A device for separating and purifying nitrogen and oxygen and a method for separating and purifying nitrogen and oxygen

Abstract

The invention discloses a device for separating and purifying nitrogen and oxygen and a separation and purification method. Ultrapure helium is connected to a system after passing through a cold trap equipped with a 13X molecular sieve, a water-cooled trap is connected to a vacuum gauge that can measure the amount of sample after the sample injection device is connected, and a sample transfer and collection cold trap equipped with silica gel is connected to the water-cooled well after the sample injection well, and a chromatographic column and a detector are connected to the cold trap in sequence. The detector is connected to a nitrogen and oxygen collection cold trap and an exhaust valve, and the rear end of the cold trap is connected to a sample collection device. The invention can realize one-time injection and complete the separation of nitrogen and oxygen at the same time, and can be applied to the treatment of gas samples in solids, gases and liquids. In order to achieve high-purity separation of nitrogen and oxygen and avoid air pollution, the entire circuit does not use a four-way valve with poor air tightness, but all uses a ferrule interface pneumatic valve / manual valve with better air tightness.

Description

Technical Field

[0001] The invention belongs to the technical field of gas isotope analysis and testing, and relates to a device and method for separating and purifying nitrogen and oxygen in a sample by using a cold trap and a chromatographic column to complete isotope testing. Background Art

[0002] Nitrogen and oxygen are widely present on Earth, with nitrogen accounting for 78.1% of the atmosphere and oxygen accounting for 20.9% of the atmosphere. As the main components of the atmosphere, nitrogen and oxygen participate in atmospheric processes, biological processes, and geological processes, and are widely used in earth science and life science research. The study of nitrogen and oxygen cluster isotopes is an emerging direction that has developed in recent years. Since cluster isotope testing, especially nitrogen cluster isotope testing, has relatively high sample purity requirements, oxygen is mixed into nitrogen, and the instrument will produce 14 N 16 O(mass number: 29.99799), interference 15 N 15 N (mass number: 30.00022). If one ten-thousandth of oxygen is mixed into nitrogen, it will cause 15 N 15 N produces a deviation of ~1‰. In addition, due to the distinction 12 C 18 O (mass number 29.99916) and 15 N 15 N (mass number: 30.00022) requires a resolution of ~80,000, so ultrapure nitrogen samples are required to test the isotope composition of nitrogen clusters. The existing technology for separating nitrogen, oxygen and carbon dioxide in the atmosphere (nitrogen, oxygen, carbon dioxide isotope sampling and analysis device and method in the atmosphere, patent number: CN 111157303A) does not have the ability to process dissolved gas samples, and because the device uses a six-way valve with poor air tightness (poor air tightness), the separated and purified nitrogen will contain a very small amount of oxygen, which cannot meet the requirements of cluster isotope testing. In addition, the gas sample collection process is very cumbersome, and the isotope composition of oxygen and nitrogen in the collected samples will change due to leakage, biological activities, etc. when the samples are stored for a long time, leaving a very short effective time for analysis and testing. Therefore, how to efficiently and quickly separate nitrogen and oxygen from the sample at one time and meet the requirements of cluster isotope analysis and testing is a technical problem that needs to be solved urgently. Summary of the invention

[0003] The present invention is aimed at gas samples and dissolved gas samples in water that cannot separate and extract nitrogen and oxygen at the same time. The existing methods can only separate nitrogen or oxygen, and the purity of the separated nitrogen is not enough to meet the cluster isotope analysis test requirements. The present invention provides a device for separating and purifying nitrogen and oxygen, and develops a gas separation and purification method based on the device. The method simultaneously realizes the separation and purification of oxygen and nitrogen in purified gas, liquid and solid samples, and meets the test requirements of high-precision cluster isotopes.

[0004] The technical scheme adopted by the present invention is: a device for separating and purifying nitrogen and oxygen, comprising a vacuum gauge, a sample injection tube, a magnesium perchlorate water removal trap, a dissolved gas sample bottle, an ultrapure helium pipeline, a water removal cold trap, a helium purification cold trap, a cold trap, a chromatographic column, a chromatograph detector, a nitrogen collection cold trap, a nitrogen sample tube, an oxygen collection cold trap, an oxygen sample tube and a valve;

[0005] The ultrapure helium pipeline is connected to two quarter-inch helium purification cold traps filled with 13X molecular sieves. The two helium purification cold traps are isolated by valves. After passing through the helium purification cold traps, the helium is divided into five paths. The helium pipelines are connected with one-eighth-inch helium pipelines:

[0006] One of the paths is connected to the water-removing cooling trap through a valve, the water-removing cooling trap is connected to the interface of the solid fracturing device through a valve, and the water-removing cooling trap is connected to the vacuum gauge through a valve, and the range of the vacuum gauge is 0 to 1000 torr;

[0007] Two-way access to a cold trap filled with silica gel, the dewatering cold trap is connected to the cold trap through a valve;

[0008] The three routes are connected to the cold trap through valves, and the cold trap is connected to a chromatographic column filled with 80 mesh 5A molecular sieve;

[0009] Four-way access to a chromatographic detector (TCD), wherein the chromatographic column is connected to the chromatographic detector, and the chromatographic detector is connected to a one-sixteenth-inch metal coil through a valve and then passes air;

[0010] The five routes are connected to the four-way through the valve, and the other three routes of the four-way are: connected to the chromatograph detector through the valve, connected to the nitrogen collection cold trap through the valve, and connected to the oxygen collection cold trap through the valve; the nitrogen collection cold trap and the oxygen collection cold trap are filled with 13X molecular sieve; the nitrogen collection cold trap is connected to a nitrogen sample tube filled with silica gel through the valve, and the nitrogen collection cold trap is connected to a one-sixteenth inch metal coil through the valve and then air is passed; the oxygen collection cold trap is connected to an oxygen sample tube filled with silica gel through the valve, and the oxygen collection cold trap is connected to a one-sixteenth inch metal coil through the valve and then air is passed; the nitrogen collection cold trap and the oxygen collection cold trap are connected to a vacuum gauge through the valve, and the vacuum gauge range is 0-100 torr;

[0011] The ultrapure helium pipeline is connected to the dissolved gas sample bottle through a valve, the dissolved gas sample bottle is connected to the magnesium perchlorate dewatering trap through a valve, and the magnesium perchlorate dewatering trap is connected to the interface of the solid fracturing device through a valve; the sampling sample tube is connected to the device for separating and purifying nitrogen and oxygen through a valve;

[0012] The device for separating and purifying nitrogen and oxygen is connected to the dry pump interface, the vacuum gauge, and the molecular pump interface through a valve;

[0013] All valves are connected with quarter-inch vacuum metal tubing.

[0014] Preferably, all valves and vacuum lines are connected by metal ferrules.

[0015] Preferably, all sample tubes and vacuum lines are connected using Swagelok Ultra-torr connections.

[0016] Preferably, all metal valves are Swagelok valves and glass valves are Kimble valves.

[0017] Preferably, the helium used is ultrapure helium (purity 99.9999%).

[0018] The ultrapure helium of the present invention is connected to the system after passing through a cold trap equipped with 13X molecular sieve, a water-cooled trap is connected after the sample injection device, a vacuum gauge capable of measuring the amount of the sample is connected to the water-cooled trap, a sample transfer and collection cold trap equipped with silica gel is connected after the water-cooled well, and a chromatographic column and a detector are connected to the cold trap in sequence. A nitrogen and oxygen collection cold trap and an exhaust valve are connected after the detector, and a sample collection device is connected to the rear end of the cold trap. The whole system uses two dry pumps and a molecular pump to provide vacuum.

[0019] The separation and purification method using the above-mentioned device for separating and purifying nitrogen and oxygen comprises the following steps:

[0020] Step 1: Turn on the chromatograph detector to preheat, remove the water-cooled trap and cover the cold trap with liquid nitrogen, and maintain it for 10 minutes while collecting the oxygen cold trap and heating it to purify the helium;

[0021] Step 2: Place the sample gas into the water-removing cold trap, read the vacuum gauge reading, cover the water-removing cold trap with liquid nitrogen, and wait for 5 minutes to remove water and carbon dioxide;

[0022] Step 3: Cover the cold trap with liquid nitrogen for 5 minutes and transfer the sample to the cold trap;

[0023] Step 4: Maintain for 30 seconds to replenish the cold trap helium;

[0024] Step 5: Freeze the chromatographic column with alcohol liquid nitrogen and remove the cold trap liquid nitrogen;

[0025] Step 5: After the oxygen peak appears, collect the oxygen in an oxygen cold trap;

[0026] Step 6: After oxygen is collected, remove the alcohol liquid nitrogen from the chromatographic column. When the nitrogen signal appears, switch the valve to collect the sample in the nitrogen cold trap.

[0027] Step 7: Transfer the sample gas to the sample tube and then to the mass spectrometer to test the isotopic composition.

[0028] Beneficial effects:

[0029] 1. The device of the present invention can achieve one-time sampling and complete the separation of nitrogen and oxygen at the same time, and can be applied to the treatment of gas samples in solids, gases and liquids. 2. In order to achieve high-purity separation of nitrogen and oxygen and avoid air pollution, the entire circuit does not use a four-way valve with poor air tightness, but all uses a ferrule interface pneumatic valve / manual valve with better air tightness. 3. The carrier gas uses ultra-high purity helium, which effectively reduces the background, realizes the separation and purification of high-purity oxygen and nitrogen, and meets the testing requirements of cluster isotopes. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is the circuit diagram of the device of the present invention;

[0031] Figure 2 is a chromatogram of an air sample separated by the present invention, showing peaks of argon, oxygen and nitrogen respectively;

[0032] Figure 3 The isotope test results of nitrogen clusters separated and purified by the device and method. The square icon represents the test results of nitrogen produced by heating strontium nitride catalysis, the solid circle represents nitrogen produced by heating ammonium dichromate decomposition, the triangle represents nitrogen produced by heating potassium azide, the hexagon represents laboratory standard gas, the diamond represents nitrogen in the air, and the five-pointed star represents the dissolved gas in lake water;

[0033] In the figure, 1 is a quarter-inch vacuum metal tube, 2 is a dry pump interface, 3 is a vacuum gauge, 4 is a molecular pump interface, 5 is a solid fracturing device interface, 6 is an injection sample tube, 7 is a magnesium perchlorate water removal trap, 8 is a dissolved gas sample bottle, 9 is an ultrapure helium pipeline, 10 is a water removal cold trap, 11 is a helium purification cold trap, 12 is a cold trap, 13 is a chromatographic column, 14 is a chromatograph detector, 15 is a one-eighth-inch helium pipeline, 16 is a nitrogen collection cold trap, 17 is a nitrogen sample tube, 18 is an oxygen collection cold trap, 19 is an oxygen sample tube, 20 is a one-sixteenth-inch metal coil, 21 is a vacuum gauge, 22 is a vacuum gauge, and 23 to 56 are valves. DETAILED DESCRIPTION

[0034] The method for separating nitrogen and oxygen in a sample by using chromatography + cold trap according to the present invention is further described below by way of examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. The technical personnel in the relevant field make some non-essential improvements and adjustments to the present invention according to the above invention content for specific implementation, which still falls within the scope of protection of the present invention.

[0035] In the following examples, the laboratory temperature was 22°C.

[0036] like Figure 1-3 As shown, in this embodiment, the separation and purification of nitrogen and oxygen in an air sample is taken as an example to illustrate the process of obtaining the method of the present invention, and on this basis, the method of the present invention for separating and purifying nitrogen and oxygen by using chromatography + cold trap is described in detail.

[0037] A device for separating and purifying nitrogen and oxygen.

[0038] The ultrapure helium pipeline 9 is connected to two 1 / 4 inch helium purification cold traps 11 filled with 13X molecular sieves. The two helium purification cold traps 11 are isolated by valves 38, 39, 40, and 41. After passing through the helium purification cold traps 11, the helium is divided into five paths. The helium pipelines are connected with a one-eighth inch helium pipeline 15:

[0039] One of the paths is connected to the water removal cooling trap 10 through valve 31 and before valve 33, the water removal cooling trap 10 is connected to the solid fracturing device interface 5 through valves 27 and 23, and the water removal cooling trap 10 is connected to the vacuum gauge 22 through valve 28, and the range of the vacuum gauge 22 is 0 to 1000 torr;

[0040] Before the two-way access to the cold trap 12 filled with silica gel, it is connected between valve 34 and valve 36, and the water removal cold trap 10 is connected to the cold trap 12 through valve 33;

[0041] The three routes are connected to the rear end of the cold trap 12 and below the valve 35 through the valve 37, and the cold trap 12 is connected to the chromatographic column 13 filled with 80 mesh 5A molecular sieve;

[0042] The chromatographic detector 14 (TCD) is connected to the chromatographic column 13, and the chromatographic detector 14 is connected to a 1 / 16-inch metal coil through a valve 42 and then passes air;

[0043] The five-way is connected to the four-way after the valve 43 through the valve 44, and the other three ways of the four-way are: connected to the chromatograph detector 14 through the valve 43, connected to the nitrogen collection cold trap 16 through the valve 45, and connected to the oxygen collection cold trap 18 through the valve 47; the nitrogen collection cold trap 16 and the oxygen collection cold trap 18 are filled with 13X molecular sieve; the nitrogen collection cold trap 16 is connected to the nitrogen sample tube 17 filled with silica gel through the valve 48 and the valve 49, and the nitrogen collection cold trap 16 is connected to the 1 / 16 inch metal coil through the valve 46 and then the air is passed; the oxygen collection cold trap 18 is connected to the oxygen sample tube 19 filled with silica gel through the valve 51 and the valve 52, and the oxygen collection cold trap 18 is connected to the 1 / 16 inch metal coil 20 through the valve 50 and then the air is passed; the nitrogen collection cold trap 16 and the oxygen collection cold trap 18 are connected to the vacuum gauge 21 through the valve 53, and the range of the vacuum gauge 21 is 0-100 torr;

[0044] The ultrapure helium pipeline 9 is connected to the dissolved gas sample bottle 8 through the valve 32, the dissolved gas sample bottle 8 is connected to the magnesium perchlorate dewatering trap 7 through the valve 29, the magnesium perchlorate dewatering trap 7 is connected to the system through the valve 25, and the valve 23 is connected to the solid fracturing device interface 5; the sampling tube 6 is connected to the device for separating nitrogen, oxygen and argon through the valve 24;

[0045] The device for separating nitrogen, oxygen and argon is connected to the dry pump interface 2, the vacuum gauge 3 and the molecular pump interface 4 through valve 26, valve 30, valve 54, valve 55 and valve 56;

[0046] All valves are connected by a quarter-inch vacuum metal tube 1.

[0047] All valves and vacuum lines are connected by metal ferrules. All sample tubes and vacuum lines are connected by Swagelok Ultra-torr. All metal valves are Swagelok valves, and all glass valves are Kimble valves. The helium used is ultra-pure helium (purity 99.9999%).

[0048] The method for separating nitrogen and oxygen using a cold trap + chromatographic column (GC) provided by the present invention, taking the separation of nitrogen and oxygen in gas as an example, comprises the following steps:

[0049] (1) Turn on the chromatograph detector 14, cover the water-removing cold trap 10 and the cold trap 12 with liquid nitrogen, and preheat for two hours; open valves 26, 27, 30, 48, 33, 51, 54, and 56, and evacuate the vacuum line to 3×10 - 5 mbar.

[0050] (2) Close valves 26 and 30, cover cold trap 10 with liquid nitrogen, open valve 24, put sample gas into the vacuum line, read the degree of vacuum gauge 22, stay for 5 minutes, and record the change of the reading of vacuum gauge 22.

[0051] (3) Put liquid nitrogen on the cold trap 12, open valve 33, read the reading of the vacuum gauge 22 after 5 minutes, and close valve 33; open valve 37 and keep it for 30 seconds, then close valve 37.

[0052] (4) Cover the chromatographic column 13 with a -80°C freezing liquid (alcohol liquid nitrogen); remove the liquid nitrogen in the cold trap 12, open valves 34 and 35 after four minutes, close valve 36, and start testing the chromatograph detector 14. After six minutes, close valves 34 and 35, and open valve 36; observe the changes in the chromatograph peak shape.

[0053] (5) After the argon peak appears, open valves 44 and 45, collect the nitrogen cold trap 16 and cover it with liquid nitrogen. Two minutes later, open valve 50. When the oxygen peak appears, close valves 42 and 44, and open valve 43. After 5 minutes after the oxygen peak appears, close valves 46, 45, and 43, and open valve 42.

[0054] (6) Remove the freezing liquid from the chromatographic column and restore it to room temperature; collect the oxygen cold trap 18 and cover it with liquid nitrogen; open valve 44 and valve 47, and open valve 50 after two minutes.

[0055] (7) After the nitrogen peak appears in the chromatogram, close valves 42 and 44, and open valve 43; five minutes after the nitrogen peak appears, close valves 50, 47, and 43 in turn, and open valve 42; the chromatograph stops collecting data and exports the spectrum.

[0056] (8) Open valve 54, valve 48, and valve 51, and use a vacuum pump to extract the helium; close valve 54; remove the liquid nitrogen from the nitrogen cold trap 16 to release the oxygen; after five minutes, read the reading of the vacuum gauge 21, open valve 49, freeze the silica gel in the sample tube with liquid nitrogen, transfer the sample to the sample tube, close valve 49, and wait for the mass spectrometer to test the isotope composition.

[0057] (9) Close valve 54, open valve 51, remove the oxygen collecting cold trap 18, read the vacuum gauge 21 after five minutes, open valve 52, cover the sample tube with liquid nitrogen, transfer the nitrogen sample to the sample tube, close valve 52, and wait for the mass spectrometer to test the isotope composition.

[0058] (10) Turn on the water removal cold trap 10, the nitrogen collection cold trap 16, the oxygen collection cold trap 18 and the heating of the chromatographic column 13, open valve 27, valve 28, valve 30, valve 33, valve 48, valve 51 and valve 54, evacuate the vacuum line with a vacuum pump, and prepare for the next sample.

[0059] (11) After completing the sample preparation each day, remove the liquid nitrogen from the helium-purified cold trap 11, heat it up and bake it out, and use helium to blow away the impurities such as water, nitrogen, and oxygen adsorbed by the molecular sieve of the cold trap.

[0060] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and deformations of these embodiments within the scope of the principles and technical ideas of the present invention still fall within the protection scope of the present invention.

Claims

1. A device for separating and purifying nitrogen and oxygen, characterized in that: Including vacuum gauge, injection sample tube, magnesium perchlorate dewatering trap, dissolved gas sample bottle, ultrapure helium pipeline, dewatering cold trap, helium purification cold trap, cold trap, chromatographic column, chromatographic detector, nitrogen collection cold trap, nitrogen sample tube, oxygen collection cold trap, oxygen sample tube and valve; The ultrapure helium pipeline is connected to two quarter-inch helium purification cold traps filled with 13X molecular sieves. The two helium purification cold traps are isolated by valves. After passing through the helium purification cold traps, the helium is divided into five paths. The helium pipelines are connected with one-eighth-inch helium pipelines: One of the paths is connected to the water-removing cooling trap through a valve, the water-removing cooling trap is connected to the interface of the solid fracturing device through a valve, and the water-removing cooling trap is connected to the vacuum gauge through a valve, and the range of the vacuum gauge is 0~1000 torr; Before the two-way access to the cold trap filled with silica gel, the water-removing cold trap is connected to the cold trap through a valve; The three routes are connected to the rear end of the cold trap through valves, and the cold trap is connected to a chromatographic column filled with 80 mesh 5A molecular sieve; Four-way access to a chromatograph detector, the chromatograph detector is a TCD, the chromatographic column is connected to the chromatograph detector, and the chromatograph detector is connected to a one-sixteenth-inch metal coil through a valve and then passes air; The five routes are connected to the four-way through the valve, and the other three routes of the four-way are: connected to the chromatograph detector through the valve, connected to the nitrogen collection cold trap through the valve, and connected to the oxygen collection cold trap through the valve; the nitrogen collection cold trap and the oxygen collection cold trap are filled with 13X molecular sieves; the nitrogen collection cold trap is connected to a nitrogen sample tube filled with silica gel through the valve, and the nitrogen collection cold trap is connected to a one-sixteenth inch metal coil through the valve and then air is passed; the oxygen collection cold trap is connected to an oxygen sample tube filled with silica gel through the valve, and the oxygen collection cold trap is connected to a one-sixteenth inch metal coil through the valve and then air is passed; the nitrogen collection cold trap and the oxygen collection cold trap are connected to a vacuum gauge through the valve, and the vacuum gauge range is 0~100 torr; The ultrapure helium pipeline is connected to the dissolved gas sample bottle through a valve, the dissolved gas sample bottle is connected to the magnesium perchlorate dewatering trap through a valve, and the magnesium perchlorate dewatering trap is connected to the interface of the solid fracturing device through a valve; the injection sample tube is connected to the device for separating and purifying nitrogen and oxygen through a valve; the injection device is connected to a dewatering cooling trap; The device for separating and purifying nitrogen and oxygen is connected to the dry pump interface, the vacuum gauge, and the molecular pump interface through a valve; All valves are connected with quarter-inch vacuum metal tubing.

2. The device for separating and purifying nitrogen and oxygen according to claim 1, characterized in that: All valves and vacuum lines are connected by metal ferrules.

3. The device for separating and purifying nitrogen and oxygen according to claim 1, characterized in that: All sample tubes and vacuum lines were connected using Swagelok Ultra-torr.

4. The device for separating and purifying nitrogen and oxygen according to claim 1, characterized in that: Valves are Swagelok metal valves or Kimble glass valves.

5. The device for separating and purifying nitrogen and oxygen according to claim 1, characterized in that: The helium used is ultra-pure helium with a purity of 99.9999%.

6. A separation and purification method using the device for separating and purifying nitrogen and oxygen according to claim 1, 2, 3, 4 or 5, characterized in that: The following steps are involved: Step 1: Turn on the chromatograph detector to preheat, remove the water-cooled trap and cover the cold trap with liquid nitrogen, and maintain it for 10 minutes while collecting the oxygen cold trap and heating it to purify the helium; Step 2: Place the sample gas into the water-removing cold trap, read the vacuum gauge reading, cover the water-removing cold trap with liquid nitrogen, and wait for 5 minutes to remove water and carbon dioxide; Step 3: Cover the cold trap with liquid nitrogen for 5 minutes and transfer the sample to the cold trap; Step 4: Maintain for 30 seconds to replenish the cold trap helium; Step 5: Freeze the chromatographic column with alcohol liquid nitrogen, remove the cold trap liquid nitrogen, and start testing the chromatograph detector; Step 6: After the oxygen peak appears, collect the oxygen in an oxygen cold trap; Step 7: After oxygen is collected, remove the alcohol liquid nitrogen from the chromatographic column. After the nitrogen peak appears, switch the valve to collect the sample in the nitrogen cold trap; Step 8: Transfer the sample gas to the sample tube and then to the mass spectrometer to test the isotopic composition.

Images