A nano-octahedral cerium oxide supported palladium catalyst, a preparation method and application thereof

Abstract

The application provides a nano-octahedral cerium oxide supported palladium catalyst and a preparation method and application thereof, mainly relates to the technical field of catalysts, and comprises a carrier, a supported active metal and a silane coating layer; the carrier is nano-octahedral cerium oxide (CeO2), and the supported active metal is an alloy formed by Pd and other noble metals. By adding other noble metals to form a nano-alloy with palladium, the nano-alloy has good low-temperature oxidation performance on tritium gas (T2). The water resistance of the catalyst can be improved by modifying the silane layer.

Description

TECHNICAL FIELD

[0001] The present application mainly relates to the technical field of metal catalyst, in particular to a nano-octahedral cerium oxide supported palladium catalyst and a preparation method and application thereof. BACKGROUND

[0002] Tritium is a kind of beta radioactive gas, with a physical half-life of 12.3a, an average energy of 5.7keV and a maximum energy of only 18.6keV. Since tritium can enter the human body, it will cause continuous radiation to the human body, which can cause various injuries to the human body, such as cell damage, DNA damage and mutation, and increase the risk of cancer; cause damage to the reproductive system, leading to decreased fertility or genetic mutation; cause damage to internal organs, and long-term exposure to high concentrations of tritium may cause damage to internal organs such as the digestive system, liver and kidney. At present, for the removal of high-concentration tritium in gas, the method of catalytic oxidation is used. However, the existing catalyst has low activity and needs to be used at a temperature higher than 100 DEG C to meet the removal requirements of tritium. SUMMARY

[0003] The present application aims to provide a nano-octahedral cerium oxide supported palladium catalyst and a preparation method thereof, which can efficiently remove tritium gas (T2) at room temperature.

[0004] The present application discloses a nano-octahedral cerium oxide supported palladium catalyst, which comprises a carrier, a supported active metal and a silicon dioxide surface layer; the carrier is nano-octahedral cerium oxide, and the supported active metal is an alloy formed by single metal Pd and other noble metals.

[0005] The nano cerium oxide with octahedral morphology can better disperse the noble metal alloy.

[0006] The use of single metal Pd and other noble metals to form a nano alloy has good room temperature oxidation performance for T2.

[0007] Further, the nano-octahedral cerium oxide is synthesized by an induced hydrothermal method.

[0008] The nano-octahedral CeO2 synthesized by the induced hydrothermal method mainly exposes the (111) crystal plane of CeO2, has excellent room temperature oxidation and reduction performance, and excellent oxygen storage and release capacity.

[0009] Further, the supported active metal is a highly dispersed noble metal Pd and one or more of Pt, Rh, Au, Ru and Ir to form a nano alloy.

[0010] Further, the mass of the nano-octahedral cerium oxide supported catalyst is 100%, and the content of the supported noble metal is 0.5% to 5.0% by mass.

[0011] Further, the mass of the nano-octahedral cerium oxide supported catalyst is 100% by mass, wherein the content of the silica surface layer is 0.05% to 3.0%.

[0012] A second object of the present application is to protect a method for preparing a nano-octahedral cerium oxide supported palladium catalyst, comprising the following steps:

[0013] S1. configuring a precursor solution and a salt solution;

[0014] S2. mixing and stirring the precursor solution and the salt solution, then aging the mixed solution, and then performing a hydrothermal reaction at high temperature, washing, filtering, and drying the catalyst overnight to obtain a solid;

[0015] S3. calcining the solid prepared in step S2 to obtain nano-octahedral cerium oxide;

[0016] S4. gradually adding a noble metal solution to the nano-octahedral cerium oxide carrier prepared in step S3 to perform a reaction and stir uniformly; drying the catalyst after the reaction overnight, and then performing a hydrogen high-temperature reduction to obtain a nano-octahedral cerium oxide supported palladium catalyst without a surface SiO2.

[0017] S5. placing the nano-octahedral cerium oxide supported palladium catalyst without a surface SiO2 obtained in S4 into an alcohol solution containing a silicone reagent to perform a reaction and stir uniformly; drying the catalyst after the reaction overnight, and then calcining to obtain a nano-octahedral cerium oxide supported palladium catalyst with a SiO2 surface layer.

[0018] Further, the method for preparing the precursor solution is to dissolve cerium nitrate solid in a deionized water solution to configure the precursor solution.

[0019] Further, the method for preparing the salt solution is to dissolve Na3PO4 solid in deionized water to configure the salt solution.

[0020] Further, the aging reaction temperature in step S2 is 25 to 60°C, preferably 25°C, and the time is 1 to 3 hours, preferably 1 hour.

[0021] Further, the hydrothermal reaction temperature in step S2 is 100 to 200°C, preferably 180°C, and the time is 6 to 48 hours, preferably 12 hours.

[0022] Further, the drying temperature in step S2 is 60 to 100°C, preferably 60°C, and the time is 12 to 24 hours, preferably 12 hours.

[0023] Further, the calcination temperature in step S3 is 300-600°C, preferably 400°C, and the time is 1-8 hours, preferably 4 hours.

[0024] Further, the reaction temperature in step S4 is 80°C.

[0025] Further, the hydrogen reduction temperature of the catalyst in step S4 is 300-500°C, preferably 350°C, and the time is 1-8 hours, preferably 2 hours.

[0026] Further, the noble metal solution in step S4 is configured using PdCl2, PtCl4, RhCl3, HAuCl3, RuCl3, and IrCl3 as precursors.

[0027] Further, the organic silicon reagent in step S5 is methyltriethoxysilane or methyltrimethoxysilane, and the alcohol used is methanol or ethanol.

[0028] Further, the drying temperature in step S5 is 60-120°C, preferably 80°C, and the time is 2-8 hours, preferably 6 hours.

[0029] Further, the high-temperature calcination temperature in step S5 is 300-500°C, preferably 350°C, and the time is 1-8 hours, preferably 2 hours.

[0030] Compared with the prior art, the present application has the beneficial effects of:

[0031] 1. The present application strengthens the interface interaction between the supported metal and the carrier, realizes high conversion removal of T2 at room temperature or even low temperature, and due to the reduced adsorption of the catalyst to T2O and H2O, the catalyst can also maintain good activity and stability under certain humidity conditions. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The transmission electron microscope (TEM) and energy dispersive X-ray spectrometer (EDX) element distribution map of the octahedral catalyst prepared in Example 1 of the present application.

[0033] Figure 2 The flow chart of the T2 removal performance test device. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments of the present application.

[0035] Example 1

[0036] A nano-octahedral ceria supported palladium catalyst and a preparation method thereof, (1) 0.8246 g of Ce(N03)3-6H20 solid is dissolved in 5 mL of water to prepare a solution. 0.0076 g of Na3P04 solid is dissolved in 35 mL of water. The two solutions are mixed thoroughly in a heat-resistant glass bottle and aged by continuous stirring for 60 minutes. The mixture is added to a high-pressure reaction kettle with a polytetrafluoroethylene liner and hydrothermally treated at 180°C for 24 hours. The solid product is centrifuged, filtered and washed to neutral, and then the Ce02 solid is dried in an oven at 60°C for 12 hours. Then calcined at 400°C for 2 hours in air to obtain a Ce02 nano-octahedral carrier. A precursor aqueous solution of palladium and gold 2.5 mL (containing 0.0025 g of Pd and 0.0025 g of Au) is added to 0.995 g of the Ce02 nano-octahedral carrier, stirred uniformly and continuously reacted at a reaction temperature of 80°C; the reacted catalyst is dried overnight, then reduced at 300°C for 2 h in hydrogen to obtain a semi-finished product. 1 g of the semi-finished product is placed in 20 mL of ethanol, 0.1 g of methyl triethoxysilane is added, stirred uniformly, continuously reacted at a reaction temperature of 40°C, dried at 60°C for 2 h, and then calcined at 400°C for 2 h to obtain a Si02@Pd-Au / Ce02 catalyst.

[0037] Example 2

[0038] A nano-octahedral ceria supported palladium catalyst and a preparation method thereof, (1) 0.8246 g of Ce(N03)3-6H20 solid is dissolved in 5 mL of water to prepare a solution. 0.0076 g of Na3P04 solid is dissolved in 35 mL of water. The two solutions are mixed thoroughly in a heat-resistant glass bottle and aged by continuous stirring for 60 minutes. The mixture is added to a high-pressure reaction kettle with a polytetrafluoroethylene liner and hydrothermally treated at 180°C for 24 hours. The solid product is centrifuged, filtered and washed to neutral, and then the Ce02 solid is dried in an oven at 60°C for 12 hours. Then calcined at 400°C for 2 hours in air to obtain a Ce02 nano-octahedral carrier. A precursor aqueous solution of palladium and gold 2.5 mL (containing 0.0025 g of Pd and 0.0025 g of Au) is added to 0.995 g of the Ce02 nano-octahedral carrier, stirred uniformly and continuously reacted at a reaction temperature of 80°C; the reacted catalyst is dried overnight, then reduced at 300°C for 2 h in hydrogen to obtain a semi-finished product. 1 g of the semi-finished product is placed in 20 mL of ethanol, 0.1 g of methyl triethoxysilane is added, stirred uniformly, continuously reacted at a reaction temperature of 40°C, dried at 60°C for 2 h, and then calcined at 400°C for 2 h to obtain a Si02@Pd-Au / Ce02 catalyst.

[0039] Example 3

[0040] A nano-octahedral cerium oxide supported palladium catalyst and a preparation method thereof, (1) 0.8246 g of Ce(NO3)3·6H2O solid is dissolved in 5 mL of water to prepare a solution. 0.0076 g of Na3PO4 solid is dissolved in 35 mL of water. The two solutions are mixed in a heat-resistant glass bottle and aged by continuously stirring for 60 minutes. The mixture is added to a high-pressure reaction kettle with a polytetrafluoroethylene liner and hydrothermally treated at 100°C for 48 hours. The solid product is centrifuged, filtered and washed to neutral, and then the CeO2 solid is dried in an oven at 100°C for 12 hours. Then calcined in air at 600°C for 2 hours to obtain a CeO2 nano-octahedral carrier. A water solution of palladium and ruthenium precursors 2.5 mL (containing 0.01 g of Pd and 0.01 g of Ru) is added to 0.98 g of the CeO2 nano-octahedral carrier, stirred uniformly and continuously reacted at a reaction temperature of 80°C; the reacted catalyst is dried overnight, and then hydrogenated at 500°C for 8 h to obtain a semi-finished product. 1 g of the semi-finished product is placed in 20 mL of ethanol, 0.1 g of methyltrimethoxysilane is added, stirred uniformly, continuously reacted at a reaction temperature of 40°C, dried at 120°C for 8 h, and calcined at 400°C for 8 h to obtain a SiO2@Pd-Ru / CeO2 catalyst.

[0041] Example 4

[0042] A nano-octahedral cerium oxide supported palladium catalyst and a preparation method thereof, (1) 0.8246 g of Ce(NO3)3·6H2O solid is dissolved in 5 mL of water to prepare a solution. 0.0076 g of Na3PO4 solid is dissolved in 35 mL of water. The two solutions are mixed in a heat-resistant glass bottle and aged by continuously stirring for 60 minutes. The mixture is added to a high-pressure reaction kettle with a polytetrafluoroethylene liner and hydrothermally treated at 200°C for 6 hours. The solid product is centrifuged, filtered and washed to neutral, and then the CeO2 solid is dried in an oven at 60°C for 24 hours. Then calcined in air at 300°C for 2 hours to obtain a CeO2 nano-octahedral carrier. A water solution of palladium and iridium precursors 2.5 mL (containing 0.01 g of Pd and 0.04 g of Ir) is added to 0.95 g of the CeO2 nano-octahedral carrier, stirred uniformly and continuously reacted at a reaction temperature of 80°C; the reacted catalyst is dried overnight, and then hydrogenated at 300°C for 2 h to obtain a semi-finished product. 1 g of the semi-finished product is placed in 20 mL of methanol, 0.1 g of methyltriethoxysilane is added, stirred uniformly, continuously reacted at a reaction temperature of 40°C, dried at 60°C for 8 h, and calcined at 300°C for 8 h to obtain a SiO2@Pd-Ir / CeO2 catalyst.

[0043] Example 5

[0044] A nano-octahedral cerium oxide supported palladium catalyst and a preparation method thereof, (1) 0.8246 g of Ce(NO3)3·6H2O solid is dissolved in 5 mL of water to prepare a solution. 0.0076 g of Na3PO4 solid is dissolved in 35 mL of water. The two solutions are mixed in a heat-resistant glass bottle and aged by continuously stirring for 60 minutes. The mixture is added to a high-pressure reaction kettle with a polytetrafluoroethylene liner and hydrothermally treated at 160°C for 6 hours. The solid product is centrifugally separated, filtered and washed to neutral, and then the CeO2 solid is dried in an oven at 60°C for 12 hours. Then calcined in air at 350°C for 2 hours to obtain a CeO2 nano-octahedral carrier. A water solution of precursors of palladium and rhodium 2.5 mL (containing 0.04 g of Pd and 0.01 g of Rh) is added to 0.95 g of the CeO2 nano-octahedral carrier, stirred uniformly and continuously reacted at a reaction temperature of 80°C; the reacted catalyst is dried overnight, and then calcined in hydrogen at 350°C for 6 hours to obtain a semi-finished product. 1 g of the semi-finished product is weighed and placed in 20 mL of ethanol, 0.1 g of methyltrimethoxysilane is added, stirred uniformly, continuously reacted at a reaction temperature of 40°C, dried at 80°C for 2 hours, and then calcined at 400°C for 8 hours to obtain a SiO2@Pd-Rh / CeO2 catalyst.

[0045] Example 6

[0046] A nano-octahedral cerium oxide supported palladium catalyst and a preparation method thereof, (1) 0.8246 g of Ce(NO3)3·6H2O solid is dissolved in 5 mL of water to prepare a solution. 0.0076 g of Na3PO4 solid is dissolved in 35 mL of water. The two solutions are mixed in a heat-resistant glass bottle and aged by continuously stirring for 60 minutes. The mixture is added to a high-pressure reaction kettle with a polytetrafluoroethylene liner and hydrothermally treated at 160°C for 6 hours. The solid product is centrifugally separated, filtered and washed to neutral, and then the CeO2 solid is dried in an oven at 60°C for 12 hours. Then calcined in air at 350°C for 2 hours to obtain a CeO2 nano-octahedral carrier. A water solution of precursors of palladium, ruthenium and rhodium 2.5 mL (containing 0.01 g of Pd, 0.01 g of Ru and 0.01 g of Rh) is added to 0.97 g of the CeO2 nano-octahedral carrier, stirred uniformly and continuously reacted at a reaction temperature of 80°C; the reacted catalyst is dried overnight, and then calcined in hydrogen at 350°C for 6 hours to obtain a semi-finished product. 1 g of the semi-finished product is weighed and placed in 20 mL of ethanol, 0.1 g of methyltrimethoxysilane is added, stirred uniformly, continuously reacted at a reaction temperature of 40°C, dried at 80°C for 2 hours, and then calcined at 400°C for 8 hours to obtain a SiO2@Pd-Ru-Rh / CeO2 catalyst.

[0047] Catalyst performance test

[0048] The nano-octahedral cerium oxide supported palladium catalyst prepared in Example 1-6 was respectively placed in the tritium catalysis and separation module of the device shown in Figure 2 The test did not need pretreatment before testing, the raw material gas was 50 mL / min of tritium gas-air mixture, the catalyst dosage was 1 g, the reaction temperature was -10-40℃, and the pressure was normal pressure. The test results are shown in Table 1.

[0049] Table 1 Test results of the T2 oxidation performance of the catalysts of the present application

[0050]

[0051] From the above Table 1, it can be seen that the alloy of the present application can significantly improve the T2 oxidation activity of the catalyst at low temperature, prolong the service life of the catalyst in the water environment, and reduce the use cost of the catalyst.

[0052] The above is the embodiment of the embodiment, but the embodiment is not limited to the above optional embodiment, and those skilled in the art can obtain other various embodiments by arbitrarily combining the above embodiments. Any person can obtain other various forms of embodiments under the inspiration of the embodiment. The above specific embodiments should not be understood as limiting the protection scope of the embodiment, and the protection scope of the embodiment should be defined by the claims, and the specification can be used to explain the claims.

Claims

1. The use of a nanooctahedral ceria supported palladium catalyst for the removal of tritium gas at room temperature, characterized in that: The catalyst comprises a carrier, a supported active metal and a silicon dioxide surface layer; the carrier is a nano-octahedral cerium oxide, and the supported active metal is a nano-alloy containing Pd; The nano-alloy is a nano-alloy of Pd and one or more of noble metals Pt, Rh, Au, Ru and Ir.

2. The use of a nano-octahedral ceria supported palladium catalyst according to claim 1 for the removal of tritium gas at room temperature, characterized in that: The nano-octahedral cerium oxide supported Pd catalyst has a mass of 100% in terms of mass percentage, and the content of the supported noble metal is 0.5%-5.0%.

3. The use of a nano-octahedral ceria supported palladium catalyst according to claim 1 for the removal of tritium gas at room temperature, characterized in that: The nano-octahedral cerium oxide supported Pd catalyst has a mass of 100% in terms of mass percentage, and the content of the silicon dioxide surface layer is 0.05%-3.0%.

4. The use of a nano-octahedral ceria supported palladium catalyst according to claim 1 for the removal of tritium gas at room temperature, characterized in that: The preparation method of the catalyst comprises the following steps: S1. configuring a precursor solution and a salt solution; S2. mixing and stirring the precursor solution and the salt solution, then aging the mixed solution sufficiently, and then performing a hydrothermal reaction at high temperature, washing, filtering and drying the catalyst after the reaction overnight to obtain a solid; S3. calcining the solid prepared in step S2 to obtain nano-octahedral cerium oxide; S4. gradually adding a noble metal solution to the nano-octahedral cerium oxide carrier prepared in step S3 to perform a reaction and stir uniformly; drying the catalyst after the reaction overnight, and then performing hydrogen high-temperature reduction to obtain a nano-octahedral cerium oxide supported Pd catalyst without a surface SiO2; S5. placing the nano-octahedral cerium oxide supported Pd catalyst without a surface SiO2 obtained in S4 into an alcohol solution containing a silicone reagent to perform a reaction and stir uniformly; drying the catalyst after the reaction overnight, and then calcining to obtain a nano-octahedral cerium oxide supported Pd catalyst with a SiO2 surface layer.

5. The use of a nanooctahedral ceria supported palladium catalyst according to claim 4 for the removal of tritium gas at room temperature, characterized in that: The preparation method of the precursor solution is to dissolve cerium nitrate solid in a deionized water solution to configure a precursor solution.

6. The use of a nano-octahedral ceria supported palladium catalyst according to claim 4 for the removal of tritium gas at room temperature, characterized in that: The preparation method of the salt solution is to dissolve Na3PO4 solid in deionized water to configure a salt solution.

7. The use of a nano-octahedral ceria supported palladium catalyst according to claim 4 for the removal of tritium gas at room temperature, characterized in that, The silicone reagent in step S5 is methyl triethoxysilane or methyl trimethoxysilane.

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