Nitric acid preparation device for simulating early atmospheric photochemical reaction of earth

Abstract

The utility model discloses a nitric acid preparation device for simulating an early atmospheric photochemical reaction of the earth. The nitric acid preparation device comprises an ultraviolet photochemical reaction system, a reaction gas source feeding system, a water vapor generator and a nitric acid freezing collector, the ultraviolet photochemical reaction system comprises an ultraviolet light source and a reaction chamber, and the ultraviolet light source is used for providing ultraviolet light required by reaction into the reaction chamber; the reaction gas source supply system is communicated with the reaction chamber and is used for supplying gas required for generating nitric acid through ultraviolet light chemical reaction into the reaction chamber; the water vapor generator is used for providing water vapor for the reaction chamber; the water vapor generator is connected with the reaction chamber; the nitric acid freezing collector is connected with the reaction chamber and is used for collecting nitric acid generated by photochemical reaction in the reaction chamber. The utility model realizes the preparation of nitric acid by simulating the early atmospheric photochemical reaction of the earth.

Description

Technical Field

[0001] This invention belongs to the field of Earth science research technology, and specifically relates to a nitric acid preparation device that simulates photochemical reactions in the early atmosphere of the Earth. Background Technology

[0002] It is currently believed that the oxygen concentration in the early Earth's atmosphere was less than one ten-thousandth of the modern atmospheric oxygen level. Increased atmospheric oxygen concentration is a prerequisite for the emergence of life on Earth and the formation of a habitable planet. Oxidized components such as H2O2 and O2, produced by the ultraviolet photolysis of oxygen-containing gas components like H2O and CO2, may have been an important source of oxygen in the pre-biological atmosphere and oceans of early Earth, but direct geological evidence is lacking. Atmospheric nitrates are a product of the non-mass fractionation (Δ) of oxygen isotopes on Earth. 17 Oxygen (O) is the largest mineral and a sensitive and effective indicator for tracing atmospheric photochemical processes. Nitrates produced by photochemical reactions are widely present in modern oxygen-rich atmospheres, but it is unclear whether similar ultraviolet photochemical reactions existed in the early oxygen-deficient atmospheres of Earth, or whether the nitrates produced exhibited non-mass fractionation of oxygen isotopes.

[0003] However, existing experimental devices and methods cannot simulate the photochemical reaction process for nitrate production in the early anaerobic / oxygen-deficient atmospheric environment of Earth. Therefore, there is an urgent need to provide a device for nitric acid preparation that can simulate the photochemical reaction of the early Earth atmosphere. Utility Model Content

[0004] Based on the above analysis, the present invention aims to provide a nitric acid preparation device that simulates the photochemical reactions of the early Earth's atmosphere, realizing the process of generating nitrates by simulating the photochemical reactions in the oxygen-free / oxygen-deficient atmospheric environment of the early Earth.

[0005] The purpose of this utility model is achieved as follows:

[0006] A device for preparing nitric acid that simulates photochemical reactions in the early Earth's atmosphere, comprising:

[0007] The ultraviolet photochemical reaction system includes an ultraviolet light source and a reaction chamber. The reaction chamber 12 serves as the site for the ultraviolet photochemical reaction to generate nitric acid, and the ultraviolet light source is used to emit ultraviolet light into the reaction chamber.

[0008] A reaction gas supply system, connected to the reaction chamber, is used to supply the gas required for the ultraviolet photochemical reaction to produce nitric acid, simulating the composition of the early Earth's atmosphere. The reaction gas supply system includes a first gas supply device, a second gas supply device, and a third gas supply device. The first gas supply device is used to supply NO to the reaction chamber. x A mixture of O2 and N2; a second gas supply device for supplying CO2 to the reaction chamber; and a third gas supply device for supplying pure O2 or a mixture of O2 and He to the reaction chamber.

[0009] A water vapor generator, connected to the reaction chamber, is used to supply water vapor to the reaction chamber to simulate the humidity of the early Earth's atmosphere;

[0010] A nitric acid cryogenic collector, connected to the reaction chamber, is used to collect nitric acid produced by the photochemical reaction within the reaction chamber.

[0011] Furthermore, the reaction chamber is a stainless steel cylinder with one end open and the other end closed.

[0012] Furthermore, the reaction chamber has an ultraviolet light inlet, a reaction gas inlet, a water vapor inlet, and a product outlet; the stainless steel cylinder is arranged horizontally along its axis, with one end of the stainless steel cylinder open as the ultraviolet light inlet, the ultraviolet light inlet and the product outlet located at both ends of the stainless steel cylinder along its axis, and the reaction gas inlet and the water vapor inlet located on the side wall of the stainless steel cylinder.

[0013] Furthermore, the reaction chamber is equipped with a first heating device, which is configured to control the temperature inside the reaction chamber at 65±0.5℃.

[0014] Furthermore, the water vapor generator includes a water tank and a helium source. The water tank contains ultrapure water, the helium inlet at the bottom of the water tank is connected to the helium source through a helium path, and the water vapor outlet at the top of the water tank is connected to the water vapor inlet through a water vapor path.

[0015] Furthermore, a second heating device is provided outside the water tank, configured to maintain the ultrapure water in the tank at 25-65°C.

[0016] Furthermore, the nitric acid cryogenic collector includes a cold source container and a collection pipe, with the top opening of the cold source container and the cold source container containing a cryogenic liquid at -50±5℃.

[0017] Furthermore, a product inlet pipe extending from the top of the collection pipe to the bottom of the collection pipe is provided, and a product outlet pipe is provided on the upper side wall of the collection pipe; the product outlet is connected to the product inlet pipe through a stainless steel pipe.

[0018] Furthermore, the top of the product feed pipe extends upwards to form a narrowed section, the inner diameter of which is smaller than the inner diameter of the product feed pipe.

[0019] Furthermore, the ultraviolet light source adopts the L11798 type vacuum ultraviolet light source.

[0020] Compared with existing technologies, the nitric acid preparation device for simulating photochemical reactions in the early atmosphere of Earth provided by this utility model has a simple structure, is easy to operate, and does not require complicated manual operation during the experiment, thus improving experimental efficiency. Moreover, the nitric acid generated in the experiment can be efficiently recovered through the nitric acid freezer collector. The experiment does not generate toxic gases and does not pollute the environment, making it green and environmentally friendly.

[0021] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages will become apparent from the description or be learned by practicing the invention. The objectives and other advantages of this invention can be realized and obtained from the description and accompanying drawings, which are particularly pointed out. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this specification or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the embodiments of this specification. For those skilled in the art, other drawings can be obtained based on these drawings.

[0023] Figure 1 A schematic diagram of the nitric acid preparation apparatus for simulating photochemical reactions in the early Earth atmosphere provided by this utility model;

[0024] Figure 2 A simplified cross-sectional diagram of the ultraviolet photochemical reaction system provided by this utility model;

[0025] Figure 3 A schematic diagram of the reaction gas supply system provided by this utility model.

[0026] Figure label:

[0027] 1. Ultraviolet photochemical reaction system; 11. Ultraviolet light source; 12. Reaction chamber; 121. Reaction gas inlet; 122. Water vapor inlet; 123. Product outlet; 124. MgF2 glass window; 2. Reaction gas supply system; 21. First gas supply device; 22. Second gas supply device; 23. Third gas supply device; 24. Main gas pipe; 25. First branch gas pipe; 251. First gas flow controller; 26. Second branch gas pipe; 261. Second gas flow controller; 27. Third branch gas pipe; 271. Third gas flow controller; 28. Four-way valve; 3. Water vapor generator; 31. Water tank; 32. Helium source; 33. Helium path; 331. Fourth gas flow controller; 34. Water vapor path; 4. Nitric acid cryogenic collector; 41. Cold source container; 42. Collection pipe; 421. Product inlet pipe; 422. Product outlet pipe; 423. Narrowing section. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0029] To facilitate understanding of the embodiments of this application, further explanation and description will be provided below with reference to the accompanying drawings and specific embodiments. These embodiments do not constitute a limitation on the embodiments of this application. In the drawings, the dimensions and relative dimensions of components may be exaggerated for clarity and / or descriptive purposes. When exemplary embodiments can be implemented differently, a specific process sequence may be performed in a different order than that described. For example, two consecutively described processes may be performed substantially simultaneously or in the reverse order of their description. Furthermore, the same reference numerals denote the same components.

[0030] The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting. As used herein, unless the context clearly indicates otherwise, the singular forms “a” and “the” are intended to include the plural forms as well. Furthermore, when the terms “comprising” and / or “including” and variations thereof are used in this specification, it indicates the presence of the stated features, integrals, steps, operations, parts, components, and / or groups thereof, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, parts, components, and / or groups thereof. It should also be noted that, as used herein, the terms “substantially,” “about,” and other similar terms are used as approximate terms rather than as terms of degree, thus explaining the inherent biases in measurements, calculated values, and / or provided values ​​that would be recognized by one of ordinary skill in the art.

[0031] Example 1

[0032] A specific embodiment of this utility model is as follows: Figures 1 to 3 As shown, a nitric acid preparation device simulating the photochemical reaction of the early Earth's atmosphere is disclosed, including an ultraviolet photochemical reaction system 1, a reaction gas source supply system 2, a water vapor generator 3, and a nitric acid cryogenic collector 4.

[0033] The ultraviolet photochemical reaction system 1 includes an ultraviolet light source 11 and a reaction chamber 12. The reaction chamber 12 serves as the site for the ultraviolet photochemical reaction to generate nitric acid. The ultraviolet light source 11 is used to provide the ultraviolet light required for the reaction into the reaction chamber 12. The reaction chamber 12 has an ultraviolet light inlet, a reaction gas inlet 121, a water vapor inlet 122, and a product outlet 123. An ultraviolet-transmitting MgF2 glass window 124 is sealed and installed at the ultraviolet light inlet. The ultraviolet light source 11 is located outside the MgF2 glass window 124 and provides the ultraviolet light required for the reaction into the reaction chamber 12 through the MgF2 glass window 124.

[0034] The reaction gas supply system 2 is used to supply the gas required for the ultraviolet photochemical reaction to generate nitric acid into the reaction chamber 12, in order to simulate the composition of the early Earth's atmosphere. The reaction gas supply system 2 includes a gas supply pipeline, the outlet end of which is connected to the reaction gas inlet 121 of the reaction chamber 12. The inlet end of the gas supply pipeline is equipped with a first gas supply device 21, a second gas supply device 22, and a third gas supply device 23. The first gas supply device 21 is used to supply NO to the reaction chamber 12. x A mixture of NO and N2, wherein NO x The first gas supply device is a NO + NO2 mixture; the second gas supply device 22 is used to supply CO2 to the reaction chamber 12; the third gas supply device 23 is used to supply pure O2 or a mixture of O2 and He to the reaction chamber 12.

[0035] A water vapor generator 3 is used to supply water vapor to the reaction chamber 12 to simulate the humidity of the early Earth's atmosphere; the water vapor generator 3 has a water vapor outlet, which is connected to the water vapor inlet 122 of the reaction chamber 12.

[0036] The nitric acid cryogenic collector 4 is connected to the product outlet 123 of the reaction chamber 12 and is used to collect the nitric acid produced by the photochemical reaction in the reaction chamber 12.

[0037] In one alternative embodiment, the reaction chamber 12 is a stainless steel cylinder open at one end and closed at the other, with the interior space of the stainless steel cylinder serving as the site for the ultraviolet photochemical reaction to generate nitric acid. Specifically, the axial length of the stainless steel cylinder is 20 cm, and the inner diameter of the stainless steel cylinder is 2.5 cm. The stainless steel cylinder is horizontally fixed on a horizontal operating table, that is, the axis of the stainless steel cylinder is arranged horizontally. The ultraviolet light inlet and the product outlet 123 are located at both ends of the axial direction of the stainless steel cylinder, and the reaction gas inlet 121 and the water vapor inlet 122 are located on the side wall of the stainless steel cylinder.

[0038] Optionally, the angle between the reaction gas inlet 121 and the water vapor inlet 122 is 90°, and both are closer to the side wall of the stainless steel cylinder on the side of the ultraviolet light inlet. This arrangement not only allows the reaction gas and water vapor supplied to the reaction chamber 12 to mix more thoroughly, but also allows the mixed gas to react with the incident ultraviolet light in the reaction chamber 12 for a longer period of time, thus making the reaction more complete.

[0039] To ensure a more complete reaction, one end of the stainless steel drum is open as an ultraviolet (UV) inlet with a diameter of 2.5 cm. The other end of the drum has an end wall, on which the product outlet 123 is located. A MgF2 glass window 124 is sealed and fixedly installed between the UV inlet and the UV light source 11. The UV light emitted by the UV light source 11 enters the reaction chamber 12 through the MgF2 glass window 124, ensuring complete UV irradiation within the reaction chamber 12. The connection between the UV light source 11 and the reaction chamber 12 is sealed with a Teflon gasket and secured by manually tightening a nut.

[0040] Furthermore, the reaction chamber 12 is provided with a first heating device, which is configured to control the temperature of the reaction chamber 12 at 65±0.5℃. Exemplarily, the first heating device includes a first resistance wire wound around the outside of a stainless steel cylinder. During the reaction, the heating temperature of the first resistance wire is controlled by adjusting the voltage, thereby controlling the temperature of the reaction chamber 12 at 65±0.5℃ to prevent the generated nitric acid from adsorbing onto the inner wall of the stainless steel cylinder under low-temperature conditions.

[0041] In this embodiment, the gas supply pipeline of the reaction gas source supply system 2 includes a main gas pipe 24, a first branch gas pipe 25, a second branch gas pipe 26, and a third branch gas pipe 27. One end of the main gas pipe 24 is connected to the reaction gas inlet 121 of the reaction chamber 12, and the other end of the main gas pipe 24 is connected to the first branch gas pipe 25, the second branch gas pipe 26, and the third branch gas pipe 27 through a four-way connector 28. The first gas supply device 21 has an independently supplied N2 gas cylinder and an NO gas cylinder. x Gas cylinder, NO x The gas is a mixture of NO and NO2; the second gas supply device 22 has a CO2 gas cylinder; the third gas supply device 23 has an independently supplied O2 gas cylinder and a He gas cylinder; the main gas pipe 24, the first branch gas pipe 25, the second branch gas pipe 26, and the third branch gas pipe 27 are all equipped with gas flow controllers.

[0042] In one alternative embodiment, the main gas pipe 24 of the reaction gas supply system 2 is connected to the first gas supply device 21, the second gas supply device 22, and the third gas supply device 23 via a four-way connector 28 and three branch gas pipes. The main gas pipe 24, the first branch gas pipe 25, the second branch gas pipe 26, and the third branch gas pipe 27 all use quartz capillary tubes with a diameter of 1 / 8 mm. The N2 gas cylinder and NO gas cylinder of the first gas supply device 21... x The gas cylinders include a CO2 cylinder from the second gas supply device 22, an O2 cylinder from the third gas supply device 23, and a He cylinder. Each gas cylinder can also be equipped with its own gas flow controller. Figure 3 The diagram only shows the first gas flow controller 251, the second gas flow controller 261, and the third gas flow controller 271 installed on three branch pipelines. By using the gas flow controllers at each location, the flow rates of different reactive gases can be precisely adjusted, thereby simulating the composition of the early Earth's atmosphere.

[0043] In this embodiment, the water vapor generator 3 uses high-purity helium as the carrier gas to deliver water vapor into the reaction chamber 12. Specifically, the water vapor generator 3 includes a water tank 31 and a helium source 32. The water tank 31 is filled with ultrapure water, but the ultrapure water does not completely fill the tank; that is, the volume of ultrapure water in the tank 31 occupies 1 / 2 to 3 / 4 of its volume. The water vapor outlet is located at the top of the water tank 31 and is connected to the water vapor inlet 122 of the reaction chamber 12 via a water vapor passage 34. A helium inlet is located at the bottom of the water tank 31 and is connected to the helium source 32 via a helium passage 33. The helium source 32 supplies helium into the water tank 31 through the helium passage 33, and the water vapor is carried into the reaction chamber 12 by the He gas flow through the water vapor passage 34. A fourth gas flow controller 331 is provided on the helium passage 33 to precisely control the helium flow rate. It is understandable that a gas flow controller could also be installed on the water vapor path 34.

[0044] Because the pressure in reaction chamber 12 is higher than that in water tank 31 during the reaction, to prevent nitric acid generated in reaction chamber 12 from flowing back into water tank 31, the water vapor path 34 has a first diameter, and the helium path 33 has a second diameter, with the first diameter being larger than the second diameter, approximately 3-5 times larger. For example, both the water vapor path 34 and the helium path 33 are quartz capillary tubes, and the first diameter of the water vapor path 34 is 4 times the second diameter of the helium path 33. Specifically, the water vapor inlet 122 of reaction chamber 12 is connected to water tank 31 via a quartz capillary tube with a diameter of 1 / 8 mm, and the helium source 32 is connected to water tank 31 via a quartz capillary tube with a diameter of 1 / 32 mm. The helium source 32 uses a smaller diameter quartz capillary tube to supply helium into water tank 31, and then uses a larger diameter quartz capillary tube to carry water vapor into reaction chamber 12, effectively preventing nitric acid generated in reaction chamber 12 from flowing back into water tank 31. Furthermore, a second heating device is provided outside the water tank 31, configured to maintain the ultrapure water in the water tank 31 at 25-65°C. Optionally, the second heating device includes a second resistance wire, which can be wound around the outside of the water tank 31. The heating temperature of the second resistance wire is controlled by adjusting the heating voltage, thereby controlling the temperature inside the water tank 31 between 25°C and 65°C. The humidity is simulated to mimic the early atmosphere of Earth by adjusting the He gas flow rate and the heating temperature of the water tank 31.

[0045] In one alternative embodiment, the nitric acid cryogenic collector 4 includes a cold source container 41 and a collection pipe 42. The cold source container 41 has an opening at the top and is filled with a cryogenic liquid. The top of the collection pipe 42 is provided with a product inlet pipe 421 extending to the bottom of the collection pipe 42. The upper side wall of the collection pipe 42 is provided with a product outlet pipe 422, which serves as an outlet for the reaction product. The product outlet 123 of the reaction chamber 12 is connected to the collection pipe 42 of the nitric acid cryogenic collector 4 through a stainless steel pipe with an outer diameter of 3 mm and an inner diameter of 2 mm. Optionally, the top and bottom walls of the collection pipe 42 are both concave arc surfaces. The product supply pipe 421 passes through the top wall and the outer wall of the product supply pipe 421 is sealed to the top wall. The top of the product supply pipe 421 extends upward with a narrowing section 423. The inner diameter of the narrowing section 423 is smaller than the inner diameter of the main body of the product supply pipe 421. The opening of the narrowing section 423 is connected to the product outlet 123 of the reaction chamber 12 through a stainless steel pipe with an outer diameter of 3 mm and an inner diameter of 2 mm. The bottom opening of the product supply pipe 421 serves as the inlet for the product to enter the collection pipe 42. The bottom opening of the product supply pipe 421 is located below the product outlet pipe 422 and above the liquid surface of the cryogenic liquid.

[0046] When collecting the nitric acid generated by the reaction, the lower part of the collection tube 42 is placed in the freezing liquid of the cold source container 41, and the bottom opening of the product supply tube 421 is located above the liquid surface of the freezing liquid, so that it does not directly contact the low-temperature freezing liquid. Moreover, since the top of the product supply tube 421 has a narrowing section 423 with a smaller diameter, the nitric acid and water vapor in the mixed gas after the reaction are not easily frozen into ice when they diffuse at the diameter change. Instead, they are more likely to condense into liquid at the diameter change. The condensate drips onto or flows along the tube wall of the collection tube 42 to the bottom of the collection tube 42, and is then frozen into solid by the low-temperature freezing liquid. Therefore, the collection tube 42 with this structure will not be blocked by ice.

[0047] In one alternative embodiment, the cooling temperature of the cryogenic liquid in the cold source container 41 is -50±5°C. For example, the cryogenic liquid can be prepared from liquid nitrogen and alcohol, and the nitric acid produced by the chemical reaction is collected by freezing the cryogenic liquid at -50±5°C.

[0048] To prevent the quartz collection tube 42 from freezing during the collection of nitric acid, the distance between the bottom of the collection tube 42 and the bottom of the cold source container 41 shall be no less than 2 cm, preferably 2-4 cm, and the bottom opening of the product inlet tube 421 shall be 4 cm above the surface of the freezing liquid. Optionally, the bottom of the collection tube 42 shall be 2-3 cm below the surface of the freezing liquid.

[0049] In one alternative embodiment, the cold source container 41 and the collection tube 42 of the nitric acid cryogenic collector 4 are both quartz glass tubes. For example, the inner diameter of the cold source container 41 is 3 cm and the height is 20 cm; the outer diameter of the collection tube 42 is 18 mm and the inner diameter is 15 mm; the outer diameter of the product inlet tube 421 is 12 mm and the inner diameter is 9 mm; and the outer diameter of the product outlet tube 422 is 6.4 mm.

[0050] In one alternative embodiment, the outer diameter of the top reduced-diameter section 423 of the product inlet pipe 421 is 6.4 mm, and a manual quick-connect coupling with an inner diameter of 6.4 mm is used to seal the product inlet pipe 421 to the stainless steel pipe. Specifically, one end of the manual quick-connect coupling is sealed to the top reduced-diameter section 423 of the product inlet pipe 421 via an O-ring rubber seal, and the other end of the manual quick-connect coupling is sealed to the stainless steel pipe via a circular rubber gasket, with the stainless steel pipe passing directly through the rubber gasket for a sealed connection.

[0051] The steps for preparing nitric acid using the nitric acid preparation apparatus simulating photochemical reactions in the early Earth's atmosphere according to this embodiment are as follows:

[0052] Step 1: Before the formal reaction begins, the reaction chamber is purged with high-purity N2 gas continuously from the N2 cylinder of the first gas supply device 21 for at least 24 hours to remove any potential contaminants. Simultaneously, high-purity He gas is continuously supplied to the MQ water in the water tank 31 via the helium source 32 of the steam generator 3 to remove any dissolved O2 and prevent trace amounts of O2 or other impurities from participating in the reaction and adversely affecting the results. In this step, the nitric acid cryogenic collector 4 is not used for cryogenic enrichment; that is, the collection tube 42 of the nitric acid cryogenic collector 4 is not placed in the cryogenic liquid of the cold source container 41.

[0053] Step 2: After the formal reaction begins, according to the early atmospheric composition data of the Earth, the gas components required for the reaction are supplied to the reaction chamber 12 using the reaction gas supply system 2, and water vapor is supplied to the reaction chamber 12 using the water vapor generator 3. After the flow rates of each gas are stable, the ultraviolet light source 11 is turned on, and the collection tube 42 of the nitric acid cryogenic collector 4 is placed into the cryogenic liquid in the cold source container 41 to freeze and collect the HNO3 generated by the reaction.

[0054] Based on previous research on the composition of Earth's early atmosphere, the first gas supply device 21, the second gas supply device 22, the third gas supply device 23, and the water vapor generator 3 supply pure N2, CO2, O2, He, water vapor, and trace amounts of NO. x The system simulates the composition of Earth's early atmosphere, with the concentrations of each gas component regulated by a gas flow controller. Specifically, NO is supplied to the reaction chamber 12 at a predetermined concentration and flow rate using the first gas supply device 21. x A mixture of NO and N2 gas, with a constant flow rate of 100 mL / min, is supplied to reaction chamber 12. x In the mixture of NO and N2, NO x The concentration is 5 ppm, and it can be pre-prepared to contain 5.0 ppm NO. x N2+NO x Mixed gas (NO) x The primary gas is NO, with an NO2 content of approximately 0.1 ppm. The second gas supply device 22 supplies CO2 to the reaction chamber 12 at a predetermined concentration and flow rate, maintaining a constant flow rate of 0.5 mL / min. The helium gas used in the water vapor generator 3 flows at a constant rate of 2.2 mL / min. The third gas supply device 23 supplies pure O2 or a mixture of O2 and He to the reaction chamber 12 at a predetermined concentration and flow rate. The flow rate of the pure O2 or the O2 and He mixture varies depending on the experimentally determined oxygen concentration in the reaction chamber 12. In other words, during each experiment, the NO concentration is maintained at a constant level. xWhile maintaining a constant flow rate of water vapor transported by the N2 mixed gas, CO2, and helium carrier gas, a series of experiments were conducted by varying the flow rate of oxygen or a mixture of oxygen and helium supplied to the reaction chamber 12. During these experiments, the third gas supply device 23 was adjusted to supply the reaction chamber 12 with mixtures of O2 and He at different O2 concentrations, or with pure O2, to obtain test results for nitric acid prepared at different O2 concentrations. In this step, the flow rate of each gas from the three gas supply devices and the water vapor generator 3 was individually adjusted, starting with a low flow rate and gradually increasing to accurately control the flow rate of each gas. After the flow rates in all gas paths stabilized, the ultraviolet light source 11 was turned on to conduct the ultraviolet photochemical reaction. The ultraviolet light source 11 was an L11798 vacuum ultraviolet light source manufactured by Hamamatsu Photonics Co., Ltd. of Japan, with wavelengths primarily at 125 nm and 160 nm.

[0055] Step 3: After the reaction is complete, transfer all the HNO3-containing solution collected in collection tube 42 of the nitric acid cryo-collector 4 to a capped sample tube, dilute it, seal it, and freeze it. Specifically, remove collection tube 42 from the cryogenic solution in cold source container 41, thaw the HNO3-containing solid in collection tube 42 at room temperature, and then heat it to melt, obtaining approximately 1 mL of HNO3-containing solution (e.g., 0.8-1.2 mL). Subsequently, transfer all the HNO3-containing solution collected in collection tube 42 to a capped sample tube, rinse the cryo-collector three times with MQ water to avoid residual contamination, and transfer the HNO3-containing rinsing solution to the sample tube. Finally, bring the HNO3 solution to a final volume of 2-2.5 mL, seal it, and freeze it for testing the nitrogen and oxygen isotopes of nitric acid.

[0056] The simulation results obtained by following the above steps are shown in Table 1:

[0057] Table 1. Simulation Experiment Data Results

[0058]

[0059] After obtaining nitric acid, the content and δ of the nitric acid produced by the photochemical reaction were analyzed using bacterial denitrification. 15 N, δ 17 O, δ 18 O and △ 17 The O values ​​are shown in Table 1. The experimental results indicate that the ΔO value of nitric acid... 17 The O value generally tends to increase with increasing oxygen concentration. During the process of increasing oxygen concentration from 0 to 5.1%, the ΔO value of nitric acid... 17 The oxygen concentration ranges from 0.3‰ to 1.1‰, with a maximum value of only 1.1‰; when the oxygen concentration increases to 5.4%, the ΔH value of nitric acid... 17 The O value suddenly increased significantly to 4.7‰, and the Δ of nitric acid...17 The oxygen concentration (ΔO) continues to increase with further increases in oxygen concentration. For example, when the oxygen concentration increases to 8.1‰ and 11.2‰, the ΔO value of nitric acid... 17 The O values ​​increased to 10.1‰ and 14.02‰ respectively, indicating that the generated nitric acid has an oxygen isotope anomaly, and the ΔO value of the nitric acid produced by the ultraviolet photochemical reaction is also higher. 17 The O value is closely related to the atmospheric oxygen concentration.

[0060] Compared with existing technologies, the nitric acid preparation device simulating the photochemical reactions of the early Earth's atmosphere provided in this embodiment uses ultraviolet light to irradiate a mixture containing N2, H2O, CO2, trace amounts of O2, and NO. x This study simulates the photochemical reaction processes of the early Earth's atmosphere, producing nitric acid (HNO3) with a significant oxygen isotope non-mass fractionation effect. This confirms that photochemical reactions in the early, oxygen-deficient atmosphere of Earth can generate nitric acid, and that the oxygen isotope non-mass fractionation of the generated nitric acid is closely related to oxygen concentration. Furthermore, the oxygen isotope non-mass fractionation effect of nitrates in early sedimentary formations (such as Proterozoic glacial till) can be used to trace the source of oxygen in the early Earth's atmosphere, providing important experimental evidence for events of increased atmospheric oxygen concentration in the early Proterozoic. This has significant implications for research on early Earth climate change and related topics. The structure of this application is simple and easy to operate, requiring no complex manual operations, thus improving experimental efficiency. Moreover, the nitric acid generated in the experiment is efficiently recovered through a nitric acid cryogenic collector, and the experiment does not produce toxic gases or pollute the environment, making it environmentally friendly.

[0061] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above description is only a specific embodiment of this application and is not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A device for preparing nitric acid that simulates photochemical reactions in the early Earth's atmosphere, characterized in that, include: An ultraviolet photochemical reaction system includes an ultraviolet light source and a reaction chamber. The reaction chamber serves as the site for the ultraviolet photochemical reaction to generate nitric acid, and the ultraviolet light source is used to emit ultraviolet light into the reaction chamber. A reaction gas supply system, connected to the reaction chamber, is used to supply the gas required for the ultraviolet photochemical reaction to produce nitric acid, simulating the composition of the early Earth's atmosphere. The reaction gas supply system includes a first gas supply device, a second gas supply device, and a third gas supply device. The first gas supply device is used to supply NO to the reaction chamber. x A mixture of O2 and N2; a second gas supply device is used to supply CO2 to the reaction chamber; a third gas supply device is used to supply pure O2 or a mixture of O2 and He to the reaction chamber; A water vapor generator, connected to the reaction chamber, is used to supply water vapor to the reaction chamber to simulate the humidity of the early Earth's atmosphere; A nitric acid cryogenic collector, connected to the reaction chamber, is used to collect nitric acid produced by the photochemical reaction within the reaction chamber.

2. The nitric acid preparation apparatus for simulating photochemical reactions in the early Earth's atmosphere according to claim 1, characterized in that, The reaction chamber is a stainless steel cylinder with one end open and the other end closed.

3. The nitric acid preparation apparatus for simulating photochemical reactions in the early Earth's atmosphere according to claim 2, characterized in that, The reaction chamber has an ultraviolet light inlet, a reaction gas inlet, a water vapor inlet, and a product outlet; the stainless steel cylinder is arranged horizontally along its axis, with one end of the stainless steel cylinder open as the ultraviolet light inlet, the ultraviolet light inlet and the product outlet located at both ends of the axial direction of the stainless steel cylinder, and the reaction gas inlet and the water vapor inlet located on the side wall of the stainless steel cylinder.

4. The nitric acid preparation apparatus for simulating photochemical reactions in the early Earth's atmosphere according to claim 3, characterized in that, The reaction chamber is equipped with a first heating device, which is configured to control the temperature inside the reaction chamber at 65±0.5℃.

5. The nitric acid preparation apparatus for simulating photochemical reactions in the early Earth's atmosphere according to claim 3, characterized in that, The water vapor generator includes a water tank and a helium source. The water tank contains ultrapure water. The helium inlet at the bottom of the water tank is connected to the helium source via a helium path, and the water vapor outlet at the top of the water tank is connected to the water vapor inlet via a water vapor path.

6. The nitric acid preparation apparatus for simulating photochemical reactions in the early Earth's atmosphere according to claim 5, characterized in that, The water tank is equipped with a second heating device, which is configured to maintain the ultrapure water in the tank at 25~65°C.

7. The nitric acid preparation apparatus for simulating photochemical reactions in the early Earth's atmosphere according to claim 1, characterized in that, The nitric acid cryogenic collector includes a cold source container and a collection pipe. The cold source container has an opening at the top and is filled with a cryogenic liquid at -50±5°C.

8. The nitric acid preparation apparatus for simulating photochemical reactions in the early Earth's atmosphere according to claim 7, characterized in that, The top of the collection tube is provided with a product inlet tube extending to the bottom of the collection tube, and the upper side wall of the collection tube is provided with a product outlet tube; the product outlet is connected to the product inlet tube through a stainless steel tube.

9. The nitric acid preparation apparatus for simulating photochemical reactions in the early Earth's atmosphere according to claim 8, characterized in that, The top of the product supply pipe extends upwards with a narrowed section, the inner diameter of which is smaller than the inner diameter of the product supply pipe.

10. The nitric acid preparation apparatus for simulating photochemical reactions in the early Earth's atmosphere according to claim 1, characterized in that, The ultraviolet light source is an L11798 type vacuum ultraviolet light source.

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