Use of a bimetallic catalyst in the catalytic decomposition of hydrazine nitrate and hydroxylamine nitrate in nitric acid

Abstract

The application discloses application of a bimetallic catalyst in catalytic decomposition of hydrazinium nitrate and hydroxylamine nitrate in nitric acid, the bimetallic catalyst comprising a carrier and an active component supported on the carrier; the carrier is selected from oxides of titanium and / or oxides of cerium; the active component comprises a first active component and a second active component; the first active component is ruthenium; the second active component is selected from at least one of iridium and rhodium. The catalyst completely catalytically decomposes hydroxylamine nitrate and hydrazinium nitrate in a nitric acid system, and provides a method for removing hydroxylamine nitrate and hydrazinium nitrate under mild conditions. The catalyst raw material is easy to obtain, the process is simple, and the catalyst has a good application prospect.

Description

Technical Field

[0001] This application relates to the application of a bimetallic catalyst in the catalytic decomposition of hydrazine nitrate and hydroxylamine nitrate in nitric acid, belonging to the field of nuclear fuel reprocessing technology. Background Technology

[0002] Nuclear fuel reprocessing technology is a crucial part of the nuclear industry. It involves processing spent nuclear fuel (used fuel) from nuclear reactors to recover uranium, plutonium, and other valuable elements, and vitrifying high-level radioactive waste for deep geological disposal. Currently, reprocessing plants both domestically and internationally primarily employ the Purex process. In this process, hydrazine and / or hydroxylamine are commonly used as stabilizers for low-oxidation-state actinide ions or as nitrite scavengers. Subsequent processes generate nitric acid waste containing hydrazine nitrate and hydroxylamine nitrate. In reprocessing, sodium nitrite or nitrogen tetroxide gas is typically added to decompose hydrazine nitrate and hydroxylamine nitrate. Adding sodium nitrite introduces salts into the system, increasing the waste volume; while introducing N₂O₄ gas does not introduce salts, it generates a large amount of radioactive aerosols, placing a significant burden on the exhaust gas purification system. Catalytic decomposition of hydrazine nitrate and hydroxylamine nitrate offers advantages such as not introducing other ions and requiring smaller waste volume, making it a method worthy of further research in reprocessing.

[0003] Since the late 1990s, scholars both domestically and internationally have published numerous papers on the catalytic decomposition of hydrazine in the post-treatment field. Ananiev et al. investigated the kinetics of Pt / SiO2-catalyzed hydrazine decomposition in nitric acid, non-nitric acid, and weakly basic systems and speculated on its reaction mechanism. They also studied the kinetics and reaction mechanism of Ru / SiO2-catalyzed hydrazine decomposition in nitric acid systems. Ananiev et al. used oxides and oxide composite supports to support Pt for catalytic hydrazine decomposition, finding that the sol-gel effect of the oxide support reduced the catalyst activity in nitric acid systems. Chang Li et al. studied the effects of temperature, acidity, and other conditions in nitric acid on Pt-Ti-catalyzed hydrazine decomposition. Currently, research on the catalytic decomposition of hydrazine mainly focuses on the investigation of kinetics and process conditions, while research on catalyst optimization design is relatively limited. Furthermore, there are few reports on the decomposition of mixed systems of hydrazine and hydroxylamine.

[0004] Chinese patent CN112678939A discloses a method for removing small amounts of hydrazine nitrate and hydroxylamine nitrate from nitric acid. A catalyst with an "activated carbon-metal-silicon oxide" structure is used for the catalytic decomposition of a mixture of hydrazine nitrate and hydroxylamine nitrate, exhibiting advantages such as high activity and long service life. However, during experiments, the reaction temperature needed to be increased to extend the catalyst's lifespan, indicating a gradual decrease in activity during the reaction. Researchers found that the active components of the catalyst were lost in the nitric acid system, and because this reaction is an in-situ, large-volume gas-producing reaction, it caused continuous erosion of the catalyst, resulting in severe catalyst breakage after 2830 hours of use. Simultaneously, the activated carbon-supported catalyst, due to prolonged immersion in the nitric acid solution, gradually decomposed, leading to significant catalyst loss and consequently affecting the catalytic reaction. Summary of the Invention

[0005] The technical problem to be solved by this invention is that the active components of the catalyst for the catalytic decomposition of hydroxylamine nitrate and hydrazine nitrate in the nitric acid system are easily lost in nitric acid solution, break down after long-term use, and suffer from catalyst digestion and loss.

[0006] To address this, a novel catalyst is provided that exhibits high strength, resistance to breakage, and resistance to acid nitric acid corrosion in nitric acid systems, with active components that are not easily lost. This catalyst can efficiently catalyze the decomposition of hydrazine nitrate and hydroxylamine nitrate in nitric acid solutions under mild conditions.

[0007] One aspect of this application provides the use of a bimetallic catalyst in the catalytic decomposition of hydrazine nitrate and hydroxylamine nitrate in nitric acid.

[0008] The bimetallic catalyst includes a support and an active component supported on the support;

[0009] The carrier is selected from oxides of titanium and / or oxides of cerium;

[0010] The active component includes a first active component and a second active component;

[0011] The first active component is ruthenium;

[0012] The second active component is selected from at least one of iridium and rhodium.

[0013] Optionally, in the bimetallic catalyst, the mass percentage of the first active component is 0.5-10%, the mass percentage of the second active component is 0.001-1%, and the remainder is a support, wherein the mass of the first active component and the mass of the second active component are based on the mass of the metal elements in the active components.

[0014] Optionally, the mass percentage of the first active component is independently selected from any value among 0.5%, 0.9%, 2%, 2.7%, 4%, 4.5%, 5.0%, 6%, 7%, 8%, 9%, and 10%, or any range between any two of the above points.

[0015] Optionally, the mass percentage of the second active component is independently selected from any value among 0.001%, 0.01%, 0.1%, 0.3%, 0.5%, 0.8%, and 1%, or any range between any two of the above points.

[0016] Optionally, in the bimetallic catalyst, the mass percentage of the first active component is 0.5-5%, the mass percentage of the second active component is 0.01-0.5%, and the remainder is a support, wherein the mass of the first active component and the mass of the second active component are based on the mass of the metal element in the active component.

[0017] In one specific embodiment, the bimetallic catalyst comprises the following components by mass: 1) oxides of titanium or cerium, the remainder being other components; 2) the first active component being Ru, accounting for 1 to 10%; and 3) the second active component being selected from one or both of Ir and Rh, accounting for 0.001 to 1%.

[0018] Optionally, the preparation method of the bimetallic catalyst includes:

[0019] (1) Add the solution containing the precursor of the first active component to the solution containing the precipitant and the carrier precursor, and after impregnation I, drying I, and calcination I, obtain the carrier loaded with the first active component;

[0020] (2) The support loaded with the first active component obtained in step (1) is mixed with a solution containing the precursor of the second active component, and the mixture is impregnated (II), dried (II), calcined (II), and reduced to obtain the bimetallic catalyst.

[0021] This method utilizes the strong interaction between the metal and the support to modulate the properties of the catalyst, suppress the loss of the active component, and modulate the electronic properties of the catalyst by the second active component, thereby improving the catalyst activity.

[0022] Optionally, the first active component precursor is a ruthenium salt;

[0023] The ruthenium salt is selected from at least one of ruthenium trichloride and ruthenium acetate.

[0024] Optionally, in the solution containing the first active component precursor, the concentration of the first active component precursor is 1% to 10% based on the mass of the first active component.

[0025] Optionally, the carrier precursor is selected from one of soluble titanium salts and soluble cerium salts.

[0026] Optionally, the soluble titanium salt is selected from at least one of titanium tetrachloride and titanium nitrate.

[0027] Optionally, the soluble cerium salt is selected from at least one of cerium nitrate and cerium nitrate.

[0028] Optionally, the precipitant is selected from at least one of urea and ammonium carbonate.

[0029] Optionally, the method for preparing the solution containing the precipitant and the carrier precursor includes:

[0030] A precipitant solution with a concentration of 0.001–10 mol / L is mixed with a carrier precursor solution with a mass concentration of 10%–50%, and stirred at 60–95°C for 0.5–24 h.

[0031] Optionally, the concentration of the precipitant solution is independently selected from any value among 0.001 mol / L, 0.005 mol / L, 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.5 mol / L, 1 mol / L, 2 mol / L, 5 mol / L, 8 mol / L, and 10 mol / L, or any range between any two of the above values.

[0032] Optionally, the concentration of the carrier precursor solution is independently selected from any value of 10%, 20%, 30%, 40%, 50%, or any range between any two of the above.

[0033] Optionally, the stirring temperature is independently selected from any value among 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, and 95℃, or any range between any two of the above points.

[0034] Optionally, the stirring time is independently selected from any value among 0.5h, 5h, 10h, 15h, and 24h, or any range between any two of the above points.

[0035] Optionally, the mass ratio of the precipitant solution to the carrier precursor solution is 0.2:1 to 1.2:1.

[0036] Optionally, the mass ratio of the precipitant solution to the carrier precursor solution is independently selected from any value among 0.2:1, 0.4:1, 0.6:1, 0.8:1, 1:1, 1.2:1 or any range between any two of the above points.

[0037] Optionally, the mass ratio of the solution containing the first active component precursor to the carrier precursor solution is 0.005:1 to 1:1.

[0038] Optionally, the mass ratio of the solution containing the first active component precursor to the carrier precursor solution is independently selected from any value among 0.005:1, 0.01:1, 0.05:1, 0.1:1, 0.2:1, 0.4:1, 0.6:1, 0.8:1, 1:1 or any range between any two of the above points.

[0039] Optionally, the impregnation time for I is 5 to 24 hours;

[0040] Optionally, the immersion time I is independently selected from any value among 5h, 10h, 12h, 15h, 20h, and 24h, or any range between any two of the above points.

[0041] Optionally, the temperature of drying I is 60-120°C, the drying time is 12-48 hours, and the atmosphere of drying I is air.

[0042] Optionally, the temperature of the drying I is independently selected from any value among 60°C, 80°C, 100°C, and 120°C, or any range between any two of the above.

[0043] Optionally, the drying time I is independently selected from any value among 12h, 24h, 36h, and 48h, or any range between any two of the above.

[0044] Optionally, the temperature of calcination I is 300-600°C, the calcination time is 1-8 hours, and the atmosphere of calcination I is air.

[0045] Optionally, the temperature of the roasting I is independently selected from any value among 300℃, 350℃, 400℃, 450℃, 500℃, 550℃, and 600℃, or any range between any two of the above points.

[0046] Optionally, the roasting time I is independently selected from any value among 1h, 2h, 4h, 6h, and 8h, or any range between any two of the above points.

[0047] Optionally, the second active component precursor is selected from at least one of iridium salt and rhodium salt.

[0048] Optionally, the iridium salt is selected from at least one of chloroiridic acid and iridium trichloride.

[0049] Optionally, the rhodium salt is selected from at least one of rhodium chloride, rhodium nitrate, and rhodium acetate.

[0050] Optionally, in the solution containing the second active component precursor, the concentration of the second active component precursor is 1% to 10% based on the mass of the second active component.

[0051] Optionally, the concentration of the second active component precursor is independently selected from any value of 1%, 2%, 4%, 6%, 8%, 10%, or any range between any two of the above.

[0052] Optionally, the volume ratio of the solution containing the second active component precursor to the carrier loaded with the first active component is 0.1 to 10.

[0053] Optionally, the volume ratio of the solution containing the second active component precursor to the carrier loaded with the first active component is independently selected from any value among 0.1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or any range between any two of the above points.

[0054] Optionally, the impregnation time II is 1 to 24 hours;

[0055] Optionally, the immersion time II is independently selected from any value among 1h, 4h, 8h, 12h, 16h, 20h, and 24h, or any range between any two of the above points.

[0056] Optionally, the temperature of the second drying step is 60–120°C, and the drying time is 1–24 hours.

[0057] Optionally, the temperature of the drying II is independently selected from any value among 60°C, 80°C, 100°C, and 120°C, or any range between any two of the above.

[0058] Optionally, the drying time II is independently selected from any value among 1h, 2h, 6h, 10h, 12h, 16h, 20h, and 24h, or any range between any two of the above points.

[0059] Optionally, the temperature of the second calcination is 200-500°C, the calcination time is 2-6 hours, and the atmosphere of the second calcination is air.

[0060] Optionally, the temperature of the roasting II is independently selected from any value among 200°C, 300°C, 400°C, and 500°C, or any range between any two of the above.

[0061] Optionally, the roasting time II is independently selected from any value among 2h, 4h, and 6h, or any range between any two of the above.

[0062] Optionally, the reduction is carried out under a hydrogen atmosphere;

[0063] The reduction temperature is 200–500℃, and the reduction time is 1–8 hours.

[0064] Optionally, the reduction temperature is independently selected from any value among 200℃, 250℃, 300℃, 350℃, 400℃, 450℃, and 500℃, or any range between any two of the above points.

[0065] Optionally, the restoration time is independently selected from any value among 1h, 2h, 4h, 6h, and 8h, or any range between any two of the above points.

[0066] As one specific implementation method, the preparation method includes:

[0067] a) Preparation of oxide supports containing Ru precursors

[0068] 1) Dissolve a certain amount of soluble titanium or cerium salt in concentrated hydrochloric acid or deionized water to prepare a solution for later use;

[0069] 2) Add an aqueous solution of urea or ammonium carbonate with a concentration of 0.001–10 mol / L to the solution in step 1), and stir in a water bath at 60–95°C for 0.5–24 h;

[0070] 3) Add the ruthenium precursor solution dropwise to step 2) and stir and soak for 5-24 hours.

[0071] 4) Filter and wash the solution from step 3) until neutral, and dry the obtained solid in air at 60–120°C for 12–48 h;

[0072] 5) The dried solid was calcined in air at 300-600℃ for 1-8 hours to obtain an oxide support containing Ru precursor;

[0073] b) Loading of the second active component

[0074] 1) Take an oxide support containing Ru precursor, add or pour a salt solution of noble metal iridium or rhodium onto the oxide support containing Ru precursor, with a volume ratio of solution to oxide support containing Ru precursor of 0.1 to 10, and mix them evenly.

[0075] 2) Soak the mixture from step 1) at room temperature for 1–24 h, then dry it at 60–120 °C for 6–24 h;

[0076] 3) Calcining the solid from step 2) at 200–500°C in air for 2–6 hours;

[0077] 4) Reduce the solid from step 3) at 200–500 °C for 3–8 h under hydrogen atmosphere.

[0078] Optionally, the method for catalytically decomposing hydrazine nitrate and hydroxylamine nitrate in nitric acid includes: contacting a solution of nitric acid to be treated containing hydrazine nitrate and hydroxylamine nitrate with the bimetallic catalyst to react and catalytically decompose hydrazine nitrate and hydroxylamine nitrate.

[0079] The catalyst simultaneously catalyzes the decomposition of hydrazine nitrate and hydroxylamine nitrate under nitric acid conditions. This catalyst can achieve the catalytic decomposition of hydrazine nitrate and hydroxylamine nitrate in a nitric acid system in a reactor or fixed bed.

[0080] Optionally, in the nitric acid solution to be treated, the concentration of nitric acid is 0.8–1.5 mol / L, the concentration of hydrazine nitrate is 0.05–0.2 mol / L, and the concentration of hydroxylamine nitrate is 0.2–0.5 mol / L.

[0081] The nitric acid solution to be treated is mixed with a 1% (v / v) tributyl phosphate / n-dodecane solution and allowed to stand to separate into layers. The lower layer is used for catalytic decomposition reaction.

[0082] Optionally, the concentration of the nitric acid is independently selected from any value among 0.8 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L, or any range between any two of the above values.

[0083] Optionally, the concentration of hydrazine nitrate is independently selected from any value among 0.05 mol / L, 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, or any range between any two of the above values.

[0084] Optionally, the concentration of hydroxylamine nitrate is independently selected from any value among 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, or any range between any two of the above values.

[0085] Optionally, the reaction is carried out in a reaction vessel or in a fixed bed;

[0086] Optionally, when the reaction is carried out in the reactor, the reaction temperature is 60-80°C, and the mass ratio of the catalyst to the volume of the nitric acid solution to be treated is 1:10-1:20 g / ml.

[0087] When the reaction is carried out in a fixed-bed reactor, the reaction temperature is 50–70°C, and the space velocity of the nitric acid solution to be treated is 2–12 h⁻¹. -1 .

[0088] Optionally, when the reaction is carried out in the reactor, the temperature of the reaction is independently selected from any value among 60°C, 70°C, and 80°C, or any range between any two of the above.

[0089] Optionally, when the reaction is carried out in the reactor, the mass ratio of the catalyst to the volume ratio of the nitric acid solution to be treated is independently selected from any value among 1:10 g / ml, 1:15 g / ml, 1:20 g / ml, or any range between any two of the above.

[0090] Optionally, when reacting in a fixed-bed reactor, the reaction temperature is independently selected from any value among 50°C, 60°C, and 70°C, or any range between any two of the above.

[0091] Optionally, when reacting in a fixed-bed reactor, the space velocity of the nitric acid solution to be treated is independently selected from 2 h⁻¹. -1 4h -1 6h -1 8h -1 10h -1 12h -1 Any value in or any range between any two of the above points.

[0092] The beneficial effects that this application can produce include:

[0093] 1) Compared with the prior art, the catalyst of the present invention has high activity, effectively suppresses the loss of active components of the catalyst in the nitric acid system, and further improves the stability of the catalyst.

[0094] 2) The catalyst of the present invention is resistant to acid corrosion and wear in nitric acid system and in-situ gas generation reaction. The catalyst did not break after 2000 hours of continuous operation and the catalyst structure did not change. This solves the problem of particle breakage and catalyst structure collapse during long-term operation of the catalyst in the prior art.

[0095] 3) This catalyst completely catalyzes the decomposition of hydroxylamine nitrate and hydrazine nitrate in a nitric acid system, providing a method for removing hydroxylamine nitrate and hydrazine nitrate under mild conditions. The catalyst of this invention uses readily available raw materials, has a simple process, and shows great promise for application. Attached Figure Description

[0096] Figure 1 The results of the residual concentration detection of hydroxylamine nitrate in the fixed-bed stability experiment of Test Example 2 of this application;

[0097] Figure 2 The results of the residual concentration detection of hydrazine nitrate in the fixed-bed stability experiment in Test Example 2 of this application are shown. Detailed Implementation

[0098] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0099] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0100] Example 1

[0101] 35.0 g of TiCl4 solution was slowly added dropwise to 50 ml of 10% hydrochloric acid solution and stirred until homogeneous. 100.0 g of 50% ammonium carbonate aqueous solution was added to the above solution, mixed thoroughly, and then stirred in a 95°C water bath for 24 h. Subsequently, 13.25 g of 5% ruthenium trichloride solution was added to the solution, and stirring continued at room temperature for 10 h. The resulting turbid liquid was filtered and washed until neutral, and the filter cake was dried in air at 80°C for 12 h. The dried solid was calcined in air at 450°C for 6 h to obtain a Ru-containing TiO2 support.

[0102] Take 4.975g of the above-mentioned Ru-containing TiO2 support and place it in a 50mL beaker for later use. Weigh 0.025g of chloroiridium acid solution with a mass concentration of 10% iridium, add water to 1.75g, mix well, pour into the 50mL beaker containing the Ru-containing TiO2 support, stir evenly, impregnate at room temperature for 1h, dry at 120℃ for 2h, calcine in air at 300℃ for 4h, and then reduce at 350℃ in a hydrogen atmosphere for 2h to obtain the Ru-Ir bimetallic catalyst, wherein the mass content of Ru is 4.5% and the mass content of Ir is 0.5%, denoted as 4.5Ru-0.5Ir / TiO2.

[0103] Example 2

[0104] 35.0 g of TiCl4 solution was slowly added dropwise to 50 ml of 10% hydrochloric acid solution and stirred until homogeneous. 100.0 g of 50% urea aqueous solution was added to the above solution, mixed thoroughly, and then stirred in a 95°C water bath for 24 h. Subsequently, 7.95 g of ruthenium trichloride solution containing 5% ruthenium was added to the solution, and stirring was continued at room temperature for 10 h. The resulting turbid liquid was filtered and washed until neutral, and the filter cake was dried in air at 80°C for 24 h. The dried solid was calcined in air at 500°C for 4 h to obtain the Ru-containing TiO2 support.

[0105] Take 4.985g of the above-mentioned Ru-containing TiO2 support and place it in a 50mL beaker for later use. Weigh 0.015g of chloroiridium acid solution with a mass concentration of 10% iridium, add water to 1.75g, mix well, pour into the 50mL beaker containing the Ru-containing TiO2 support, stir evenly, impregnate at room temperature for 1h, dry at 120℃ for 2h, calcine in air at 300℃ for 4h, and then reduce at 350℃ in a hydrogen atmosphere for 2h to obtain the Ru-Ir bimetallic catalyst, wherein the mass content of Ru is 2.7% and the mass content of Ir is 0.3%, denoted as 2.7Ru-0.3Ir / TiO2.

[0106] Example 3

[0107] 35.0 g of TiCl4 solution was slowly added dropwise to 50 ml of 10% hydrochloric acid solution and stirred until homogeneous. 100.0 g of 50% ammonium carbonate aqueous solution was added to the above solution, mixed thoroughly, and then stirred in a 95°C water bath for 24 h. Subsequently, 2.94 g of ruthenium acetate solution containing 5% ruthenium was added to the solution, and stirring was continued at room temperature for 10 h. The resulting turbid liquid was filtered and washed until neutral, and the filter cake was dried in air at 80°C for 24 h. The dried solid was calcined in air at 500°C for 4 h to obtain the Ru-containing TiO2 support.

[0108] Take 4.995g of the above-mentioned Ru-containing TiO2 support and place it in a 50mL beaker for later use. Weigh 0.005g of chloroiridium acid solution containing 10% iridium by mass, add water to 1.75g, mix well, pour into the 50mL beaker containing the Ru-containing TiO2 support, stir evenly, impregnate at room temperature for 1h, dry at 120℃ for 2h, calcine in air at 300℃ for 4h, and then reduce at 350℃ in a hydrogen atmosphere for 2h to obtain the Ru-Ir bimetallic catalyst, wherein the mass content of Ru is 0.9% and the mass content of Ir is 0.1%, denoted as 0.9Ru-0.1Ir / TiO2.

[0109] Example 4

[0110] Take 4.975g of the Ru-containing TiO2 support from Example 1 and place it in a 50mL beaker for later use. Weigh 0.025g of a 10% rhodium chloride solution, add water to 1.75g, mix well, pour into the 50mL beaker containing the Ru-containing TiO2 support, stir evenly, impregnate at room temperature for 1h, dry at 120℃ for 2h, calcine in air at 300℃ for 4h, and then reduce at 350℃ in a hydrogen atmosphere for 2h to obtain the Ru-Rh bimetallic catalyst, wherein the mass content of Ru is 4.5% and the mass content of Rh is 0.5%, denoted as 4.5Ru-0.5Rh / TiO2.

[0111] Example 5

[0112] Dissolve 21.7 g of Ce(NO3)3·6H2O in 100 ml of deionized water and stir well. Add 50 g of a 50% (w / w) urea aqueous solution to the above solution, mix well, and then stir in an 80°C water bath for 15 h. Then add 8.2 g of a 5% (w / w) ruthenium trichloride solution to the solution and continue stirring at room temperature for 12 h. Filter and wash the resulting turbid liquid until neutral, then dry the filter cake in air at 100°C for 12 h. Calcine the dried solid in air at 400°C for 6 h to obtain a Ru-containing CeO2 support.

[0113] Take 4.975g of the above-mentioned Ru-containing CeO2 support and place it in a 50mL beaker for later use. Weigh 0.025g of chloroiridium acid solution containing 10% iridium by mass, add water to 1.50g, mix well, pour into the 50mL beaker containing the Ru-containing CeO2 support, stir evenly, impregnate at room temperature for 1h, dry at 120℃ for 2h, calcine in air at 300℃ for 4h, and then reduce at 350℃ in a hydrogen atmosphere for 2h to obtain the Ru-Ir bimetallic catalyst, wherein the mass content of Ru is 4.5% and the mass content of Ir is 0.5%, denoted as 4.5Ru-0.5Ir / CeO2.

[0114] Example 6

[0115] Take 4.975g of the Ru-containing CeO2 support from Example 5 and place it in a 50mL beaker for later use. Weigh 0.025g of a 10% rhodium chloride solution, add water to 1.50g, mix well, pour into the 50mL beaker containing the Ru-containing CeO2 support, stir evenly, impregnate at room temperature for 1h, dry at 120℃ for 2h, calcine at 300℃ in air for 4h, and then reduce at 350℃ in a hydrogen atmosphere for 2h to obtain the Ru-Rh bimetallic catalyst, wherein the mass content of Ru is 4.5% and the mass content of Rh is 0.5%, denoted as 4.5Ru-0.5Rh / CeO2.

[0116] Comparative Example 1

[0117] 35.0 g of TiCl4 solution was slowly added dropwise to 50 ml of 10% hydrochloric acid solution and stirred until homogeneous. 100.0 g of 50% ammonium carbonate aqueous solution was added to the above solution and mixed thoroughly. The mixture was then placed in a 95°C water bath and stirred for 24 h. Subsequently, 14.72 g of ruthenium trichloride solution containing 5% ruthenium was added to the solution, and stirring was continued at room temperature for 10 h. The resulting turbid liquid was filtered and washed until neutral. The filter cake was then dried in air at 80°C for 12 h. The dried solid was calcined in air at 450°C for 6 h, and then reduced in hydrogen atmosphere at 350°C for 2 h to obtain a Ru metal catalyst with a Ru content of 5.0%, denoted as 5.0Ru / TiO2.

[0118] Comparative Example 2

[0119] Dissolve 21.7 g of Ce(NO3)3·6H2O in 100 ml of deionized water and stir well. Add 50 g of a 50% urea aqueous solution to the above solution, mix well, and then stir in an 80°C water bath for 15 h. Then add 9.11 g of a 5% ruthenium trichloride solution to the solution and continue stirring at room temperature for 12 h. Filter and wash the resulting turbid liquid until neutral, then dry the filter cake in air at 100°C for 12 h. Calcine the dried solid in air at 400°C for 6 h, and then reduce it in hydrogen atmosphere at 350°C for 2 h to obtain a Ru metal catalyst with a Ru content of 5.0%, denoted as 5.0Ru / CeO2.

[0120] Comparative Example 3

[0121] A ruthenium-carbon catalyst with a Ru mass concentration of 5% was prepared according to the catalyst preparation method described in Example 3 of Chinese Patent CN112678939A, denoted as 5.0Ru / AC.

[0122] Test Example 1

[0123] The catalyst activity was initially evaluated using a batch reactor. 100 mL of a feed solution consisting of 0.3 mol / L hydroxylamine nitrate, 0.1 mol / L hydrazine nitrate, and 1.0 mol / L nitric acid solution (this feed solution was mixed with a 1% (v / v) tributyl phosphate / n-dodecane solution before use, allowed to stand and separate into layers; the lower layer was used for the catalytic decomposition reaction) was poured into a 250 mL three-necked flask. The flask was placed in a thermostatically heated magnetically stirred water bath, set to the required reaction temperature. Once the temperature was reached, 5.0 g of dry catalyst was added to the flask. The stirring speed was 400 rpm, and the reaction was timed. The reaction was stopped when no more bubbles were generated in the reaction system. The reaction time was recorded, and samples were taken for analysis of the residual concentrations of hydroxylamine nitrate and hydrazine nitrate.

[0124] Table 1. Experimental results of catalytic decomposition of hydroxylamine nitrate and hydrazine nitrate using different catalysts at the same temperature.

[0125]

[0126] The catalyst 4.5Ru-0.5Ir / TiO2 was recycled 230 times at 80℃, with each reaction time ranging from 18 to 22 minutes. No hydrazine nitrate or hydroxylamine nitrate was detected in the solution after the reaction, indicating that the catalyst maintained high stability.

[0127] Test Example 2

[0128] The stability and wear resistance of the 4.5Ru-0.5Ir / TiO2 catalyst were evaluated using a fixed-bed reaction mode. 7.5 g (dry weight) of catalyst was loaded into a stainless steel reactor. The outer wall of the reactor was gently tapped to ensure a compacted catalyst layer. The reaction temperature was 60℃, and the feed solution was introduced at a flow rate of 0.5 mL / min. The feed solution consisted of an aqueous solution of 1.0 mol / L nitric acid, 0.1 mol / L hydrazine nitrate, and 0.3 mol / L hydroxylamine nitrate. Before use, this feed solution was mixed with a 1% (v / v) tributyl phosphate / n-dodecane solution and allowed to stand for separation. The lower layer was used for the catalytic decomposition reaction. During operation, samples were taken daily to detect the content of hydroxylamine nitrate and hydrazine nitrate in the effluent. The results are shown below. Figure 1 , Figure 2 The monitoring results of ruthenium content in the reaction solution are shown in Table 2.

[0129] from Figure 1 and Figure 2 The results show that by maintaining a constant reaction temperature of 60℃, the catalyst retains high activity even after 2000 hours of use. Table 2 indicates that the loss of the active component Ru in the catalyst was minimal in the initial stage of the reaction. Upon disassembling the reactor and observing the catalyst state, no catalyst bed collapse or catalyst breakage was observed.

[0130] Table 2. Content of active component Ru in the reaction solution

[0131] 2h 0.3ppm 10h 0.25ppm 20h 0.27ppm 50h 0.3ppm 100h 0.34ppm 200h 0.23ppm 300h 0.15ppm

[0132] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. The application of a bimetallic catalyst in the catalytic decomposition of hydrazine nitrate and hydroxylamine nitrate in nitric acid, characterized in that, The bimetallic catalyst includes a support and an active component supported on the support; The carrier is selected from oxides of titanium and / or oxides of cerium; The active component includes a first active component and a second active component; The first active component is ruthenium; The second active component is selected from at least one of iridium and rhodium; The preparation method of the bimetallic catalyst includes: (1) Add the solution containing the precursor of the first active component to the solution containing the precipitant and the carrier precursor, and then impregnate I, dry I, and calcine I to obtain the carrier loaded with the first active component; (2) The support loaded with the first active component obtained in step (1) is mixed with a solution containing the precursor of the second active component, and the mixture is impregnated (II), dried (II), calcined (II), and reduced to obtain the bimetallic catalyst.

2. The application according to claim 1, characterized in that, In the bimetallic catalyst, the mass percentage of the first active component is 0.5-10%, the mass percentage of the second active component is 0.001-1%, and the remainder is a support. The mass of the first active component and the mass of the second active component are based on the mass of the metal elements in the active components.

3. The application according to claim 1, characterized in that, In the bimetallic catalyst, the mass percentage of the first active component is 0.5-5%, the mass percentage of the second active component is 0.01-0.5%, and the remainder is a support. The mass of the first active component and the mass of the second active component are based on the mass of the metal elements in the active components.

4. The application according to claim 1, characterized in that, The first active component precursor is a ruthenium salt; The ruthenium salt is selected from at least one of ruthenium trichloride and ruthenium acetate; In the solution containing the precursor of the first active component, the concentration of the first active component is 1% to 10%, based on the mass of the first active component; The carrier precursor is selected from one of soluble titanium salts and soluble cerium salts; The soluble titanium salt is selected from at least one of titanium tetrachloride and titanium nitrate; The soluble cerium salt is selected from at least one of cerium nitrate and cerium nitrate; The precipitant is selected from at least one of urea and ammonium carbonate.

5. The application according to claim 1, characterized in that, The method for preparing the solution containing the precipitant and the carrier precursor includes: A precipitant solution with a concentration of 0.001~10 mol / L was mixed with a carrier precursor solution with a mass concentration of 10%~50%, and stirred at 60~95 ​​°C for 0.5~24 h. The mass ratio of the precipitant solution to the carrier precursor solution is 0.2:1 to 1.2:1; The mass ratio of the solution containing the first active component precursor to the carrier precursor solution is 0.005:1 to 1:1; The immersion time for I is 5-24 hours; The temperature of drying I is 60~120℃, the drying time is 12~48 h, and the atmosphere of drying I is air. The temperature of calcination I is 300~600 ℃, the calcination time is 1~8 h, and the atmosphere of calcination I is air.

6. The application according to claim 1, characterized in that, The second active component precursor is selected from at least one of iridium salt and rhodium salt; The iridium salt is selected from at least one of chloroiridium acid and iridium trichloride; The rhodium salt is selected from at least one of rhodium chloride, rhodium nitrate, and rhodium acetate; In the solution containing the precursor of the second active component, the concentration of the precursor of the second active component is 1% to 10%, based on the mass of the second active component. The volume ratio of the solution containing the precursor of the second active component to the carrier loaded with the first active component is 0.1 to 10.

7. The application according to claim 1, characterized in that, The immersion time for the second stage is 1 to 24 hours; The temperature of drying II is 60~120℃, and the drying time of drying II is 1~24h; The temperature of calcination II is 200~500℃, the calcination time is 2~6h, and the atmosphere of calcination II is air. The reduction was carried out under a hydrogen atmosphere; The reduction temperature is 200~500℃, and the reduction time is 1~8h.

8. The application according to claim 1, characterized in that, The method for catalytically decomposing hydrazine nitrate and hydroxylamine nitrate in nitric acid includes: contacting a solution of nitric acid to be treated containing hydrazine nitrate and hydroxylamine nitrate with the bimetallic catalyst, reacting, and catalytically decomposing hydrazine nitrate and hydroxylamine nitrate.

9. The application according to claim 8, characterized in that, In the nitric acid solution to be treated, the concentration of nitric acid is 0.8~1.5 mol / L, the concentration of hydrazine nitrate is 0.05~0.2 mol / L, and the concentration of hydroxylamine nitrate is 0.2~0.5 mol / L.

10. The application according to claim 8, characterized in that, The reaction is carried out in a reaction vessel or in a fixed bed; When the reaction is carried out in the reactor, the reaction temperature is 60~80℃, and the mass ratio of the catalyst to the volume of the nitric acid solution to be treated is 1:10~1:20 g / ml; When the reaction is carried out in a fixed-bed reactor, the reaction temperature is 50-70°C, and the space velocity of the nitric acid solution to be treated is 2-12 h⁻¹. -1 .

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