CN114308021B - Method for catalyzing hydrazine to reduce uranium by composite carrier catalyst - Google Patents
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Abstract
The invention relates to a method for catalyzing hydrazine to reduce uranium by a composite carrier catalyst, which mainly realizes that the uranium is prepared into a uranium-tetravalent solution by catalyzing hydrazine to reduce hexavalent uranium under an acidic condition, and obtains higher uranium-tetravalent yield. The catalyst is formed by loading active component metal on a Ti-M composite carrier, and comprises the following components in parts by mass: a) Ti in the Ti-M composite carrier is titanium oxide, and the Ti accounts for 50-99.9 percent; b) The active component is selected from any one of metals Pt, pd, ru, ir, rh, au, and the active component accounts for 0.001-20% of the total weight of the components; c) M in the Ti-M composite carrier is selected from SiO 2 、Al 2 O 3 、ZrO 2 One or more than two of the components accounting for 0.001 to 40 percent. The catalyst provided by the invention can directly catalyze hydrazine to reduce hexavalent uranium into tetravalent uranium under mild conditions in an acidic system, the yield of the tetravalent uranium can reach 99%, and the reaction rate can reach 135.7g U4 g ‑1 min ‑1 。
Description
Technical Field
The invention relates to a method for catalyzing hydrazine to reduce uranium by a composite carrier catalyst.
Background
Nuclear fuel post-treatment technology is an important part of the nuclear industry. Post-treatment is carried out on spent fuel (used nuclear fuel in a reactor), uranium (U) and plutonium (Pu) are separated and recycled to be reused as nuclear fuel, and geological disposal is carried out on high-radioactivity waste, so that the method is important for the safety and sustainable development of nuclear energy in China.
Key to spent fuel reprocessing technology is the separation of uranium, plutonium, and other fissile elements. At present, post-treatment factories at home and abroad mainly adopt a Purex process, and the separation of uranium and plutonium is realized by utilizing the small extraction capacity of tributyl phosphate (TBP) to trivalent plutonium. However, the pretreated plutonium is in a tetravalent state, and a reducing agent is added to reduce the tetravalent plutonium (Pu (IV)) to trivalent plutonium (Pu (III)) which is not easily extracted. When hydrazine is used as a supporting reducing agent, tetravalent uranium (U (IV)) is a better reducing stripping agent of tetravalent plutonium (Pu (IV)), and has the advantages of complete reduction stripping of plutonium, no introduction of impurities into a system, high reaction rate and the like, so that the method is widely applied. Therefore, most of the spent fuel post-treatment plants running and under construction use hydrazine stable U (IV) as a reduction stripping agent, such as UP3, UP2-800 in France, pilot plant in China and the like.
At present, the production of tetravalent uranium mainly comprises an electrolytic reduction method, a hydrogenation reduction method, a liquid phase reduction method and the like. The electrolytic reduction method is carried out by electrolyzing uranyl nitrate (UO) 2 (NO 3 ) 2 ) The method is reduced into tetravalent uranium (U (IV)), and has the advantages of simple process, no introduction of impurities and the like. However, in actual production, the conversion rate of hexavalent uranium (U (VI)) in the electrolytic reduction method is lower, generally 50-60%, so that the concentration of the tetravalent uranium in the product is lower. When it is used as a reducing agentNot only can the dilution of the plutonium product occur, but also the recycling burden of the uranium product can be increased. Hydrogenation reduction method for using high-pressure hydrogen to make UO 2 (NO 3 ) 2 The solution is reduced into U (IV), which has the advantages of high production capacity, high U (IV) yield and the like. However, the hydrogenation reduction method has complex production equipment, and the use of high-pressure hydrogen is a great potential safety hazard in a nuclear fuel post-treatment workshop with extremely strong radioactivity. Under the action of a catalyst, the U (VI) can be reduced to U (IV) by adopting organic reducing agents such as hydrazine, and the method has mild reaction conditions (normal temperature and normal pressure) and simple preparation process, and is a very promising preparation method of the U (VI).
N 2 H 5 + +3H + +2UO 2 2+ →2U 4+ +N 2 +4H 2 O (1)
Li and the like, a process condition of a reaction for preparing U (IV) by reducing U (VI) by hydrazine in a nitric acid system is studied by taking platinum black as a catalyst. When the uranium concentration is 0.9mol/L, HNO 3 When the concentration is 0.8mol/L and the hydrazine concentration is 1mol/L, the conversion rate of U (VI) can reach more than 90 percent at 60 ℃. (Nuclear chemistry and radiochemistry, 2013,35, (1): 24-28). Boltoeva et al examined Pt/SiO 2 Catalyst at H 2 SO 4 、HClO 4 、HNO 3 Particle size effect of Pt in U (IV) by hydrazine reduction in the system. It was found that U (VI) conversion increased with increasing Pt particle size (Radiochemistry, 2007,49,603-606). Anan' ev et al examined the reactivity of hydrazine with U (IV) from U (VI) in a formic acid reduction system (Radiochemistry, 2001,43,39-43). At present, research on the reaction of preparing U (IV) by reducing U (VI) with hydrazine is mainly focused on the investigation of dynamics and process conditions, and the research on the optimization design of a catalyst is less.
At present, a plurality of tetravalent uranium solution preparation applications are filed. The following list of several reported patents are detailed:
chinese patent CN201110097474 publication name: a preparation method of a tetravalent uranium solution. The patent reports the preparation of U (IV) solutions by reduction of U (VI) with organic reducing agents (hydrazine or carboxylic acids and derivatives thereof) over Pt, pd, rh catalysts. The process and method of preparing the catalyst is not addressed in this patent.
Chinese patent CN201310743451 publication name: an apparatus for preparing tetravalent uranium by electrolytic reduction. The patent reports an improved device for preparing tetravalent uranium by electrolytic reduction, and mainly solves the problem of lower U (VI) conversion rate in a diaphragm-free electrolytic device. In actual production, the effectiveness of the device needs to be further checked.
U (VI) can be reduced to U (IV) by utilizing hydrazine under the action of a noble metal catalyst in an acid system. And through the optimal design of the catalyst, the capability of reducing U (VI) by hydrazine is modulated, so that the activity of the catalyst and the utilization rate of hydrazine are improved, and the efficient production of U (IV) is expected to be realized under mild conditions.
Disclosure of Invention
One of the technical problems to be solved by the invention is to solve the problem of preparing the U (IV) catalyst by reducing U (VI) with hydrazine in an acid system, and provide a novel catalyst which can obtain high U (VI) conversion rate under mild conditions and has higher reaction rate.
The second technical problem to be solved by the invention is to adopt the preparation method of the catalyst in one of the technical problems. The method utilizes the Ti-M composite carrier, and can effectively improve the interaction between the carrier and the active component.
The third technical problem to be solved by the invention is to adopt the catalyst in one of the technical problems to realize the catalytic reaction process for preparing U (IV) by reducing U (VI) with hydrazine under an acidic condition.
In order to solve one of the technical problems, the invention adopts the following technical scheme: the noble metal catalyst for preparing U (IV) by reducing U (VI) with hydrazine under an acidic condition comprises the following components in parts by mass: a) Titanium oxide accounting for 50 to 99.9 percent; b) The active component is selected from any one of metals Pt, pd, ru, ir, rh, au, and the active component accounts for 0.001-20% of the total weight of the components; c) Selected from SiO 2 、Al 2 O 3 、ZrO 2 One or more than two of the components accounting for 0.001 to 40 percent.
In the scheme, the method is characterized in that: the component a) of the catalyst is preferably titanium oxide of rutile type titanium dioxide or anatase type di-oxideOne or two of titanium oxide, the preferable content is 89-99%; component b) is preferably any one of metals Pt, pd, ru, ir, preferably in an amount of 0.1 to 10%; component c) is preferably SiO 2 、ZrO 2 Any one or more of the oxides in the (a) is preferably contained in an amount of 0.01 to 10%.
In order to solve the second technical problem, the invention adopts the following technical scheme:
a)TiO 2 is prepared from
1) Dissolving soluble titanium salt in 6-12mol/L concentrated hydrochloric acid to obtain solution A; wherein the concentration of titanium ions is 0.001-10 mol/L;
2) Dissolving alkali into deionized water to prepare a precipitant to obtain a solution B with the concentration of 0.01-10 mol/L;
3) Dropwise adding the solution B into the solution A until the pH value of the mixed solution is 7-10, and then stirring and aging the obtained mixture in a water bath at 25-90 ℃ for 0.5-24 h;
4) Filtering and washing the obtained turbid liquid, and drying a filter cake in air for 12-48 hours at 50-200 ℃;
5) Roasting the dried solid in air atmosphere at 200-900 ℃ for 1-8 h to obtain TiO 2 。
b) Preparation of Ti-M composite carrier
1) The Ti-M composite carrier is prepared by adopting an impregnation method, wherein M is one or more than two of Si and Zr. Dissolving one or more than two of a soluble Si source and a soluble Zr source in deionized water or absolute ethyl alcohol to prepare a solution C, wherein the concentration of M is 0.001-10 mol/L.
2) Taking prepared TiO 2 The carrier is used for dripping or pouring the solution C with the required quantity into TiO according to the mass fraction of M 2 Is a kind of medium.
3) Immersing the mixture in the step (2) for 0.5-48 h at room temperature;
4) Drying the mixture obtained in the step (3) for 4-24 hours at the temperature of 60-120 ℃;
5) Roasting the dried mixture at 300-950 ℃ for 1-8 hours to obtain the Ti-M composite carrier.
c) Preparation of noble metal catalysts
1) Dissolving any one of the soluble salts in Pt, pd, ru, ir, rh, au in deionized water to prepare solution D, wherein the concentration of noble metal ions is 0.001-0.5 mol/L;
2) The noble metal catalyst is prepared by adopting an impregnation method. Taking a Ti-M composite carrier, and dripping or pouring a required amount of solution D into the Ti-M composite carrier according to the content of noble metal in the catalyst;
3) Immersing the mixture in the step (2) for 0.5-48 h at room temperature;
4) Drying the mixture obtained in the step (3) for 4-24 hours at the temperature of 60-120 ℃;
5) Roasting the dried mixture at 200-500 ℃ for 1-8 h;
6) The solid obtained in the step (5) is subjected to the reduction and activation process that: reducing gas to H 2 (molar purity)>99.9 percent) and the volume airspeed of the reducing gas is 100-3600h -1 The temperature rising rate from room temperature to reduction temperature is 1-10 ℃/min, the reduction temperature is 200-600 ℃, the pressure is normal pressure, and the reduction time is 1-48h.
TiO 2 In the preparation of (2), the alkali is one or more than two of ammonia water, sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate;
TiO 2 in preparation step 5) of (2) calcination may be carried out in a flowing or stationary air atmosphere; wherein, the temperature is raised from room temperature or the drying temperature to the roasting temperature by adopting the programmed temperature rise, and the temperature rise rate is 0.5-10 ℃/min;
the Si source in the step 1) of preparing the Ti-M composite carrier is one or two of ethyl orthosilicate and butyl orthosilicate; the Zr source is one or more than two of zirconium nitrate, zirconyl nitrate, zirconium oxychloride and zirconium sulfate.
The soluble salt of Pt, pd, ru, ir, rh, au in the preparation step 1) of the noble metal catalyst is one of nitrate or chloride of corresponding noble metal;
the roasting temperature in the preparation step 5) of the noble metal catalyst is 300-500 ℃ and the roasting time is 1-6 h;
in order to solve the third technical problem, the invention adopts the following technical scheme: in an acidic system, hydrazine is used as a reducing agent to reduce hexavalent uranium into tetravalent uranium solution. The conditions for preparing the tetravalent uranium solution by hydrazine reduction of hexavalent uranium by the catalyst applied to the stirred tank reactor or the fixed bed reactor are as follows: the acid concentration (calculated by the hydrogen ion concentration) is 0.5-1.0mol/L, the uranyl ion concentration is 0.5-1.3mol/L, the hydrazine concentration is 0.5-2.0mol/L, the reaction temperature is 25-70 ℃, and the reaction pressure is normal pressure.
The invention has the advantages that:
(1) The catalyst provided by the invention has stable properties, and is beneficial to prolonging the service life of the catalyst.
(2) The catalyst provided by the invention can reduce U (VI) into U (IV) solution by utilizing hydrazine under an acidic condition. The interaction between the composite carrier and noble metal in the catalyst improves the conversion rate and the reaction rate of U (VI). In a stirred tank reactor, U (VI) conversion can reach 99% within 60 min. And the reaction rate reaches 135.7g U4 g -1 min -1 。
Detailed Description
The technical details of the present invention are described in detail by the following examples. It should be noted that the illustrated embodiments are only for further illustrating technical features of the present invention, and are not limiting the present invention.
Catalyst preparation and performance evaluation
Example 1
20ml TiCl was taken 4 The solution was slowly added dropwise to 50ml of 10mol/L concentrated hydrochloric acid to prepare solution A, the concentration of titanium ions being 2.60mol/L. 100ml of 10mol/L ammonia water (solution B) was added to the mixture A at a flow rate of 1ml/min using a constant flow pump, and the pH of the solution after the addition was about 10. The mixture is placed in a water bath with the temperature of 60 ℃ and is continuously stirred and aged for 4 hours. Filtering and washing the obtained turbid liquid to be neutral, and then drying a filter cake in air at 80 ℃ for 24 hours; roasting the dried solid for 4 hours in an air atmosphere at 500 ℃ to obtain rutile type titanium dioxide, r-TiO 2 。
2.0g of the r-TiO prepared above were weighed out 2 0.77g of ethyl orthosilicate is weighed and dissolved in 10ml of absolute ethyl alcohol to prepare a mixed solution, and the concentration of the ethyl acetate is0.37mol/L, drop-wise to TiO 2 And mixing them uniformly. Soaking at room temperature for 12h, drying at 80deg.C for 12h, calcining at 400deg.C in air atmosphere for 4h, grinding, tabletting, crushing, and sieving (20-40 mesh) to obtain Ti-Si composite carrier, wherein SiO 2 The mass content is 10 percent and is recorded as r-Ti-10Si.
Weigh 2.0g of Ti-10Si composite support and weigh 0.1642g H 2 PtCl 6 ·6H 2 O is dissolved in 2ml deionized water to prepare a mixed solution, the molar concentration of Pt is 0.16mol/L, and the mixed solution is dropwise added into the Ti-10Si composite carrier and uniformly mixed. Soaking for 12h at room temperature, drying at 80deg.C for 12h, and calcining at 400deg.C in air atmosphere for 4h, wherein Pt mass content is 3%, siO 2 The mass content is 9.7%, and the rest is TiO 2 The catalyst was designated as 3Pt/r-Ti-10Si catalyst.
Catalyst reduction activation conditions: reducing gas to pure H 2 (molar purity)>99.9 percent, airspeed of 2000h -1 The temperature rising rate is 5 ℃/min, the reduction temperature is 400 ℃, the pressure is normal pressure, and the reduction time is 4h. The catalyst is used for stirring reaction conditions in a kettle: nitric acid concentration (calculated by hydrogen ion concentration) is 1.0mol/L, uranyl ion concentration is 0.9mol/L, hydrazine concentration is 1.0mol/L, temperature is 60 ℃, stirring speed is 800rpm, and pressure is normal pressure. The reaction results are shown in Table 1.
Example 2
10ml TiCl was taken 4 The solution was slowly added dropwise to 20ml of 12mol/L concentrated hydrochloric acid to prepare solution A, the concentration of titanium ions being 3.03mol/L. 50ml of 10mol/L ammonia water (solution B) was added to the mixture A at a flow rate of 1ml/min by means of a constant flow pump, and the pH of the solution after the addition was about 9. The mixture is placed in a water bath with the temperature of 30 ℃ and is continuously stirred and aged for 24 hours. Filtering and washing the obtained turbid liquid to be neutral, and then drying a filter cake in air at 60 ℃ for 48 hours; roasting the dried solid in air atmosphere at 300 ℃ for 1h to obtain rutile type titanium dioxide, r1-TiO 2 。
2.0g of the r1-TiO prepared above are weighed out 2 0.77g of ethyl orthosilicate is weighed and dissolved in 10ml of absolute ethyl alcohol to prepare a mixed solution, the concentration of the ethyl orthosilicate is 0.37mol/L, and the mixed solution is poured into r-TiO 2 Mixed solutionAnd mixing them uniformly. Soaking at room temperature for 0.5h, drying at 60deg.C for 24h, calcining at 300deg.C in air atmosphere for 1h, grinding, tabletting, crushing, and sieving (20-40 mesh) to obtain Ti-Si composite carrier, wherein SiO 2 The mass content is 10 percent and is expressed as r1-Ti-10Si.
2.0g of r1-Ti-10Si composite carrier was weighed out, 0.1031g of PdCl was weighed out 2 Dissolving the mixture in 2ml deionized water and 1ml concentrated hydrochloric acid to prepare a mixed solution, wherein the molar concentration of Pd is 0.19mol/L, dripping the mixed solution into the r1-Ti-10Si composite carrier, and uniformly mixing the mixed solution. Soaking for 1h at room temperature, drying at 60deg.C for 4h, and calcining at 300deg.C in air atmosphere for 1h, wherein Pd mass content is 3%, siO 2 The mass content is 9.7%, and the rest is TiO 2 The catalyst is 3Pd/r1-Ti-10 Si.
Catalyst reduction activation conditions: reducing gas to pure H 2 (molar purity)>99.9 percent, airspeed of 200h -1 The temperature rising rate is 5 ℃/min, the reduction temperature is 200 ℃, the pressure is normal pressure, and the reduction time is 1h. The catalyst is used for stirring reaction conditions in a kettle: nitric acid concentration (calculated by hydrogen ion concentration) is 0.5mol/L, uranyl ion concentration is 0.5mol/L, hydrazine concentration is 0.5mol/L, temperature is 25 ℃, stirring speed is 800rpm, and pressure is normal pressure. The reaction results are shown in Table 1.
Example 3
10ml of tetrabutyl titanate solution is slowly dripped into 20ml of concentrated hydrochloric acid with the concentration of 12mol/L to prepare solution A, and the concentration of titanium ions is 0.97mol/L. 300ml of 1mol/L sodium hydroxide (solution B) was added to the mixture A at a flow rate of 1ml/min using a constant flow pump, and the pH of the solution after the addition was about 9. The mixed solution is placed in a water bath with the temperature of 90 ℃ and is continuously stirred for aging for 0.5h. Filtering and washing the obtained turbid liquid to be neutral, and then drying a filter cake in air at 200 ℃ for 12 hours; roasting the dried solid for 8 hours in an air atmosphere at 900 ℃ to obtain rutile type titanium dioxide, r2-TiO 2 。
2.0g of the r2-TiO prepared above are weighed out 2 1.18g of butyl orthosilicate is weighed and dissolved in 10ml of absolute ethyl alcohol to prepare a mixed solution, the concentration of the butyl orthosilicate is 0.37mol/L, and the mixed solution is poured into r1-TiO 2 Mixing the above solutions, and mixing. Room temperature soakingSoaking for 48 hr, drying at 120deg.C for 4 hr, calcining at 950 deg.C in air atmosphere for 1 hr, grinding, tabletting, crushing, sieving (20-40 mesh) to obtain Ti-Si composite carrier, wherein SiO 2 The mass content is 10 percent and is expressed as r2-Ti-10Si.
2.0g of r2-Ti-10Si composite carrier was weighed out, and 0.1672g of RuCl was weighed out 3 ·3H 2 O is dissolved in 2ml deionized water to prepare a mixed solution, the molar concentration of Ru is 0.40mol/L, and the mixed solution is dripped into the r2-Ti-10Si composite carrier and is uniformly mixed. Soaking for 48h at room temperature, drying at 120deg.C for 24h, and calcining at 500deg.C in air atmosphere for 6h, wherein Ru mass content is 3%, siO 2 The mass content is 9.7%, and the rest is TiO 2 The catalyst is marked as 3Ru/r2-Ti-10Si catalyst.
Catalyst reduction activation conditions: reducing gas to pure H 2 (molar purity)>99.9%) space velocity of 3600h -1 The temperature rising rate is 5 ℃/min, the reduction temperature is 600 ℃, the pressure is normal pressure, and the reduction time is 4h. The catalyst is used for stirring reaction conditions in a kettle: the nitric acid concentration (calculated by the concentration of hydrogen ions) is 1.0mol/L, the uranyl ion concentration is 1.3mol/L, the hydrazine concentration is 2.0mol/L, the temperature is 70 ℃, the stirring speed is 800rpm, and the pressure is normal pressure. The reaction results are shown in Table 1.
Example 4
2.0g of the r-Ti-10Si composite support prepared in example 1 was weighed out, and 0.1660. 0.1660g H g was weighed out 2 IrCl 6 ·6H 2 O is dissolved in 2ml deionized water to prepare a mixed solution, the molar concentration of Ir is 0.19mol/L, the mixed solution is dripped into an r-Ti-10Si composite carrier, and the mixed solution is uniformly mixed. Soaking for 12h at room temperature, drying at 60deg.C for 12h, and calcining at 400deg.C in air atmosphere for 4h, wherein Ir mass content is 3%, siO 2 The mass content is 9.7%, and the rest is TiO 2 The catalyst is 3Ir/r-Ti-10 Si.
Catalyst reduction activation conditions: reducing gas to pure H 2 (molar purity)>99.9 percent, airspeed of 2000h -1 The temperature rising rate is 5 ℃/min, the reduction temperature is 400 ℃, the pressure is normal pressure, and the reduction time is 4h. The catalyst is used for stirring reaction conditions in a kettle: nitric acid concentration (calculated by hydrogen ion concentration) of 0.8mol/L and uranyl ion concentration of 0.9The concentration of hydrazine is 1.0mol/L, the temperature is 50 ℃, the stirring speed is 800rpm, and the pressure is normal pressure. The reaction results are shown in Table 1.
Example 5
2.0g of the r-Ti-10Si composite support prepared in example 1 was weighed out, and 0.1258g of RhCl was weighed out 3 Dissolving the mixed solution in 2ml of deionized water to prepare a mixed solution, dropwise adding the mixed solution into an r-Ti-10Si composite carrier, wherein the molar concentration of Rh is 0.30mol/L, and uniformly mixing the mixed solution. Soaking for 12h at room temperature, drying at 60deg.C for 12h, and calcining at 400deg.C in air atmosphere for 4h, wherein Rh mass content is 3%, siO 2 The mass content is 9.7%, and the rest is TiO 2 The catalyst was designated as 3Rh/r-Ti-10Si catalyst.
Catalyst reduction activation conditions: reducing gas to pure H 2 (molar purity)>99.9 percent, airspeed of 2000h -1 The temperature rising rate is 5 ℃/min, the reduction temperature is 400 ℃, the pressure is normal pressure, and the reduction time is 4h. The catalyst is used for stirring reaction conditions in a kettle: nitric acid concentration (calculated by hydrogen ion concentration) is 1.0mol/L, uranyl ion concentration is 0.9mol/L, hydrazine concentration is 1.0mol/L, temperature is 60 ℃, stirring speed is 800rpm, and pressure is normal pressure. The reaction results are shown in Table 1.
Example 6
2.0g of the r-Ti-10Si composite support prepared in example 1 was weighed out, and 0.1293g of HAuCl was weighed out 4 ·4H 2 O is dissolved in 2ml deionized water to prepare a mixed solution, the molar concentration of Au is 0.19mol/L, and the mixed solution is dripped into the r-Ti-10Si composite carrier and is uniformly mixed. Soaking for 12h at room temperature, drying at 60deg.C for 12h, and calcining at 400deg.C in air atmosphere for 4h, wherein Au content is 3% and SiO mass content is 3% 2 The mass content is 9.7%, and the rest is TiO 2 The catalyst was designated 3Au/r-Ti-10 Si.
Catalyst reduction activation conditions: reducing gas to pure H 2 (molar purity)>99.9 percent, airspeed of 2000h -1 The temperature rising rate is 5 ℃/min, the reduction temperature is 400 ℃, the pressure is normal pressure, and the reduction time is 4h. The catalyst is used for stirring reaction conditions in a kettle: nitric acid concentration (calculated by hydrogen ion concentration) of 1.0mol/L, uranyl ion concentration of 0.9mol/L, hydrazine concentration of 1.0mol/L, temperature of 60 ℃ and stirring rate of800rpm, the pressure was normal pressure. The reaction results are shown in Table 1.
Example 7
2.0g of the r-Ti-10Si composite support prepared in example 1 was weighed out, and 0.0265g H was weighed out 2 PtCl 6 ·6H 2 O is dissolved in 2ml deionized water to prepare a mixed solution, the molar concentration of Pt is 0.025mol/L, and the mixed solution is dripped into the Ti-10Si composite carrier and uniformly mixed. Soaking for 12h at room temperature, drying at 60deg.C for 12h, and calcining at 400deg.C in air atmosphere for 4h, wherein Pt mass content is 0.5%, siO 2 The mass content is 9.95 percent, and the rest is TiO 2 The catalyst was designated as 0.5Pt/r-Ti-10Si catalyst.
Catalyst reduction activation conditions: reducing gas to pure H 2 (molar purity)>99.9 percent, airspeed of 2000h -1 The temperature rising rate is 5 ℃/min, the reduction temperature is 400 ℃, the pressure is normal pressure, and the reduction time is 4h. The catalyst is used for stirring reaction conditions in a kettle: nitric acid concentration (calculated by hydrogen ion concentration) is 1.0mol/L, uranyl ion concentration is 0.9mol/L, hydrazine concentration is 1.0mol/L, temperature is 60 ℃, stirring speed is 800rpm, and pressure is normal pressure. The reaction results are shown in Table 1.
Example 8
2.0g of the r-Ti-10Si composite support prepared in example 1 was weighed out, and 0.5902g H was weighed out 2 PtCl 6 ·6H 2 O is dissolved in 2ml deionized water to prepare a mixed solution, the molar concentration of Pt is 0.57mol/L, and the mixed solution is dropwise added into the Ti-10Si composite carrier and uniformly mixed. Soaking for 12h at room temperature, drying at 60deg.C for 12h, and calcining at 400deg.C in air atmosphere for 4h, wherein Pt mass content is 10%, siO 2 9% by mass and the balance of TiO 2 The catalyst was designated as 10Pt/r-Ti-10Si catalyst.
Catalyst reduction activation conditions: reducing gas to pure H 2 (molar purity)>99.9 percent, airspeed of 2000h -1 The temperature rising rate is 5 ℃/min, the reduction temperature is 400 ℃, the pressure is normal pressure, and the reduction time is 4h. The catalyst is used for stirring reaction conditions in a kettle: nitric acid concentration (calculated by hydrogen ion concentration) of 1.0mol/L, uranyl ion concentration of 0.9mol/L, hydrazine concentration of 1.0mol/L, temperature of 60 ℃, stirring speed of 800rpm, and pressure ofAtmospheric pressure. The reaction results are shown in Table 1.
Example 9
2.0g of the r-TiO prepared in example 1 are weighed out 2 0.77g of zirconium nitrate was weighed and dissolved in 10ml of water to prepare a mixed solution, the molar concentration of Zr was 0.18mol/L, and TiO was prepared 2 Pouring the mixture into the mixed solution, and uniformly mixing the mixture. Soaking at room temperature for 12h, drying at 60deg.C for 12h, calcining at 500deg.C in air atmosphere for 4h, grinding, tabletting, crushing, and sieving (20-40 mesh) to obtain r-Ti-Zr composite carrier, wherein ZrO 2 The mass content is 10 percent and is recorded as r-Ti-10Zr.
2.0g r-Ti-10Zr composite carrier is weighed and 0.1642g H is weighed 2 PtCl 6 ·6H 2 O is dissolved in 2ml deionized water to prepare a mixed solution, the molar concentration of Pt is 0.16mol/L, and the r-Ti-10Zr composite carrier is poured into the mixed solution and uniformly mixed. Soaking for 12h at room temperature, drying at 60deg.C for 12h, and calcining at 800deg.C under air atmosphere for 4h, wherein Pt mass content is 3%, zrO 2 The mass content is 9.7%, and the rest is TiO 2 The catalyst was designated as 3Pt/r-Ti-10Zr catalyst.
Catalyst reduction activation conditions: reducing gas to pure H 2 (molar purity)>99.9 percent, airspeed of 2000h -1 The temperature rising rate is 5 ℃/min, the reduction temperature is 300 ℃, the pressure is normal pressure, and the reduction time is 4h. The catalyst is used for stirring reaction conditions in a kettle: nitric acid concentration (calculated by hydrogen ion concentration) is 1.0mol/L, uranyl ion concentration is 0.9mol/L, hydrazine concentration is 1.0mol/L, temperature is 60 ℃, stirring speed is 800rpm, and pressure is normal pressure. The reaction results are shown in Table 1.
Example 10
2.0g of the r-TiO prepared in example 1 are weighed out 2 1.64g of aluminum nitrate was weighed and dissolved in 10ml of water to prepare a mixed solution, the molar concentration of Al was 0.44mol/L, and TiO was prepared 2 Pouring the mixture into the mixed solution, and uniformly mixing the mixture. Soaking at room temperature for 12h, drying at 60deg.C for 12h, calcining at 500deg.C in air atmosphere for 4h, grinding, tabletting, crushing, and sieving (20-40 mesh) to obtain r-Ti-Al composite carrier, wherein Al 2 O 3 The mass content is 10%, recordIs r-Ti-10Al.
2.0g r-Ti-10Al composite carrier is weighed and 0.1642g H is weighed 2 PtCl 6 ·6H 2 O is dissolved in 2ml deionized water to prepare a mixed solution, the molar concentration of Pt is 0.16mol/L, and the r-Ti-10Al composite carrier is poured into the mixed solution and uniformly mixed. Soaking for 12h at room temperature, drying at 60deg.C for 12h, and calcining at 500 deg.C in air atmosphere for 4h, wherein Pt mass content is 3%, al 2 O 3 The mass content is 9.7%, and the rest is TiO 2 The catalyst was designated as 3Pt/r-Ti-10Al catalyst.
Catalyst reduction activation conditions: reducing gas to pure H 2 (molar purity)>99.9 percent, airspeed of 2000h -1 The temperature rising rate is 5 ℃/min, the reduction temperature is 300 ℃, the pressure is normal pressure, and the reduction time is 4h. The catalyst is used for stirring reaction conditions in a kettle: nitric acid concentration (calculated by hydrogen ion concentration) is 1.0mol/L, uranyl ion concentration is 0.9mol/L, hydrazine concentration is 1.0mol/L, temperature is 60 ℃, stirring speed is 800rpm, and pressure is normal pressure. The reaction results are shown in Table 1.
Example 11
20ml TiCl was taken 4 The solution was slowly added dropwise to 50ml of 12mol/L concentrated hydrochloric acid to prepare solution A, the concentration of titanium ions being 2.60mol/L. 100ml of 10mol/L ammonia water (solution B) is added into the mixed solution A by a constant flow pump at a flow rate of 1ml/min, the mixed solution is placed in a water bath with 70 ℃ for continuous stirring, and the mixed solution is aged for 12 hours after the dripping is finished. Filtering and washing the obtained turbid liquid to be neutral, and then drying a filter cake in air at 80 ℃ for 12 hours; roasting the dried solid for 4 hours in an air atmosphere at 300 ℃ to obtain anatase titanium dioxide, A-TiO 2 。
Weigh 2.0g of A-TiO prepared as described above 2 Weighing 0.77g of ethyl orthosilicate, dissolving the ethyl orthosilicate in 10ml of absolute ethyl alcohol to prepare a mixed solution, wherein the concentration of the ethyl orthosilicate is 0.37mol/L, and preparing the TiO 2 Pouring the mixture into the mixed solution, and uniformly mixing the mixture. Soaking at room temperature for 12h, drying at 60deg.C for 12h, calcining at 400deg.C in air atmosphere for 4h, grinding, tabletting, crushing, and sieving (20-40 mesh) to obtain Ti-Si composite carrier, wherein SiO 2 The mass content is 10 percent and is recorded as Ti-A-10Si。
Weigh 2.0g of Ti-A-10Si composite support, weigh 0.1642g H 2 PtCl 6 ·6H 2 O is dissolved in 2ml deionized water to prepare a mixed solution, the molar concentration of Pt is 0.16mol/L, and the Ti-A-10Si composite carrier sample is poured into the mixed solution and uniformly mixed. Soaking for 12h at room temperature, drying at 60deg.C for 12h, and calcining at 400deg.C in air atmosphere for 4h, wherein Pt mass content is 3%, siO 2 The mass content is 9.7%, and the rest is TiO 2 The catalyst was designated as 3Pt/Ti-A-10Si catalyst.
Catalyst reduction activation conditions: reducing gas to pure H 2 (molar purity)>99.9 percent, airspeed of 2000h -1 The temperature rising rate is 5 ℃/min, the reduction temperature is 300 ℃, the pressure is normal pressure, and the reduction time is 4h. The catalyst is used for stirring reaction conditions in a kettle: the nitric acid concentration (calculated by the concentration of hydrogen ions) is 1.0mol/L, the uranyl ion concentration is 0.9mol/L, the hydrazine concentration is 1.0mol/L, the temperature is 60 ℃, the stirring speed is 800rpm, and the pressure is normal pressure. The reaction results are shown in Table 1.
Example 12
The 3Pt/r-Ti-10Si catalyst subjected to reduction activation in example 1 was taken. The catalyst is used for stirring reaction conditions in a kettle: the sulfuric acid concentration is 0.5mol/L (1.0 mol/L in terms of hydrogen ion concentration), the uranyl ion concentration is 0.9mol/L, the hydrazine concentration is 1.0mol/L, the temperature is 60 ℃, the stirring speed is 800rpm, and the pressure is normal pressure. The reaction results are shown in Table 1.
Example 13
The 3Pt/r-Ti-10Si catalyst subjected to reduction activation in example 1 was taken. The catalyst is used for stirring reaction conditions in a kettle: the perchloric acid concentration is 1.0mol/L (1.0 mol/L in terms of hydrogen ion concentration), the uranyl ion concentration is 0.9mol/L, the hydrazine concentration is 1.0mol/L, the temperature is 60 ℃, the stirring speed is 800rpm, and the pressure is normal pressure. The reaction results are shown in Table 1.
Example 14
The 3Pt/r-Ti-10Si catalyst subjected to reduction activation in example 1 was taken. Reaction conditions in the fixed bed: nitric acid concentration (calculated by hydrogen ion concentration) of 1.0mol/L, uranyl ion concentration of 0.9mol/L, hydrazine concentration of 1.0mol/L, temperature of 60 ℃ and liquid space velocity of0.3h -1 The pressure is normal pressure. The reaction results are shown in Table 1.
Example 15
2.0g of the r-TiO prepared in example 1 are weighed out 2 0.0070g of ethyl orthosilicate is weighed and dissolved in 2ml of absolute ethyl alcohol to prepare a mixed solution, the molar concentration of Si is 0.016mol/L, and the mixed solution is added dropwise to TiO 2 And mixing them uniformly. Soaking at room temperature for 12h, drying at 80deg.C for 12h, calcining at 400deg.C in air atmosphere for 4h, grinding, tabletting, crushing, and sieving (20-40 mesh) to obtain Ti-Si composite carrier, wherein SiO 2 The mass content is 0.1%, which is expressed as r-Ti-0.1Si.
Weigh 2.0. 2.0g r-Ti-0.1Si composite support and weigh 0.1642g H 2 PtCl 6 ·6H 2 O is dissolved in 2ml deionized water to prepare a mixed solution, the molar concentration of Pt is 0.16mol/L, and the mixed solution is dropwise added into the r-Ti-0.1Si composite carrier and uniformly mixed. Soaking for 12h at room temperature, drying at 80deg.C for 12h, and calcining at 400deg.C in air atmosphere for 4h, wherein Pt mass content is 3%, siO 2 The mass content is 0.97%, and the rest is TiO 2 The catalyst was designated as 3Pt/r-Ti-0.1Si catalyst.
Catalyst reduction activation conditions: reducing gas to pure H 2 (molar purity)>99.9 percent, airspeed of 2000h -1 The temperature rising rate is 5 ℃/min, the reduction temperature is 400 ℃, the pressure is normal pressure, and the reduction time is 4h. The catalyst is used for stirring reaction conditions in a kettle: nitric acid concentration (calculated by hydrogen ion concentration) is 1.0mol/L, uranyl ion concentration is 0.9mol/L, hydrazine concentration is 1.0mol/L, temperature is 60 ℃, stirring speed is 800rpm, and pressure is normal pressure. The reaction results are shown in Table 1.
Example 16
2.0g of the r-TiO prepared in example 1 are weighed out 2 1.73g of ethyl orthosilicate is weighed and dissolved in 5ml of absolute ethyl alcohol to prepare a mixed solution, the molar concentration of Si is 1.66mol/L, and the mixed solution is added dropwise to TiO 2 And mixing them uniformly. Soaking at room temperature for 12h, drying at 80deg.C for 12h, calcining at 400deg.C in air atmosphere for 4h, grinding, tabletting, crushing, and sieving (20-40 mesh) to obtain Ti-Si composite carrier, wherein SiO 2 The mass content is 20%, and is denoted as r-Ti-20Si.
Weigh 2.0g r-Ti-20Si composite support and weigh 0.1642g H 2 PtCl 6 ·6H 2 O is dissolved in 2ml deionized water to prepare a mixed solution, the molar concentration of Pt is 0.16mol/L, and the mixed solution is dripped into the r-Ti-20Si composite carrier and uniformly mixed. Soaking for 12h at room temperature, drying at 80deg.C for 12h, and calcining at 400deg.C in air atmosphere for 4h, wherein Pt mass content is 3%, siO 2 The mass content is 19.4%, and the rest is TiO 2 The catalyst was designated as 3Pt/r-Ti-20Si catalyst.
Catalyst reduction activation conditions: reducing gas to pure H 2 (molar purity)>99.9 percent, airspeed of 2000h -1 The temperature rising rate is 5 ℃/min, the reduction temperature is 400 ℃, the pressure is normal pressure, and the reduction time is 4h. The catalyst is used for stirring reaction conditions in a kettle: nitric acid concentration (calculated by hydrogen ion concentration) is 1.0mol/L, uranyl ion concentration is 0.9mol/L, hydrazine concentration is 1.0mol/L, temperature is 60 ℃, stirring speed is 800rpm, and pressure is normal pressure. The reaction results are shown in Table 1.
Comparative example 17
Taking the r-TiO prepared in example 1 2 Carrier 2.0g, weigh 0.1642g H 2 PtCl 6 ·6H 2 O is dissolved in 2ml deionized water to prepare a mixed solution, the molar concentration of Pt is 0.16mol/L, and r-TiO is prepared 2 The carrier is immersed in the mixed solution and is uniformly mixed. Soaking for 12h at room temperature, drying for 12h at 60 ℃, and roasting for 4h in an air atmosphere at 400 ℃, wherein the mass content of Pt is 3%, which is marked as a 3Pt/Ti catalyst.
Catalyst reduction activation conditions: reducing gas to pure H 2 (molar purity)>99.9 percent, airspeed of 2000h -1 The temperature rising rate is 5 ℃/min, the reduction temperature is 300 ℃, the pressure is normal pressure, and the reduction time is 4h. The catalyst is used for stirring reaction conditions in a kettle: nitric acid concentration (calculated by hydrogen ion concentration) is 1.0mol/L, uranyl ion concentration is 0.9mol/L, hydrazine concentration is 1.0mol/L, temperature is 60 ℃, stirring speed is 800rpm, and pressure is normal pressure. The reaction results are shown in Table 1.
Comparative example 18
Taking SiO 2 Carrier 2.0g, weigh 0.1642g H 2 PtCl 6 ·6H 2 O is dissolved in 2ml deionized water to prepare a mixed solution, the molar concentration of Pt is 0.16mol/L, and SiO is prepared 2 The carrier is immersed in the mixed solution and is uniformly mixed. Soaking for 12h at room temperature, drying for 12h at 60 ℃, and roasting for 4h in an air atmosphere at 400 ℃, wherein the mass content of Pt is 3%, which is marked as a 3Pt/Si catalyst.
Catalyst reduction activation conditions: reducing gas to pure H 2 Purity of>99%, airspeed of 2000h -1 The temperature rising rate is 5 ℃/min, the reduction temperature is 300 ℃, the pressure is normal pressure, and the reduction time is 4h. The catalyst is used for stirring reaction conditions in a kettle: nitric acid concentration (calculated by hydrogen ion concentration) is 1.0mol/L, uranyl ion concentration is 0.9mol/L, hydrazine concentration is 1.0mol/L, temperature is 60 ℃, stirring speed is 800rpm, and pressure is normal pressure. The reaction results are shown in Table 1.
Comparative example 19
Weighing SiO 2 2.0g of carrier, 0.77g of zirconium nitrate was weighed and dissolved in 10ml of water to prepare a mixed solution, the molar concentration of Zr was 0.18mol/L, and SiO was added 2 The carrier is poured into the mixed solution and mixed uniformly. Soaking at room temperature for 12h, drying at 60deg.C for 12h, calcining at 500deg.C in air atmosphere for 4h, grinding, tabletting, crushing, and sieving (20-40 mesh) to obtain Si-Zr composite carrier, wherein ZrO 2 The mass content was 10%, denoted as Si-10Zr.
Weigh 2.0g SiO 2 -10Zr composite carrier, weighing 0.1642g H 2 PtCl 6 ·6H 2 O is dissolved in 2ml deionized water to prepare a mixed solution, the molar concentration of Pt is 0.16mol/L, and SiO is prepared 2 The-10 Zr composite carrier is poured into the mixed solution and is uniformly mixed. Soaking for 12h at room temperature, drying at 60deg.C for 12h, and calcining at 800deg.C under air atmosphere for 4h, wherein Pt mass content is 3%, zrO 2 The mass content is 9.7%, the rest is SiO 2 The catalyst was designated as 3Pt/Si-10Zr catalyst.
Catalyst reduction activation conditions: reducing gas to pure H 2 (molar purity)>99.9 percent, airspeed of 2000h -1 The temperature rising rate is 5 ℃/min, the reduction temperature is 300 ℃, the pressure is normal pressure, and the reduction time is 4h. Catalytic reactionThe agent is used for stirring reaction conditions in a kettle: nitric acid concentration (calculated by hydrogen ion concentration) is 1.0mol/L, uranyl ion concentration is 0.9mol/L, hydrazine concentration is 1.0mol/L, temperature is 60 ℃, stirring speed is 800rpm, and pressure is normal pressure. The reaction results are shown in Table 1.
Comparative example 20
Weighing SiO 2 2.0g of carrier, 1.64g of aluminum nitrate was weighed and dissolved in 10ml of water to prepare a mixed solution, the molar concentration of Al was 0.44mol/L, and SiO was added 2 The carrier is poured into the mixed solution and mixed uniformly. Soaking at room temperature for 12 hr, drying at 60deg.C for 12 hr, calcining at 500deg.C in air atmosphere for 4 hr, grinding, tabletting, crushing, and sieving (20-40 mesh) to obtain Si-Al composite carrier, wherein Al 2 O 3 The mass content is 10%, which is marked as Si-10Al.
Weigh 2.0g of Si-10Al composite carrier, weigh 0.1642g H 2 PtCl 6 ·6H 2 O is dissolved in 2ml deionized water to prepare a mixed solution, the molar concentration of Pt is 0.16mol/L, and the Si-10Al composite carrier is poured into the mixed solution and uniformly mixed. Soaking for 12h at room temperature, drying at 60deg.C for 12h, and calcining at 500 deg.C in air atmosphere for 4h, wherein Pt mass content is 3%, al 2 O 3 The mass content is 9.7%, the rest is SiO 2 The catalyst was designated as 3Pt/Si-10Al catalyst.
Catalyst reduction activation conditions: reducing gas to pure H 2 (molar purity)>99.9 percent, airspeed of 2000h -1 The temperature rising rate is 5 ℃/min, the reduction temperature is 300 ℃, the pressure is normal pressure, and the reduction time is 4h. The catalyst is used for stirring reaction conditions in a kettle: nitric acid concentration (calculated by hydrogen ion concentration) is 1.0mol/L, uranyl ion concentration is 0.9mol/L, hydrazine concentration is 1.0mol/L, temperature is 60 ℃, stirring speed is 800rpm, and pressure is normal pressure. The reaction results are shown in Table 1.
Comparative example 21
Weigh Al 2 O 3 2.0g of carrier, 0.77g of zirconium nitrate was weighed and dissolved in 10ml of water to prepare a mixed solution, the molar concentration of Zr was 0.18mol/L, and Al was added 2 O 3 The carrier is poured into the mixed solution and mixed uniformly. Room temperature impregnation 12h, drying at 60 ℃ for 12h, roasting at 500 ℃ for 4h in air atmosphere, and finally grinding, tabletting, crushing and sieving (20-40 meshes) to obtain the Al-Zr composite carrier, wherein ZrO 2 The mass content is 10%, which is expressed as Al-10Zr.
Weigh 2.0g of Al-10Zr composite carrier and weigh 0.1642g H 2 PtCl 6 ·6H 2 O is dissolved in 2ml deionized water to prepare a mixed solution, the molar concentration of Pt is 0.16mol/L, and the Al-10Zr composite carrier is poured into the mixed solution and uniformly mixed. Soaking for 12h at room temperature, drying at 60deg.C for 12h, and calcining at 800deg.C under air atmosphere for 4h, wherein Pt mass content is 3%, zrO 2 The mass content is 9.7%, the rest is Al 2 O 3 The catalyst was designated as 3Pt/Al-10Zr catalyst.
Catalyst reduction activation conditions: reducing gas to pure H 2 (molar purity)>99.9 percent, airspeed of 2000h -1 The temperature rising rate is 5 ℃/min, the reduction temperature is 300 ℃, the pressure is normal pressure, and the reduction time is 4h. The catalyst is used for stirring reaction conditions in a kettle: nitric acid concentration (calculated by hydrogen ion concentration) is 1.0mol/L, uranyl ion concentration is 0.9mol/L, hydrazine concentration is 1.0mol/L, temperature is 60 ℃, stirring speed is 800rpm, and pressure is normal pressure. The reaction results are shown in Table 1.
Example results analysis:
from the data analysis in Table 1, it can be seen that in TiO 2 On the noble metal catalyst prepared by the composite carrier, in the reaction of preparing U (IV) by hydrazine reduction U (VI) under the acidic condition, the conversion rate of U (VI) is higher than 90 percent. In the 3Pt/Ti-10Si catalyst, the conversion rate of U (VI) can reach 99 percent, and the reaction rate can reach 135.7g U4 g -1 min -1 。
TABLE 1 reactivity of hydrazine to hexavalent uranium (U (VI)) to prepare tetravalent uranium (U (IV)) under acidic conditions on different catalysts
In Table 1, the reaction rate was calculated as the amount of catalyst conversion U (VI) at 40min, the catalyst addition amount in the stirred tank was 1g, and the reaction liquid was 25ml; the catalyst loading in the fixed bed was 20g.
Claims (9)
1. A method for catalyzing hydrazine to reduce uranium by using a composite carrier catalyst is characterized by comprising the following steps of: the catalyst is formed by loading active component metal on a Ti-M composite carrier and comprises the following components in parts by mass: a) Ti in the Ti-M composite carrier is an oxide of titanium, and the Ti accounts for 50-99.9% of the total weight of the Ti-M composite carrier; b) The active component is selected from any one of metals Pt, pd, ru, ir, rh, au, and the active component accounts for 0.001-20% by weight; c) M in the Ti-M composite carrier is selected from SiO 2 、Al 2 O 3 、ZrO 2 One or more than two of the components accounting for 0.001-40 percent.
2. The method according to claim 1, characterized in that: the titanium oxide in the component a) in the catalyst is one or two of rutile titanium dioxide and anatase titanium dioxide, and the content is 70-99%; the component b) is any one of the metals Pt, pd, ru, ir, rh, au, and the content is 0.1-10%; component c) is SiO 2 、ZrO 2 Any one or two of the oxides in the catalyst, and the content is 0.01-20%.
3. The method according to any one of claims 1-2, wherein: the preparation process of the catalyst comprises the following steps:
a）TiO 2 is prepared from
1) Dissolving soluble titanium salt in 6-12mol/L hydrochloric acid to obtain solution A; wherein the concentration of titanium ions is 0.001-10 mol/L;
2) Dissolving alkali into deionized water to prepare a precipitant to obtain a solution B with the concentration of 0.01-10 mol/L;
3) Dropwise adding the solution B into the solution A until the pH value of the mixed solution is 7-10, and then stirring and aging the obtained mixture in a water bath at 25-90 ℃ for 0.5-24 h;
4) Filtering and washing the obtained turbid liquid, and drying a filter cake in air at 50-200 ℃ for 12-48 hours;
5) Roasting the dried solid in an air atmosphere at 200-900 ℃ for 1-8 hours to obtain TiO 2 A carrier;
b) Preparation of Ti-M composite carrier
1) Preparing Ti-M composite carrier by adopting an impregnation method, wherein M is SiO 2 、ZrO 2 One or two of the following components; dissolving one or two of a soluble Si source and a soluble Zr source in deionized water and/or absolute ethyl alcohol to prepare a solution C, wherein the concentration of M is 0.001-10 mol/L;
2) Taking prepared TiO 2 The carrier is used for dripping or pouring the solution C with the required quantity into TiO according to the mass fraction of M 2 In (a) and (b);
3) Impregnating the mixture obtained in the step 2) for 0.5-48 h at room temperature;
4) Drying the mixture obtained in the step 3) for 4-24 hours at 60-120 ℃;
5) Roasting the dried mixture at 300-950 ℃ for 1-8 hours to obtain a Ti-M composite carrier;
c) Preparation of noble metal catalysts
1) Dissolving any one of the Pt, pd, ru, ir, rh, au soluble salts in deionized water to prepare a solution D, wherein the concentration of noble metal ions is 0.001-0.5 mol/L;
2) The noble metal catalyst is prepared by adopting an impregnation method: taking a Ti-M composite carrier, and dripping or pouring a required amount of solution D into the Ti-M composite carrier according to the content of noble metal in the catalyst;
3) Impregnating the mixture obtained in the step 2) for 0.5-48 h at room temperature;
4) Drying the mixture obtained in the step 3) for 4-24 hours at 60-120 ℃;
5) Roasting the dried mixture at 200-500 ℃ for 1-8 hours;
6) The solid obtained in the step 5) is subjected to the reduction and activation process that: reducing gas to H 2 The volume airspeed of the reducing gas is 100-3600h -1 The temperature rising rate from room temperature to reduction temperature is 1-10 ℃/min, the reduction temperature is 200-600 ℃, the pressure is normal pressure, and the reduction time is 1-48h.
4. A method according to claim 3, characterized in that:
TiO 2 the soluble titanium salt in the step 1) in the preparation is one or two of titanium tetrachloride and tetrabutyl titanate;
TiO 2 in the preparation of (2), the alkali is one or more than two of ammonia water, sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate;
TiO 2 in the preparation step 5) of (2) in a flowing or stationary air atmosphere; and heating from room temperature or drying temperature to roasting temperature by adopting temperature programming, wherein the heating rate is 0.5-10 ℃/min.
5. A method according to claim 3, characterized in that:
the Si source in the step 1) of preparing the Ti-M composite carrier is one or two of ethyl orthosilicate and butyl orthosilicate; the Zr source is one or more than two of zirconium nitrate, zirconyl nitrate, zirconium oxychloride and zirconium sulfate.
6. A method according to claim 3, characterized in that:
the soluble salt of Pt, pd, ru, ir, rh, au in the preparation step 1) of the noble metal catalyst is one of nitrate or chloride of corresponding noble metal;
the roasting temperature in the preparation step 5) of the noble metal catalyst is 300-500 ℃, and the roasting time is 1-6 h.
7. The method according to claim 1, characterized in that: the catalyst is used for preparing a tetravalent uranium solution by catalyzing hydrazine to reduce hexavalent uranium in an acidic system.
8. The method according to claim 7, wherein: the acid system is one or more than two of nitric acid, sulfuric acid or perchloric acid systems; the hexavalent uranium is uranyl ions corresponding to acid types in an acid system, and is one or more than two of uranyl nitrate, uranyl sulfate and uranyl perchlorate solutions respectively; the tetravalent uranium is a reduction product of the corresponding hexavalent uranium.
9. The method according to claim 1, characterized in that: the conditions for preparing the tetravalent uranium solution by hydrazine reduction of hexavalent uranium by the catalyst applied to the stirred tank reactor or the fixed bed reactor are as follows: the acid concentration is 0.5-1.0mol/L, the uranyl ion concentration is 0.5-1.3mol/L, the hydrazine concentration is 0.5-2.0mol/L, the reaction temperature is 25-70 ℃, and the reaction pressure is normal pressure.
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