Preparation method of palladium oxide solid material

Abstract

The invention relates to a preparation method of a palladium oxide solid material, which comprises the following steps: dissolving palladium nitrate in nitric acid to obtain a palladium nitrate-nitric acid solution, mixing the palladium nitrate-nitric acid solution with fused salt, calcining at high temperature, adding water into a reaction product, ultrasonically dissolving, centrifugally filtering and drying to obtain the palladium oxide solid material. Compared with the prior art, a high-temperature molten salt method is used, and toxic chlorine and a complex technological process are avoided. The method comprises the following steps: firstly, directly converting palladium nitrate into a palladium oxide solid by using a high-temperature molten salt method, then removing molten salt through ultrasonic washing, and finally, carrying out centrifugal filtration and drying to obtain a pure palladium oxide solid.

Description

Technical Field

[0001] The present invention relates to the field of inorganic compounds, and particularly to a method for preparing a palladium oxide solid material. Background Art

[0002] Palladium oxide is an important metal compound with a wide range of applications. Palladium oxide is widely used in multiple fields such as chemical industry, electronics, healthcare, and environmental protection. In the chemical industry, palladium oxide is an efficient catalyst. Especially in the petrochemical industry, it is widely used in the hydrogenation and dehydrogenation reactions of hydrocarbons. Due to the unique surface activity of palladium oxide, it can provide a large number of active centers, thus greatly improving the reaction rate and conversion rate. In the electronic industry, due to its good electrical conductivity and stability, palladium oxide is often used as a conductive paste for advanced electronic devices, such as chips, printed circuit boards, and displays. In the healthcare field, palladium oxide has excellent antioxidant properties and is often used to manufacture anti-corrosion and antioxidant coatings. In the environmental protection field, palladium oxide is also widely used in the photocatalytic degradation of organic pollutants to help purify water and air.

[0003] Palladium is a fission product in high-level radioactive waste, and its content is objective and comparable to natural resources. Extracting and separating palladium from high-level radioactive waste can not only reduce its impact on the vitrification of high-level radioactive waste, but also the recovered palladium can be reused as secondary resources. However, currently, the palladium extracted from high-level radioactive waste is all in the form of palladium nitrate solution and cannot be directly utilized. In order to prepare palladium oxide products that meet market demands, a method for converting palladium nitrate solution into solid palladium oxide needs to be developed.

[0004] Currently, methods for preparing palladium oxide include homogeneous precipitation method, sol-gel method, hydrothermal synthesis method, etc. For example, Ren Yuhua et al. prepared palladium oxide solid by hydrothermal method, but the raw material used in this method is palladium chlorate, not palladium nitrate solution (Ren Yuhua. Hydrothermal Synthesis and Characterization of Platinum Group Metals and Their Oxide Nanoparticles. Master's Thesis. South-Central University for Nationalities, 2011). Patent Publication No. CN105293592A discloses a method for preparing nano-palladium oxide, but this method requires processes such as dissolution - reaction - filtration - concentration - cooling - calcination, which is relatively cumbersome. Patent Publication No. CN103288146A discloses a method for preparing palladium oxide hydrate. This method requires chlorine gas and hydrochloric acid to make refined palladium into chloropalladous acid solution, and then through processes such as precipitation - washing - filtration to obtain palladium oxide hydrate. This method not only uses raw materials that are not palladium nitrate solution, but also requires toxic chlorine gas, and has a greater operational risk in the complex preparation process.

[0005] Therefore, there is an urgent need to study a simple and efficient method to convert palladium nitrate into a palladium oxide solid material. Summary of the Invention

[0006] The object of the present invention is to overcome the defects of the above-mentioned existing technologies and provide a preparation method of palladium oxide solid material, which simply and efficiently converts palladium nitrate into palladium oxide solid material.

[0007] The object of the present invention can be achieved by the following technical solutions:

[0008] A preparation method of palladium oxide solid material, which dissolves palladium nitrate in nitric acid to obtain a palladium nitrate - nitric acid solution, mixes it with molten salt and then conducts high-temperature calcination, and dissolves the reaction product in water by ultrasonic treatment, centrifuges and filters, and dries to obtain palladium oxide solid material.

[0009] Further, the mass content of palladium element in the palladium nitrate - nitric acid solution is 0.001 - 100 g / L.

[0010] Furthermore, the mass content of palladium element in the palladium nitrate - nitric acid solution is 0.01 - 20 g / L.

[0011] Further, the concentration of nitric acid in the palladium nitrate - nitric acid solution is 0.00001 - 10 mol / L.

[0012] Furthermore, the concentration of nitric acid in the palladium nitrate - nitric acid solution is 0.001 - 6 mol / L.

[0013] Further, the molten salt includes one or more of lithium chloride, potassium chloride, potassium nitrate, lithium nitrate, and sodium nitrate.

[0014] Furthermore, the molten salt is any of the following combination modes:

[0015] (a) The molten salt is a mixture of lithium chloride and potassium chloride, and the molar ratio of lithium chloride to potassium chloride is 40 - 70:30 - 60;

[0016] (b) The molten salt is a mixture of potassium nitrate and lithium nitrate, and the molar ratio of potassium nitrate to lithium nitrate is 40 - 70:30 - 60;

[0017] (c) The molten salt is a mixture of potassium nitrate and sodium nitrate, and the molar ratio of potassium nitrate to sodium nitrate is 40 - 70:30 - 60.

[0018] Furthermore, the molten salt is any of the following combination modes:

[0019] (a) The molten salt is a mixture of lithium chloride and potassium chloride, and the molar ratio of lithium chloride to potassium chloride is 50 - 60:40 - 50;

[0020] (b) The molten salt is a mixture of potassium nitrate and lithium nitrate, and the molar ratio of potassium nitrate to lithium nitrate is 50 - 60:40 - 50;

[0021] (c) The molten salt described is a mixture of potassium nitrate and sodium nitrate, and the molar ratio of potassium nitrate to sodium nitrate is 50 - 60:40 - 50.

[0022] Furthermore, the molten salt is any of the following combination methods:

[0023] (a) The molten salt described is a mixture of lithium chloride and potassium chloride, and the molar ratio of lithium chloride to potassium chloride is 59:41;

[0024] (b) The molten salt described is a mixture of potassium nitrate and lithium nitrate, and the molar ratio of potassium nitrate to lithium nitrate is 57:43;

[0025] (c) The molten salt described is a mixture of potassium nitrate and sodium nitrate, and the molar ratio of potassium nitrate to sodium nitrate is 53:47.

[0026] Furthermore, the molar ratio of palladium nitrate to the molten salt in the palladium nitrate - nitric acid solution is 1:5 - 100.

[0027] Furthermore, the molar ratio of palladium nitrate to the molten salt in the palladium nitrate - nitric acid solution is 1:10 - 50.

[0028] Furthermore, the high - temperature calcination is carried out in a segmented manner. Among them, the temperature of the first stage is from room temperature to 100 °C, and the temperature of the second stage is from 100 to 800 °C.

[0029] Furthermore, the heating rate of the first stage is 1 - 5 °C / min, and the heating rate of the second stage is 1 - 20 °C / min.

[0030] Furthermore, after the first stage is heated to the highest temperature, it is kept warm for 10 - 300 min, and after the second stage is heated to the highest temperature, it is kept warm for 30 - 600 min.

[0031] Furthermore, when the reaction product is dissolved in water, the mass - volume ratio of the reaction product to water is 1:5 - 100.

[0032] Furthermore, the frequency of the ultrasonic dissolution is 20 - 100 kHz.

[0033] Furthermore, the rotational speed of the centrifugal filtration is 500 - 5000 rpm.

[0034] Furthermore, the drying temperature is 30 - 120 °C.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] (1) The present invention uses the high-temperature molten salt method, avoiding toxic chlorine gas and complex process flows. First, the high-temperature molten salt method is used to directly convert palladium nitrate into palladium oxide solid. Then, the molten salt is removed by ultrasonic washing. Finally, after centrifugal filtration and drying, pure palladium oxide solid is obtained.

[0037] (2) The operation method of the present invention is simple, convenient and feasible, capable of directly converting palladium nitrate into palladium oxide solid, and having broad application prospects in the preparation of palladium oxide materials.

[0038] (3) Most of the reaction temperatures provided by water and most organic solvents are not high, and traditional solution chemistry methods often have difficulty obtaining oxide nanoparticles with high crystallinity. Molten pure inorganic salts have unique advantages as liquid-phase reaction media and can provide a higher and wider reaction temperature window under atmospheric pressure. The present invention uses molten salt as a solvent, increasing the mass transfer efficiency; secondly, the electrostatic interaction and steric hindrance effect in the molten salt contribute to promoting the nucleation and growth of polar crystals, making it easier to generate palladium oxide nanoparticles; finally, the molten salt can be separated from palladium oxide by simple water washing to obtain high-purity palladium oxide. Description of the Drawings

[0039] Figure 1 XRD spectrum of palladium oxide prepared in Example 2;

[0040] Figure 2 TEM spectrum of palladium oxide prepared in Example 2. Detailed Embodiments

[0041] The present invention will be described in detail below with reference to the drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and the detailed implementation methods and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments. Based on the given embodiments, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of this application.

[0042] Unless otherwise specified, the reagents, methods, instruments and equipment used in the present invention are conventional reagents, methods, instruments and equipment in the art.

[0043] Example 1

[0044] A method for preparing a palladium oxide solid material, comprising the following steps:

[0045] (1) Ratio of raw material composition: Using lithium nitrate at 43 mol% and potassium nitrate at 57 mol% as the molten salt, preparing a 0.001 g / L palladium nitrate-nitric acid solution with 0.00001 mol / L nitric acid, where the molar ratio of palladium nitrate to the molten salt is 1:5;

[0046] (2) Treatment of raw materials: Add the raw materials in the above ratios to an alumina crucible, and stir with a glass rod to make them evenly mixed;

[0047] (3) Calcination of raw materials: Place the alumina crucible in a muffle furnace, first heat from room temperature to 100 °C at a rate of 1 °C / min, hold for 300 min, then heat from 100 °C to 800 °C at a rate of 20 °C / min, hold for 30 min, and obtain the reaction product after the sample cools;

[0048] (4) Treatment of the reaction product: Add deionized water to the reaction product and transfer it to a beaker, then ultrasonicate at 20 kHz for 60 min to dissolve the molten salt in water and obtain a suspension;

[0049] (5) Treatment of the suspension: Centrifuge and filter the suspension at 5000 rpm to obtain a solid, and dry it at 30 °C to obtain a pure palladium oxide solid material.

[0050] Example 2

[0051] A method for preparing a palladium oxide solid material, comprising the following steps:

[0052] (1) Ratio of raw material composition: Use potassium nitrate at 53 mol% and sodium nitrate at 47 mol% as the molten salt, and prepare a 100 g / L palladium nitrate - nitric acid solution with 10 mol / L nitric acid, where the molar ratio of palladium nitrate to the molten salt is 1:100;

[0053] (2) Treatment of raw materials: Add the raw materials in the above ratios to an alumina crucible, and stir with a glass rod to make them evenly mixed;

[0054] (3) Calcination of raw materials: Place the alumina crucible in a muffle furnace, first heat from room temperature to 100 °C at a rate of 5 °C / min, hold for 300 min, then heat from 100 °C to 600 °C at a rate of 10 °C / min, hold for 600 min, and obtain the reaction product after the sample cools;

[0055] (4) Treatment of the reaction product: Add deionized water to the reaction product and transfer it to a beaker, then ultrasonicate at 100 kHz for 10 min to dissolve the molten salt in water and obtain a suspension;

[0056] (5) Treatment of the suspension: Centrifuge and filter the suspension at 500 rpm to obtain a solid, and dry it at 80 °C to obtain a pure palladium oxide solid material.

[0057] Example 3

[0058] A method for preparing a palladium oxide solid material, comprising the following steps:

[0059] (1) Ratio of raw material composition: Using 59 mol% lithium chloride and 41 mol% potassium chloride as molten salt, the molar ratio of palladium nitrate solid to molten salt is 1:20;

[0060] (2) Treatment of raw materials: Add the raw materials in the above ratio to an alumina crucible, and stir with a glass rod to mix evenly;

[0061] (3) Calcination of raw materials: Place the alumina crucible in a muffle furnace, heat from room temperature to 300 °C at a rate of 10 °C / min, hold for 60 min, and obtain the reaction product after the sample cools;

[0062] (4) Treatment of reaction product: Add deionized water to the reaction product and transfer it to a beaker, ultrasonicate at 50 kHz for 30 min, dissolve the molten salt in water to obtain a suspension;

[0063] (5) Treatment of suspension: Centrifuge and filter the suspension at 1000 rpm to obtain a solid, dry it at 120 °C to obtain a pure palladium oxide solid material.

[0064] Comparative Example 1

[0065] Compared with Example 3, most of them are the same, except that in step (1), molten salt is not used and palladium nitrate solid is directly calcined.

[0066] Comparative Example 2

[0067] Compared with Example 3, most of them are the same, except that in step (3), the alumina crucible is placed in a muffle furnace, heated from room temperature to 300 °C at a rate of 10 °C / min, held for 600 min, and the reaction product is obtained after the sample cools, and the calcination temperature is reduced to 200 °C.

[0068] The XRD and TEM spectra of the palladium oxide solid material prepared in Example 2 are as Figure 1 and Figure 2 shown. In Figure 1 , the peaks of the XRD spectrum of the prepared palladium oxide solid sample are consistent with the positions of the PDF#41-1107 reference substance (PdO), and there are no other impurity peaks, indicating that the prepared sample is a single PdO phase with high purity. From Figure 2 it can be seen that the morphology of the prepared palladium oxide solid material is an irregular flaky structure. However, the crystallinity of the solids prepared in Comparative Examples 1 and 2 is not high, and the XRD spectra are incomplete, making it impossible to determine their specific structures.

[0069] Although the present invention has been described in detail above by means of general descriptions, specific embodiments and experiments, modifications or improvements can be made to it based on the present invention, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection required by the present invention.

Claims

1. A method for preparing a palladium oxide solid material, characterized in that, Dissolve palladium nitrate in nitric acid to obtain a palladium nitrate-nitric acid solution. Mix it with molten salt and then carry out high-temperature calcination. Ultrasonically dissolve the reaction product in water, centrifuge and filter, and dry to obtain a palladium oxide solid material.

2. The preparation method of a palladium oxide solid material according to claim 1, characterized in that, The mass content of palladium element in the palladium nitrate-nitric acid solution is 0.001-100 g / L.

3. The preparation method of a palladium oxide solid material according to claim 1, characterized in that, The concentration of nitric acid in the palladium nitrate-nitric acid solution is 0.00001-10 mol / L.

4. The preparation method of a palladium oxide solid material according to claim 1, characterized in that, The molten salt includes one or more of lithium chloride, potassium chloride, potassium nitrate, lithium nitrate, and sodium nitrate.

5. The preparation method of a palladium oxide solid material according to claim 4, wherein, The molten salt is in any of the following combination modes: (a) The molten salt is a mixture of lithium chloride and potassium chloride, and the molar ratio of lithium chloride to potassium chloride is 40-70:30-60; (b) The molten salt is a mixture of potassium nitrate and lithium nitrate, and the molar ratio of potassium nitrate to lithium nitrate is 40-70:30-60; (c) The molten salt is a mixture of potassium nitrate and sodium nitrate, and the molar ratio of potassium nitrate to sodium nitrate is 40-70:30-60.

6. The preparation method of a palladium oxide solid material according to claim 1, wherein, The molar ratio of palladium nitrate to molten salt in the palladium nitrate-nitric acid solution is 1:5-100.

7. The preparation method of a palladium oxide solid material according to claim 1, wherein, The high-temperature calcination is carried out in stages. Among them, the temperature of the first stage is from room temperature to 100 °C, and the temperature of the second stage is 100-800 °C.

8. A method for preparing a palladium oxide solid material according to claim 7, characterized in that, The heating rate of the first stage is 1-5 °C / min, and the heating rate of the second stage is 1-20 °C / min.

9. The preparation method of a palladium oxide solid material according to claim 7, characterized in that, After the first stage is heated to the highest temperature, it is kept warm for 10-300 min. After the second stage is heated to the highest temperature, it is kept warm for 30-600 min.

10. The preparation method of a palladium oxide solid material according to claim 1, characterized in that, The drying temperature is 30-120 °C.

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