A method for analyzing hydrocarbon content in high-purity ammonia and a pretreatment device

Abstract

The present invention discloses an analysis method and pretreatment device for hydrocarbon content in high-purity ammonia, which is detected by a gas chromatograph equipped with a hydrogen flame ionization detector, comprising the following steps: (1) taking liquid high-purity ammonia into a liquid ammonia collection cylinder; (2) the high-purity ammonia is treated by a pretreatment device before entering the gas chromatograph for analysis; (3) the hydrocarbon content in the high-purity ammonia w1=w0(V2+V 吸空 ) / V1; V1=(m0‑m1) / ρ; w0 is the hydrocarbon content of the gas in the syringe, ppm; V2 is the volume of the mixed gas entering the syringe, ml; V 吸空 is the volume of the absorption bottle minus the volume of the dilute sulfuric acid solution, ml; V1 is the volume of high-purity ammonia absorbed in the dilute sulfuric acid aqueous solution, ml; m0 is the mass of the liquid ammonia collection cylinder before absorption, g; m1 is the mass of the liquid ammonia collection cylinder after absorption, g; ρ is the density of liquid ammonia 0.68 g / mL.

Description

Technical Field

[0001] The invention belongs to the field of analytical chemistry, and in particular relates to an analytical method for hydrocarbon content in high-purity ammonia. Background Art

[0002] High-purity ammonia is an important raw material for semiconductors and the production of liquid crystal displays. It is also an important raw material for the production of electronic-grade gas NF 3As the main nitrogen source of high-purity ammonia, its purity directly affects the quality of the product, especially the content of hydrocarbons in high-purity ammonia has a great impact on the quality of the product. With the continuous development and expansion of the domestic semiconductor industry, the requirements for raw material high-purity ammonia are getting higher and higher. There are many methods for detecting organic compounds in high-purity ammonia, but most of them have some defects, such as the method specified in Part 6 of "GB / T 8570.6-2010 Determination of liquid anhydrous ammonia": oil content gravimetric method and infrared spectroscopy: by evaporating the liquid ammonia sample at room temperature, extracting the oil in the evaporation residue with carbon tetrachloride, heating and removing carbon tetrachloride, weighing the remaining residue, or measuring the absorbance of organic matter at a fixed wavelength of about 3.42μm to calculate the oil content in high-purity ammonia. The operation of this method is complicated, the error is large, and this method only quantifies the mixture, and does not perform single-substance qualitative and quantitative analysis on the organic matter in ammonia. In 2016, Chai Huiyu (Chai Huiyu, Zhao Zexiu, Liu Yang, et al. Discussion on the Improvement of the Analysis Method of Oil Content in Liquid Anhydrous Ammonia [J]. China High-tech Enterprise, 2016, 000(008): 31-33.) et al. reported "Discussion on the Improvement of the Analysis Method of Oil Content in Liquid Anhydrous Ammonia". This method improved the national standard GB / T 8570 by evaporating the liquid ammonia and washing the residue with anhydrous ethanol several times, and then using GC-MS for qualitative and quantitative analysis. However, the instruments used in this method are expensive and have high maintenance costs, and the sample is lost during the evaporation, transfer, and drying process. In 2013, Jin Xianghua et al. (Jin Xianghua, Li Heqing, Yan Haifeng, et al. Research on the determination method of oil content in anhydrous industrial liquid ammonia as ultra-pure ammonia raw material [C]. The Fourth Fifth Meeting of the National Technical Committee on Gas Standardization, the National Technical Committee on Semiconductor Equipment and Materials Standardization Gas Branch, the National Technical Committee on Standard Samples Gas Standard Sample Working Group, the First Fifth Joint Meeting of the National Technical Committee on Gas Standardization Analysis Branch.) reported on "Research on the determination method of oil content in anhydrous industrial liquid ammonia as ultra-pure ammonia raw material". The ultraviolet-visible spectrophotometry was used to analyze the oil in anhydrous industrial liquid ammonia, but the impurity content was lost during extraction and evaporation, and hydrocarbons that are gases at room temperature and pressure, such as methane, could not be qualitatively and quantitatively determined. In 2011, Fang Hua et al. (Fang Hua, Zhuang Hongtao, Yang Kang. Application of Helium Ion Chromatography in Ultra-High Purity Ammonia Analysis [C]. National Special Gas Annual Conference. China Industrial Gas Industry Association, 2011.) reported on "Application of Helium Ion Chromatography in Ultra-High Purity Ammonia Analysis". PDHID detector, ten-port valve injection, Porpak T as pre-column, 5A molecular sieve as analytical column were used to analyze impurities. However, the analysis of hydrocarbons was limited to CH4, and there was no corresponding method for C 2 -C 5 Analyze hydrocarbons.

[0003] Because the retention time of ammonia is close to that of ethane and propane when gas chromatography is used to detect hydrocarbons in ammonia, the peak area of ​​the main component ammonia on the chromatogram is too large, covering the peaks of ethane and propane, making it impossible to determine whether ammonia contains ethane and propane. Summary of the invention

[0004] The first technical problem to be solved by the present invention is to provide a method for analyzing the hydrocarbon content in high-purity ammonia. The method can determine whether the high-purity ammonia contains ethane and propane, and can also realize the qualitative and quantitative analysis of hydrocarbons. The detection method is intuitive, rapid and has good repeatability.

[0005] The second technical problem to be solved by the present invention is to provide a pretreatment device used in the method.

[0006] In order to solve the first technical problem, the present invention provides a method for analyzing the hydrocarbon content in high-purity ammonia, which is detected by a gas chromatograph equipped with a hydrogen flame ionization detector, comprising the following steps:

[0007] (1) Take liquid high-purity ammonia into a liquid ammonia collection cylinder;

[0008] (2) Before high-purity ammonia enters the gas chromatograph for analysis, it is pretreated by a pretreatment device:

[0009] The pretreatment device comprises a high-purity nitrogen cylinder 1, a liquid ammonia collection cylinder D, a flowmeter 4, a buffer bottle 7, an absorption bottle 8, a vacuum pump 10 and a syringe 11; the liquid ammonia collection cylinder D is equipped with a third needle valve A and a fourth needle valve B at the bottle mouth, and the liquid ammonia collection cylinder is connected in sequence to the fifth needle valve C-the second needle valve 6-the buffer bottle 7-the absorption bottle 8; the absorption bottle 8 is connected to the vacuum pump 10 and the syringe 11 through a pipeline three-way valve 9; the high-purity nitrogen cylinder 1 is connected in sequence to the pressure reducing valve 2-the first needle valve 3-the flowmeter 4-the emptying three-way valve 5-the buffer bottle 7.

[0010] 1) Prepare 200 mL of 1 mol / L dilute sulfuric acid aqueous solution and place it in an absorption bottle, then drop methyl orange solution into it;

[0011] 2) Weigh the mass of the liquid ammonia collection cylinder m 0 ;

[0012] 3) Use nitrogen to replace the gas in the pipeline between the nitrogen cylinder and the exhaust three-way valve;

[0013] 4) Use nitrogen to replace the gas in the pipeline between the flow meter and the vacuum pump;

[0014] 5) Use a vacuum pump to evacuate the gas in the syringe;

[0015] 6) Open the third needle valve A on the liquid ammonia collection cylinder to allow ammonia gas to enter the absorption bottle;

[0016] 7) When the color of the dilute sulfuric acid aqueous solution changes from orange-red to bright yellow, close the second needle valve and the third needle valve, and weigh the mass m of the liquid ammonia collection cylinder. 1 , and calculate the volume V of the absorbed liquid ammonia 1 ; V 1 =(m 0 -m 1 ) / ρ, ρ is the density of liquid ammonia 0.68 g / mL;

[0017] 8) Switch the exhaust three-way valve and the pipeline three-way valve to allow nitrogen to enter the syringe. Calculate the volume V of the mixed gas entering the syringe based on the syringe volume increment. 2 ;

[0018] (3) Analysis and Detection: The injector is connected to a gas chromatograph equipped with a hydrogen flame ionization detector for analysis. The hydrocarbon content in the injector gas is w 0 ;

[0019] Hydrocarbon content in high purity ammonia 1 =w 0 (V 2 +V 吸空 ) / V 1

[0020] V 1 =(m 0 -m 1 ) / ρ

[0021] where w 0 is the hydrocarbon content of the gas in the syringe, ppm; V 2 V is the volume of the mixed gas entering the syringe, ml; 吸空 V is the volume of the absorption bottle minus the volume of the dilute sulfuric acid solution, ml; 1 is the volume of high-purity ammonia absorbed in dilute sulfuric acid aqueous solution, ml; m 0 The mass of the liquid ammonia collection cylinder before absorption, g; m 1 is the mass of the liquid ammonia collection cylinder after absorption, g; ρ is the density of liquid ammonia 0.68 g / mL.

[0022] Furthermore, the capacity of the liquid ammonia collection cylinder in step (1) is preferably 1000 mL;

[0023] Furthermore, the syringe preferably has a volume of 100 ml and is made entirely of glass;

[0024] The test conditions of the gas chromatograph in step (3) are as follows: the chromatographic column is porapak Q, the initial temperature of the column box is 110°C and maintained for 7.8 min, then increased to 150°C at a heating rate of 70°C / min and maintained for 21 min, the detector temperature is 250°C, the column flow rate is 16 ml / min, and the carrier gas is ultrapure helium with a pressure of 0.56 MPa.

[0025] To solve the second technical problem, the present invention provides a pretreatment device, including a high-purity nitrogen cylinder 1, a liquid ammonia collection cylinder D, a flow meter 4, a buffer bottle 7, an absorption bottle 8, a vacuum pump 10 and a syringe 11; the mouth of the liquid ammonia collection cylinder D is equipped with a third needle valve A and a fourth needle valve B, and the liquid ammonia collection cylinder is connected in sequence to the fifth needle valve C-the second needle valve 6-the buffer bottle 7-the absorption bottle 8; the absorption bottle 8 is connected to the vacuum pump 10 and the syringe 11 through a pipeline three-way valve 9; the high-purity nitrogen cylinder 1 is connected in sequence to the pressure reducing valve 2-the first needle valve 3-the flow meter 4-the emptying three-way valve 5-the buffer bottle 7.

[0026] Furthermore, the flow meter is preferably a rotor flow meter, the three-way exhaust valve is a three-way ball valve, and the three-way pipeline valve is a three-way ball valve.

[0027] The analytical method of the present invention adds a gas pretreatment device, absorbs ammonia, and then quantifies the single components of methane, ethane, propane, n-butane, and n-pentane in high-purity ammonia through a gas chromatograph equipped with a hydrogen flame ionization detector, thereby solving the problem that the ammonia peak covers the ethane and propane peaks, making it impossible to determine whether ethane and propane are contained, and unable to quantitatively analyze ethane and propane; at the same time, it solves the single qualitative and quantitative problems of methane, ethane, propane, n-butane, and n-pentane in high-purity ammonia. At the same time, after the ammonia is pretreated, the corrosion of the hydrogen flame ionization detector by ammonia can be avoided, thereby extending the service life of the gas chromatograph, avoiding ammonia pollution of the atmosphere, and playing an environmental protection role. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the pretreatment device before liquid ammonia analysis of the present invention.

[0029] Figure 2 This is a schematic diagram of the liquid ammonia sampling connection of the present invention.

[0030] Figure 3 The figure is a chromatogram of analyzing high-purity ammonia by the method of the present invention.

[0031] Figure 4 The chromatogram of the mixed gas of high-purity ammonia and standard gas analyzed by the method of the present invention.

[0032] Figure 5 This is a chromatogram of directly analyzing high-purity ammonia gas without passing through the pretreatment device of the present invention.

[0033] Figure 6 For the mixed standard gas (CH 4 , C 2 H 6 , C 3 H 8 , C 4 H 10 , C 5 H 12 The content of each sample is 10 ppm).

[0034] Among them: 1. High-purity nitrogen cylinder 2. Pressure reducing valve 3. First needle valve 4. Flow meter 5. Empty three-way valve 6. Second needle valve 7. Buffer bottle 8. Absorption bottle 9. Pipe three-way valve 10. Vacuum pump 11. Syringe 12. Liquid ammonia container 13. Liquid phase valve of liquid ammonia container 14. Connecting pipe 15. Sixth needle valve A. Third needle valve B. Fourth needle valve C. Fifth needle valve D. Liquid ammonia collection cylinder DETAILED DESCRIPTION

[0035] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0036] Example 1

[0037] A method for analyzing hydrocarbon content in high-purity ammonia comprises the following steps:

[0038] (1) Sampling of liquid high-purity ammonia

[0039] 1) Pour an appropriate amount of industrial alcohol into a Dewar flask, inject liquid nitrogen into it, stir while injecting, and stop injecting liquid nitrogen when the alcohol cools to a paste;

[0040] 2) Place the liquid ammonia collection cylinder into the Dewar flask in step 1) above and cool for 15 minutes;

[0041] 3) If Figure 2 As shown, one end of the connecting pipe is tightly connected to the liquid phase valve of the liquid ammonia container, and the other end is connected to the third needle valve A; before opening the liquid phase valve of the liquid ammonia container, first open the sixth needle valve to communicate with the atmosphere;

[0042] 4) If Figure 2 As shown, carefully open the liquid phase valve of the liquid ammonia container to let the liquid ammonia flow out, discharge the air in the connecting pipe through the sixth needle valve, and after the sampling tube is purified by the free flow of liquid ammonia, close the sixth needle valve, open the third needle valve, and let the liquid ammonia flow into the liquid ammonia collection cylinder to the specified safe filling volume. Close the third needle valve and the liquid phase valve of the liquid ammonia container, open the sixth needle valve, and after the liquid ammonia in the connecting pipe is discharged, remove the liquid ammonia collection cylinder;

[0043] 5) Use a balance to weigh the mass m of the liquid ammonia collection cylinder after sampling0 =7125g.

[0044] (2) Pretreatment before chromatography

[0045] 1) Prepare 200 mL of 1 mol / L dilute sulfuric acid aqueous solution and place it in an absorption bottle, then add two drops of methyl orange solution;

[0046] 2) If Figure 1 As shown, switch the three-way valve of the evacuation to the displacement evacuation side, open the main valve of high-purity nitrogen, pressurize the pressure reducing valve to 0.1MPa-0.2MPa, adjust the first needle valve to make the flow meter 4 at a flow rate of 20mL / min, and maintain the displacement for 2min;

[0047] 3) Cut the three-way valve of the pipeline to the absorption bottle side, cut the emptying three-way valve to the sampling pipeline, adjust the first needle valve to make the flow meter flow rate at 100mL / min, replace the pipeline for 2 minutes, and then close the emptying three-way valve;

[0048] 4) Cut the three-way ball valve of the pipeline to the vacuum pump side. At this time, the gas in the syringe is evacuated and discharged. After evacuation, cut the three-way ball valve of the pipeline to the absorption bottle side;

[0049] 5) Slowly open the third needle valve to allow ammonia in the liquid ammonia collection cylinder to escape into the absorption bottle, and adjust the second needle valve to control the escape speed;

[0050] 6) When the color of the solution in the absorption bottle changes from orange-red to bright yellow, close the second needle valve and the third needle valve, and weigh the weight of the liquid ammonia collection cylinder m 1 = 6617g, calculate the volume V of liquid ammonia discharged from the liquid ammonia collection cylinder 1 =747.06ml;

[0051] 7) If Figure 1 As shown, the three-way ball valve is cut to the sampling line, and high-purity nitrogen is introduced at a flow rate of 20 mL / min. The volume V of the mixed gas entering the syringe is calculated based on the syringe volume increment. 2 =25ml;

[0052] 8) Connect the syringe to a gas chromatograph equipped with a hydrogen flame ionization detector (FID-GC) for analysis. The test results are shown in the attached Figure 3 After ammonia was absorbed by the pretreatment device, no peak appeared on the chromatogram, indicating that ammonia had been completely absorbed by the pretreatment device. The methane content in the injector gas was detected to be w 0 =1.0ppm, V 吸空 =300ml, V 1 =(m 0 -m 1) / ρ=(7125-6617) / 0.68=747.06ml, high purity ammonia contains only methane w 1 =w 0 (V 2 +V 吸空 ) / V 1 =0.44ppm.

[0053] Example 2

[0054] (1) Prepare ammonia-standard gas mixture

[0055] High-purity ammonia and standard gas (CH 4 , C 2 H 6 , C 3 H 8 , C 4 H 10 , C 5 H 12 The content of both was 10ppm) was introduced into an aluminum foil bag in a certain proportion and mixed thoroughly to prepare an ammonia-standard gas mixture of unknown concentration.

[0056] (2) Pretreatment before chromatography

[0057] 1) Prepare 200 mL of 1 mol / L dilute sulfuric acid aqueous solution and place it in an absorption bottle, then add two drops of methyl orange solution;

[0058] 2) Figure 1 The liquid ammonia collection cylinder is replaced with an aluminum foil bag of ammonia-standard gas mixture;

[0059] 3) If Figure 1 As shown, switch the three-way valve of the evacuation to the displacement evacuation side, open the main valve of high-purity nitrogen, pressurize the pressure reducing valve to 0.1MPa-0.2MPa, adjust the first needle valve to make the flow meter 4 at a flow rate of 20mL / min, and maintain the displacement for 2min;

[0060] 4) Cut the three-way valve of the pipeline to the absorption bottle side, cut the emptying three-way valve to the sampling pipeline, adjust the first needle valve to make the flow meter flow rate at 100mL / min, replace the pipeline for 2 minutes, and then close the emptying three-way valve;

[0061] 5) Cut the three-way ball valve of the pipeline to the vacuum pump side. At this time, the gas in the syringe is evacuated and discharged. After evacuation, cut the three-way ball valve of the pipeline to the absorption bottle side;

[0062] 6) Slowly open the third needle valve to allow ammonia in the liquid ammonia collection cylinder to escape into the absorption bottle, and adjust the second needle valve to control the escape speed;

[0063] 7) When the color of the solution in the absorption bottle changes from orange-red to bright yellow, close the second needle valve and the third needle valve.

[0064] 8) If Figure 1 As shown, the evacuation three-way ball valve is cut to the sampling line, and high-purity nitrogen is introduced at a flow rate of 20 mL / min. The nitrogen volume V is calculated according to the syringe volume increment. 2 =25ml;

[0065] 9) Connect the syringe to the FID-GC for analysis. The test results are as shown in the attached Figure 4 After ammonia is absorbed by the pretreatment device, no peak appears on the chromatogram. The methane content in the injector gas is detected to be 9.02ppm, the ethane content is 8.73ppm, the propane content is 9.45ppm, the n-butane content is 9.45ppm, and the n-pentane content is 7.92ppm. The peaks of methane, ethane, propane, n-butane, and n-pentane on the chromatogram are normal. The present invention can be used to detect the contents of ethane, propane, n-butane, and n-pentane in addition to methane in high-purity ammonia.

[0066] Comparative Example 1

[0067] Connect the liquid ammonia collection cylinder directly to the FID-GC for detection. The analysis steps are as follows:

[0068] 1) Connect the liquid ammonia collection cylinder directly to the FID-GC and adjust the inlet flow rate to 20ml / min. The analysis results are shown in the attached Figure 5 ;

[0069] 2) Place the mixed standard gas cylinder (CH 4 , C 2 H 6 , C 3 H 8 , C 4 H 10 , C 5 H 12 The content is 10ppm) connected to FID-GC, the inlet flow rate was adjusted to 20ml / min, and the analysis results are shown in the attached Figure 6 ;

[0070] From the chromatogram of the mixed standard gas (attached Figure 6 ) It can be seen that the retention time of ethane is 2.707min, the retention time of propane is 7.015min, and the peaks of ethane and propane on the chromatogram are covered by the ammonia peak (see attached Figure 5 ), so it is impossible to determine whether the ammonia contains ethane and propane. The methane content in this bottle of high-purity liquid ammonia was 0.44ppm when the ammonia was directly detected by FID-GC without pretreatment.

[0071] Table 1 Detection results of hydrocarbon content in ammonia gas of the embodiment and the comparative example

[0072]

Claims

1. A method for analyzing the hydrocarbon content in high-purity ammonia, using a gas chromatograph equipped with a hydrogen flame ionization detector for detection, comprising the following steps: (1) Take liquid high-purity ammonia into a liquid ammonia collection cylinder; (2) Before high-purity ammonia enters the gas chromatograph for analysis, it is pretreated by a pretreatment device: The pretreatment device comprises a high-purity nitrogen cylinder (1), a liquid ammonia collection cylinder (D), a flow meter (4), a buffer bottle (7), an absorption bottle (8), a vacuum pump (10) and a syringe (11); the mouth of the liquid ammonia collection cylinder (D) is equipped with a third needle valve (A) and a fourth needle valve (B), and the liquid ammonia collection cylinder is connected in sequence to a fifth needle valve (C) - a second needle valve (6) - a buffer bottle (7) - an absorption bottle (8); the absorption bottle (8) is connected to a vacuum pump (10) and a syringe (11) via a pipeline three-way valve (9); the high-purity nitrogen cylinder (1) is connected in sequence to a pressure reducing valve (2) - a first needle valve (3) - a flow meter (4) - an emptying three-way valve (5) - a buffer bottle (7); 1) Prepare 200 mL of 1 mol / L dilute sulfuric acid aqueous solution and place it in an absorption bottle, then drop methyl orange solution into it; 2) Weigh the mass m0 of the liquid ammonia collection cylinder; 3) Use nitrogen to replace the gas in the pipeline between the nitrogen cylinder and the exhaust three-way valve; 4) Use nitrogen to replace the gas in the pipeline between the flow meter and the vacuum pump; 5) Use a vacuum pump to evacuate the gas in the syringe; 6) Open the third needle valve A on the liquid ammonia collection cylinder to allow ammonia gas to enter the absorption bottle; 7) When the color of the dilute sulfuric acid aqueous solution changes from orange-red to bright yellow, close the second needle valve and the third needle valve, weigh the mass m1 of the liquid ammonia collection cylinder, and calculate the volume V1 of the absorbed liquid ammonia; V1 = (m0-m1) / ρ, ρ is the density of liquid ammonia 0.68 g / mL; 8) Switch the exhaust three-way valve and the pipeline three-way valve to allow nitrogen to enter the syringe, and calculate the volume V2 of the mixed gas entering the syringe based on the syringe volume increment; (3) Analysis and Detection The injector is connected to a gas chromatograph equipped with a hydrogen flame ionization detector for analysis, and the hydrocarbon content in the injector gas is detected as w0; The hydrocarbon content in high-purity ammonia is w1=w0(V2+V 吸空 ) / V1 V1=(m0-m1) / ρ Where w0 is the hydrocarbon content of the gas in the syringe, ppm; V2 is the volume of the mixed gas entering the syringe, ml; V 吸空 is the volume of the absorption bottle minus the volume of the dilute sulfuric acid solution, ml; V1 is the volume of high-purity ammonia absorbed in the dilute sulfuric acid aqueous solution, ml; m0 is the mass of the liquid ammonia collection cylinder before absorption, g; m1 is the mass of the liquid ammonia collection cylinder after absorption, g; ρ is the density of liquid ammonia 0.68 g / mL.

2. The analytical method according to claim 1, characterized in that The capacity of the liquid ammonia collection cylinder in step (1) is 1000 mL.

3. The analytical method according to claim 1, characterized in that The syringe has a volume of 100 ml and is made entirely of glass.

4. The analytical method according to claim 1, characterized in that The test conditions of the gas chromatograph in step (3) are as follows: the chromatographic column is porapak Q, the initial temperature of the column box is 110°C and maintained for 7.8 min, then the temperature is increased to 150°C at a heating rate of 70°C / min and maintained for 21 min, the detector temperature is 250°C, the column flow rate is 16 ml / min, and the carrier gas is ultrapure helium with a pressure of 0.56 MPa.

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