Preparation method of defective Pd / ZrO2 catalyst and application of defective Pd / ZrO2 catalyst in catalytic hydrogenation of nitrile rubber
By constructing an oxygen vacancies defective Pd/ZrO2 catalyst on the surface of ZrO2 support, the problems of catalyst separation and active metal loss in heterogeneous catalytic hydrogenation of hydrogenated nitrile rubber are solved, and efficient and low-cost catalytic hydrogenation effect is achieved.
Patent Information
- Application Number
- CN202510555422.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-29
- Publication Date
- 2025-07-29
AI Technical Summary
In the prior art, heterogeneous catalytic hydrogenation of hydrogenated nitrile rubber has problems such as difficulty in separation between catalyst and rubber liquid, loss of active metals, low contact efficiency and poor catalyst reusability. In addition, traditional preparation methods use a large number of organic solvents, which increase costs and pollute the environment.
The precipitation method is used to prepare tetragonal phase ZrO2 nanoparticles as support, and oxygen vacancy defects are constructed on their surface by NaBH4 or N2H4·H2O reducing agent, and defective Pd/ZrO2 catalyst is prepared to optimize metal-support interaction and dispersion.
The hydrogenation activity and stability of the catalyst are improved, and the hydrogenation degree of hydrogenated nitrile rubber reaches 96.7%, and the preparation cost is reduced and environmental pollution is reduced.
Smart Images
Figure CN120381838A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of polymer hydrogenation chemical industry, and particularly relates to a preparation method of a defective Pd / ZrO2 catalyst and its application in the catalytic hydrogenation of nitrile rubber. Background Art
[0002] Hydrogenated nitrile rubber (HNBR) has excellent properties such as aging resistance, heat resistance, ozone resistance, and chemical corrosion resistance, and is widely used in the fields of petrochemical industry, aerospace, national defense, automotive, and lithium batteries. Due to the rapid development of terminal industries such as automotive and lithium batteries, the market demand for hydrogenated nitrile rubber has increased rapidly. Therefore, more and more companies and researchers at home and abroad have continuously increased their R & D investment in hydrogenated nitrile rubber. Currently, the industrial production of hydrogenated nitrile rubber mostly adopts homogeneous solution hydrogenation process, but this process has problems such as difficult separation of the catalyst from the rubber solution, which affects the subsequent processing and use performance of the product. Compared with homogeneous solution hydrogenation, heterogeneous solution catalytic hydrogenation can better solve problems such as catalyst recycling, saving costs while avoiding the influence of precious metals remaining in the product on product performance. However, there are still challenges in the heterogeneous solution hydrogenation of nitrile rubber. For example, nitrile rubber molecules have high viscosity, low diffusion coefficient, and there is an adsorption interaction between -C≡N in the molecular chain and Pd, which easily reduces the contact efficiency between nitrile rubber molecules and active sites, and causes Pd loss, reducing the reusability of the catalyst. Therefore, eliminating internal mass transfer limitations and enhancing the metal - support interaction are the key factors for efficient hydrogenation of nitrile rubber (ACS Catal. 2024, 14, 1432 - 1442).
[0003] In the research and development of NBR heterogeneous catalysts, the main focus is on improving the metal - support interaction, aiming to solve problems such as the loss of active metal and the significant reduction of secondary hydrogenation activity. Then, on this basis, the catalytic activity is further improved by designing the support structure and regulating the electronic properties of the active metal (Ind. Eng. Chem. Res. 2019, 58, 11821−11830; J.Mater. Sci. 2020, 55, 12876 - 12883). However, both the support surface modification and the active metal loading process in the previous research require the use of a large amount of organic solvents, which not only increases the catalyst preparation cost but also pollutes the environment. Therefore, the development of a green, low - cost, highly dispersed, and highly stable supported Pd - based catalyst is of great significance and value for the industrial production of high - value - added HNBR.
[0004] To address the weak interaction between the support and the metal and improve the hydrogenation activity and stability of the catalyst, rationally designing the support structure and regulating the surface chemical properties of the support are the keys to preparing highly active and stable catalysts. Zirconia (ZrO₂) is a material with both acid-base bifunctional properties, having reducibility and oxidizability on its surface. Moreover, when the crystal structure of ZrO₂ is different, there are significant differences in its surface chemical properties. Some studies have found that the catalytic effect is closely related to the crystal structure of ZrO₂. Among them, in the reaction of benzene hydrogenation to cyclohexene, the catalyst prepared with tetragonal ZrO₂ as the support has better catalytic performance than that prepared with monoclinic ZrO₂ (Chem. Eng. J. 2014, 243, 207 - 216). In addition, research has shown that surface defects on the support can not only further enhance the metal-support interaction, but also improve the dispersion of active metals, reduce particle size, change the electronic state, etc. The resulting catalyst exhibits excellent catalytic activity, stability, and selectivity in hydrogenation reactions (ACS Catal. 2024, 14, 1432 - 1442). Therefore, selecting a ZrO₂ support with a suitable crystal form and introducing surface defects on its surface are the keys to creating a high-performance NBR hydrogenation catalyst. Summary of the Invention
[0005] The purpose of the present invention is to provide a method for preparing a defective Pd / ZrO₂ catalyst, which can be applied to the efficient hydrogenation reaction of nitrile butadiene rubber to prepare hydrogenated nitrile butadiene rubber.
[0006] To achieve the above purpose, the present invention adopts the following technical solutions: A method for preparing a defective Pd / ZrO₂ catalyst, comprising the following steps: (1) Preparation of the ZrO₂ support: Disperse zirconium oxychloride octahydrate in deionized water, stir at room temperature for 10 min, then dropwise add ammonia water during stirring to adjust the pH value to 9.5, and react at 100 °C for 48 h. After the reaction is completed, cool to room temperature, filter by suction, wash the precipitate repeatedly with deionized water, place it in an 80 °C oven to dry overnight, and finally calcine at 600 °C for 6 h to obtain ZrO₂ nanoparticles.
[0007] (2) Construction of the defective Pd / ZrO₂ catalyst: Using the ZrO₂ obtained in step (1) as the support and palladium acetate as the palladium source, perform reduction treatment by introducing a reducing agent, and the reducing agent is NaBH₄ or N₂H₄·H₂O. The specific steps are as follows: (a) Defective Pd / ZrO₂ - NaBH₄ catalyst Take 1 g of the ZrO2 prepared in step (1) as the carrier, disperse the carrier into 50 mL of deionized water, add 1.89 mL of 0.01 mol / L palladium acetate solution and stir for 30 min. Subsequently, quickly add 1 g of NaBH4 powder under vigorous stirring, react at room temperature for 6 h, then centrifuge, wash, and dry to prepare the Pd / ZrO2-NaBH4 catalyst; (b) Defective Pd / ZrO2-N2H4 catalyst Take 3 g of the ZrO2 prepared in step (1) as the carrier, use palladium acetate as the palladium source, and prepare Pd / ZrO2 by the equal-volume impregnation method. Add 2.5 g of Pd / ZrO2 to 17 mL of N2H4·H2O solution, stir at 80 °C for 1 h, filter the sample, wash, and dry at 60 °C for 10 h to prepare Pd / ZrO2-N2H4.
[0008] The defective Pd / ZrO2 catalyst containing oxygen vacancy defects prepared by the above method can be used for the catalytic hydrogenation of NBR to prepare HNBR. The specific application method is as follows: Weigh a certain mass of NBR, dissolve it in 80 g of acetone solvent to obtain an NBR rubber solution, and then add the obtained NBR rubber solution and the above defective Pd / ZrO2 catalyst containing oxygen vacancy defects to a high-pressure reaction kettle. The mass ratio of the catalyst to NBR is 1:1, and hydrogenation reaction is carried out under the conditions of 40 - 100 °C, hydrogen pressure of 0.5 - 2 MPa, and stirring rate of 600 - 1000 rpm for 1 - 4 h. Cool the reaction solution to room temperature and centrifuge.
[0009] In the present invention, ZrO2 nanoparticles synthesized by the precipitation method are used as the carrier. By regulating the type of chemical reducing agent, reduction process parameters, and reduction process, an oxygen vacancy defect structure is introduced on its surface, and a defective Pd / ZrO2 catalyst with a controllable oxygen vacancy concentration is successfully prepared. The catalyst effectively improves the dispersion of the active component palladium through the construction of oxygen vacancies, forming more highly active metal-support interface sites on the surface. At the same time, the electron effect induced by oxygen vacancies optimizes the adsorption configuration of NBR molecules on the surface of the palladium-based catalyst, significantly enhancing the interaction of the catalytic system. The optimized catalyst shows excellent hydrogenation performance in the hydrogenation reaction of NBR, and the hydrogenation degree of hydrogenated nitrile rubber is as high as 96.7%.
[0010] The beneficial effects of the present invention are as follows: (1) The Pd / ZrO2 catalyst prepared in the present invention has a tetragonal crystal structure, and the active metal is evenly dispersed on the surface of the carrier, which is beneficial to the full contact between NBR and the active metal. It can adjust the active sites of the catalyst, optimize the adsorption configuration and strength of reactant molecules, etc., so as to control the selectivity of the hydrogenation products of the catalyst.
[0011] (2) The prepared Pd / ZrO2-N2H4 and Pd / ZrO2-NaBH4 of the present invention are both Pd / ZrO2 catalysts containing oxygen vacancy defects. By modulating the defect construction method, the content of oxygen vacancy defects on the catalyst surface is increased, which not only helps to improve the dispersion and stability of the active metal palladium, but also can regulate its electronic structure, and improve the hydrogenation activity and stability of the catalyst.
[0012] (3) The conditions for preparing the catalyst of the present invention are mild, and it has excellent performance when applied to the low-temperature hydrogenation of NBR.
[0013] (4) There has been no research on using Pd / ZrO2 catalysts containing oxygen vacancy defects for this reaction before, which can provide reference value for the research on using palladium-based catalysts for the hydrogenation of NBR to prepare chemicals with high hydrogenation activity to a certain extent. Description of the Drawings
[0014] Figure 1 It is the TEM image of the ZrO2 nanoparticle support and Pd / ZrO2 catalyst prepared in the examples.
[0015] Figure 2 It is the EPR image of the defective Pd / ZrO2-N2H4 catalyst and defective Pd / ZrO2-NaBH4 catalyst prepared in the examples.
[0016] Figure 3 It is the comparison chart of the hydrogenation degree of the hydrogenation products of the defective Pd / ZrO2-N2H4 catalyst and defective Pd / ZrO2-NaBH4 catalyst prepared in the examples. Detailed Embodiments
[0017] In order to clearly display the technical content, features and effects of the present invention, the following examples will describe the present invention more accurately and comprehensively, but it should not be understood as a limitation on the scope of the present invention that can be implemented. The methods of the present invention are all conventional methods in the art unless otherwise specified.
[0018] Comparative Example (1) Preparation of the ZrO2 support: Weigh 8.0563 g of ZrOCl₂·8H₂O and place it in a 100 mL reaction flask. Add 50 mL of deionized water, and then place it on a magnetic stirrer and stir at high speed for 10 min. Subsequently, while stirring, add ammonia water dropwise to the mixed solution to adjust the pH value to 9.5. Then heat and stir the above mixed solution with adjusted pH value in a water bath at 100 °C for 48 h. After the reaction is completed and cooled to room temperature, filter by suction to separate the precipitate, wash it with deionized water until neutral, and then grind it into a powder. First, place it in an oven at 80 °C and dry it overnight, and then calcine it at 600 °C for 6 h (heating rate 2 °C / min) to obtain the zirconia support.
[0019] (2) Preparation of Pd / ZrO₂ catalyst by equal-volume impregnation method: Take 1.5069 g of the ZrO₂ prepared in step (1) as the support, add dichloromethane dropwise to measure the water absorption rate of the support, record the data of 2.00 mL, and then place it in an oven at 80 °C and dry it for 30 min. Weigh 0.0338 g of palladium acetate and dissolve it in 2.00 mL of dichloromethane solution to prepare a precious metal precursor solution. Add the precursor solution dropwise to the above support and impregnate it at room temperature for 12 h, and then dry it overnight in an oven at 80 °C to obtain the catalyst precursor. Place the above catalyst precursor in a muffle furnace and calcine it at 550 °C (heating rate 5 °C / min) for 4 h, and then place it in a tubular furnace. Under a H₂ atmosphere (90% Ar₂, 10% H₂), reduce it at 140 °C (heating rate 5 °C / min) for 2 h. After reduction, a supported Pd-based catalyst is obtained, named Pd / ZrO₂ (Pd loading 1 wt.%).
[0020] (3) Hydrogenation reaction of NBR: Dissolve 1 g of NBR in 80 g of acetone, and then place it on a magnetic stirrer and stir for more than 3 h until the NBR is fully dissolved and evenly distributed to obtain an NBR rubber solution. The hydrogenation reaction conditions of NBR are as follows: dosage of catalyst Pd / ZrO₂: 1 g, reaction temperature: 60 °C, hydrogen pressure: 1 MPa, stirring speed: 800 rpm, reaction time: 2 h. Before stirring, turn on the condensed water first. Before heating up, check whether the thermocouple is connected to the reaction kettle and whether there is water entering the condensed water inlet and outlet. At the end of the reaction, turn off the console switch to stop heating and stirring, turn off the condensed water. After the reaction kettle drops to a certain temperature, open the kettle to take samples. Centrifuge and separate the catalyst and the rubber solution, and precipitate the rubber solution with deionized water to obtain the hydrogenated product HNBR. After the product is dried in an oven at 80 °C for several hours, calculate the hydrogenation conversion rate through the data obtained by infrared spectroscopy. The calculated result is: for the Pd / ZrO₂ catalyst without oxygen vacancy defects, the hydrogenation activity of hydrogenated nitrile rubber is 95.1%.
[0021] Example 1 The ZrO2 support was prepared by the same method as in step (1) of the comparative example.
[0022] (1) Preparation of defective Pd / ZrO2 - NaBH4 catalyst: Take 1 g of ZrO2 as the support, disperse the support in 50 mL of deionized water, add 1.89 mL of a dichloromethane solution of 0.01 mol / L palladium acetate and stir for 30 min. Subsequently, quickly add 1 g of NaBH4 powder under vigorous stirring, react at room temperature for 6 h, then centrifuge to collect the precipitate, wash it several times with deionized water and ethanol, and dry it at 60 °C. The obtained sample was named Pd / ZrO2 - NaBH4 catalyst (Pd loading 1 wt.%).
[0023] (2) Catalytic hydrogenation of NBR: Dissolve 1 g of NBR in 80 g of acetone, then place it on a magnetic stirrer and stir for more than 3 h until the NBR is fully dissolved and evenly distributed to obtain an NBR rubber solution. The NBR hydrogenation reaction conditions are as follows: catalyst Pd / ZrO2 - NaBH4 dosage: 1 g, reaction temperature: 60 °C, hydrogen pressure: 1 MPa, stirring speed: 800 rpm, reaction time: 2 h. Turn on the condensed water before stirring. Before heating up, check whether the thermocouple is connected to the reaction kettle and whether there is water entering the condensed water inlet and outlet. At the end of the reaction, turn off the console switch to stop heating and stirring, turn off the condensed water. After the reaction kettle cools down to a certain temperature, open the kettle to take samples. Centrifuge and separate the catalyst and the rubber solution, and coagulate the rubber solution with deionized water to obtain the hydrogenated product HNBR. After the product is dried in an oven at 80 °C for several hours, the hydrogenation conversion rate is calculated based on the data obtained by infrared spectroscopy. The calculated result is: for the Pd / ZrO2 - NaBH4 catalyst with oxygen vacancy defects, the hydrogenation activity of hydrogenated nitrile rubber is 96.2%.
[0024] Example 2 The ZrO2 support and Pd / ZrO2 were prepared by the same methods as in steps (1) and (2) of the comparative example.
[0025] (1) Preparation of defective Pd / ZrO2 - N2H4 catalyst: Take 2.5 g of Pd / ZrO2 catalyst, add 2.5 g of Pd / ZrO2 to 17 mL of N2H4·H2O solvent, stir at 80 °C for 1 h, then filter the sample, wash the precipitate several times with ultrapure water, and dry it at 60 °C for 10 h. The obtained solid sample was named Pd / ZrO2 - N2H4 (Pd loading 1 wt.%).
[0026] (2)Catalytic hydrogenation of NBR: Dissolve 1 g of NBR in 80 g of acetone, and then place it on a magnetic stirrer and stir for more than 3 h. After the NBR is fully dissolved and evenly distributed, an NBR rubber solution is obtained. The NBR hydrogenation reaction conditions are as follows: dosage of catalyst Pd / ZrO2-N2H4: 1 g, reaction temperature: 60 °C, hydrogen pressure: 1 MPa, stirring speed: 800 rpm, reaction time: 2 h. Before stirring, turn on the condensed water first. Before heating up, check whether the thermocouple is connected to the reaction kettle and whether there is water entering the inlet and outlet of the condensed water. At the end of the reaction, turn off the console switch to stop heating and stirring, turn off the condensed water. After the reaction kettle cools down to a certain temperature, open the kettle to take samples. Centrifuge and separate the catalyst and the rubber solution, and precipitate the rubber solution with deionized water to obtain the hydrogenated product HNBR. After the product is dried in an oven at 80 °C for several hours, the hydrogenation conversion rate is calculated based on the data obtained by infrared spectroscopy. The calculated result is that the hydrogenation activity of hydrogenated nitrile rubber with the Pd / ZrO2-N2H4 catalyst containing oxygen vacancy defects is 96.7%.
[0027] Figure 1 (a)-(b) are TEM images of the ZrO2 support. As can be seen from the figure, the support is composed of stacked particles. This is because irregular particles with a polycrystalline structure are initially formed at low temperatures. As the water bath temperature increases, these particles continuously undergo a dissolution-recrystallization process and gradually transform into small and uniform crystals. Figure 1 (c) is the TEM image of the Pd / ZrO2 catalyst. As can be seen from the figure, the Pd / ZrO2 catalyst has small and uniformly dispersed Pd particles. To further understand the dispersion of each element on the Pd / ZrO2 catalyst, STEM characterization was performed on the Pd / ZrO2 catalyst. As Figure 1 (d)-(f) show, it can be observed that the Pd element is evenly distributed on the Pd / ZrO2 catalyst.
[0028] Figure 2 are the EPR images of the defective Pd / ZrO2-N2H4 catalyst and the defective Pd / ZrO2-NaBH4 catalyst prepared in the examples. As can be seen from the figure, the defective Pd / ZrO2-N2H4 catalyst under the N2H4 treatment process will generate more oxygen vacancy defects.
[0029] Figure 3 is a comparison chart of the hydrogenation degrees of the hydrogenation products of the defective Pd / ZrO2-N2H4 catalyst and the defective Pd / ZrO2-NaBH4 catalyst prepared in the examples. The hydrogenation test results show that the hydrogenation degree of the Pd / ZrO2-NaBH4 catalyst is 96.2%, and the hydrogenation degree of the defective Pd / ZrO2-N2H4 catalyst is 96.7%.
[0030] The above are only the preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.
Claims
1. A preparation method of a defective Pd / ZrO2 catalyst, characterized in that: It includes the following steps: (1) Preparation of ZrO2 support: Dissolve zirconium oxychloride octahydrate in deionized water, dropwise add ammonia water during stirring to adjust the pH value, then react at 100 ºC for 48 h. After the reaction, filter the precipitate by suction, wash, dry and calcine to obtain ZrO2 nanoparticles; (2) Construction of defective Pd / ZrO2 catalyst: Using the ZrO2 obtained in step (1) as the support and palladium acetate as the palladium source, perform reduction treatment by introducing a reducing agent. After the reduction product is separated by solid-liquid separation, washed and dried, a defective Pd / ZrO2 catalyst is obtained. The reducing agent is NaBH4 or N2H4·H2O.
2. The preparation method according to claim 1, characterized in that: The specific steps for constructing the defective Pd / ZrO2 catalyst in step (2) are: Disperse the ZrO2 support in deionized water, add the palladium acetate solution and stir for 30 min, then quickly add NaBH4 powder for reaction.
3. The preparation method according to claim 1, wherein: The specific steps for constructing the defective Pd / ZrO2 catalyst in step (2) are: Load the palladium acetate solution onto the ZrO2 support by the equal-volume impregnation method to obtain Pd / ZrO2, and then add Pd / ZrO2 to N2H4·H2O for reaction.
4. The preparation method according to claim 1, characterized in that: In the defective Pd / ZrO2 catalyst described in step (2), the loading amount of Pd metal is 0.5 - 2.0 wt.%.
5. The preparation method according to claim 2, wherein: The mass ratio of the ZrO2 support to the NaBH4 powder is 1:1 - 3, the concentration of the palladium acetate solution is 5 - 20 mM, the reaction temperature is 20 - 60 ºC, and the reaction time is 3 - 8 h.
6. The preparation method according to claim 3, characterized in that: The dosage ratio of N2H4·H2O to Pd / ZrO2 is 4 - 10 mL:1 g, the reaction temperature is 60 - 100 ºC, and the reaction time is 0.5 - 3 h.
7. A Pd / ZrO2 catalyst containing oxygen vacancy defects prepared by the method according to any one of claims 1 - 6.
8. Application of the Pd / ZrO2 catalyst containing oxygen vacancy defects according to claim 7 in the hydrogenation of nitrile rubber to prepare hydrogenated nitrile rubber.
9. The application according to claim 8, characterized in that: The mass ratio of the Pd / ZrO2 catalyst to the nitrile rubber is 1:1, the reaction temperature is 40 - 100 ºC, the hydrogen pressure is 0.5 - 2 MPa, the stirring rate is 600 - 1000 rpm, and the reaction is 1 - 4 h.