CN114308021A - Method for reducing uranium by hydrazine under catalysis of composite carrier catalyst - Google Patents
Method for reducing uranium by hydrazine under catalysis of composite carrier catalyst Download PDFInfo
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Abstract
The invention relates to a method for reducing uranium by hydrazine under catalysis of a composite carrier catalyst, which mainly realizes preparation of a uranium solution by reducing hexavalent uranium by hydrazine catalysis under an acidic condition and obtains higher yield of uranium. 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) in Ti-M composite carrierThe Ti is titanium oxide, and accounts for 50-99.9%; b) the active component is selected from any one of metal Pt, Pd, Ru, Ir, Rh and Au, and accounts for 0.001-20%; c) m in the Ti-M composite carrier is selected from SiO2、Al2O3、ZrO2One or more than two of the components in the total amount of 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 acid system, the yield of the tetravalent uranium can reach 99%, and the reaction rate can reach 135.7gU4g‑1min‑1。
Description
Technical Field
The invention relates to a method for reducing uranium by hydrazine under the catalysis of a composite carrier catalyst.
Background
Nuclear fuel reprocessing technology is an important segment of the nuclear industry. The method is characterized in that spent fuel (nuclear fuel used in a reactor) is subjected to post-treatment, uranium (U) and plutonium (Pu) are separated and recycled as nuclear fuel for reuse, and high radioactive waste is subjected to geological disposal, so that the method is of great importance to the safe and sustainable development of nuclear energy in China.
The key of the spent fuel reprocessing technology is to realize the separation of uranium, plutonium and other fissile elements. At present, post-processing plants at home and abroad mainly adopt a Purex (Purex) flow, and utilize tributyl phosphate (TBP) to have low extraction capacity on trivalent plutonium, so that the uranium and the plutonium are separated. 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, the tetravalent uranium (U (IV)) is a better reduction stripping agent of the tetravalent plutonium (Pu (IV)), and has the advantages of complete reduction stripping of the 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 reprocessing plants in operation and under construction use hydrazine stabilized U (IV) as a reduction stripping agent, such as UP3 and UP2-800 in France and pilot plant in China.
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 to electrolyze uranyl nitrate (UO)2(NO3)2) The method has the advantages of simple process, no introduction of impurities and the like. However, in the actual production, the conversion rate of hexavalent uranium (U (VI)) in the electrolytic reduction method is low, generally 50-60%, so that the concentration of tetravalent uranium in the product is low. When the catalyst is used as a reducing agent, not only dilution of the plutonium product is caused, but also the load of recycling the uranium product is increased. Hydrogenation reduction method for preparing UO by using high-pressure hydrogen2(NO3)2The solution is reduced into U (IV), which has the advantages of large production capacity, high U (IV) yield and the like. However, the production equipment of the hydrogenation reduction method is complex, and the use of high-pressure hydrogen in a nuclear fuel post-treatment workshop with extremely strong radioactivity is a great safety hazard. Under the action of a catalyst, U (VI) can be reduced into U (IV) by adopting organic reducing agents such as hydrazine and the like, the formula (1) is shown in the specification, the reaction conditions are mild (normal temperature and normal pressure), the preparation process is simple, and the preparation method is a promising U (VI) preparation method.
N2H5 ++3H++2UO2 2+→2U4++N2+4H2O (1)
Bin and the like, platinum black is used as a catalyst, and the process conditions of the reaction for preparing U (IV) by reducing hydrazine U (VI) in a nitric acid system are studied. HNO when the uranium concentration is 0.9mol/L3When 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 and Radioactive chemistry, 2013,35, (1): 24-28). Boltoeva et al examined Pt/SiO2Catalyst in H2SO4、HClO4、HNO3System ofHydrazine reduction U (VI) to prepare the particle size effect of Pt in U (IV). It was found that the U (VI) conversion increased with increasing Pt particle size (Radiochemistry,2007,49, 603- "606). Anan' ev et al examined the performance of the reaction of hydrazine and formic acid to reduce U (VI) to U (IV) in a nitric acid system (Radiochemistry,2001,43, 39-43). At present, the research on the reaction for preparing U (IV) by reducing U (VI) by hydrazine mainly focuses on the study on the kinetics and the process conditions, and the research on the optimization design of the catalyst is less.
At present, some relevant patents are applied to the preparation of tetravalent uranium solutions. Several reported patents are listed below for details:
chinese patent CN201110097474 discloses a name: a preparation method of a tetravalent uranium solution. The patent reports the preparation of u (iv) solution by reduction of u (vi) with an organic reducing agent (hydrazine or carboxylic acids and their derivatives) over Pt, Pd, Rh catalysts. The process and method of catalyst preparation is not described in this patent.
Chinese patent CN201310743451 discloses name: a device 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 low U (VI) conversion rate in a diaphragm-free electrolysis device. In actual production, the effectiveness of the device needs to be further verified.
U (VI) can be reduced to U (IV) by hydrazine under the action of a noble metal catalyst in an acidic system. And the ability of hydrazine reduction U (VI) is modulated through the optimization design of the catalyst, so that the activity of the catalyst and the utilization rate of hydrazine are improved, and the high-efficiency production of U (IV) is hopefully realized under the mild condition.
Disclosure of Invention
One of the technical problems to be solved by the invention is to solve the problem of preparing U (IV) catalyst by reducing U (VI) hydrazine in an acidic 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 present invention is to adopt the method for preparing the catalyst described in the first technical problem. 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 above technical problems to realize the catalytic reaction process for preparing U (IV) by reducing hydrazine U (VI) under an acidic condition.
In order to solve one of the technical problems, the invention adopts the following technical scheme: the method for preparing the noble metal catalyst U (IV) by reducing the hydrazine U (VI) under the acidic condition comprises the following components in parts by mass: a) the titanium oxide accounts for 50-99.9 percent; b) the active component is selected from any one of metal Pt, Pd, Ru, Ir, Rh and Au, and accounts for 0.001-20%; c) selected from SiO2、Al2O3、ZrO2One or more than two of the components in the total amount of 0.001 to 40 percent.
In the scheme, the method is characterized in that: in the catalyst, the component a) is preferably one or two of rutile titanium dioxide or anatase titanium dioxide as titanium oxide, and the preferable content is 89-99%; the component b) is preferably any one of metals of Pt, Pd, Ru and Ir, and the preferred content is 0.1-10%; component c) is preferably SiO2、ZrO2The content of any one or more of the oxides is preferably 0.01 to 10%.
In order to solve the second technical problem, the invention adopts the following technical scheme:
a)TiO2preparation of
1) Dissolving soluble titanium salt in concentrated hydrochloric acid of 6-12mol/L to obtain solution A; wherein the concentration of the titanium ions is 0.001-10 mol/L;
2) dissolving alkali in deionized water to prepare a precipitator 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 h;
5) roasting the dried solid for 1-8 h at 200-900 ℃ in an air atmosphere to obtain TiO2。
b) Preparation of Ti-M composite carrier
1) The Ti-M composite carrier is prepared by an impregnation method, wherein M is one or more than two of Si and Zr. One or more than two of soluble Si source and soluble Zr source are dissolved in deionized water or absolute ethyl alcohol to prepare solution C, and the concentration of M is 0.001-10 mol/L.
2) Taking the prepared TiO2A carrier, according to the mass fraction of M, dropwise adding or pouring the required amount of the solution C into TiO2In (1).
3) Soaking the mixture in the step (2) at room temperature for 0.5-48 h;
4) drying the mixture obtained in the step (3) at the temperature of 60-120 ℃ for 4-24 hours;
5) and roasting the dried mixture at the temperature of 300-950 ℃ for 1-8 h to obtain the Ti-M composite carrier.
c) Preparation of noble metal catalysts
1) Dissolving soluble salt of any one of Pt, Pd, Ru, Ir, Rh and 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 an impregnation method. Taking a Ti-M composite carrier, and dropwise adding 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) soaking the mixture in the step (2) at room temperature for 0.5-48 h;
4) drying the mixture obtained in the step (3) at the temperature of 60-120 ℃ for 4-24 hours;
5) roasting the dried mixture at 200-500 ℃ for 1-8 h;
6) the solid obtained in the step (5) is subjected to reduction activation by the following steps: reducing gas to H2(molar purity)>99.9 percent) and the volume space velocity of the reducing gas is 100-3600h-1The heating rate from room temperature to the reduction temperature is 1-10 ℃/min, the reduction temperature is 200-.
TiO2In the preparation, the alkali in the step 2) is one or more than two of ammonia water, sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate;
TiO2the calcination can be carried out in a flowing or static air atmosphere in the preparation step 5); wherein the temperature is raised from room temperature or drying temperature to roasting temperature by adopting a program, and the temperature raising rate is 0.5-10 ℃/min;
in the preparation step of the Ti-M composite carrier, the Si source in the step 1) is one or two of ethyl orthosilicate and butyl orthosilicate; the Zr source is one or more of zirconium nitrate, zirconyl nitrate, zirconium oxychloride and zirconium sulfate.
Preparing a noble metal catalyst, wherein soluble salts of Pt, Pd, Ru, Ir, Rh and Au in the step 1) are one of nitrates or chlorides of corresponding noble metals;
the roasting temperature in the step 5) of preparing 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 acid system, hydrazine is used as a reducing agent to reduce hexavalent uranium into a tetravalent uranium solution. The conditions of the catalyst applied to a stirred tank reactor or a fixed bed reactor for preparing the uranium solution by reducing hexavalent uranium with hydrazine are as follows: the acid concentration (by 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 property and is beneficial to prolonging the service life of the catalyst.
(2) The catalyst provided by the invention can reduce U (VI) to U (IV) solution by hydrazine under acidic condition. The interaction between the composite carrier and the noble metal in the catalyst improves the conversion rate and the reaction rate of U (VI). In a stirred tank reactor, the conversion of U (VI) can reach 99% within 60 min. And the reaction rate reached 135.7gU4 g-1min-1。
Detailed Description
The technical details of the present invention are described in detail by the following examples. The embodiments are described for further illustrating the technical features of the invention, and are not to be construed as limiting the invention.
Catalyst preparation and Performance evaluation
Example 1
20ml of TiCl are taken4The solution is slowly dripped into 50ml of 10mol/L concentrated hydrochloric acid to prepare a solution A, and the concentration of titanium ions is 2.60 mol/L. 100ml of 10mol/L ammonia water (solution B) is added into the mixed solution A at the flow rate of 1ml/min by using a constant flow pump, and the pH value of the solution after the addition is about 10. The mixed solution is placed in a water bath at 60 ℃ to be continuously stirred and aged for 4 h. Filtering and washing the obtained turbid solution to be neutral, and then drying a filter cake in air at the temperature of 80 ℃ for 24 hours; roasting the dried solid for 4 hours at 500 ℃ in an air atmosphere to obtain rutile type titanium dioxide, r-TiO2。
2.0g of the r-TiO prepared above was weighed2Weighing 0.77g of ethyl orthosilicate, dissolving the ethyl orthosilicate in 10ml of absolute ethyl alcohol to prepare a mixed solution, wherein the concentration of ethyl acetate is 0.37mol/L, and dropwise adding the mixed solution to TiO2Neutralizing and mixing them uniformly. Soaking at room temperature for 12h, drying at 80 deg.C for 12h, calcining at 400 deg.C in air atmosphere for 4h, grinding, tabletting, crushing, and sieving (20-40 mesh) to obtain Ti-Si composite carrier, wherein SiO is2The mass content is 10 percent and is recorded as r-Ti-10 Si.
2.0g of a Ti-10Si composite carrier was weighed, 0.1642g H was weighed2PtCl6·6H2Dissolving the O in 2ml of deionized water to prepare a mixed solution, dropwise adding the Pt with the molar concentration of 0.16mol/L into the Ti-10Si composite carrier, and uniformly mixing. Soaking at room temperature for 12h, drying at 80 deg.C for 12h, and calcining at 400 deg.C in air atmosphere for 4h, wherein Pt content is 3 wt%, and SiO29.7 percent of mass content and the balance of TiO2And is marked as 3Pt/r-Ti-10Si catalyst.
Catalyst reduction activation conditions: reducing the gas to pure H2(molar purity)>99.9 percent) and the space velocity is 2000h-1The heating rate is 5 ℃/min, the reduction temperature is 400 ℃, the pressure is normal pressure, and the reduction time is 4 h. The catalyst is used in a stirred tank under the following reaction conditions: the concentration of nitric acid (by hydrogen ion concentration) is 1.0mol/L, the concentration of uranyl ions is 0.9mol/L, the concentration of hydrazine is 1.0mol/L, the temperature is 60 ℃, the stirring speed is 800rpm, and the pressure is highThe force was normal pressure. The reaction results are shown in Table 1.
Example 2
Taking 10ml of TiCl4The solution is slowly dripped into 20ml of 12mol/L concentrated hydrochloric acid to prepare a solution A, and the concentration of titanium ions is 3.03 mol/L. 50ml of 10mol/L ammonia water (solution B) is added into the mixed solution A at the flow rate of 1ml/min by using a constant flow pump, and the pH value of the solution is about 9 after the addition. The mixed solution is placed in a water bath with the temperature of 30 ℃ to be continuously stirred and aged for 24 hours. Filtering and washing the obtained turbid solution to be neutral, and then drying a filter cake in air at 60 ℃ for 48 hours; roasting the dried solid for 1h at 300 ℃ in an air atmosphere to obtain rutile type titanium dioxide, r1-TiO2。
2.0g of r1-TiO prepared as described above were weighed2Weighing 0.77g of tetraethoxysilane, dissolving the tetraethoxysilane in 10ml of absolute ethyl alcohol to prepare a mixed solution, pouring the mixed solution into gamma-TiO, wherein the concentration of the tetraethoxysilane is 0.37mol/L2Mixing the solution and mixing the solution evenly. Soaking at room temperature for 0.5h, drying at 60 deg.C for 24h, calcining at 300 deg.C in air atmosphere for 1h, grinding, tabletting, crushing, and sieving (20-40 mesh) to obtain Ti-Si composite carrier, wherein SiO is2The mass content is 10 percent and is recorded as r1-Ti-10 Si.
2.0g r1-Ti-10Si composite support was weighed, 0.1031g of PdCl were weighed2Dissolving the Pd in 2ml deionized water and 1ml concentrated hydrochloric acid to prepare a mixed solution, wherein the molar concentration of Pd is 0.19mol/L, dropwise adding the mixed solution into an r1-Ti-10Si composite carrier, and uniformly mixing the carrier. Soaking at room temperature for 1h, drying at 60 deg.C for 4h, and calcining at 300 deg.C in air atmosphere for 1h, wherein the mass content of Pd is 3%, and SiO29.7 percent of mass content and the balance of TiO2And is marked as 3Pd/r1-Ti-10Si catalyst.
Catalyst reduction activation conditions: reducing the gas to pure H2(molar purity)>99.9 percent) and the space velocity is 200h-1The heating rate is 5 ℃/min, the reduction temperature is 200 ℃, the pressure is normal pressure, and the reduction time is 1 h. The catalyst is used in a stirred tank under the following reaction conditions: the concentration of nitric acid (by hydrogen ion concentration) is 0.5mol/L, the concentration of uranyl ions is 0.5mol/L, the concentration of hydrazine is 0.5mol/L, the temperature is 25 ℃, the stirring speed is 800rpm, and the 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 12mol/L concentrated hydrochloric acid to prepare solution A, and the concentration of titanium ions is 0.97 mol/L. 300ml of 1mol/L sodium hydroxide (solution B) was added to the mixed solution A at a flow rate of 1ml/min by a constant flow pump, and the pH of the solution was about 9 after the addition. The mixed solution is placed in a water bath with the temperature of 90 ℃ to be continuously stirred and aged for 0.5 h. Filtering and washing the obtained turbid solution to be neutral, and then drying a filter cake in air at 200 ℃ for 12 hours; roasting the dried solid for 8h at 900 ℃ in an air atmosphere to obtain rutile type titanium dioxide, r2-TiO2。
2.0g of r2-TiO prepared as described above were weighed2Weighing 1.18g of n-butyl silicate, dissolving the n-butyl silicate in 10ml of absolute ethyl alcohol to prepare a mixed solution, pouring the mixed solution into r1-TiO, wherein the concentration of the n-butyl silicate is 0.37mol/L2Mixing the solution and mixing the solution evenly. Soaking at room temperature for 48h, drying at 120 deg.C for 4h, calcining at 950 deg.C in air atmosphere for 1h, grinding, tabletting, crushing, and sieving (20-40 mesh) to obtain Ti-Si composite carrier, wherein SiO is2The mass content is 10 percent and is recorded as r2-Ti-10 Si.
2.0g r2-Ti-10Si composite support was weighed, 0.1672g of RuCl was weighed3·3H2Dissolving the compound O in 2ml of deionized water to prepare a mixed solution, dripping the mixed solution into an r2-Ti-10Si composite carrier with the molar concentration of Ru being 0.40mol/L, and uniformly mixing the mixed solution. Soaking at room temperature for 48h, drying at 120 deg.C for 24h, and calcining at 500 deg.C in air atmosphere for 6h, wherein the mass content of Ru is 3%, and SiO29.7 percent of mass content and the balance of TiO2And is marked as 3Ru/r2-Ti-10Si catalyst.
Catalyst reduction activation conditions: reducing the gas to pure H2(molar purity)>99.9%) at 3600h-1The heating rate is 5 ℃/min, the reduction temperature is 600 ℃, the pressure is normal pressure, and the reduction time is 4 h. The catalyst is used in a stirred tank under the following reaction conditions: the concentration of nitric acid (by hydrogen ion concentration) is 1.0mol/L, the concentration of uranyl ions is 1.3mol/L, the concentration of hydrazine 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 carrier prepared in example 1 was weighed, and 0.1660g H was weighed2IrCl6·6H2Dissolving the Ir in 2ml of deionized water to prepare a mixed solution, dripping the mixed solution into the r-Ti-10Si composite carrier with the molar concentration of the Ir of 0.19mol/L, and uniformly mixing the carrier. Soaking at room temperature for 12h, drying at 60 deg.C for 12h, and calcining at 400 deg.C in air atmosphere for 4h, wherein Ir content is 3 wt%, and SiO29.7 percent of mass content and the balance of TiO2And is marked as a 3Ir/r-Ti-10Si catalyst.
Catalyst reduction activation conditions: reducing the gas to pure H2(molar purity)>99.9 percent) and the space velocity is 2000h-1The heating rate is 5 ℃/min, the reduction temperature is 400 ℃, the pressure is normal pressure, and the reduction time is 4 h. The catalyst is used in a stirred tank under the following reaction conditions: the concentration of nitric acid (by hydrogen ion concentration) is 0.8mol/L, the concentration of uranyl ions is 0.9mol/L, the 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 carrier prepared in example 1 was weighed, 0.1258g of RhCl was weighed3Dissolving the mixed solution in 2ml of deionized water to prepare a mixed solution, wherein the molar concentration of Rh is 0.30mol/L, dropwise adding the mixed solution into an r-Ti-10Si composite carrier, and uniformly mixing the carrier. Soaking at room temperature for 12h, drying at 60 deg.C for 12h, and calcining at 400 deg.C in air atmosphere for 4h, wherein Rh content is 3%, and SiO29.7 percent of mass content and the balance of TiO2And is marked as 3Rh/r-Ti-10Si catalyst.
Catalyst reduction activation conditions: reducing the gas to pure H2(molar purity)>99.9 percent) and the space velocity is 2000h-1The heating rate is 5 ℃/min, the reduction temperature is 400 ℃, the pressure is normal pressure, and the reduction time is 4 h. The catalyst is used in a stirred tank under the following reaction conditions: the concentration of nitric acid (by hydrogen ion concentration) is 1.0mol/L, the concentration of uranyl ions is 0.9mol/L, the concentration of hydrazine 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 6
Weighing machine2.0g of the r-Ti-10Si composite carrier prepared in example 1, 0.1293g of HAuCl was weighed4·4H2Dissolving the mixed solution into 2ml of deionized water to prepare a mixed solution, dropwise adding the mixed solution into the r-Ti-10Si composite carrier with the Au molar concentration of 0.19mol/L, and uniformly mixing. Soaking at room temperature for 12h, drying at 60 deg.C for 12h, and calcining at 400 deg.C in air atmosphere for 4h, wherein Au content is 3%, and SiO29.7 percent of mass content and the balance of TiO2And is marked as a 3Au/r-Ti-10Si catalyst.
Catalyst reduction activation conditions: reducing the gas to pure H2(molar purity)>99.9 percent) and the space velocity is 2000h-1The heating rate is 5 ℃/min, the reduction temperature is 400 ℃, the pressure is normal pressure, and the reduction time is 4 h. The catalyst is used in a stirred tank under the following reaction conditions: the concentration of nitric acid (by hydrogen ion concentration) is 1.0mol/L, the concentration of uranyl ions is 0.9mol/L, the concentration of hydrazine 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 7
2.0g of the r-Ti-10Si composite carrier prepared in example 1 was weighed, 0.0265g H was weighed2PtCl6·6H2Dissolving the Pt in 2ml of deionized water to prepare a mixed solution, dropwise adding the Pt with the molar concentration of 0.025mol/L into the Ti-10Si composite carrier, and uniformly mixing. Soaking at room temperature for 12h, drying at 60 deg.C for 12h, and calcining at 400 deg.C in air atmosphere for 4h, wherein the Pt content is 0.5 wt%, and SiO29.95 percent of mass content and the balance of TiO2And is marked as 0.5Pt/r-Ti-10Si catalyst.
Catalyst reduction activation conditions: reducing the gas to pure H2(molar purity)>99.9 percent) and the space velocity is 2000h-1The heating rate is 5 ℃/min, the reduction temperature is 400 ℃, the pressure is normal pressure, and the reduction time is 4 h. The catalyst is used in a stirred tank under the following reaction conditions: the concentration of nitric acid (by hydrogen ion concentration) is 1.0mol/L, the concentration of uranyl ions is 0.9mol/L, the concentration of hydrazine 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 8
2.0g of r-Ti-10Si composite support, weighing 0.5902g H2PtCl6·6H2Dissolving the Pt in 2ml of deionized water to prepare a mixed solution, dropwise adding the Pt with the molar concentration of 0.57mol/L into the Ti-10Si composite carrier, and uniformly mixing. Soaking at room temperature for 12h, drying at 60 deg.C for 12h, and calcining at 400 deg.C in air atmosphere for 4h, wherein Pt content is 10 wt%, and SiO29 percent of mass content and the balance of TiO2And is marked as 10Pt/r-Ti-10Si catalyst.
Catalyst reduction activation conditions: reducing the gas to pure H2(molar purity)>99.9 percent) and the space velocity is 2000h-1The heating rate is 5 ℃/min, the reduction temperature is 400 ℃, the pressure is normal pressure, and the reduction time is 4 h. The catalyst is used in a stirred tank under the following reaction conditions: the concentration of nitric acid (by hydrogen ion concentration) is 1.0mol/L, the concentration of uranyl ions is 0.9mol/L, the concentration of hydrazine 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 9
2.0g of the r-TiO prepared in example 1 were weighed2Weighing 0.77g of zirconium nitrate and dissolving the zirconium nitrate in 10ml of water to prepare a mixed solution, wherein the molar concentration of Zr is 0.18mol/L, and preparing the prepared TiO2Pouring into the mixed solution, and uniformly mixing. Soaking at room temperature for 12h, drying at 60 deg.C for 12h, calcining at 500 deg.C in air atmosphere for 4h, grinding, tabletting, crushing, and sieving (20-40 mesh) to obtain r-Ti-Zr composite carrier, wherein ZrO is2The mass content is 10 percent and is recorded as r-Ti-10 Zr.
2.0g r-Ti-10Zr composite support was weighed, 0.1642g H2PtCl6·6H2Dissolving the carrier in 2ml of deionized water to prepare a mixed solution, wherein the molar concentration of Pt is 0.16mol/L, pouring the r-Ti-10Zr composite carrier into the mixed solution, and uniformly mixing. Soaking at room temperature for 12h, drying at 60 deg.C for 12h, and calcining at 800 deg.C in air atmosphere for 4h, wherein Pt content is 3 wt%, and ZrO is added29.7 percent of mass content and the balance of TiO2And is recorded as a 3Pt/r-Ti-10Zr catalyst.
Catalyst reduction activation conditions: reducing the gas to pure H2(molar purity)>99.9%) and space velocity of2000h-1The heating rate is 5 ℃/min, the reduction temperature is 300 ℃, the pressure is normal pressure, and the reduction time is 4 h. The catalyst is used in a stirred tank under the following reaction conditions: the concentration of nitric acid (by hydrogen ion concentration) is 1.0mol/L, the concentration of uranyl ions is 0.9mol/L, the concentration of hydrazine 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 10
2.0g of the r-TiO prepared in example 1 were weighed21.64g 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 the prepared TiO was added2Pouring into the mixed solution, and uniformly mixing. Soaking at room temperature for 12h, drying at 60 deg.C for 12h, calcining at 500 deg.C in air atmosphere for 4h, grinding, tabletting, crushing, and sieving (20-40 mesh) to obtain r-Ti-Al composite carrier, wherein Al is2O3The mass content is 10 percent and is recorded as r-Ti-10 Al.
2.0g r-Ti-10Al composite carrier was weighed, 0.1642g H2PtCl6·6H2Dissolving the carrier in 2ml of deionized water to prepare a mixed solution, wherein the molar concentration of Pt is 0.16mol/L, pouring the r-Ti-10Al composite carrier into the mixed solution, and uniformly mixing. Soaking at room temperature for 12h, drying at 60 deg.C for 12h, and calcining at 500 deg.C in air atmosphere for 4h, wherein the Pt content is 3% by mass, and Al2O39.7 percent of mass content and the balance of TiO2And is marked as a 3Pt/r-Ti-10Al catalyst.
Catalyst reduction activation conditions: reducing the gas to pure H2(molar purity)>99.9 percent) and the space velocity is 2000h-1The heating rate is 5 ℃/min, the reduction temperature is 300 ℃, the pressure is normal pressure, and the reduction time is 4 h. The catalyst is used in a stirred tank under the following reaction conditions: the concentration of nitric acid (by hydrogen ion concentration) is 1.0mol/L, the concentration of uranyl ions is 0.9mol/L, the concentration of hydrazine 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 11
20ml of TiCl are taken4The solution is slowly dripped into 50ml of 12mol/L concentrated hydrochloric acid to prepare a solution A, and the concentration of titanium ions is 2.60 mol/L. And adding 100ml of 10mol/L ammonia water (solution B) into the mixed solution A at the flow rate of 1ml/min by using a constant flow pump, placing the mixed solution in a water bath at 70 ℃ for continuous stirring, and aging for 12 hours after dropwise addition. Filtering and washing the obtained turbid solution to be neutral, and then drying a filter cake in air at the temperature of 80 ℃ for 12 hours; roasting the dried solid for 4 hours at 300 ℃ in an air atmosphere to obtain anatase type titanium dioxide, A-TiO2。
2.0g of the A-TiO prepared above was weighed2Weighing 0.77g of tetraethoxysilane, dissolving the tetraethoxysilane in 10ml of absolute ethyl alcohol to prepare a mixed solution, wherein the concentration of the tetraethoxysilane is 0.37mol/L, and preparing TiO2Pouring into the mixed solution, and uniformly mixing. Soaking at room temperature for 12h, drying at 60 deg.C for 12h, calcining at 400 deg.C in air atmosphere for 4h, grinding, tabletting, crushing, and sieving (20-40 mesh) to obtain Ti-Si composite carrier, wherein SiO is2The mass content is 10 percent and is marked as Ti-A-10 Si.
2.0g of a Ti-A-10Si composite carrier was weighed, 0.1642g H was weighed2PtCl6·6H2Dissolving the Ti-A-10Si composite carrier in 2ml of deionized water to prepare a mixed solution, wherein the molar concentration of Pt is 0.16mol/L, pouring the Ti-A-10Si composite carrier sample into the mixed solution, and uniformly mixing. Soaking at room temperature for 12h, drying at 60 deg.C for 12h, and calcining at 400 deg.C in air atmosphere for 4h, wherein Pt content is 3 wt%, and SiO29.7 percent of mass content and the balance of TiO2And is marked as a 3Pt/Ti-A-10Si catalyst.
Catalyst reduction activation conditions: reducing the gas to pure H2(molar purity)>99.9 percent) and the space velocity is 2000h-1The heating rate is 5 ℃/min, the reduction temperature is 300 ℃, the pressure is normal pressure, and the reduction time is 4 h. The catalyst is used in a stirred tank under the following reaction conditions: the concentration of nitric acid (by hydrogen ion concentration) is 1.0mol/L, the concentration of uranyl ions is 0.9mol/L, the concentration of hydrazine 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 which had been subjected to reduction activation in example 1 was taken. The catalyst is used in a stirred tank under the following reaction conditions: the sulfuric acid concentration is 0.5mol/L (hydrogen ion concentration 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 13
The 3Pt/r-Ti-10Si catalyst which had been subjected to reduction activation in example 1 was taken. The catalyst is used in a stirred tank under the following reaction conditions: the perchloric acid concentration is 1.0mol/L (hydrogen ion concentration 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 14
The 3Pt/r-Ti-10Si catalyst which had been subjected to reduction activation in example 1 was taken. Reaction conditions in a fixed bed: the concentration of nitric acid (by hydrogen ion concentration) is 1.0mol/L, the concentration of uranyl ions is 0.9mol/L, the concentration of hydrazine is 1.0mol/L, the temperature is 60 ℃, and the liquid space velocity is 0.3h-1The pressure is normal pressure. The reaction results are shown in Table 1.
Example 15
2.0g of the r-TiO prepared in example 1 were weighed2Weighing 0.0070g of tetraethoxysilane, dissolving the tetraethoxysilane in 2ml of absolute ethyl alcohol to prepare a mixed solution, dropwise adding the mixed solution to TiO, wherein the molar concentration of Si is 0.016mol/L2Neutralizing and mixing them uniformly. Soaking at room temperature for 12h, drying at 80 deg.C for 12h, calcining at 400 deg.C in air atmosphere for 4h, grinding, tabletting, crushing, and sieving (20-40 mesh) to obtain Ti-Si composite carrier, wherein SiO is2The mass content is 0.1 percent and is recorded as r-Ti-0.1 Si.
2.0g r-Ti-0.1Si composite support was weighed, 0.1642g H2PtCl6·6H2Dissolving the O in 2ml of deionized water to prepare a mixed solution, dropwise adding the Pt with the molar concentration of 0.16mol/L into the r-Ti-0.1Si composite carrier, and uniformly mixing. Soaking at room temperature for 12h, drying at 80 deg.C for 12h, and calcining at 400 deg.C in air atmosphere for 4h, wherein Pt content is 3 wt%, and SiO2The mass content is 0.97 percent, and the balance is TiO2And is marked as 3Pt/r-Ti-0.1Si catalyst.
Catalyst reduction activation conditions: reducing the gas to pure H2(molar purity)>99.9％)，Space velocity of 2000h-1The heating rate is 5 ℃/min, the reduction temperature is 400 ℃, the pressure is normal pressure, and the reduction time is 4 h. The catalyst is used in a stirred tank under the following reaction conditions: the concentration of nitric acid (by hydrogen ion concentration) is 1.0mol/L, the concentration of uranyl ions is 0.9mol/L, the concentration of hydrazine 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 16
2.0g of the r-TiO prepared in example 1 were weighed2Weighing 1.73g of tetraethoxysilane, dissolving the tetraethoxysilane in 5ml of absolute ethyl alcohol to prepare a mixed solution, dropwise adding the mixed solution to TiO, wherein the molar concentration of Si is 1.66mol/L2Neutralizing and mixing them uniformly. Soaking at room temperature for 12h, drying at 80 deg.C for 12h, calcining at 400 deg.C in air atmosphere for 4h, grinding, tabletting, crushing, and sieving (20-40 mesh) to obtain Ti-Si composite carrier, wherein SiO is2The mass content is 20 percent and is recorded as r-Ti-20 Si.
2.0g r-Ti-20Si composite carrier was weighed, 0.1642g H2PtCl6·6H2Dissolving the O in 2ml of deionized water to prepare a mixed solution, dropwise adding the Pt with the molar concentration of 0.16mol/L into the r-Ti-20Si composite carrier, and uniformly mixing. Soaking at room temperature for 12h, drying at 80 deg.C for 12h, and calcining at 400 deg.C in air atmosphere for 4h, wherein Pt content is 3 wt%, and SiO219.4 percent of mass content and the balance of TiO2And is marked as 3Pt/r-Ti-20Si catalyst.
Catalyst reduction activation conditions: reducing the gas to pure H2(molar purity)>99.9 percent) and the space velocity is 2000h-1The heating rate is 5 ℃/min, the reduction temperature is 400 ℃, the pressure is normal pressure, and the reduction time is 4 h. The catalyst is used in a stirred tank under the following reaction conditions: the concentration of nitric acid (by hydrogen ion concentration) is 1.0mol/L, the concentration of uranyl ions is 0.9mol/L, the concentration of hydrazine 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.
Comparative example 17
Taking the r-TiO prepared in example 122.0g of support weighed 0.1642g H2PtCl6·6H2Dissolving the O in 2ml deionized water to prepare a mixed solutionLiquid, the molar concentration of Pt is 0.16mol/L, and r-TiO2The carrier is immersed in the mixed solution and mixed uniformly. Dipping for 12h at room temperature, drying for 12h at 60 ℃, and roasting for 4h at 400 ℃ in an air atmosphere, wherein the mass content of Pt is 3 percent, and the catalyst is marked as 3Pt/Ti catalyst.
Catalyst reduction activation conditions: reducing the gas to pure H2(molar purity)>99.9 percent) and the space velocity is 2000h-1The heating rate is 5 ℃/min, the reduction temperature is 300 ℃, the pressure is normal pressure, and the reduction time is 4 h. The catalyst is used in a stirred tank under the following reaction conditions: the concentration of nitric acid (by hydrogen ion concentration) is 1.0mol/L, the concentration of uranyl ions is 0.9mol/L, the concentration of hydrazine 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.
Comparative example 18
Taking SiO22.0g of support weighed 0.1642g H2PtCl6·6H2Dissolving O in 2ml deionized water to prepare a mixed solution, wherein the molar concentration of Pt is 0.16mol/L, and dissolving SiO in the mixed solution2The carrier is immersed in the mixed solution and mixed uniformly. Dipping for 12h at room temperature, drying for 12h at 60 ℃, and roasting for 4h at 400 ℃ in an air atmosphere, wherein the mass content of Pt is 3 percent, and the catalyst is marked as 3Pt/Si catalyst.
Catalyst reduction activation conditions: reducing the gas to pure H2Purity of>99 percent and the airspeed of 2000h-1The heating rate is 5 ℃/min, the reduction temperature is 300 ℃, the pressure is normal pressure, and the reduction time is 4 h. The catalyst is used in a stirred tank under the following reaction conditions: the concentration of nitric acid (by hydrogen ion concentration) is 1.0mol/L, the concentration of uranyl ions is 0.9mol/L, the concentration of hydrazine 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.
Comparative example 19
Weighing SiO22.0g 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, SiO2The carrier was poured into the above mixed solution and mixed well. Soaking at room temperature for 12h, drying at 60 deg.C for 12h, calcining at 500 deg.C in air atmosphere for 4h, grinding, tabletting, and crushingSieving (20-40 mesh) to obtain Si-Zr composite carrier, wherein ZrO2The mass content was 10%, and it was designated as Si-10 Zr.
Weigh 2.0g of SiO2-10Zr composite support, weighed 0.1642g H2PtCl6·6H2Dissolving O in 2ml deionized water to prepare a mixed solution, wherein the molar concentration of Pt is 0.16mol/L, and dissolving SiO in the mixed solution2Pouring the-10 Zr composite carrier into the mixed solution, and uniformly mixing. Soaking at room temperature for 12h, drying at 60 deg.C for 12h, and calcining at 800 deg.C in air atmosphere for 4h, wherein Pt content is 3 wt%, and ZrO is added29.7 percent of mass content and the balance of SiO2And is recorded as a 3Pt/Si-10Zr catalyst.
Catalyst reduction activation conditions: reducing the gas to pure H2(molar purity)>99.9 percent) and the space velocity is 2000h-1The heating rate is 5 ℃/min, the reduction temperature is 300 ℃, the pressure is normal pressure, and the reduction time is 4 h. The catalyst is used in a stirred tank under the following reaction conditions: the concentration of nitric acid (by hydrogen ion concentration) is 1.0mol/L, the concentration of uranyl ions is 0.9mol/L, the concentration of hydrazine 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.
Comparative example 20
Weighing SiO22.0g 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, SiO was added2The carrier was poured into the above mixed solution and mixed well. Soaking at room temperature for 12h, drying at 60 deg.C for 12h, calcining at 500 deg.C in air atmosphere for 4h, grinding, tabletting, crushing, and sieving (20-40 mesh) to obtain Si-Al composite carrier, wherein Al is2O3The mass content is 10%, and is marked as Si-10 Al.
2.0g of Si-10Al composite carrier was weighed, 0.1642g H was weighed2PtCl6·6H2Dissolving the O in 2ml of deionized water to prepare a mixed solution, wherein the molar concentration of Pt is 0.16mol/L, pouring the Si-10Al composite carrier into the mixed solution, and uniformly mixing. Soaking at room temperature for 12h, drying at 60 deg.C for 12h, and calcining at 500 deg.C in air atmosphere for 4h, wherein the Pt content is 3% by mass, and Al2O3The mass content is 9.7% and the balance of SiO2And is marked as a 3Pt/Si-10Al catalyst.
Catalyst reduction activation conditions: reducing the gas to pure H2(molar purity)>99.9 percent) and the space velocity is 2000h-1The heating rate is 5 ℃/min, the reduction temperature is 300 ℃, the pressure is normal pressure, and the reduction time is 4 h. The catalyst is used in a stirred tank under the following reaction conditions: the concentration of nitric acid (by hydrogen ion concentration) is 1.0mol/L, the concentration of uranyl ions is 0.9mol/L, the concentration of hydrazine 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.
Comparative example 21
Weighing Al2O32.0g 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 added2O3The carrier was poured into the above mixed solution and mixed well. Soaking at room temperature for 12h, drying at 60 deg.C for 12h, calcining at 500 deg.C in air atmosphere for 4h, grinding, tabletting, crushing, and sieving (20-40 mesh) to obtain Al-Zr composite carrier, wherein ZrO is2The mass content was 10%, and it was recorded as Al-10 Zr.
2.0g of Al-10Zr composite carrier was weighed, 0.1642g H was weighed2PtCl6·6H2Dissolving the O in 2ml of deionized water to prepare a mixed solution, wherein the molar concentration of Pt is 0.16mol/L, pouring the Al-10Zr composite carrier into the mixed solution, and uniformly mixing. Soaking at room temperature for 12h, drying at 60 deg.C for 12h, and calcining at 800 deg.C in air atmosphere for 4h, wherein Pt content is 3 wt%, and ZrO is added29.7 percent of mass content and the balance of Al2O3And is recorded as a 3Pt/Al-10Zr catalyst.
Catalyst reduction activation conditions: reducing the gas to pure H2(molar purity)>99.9 percent) and the space velocity is 2000h-1The heating rate is 5 ℃/min, the reduction temperature is 300 ℃, the pressure is normal pressure, and the reduction time is 4 h. The catalyst is used in a stirred tank under the following reaction conditions: the concentration of nitric acid (by hydrogen ion concentration) is 1.0mol/L, the concentration of uranyl ions is 0.9mol/L, the concentration of hydrazine 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 analysis of results:
from the data analysis in Table 1, it can be seen that in TiO2In the reaction of preparing U (IV) by hydrazine reduction on a noble metal catalyst prepared by a composite carrier under an 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 reaches 135.7gU4 g-1min-1。
TABLE 1 reactivity of hydrazine reduction of hexavalent uranium (U (VI)) to tetravalent uranium (U (IV)) on different catalysts under acidic conditions
In Table 1, the reaction rate is calculated by the amount of the catalyst converted U (VI) at 40min, the amount of the catalyst added in the stirred tank is 1g, and the amount of the reaction feed liquid is 25 ml; the catalyst loading in the fixed bed was 20 g.
Claims (9)
1. A method for reducing uranium by hydrazine under catalysis of a composite carrier catalyst is characterized by comprising the following steps: 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 accounts for 50-99.9%; b) the active component is selected from any one of metal Pt, Pd, Ru, Ir, Rh and Au, and accounts for 0.001-20%; c) m in the Ti-M composite carrier is selected from SiO2、Al2O3、ZrO2One or more than two of the components in the total amount of 0.001 to 40 percent.
2. The method of claim 1, wherein: in the catalyst, the component a) is preferably one or two of rutile titanium dioxide or anatase titanium dioxide as titanium oxide, and the preferable content is 70-99%; component b) is preferably metallic Pt,Any one of Pd, Ru and Ir, preferably the content is 0.1-10%; component c) is preferably SiO2、ZrO2The content of any one or more of the oxides is preferably 0.01 to 20%.
3. The method according to any one of claims 1 to 2, wherein: the preparation process of the catalyst comprises the following steps:
a)TiO2preparation of
1) Dissolving soluble titanium salt in 6-12mol/L hydrochloric acid to obtain a solution A; wherein the concentration of the titanium ions is 0.001-10 mol/L;
2) dissolving alkali in deionized water to prepare a precipitator 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 h;
5) roasting the dried solid for 1-8 h at 200-900 ℃ in an air atmosphere to obtain TiO2A carrier;
b) preparation of Ti-M composite carrier
1) Preparing a Ti-M composite carrier by adopting an impregnation method, wherein M is one or more than two of Si and Zr; dissolving one or more than two of soluble Si source and soluble Zr source in deionized water and/or absolute ethyl alcohol to prepare solution C, wherein the concentration of M is 0.001-10 mol/L;
2) taking the prepared TiO2A carrier, according to the mass fraction of M, dropwise adding or pouring the required amount of the solution C into TiO2Performing the following steps;
3) soaking the mixture in the step (2) at room temperature for 0.5-48 h;
4) drying the mixture obtained in the step (3) at the temperature of 60-120 ℃ for 4-24 hours;
5) roasting the dried mixture at the temperature of 300-950 ℃ for 1-8 h to obtain a Ti-M composite carrier;
c) preparation of noble metal catalysts
1) Dissolving soluble salt of any one of Pt, Pd, Ru, Ir, Rh and Au in deionized water to prepare solution D, wherein the concentration of noble metal ions is 0.001-0.5 mol/L;
2) preparing a noble metal catalyst by adopting an impregnation method: taking a Ti-M composite carrier, and dropwise adding 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) soaking the mixture in the step (2) at room temperature for 0.5-48 h;
4) drying the mixture obtained in the step (3) at the temperature of 60-120 ℃ for 4-24 hours;
5) roasting the dried mixture at 200-500 ℃ for 1-8 h;
6) the solid obtained in the step (5) is subjected to reduction activation by the following steps: reducing gas to H2(molar purity)>99.9 percent) and the volume space velocity of the reducing gas is 100-3600h-1The heating rate from room temperature to the reduction temperature is 1-10 ℃/min, the reduction temperature is 200-.
4. The method of claim 3, wherein:
TiO2in the preparation, the soluble titanium salt in the step 1) is one or two of titanium tetrachloride and tetrabutyl titanate;
TiO2in the preparation, the alkali in the step 2) is one or more than two of ammonia water, sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate;
TiO2the calcination can be carried out in a flowing or static air atmosphere in the preparation step 5); wherein the temperature is raised from room temperature or drying temperature to roasting temperature by adopting a temperature programming, and the temperature raising rate is 0.5-10 ℃/min.
5. The method of claim 3, wherein:
in the preparation step of the Ti-M composite carrier, the Si source in the step 1) is one or two of ethyl orthosilicate and butyl orthosilicate; the Zr source is one or more of zirconium nitrate, zirconyl nitrate, zirconium oxychloride and zirconium sulfate.
6. The method of claim 3, wherein:
preparing a noble metal catalyst, wherein soluble salts of Pt, Pd, Ru, Ir, Rh and Au in the step 1) are one of nitrates or chlorides of corresponding noble metals;
the roasting temperature in the step 5) of preparing the noble metal catalyst is 300-500 ℃, and the roasting time is 1-6 h.
7. The method according to claims 1-6, characterized in that: the catalyst is used for catalyzing hydrazine to reduce hexavalent uranium in an acid system to prepare a tetravalent uranium solution.
8. The method according to claims 1-7, characterized in that: 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 solution, uranyl sulfate solution and uranyl perchlorate solution; the tetravalent uranium is the reduction product of the corresponding hexavalent uranium.
9. The method according to any one of claims 1 to 8, wherein: the conditions of the catalyst applied to a stirred tank reactor or a fixed bed reactor for preparing the uranium solution by reducing hexavalent uranium with hydrazine are as follows: the acid concentration (by 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.
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| US20030008145A1 (en) * | 2001-06-29 | 2003-01-09 | Goldstein Avery N. | Metal nanocrystals and synthesis thereof |
| CN102658165A (en) * | 2012-04-06 | 2012-09-12 | 华东理工大学 | Catalyst for preparing ethanol by acetic acid gas phase hydrogenation and preparation method thereof |
| RU2015157473A (en) * | 2015-12-31 | 2017-07-05 | Федеральное Государственное Унитарное Предприятие "Горно - Химический Комбинат" (Фгуп "Гхк") | METHOD FOR PRODUCING MIXED URANIUM AND PLUTONIUM OXIDES |
| CN110052266A (en) * | 2019-04-30 | 2019-07-26 | 天津大学 | A kind of phthalic acid ester hydrogenation catalyst and the preparation method and application thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US20030008145A1 (en) * | 2001-06-29 | 2003-01-09 | Goldstein Avery N. | Metal nanocrystals and synthesis thereof |
| CN102658165A (en) * | 2012-04-06 | 2012-09-12 | 华东理工大学 | Catalyst for preparing ethanol by acetic acid gas phase hydrogenation and preparation method thereof |
| RU2015157473A (en) * | 2015-12-31 | 2017-07-05 | Федеральное Государственное Унитарное Предприятие "Горно - Химический Комбинат" (Фгуп "Гхк") | METHOD FOR PRODUCING MIXED URANIUM AND PLUTONIUM OXIDES |
| CN110052266A (en) * | 2019-04-30 | 2019-07-26 | 天津大学 | A kind of phthalic acid ester hydrogenation catalyst and the preparation method and application thereof |
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