of each component in R507 series refrigerants
[0055] As shown in Table 8, the mass fraction of R143a in the R507 series is 49.68%-49.84%, with an average of 49.75%, and the difference between its maximum and minimum values is 0.16%; the mass fraction of R125 is 50.16%-50.32%, with an average of 50.25%, and the difference between its maximum and minimum values is also 0.16%. This also indicates that the error of each component is very small and the results have good repeatability.
[0056] Example 3 A gas chromatography method for determining the refrigerant ratio, using R404 and R507 series refrigerants, is described below, along with the sampling and preparation containers and chromatographic conditions: The sampling cylinder used was a small, double-valve cylinder with a volume of 500 mL and a working pressure of 5 MPa. The standard samples were prepared in accordance with HG / T5161-2017 and HG / T6052-2022. The chromatographic column used was a capillary column CP-Al2O3 / KCl; the column length was 50m, the stationary phase liquid film thickness was 10μm, and the inner diameter was 0.53mm. Inlet vaporization chamber temperature: 180℃; Column oven temperature: Initial temperature 60℃, hold for 1 min, then increase to 170℃ at 10℃ / min and hold for 4 min; Flow split ratio: 40:1; Column flow rate: 5.0 mL / min; Linear velocity: 28.0 cm / s; Hydrogen flame ionization detector temperature: 280℃; Injection volume: 0.30 mL; Carrier gas (nitrogen): flow rate 35 mL / min.
[0057] According to the above chromatographic conditions, R404 series refrigerants and R507 series refrigerants were injected and chromatographically analyzed. After the separation of each component, the corrected area normalization method was used to quantify each component of R404 series and R507 series refrigerants. The correction factor was prepared and calculated according to the above standard.
[0058] Five tests were conducted on the same R404 refrigerant sample under the same conditions using the same gas chromatograph. The results are shown in Table 9. The chromatograms of the R404 series refrigerants are shown below. Figure 7 As shown.
[0059] Table 9 Mass fraction of each component in R404 series refrigerants
[0060] Table 9 shows that in the R404 series, the mass fraction of R143a is 52.16%-52.24%, with an average of 52.20%, and the difference between its maximum and minimum values is 0.08%; the mass fraction of R125 is 44.44%-44.49%, with an average of 44.46%, and the difference between its maximum and minimum values is 0.05%; and the mass fraction of R134a is 3.32%-3.35%, with an average of 3.34%, and the difference between its maximum and minimum values is 0.03%. This indicates that the error of each component is very small and the results have good repeatability.
[0061] Five tests were conducted on the same R507 refrigerant sample under the same conditions using the same gas chromatograph. The results are shown in Table 10. The chromatograms of the R507 series refrigerants are shown below. Figure 8 As shown.
[0062] Table 10 Mass fraction of each component in R507 series refrigerants
[0063] As shown in Table 10, the mass fraction of R143a in the R507 series is 49.68%-49.82%, with an average of 49.76%, and the difference between its maximum and minimum values is 0.14%; the mass fraction of R125 is 50.18%-50.32%, with an average of 50.24%, and the difference between its maximum and minimum values is 0.16%. This also indicates that the error of each component is very small and the results have good repeatability.
Claims
1. A method for determining refrigerant ratio by gas chromatography, characterized in that, The refrigerants were R404 and R507 series. Sampling was carried out using sampling cylinders. Standard samples were prepared according to HG / T5161-2017 and HG / T6052-2022. The content of R404 and R507 series refrigerants was determined by gas chromatography. The chromatographic columns were all alumina capillary columns, the detectors were all flame ionization detectors, and the carrier gas was nitrogen.
2. The method for determining refrigerant ratio by gas chromatography as described in claim 1, characterized in that, The sampling cylinder is a double-valve type with a working pressure greater than 4MPa.
3. The method for determining refrigerant ratio by gas chromatography as described in claim 1, characterized in that, Chromatographic analysis conditions: injection port vaporization chamber temperature 110℃-180℃, column oven temperature 150℃-170℃, temperature programmed mode, detector temperature 210℃-280℃, split ratio (20-40):1; column flow rate 3mL / min-5mL / min, linear velocity 26cm / s-28cm / s.
4. The method for determining refrigerant ratio by gas chromatography as described in claim 1, characterized in that, Chromatographic analysis conditions: injection port vaporization chamber temperature 150℃, column oven temperature 150℃, programmed temperature ramp mode, detector temperature 250℃, split ratio 30:1; column flow rate 3.55mL / min, linear velocity 27.3cm / s.
5. The method for determining refrigerant ratio by gas chromatography as described in claim 1, characterized in that, The capillary column is a capillary column with aluminum oxide as the stationary phase.
6. The method for determining refrigerant ratio by gas chromatography as described in claim 1, characterized in that, The capillary column is CP-Al2O3 / KCl.
7. The method for determining refrigerant ratio by gas chromatography as described in claim 1, characterized in that, The capillary column is 50m long, the stationary phase liquid film is 10μm thick, and the inner diameter is 0.53mm.
8. The method for determining refrigerant ratio by gas chromatography as described in claim 7, characterized in that, The operating steps are as follows: 1) Samples were taken from the finished refrigerant tanks of R404 and R507 series using 500mL double-valve small steel cylinders and injected for chromatographic analysis; 2) Based on the peak elution results, the corrected area normalization method was used to quantify the results of each component of the refrigerant.
9. The method for determining refrigerant ratio by gas chromatography as described in claim 8, characterized in that, The injection volume for R404 and R507 series refrigerant samples is 0.2 mL to 0.3 mL.