Pd / F-Al2O3 catalyst with strong metal-carrier interaction as well as preparation method and application of Pd / F-Al2O3 catalyst

Abstract

The invention relates to a Pd / F-Al2O3 catalyst with strong metal-carrier interaction and a preparation method and application thereof in the technical field of selective catalytic reduction, a catalytic material comprises an active component and a carrier material, the active component is Pd, the carrier material is F-Al2O3 rich in F center and AlV center, and the mass fraction of the active component is 0.5 wt.%. A carrier F-Al2O3 is prepared through high-temperature treatment of basic aluminum acetate in an argon atmosphere, Pd active components are loaded on the surface of the carrier by adopting an initial wet impregnation method, and the efficient catalytic material for nitrous oxide-ammonia gas selective catalytic reduction reaction is finally prepared after centrifugation, drying and calcination in an air atmosphere. The prepared catalytic material has the advantages of being high in metal-carrier interaction, good in active component dispersity and simple in preparation process, the T90 temperature required by the catalytic efficiency reaching 90% is reduced by 30% compared with that of a traditional Pd / Al2O3 catalyst, the wide industrial application prospect is achieved, and upgrading and optimization of the nitrogen oxide pollution control technology are promoted.

Description

Technical Field

[0001] This invention relates to the field of catalytic materials technology, and in particular to a Pd / F-Al2O3 catalyst with strong metal-support interaction, its preparation method, and its application in the selective catalytic reduction reaction of nitrous ammonia. Background Technology

[0002] Selective catalytic reduction (SCR) is a key technology for controlling nitrogen oxide emissions and has wide applications in industrial exhaust gas purification and vehicle exhaust treatment. Nitrous oxide, a potent greenhouse gas and a significant component of nitrogen oxides, requires efficient removal for environmental protection.

[0003] Pd-based catalysts have attracted much attention in SCR reactions due to their excellent catalytic redox performance. Traditional Pd-based catalysts mostly use Al2O3 as a support, but they suffer from problems such as weak metal-support interaction, easy aggregation of Pd active components, and poor high-temperature stability, resulting in insufficient activity and selectivity of the catalysts in SCR reactions, especially under complex conditions where NO coexists, further limiting their catalytic performance.

[0004] To address these issues, researchers have improved the performance of Pd-based catalysts through methods such as support modification and optimization of active component loading. Oxygen vacancies and specific active centers on the support surface can enhance the interaction between the metal and the support, promote the dispersion of the active component, and thus improve catalytic efficiency. However, existing modified support preparation processes are often complex or yield poor modification results, making it difficult to simultaneously meet the requirements of strong interaction, high dispersion, and stability. Therefore, developing a Pd-based catalyst with a simple preparation process, strong metal-support interaction, and excellent performance in SCR reactions has significant practical application value. Summary of the Invention

[0005] The purpose of this invention is to solve the above-mentioned problems in practical application scenarios, and to provide a Pd / F-Al2O3 catalyst with strong metal-support interaction, its preparation method and application, so as to simplify the preparation process of Pd-based catalytic materials, meet the requirements of high activity at low temperature, stable structure and low noble metal loading, and improve the catalytic efficiency of selective catalytic reduction reaction of nitrous oxide-ammonia.

[0006] This invention is achieved through the following technical solution: The Pd / F-Al2O3 catalyst with strong metal-support interaction consists of an active component and a support material, wherein the active component is Pd and the support material is F-Al2O3. F-Al2O3 is rich in F centers with free electron oxygen vacancies and has five-coordinate aluminum ion centers on its surface, which can form a strong metal-support interaction with Pd.

[0007] Furthermore, in this invention, the mass fraction of the active component Pd in ​​the catalyst is 0.5 wt.%.

[0008] This invention also provides a method for preparing a Pd / F-Al2O3 catalyst with strong metal-support interaction, comprising the following steps: Step S1, Preparation of F-Al2O3 support: The precursor is placed in a boat-shaped alumina crucible, placed in a tube furnace, heated to a certain temperature at a fixed heating rate under an inert gas atmosphere, and held at that temperature for a period of time. After natural cooling, F-Al2O3 support is obtained. Step S2, initial wet impregnation of Pd: The F-Al2O3 support is added to an aqueous solution prepared with nitrate hydrate for initial wet impregnation; Step S3, centrifugation and drying: After centrifuging the mixture obtained in step S2, dry it at a specified temperature for a period of time; Step S4, calcination and shaping: The sample dried in step S3 is placed in a calcination atmosphere and under normal pressure to calcine, thereby obtaining the Pd / F-Al2O3 catalyst.

[0009] Furthermore, in step S1 above, the precursor is basic aluminum acetate (Al(CH3COO)2(OH)), the inert gas atmosphere of the tube furnace is argon, the heating rate is fixed at 5℃ / min, the final holding temperature is 400℃, and the holding time is 4 hours.

[0010] Furthermore, in step S2 above, the amount of F-Al2O3 carrier used is 10g; the nitrate hydrate is Pd(NO3)2·2H2O, and the amount used is 0.128g; the impregnation method is initial wet impregnation, and the solvent is deionized water.

[0011] Furthermore, in step S3 above, the drying temperature is 383K and the drying time is 12 hours; centrifugation is used to remove excess moisture from the system to ensure that the carrier and the active component precursor are fully combined.

[0012] Furthermore, in step S4, the calcination atmosphere is air, and the pressure is atmospheric pressure; the calcination temperature is 773K, and the calcination time is 2 hours.

[0013] The present invention also provides an application of the above-mentioned catalyst, which is used in the selective catalytic reduction reaction of nitrous oxide and ammonia.

[0014] Furthermore, in the application of the above-mentioned catalyst, the nitrous oxide-ammonia selective catalytic reduction reaction includes the nitrous oxide-ammonia-SCR reaction alone and the nitrous oxide-ammonia-SCR reaction in the presence of NO; ​​the catalyst can be directly loaded into a fixed-bed reactor and its catalytic performance can be tested by programmed temperature rise.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention fully utilizes the structural characteristics of the F-Al2O3 support, which is rich in F centers (free electron oxygen vacancies) and AlV centers. Through the fixation effect of AlV centers on Pd atoms, a strong metal-support interaction is formed, which effectively improves the dispersibility of Pd active components and avoids their aggregation during the reaction process, thereby increasing the catalytic reaction sites and enhancing intrinsic activity.

[0016] This invention utilizes a high-temperature argon atmosphere to prepare a modified F-Al2O3 support. Pd is loaded via a simple initial wet impregnation method, followed by centrifugation, drying, and air calcination. The process is concise, requiring no complex equipment or harsh reaction conditions, facilitating industrial scale-up. Test results show that the catalyst's T90 temperature is 30% lower than that of traditional Pd / Al2O3 catalysts. It exhibits excellent catalytic activity under complex conditions, including the individual oxidation of nitrous oxide-ammonia-SCR reaction and the presence of NO. Furthermore, the Pd loading is only 0.5 wt.%, reducing the cost of precious metals. This invention represents a low-temperature, high-efficiency, stable, and reliable nitrogen oxide purification catalyst. Attached Figure Description

[0017] Figure 1: Comparison of selective catalytic reduction performance of Pd / F-Al2O3 and traditional Pd / Al2O3 for nitrous oxide ammonia; Figure 2: Comparison of the selective catalytic reduction performance of Pd / F-Al2O3 and traditional Pd / Al2O3 in the presence of NO. Detailed Implementation

[0018] To facilitate understanding of the present invention, the technical solutions described below are further illustrated with specific embodiments. These examples are for illustrative purposes only and are not limited to this scope. Operations not specifically described in the following embodiments are generally performed under conventional conditions or according to the product instructions. Chemical reagents not specifying manufacturers are all conventional pharmaceuticals that comply with national standards and are available on the market.

[0019] Example 1 Weigh an appropriate amount of basic aluminum acetate (Al(CH3COO)2(OH)) and spread it evenly in a boat-shaped alumina crucible. Place the crucible in a tube furnace. Close the tube furnace and introduce argon gas as a protective gas. After ensuring that the air in the furnace is completely purged, raise the temperature from room temperature to 400℃ at a rate of 5℃ / min, and maintain the temperature for 4 hours after reaching the target temperature. After the reaction is complete, stop heating and allow it to cool naturally to room temperature. Remove the F-Al2O3 support. Accurately weigh 10g of the prepared F-Al2O3 support and place it in a beaker. Separately, take 0.128g of palladium nitrate hydrate (Pd(NO3)2·2H2O), dissolve it in an appropriate amount of deionized water, and prepare a homogeneous palladium nitrate aqueous solution. Slowly add the palladium nitrate aqueous solution dropwise to the beaker containing the F-Al2O3 support while stirring to ensure that the support is fully wetted, completing the initial wet impregnation. Transfer the impregnated mixture to a centrifuge tube and centrifuge to remove excess water. After centrifugation, the precipitate was removed and placed in an oven to dry at 383 K (110 °C) for 12 hours to obtain a dried solid sample. The dried solid sample was then placed in a muffle furnace and heated to 773 K (500 °C) under atmospheric pressure and air atmosphere, and calcined at this temperature for 2 hours. After calcination, the sample was naturally cooled to room temperature to obtain a Pd / F-Al2O3 catalyst with a Pd mass fraction of 0.5 wt.%.

[0020] Example 2 Using the same loading and preparation process as in the examples, except that the support was replaced with a common Al2O3 support that had not undergone argon high-temperature treatment, a conventional Pd / Al2O3 catalyst was prepared, wherein the mass fraction of Pd was 0.5 wt.%.

[0021] The activity test results of the samples in Example 1 and Comparative Example 1 of this invention are as follows: Figure 1 As shown in the figure, for the same content, different supports significantly affect the catalytic activity of nitrous oxide removal, with Pd / F-Al2O3 > Pd / Al2O3. Modification of the support, by increasing unsaturated oxygen vacancies, strengthens the support-metal interaction, which is considered the reason for this result.

[0022] Figure 2 The figure shows the activity test curves of Example 1 and Comparative Example 1 after the addition of NO. As shown in the figure, the activities of the catalysts prepared before and after support modification differ after the addition of NO, with Pd / F-Al2O3 > Pd / Al2O3. This indicates that the strong support-metal interaction after support modification is less inhibited by NO, thus maintaining high catalytic performance.

[0023] Combination Figure 1 and Figure 2It can be seen that the Pd / F-Al2O3 sample prepared by this invention has higher catalytic nitrous oxide removal activity than the comparative example, and the nitrous oxide removal rate reaches 90% at 230℃, which has broad prospects for industrial application.

[0024] The above description is only a preferred embodiment of the present invention. Any equivalent changes and modifications made by those skilled in the art within the scope of the patent application of the present invention shall also fall within the scope covered by the appended claims.

Claims

1. A Pd / F-Al2O3 catalyst with strong metal-support interaction, wherein the catalyst uses F-Al2O3 as the support and Pd as the active component, characterized in that, The mass fraction of Pd is 0.5 wt.%; the F-Al2O3 support is rich in F centers with free electron oxygen vacancies and has five-coordinate aluminum ion centers on its surface; the five-coordinate aluminum ion centers are used to fix Pd atoms and form a strong metal-support interaction.

2. The Pd / F-Al2O3 catalyst with strong metal-support interaction according to claim 1, characterized in that... The catalyst has a particle size of 40-60 mesh.

3. A method for preparing a Pd / F-Al2O3 catalyst with strong metal-support interaction as described in claim 1 or 2, characterized in that... Includes the following steps: Step S1, Preparation of F-Al2O3 support: The precursor is placed in a boat-shaped alumina crucible, placed in a tube furnace, heated to a specific temperature at a fixed heating rate under an inert gas atmosphere, and held at that temperature for a period of time. After natural cooling, F-Al2O3 support is obtained. Step S2, initial wet impregnation with Pd: A certain amount of the F-Al2O3 support obtained in step S1 is added to an aqueous solution prepared from nitrate hydrate for initial wet impregnation. Step S3, centrifugation and drying: The mixture obtained in step S2 is centrifuged and then dried at a specific temperature; Arrangement S4, calcination and shaping: The sample dried in step S3 is placed in a calcination atmosphere and calcined under specific temperature and pressure conditions to obtain the Pd / F-Al2O3 catalyst.

4. The method for preparing the Pd / F-Al2O3 catalyst according to claim 3, characterized in that... In step S1, the precursor is basic aluminum acetate; the inert gas in the tube furnace is argon; the heating rate is 5℃ / min, the final temperature is 400℃, and the holding time is 4 hours.

5. The method for preparing the Pd / F-Al2O3 catalyst according to claim 3, characterized in that... In step S2, the amount of the F-Al2O3 support is 10g; the amount of the nitrate hydrate is Pd(NO3)2·2H2O, which is 0.128g; the impregnation method is initial wet impregnation, and the solvent is water.

6. The method for preparing the Pd / F-Al2O3 catalyst according to claim 3, characterized in that... In step S3, the drying temperature is 383K and the drying time is 12 hours.

7. The method for preparing the Pd / F-Al2O3 catalyst according to claim 3, characterized in that... In step S4, the calcination atmosphere is air, and the pressure is atmospheric pressure; the calcination temperature is 773K, and the calcination time is 2 hours.

8. The method for preparing the Pd / F-Al2O3 catalyst according to claim 3, characterized in that... The Pd / F-Al2O3 catalyst has a Pd mass fraction of 0.5 wt.%.

9. The application of a catalyst according to any one of claims 1 to 3 or a catalyst prepared by the method according to any one of claims 4 to 8, characterized in that... The catalyst is used for the selective catalytic reduction reaction of nitrous ammonia.

10. The application of the catalyst according to claim 9, characterized in that... The selective catalytic reduction reaction of nitrous oxide ammonia includes a single selective catalytic reduction reaction of nitrous oxide ammonia and a selective catalytic reduction reaction of nitrous oxide ammonia in the presence of NO.

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