Preparation method of hydrophobic tritium oxidation catalyst and tritium-containing waste gas treatment method

Abstract

The invention relates to a preparation method of a hydrophobic tritium oxidation catalyst and a tritium-containing waste gas treatment method. The preparation method comprises the following steps: adding a hydrophobic molecular sieve into an ammonium nitrate solution for reaction, then washing to be neutral, and drying to obtain a pretreated molecular sieve; and loading noble metal on the pretreated molecular sieve by adopting an ion exchange method to obtain the hydrophobic tritium oxidation catalyst. On the basis of a method for loading noble metal on the hydrophobic molecular sieve, the conversion rate of the catalyst under high humidity can be remarkably improved, and the catalyst has relatively high catalytic stability and can still keep high catalytic conversion rate after being used for a long time.

Description

Technical Field

[0001] This invention relates to the field of deacidification process technology in the nuclear industry, and particularly to a method for preparing a hydrophobic tritium oxidation catalyst and a method for treating tritium-containing waste gas. Background Technology

[0002] In nuclear industry production processes, the treatment of tritium-containing waste gas is crucial. Catalytic oxidation, a commonly used method, relies on catalysts to oxidize tritium gas into tritium water. However, traditional precious metal catalysts are highly susceptible to environmental humidity when treating tritium-containing waste gas. When the water vapor content in the waste gas is high, the water vapor adsorbs on the catalyst surface, occupying active sites and hindering the contact between tritium gas and the active centers of the catalyst, leading to a significant reduction in catalyst activity or even deactivation.

[0003] In actual nuclear facility operation, when using traditional precious metal catalysts to treat tritium-containing waste gas, the oxidation conversion rate of tritium gas drops sharply from over 90% under normal operating conditions to below 60% in high humidity environments, severely affecting the treatment efficiency and effectiveness of tritium-containing waste gas. These problems urgently need to be addressed. Summary of the Invention

[0004] This invention discloses a method for preparing a hydrophobic tritium oxidation catalyst and a method for treating tritium-containing waste gas, aiming to solve the technical problems existing in the prior art.

[0005] The present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing a hydrophobic tritium oxidation catalyst, comprising the following steps: Hydrophobic molecular sieves were added to ammonium nitrate solution for reaction, and then washed until neutral and dried to obtain pretreated molecular sieves. The pretreated molecular sieve was loaded with noble metals using an ion exchange method to obtain a hydrophobic tritium oxidation catalyst.

[0006] In the preparation method of the hydrophobic tritium oxidation catalyst of the present invention, the step of washing to neutrality and drying to obtain the pretreated molecular sieve includes: After washing with deionized water until neutral, the molecular sieve is dried at 100-120℃ for 12-16 hours to obtain the pretreated molecular sieve.

[0007] In the preparation method of the hydrophobic tritium oxidation catalyst of the present invention, the hydrophobic molecular sieve is ZSM-5 molecular sieve or Y-type molecular sieve.

[0008] In the preparation method of the hydrophobic tritium oxidation catalyst of the present invention, the concentration of the ammonium nitrate solution in the step of adding the hydrophobic molecular sieve to the ammonium nitrate solution for reaction is 0.1-0.5 mol / L, and the reaction temperature is 60-80℃.

[0009] In the preparation method of the hydrophobic tritium oxidation catalyst of the present invention, the concentration of the ammonium nitrate solution is 0.5 mol / L and the reaction temperature is 80°C.

[0010] In the preparation method of the hydrophobic tritium oxidation catalyst of the present invention, in the step of loading noble metals onto the pretreated molecular sieve by ion exchange, the noble metals are platinum and / or palladium, and the loading amount is 0.1-5% of the mass of the hydrophobic tritium oxidation catalyst.

[0011] In the preparation method of the hydrophobic tritium oxidation catalyst of the present invention, the loading of the noble metal is 1% of the mass of the hydrophobic tritium oxidation catalyst.

[0012] In the preparation method of the hydrophobic tritium oxidation catalyst of the present invention, the step of loading noble metals onto the pretreated molecular sieve by ion exchange to obtain the hydrophobic tritium oxidation catalyst includes: Prepare a soluble salt solution of a precious metal, specifically an aqueous solution of a soluble salt, wherein the soluble salt may be palladium nitrate and / or chloroplatinic acid; the concentration of the soluble salt solution is 0.1-0.3 mol / L; The pretreated molecular sieve is added to the soluble salt solution, and the ratio of the molecular sieve to the soluble salt solution is 1g:200ml; Stirring at room temperature for 12-24 hours, then filtering, washing with deionized water until no precious metal residue remains, and drying. The dried molecular sieve was calcined to obtain the hydrophobic tritium oxidation catalyst.

[0013] In the preparation method of the hydrophobic tritium oxidation catalyst of the present invention, the drying temperature in the drying step is 100-120°C and the drying time is 6-12 hours.

[0014] In the preparation method of the hydrophobic tritium oxidation catalyst of the present invention, the calcination temperature in the calcination step is 300-500℃ and the calcination time is 2-4 hours.

[0015] In the preparation method of the hydrophobic tritium oxidation catalyst of the present invention, the calcination temperature in the calcination step is 4500°C and the calcination time is 3 hours.

[0016] In the preparation method of the hydrophobic tritium oxidation catalyst of the present invention, the hydrophobic molecular sieve is an alkylsilylated modified molecular sieve, and the modification steps are as follows: Molecular sieves are calcined. The calcined molecular sieve is added to an organic solution of methyltriethoxysilane or phenyltrimethoxysilane, wherein the mass percentage concentration of methyltriethoxysilane or phenyltrimethoxysilane in the organic solution is 5-20%, and the solvent is toluene. After stirring and reacting for 3 hours in a nitrogen atmosphere at a temperature of 50-120℃, the molecular sieve is separated and dried to obtain the hydrophobic molecular sieve.

[0017] In the preparation method of the hydrophobic tritium oxidation catalyst of the present invention, the molecular sieve is ZSM-5 molecular sieve or Y-type molecular sieve.

[0018] In the preparation method of the hydrophobic tritium oxidation catalyst of the present invention, in the step of calcining the molecular sieve, the calcination temperature is 550-650℃ and the calcination time is 4-6 hours.

[0019] Secondly, the present invention also provides a method for treating tritium-containing waste gas, which includes the following steps: Tritium-containing waste gas is introduced into a container loaded with a hydrophobic tritium oxidation catalyst, and the reaction is carried out at a temperature of 60-200°C. The hydrophobic tritium oxidation catalyst is prepared by any of the methods described above.

[0020] In the preparation method of the hydrophobic tritium oxidation catalyst of the present invention, the reaction temperature is 200°C.

[0021] The technical solution adopted in this invention can achieve the following beneficial effects: This invention mainly provides a method for preparing a hydrophobic noble metal molecular sieve tritium oxidation catalyst and a method for treating tritium-containing waste gas. Based on the method of loading noble metals onto hydrophobic molecular sieves, the conversion rate of the catalyst under high humidity can be significantly improved, and it has high catalytic stability, maintaining a high catalytic conversion rate even after long-term use. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. In the description of this invention, it should be noted that the term "or" is generally used to include the meaning of "and / or," unless otherwise expressly indicated.

[0023] Unless explicitly stated otherwise, the numerical parameters in this specification and the appended claims may be approximate values ​​and can be varied according to the desired characteristics obtained from the content of this invention. Specifically, all figures used in the specification and claims to indicate the content of composition, reaction conditions, etc., should be understood to be modified by the term "about" in all cases. Generally, this means that there may be variations of ±10% in some embodiments, ±5% in some embodiments, ±1% in some embodiments, and ±0.5% in some embodiments.

[0024] Furthermore, the word "comprising" does not exclude the presence of materials or steps not listed in the claims. The ordinal numbers used in the specification and claims, such as "first," "second," "third," and Arabic numerals and letters, to modify corresponding elements or steps, do not in themselves imply an order of manufacturing process; their use is solely to ensure clear distinction between steps.

[0025] Furthermore, unless otherwise specified or required to occur in a specific order, the order of the above steps is not limited to those listed above and can be varied or rearranged according to the desired design. Moreover, the above embodiments can be used in combination with each other or with other embodiments based on design and reliability considerations; that is, technical features from different embodiments can be freely combined to form more embodiments.

[0026] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0027] To address the problems existing in the prior art, this application provides a method for preparing a hydrophobic tritium oxidation catalyst and a method for treating tritium-containing waste gas.

[0028] Example 1 S1. The ZSM-5 molecular sieve hydrophobic molecular sieve is calcined; S2. The calcined molecular sieve is added to a mixed organic solution of methyltriethoxysilane and toluene with a mass percentage concentration of 8%. S3. Under a nitrogen atmosphere and at a temperature of 80°C, the reaction was stirred for 3 hours. The molecular sieve was then separated and dried to obtain a hydrophobic molecular sieve. S4. The hydrophobic molecular sieve is added to a 0.5 mol / L ammonium nitrate solution for reaction at 80℃; then, it is washed until neutral and dried to obtain the pretreated molecular sieve. S5. The pretreated molecular sieve is loaded with the noble metal platinum by ion exchange method to obtain a hydrophobic tritium oxidation catalyst; the loading amount of the noble metal is 1% of the mass of the hydrophobic tritium oxidation catalyst.

[0029] Example 2 The difference between this embodiment and embodiment 1 is that steps S2 and S3 are not included; the rest is the same as in embodiment 1.

[0030] Example 3 The difference between this embodiment and Embodiment 1 is that step S2 is a mixed solution of phenyltrimethoxysilane and toluene; the rest is the same as in Embodiment 1.

[0031] Example 4 The difference between this embodiment and Embodiment 1 is that the mass percentage concentration in step S2 is 20% and the temperature in step S3 is 120°C; the rest is the same as in Embodiment 1.

[0032] Example 5 The difference between this embodiment and Embodiment 1 is that the mass percentage concentration in step S2 is 5% and the temperature in step S3 is 50°C; the rest is the same as in Embodiment 1.

[0033] Example 6 The difference between this embodiment and Embodiment 1 is that the concentration of the ammonium nitrate solution in step S4 is 0.1 mol / L, and the reaction temperature is 60°C; the rest is the same as in Embodiment 1.

[0034] Example 7 The difference between this embodiment and Embodiment 1 is that the concentration of the ammonium nitrate solution in step S4 is 0.3 mol / L, and the reaction temperature is 70°C; the rest is the same as in Embodiment 1.

[0035] Example 8 The difference between this embodiment and Embodiment 1 is that step S5 involves loading the noble metal palladium; the rest is the same as in Embodiment 1.

[0036] Example 9 The difference between this embodiment and embodiment 1 is that the loading of precious metal in step S5 is 5%; the rest is the same as in embodiment 1.

[0037] Example 10 The difference between this embodiment and embodiment 1 is that the loading of precious metal in step S5 is 0.1%; the rest is the same as in embodiment 1.

[0038] Example 11 The difference between this embodiment and Embodiment 1 is that the loading amounts of the noble metals platinum and palladium in step S5 are 1% and 1%, respectively; the rest is the same as in Embodiment 1.

[0039] Example 12 The difference between this embodiment and Embodiment 1 is that the hydrophobic molecular sieve used in step S1 is a Y-type molecular sieve; the rest is the same as in Embodiment 1.

[0040] Comparative Example 1 The difference between this comparative example and Example 1 is that the reaction temperature in step S4 is 100°C; the rest is the same as in Example 1.

[0041] Comparative Example 2 The difference between this comparative example and Example 1 is that the concentration of the ammonium nitrate solution in step S4 is 0.7 mol / L; the rest is the same as in Example 1.

[0042] Comparative Example 3 The difference between this comparative example and Example 1 is that the load in step S5 is 7%; the rest is the same as in Example 1.

[0043] The hydrophobic tritium oxidation catalysts prepared in Examples 1-12 and Comparative Examples 1-3 were subjected to performance tests under the following conditions: A hydrophobic tritium oxidation catalyst was packed into a fixed-bed reactor and subjected to an oxidation reaction at 80 °C and a gas space velocity of 5000 h⁻¹. -1 The test was conducted under conditions of 12% oxygen content and 80% relative humidity. The test results are shown in Table 1 below. Table 1

[0044] The embodiments of the present invention have been described above. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of the present invention.

Claims

1. A method for preparing a hydrophobic tritium oxidation catalyst, characterized in that, Includes the following steps: Hydrophobic molecular sieves were added to ammonium nitrate solution for reaction, and then washed until neutral and dried to obtain pretreated molecular sieves. The pretreated molecular sieve was loaded with noble metals using an ion exchange method to obtain a hydrophobic tritium oxidation catalyst.

2. The method for preparing the hydrophobic tritium oxidation catalyst according to claim 1, characterized in that, In the step of adding hydrophobic molecular sieves to ammonium nitrate solution for reaction, the concentration of the ammonium nitrate solution is 0.1-0.5 mol / L, and the reaction temperature is 60-80℃.

3. The method for preparing the hydrophobic tritium oxidation catalyst according to claim 2, characterized in that, The concentration of the ammonium nitrate solution is 0.5 mol / L, and the reaction temperature is 80℃.

4. The method for preparing the hydrophobic tritium oxidation catalyst according to claim 1, characterized in that, In the step of loading noble metals onto the pretreated molecular sieve using ion exchange, the noble metals are platinum and / or palladium, and the loading amount is 0.1-5% of the mass of the hydrophobic tritium oxidation catalyst.

5. The method for preparing the hydrophobic tritium oxidation catalyst according to claim 4, characterized in that, The loading of the precious metal is 1% of the mass of the hydrophobic tritium oxidation catalyst.

6. The method for preparing the hydrophobic tritium oxidation catalyst according to claim 1, characterized in that, The step of loading noble metals onto the pretreated molecular sieve using an ion exchange method to obtain a hydrophobic tritium oxidation catalyst includes: Prepare a soluble salt solution of a precious metal, wherein the concentration of the soluble salt solution is 0.1-0.3 mol / L; The pretreated molecular sieve is added to the soluble salt solution, and the ratio of the molecular sieve to the soluble salt solution is 1g:200ml; Stir at room temperature for 12-24 hours, then filter and dry. The dried molecular sieve was calcined to obtain the hydrophobic tritium oxidation catalyst.

7. The method for preparing the hydrophobic tritium oxidation catalyst according to claim 6, characterized in that, The roasting temperature in the roasting step is 300-500℃, and the roasting time is 2-4 hours.

8. The method for preparing the hydrophobic tritium oxidation catalyst according to claim 1, characterized in that, The hydrophobic molecular sieve is an alkylsilane-modified molecular sieve, and the modification steps are as follows: Molecular sieves are calcined. The calcined molecular sieve is added to an organic solution of methyltriethoxysilane or phenyltrimethoxysilane, wherein the mass percentage concentration of methyltriethoxysilane or phenyltrimethoxysilane in the organic solution is 5-20%, and the solvent is toluene. After stirring and reacting for 3 hours in a nitrogen atmosphere at a temperature of 50-120℃, the molecular sieve is separated and dried to obtain the hydrophobic molecular sieve.

9. The method for preparing the hydrophobic tritium oxidation catalyst according to claim 8, characterized in that, In the step of calcining the molecular sieve, the calcination temperature is 550-650℃ and the calcination time is 4-6 hours.

10. A method for treating tritium-containing waste gas, characterized in that, Includes the following steps: Tritium-containing waste gas is introduced into a container loaded with a hydrophobic tritium oxidation catalyst, and the reaction is carried out at a temperature of 60-200°C; the hydrophobic tritium oxidation catalyst is prepared by the method described in any one of claims 1-9.

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