Preparation method and application of rare earth element-containing precious metal tritium oxidation catalyst

Abstract

The invention relates to a preparation method and application of a rare earth element-containing precious metal tritium oxidation catalyst. The preparation method comprises the following steps: preparing a gamma-Al2O3 carrier containing rare earth elements; and loading noble metal on the surface of the gamma-Al2O3 carrier by adopting a deposition-precipitation method to obtain the catalyst, immersing the catalyst into a solution containing a nonionic surfactant for surface modification; and roasting the modified catalyst to obtain the tritium oxidation catalyst. According to the invention, the catalytic performance under a high-humidity condition is improved by firstly loading the rare earth element, then loading the noble metal and finally modifying through the nonionic surfactant, and the low-temperature activity of the catalyst is improved through a composite active site formed by loading the rare earth element and the noble metal; and meanwhile, the reaction activity under the condition of low tritium concentration and the reaction activity under the conditions of high humidity and large air volume are also improved.

Description

Technical Field

[0001] This invention relates to the field of tritium removal catalyst technology, and in particular to a method for preparing and applying a precious metal tritium oxidation catalyst containing rare earth elements. Background Technology

[0002] Tritium, a radioactive nuclide, is generated during nuclear energy development and utilization, particularly during reactor operation and nuclear fuel reprocessing. Direct emission of tritium-containing waste gas without effective treatment poses potential hazards to the environment and human health.

[0003] Traditional precious metal tritium oxidation catalysts suffer from numerous problems. On one hand, the uneven dispersion of precious metals on the support leads to low utilization of active sites and poor overall catalytic performance. On the other hand, the poor catalytic performance of the active sites results in a slow reaction rate between tritium and oxygen, failing to meet the requirements for efficient treatment of tritium-containing waste gas. Studies have shown that the agglomeration of precious metal particles is common, burying some active sites and preventing them from fully exerting their catalytic effect. This leads to problems such as low conversion rates when treating water-containing waste gas, low activity at low temperatures, poor efficiency at low tritium concentrations, and insufficient adaptability to large flow rates. These problems urgently need to be addressed. Summary of the Invention

[0004] This invention discloses a method for preparing a precious metal tritium oxidation catalyst containing rare earth elements and its application, aiming to solve the technical problems existing in the prior art.

[0005] The present invention adopts the following technical solution: This invention provides a method for preparing a noble metal tritium oxidation catalyst containing rare earth elements, comprising the following steps: Prepare γ-Al2O3 supports containing rare earth elements, namely γ-Al2O3 particles with rare earth elements loaded on the surface. A catalyst was obtained by loading noble metals onto the surface of the γ-Al2O3 support using a deposition-precipitation method. The catalyst was surface modified by immersing it in a solution containing a nonionic surfactant. The modified catalyst was calcined to obtain a tritium oxidation catalyst.

[0006] In the preparation method of the rare earth element-containing noble metal tritium oxidation catalyst of the present invention, the rare earth element is cerium and / or lanthanum.

[0007] In the preparation method of the rare earth element-containing noble metal tritium oxidation catalyst of the present invention, the loading of the rare earth element is 1-10% of the mass of the γ-Al2O3 support. Within this range, the performance of the prepared tritium oxidation catalyst is better; exceeding the range will reduce the catalyst performance.

[0008] In the preparation method of the rare earth element-containing noble metal tritium oxidation catalyst of the present invention, the step of loading noble metals onto the surface of the γ-Al2O3 support by deposition-precipitation method to obtain the catalyst includes: Prepare a solution containing a noble metal precursor, wherein the noble metal precursor includes a Pt precursor and / or a Pd precursor; The γ-Al2O3 support was added to the solution; An alkaline precipitant was added dropwise to the solution to initiate a reaction. After the reaction was complete, the solution was washed with deionized water to obtain the catalyst.

[0009] In the preparation method of the rare earth element-containing noble metal tritium oxidation catalyst of the present invention, the heavy metal concentration in the solution is 0.01-0.1 mol / L, and the mass ratio of the γ-Al2O3 support to the solution is 1:10-1:20.

[0010] In the preparation method of the rare earth element-containing noble metal tritium oxidation catalyst of the present invention, the Pt precursor is chloroplatinic acid (H2PtCl6) or platinum nitrate (Pt(NO3)2); the Pd precursor is palladium acetate (C4H6O4Pd), palladium chloride (PdCl2) or palladium nitrate (Pd(NO3)2). In the preparation method of the rare earth element-containing noble metal tritium oxidation catalyst of the present invention, the step of adding an alkaline precipitant dropwise to the solution to carry out the reaction includes: Under stirring conditions, an alkaline precipitant is added dropwise to the solution until the pH of the solution is 8-10; The solution temperature was adjusted to 60-80℃, and the reaction was stirred continuously for 4-8 hours. Then, the solution was cooled to room temperature, filtered, and washed with deionized water until no chloride ions were found. The solution was then cooled to room temperature to obtain the catalyst.

[0011] In the preparation method of the rare earth element-containing noble metal tritium oxidation catalyst of the present invention, the alkaline precipitant is sodium carbonate or urea.

[0012] In the preparation method of the rare earth element-containing noble metal tritium oxidation catalyst of the present invention, the loading of the noble metal is 0.1-2% of the mass of the catalyst. Too low a loading: the support sites cannot be fully utilized, resulting in an increase in the amount of catalyst required to achieve the same catalytic effect in practical applications; too high a loading: the catalytic performance per unit mass of noble metal decreases, and the utilization rate of noble metal atoms is low.

[0013] In the preparation method of the rare earth element-containing noble metal tritium oxidation catalyst of the present invention, the surface modification step of immersing the catalyst in a solution containing a nonionic surfactant includes: The catalyst is immersed in a solution containing a nonionic surfactant, wherein the mass percentage concentration of the surfactant in the solution is 1-5%; the mass ratio of the catalyst to the surfactant solution is 1:1; both excessively high and excessively low surfactant concentrations will result in a reduction in the performance of the final tritium oxidation catalyst.

[0014] Stir at room temperature for 1-3 hours, then filter and dry at 60-80℃ for 6-12 hours.

[0015] In the preparation method of the rare earth element-containing noble metal tritium oxidation catalyst of the present invention, the nonionic surfactant is PEG-6000 (CAS: 25322-68-3) or P123 (CAS: 9003-11-6).

[0016] In the preparation method of the rare earth element-containing noble metal tritium oxidation catalyst of the present invention, the step of calcining the modified catalyst to obtain the tritium oxidation catalyst includes: The modified catalyst was heated to 200-300℃ under a nitrogen atmosphere and held at that temperature for 1-2 hours. Then, under a hydrogen atmosphere, the modified catalyst is heated to 300-400°C and held at that temperature for 2-4 hours; Finally, the mixture was cooled to room temperature under a nitrogen atmosphere to obtain the tritium oxidation catalyst. Purging with nitrogen followed by hydrogen helps to form stable, highly dispersed noble metal atoms or groups.

[0017] In the preparation method of the rare earth element-containing noble metal tritium oxidation catalyst of the present invention, the heating rate is 2-5℃ / min. If the heating rate is too slow, the preparation time will be prolonged; if the heating rate is too fast, the temperature of the material itself will change too quickly, which is not conducive to the stability and dispersion of the catalyst active centers.

[0018] In the preparation method of the rare earth element-containing noble metal tritium oxidation catalyst of the present invention, the step of preparing the rare earth element-containing γ-Al2O3 support includes: The pretreated γ-Al2O3 support (i.e., γ-Al2O3 particles) was added to a rare earth element nitrate solution and stirred until homogeneous. The solution is aged at 60-80°C for 2-4 hours; The solution is then dried to obtain a carrier powder; The carrier powder was calcined at 500-700℃ for 4-6 hours to obtain a γ-Al2O3 support containing rare earth elements. If the temperature is too low, the rare earth metals cannot form a good bond with γ-Al2O3, affecting the performance of the catalyst after subsequent noble metal loading.

[0019] In the preparation method of the rare earth element-containing noble metal tritium oxidation catalyst of the present invention, the rare earth element nitrate solution is cerium nitrate or lanthanum nitrate solution.

[0020] In the preparation method of the rare earth element-containing noble metal tritium oxidation catalyst of the present invention, the γ-Al2O3 support is a pretreated γ-Al2O3 support; the pretreatment step includes: The γ-Al2O3 support was calcined at 500-600℃ for 3-5 hours, and then cooled to room temperature. The γ-Al2O3 support was immersed in a 0.1-1 mol / L organic acid solution and stirred at 40-60°C for 2-4 hours. Then, it is washed with deionized water until neutral and dried at 100-120°C for 12 hours to obtain the pretreated γ-Al2O3 support.

[0021] In the preparation method of the rare earth element-containing noble metal tritium oxidation catalyst of the present invention, the organic acid solution is citric acid or oxalic acid solution.

[0022] In a second aspect, the present invention also provides the application of the tritium oxidation catalyst prepared by any of the above-described preparation methods in the treatment of tritium-containing waste gas. Specifically, the tritium oxidation catalyst is packed in a fixed-bed reactor, and the reaction is carried out at a temperature of 50-200°C, preferably 80-150°C; the gas space velocity is 5000-30000 h⁻¹, preferably 10000-20000 h⁻¹.

[0023] The technical solution adopted in this invention can achieve the following beneficial effects: This invention mainly provides a method for preparing a rare earth element-containing noble metal tritium oxidation catalyst. The method involves first loading rare earth elements, then loading noble metals, and finally modifying the catalyst with a nonionic surfactant. This improves the catalytic performance under high humidity conditions. Furthermore, the composite active sites formed by the rare earth elements and noble metal loading enhance the low-temperature activity of the catalyst, as well as the reaction activity under low tritium concentrations, high humidity conditions, and high airflow conditions. Detailed Implementation

[0024] 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.

[0025] 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.

[0026] 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.

[0027] Furthermore, unless specifically described 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.

[0028] 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.

[0029] To address the problems existing in the prior art, this application provides a method for preparing a precious metal tritium oxidation catalyst containing rare earth elements.

[0030] Example 1 S1. The γ-Al2O3 support was calcined at 550℃ for 4 hours, and then cooled to room temperature. S2. Immerse the γ-Al2O3 support in a 0.5 mol / L organic acid solution and stir at 50°C for 3 hours. S3. Then, wash with deionized water until neutral, and dry at 110°C for 12 hours to obtain the pretreated γ-Al2O3 support. S4. Add the pretreated γ-Al2O3 support to the lanthanum nitrate solution and stir until homogeneous; S5. Aging the solution at 70°C for 3 hours; S6. Then, the solution is spray-dried to obtain γ-Al2O3 support powder with a lanthanum loading of 6wt%. S7. The carrier powder was calcined at 600℃ for 5 hours to obtain a γ-Al2O3 carrier containing rare earth elements. S8. Prepare a solution containing chloroplatinic acid precursor; S9. Add the γ-Al2O3 support to the solution containing the chloroplatinic acid precursor; S10. An alkaline precipitant was added dropwise to a solution containing chloroplatinic acid (H2PtCl6) precursor to carry out the reaction. After the reaction was completed, the solution was washed with deionized water to obtain a catalyst with a platinum loading of 1 wt%. S11. The catalyst is immersed in a solution containing PEG-6000 surfactant, the surfactant mass percentage concentration in the solution is 3%, and the mass ratio of catalyst to surfactant solution is 1:1. S12. The catalyst is stirred at room temperature for 2 hours, then filtered, and dried at 70°C for 9 hours to obtain the surface-modified catalyst. S13. Under a nitrogen atmosphere, the modified catalyst is heated to 250°C at a rate of 3°C / min and held at that temperature for 1.5 hours. S14. Then, under a hydrogen atmosphere, the modified catalyst is heated to 350°C at the same heating rate and held at that temperature for 3 hours. S15. Finally, under a nitrogen atmosphere, the temperature is lowered to room temperature to obtain the tritium oxidation catalyst.

[0031] Example 2 The difference between this embodiment and Embodiment 1 is that the lanthanum loading in the γ-Al2O3 support powder obtained in step S6 is 1 wt%, while the rest is the same as in Embodiment 1.

[0032] Example 3 The difference between this embodiment and Embodiment 1 is that the lanthanum loading in the γ-Al2O3 support powder obtained in step S6 is 10 wt%, while the rest is the same as in Embodiment 1.

[0033] Example 4 The difference between this embodiment and Embodiment 1 is that the lanthanum loading in the γ-Al2O3 support powder obtained in step S6 is 3wt%, while the rest is the same as in Embodiment 1.

[0034] Example 5 The difference between this embodiment and Embodiment 1 is that in step S4, a cerium nitrate solution is used, and in step S6, the cerium loading in the γ-Al2O3 support powder is 6 wt%, while the rest is the same as in Embodiment 1.

[0035] Example 6 The difference between this embodiment and Embodiment 1 is that step S4 uses a cerium nitrate solution, and the cerium loading in the γ-Al2O3 carrier powder obtained in step S6 is 1 wt%, while the rest is the same as in Embodiment 1.

[0036] Example 7 The difference between this embodiment and Embodiment 1 is that step S4 uses a cerium nitrate solution, and the cerium loading in the γ-Al2O3 carrier powder obtained in step S6 is 3 wt%, while the rest is the same as in Embodiment 1.

[0037] Example 8 The difference between this embodiment and Embodiment 1 is that in step S4, a cerium nitrate solution is used, and in step S6, the cerium loading in the γ-Al2O3 carrier powder is 10 wt%, while the rest is the same as in Embodiment 1.

[0038] Example 9 The difference between this embodiment and Example 1 is that in step S10, palladium chloride precursor is used, and the palladium loading in the obtained catalyst is 1 wt%, while the rest is the same as in Example 1.

[0039] Example 10 The difference between this embodiment and Example 1 is that the lanthanum loading in the γ-Al2O3 support powder obtained in step S6 is 1 wt%, the palladium chloride precursor in step S10 is used, and the palladium loading in the obtained catalyst is 1 wt%. The rest is the same as in Example 1.

[0040] Example 11 The difference between this embodiment and Example 1 is that the lanthanum loading in the γ-Al2O3 support powder obtained in step S6 is 3 wt%, the palladium chloride precursor in step S10 is 1 wt%, and the palladium loading in the obtained catalyst is 1 wt%. The rest is the same as in Example 1.

[0041] Example 12 The difference between this embodiment and Example 1 is that the lanthanum loading in the γ-Al2O3 support powder obtained in step S6 is 10 wt%, the palladium chloride precursor in step S10 is 1 wt%, and the palladium loading in the obtained catalyst is 1 wt%. The rest is the same as in Example 1.

[0042] Example 13 The difference between this embodiment and Example 1 is that step S4 uses a cerium nitrate solution, the γ-Al2O3 support powder obtained in step S6 has a cerium loading of 6 wt%, and the catalyst obtained in step S10 uses a palladium chloride precursor with a palladium loading of 1 wt%. The rest is the same as in Example 1.

[0043] Example 14 The difference between this embodiment and Example 1 is that step S4 uses a cerium nitrate solution, the γ-Al2O3 support powder obtained in step S6 has a cerium loading of 1 wt%, and the catalyst obtained in step S10 uses a palladium chloride precursor with a palladium loading of 1 wt%. The rest is the same as in Example 1.

[0044] Example 15 The difference between this embodiment and Example 1 is that step S4 uses a cerium nitrate solution, the γ-Al2O3 support powder obtained in step S6 has a cerium loading of 3 wt%, and the catalyst obtained in step S10 uses a palladium chloride precursor with a palladium loading of 1 wt%. The rest is the same as in Example 1.

[0045] Example 16 The difference between this embodiment and Example 1 is that step S4 uses a cerium nitrate solution, the γ-Al2O3 support powder obtained in step S6 has a cerium loading of 10 wt%, and the catalyst obtained in step S10 uses a palladium chloride precursor with a palladium loading of 1 wt%. The rest is the same as in Example 1.

[0046] Example 17 The difference between this embodiment and Embodiment 1 is that the platinum loading in step S10 is 0.1 wt%, while the rest is the same as in Embodiment 1.

[0047] Example 18 The difference between this embodiment and Embodiment 1 is that the platinum loading in step S10 is 2wt%, while the rest is the same as in Embodiment 1.

[0048] Example 19 The difference between this embodiment and Embodiment 1 is that the calcination temperature in step S7 is 500℃, while the rest is the same as in Embodiment 1.

[0049] Example 20 The difference between this embodiment and Embodiment 1 is that the roasting temperature in step S7 is 700℃, while the rest is the same as in Embodiment 1.

[0050] Example 21 The difference between this embodiment and Embodiment 1 is that the surfactant used in step S11 is P123, while the rest is the same as in Embodiment 1.

[0051] Comparative Example 1 The difference between this comparative example and Example 1 is that in step S13, the modified catalyst is heated to 350°C at 3°C / min under a nitrogen atmosphere and held at that temperature for 4.5 hours; step S14 is not included, and the rest is the same as in Example 1.

[0052] Comparative Example 2 The difference between this comparative example and Comparative Example 1 is that in step S13, the modified catalyst is heated to 350°C at a rate of 3°C / min under a hydrogen atmosphere and held at that temperature for 4.5 hours; the rest is the same as in Example 23.

[0053] Comparative Example 3 The difference between this comparative example and Example 1 is that the lanthanum loading in the γ-Al2O3 support powder obtained in step S6 is 0.5 wt%, and the platinum loading in step S10 is 3 wt%, with the rest being the same as in Example 1.

[0054] Comparative Example 4 The difference between this comparative example and Example 1 is that the lanthanum loading in the γ-Al2O3 support powder obtained in step S6 is 15 wt%, and the platinum loading in step S10 is 0.1 wt%, with the rest being the same as in Example 1.

[0055] Comparative Example 5 The difference between this comparative example and Example 1 is that the calcination temperature in step S7 is 800°C, while the rest is the same as in Example 1.

[0056] Comparative Example 6 The difference between this comparative example and Example 1 is that the calcination temperature in step S7 is 400°C, while the rest is the same as in Example 1.

[0057] Comparative Example 7 The difference between this comparative example and Example 1 is that step S10 does not include the step of adding an alkaline precipitant to the solution containing the chloroplatinic acid (H2PtCl6) precursor for reaction; the rest is the same as in Example 1.

[0058] Comparative Example 8 The difference between this comparative example and Example 1 is that in step S4-10, the pretreated γ-Al2O3 support, lanthanum nitrate solution and solution containing chloroplatinic acid (H2PtCl6) precursor are mixed, stirred evenly, and then dried and calcined to obtain the catalyst. The rest is the same as in Example 1.

[0059] The performance of the tritium oxidation catalysts prepared in Examples 1-22 and Comparative Examples 1-8 was determined experimentally below. The specific testing method is as follows: The catalyst was packed into a plug flow reactor, and the center of the reactor was heated to a constant 100°C, with a tritium concentration of 2.0 × 10⁻⁶. 6 Bq / m 3 Relative humidity 80%, volume hourly space velocity 15000 h⁻¹ -1 Under the conditions, the tritium conversion rate was tested, which is (inlet tritium concentration - outlet tritium concentration) ÷ inlet tritium concentration × 100%. The tritium conversion rate was recorded when the reactor temperature just reached 100℃ and after continuous operation for 1000 hours.

[0060] Method for testing the dispersion of precious metals: The catalyst is ground and sieved to obtain a 60-80 mesh powder sample. The dispersion of precious metals is tested using a carbon monoxide pulse adsorption method. Specifically, the sample is pretreated at 500℃ for 2 hours under an inert He atmosphere, then cooled to 40℃ and switched to a CO pulse gas source. Multiple pulses of CO gas with known volumes and concentrations are quantitatively injected, causing CO to chemically adsorb onto the metal active sites on the catalyst surface. A downstream TCD detector records the breakthrough curve of each pulse in real time. The amount of unadsorbed CO gradually stabilizes with the number of pulses, and the cumulative adsorption amount allows calculation of the number of available sites on the metal surface. Combining the metal loading and the stoichiometric ratio of CO to metal surface atoms (e.g., Pt:CO = 1:1, Pd:CO = 1:1), the ratio of the number of surface atoms to the total number of metal atoms can be further calculated, thus obtaining the dispersion of the precious metal.

[0061] The test results are shown in Table 1 below.

[0062] Table 1

[0063] Note 1: The dispersion of precious metals is positively correlated with the activity of the catalyst; the better the dispersion, the higher the reaction activity of the catalyst.

[0064] Note 2, Conversion rate = Conversion amount / (catalyst mass × reaction time).

[0065] 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 rare earth element-containing noble metal tritium oxidation catalyst, characterized in that, Includes the following steps: Preparation of γ-Al2O3 supports containing rare earth elements; A catalyst was obtained by loading noble metals onto the surface of the γ-Al2O3 support using a deposition-precipitation method. The catalyst was surface modified by immersing it in a solution containing a nonionic surfactant. The modified catalyst was calcined to obtain a tritium oxidation catalyst.

2. The preparation method of the rare earth element-containing noble metal tritium oxidation catalyst according to claim 1, characterized in that, The rare earth element loading is 1-10% of the mass of the γ-Al2O3 support.

3. The preparation method of the rare earth element-containing noble metal tritium oxidation catalyst according to claim 1, characterized in that, The step of loading noble metals onto the surface of the γ-Al2O3 support using a deposition-precipitation method to obtain the catalyst includes: Prepare a solution containing a noble metal precursor, wherein the noble metal precursor includes a Pt precursor and / or a Pd precursor; The γ-Al2O3 support was added to the solution; An alkaline precipitant was added dropwise to the solution to initiate a reaction. After the reaction was complete, the solution was washed with deionized water to obtain the catalyst.

4. The preparation method of the rare earth element-containing noble metal tritium oxidation catalyst according to claim 3, characterized in that, The reaction step of adding an alkaline precipitant dropwise to the solution includes: Under stirring conditions, an alkaline precipitant is added dropwise to the solution until the pH of the solution is 8-10; The solution temperature was adjusted to 60-80℃, and the reaction was stirred continuously for 4-8 hours. Then, the solution was cooled to room temperature, filtered, and washed with deionized water until no chloride ions were found. The solution was then cooled to room temperature to obtain the catalyst.

5. The preparation method of the rare earth element-containing noble metal tritium oxidation catalyst according to claim 1, characterized in that, The loading of the precious metal is 0.1-2% of the mass of the catalyst.

6. The method for preparing the rare earth element-containing noble metal tritium oxidation catalyst according to claim 1, characterized in that, The surface modification step of immersing the catalyst in a solution containing a nonionic surfactant includes: The catalyst is immersed in a solution containing a nonionic surfactant, wherein the surfactant has a mass percentage concentration of 1-5% in the solution. The catalyst was stirred at room temperature for 1-3 hours, then filtered and dried at 60-80°C for 6-12 hours to obtain the surface-modified catalyst.

7. The method for preparing the rare earth element-containing noble metal tritium oxidation catalyst according to claim 6, characterized in that, The nonionic surfactant is PEG-6000 or P123.

8. The method for preparing the rare earth element-containing noble metal tritium oxidation catalyst according to claim 1, characterized in that, The step of calcining the modified catalyst to obtain the tritium oxidation catalyst includes: The modified catalyst was heated to 200-300℃ under a nitrogen atmosphere and held at that temperature for 1-2 hours. Then, under a hydrogen atmosphere, the modified catalyst is heated to 300-400°C and held at that temperature for 2-4 hours; Finally, the mixture was cooled to room temperature under a nitrogen atmosphere to obtain the tritium oxidation catalyst.

9. The method for preparing the rare earth element-containing noble metal tritium oxidation catalyst according to claim 1, characterized in that, The steps for preparing the γ-Al2O3 support containing rare earth elements include: The pretreated γ-Al2O3 support was added to a rare earth element nitrate solution and stirred until homogeneous. The nitrate solution was either cerium nitrate or lanthanum nitrate solution. The solution is aged at 60-80°C for 2-4 hours; The solution is then dried to obtain a carrier powder; The carrier powder was calcined at 500-700℃ for 4-6 hours to obtain a γ-Al2O3 carrier containing rare earth elements.

10. The method for preparing the rare earth element-containing noble metal tritium oxidation catalyst according to claim 1, characterized in that, The γ-Al2O3 support is a pretreated γ-Al2O3 support; The preprocessing steps include: The γ-Al2O3 support was calcined at 500-600℃ for 3-5 hours, and then cooled to room temperature. The γ-Al2O3 support was immersed in a 0.1-1 mol / L organic acid solution and stirred at 40-60°C for 2-4 hours. Then, it is washed with deionized water until neutral and dried at 100-120°C for 12 hours to obtain the pretreated γ-Al2O3 support.

11. The application of a tritium oxidation catalyst prepared by any one of the preparation methods according to claims 1-10 in the treatment of tritium-containing waste gas.

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