A process for the preparation of a catalyst for the hydrogenation of uranyl nitrate and its use

Abstract

The present application relates to a kind of preparation method and application for uranyl nitrate hydrogenation catalyst, it is characterized in that, the catalyst is made of carrier silica and active component tungsten carbide two parts, wherein, the mass percentage content of active component in catalyst is 10-25%.The catalyst of the present application has good corrosion resistance and higher uranyl nitrate hydrogenation catalytic decomposition activity.Using hydrogen as reducing agent, the catalyst can reduce uranyl (VI) nitrate to generate uranyl (IV) nitrate at room temperature, and the conversion rate is as high as 99% or more.The catalyst can reduce UO2 2+ In waste water to recyclable U 4+ , both can reduce the pollution of waste water containing uranium, and can improve the use of uranium recovery.

Description

Invention Field

[0001] This invention relates to a method for preparing and applying a hydrogenation catalyst for uranyl nitrate. In this invention, hydrogen is used as a reducing agent, and the catalyst enables uranyl nitrate (VI) to undergo a hydrogenation reduction reaction at room temperature to produce uranyl (IV) nitrate, with a conversion rate exceeding 99%. This catalyst can also remove UO2 from wastewater. 2+ Restored to recyclable U 4+ This can both reduce uranium-containing wastewater pollution and improve the recycling and utilization of uranium.

[0002] Nuclear energy is the world's third major energy source after fossil fuels such as coal, oil, and natural gas, and is expected to become my country's main energy source in the future. While nuclear energy has developed rapidly due to its advantages such as readily available energy storage, high energy density, minimal space constraints, and no air pollution, the large amount of spent fuel accumulated has become a significant problem. The PUREX process is currently the mainstream technology for spent fuel reprocessing. In this process, uranium and plutonium are co-extracted by tributyl phosphate, while fission products remain in the aqueous phase. Furthermore, the co-decontamination and separation of uranium and plutonium is achieved by selectively reducing Pu(Ⅳ) to the less extractable Pu(III) using the reducing agent uranyl nitrate(Ⅳ). Therefore, the reduction of U(Ⅵ) to prepare U(Ⅳ) as a reducing agent for Pu(Ⅳ) is particularly important in spent fuel reprocessing. Currently, methods for preparing uranyl nitrate(Ⅳ) from uranyl nitrate(Ⅵ) include electrolysis, photocatalysis, and heterogeneous catalysis. Electrolytic reduction of uranyl nitrate in the presence of hydrazine nitrate is a common method for preparing uranyl nitrate, but this method suffers from low conversion rates (50%–60%). Heterogeneous catalytic methods, on the other hand, have lower requirements for conditions, simpler equipment, and are easier to industrialize. The French Nuclear Fuel Corporation used a Pt / SiO2 catalyst and hydrogen as a reducing agent at a hydrogen pressure of 4 MPa to catalytically reduce uranyl nitrate to uranyl nitrate, achieving a conversion rate of 96%. Deptuia et al. in Italy used Pt / Al2O3 as a catalyst and formic acid as a reducing agent to catalytically reduce uranyl nitrate to uranyl nitrate, achieving a conversion rate of 100% after 40 minutes, and the catalyst maintained high activity even after 10 reuses. The Dalian Institute of Chemical Physics used Pt / SiO2 as a catalyst and hydrazine as a reducing agent to catalytically reduce uranyl nitrate to uranyl nitrate, achieving a conversion rate of 100% at 60°C.

[0003] Tungsten carbide is a novel catalytic material with surface properties and catalytic performance similar to noble metals, making it a promising candidate for various applications. In addition, tungsten carbide possesses advantages such as strong acid resistance, a large specific surface area, a suitable pore structure, good electrical conductivity, and resistance to poisoning.

[0004] To date, there have been no reports on the hydrogenation reaction of uranyl nitrate (VI) to uranium nitrate (IV) by catalytic reduction of uranyl nitrate (VI) at room temperature using hydrogen as a reducing agent and tungsten carbide supported on silica as a catalyst. Summary of the Invention

[0005] This invention relates to a method for preparing a catalyst for the hydrogenation of uranyl nitrate and its application.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A catalyst for the hydrogenation of uranyl nitrate, the catalyst being composed of two parts: a support of silica and an active component of tungsten carbide, wherein the active component comprises 10-25% by mass, preferably 15-25%.

[0008] The preparation method of the uranyl nitrate hydrogenation catalyst, using the sol-gel method, includes the following steps: A carbon source and a tungsten source are weighed according to a carbon:w molar ratio of C:W = 0.8:1 to 1.25:1, dissolved in water, mixed evenly, and then poured into an ethanol solution containing a silicon source. The mass ratio of silicon source to ethanol is 1:7 to 1:2 (preferably 1:5 to 1:2.5). Citric acid monohydrate is then added, with a molar ratio of citric acid monohydrate to tungsten source of 1:1 to 6:1 (preferably 1.2:1 to 4:1). The mixture is rapidly stirred at 50°C to 80°C for 24 to 48 hours to prepare a sol. The sol is then dried at 80 to 110°C to obtain a gel. The gel is calcined at 1000 to 1200°C (preferably 1000 to 1100°C) under an argon atmosphere for 4 to 10 hours to obtain a silicon dioxide-supported tungsten carbide sample.

[0009] A method for preparing a uranyl nitrate hydrogenation catalyst, wherein the carbon source is one or a combination of two or more of glucose and sucrose.

[0010] A method for preparing a uranyl nitrate hydrogenation catalyst, wherein the tungsten source is one or a combination of two or more of ammonium tungstate and ammonium metatungstate.

[0011] A method for preparing a uranyl nitrate hydrogenation catalyst, wherein the silicon source is one or a combination of two or more of vinyltrimethoxysilane (VTMS) or vinyltriethoxysilane (VTES).

[0012] The application of uranyl nitrate hydrogenation catalyst, wherein hydrogen is used as a reducing agent in the uranyl nitrate hydrogenation catalytic reaction, and the catalyst is sufficient to enable uranyl nitrate (VI) to undergo hydrogenation reaction at room temperature to produce uranyl nitrate (IV).

[0013] The catalyst

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1) Compared with existing catalysts, this catalyst has good activity and stability in the hydrogenation reaction of uranyl nitrate, and can remove UO2 from wastewater. 2+ Restored to recyclable U 4+ This can both reduce uranium-containing wastewater pollution and improve the recycling and utilization of uranium.

[0016] 2) Compared with the same Pt-based catalyst prepared by the traditional impregnation method, the conversion rate of uranyl nitrate reduced by hydrogen is as high as 99% or more at room temperature, which can meet the application requirements of industrialization of uranyl nitrate reduction to uranium nitrate.

[0017] 3) The active component of the catalyst of the present invention is tungsten carbide, which has stronger acid resistance, good conductivity and anti-poisoning performance than conventional noble metal Pt catalysts.

[0018] 4) The carbon and tungsten sources used in this invention are relatively inexpensive and have low production costs, making this method more suitable for large-scale production. Attached Figure Description

[0019] Figure 1 The image shows the XRD pattern of the WC / SiO2 catalyst obtained in Example 1. Detailed Implementation

[0020] The following examples are provided to illustrate the invention in more detail, but the invention is not limited thereto.

[0021] Example 1

[0022] Prepare a WC15 / SiO2 catalyst with a WC content of 15%.

[0023] Dissolve 0.16 g of glucose and 1.34 g of ammonium metatungstate in 15 mL of water. Pour the solution into a mixture containing 14.8 g of VTMS and 80 mL of ethanol. Then add 0.24 g of citric acid monohydrate. Stir rapidly at 80 °C for 24 hours to form a gel. Dry at 80 °C overnight and calcine at 1000 °C for 10 hours under an argon atmosphere to obtain the WC / SiO2 catalyst. XRD results are shown below. Figure 1 As shown in the figure, the structure contains silicon dioxide and tungsten carbide. The specific surface area results are shown in Table 1.

[0024] Example 2

[0025] Prepare a WC10 / SiO2 catalyst with a WC content of 10%.

[0026] The difference from Example 1 is that 0.10 g of glucose and 0.84 g of ammonium metatungstate were dissolved in 15 mL of water, while the amounts of other materials and operating conditions were the same as in Example 1. The specific surface area results are shown in Table 1.

[0027] Example 3

[0028] Prepare a WC10 / SiO2 catalyst with a WC content of 25%.

[0029] Dissolve 0.31g of glucose and 2.53g of ammonium metatungstate in 15mL of water. The amounts of other materials and operating conditions are the same as in Example 1. The specific surface area results are shown in Table 1.

[0030] Example 4

[0031] The difference from Example 1 is that the added carbon source is sucrose, with an amount of 0.15 g. The amounts of other materials and operating conditions are the same as in Example 1. The specific surface area results are shown in Table 1.

[0032] Example 5

[0033] The difference from Example 1 is that the added tungsten source is ammonium tungstate, with an amount of 1.33 g. The mixture is rapidly stirred at 50°C for 48 hours to form a gel. The amounts of other materials and operating conditions are the same as in Example 1. The specific surface area results are shown in Table 1.

[0034] Example 6

[0035] The difference from Example 1 is that VTES replaced VTMS, and the dosage was 19g. The dosage of other materials and other operating conditions were the same as in Example 1. The specific surface area results are shown in Table 1.

[0036] Example 7

[0037] Unlike Example 1, after overnight drying at 80°C, the sample was calcined at 1200°C for 4 hours under an argon atmosphere. The amounts of other materials and other operating conditions were the same as in Example 1. The specific surface area results are shown in Table 1.

[0038] Table 1 Comparison of samples prepared in Examples 1-7

[0039]

[0040] Example 8

[0041] 1.5g of the WC15 / SiO2 catalyst prepared in Example 1 was added to a reactor. The concentration of uranyl nitrate in the reactor was 200g / L, and the concentration of acid in the raw materials was 1.7mol / L. H2 was bubbled into the reactor under a pressure of 4MPa. After 30 minutes, the concentration of uranium in the sampling tube was analyzed. 4+ The concentration was 199.5 g / L, and the conversion rate of uranyl nitrate was 99.75%. The experimental results are shown in Table 2.

[0042] Example 9

[0043] Unlike Example 8, 1.5g of the WC10 / SiO2 catalyst prepared in Example 2 was added to the reactor. The amounts of other materials and operating conditions were the same as in Example 8. The U in the sampling tube... 4+ The concentration was 198.2 g / L, and the conversion rate of uranyl nitrate was 99.10%. The experimental results are shown in Table 2.

[0044] Example 10

[0045] Unlike Example 8, 1.5g of the WC25 / SiO2 catalyst prepared in Example 3 was added to the reactor. The amounts of other materials and operating conditions were the same as in Example 8. The U in the sampling tube... 4+ The concentration was 199.0 g / L, and the conversion rate of uranyl nitrate was 99.50%. The experimental results are shown in Table 2.

[0046] Example 11

[0047] Unlike Example 8, 1.5g of the WC15 / SiO2 catalyst prepared in Example 4 was added to the reactor. The amounts of other materials and operating conditions were the same as in Example 8. The U in the sampling tube... 4+ The concentration was 198.7 g / L, and the conversion rate of uranyl nitrate was 99.35%. The experimental results are shown in Table 2.

[0048] Example 12

[0049] Unlike Example 8, 1.5g of the WC15 / SiO2 catalyst prepared in Example 5 was added to the reactor. The amounts of other materials and operating conditions were the same as in Example 8. The U in the sampling tube... 4+ The concentration was 198.5 g / L, and the conversion rate of uranyl nitrate was 99.25%. The experimental results are shown in Table 2.

[0050] Example 13

[0051] Unlike Example 8, 1.5g of the WC15 / SiO2 catalyst prepared in Example 6 was added to the reactor. The amounts of other materials and operating conditions were the same as in Example 8. The U in the sampling tube... 4+ The concentration was 198.6 g / L, and the conversion rate of uranyl nitrate was 99.30%. The experimental results are shown in Table 2.

[0052] Example 14

[0053] Unlike Example 8, 1.5g of the WC15 / SiO2 catalyst prepared in Example 7 was added to the reactor. The amounts of other materials and operating conditions were the same as in Example 8. The U in the sampling tube... 4+ The concentration was 198.4 g / L, and the conversion rate of uranyl nitrate was 99.20%. The experimental results are shown in Table 2.

[0054] Comparative Example 1

[0055] Unlike Example 8, 1.5g of Pt3 / SiO2 (Pt content 3wt%) catalyst prepared by the conventional impregnation method was added to the reactor. The amounts of other materials and operating conditions were the same as in Example 8. U was sampled from the tube. 4+ The concentration was 196.0 g / L, and the conversion rate of uranyl nitrate was 98.00%. The experimental results are shown in Table 2.

[0056] Table 2 Results of uranyl nitrate hydrogenation tests in Examples 8-14 and Comparative Example 1

[0057]

[0058]

[0059] Results Evaluation and Analysis: As can be seen from Table 2, the activity of the silica-supported tungsten carbide catalyst (Examples 8-14) is higher than that of the silica-supported Pt catalyst (Comparative Example 1). Using hydrogen as a reducing agent, it can reduce uranyl nitrate (VI) to uranium nitrate (IV) at room temperature with a conversion rate of over 99%.

Claims

1. An application of a uranyl nitrate hydrogenation catalyst, characterized in that, In the hydrogenation catalytic reaction of uranyl nitrate, hydrogen is used as a reducing agent. The catalyst enables uranyl nitrate (VI) to undergo a hydrogenation reaction at room temperature to produce uranyl nitrate (IV). The catalyst consists of two parts: a support of silica and an active component of tungsten carbide. The mass percentage of the active component in the catalyst is 10-25%.

2. The application according to claim 1, characterized in that, The active component in the catalyst has a mass percentage of 15-25%.

3. The application according to claim 1, characterized in that, The sol-gel method was used to prepare the sample, which included the following steps: Carbon and tungsten sources were weighed according to a carbon:W molar ratio of C:W = 0.8:1~1.25:1, dissolved in water, and mixed thoroughly. The mixture was then poured into an ethanol solution containing a silicon source, with a silicon source to ethanol mass ratio of 1:7~1:

2. Citric acid monohydrate was then added, with a citric acid monohydrate to tungsten source molar ratio of 1:1~6:

1. The mixture was rapidly stirred at 50℃~80℃ for 24~48 hours to prepare a sol. The sol was then dried at 80~110℃ to obtain a gel. The gel was calcined at 1000~1200℃ under an argon atmosphere for 4~10 hours to obtain a silicon dioxide-supported tungsten carbide sample.

4. The application according to claim 3, characterized in that, The mass ratio of silicon source to ethanol is 1:5 to 1:2.5, and the molar ratio of citric acid monohydrate to tungsten source is 1.2:1 to 4:

1. The gel is then calcined at 1000 to 1100°C under an argon atmosphere.

5. The application according to claim 3, characterized in that, The carbon source is one or two of glucose and sucrose.

6. The application according to claim 3, characterized in that, The tungsten source is one or two of ammonium tungstate and ammonium metatungstate.

7. The application according to claim 3, characterized in that, The silicon source is one or both of vinyltrimethoxysilane (VTMS) or vinyltriethoxysilane (VTES).

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