Method and equipment for treating tail gas and synchronously recovering chlorine gas in electronic-grade chlorine gas purification process

Abstract

The invention discloses a method and equipment for treating tail gas and synchronously recovering chlorine in an electronic-grade chlorine purification process, ClO2, Cl2O, Cl2O6 and NCl3 in heavy-component tail gas are decomposed into nitrogen, oxygen and chlorine under the action of light and a catalyst, the nitrogen and the oxygen are discharged, and the chlorine is recovered; the light wavelength is 50-800 nm, the catalyst is a titanium-based catalyst composed of an organic ligand and a titanium salt, the organic ligand is composed of one or more of carboxylic acids, pyridines, aromatic rings, furans and imidazoles, and the titanium salt is selected from one or more of an organic metal salt, a metal nitrate or a metal carbonate. The equipment comprises a photolysis processor and a freezing collection tank, wherein the photolysis processor and the freezing collection tank are respectively connected with a refrigerating machine; a light source is arranged at the top of the photolysis processor, a titanium-based catalyst is filled at the bottom of the photolysis processor, and a gas inlet pipe is arranged at the bottom of the photolysis processor; a blow-down pipe is arranged at the other end of the freezing collection tank.

Description

Technical Field

[0001] The invention relates to the field of electronic-grade chlorine purification, and in particular to a method and a device for electronic-grade chlorine purification and tail gas treatment. Background Art

[0002] Electronic-grade chlorine is a very important electronic specialty gas product, which is widely used as the main etching gas or auxiliary etching gas for substrate materials such as single-crystal silicon, polycrystalline silicon, Al, and W in the field of large-scale integrated circuit manufacturing and micro-electromechanical systems (MEMS). In the field of optical fiber production, electronic-grade chlorine is used to eliminate hydroxyl groups on the surface of optical fibers and reduce the loss during optical fiber transmission. With the development of optical fiber communications and microelectronics, the demand for electronic-grade chlorine is increasing, and the tail gas generated by the industrial chlorine purification process is increasing.

[0003] The main impurities of industrial chlorine produced by electrolysis of sodium chloride solution include H2O, O2, H2, N2, CO2, CO, HCl, ClO2, Cl2O, Cl2O6, NCl3, metal impurities, etc. Industrial chlorine can be used as raw material and purified to produce high-purity chlorine. Patent document CN103466549 A discloses a three-stage distillation tower designed by distillation process, in which industrial liquid chlorine passes through a vaporizer and then passes through a de-weighting tower to recover high-boiling components, and then passes through a de-lighting tower to recover light components such as O2 and N2 from the gas outlet. After the three-stage de-weighting tower is de-weighted again, 99.9999% of chlorine is collected in the third reflux tank. The patent does not involve how to safely handle and recover the heavy tail gas of the three-stage de-weighting tower. Patent document CN 215101986 U points out that nitrogen trichloride is extremely unstable in physical properties and is prone to explosion when enriched in liquid chlorine storage tanks. Therefore, nitrogen trichloride can be removed by using a chlorine water scrubber and a de-heavy distillation tower to prevent nitrogen trichloride from contaminating high-purity chlorine. However, in the heavy tail gas produced during the purification and production of electronic-grade chlorine, not only nitrogen trichloride is dangerous, but other components including ClO2, Cl2O, Cl2O6, etc. are also dangerous. Among them, ClO2 is quite sensitive to heat, vibration, impact and friction, and is very easy to decompose and explode; Cl2O has poor thermal stability and is the most unstable oxide of chlorine. It can gradually decompose at 3.8°C. Under the action of light and heat, it accelerates decomposition into Cl2 and O2, and can cause explosions; Cl2O6 will decompose into O2 and ClO2 under heating, light and other conditions.

[0004] After the heavy components such as ClO2, Cl2O, Cl2O6, and NCl3 are enriched and stored in tail gas collectors or other containers, they are prone to explosions, environmental pollution and other potential dangers, which seriously threaten production safety. At present, there is a lack of methods for safely handling and recovering the heavy components generated by the enrichment process in the production of electronic-grade chlorine. The energy consumption is high under the photothermal effect, and the controllability of the decomposition efficiency is poor at high temperatures, which easily leads to the rapid decomposition and explosion of the heavy components. The present invention does not require an external heat source and uses a photocatalyst to reduce the activation energy of the decomposition reaction, and the heavy component materials are safely and controllably decomposed and recovered. Summary of the invention

[0005] The first purpose of the present invention is to provide a method for simultaneously recovering chlorine during tail gas treatment in an electronic grade chlorine purification process, so as to solve the safety problems in the prior art that the heavy component mixture produced after chlorine purification and enrichment is extremely unstable and easy to decompose and explode.

[0006] A second object of the present invention is to provide an apparatus for use in the method.

[0007] To achieve the first purpose, the technical solution of the present invention is: a method for treating tail gas of electronic-grade chlorine purification process and recovering chlorine simultaneously, through the action of light and catalyst, ClO2, Cl2O, Cl2O6 and NCl3 in the heavy tail gas are decomposed into nitrogen, oxygen and chlorine, nitrogen and oxygen are discharged, and chlorine is recovered; the wavelength of the light is 50-800 nm, the catalyst is a titanium-based catalyst composed of organic ligands and titanium salts, the organic ligands are composed of one or more of carboxylic acids, pyridines, aromatic rings, furans, imidazoles, etc., and the titanium salts are selected from one or more of organic metal salts, metal nitrates or metal carbonates. The heavy tail gas refers to the tail gas containing ClO2, Cl2O, Cl2O6 and NCl3 produced in the process of purifying and producing electronic-grade chlorine.

[0008] The molar ratio of the organic ligand to the titanium salt is generally 1:0.2 to 1:3.2, preferably 1:0.5 to 1:3.2, and more preferably 1:0.5 to 1.5.

[0009] The titanium-based catalyst can be prepared by the following method: dissolving the organic ligand and the titanium salt in an organic solvent in proportion, heating to 80-150° C. and refluxing for 12-72 h, washing the solid with ethanol after centrifugation, and drying to obtain the titanium-based catalyst. The drying step can be performed at a temperature of 50-120° C. for 5-24 h.

[0010] The organic solvent is selected from at least one of ethanol, methanol, N,N-dimethylformamide and the like.

[0011] A method for simultaneously recovering chlorine from tail gas during electronic grade chlorine purification process comprises the following steps: (1) The titanium-based catalyst is loaded at the bottom of the photodecomposition processor. The temperature of the photodecomposition processor is controlled at 10°C to -25°C, and the temperature of the heavy component tail gas is controlled at -30 to -50°C.

[0012] (2) Turn on a light source with a wavelength of 50 to 800 nm and irradiate the titanium-based catalyst for 30 to 180 min. The preferred wavelength is 100 to 600 nm.

[0013] (3) The heavy tail gas is passed into a photodecomposition processor for liquefaction.

[0014] (4) When the liquid level reaches 2-10 mm, turn on the light source, and the ClO2, Cl2O, Cl2O6, and NCl3 in the heavy component tail gas will decompose to produce N2, O2, and Cl2.

[0015] Optionally, the wavelength of the light source is adjusted to 50-800 nm to control the decomposition rate of ClO2, Cl2O, Cl2O6, and NCl3 to achieve slow and safe decomposition.

[0016] (5) The gas generated by the decomposition in the photodecomposition processor is introduced into a freezing collection tank, the light component gas is discharged from the discharge port above the tank, and the Cl2 is condensed and liquefied in the tank.

[0017] To achieve the second purpose, the technical solution of the present invention is: an equipment for treating tail gas and simultaneously recovering chlorine in an electronic-grade chlorine purification process, comprising a photodecomposition processor and a freezing collection tank, wherein the photodecomposition processor and the freezing collection tank are respectively connected to a refrigerator; a light source is arranged on the top of the photodecomposition processor, a titanium-based catalyst is loaded on the bottom, an air inlet pipe is arranged on the bottom, an air outlet pipe is arranged on the upper part of the opposite end of the air inlet pipe and is connected to the freezing collection tank; a vent pipe is arranged on the other end of the freezing collection tank.

[0018] The light source is a tunable light source, providing light with a wavelength of 50-800 nm. The shorter the wavelength, the higher the energy of the photons, and the faster the decomposition of the heavy components.

[0019] The beneficial effects of the present invention are as follows: the method of the present invention safely and controllably decomposes the heavy components in the tail gas produced by the electronic grade chlorine purification process into N2, O2, and Cl2, and the light components such as O2 and N2 are discharged from the vent, thereby reducing the risk of explosion and environmental pollution, and reducing waste by recovering Cl2. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the equipment used for simultaneous recovery of chlorine during tail gas treatment in the electronic grade chlorine purification process.

[0021] Wherein: 1. Refrigerator; 2. Photodecomposition processor; 3. Light source; 4. Titanium-based catalyst; 5. Cryogenic collection tank; I. Air inlet pipe; II. Pipeline from the outlet of the photodecomposition processor to the inlet of the cryogenic collection tank; III. Vent pipe. DETAILED DESCRIPTION

[0022] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] In order to eliminate the interference of water enrichment on the performance of the catalyst, the heavy tail gas used in the embodiment was first dehydrated by adsorption to control the water content below 1 ppm. The main impurities in the heavy tail gas are: ClO2, Cl2O, Cl2O6, NCl3.

[0024] like Figure 1 As shown, an apparatus for treating tail gas from an electronic-grade chlorine purification process and recovering chlorine simultaneously comprises a photodecomposition processor and a freezing collection tank, wherein the photodecomposition processor and the freezing collection tank are respectively connected to a refrigerator; a light source is arranged on the top of the photodecomposition processor, a titanium-based catalyst is loaded on the bottom, an air inlet pipe is arranged on the bottom, an air outlet pipe is arranged on the upper part of the opposite end of the air inlet pipe and is connected to the freezing collection tank; a vent pipe is arranged on the other end of the freezing collection tank.

[0025] Example 1

[0026] Preparation of catalyst: Dissolve biphenyl dicarboxylic acid (BPDC) and Ti(NO3)4 in an organic solvent N,N-dimethylformamide at a molar ratio of 1:3.2, heat to reflux for 15-20 h, wash the solid with ethanol after centrifugation, and then bake at a temperature of 50-120°C for 5-24 h to obtain a titanium-based catalyst.

[0027] The titanium-based catalyst prepared above was loaded at the bottom of the photodecomposition processor, and a light source with a wavelength of 300 nm was selected to irradiate the titanium-based catalyst for 120 min to activate it. The temperature of the photodecomposition processor was controlled at -20~-28℃, and the temperature of the freezing collection tank was controlled at -40~-50℃. The heavy component tail gas was slowly introduced into the photodecomposition processor, and the air inlet pipe was closed when the liquid level in the photodecomposition processor reached 20mm. The light source with a wavelength of 300 nm was turned on, and the heavy components such as ClO2 and Cl2O were started to be photodecomposed. After the pressure of the photodecomposition processor slowly rose to 1MPa, the decomposed gas entered the freezing collection tank along the pipeline. When the pressure of the photodecomposition processor dropped to 50Kpa, the outlet pipe of the photodecomposition processor was closed. After the liquid level of the freezing collection tank stopped increasing, the vent pipe was opened to vent the light components such as O2 and N2. Table 1 shows the gas chromatography analysis results of the tail gas before and after treatment.

[0028] Table 1 Gas chromatography analysis results of tail gas before and after treatment in Example 1

[0029] Example 2 The titanium-based catalyst prepared in Example 1 was loaded at the bottom of the photodecomposition processor, and a light source with a wavelength of 500 nm was selected to irradiate the titanium-based catalyst for 60 minutes to activate it. The other operating steps were the same as in Example 1. Table 2 shows the gas chromatography analysis results of the tail gas before and after treatment.

[0030] Table 2 Gas chromatography analysis results of tail gas before and after treatment in Example 2

[0031] Comparing Example 1 with Example 2, it can be seen that the wavelength of the light source used in Example 2 is larger than that in Example 1 and the catalyst pretreatment time is shorter than that in Example 1. When the wavelength of the light source selected is larger and the catalyst pretreatment time is shorter, the catalyst activation is insufficient, reducing the active site Ti Ⅲ / Ti Ⅳ The formation of makes the recombinant spectroscopic decomposition effect weakened, so the purity of Cl2 in the tail gas after the treatment in Example 2 is significantly reduced.

[0032] Example 3

[0033] Preparation of catalyst: 5-[(3,5-dicarboxyphenyl)methyl]benzene-1,3-dicarboxylic acid (MDIP) and Ti(NO3)4 were dissolved in an organic solvent N,N-dimethylformamide at a molar ratio of 1:0.5, heated to reflux for 12-15 hours, and the solid was washed with ethanol after centrifugation, and then dried at a temperature of 50-120°C for 5-24 hours to obtain a titanium-based catalyst.

[0034] The method for treating the heavy tail gas is the same as in Example 1. Table 3 shows the results of gas chromatography analysis of the tail gas before and after treatment.

[0035] Table 3 Gas chromatography analysis results of tail gas before and after treatment in Example 3

[0036] Compared with Example 1, Example 3 increases the molar ratio of organic ligand to metal salt, and the content of Ti element is reduced, resulting in Ti Ⅲ / Ti Ⅳ The active sites are reduced, and the recombinant photolysis effect is deteriorated. Therefore, the content of the recombinant components in the tail gas after treatment in Example 3 is significantly higher than that in Example 1.

Claims

1. A method for treating tail gas from an electronic-grade chlorine purification process and simultaneously recovering chlorine, wherein ClO2, Cl2O, Cl2O6 and NCl3 in the heavy tail gas are decomposed into nitrogen, oxygen and chlorine through the action of light and catalyst, the nitrogen and oxygen are discharged, and the chlorine is recovered; the wavelength of the light is 50-800 nm, the catalyst is a titanium-based catalyst composed of an organic ligand and a titanium salt, the organic ligand is composed of one or more of carboxylic acids, pyridines, aromatic rings, furans, and imidazoles, and the titanium salt is selected from one or more of organic metal salts, metal nitrates or metal carbonates.

2. The method according to claim 1, characterized in that The molar ratio of the organic ligand to the titanium salt is 1:0.2~1:3.

2.

3. The method according to claim 2, characterized in that The molar ratio of the organic ligand to the titanium salt is 1:0.5~1:3.

2.

4. The method according to claim 3, characterized in that: The molar ratio of the organic ligand to the titanium salt is 1:0.5-1.

5.

5. The method according to claim 1, characterized in that The titanium-based catalyst is prepared by the following method: dissolving an organic ligand and a titanium salt in an organic solvent in proportion, heating to 80-150° C. and refluxing for 12-72 h, washing the solid with ethanol after centrifugation, and drying to obtain the titanium-based catalyst.

6. The method according to claim 5, characterized in that The drying step is to bake at a temperature of 50-120° C. for 5-24 hours.

7. The method according to claim 1, characterized in that: The organic solvent is selected from at least one of ethanol, methanol and N,N-dimethylformamide.

8. The method according to claim 1, characterized in that The following steps are involved: (1) The titanium-based catalyst is loaded at the bottom of the photodecomposition processor, the temperature of the photodecomposition processor is controlled at 10°C to -25°C, and the temperature of the heavy component tail gas is controlled at -30°C to -50°C; (2) Turn on the light source with a wavelength of 50-800 nm to irradiate the titanium-based catalyst for 30-180 min; (3) The heavy tail gas is introduced into a photodecomposition processor for liquefaction; (4) When the liquid level reaches 2-10 mm, turn on the light source, and the ClO2, Cl2O, Cl2O6, and NCl3 in the heavy component tail gas decompose to produce N2, O2, and Cl2; (5) The gas generated by the decomposition in the photodecomposition processor is introduced into a freezing collection tank, the light component gas is discharged from the discharge port above the tank, and the Cl2 is condensed and liquefied in the tank.

9. The method according to claim 8, characterized in that The wavelength of the light source in step (2) is 100-600 nm; the wavelength of the light source in step (2) is 50-800 nm.

10. An apparatus used in the method described in any one of claims 1 to 9, comprising a photodecomposition processor and a freezing collection tank, wherein the photodecomposition processor and the freezing collection tank are each connected to a refrigerator; a light source is arranged on the top of the photodecomposition processor, a titanium-based catalyst is filled at the bottom, an air inlet pipe is arranged at the bottom, an air outlet pipe is arranged at the upper part of the opposite end of the air inlet pipe and is connected to the freezing collection tank; a vent pipe is arranged at the other end of the freezing collection tank.

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