CN116216666A - Preparation method of high-purity nitrogen trifluoride and application of high-purity nitrogen trifluoride - Google Patents
Preparation method of high-purity nitrogen trifluoride and application of high-purity nitrogen trifluoride Download PDFInfo
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Abstract
The invention provides a preparation method of high-purity nitrogen trifluoride, which comprises the following steps: independently introducing fluorine gas and ammonia gas into the protective gas in sequence, mixing to obtain mixed gas, and reacting the mixed gas to obtain mixed gas containing hydrogen fluoride, nitrogen trifluoride and the protective gas; and (3) adsorbing the hydrogen fluoride in the mixed gas containing the hydrogen fluoride, the nitrogen trifluoride and the protective gas by using a hydrogen fluoride adsorbent to obtain a purified mixed gas, and condensing and separating to obtain the high-purity nitrogen trifluoride. Also provided is the use of the high purity nitrogen trifluoride prepared by the above preparation method, and the high purity nitrogen trifluoride is used in the microelectronics industry. The nitrogen trifluoride gas prepared by the preparation method of the high-purity nitrogen trifluoride has higher purity, simple preparation process and higher preparation efficiency, does not generate a large amount of wastewater polluting the environment, and is easy to be applied to industrial production on a large scale.
Description
Technical Field
The invention belongs to the technical field of nitrogen trifluoride preparation, and particularly relates to a preparation method of high-purity nitrogen trifluoride and application of the high-purity nitrogen trifluoride.
Background
Nitrogen trifluoride is mainly applied to the microelectronics industry, is an excellent plasma etchant and cleaning agent, and particularly has quite excellent etching speed and selectivity for semiconductor materials such as silicon, silicon nitride and the like; when the nitrogen trifluoride is used as a gas cleaning agent, the cleaning efficiency of the nitrogen trifluoride is high and no trace is left. In recent years, with the growth of the global semiconductor industry, the liquid crystal display industry and the photovoltaic industry, the demand for nitrogen trifluoride has been rapidly increased, and the production of nitrogen trifluoride with high quality and high productivity has been attracting attention.
Raw material gas for purifying and preparing high-purity nitrogen trifluoride gas is generally produced by a chemical synthesis method or an electrolytic method. The more classical chemical synthesis is with NH 3 And F is equal to 2 The nitrogen trifluoride gas is prepared by reaction, but crude NF prepared by chemical synthesis method 3 The content of various impurities in the gas is high.
The process methods for refining and purifying nitrogen trifluoride gas are reported in patent documents of various countries, and the specific process methods are different and have different lengths, but most of the process methods for refining high-purity nitrogen trifluoride gas are process methods realized in a laboratory and are not suitable for large-scale industrial production.
CN106222688A discloses a method for preparing nitrogen trifluoride by electrolyzing ammonium bifluoride, which comprises the steps of preparing a conductive graphene modified carbon electrode as an anode of an electrolytic reaction. Preparing electrolyte by hydrogen fluoride and ammonium fluoride according to a molar ratio (molten salt ratio) of 1-3:1, continuously injecting the electrolyte into an electrolytic tank, wherein the electrolysis temperature is 80-150 ℃, the pressure is-0.01 MPa, the voltage is 5-10V, and the anode generating gas contains NF 3 、CF 4 And N 2 O and some trace impurities, the mixed gas is subjected to a series of refining processes known in the art, including impurity fluorine removal, acidic impurity removal, and NF adsorption by a molecular sieve 3 Make NF 3 And CF (compact flash) 4 Separation, NF 3 And refining by water washing and alkali washing to obtain the product. However, the method for preparing nitrogen trifluoride by electrolyzing ammonium bifluorideComplex art and NF 3 The preparation efficiency is low, and the large-scale popularization and use are not facilitated.
CN113247870B discloses a method and a device for preparing high-purity nitrogen trifluoride gas, which belong to the technical field of nitrogen trifluoride gas preparation. The method is NF prepared by adopting an electrolytic method 3 The electrolytic gas is subjected to secondary cracking, cooling, water washing, reduction, alkali washing, water removal and secondary rectification in sequence. In addition, the device comprises an electrolytic tank, a primary pyrolysis tower, a secondary pyrolysis tower, a first buffer tank, a cooler, a second buffer tank, a water washing tower, a reduction tower, an alkaline washing tower, a water ring compressor, a water removal tower, a diaphragm compressor, a primary rectifying tower, a secondary rectifying tower and a filling system. However, the process of the method for preparing the high-purity nitrogen trifluoride gas is complex, a large amount of wastewater which is difficult to treat can be generated, the environment-friendly requirement is not met, and meanwhile, the device is complex in structure, high in manufacturing cost and unfavorable for large-scale popularization and use.
The preparation and purification methods of nitrogen trifluoride disclosed at present have certain defects, and have the problems that the impurity content in the prepared nitrogen trifluoride gas is high, the preparation process is complex, the preparation efficiency is low, the method is not suitable for large-scale industrial production, and a large amount of wastewater which is difficult to treat is generated in the purification process. Therefore, development and design of a novel preparation method of high-purity nitrogen trifluoride and application of the high-purity nitrogen trifluoride are important.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a preparation method of high-purity nitrogen trifluoride and application of the high-purity nitrogen trifluoride, and the nitrogen trifluoride gas prepared by the method has higher purity, simple preparation process and higher preparation efficiency, does not generate a large amount of wastewater polluting the environment, and is easy to be applied to industrial production on a large scale.
In order to solve the technical problems, the invention adopts the following technical scheme: a process for preparing high purity nitrogen trifluoride comprising the steps of:
s1, fluorine gas and ammonia gas are independently introduced into protective gas in sequence, and mixed gas is obtained after mixing; the mixed gas reacts for 3 to 24 hours at the temperature of-20 to 30 ℃ to obtain mixed gas containing hydrogen fluoride, nitrogen trifluoride and protective gas;
the reaction temperature may be-20 ℃, -15 ℃, -10 ℃, -5 ℃, 0 ℃, 5 ℃, 10 ℃, 15 ℃, 20 ℃, 25 ℃ or 30 ℃ and the reaction time may be 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h or 24h;
s2, adsorbing the mixed gas containing the hydrogen fluoride, the nitrogen trifluoride and the protective gas obtained in the step S1 by using a hydrogen fluoride adsorbent to obtain a purified mixed gas;
s3, condensing and separating the purified mixed gas obtained in the step S2 to obtain high-purity nitrogen trifluoride.
Preferably, the molar ratio of fluorine gas to ammonia gas in the mixed gas in the step S1 is (2-5): 1, which can be 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1 or 5:1; the molar concentration of the fluorine gas in the mixed gas is 2-15 mol%, and can be 2mol%, 3mol%, 4mol%, 5mol%, 6mol%, 7mol%, 8mol%, 9mol%, 10mol%, 11mol%, 12mol%, 13mol%, 14mol% or 15mol%; the molar concentration of ammonia in the mixed gas is 1 to 3mol%, and may be 1mol%, 1.2mol%, 1.5mol%, 1.7mol%, 2mol%, 2.2mol%, 2.5mol%, 2.7mol% or 3mol%.
Preferably, the temperature of the adsorption in S2 is-5-30 ℃; the adsorption is performed in an adsorption device, and the flow rate of the gas mixture containing hydrogen fluoride, nitrogen trifluoride and protective gas, which is introduced into the adsorption device, is 5-30 ml/s, and may be 5ml/s, 7ml/s, 9ml/s, 10ml/s, 12ml/s, 14ml/s, 1ml/s, 18ml/s, 20ml/s, 22ml/s, 24ml/s, 26ml/s, 28ml/s or 30ml/s. The temperature of adsorption may be-5 ℃, -2 ℃, -1 ℃, 0 ℃, 2 ℃, 5 ℃, 10 ℃, 15 ℃, 20 ℃, 25 ℃ or 30 ℃.
Preferably, the hydrogen fluoride adsorbent in S2 is made of polyacrylonitrile and a compound, wherein the mass ratio of the compound to the polyacrylonitrile is 1 (0.2-5), and the compound can be 1:0.2, 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5 or 1:5; the compound is alkali metal fluoride, alkaline earth metal fluoride or alkali metal fluorine hydride.
Preferably, the alkali metal fluoride is lithium fluoride, potassium fluoride or sodium fluoride; the alkaline earth metal fluoride is barium fluoride, calcium fluoride or magnesium fluoride; the alkali metal fluorine hydride compound is lithium fluoride, potassium fluoride or sodium fluoride.
Preferably, the preparation method of the hydrogen fluoride adsorbent comprises the following steps: the compound and polyacrylonitrile are subjected to solid-solid mixing, and then are crushed and molded sequentially to obtain a molded mixture; carrying out first heat treatment on the molding mixture in air, and then carrying out second heat treatment on the molding mixture in protective gas to obtain a hydrogen fluoride adsorbent; the protective gas is nitrogen, argon or ammonia.
Preferably, the particle size of the crushed particles is 130 to 200 meshes, which can be 130 meshes, 140 meshes, 150 meshes, 160 meshes, 170 meshes, 180 meshes, 190 meshes or 200 meshes; the shape of the molding mixture is spherical, cylindrical or sheet; the first heat treatment comprises a first heating and a first heat preservation which are sequentially carried out, wherein the heating rate of the first heating is 2-12 ℃/min, which can be 2 ℃/min, 3 ℃/min, 4 ℃/min, 5 ℃/min, 6 ℃/min, 7 ℃/min, 8 ℃/min, 9 ℃/min, 10 ℃/min, 11 ℃/min or 12 ℃/min, the end point temperature is 260-320 ℃, which can be 260 ℃, 270 ℃, 280 ℃, 290 ℃ or 300 ℃, and the time of the first heat preservation is 1.5-3 h, which can be 1.5h, 1.7h, 2h, 2.2h, 2.4h, 2.6h, 2.8h or 3h; the second heat treatment comprises sequentially performing second heating and second heat preservation, wherein the heating rate of the second heating is 2-12 ℃/min, which can be 2 ℃/min, 3 ℃/min, 4 ℃/min, 5 ℃/min, 6 ℃/min, 7 ℃/min, 8 ℃/min, 9 ℃/min, 10 ℃/min, 11 ℃/min or 12 ℃/min, the end point temperature is 540-640 ℃, which can be 540 ℃, 550 ℃, 560 ℃, 570 ℃, 580 ℃, 590 ℃, 600 ℃, 610 ℃, 620 ℃, 630 ℃ or 640 ℃, and the time of the second heat preservation is 1-2 h, which can be 1h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2h; the protective gas is nitrogen, argon or ammonia.
Preferably, the condensation separation in S3 includes a first condensation separation and a second condensation separation performed sequentially, wherein the temperature of the first condensation separation is-30 to-15 ℃, and the first condensation separation can be-30 ℃, -28 ℃, -26 ℃, -24 ℃, -22 ℃, -20 ℃, -19 ℃, -17 ℃ or-15 ℃, and the condensation medium is a mixed solution of ethylene glycol and water; the temperature of the second condensation separation is-150 to-130 ℃, and can be-150 ℃, -148 ℃, -146 ℃, -144 ℃, -142 ℃, -140 ℃, -138 ℃, -136 ℃, -134 ℃, -132 ℃ or-130 ℃, and the condensation medium is liquid nitrogen.
Preferably, the protective gas is nitrogen, argon or ammonia.
Also provided is the use of the high purity nitrogen trifluoride produced by the above production method for use in the microelectronics industry.
Compared with the prior art, the invention has the following advantages:
the invention prepares the crude NF through the reaction after mixing fluorine gas, ammonia gas and protective gas 3 The gas is passed through hydrogen fluoride adsorbent to obtain crude NF 3 The hydrogen fluoride impurity gas in the gas is subjected to preliminary adsorption to obtain purified mixed gas, and the purified mixed gas is subjected to condensation separation to further remove the hydrogen fluoride impurity gas and other impurity gases, so that nitrogen trifluoride with higher purity is obtained; the nitrogen trifluoride gas prepared by the preparation method of the high-purity nitrogen trifluoride has higher purity, simple preparation process and higher preparation efficiency, does not generate a large amount of wastewater polluting the environment, and is easy to be applied to industrial production on a large scale.
The present invention will be described in further detail with reference to examples.
Detailed Description
Example 1
The preparation method of the high-purity nitrogen trifluoride comprises the following steps:
s1, introducing fluorine gas into nitrogen, and then introducing ammonia gas, wherein the molar ratio of the fluorine gas to the ammonia gas is 4:1, and mixing to obtain mixed gas, wherein the molar concentration of the fluorine gas in the mixed gas is 8mol% and the molar concentration of the ammonia gas is 2mol%; the mixed gas reacts for 18 hours at the temperature of minus 10 ℃ to obtain mixed gas containing hydrogen fluoride, nitrogen trifluoride and nitrogen;
s2, introducing the mixed gas containing hydrogen fluoride, nitrogen trifluoride and nitrogen obtained in the step S1 into an adsorption device at a gas flow rate of 18ml/S, and adsorbing the mixed gas in the adsorption device by using a hydrogen fluoride adsorbent at a temperature of 20 ℃ to obtain a purified mixed gas;
s3, performing first condensation separation on the purified mixed gas obtained in the S2 by taking a mixed solution of ethylene glycol and water as a condensing medium at the temperature of-25 ℃ to separate hydrogen fluoride liquid and non-condensable gas; and then, under the condition of the temperature of 140 ℃ below zero, liquid nitrogen is used as a condensing medium to carry out second condensation separation, and the nitrogen trifluoride liquid and nitrogen are separated to obtain high-purity nitrogen trifluoride.
The preparation method of the hydrogen fluoride adsorbent comprises the following steps: and (3) carrying out solid-solid mixing on sodium fluoride and polyacrylonitrile in a mass ratio of 1:3, crushing the mixture obtained by solid-solid mixing into 160-mesh powder, preparing the powder into a flaky molding mixture, heating the molding mixture to 290 ℃ at a heating rate of 7 ℃/min in air and preserving heat for 2.2 hours, heating the molding mixture to 600 ℃ at a heating rate of 5 ℃/min in argon and preserving heat for 1.5 hours to obtain the hydrogen fluoride adsorbent.
Example 2
The preparation method of the high-purity nitrogen trifluoride comprises the following steps:
s1, introducing fluorine gas into argon, then introducing ammonia gas, wherein the molar ratio of the fluorine gas to the ammonia gas is 4:1, and mixing to obtain mixed gas, wherein the molar concentration of the fluorine gas in the mixed gas is 12mol% and the molar concentration of the ammonia gas is 3mol%; the mixed gas reacts for 14 hours at the temperature of 5 ℃ to obtain mixed gas containing hydrogen fluoride, nitrogen trifluoride and argon;
s2, introducing the mixed gas containing hydrogen fluoride, nitrogen trifluoride and argon obtained in the step S1 into an adsorption device at a gas flow rate of 24ml/S, and adsorbing the mixed gas in the adsorption device by using a hydrogen fluoride adsorbent at a temperature of 12 ℃ to obtain a purified mixed gas;
s3, performing first condensation separation on the purified mixed gas obtained in the S2 by taking a mixed solution of ethylene glycol and water as a condensing medium at the temperature of minus 28 ℃ to separate hydrogen fluoride liquid and non-condensable gas; and then, under the condition of the temperature of minus 135 ℃, liquid nitrogen is used as a condensing medium to carry out second condensation separation, and nitrogen trifluoride liquid and argon are separated to obtain high-purity nitrogen trifluoride.
The preparation method of the hydrogen fluoride adsorbent comprises the following steps: and (3) carrying out solid-solid mixing on calcium fluoride and polyacrylonitrile in a mass ratio of 1:1, crushing the mixture obtained by the solid-solid mixing into powder with the particle size of 180 meshes, preparing the powder into a spherical molding mixture, heating the molding mixture to 275 ℃ at a heating rate of 5 ℃/min in air, preserving heat for 2.6 hours, heating the molding mixture to 620 ℃ at a heating rate of 7 ℃/min in argon, and preserving heat for 1.2 hours to obtain the hydrogen fluoride adsorbent.
Example 3
The preparation method of the high-purity nitrogen trifluoride comprises the following steps:
s1, firstly introducing ammonia gas into helium gas, then introducing fluorine gas, wherein the molar ratio of the fluorine gas to the ammonia gas is 2.5:1, and mixing to obtain mixed gas, wherein the molar concentration of the fluorine gas in the mixed gas is 5mol%, and the molar concentration of the ammonia gas is 2mol%; the mixed gas reacts for 8 hours at the temperature of 15 ℃ to obtain mixed gas containing hydrogen fluoride, nitrogen trifluoride and helium;
s2, introducing the mixed gas containing hydrogen fluoride, nitrogen trifluoride and helium obtained in the step S1 into an adsorption device at a gas flow rate of 5ml/S, and adsorbing the mixed gas in the adsorption device by using a hydrogen fluoride adsorbent at a temperature of 5 ℃ to obtain a purified mixed gas;
s3, performing first condensation separation on the purified mixed gas obtained in the S2 by taking a mixed solution of ethylene glycol and water as a condensing medium at the temperature of-15 ℃ to separate hydrogen fluoride liquid and non-condensable gas; and then, under the condition of the temperature of 145 ℃ below zero, liquid nitrogen is used as a condensing medium to perform second condensation separation, and nitrogen trifluoride liquid and helium are separated to obtain high-purity nitrogen trifluoride.
The preparation method of the hydrogen fluoride adsorbent comprises the following steps: and (3) carrying out solid-solid mixing on barium fluoride and polyacrylonitrile in a mass ratio of 1:0.2, crushing the mixture obtained by the solid-solid mixing into 130-mesh powder, preparing the powder into a flaky molding mixture, heating the molding mixture to 320 ℃ at a heating rate of 12 ℃/min in air and preserving heat for 1.5 hours, heating the molding mixture to 570 ℃ at a heating rate of 10 ℃/min in argon and preserving heat for 1.8 hours to obtain the hydrogen fluoride adsorbent.
Example 4
The preparation method of the high-purity nitrogen trifluoride comprises the following steps:
s1, firstly introducing ammonia gas into nitrogen, then introducing fluorine gas, wherein the molar ratio of the fluorine gas to the ammonia gas is 3:1, and mixing to obtain mixed gas, wherein the molar concentration of the fluorine gas in the mixed gas is 3mol% and the molar concentration of the ammonia gas is 1mol%; the mixed gas reacts for 3 hours at the temperature of 30 ℃ to obtain mixed gas containing hydrogen fluoride, nitrogen trifluoride and nitrogen;
s2, introducing the mixed gas containing hydrogen fluoride, nitrogen trifluoride and nitrogen obtained in the step S1 into an adsorption device at a gas flow rate of 12ml/S, and adsorbing the mixed gas in the adsorption device by using a hydrogen fluoride adsorbent at a temperature of 30 ℃ to obtain a purified mixed gas;
s3, performing first condensation separation on the purified mixed gas obtained in the S2 by taking a mixed solution of ethylene glycol and water as a condensing medium at the temperature of-20 ℃ to separate hydrogen fluoride liquid and non-condensable gas; and then, under the condition of the temperature of minus 130 ℃, liquid nitrogen is used as a condensing medium to carry out second condensation separation, and nitrogen trifluoride liquid and nitrogen are separated to obtain high-purity nitrogen trifluoride.
The preparation method of the hydrogen fluoride adsorbent comprises the following steps: and (3) carrying out solid-solid mixing on sodium fluohydride and polyacrylonitrile in a mass ratio of 1:0.5, crushing the mixture obtained by the solid-solid mixing into 150-mesh powder, preparing the powder into a flaky molding mixture, heating the molding mixture to 260 ℃ at a heating rate of 10 ℃/min in air and preserving heat for 3 hours, heating the molding mixture to 540 ℃ at a heating rate of 2 ℃/min in argon and preserving heat for 2 hours, and thus obtaining the hydrogen fluoride adsorbent.
Example 5
The preparation method of the high-purity nitrogen trifluoride comprises the following steps:
s1, firstly introducing ammonia gas into nitrogen, then introducing fluorine gas, wherein the molar ratio of the fluorine gas to the ammonia gas is 5:1, and mixing to obtain mixed gas, wherein the molar concentration of the fluorine gas in the mixed gas is 15mol% and the molar concentration of the ammonia gas is 3mol%; the mixed gas reacts for 24 hours at the temperature of minus 20 ℃ to obtain mixed gas containing hydrogen fluoride, nitrogen trifluoride and argon;
s2, introducing the mixed gas containing hydrogen fluoride, nitrogen trifluoride and argon obtained in the step S1 into an adsorption device at a gas flow rate of 30ml/S, and adsorbing the mixed gas in the adsorption device by using a hydrogen fluoride adsorbent at a temperature of-5 ℃ to obtain a purified mixed gas;
s3, performing first condensation separation on the purified mixed gas obtained in the S2 by taking a mixed solution of ethylene glycol and water as a condensing medium at the temperature of minus 30 ℃ to separate hydrogen fluoride liquid and non-condensable gas; and then, under the condition of the temperature of-150 ℃, liquid nitrogen is used as a condensing medium to perform second condensation separation, and nitrogen trifluoride liquid and argon are separated to obtain high-purity nitrogen trifluoride.
The preparation method of the hydrogen fluoride adsorbent comprises the following steps: and (3) carrying out solid-solid mixing on potassium fluoride and polyacrylonitrile in a mass ratio of 1:5, crushing the mixture obtained by the solid-solid mixing into 200-mesh powder, preparing the spherical molding mixture from the powder, heating the molding mixture to 310 ℃ at a heating rate of 2 ℃/min in air, preserving heat for 1.8 hours, heating to 640 ℃ at a heating rate of 12 ℃/min in argon, and preserving heat for 1 hour to obtain the hydrogen fluoride adsorbent.
Comparative example 1
The comparative example of the method for producing high-purity nitrogen trifluoride is exactly the same as that of example 1, except that the fluorine gas and the ammonia gas are mixed and then introduced into the shielding gas in S1.
Comparative example 2
The preparation method of the high-purity nitrogen trifluoride of the comparative example is completely the same as that of the high-purity nitrogen trifluoride of example 1, except that the molar ratio of fluorine gas to ammonia gas in S1 is 1:1, the molar concentration of fluorine gas in the mixed gas is 5mol%, and the molar concentration of ammonia gas is 5mol%.
Comparative example 3
The preparation method of the high-purity nitrogen trifluoride of the comparative example is exactly the same as that of the high-purity nitrogen trifluoride of example 1, except that the molar ratio of fluorine gas to ammonia gas in S1 is 7:1, the molar concentration of fluorine gas in the mixed gas is 8.75mol%, and the molar concentration of ammonia gas is 1.25mol%.
Comparative example 4
The process for preparing the high-purity nitrogen trifluoride of this comparative example is exactly the same as that of example 1, except that the mixed gas in S1 is reacted at a temperature of-50 ℃.
Comparative example 5
The process for producing high-purity nitrogen trifluoride of this comparative example is exactly the same as that of example 1, except that the mixed gas in S1 is reacted at a temperature of 50 ℃.
Comparative example 6
The process for producing high-purity nitrogen trifluoride of this comparative example is exactly the same as that of example 1, except that pyridine is used as the hydrogen fluoride adsorbent in S2.
Comparative example 7
The method for producing high-purity nitrogen trifluoride of this comparative example is exactly the same as that of example 1, except that the nitrogen gas in S1 is replaced with air.
Comparative example 8
The production method of the high-purity nitrogen trifluoride of this comparative example is exactly the same as that of example 1, except that the step S2 is not performed.
The results of testing the high purity nitrogen trifluoride produced in examples 1 to 5 and comparative examples 1 to 8 to obtain the purity of the high purity nitrogen trifluoride are shown in Table 1, and the fluorine-based and ammonia-based yields of the high purity nitrogen trifluoride produced in examples 1 to 5 and comparative examples 1 to 8 are shown in Table 1.
TABLE 1
From table 1:
(1) The high-purity nitrogen trifluoride prepared in the examples 1-5 has higher purity and higher yield, the crude nitrogen trifluoride gas is prepared by mixing fluorine gas, ammonia gas and protective gas and then reacting, hydrogen fluoride impurity gas in the crude nitrogen trifluoride gas is subjected to preliminary adsorption by a hydrogen fluoride adsorbent to obtain purified mixed gas, and the purified mixed gas is subjected to condensation separation to further remove the hydrogen fluoride impurity gas and other impurity gases, so that the nitrogen trifluoride with higher purity is obtained;
(2) As is clear from the comparison between example 1 and comparative example 1, the way of introducing fluorine gas and ammonia gas into the protective gas in the present invention affects the purity and yield of nitrogen trifluoride, and if fluorine gas and ammonia gas are mixed first and then introduced into the diluent gas, fluorine gas and ammonia gas react first and produce impurity gas, thereby reducing the purity and yield of nitrogen trifluoride;
(3) As is clear from the comparison of example 1 with comparative examples 2 and 3, the molar ratio of fluorine gas to ammonia gas in the present invention affects the yield of nitrogen trifluoride, and when the molar ratio of fluorine gas to ammonia gas is too low, the yield of fluorine gas is increased, but the yield of ammonia gas is greatly reduced, and the requirement of actual production is not satisfied; when the molar ratio of fluorine gas to ammonia gas is too high, the yield of ammonia gas is increased, but the yield of fluorine gas is greatly reduced, and the actual production requirement is not met;
(4) As is clear from the comparison of the example 1 and the comparative examples 4 and 5, the temperature of the mixed gas reaction in the invention affects the yield and purity of nitrogen trifluoride, and when the temperature of the mixed gas reaction is lower, the reaction rate of fluorine gas and ammonia gas is slower, thus greatly reducing the production efficiency and also reducing the yield; when the reaction temperature of the mixed gas is higher, side reaction can be generated when fluorine gas reacts with ammonia gas, so that impurity gas is generated, and yield can be reduced;
(5) As is apparent from a comparison of example 1 and comparative example 6, the hydrogen fluoride adsorbent prepared by the preparation method of the hydrogen fluoride adsorbent of the present invention can adsorb hydrogen fluoride in the mixed gas better than the conventional adsorbent, thereby improving the purity of nitrogen trifluoride;
(6) As can be seen from the comparison between the embodiment 1 and the comparative example 7, the mixed gas is obtained by introducing fluorine gas and ammonia gas into protective gas for reaction, and in the protective gas, the fluorine gas and the ammonia gas can smoothly react to obtain nitrogen trifluoride, and a large amount of gas impurities can not be generated due to a large amount of side reactions, so that the nitrogen trifluoride with higher purity can be obtained;
(7) As is apparent from a comparison between example 1 and comparative example 8, the adsorption of the mixed gas using the hydrogen fluoride adsorbent in the present invention is advantageous in improving the purity of nitrogen trifluoride, and the hydrogen fluoride adsorbent is capable of preliminarily adsorbing the hydrogen fluoride gas in the mixed gas, and the hydrogen fluoride gas is further adsorbed in the subsequent process, thereby resulting in a higher purity of the obtained nitrogen trifluoride.
In conclusion, the nitrogen trifluoride gas prepared by the preparation method of the high-purity nitrogen trifluoride has higher purity, simple preparation process and higher preparation efficiency, does not generate a large amount of wastewater polluting the environment, and is easy to be applied to industrial production on a large scale.
The above description is only of the preferred embodiments of the present invention, and is not intended to limit the present invention. Any simple modification, variation and equivalent variation of the above embodiments according to the technical substance of the invention still fall within the scope of the technical solution of the invention.
Claims (10)
1. A method for preparing high-purity nitrogen trifluoride, which is characterized by comprising the following steps:
s1, fluorine gas and ammonia gas are independently introduced into protective gas in sequence, and mixed gas is obtained after mixing; the mixed gas reacts for 3 to 24 hours at the temperature of-20 to 30 ℃ to obtain mixed gas containing hydrogen fluoride, nitrogen trifluoride and protective gas;
s2, adsorbing the mixed gas containing the hydrogen fluoride, the nitrogen trifluoride and the protective gas obtained in the step S1 by using a hydrogen fluoride adsorbent to obtain a purified mixed gas;
s3, condensing and separating the purified mixed gas obtained in the step S2 to obtain high-purity nitrogen trifluoride.
2. The method according to claim 1, wherein the molar ratio of fluorine gas to ammonia gas in the mixed gas in S1 is (2-5): 1; the molar concentration of fluorine in the mixed gas is 2-15 mol%, and the molar concentration of ammonia is 1-3 mol%.
3. The method according to claim 1, wherein the temperature of adsorption in S2 is-5 to 30 ℃; the adsorption is carried out in an adsorption device, and the gas flow rate of the mixed gas containing hydrogen fluoride, nitrogen trifluoride and protective gas which is introduced into the adsorption device is 5-30 ml/s.
4. The preparation method according to claim 3, wherein the hydrogen fluoride adsorbent in S2 is prepared from polyacrylonitrile and a compound, and the mass ratio of the compound to the polyacrylonitrile is 1 (0.2-5); the compound is alkali metal fluoride, alkaline earth metal fluoride or alkali metal fluorine hydride.
5. The method according to claim 4, wherein the alkali metal fluoride is lithium fluoride, potassium fluoride or sodium fluoride; the alkaline earth metal fluoride is barium fluoride, calcium fluoride or magnesium fluoride; the alkali metal fluorine hydride compound is lithium fluoride, potassium fluoride or sodium fluoride.
6. The method according to claim 5, wherein the method for producing the hydrogen fluoride adsorbent comprises: the compound and polyacrylonitrile are subjected to solid-solid mixing, and then are crushed and molded sequentially to obtain a molded mixture; and (3) carrying out first heat treatment on the molding mixture in air, and then carrying out second heat treatment on the molding mixture in protective gas to obtain the hydrogen fluoride adsorbent.
7. The method according to claim 6, wherein the crushed particles have a particle diameter of 130 to 200 mesh, and the molded mixture has a spherical, cylindrical or flaky shape; the first heat treatment comprises a first heating and a first heat preservation which are sequentially carried out, wherein the heating rate of the first heating is 2-12 ℃/min, the end temperature is 260-320 ℃, and the time of the first heat preservation is 1.5-3 h; the second heat treatment comprises sequentially performing second heating and second heat preservation, wherein the heating rate of the second heating is 2-12 ℃/min, the end temperature is 540-640 ℃, and the time of the second heat preservation is 1-2 h; the protective gas is nitrogen, argon or ammonia.
8. The preparation method according to claim 1, wherein the condensation separation in S3 comprises a first condensation separation and a second condensation separation which are sequentially performed, the temperature of the first condensation separation is-30 to-15 ℃, and the condensation medium is a mixed solution of glycol and water; the temperature of the second condensation separation is-150 to-130 ℃, and the condensing medium is liquid nitrogen.
9. The method of claim 1, wherein the protective gas is nitrogen, argon or ammonia.
10. Use of the high purity nitrogen trifluoride produced by the production process as claimed in any one of claims 1-9, characterized in that the high purity nitrogen trifluoride is used in the microelectronics industry.
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