Perovskite-loaded Pd-based catalyst as well as preparation method and application thereof

Abstract

The invention relates to a perovskite-loaded Pd-based catalyst as well as a preparation method and application thereof. The preparation method comprises the following steps: step 1, performing reduction pretreatment on perovskite oxide powder; 2, the pretreated powder is soaked in a solution containing a Pd precursor, and then drying is conducted; and 3, carrying out calcination treatment on the dried solid to obtain the perovskite-loaded Pd-based catalyst. The key point of the invention is to perform reduction pretreatment on a perovskite carrier, regulate and control the dispersion degree of Pd species on the surface of the catalyst and the interaction of the Pd species and the perovskite carrier, and finally, the perovskite-loaded Pd-based catalyst is invented. Pd is loaded on the surface of the perovskite oxide in a direct and effective mode, and compared with a traditional perovskite-loaded Pd catalyst, the perovskite-loaded Pd-based catalyst has high catalytic activity and high sulfur resistance and is a stable and efficient CO oxidation catalyst.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalytic oxidation removal of gaseous pollutants, and specifically relates to a perovskite-supported Pd-based catalyst, a preparation method thereof, and uses thereof. Background Art

[0002] Carbon monoxide (CO), a major atmospheric pollutant, is widely sourced from industrial combustion, automobile exhaust, and chemical production processes. Its high toxicity poses a serious threat to human health and the ecological environment. Therefore, the development of efficient and stable CO purification technologies is crucial. Catalytic oxidation, with its advantages of mild reaction conditions and high conversion efficiency, is considered one of the most promising methods for CO removal.

[0003] Precious metal palladium (Pd)-based catalysts are widely used due to their excellent catalytic oxidation activity. Among various common catalyst supports, perovskite oxide (ABO3) has attracted widespread attention due to its tunable composition, high oxygen mobility, good thermal stability, low cost, and strong adaptability to supported elements, and is considered an ideal catalyst support. However, the traditional two types of perovskite Pd loading methods have inherent drawbacks:

[0004] In the prior art, some methods directly introduce Pd precursors (such as palladium nitrate and palladium chloride) during the perovskite synthesis stage, hoping to achieve good interaction between Pd and the perovskite support, thereby achieving better stability and impurity tolerance. However, during the calcination stage, Pd ions can easily diffuse into the perovskite lattice through the solid phase, occupying the B site to form a doped structure. This deep doping causes Pd to be locked in the perovskite bulk phase, making it difficult to expose to the surface to form active sites. Since the Pd active center is wrapped by the dense perovskite lattice and cannot directly contact the reactant molecules, the catalytic activity is significantly reduced. This also causes the Pd / perovskite catalysts synthesized by this method to face the problem of "high loading and low utilization", and the actual application value is relatively limited.

[0005] Another part of the method mainly loads the Pd precursor on the surface of the perovskite support by impregnation or deposition. However, the untreated perovskite surface lacks anchoring sites, which makes the Pd particles easily migrate and agglomerate during the calcination process, forming large-sized particles, resulting in a significant reduction in the number of surface active sites. In addition, due to the weak interaction between Pd and the perovskite support, the electron transfer between Pd and the perovskite is limited, making it difficult to form a synergistic effect to weaken the sulfur adsorption strength, resulting in SO2 easily attacking the Pd active sites directly, and ultimately forming stable sulfate species, poisoning the Pd active center. In addition, the preparation of existing highly dispersed Pd catalysts mostly relies on precision technologies such as template method and atomic layer deposition, which require multi-step processing and demanding equipment requirements, resulting in a long production cycle, extremely high cost, and difficulty in large-scale application. Summary of the Invention

[0006] In view of the above problems, the object of the present invention is to provide a perovskite-loaded Pd-based catalyst having high Pd utilization, strong anti-poisoning ability and simplified process, as well as a preparation method and use thereof.

[0007] To achieve the above object, the present invention provides a method for preparing a perovskite-supported Pd-based catalyst, comprising the following steps:

[0008] Step 1: pre-treating the perovskite oxide powder by reduction;

[0009] Step 2: Immersing the pretreated powder in a solution containing a Pd precursor and then drying;

[0010] Step 3: calcining the dried solid to obtain a perovskite-supported Pd-based catalyst;

[0011] Furthermore, the composition of the perovskite oxide in step 1 is ABO3, wherein A represents one or a combination of two or more rare earth and alkaline earth metal elements; B represents one or a combination of two or more transition metal elements, and the particle size of the perovskite oxide powder is less than 0.1 mm.

[0012] Furthermore, the reduction pretreatment in step 1 refers to heating the perovskite oxide powder in a hydrogen atmosphere or a mixed gas atmosphere of hydrogen and inert gas, with a heating temperature of 100 to 1000° C. and a heating time of 0.5 to 5 hours, followed by natural cooling; wherein the inert gas is one or more of nitrogen, argon, and helium.

[0013] Furthermore, the Pd precursor in step 2 is palladium acetylacetonate, palladium acetate, palladium nitrate or palladium chloride, and the concentration of the Pd precursor solution is 0.1 to 10 mmol / L.

[0014] Furthermore, the solvent in the solution containing the Pd precursor in step 2 is one or more solutions of ethanol, acetone, acetylacetone, tetrahydrofuran or water.

[0015] Furthermore, during the impregnation process described in step 2, the ratio of the mass of the perovskite oxide to the volume of the solution containing the Pd precursor is 100-1000 g (perovskite) / L (impregnation solution), the impregnation temperature is 5-50° C., and the impregnation time is 1-30 h.

[0016] Furthermore, the drying process in step 2 refers to drying at 50-100° C. for 1-40 hours.

[0017] Furthermore, the calcination treatment in step 3 refers to calcination at 250-600° C. for 1-10 hours.

[0018] Furthermore, the calcination process in step 3 is carried out in an air atmosphere, an inert gas atmosphere, or a mixed gas atmosphere of air and inert gas; wherein the inert gas is one or more of nitrogen, argon, and helium.

[0019] To achieve the above object, the present invention provides a perovskite-supported Pd-based catalyst prepared by the above preparation method.

[0020] Furthermore, the mass proportion of the Pd element detected by the ICP method on the surface of the perovskite-supported Pd-based catalyst is 0.01-2%.

[0021] To achieve the above objectives, the present invention provides a use of the above-mentioned perovskite-supported Pd-based catalyst as a catalyst in the catalytic oxidation of CO.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] 1) The present invention achieves a synergistic improvement in catalyst activity and stability by innovatively introducing a "perovskite reduction pretreatment" step.

[0024] 2) This invention directly and efficiently loads Pd onto the surface of perovskite oxide. Compared with traditional perovskite-supported Pd catalysts, the present perovskite-supported Pd-based catalyst improves Pd utilization efficiency, exhibits high catalytic activity, and exhibits high sulfur tolerance, making it a stable and efficient CO oxidation catalyst. This overcomes the issues of low Pd utilization efficiency and susceptibility to deactivation in atmospheres containing impurities such as SO2 in conventional perovskite-supported Pd catalysts.

[0025] 3) The preparation method of the perovskite-supported Pd-based catalyst of the present invention has simple steps, is easy to operate, and is easy to produce on a large scale. The Pd utilization efficiency is high, and the prepared perovskite-supported Pd-based catalyst has high activity and good impurity tolerance, which can save a lot of costs for industrial production.

[0026] 4) The perovskite-supported Pd-based catalyst of the present invention can be used to purify gaseous pollution such as CO, providing a guarantee for the development of CO catalytic oxidation technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a performance test chart of the catalytic oxidation of CO by the samples obtained in Examples 1 and 2 of the present invention and the sample in Comparative Example 1.

[0028] Figure 2 This is a curve chart of the CO catalytic stability test of the sample in Example 1 of the present invention under a sulfur-containing atmosphere. DETAILED DESCRIPTION

[0029] The present invention will be described in further detail below with reference to specific embodiments.

[0030] In the description of the present invention, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0031] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0032] Example 1:

[0033] Step 1: The perovskite oxide powder with a chemical formula of SrTiO3 is subjected to reduction pretreatment in a 4% H2 / N2 atmosphere at a reduction temperature of 850°C for 2 hours, and then naturally cooled to room temperature.

[0034] Step 2: Immerse the pretreated perovskite oxide powder in a solution containing a palladium precursor (Pd) (1.524 mmol / L palladium acetylacetonate in acetylacetone). The perovskite oxide mass to Pd precursor solution volume ratio is 500 g (perovskite) / L (impregnation solution). The immersion temperature is 25°C for 5 hours. The powder is then dried at 40°C for 24 hours.

[0035] Step 3: The dried solid was calcined at 800° C. for 2 h in an air atmosphere to obtain a perovskite-supported Pd-based catalyst, which is denoted as Example 1. ICP characterization results showed that the loading mass percentage of Pd in ​​the catalyst was 0.048 wt %.

[0036] Example 2:

[0037] Step 1: The perovskite oxide powder with a chemical formula of SrTiO3 is subjected to reduction pretreatment in a 4% H2 / N2 atmosphere at a reduction temperature of 450°C for 2 hours, and then naturally cooled to room temperature.

[0038] Step 2: Immerse the pretreated perovskite oxide powder in a solution containing a palladium precursor (Pd) (1.524 mmol / L palladium acetylacetonate in acetylacetone). The perovskite oxide mass to Pd precursor solution volume ratio is 500 g (perovskite) / L (impregnation solution). The immersion temperature is 25°C for 5 hours. The powder is then dried at 40°C for 24 hours.

[0039] Step 3: The dried solid was calcined at 800° C. for 2 h in an air atmosphere to obtain a perovskite-supported Pd-based catalyst, which is denoted as Example 2. ICP characterization results showed that the loading mass percentage of Pd in ​​the catalyst was 0.047 wt %.

[0040] Comparative Example 1:

[0041] Step 1: Perovskite oxide powder with the chemical formula SrTiO3 is not subjected to any reduction pretreatment.

[0042] Step 2: The untreated perovskite oxide powder was immersed in a solution containing a Pd precursor, wherein the Pd precursor solution was a solution of 1.524 mmol / L palladium acetylacetonate in acetylacetone. The ratio of the perovskite oxide mass to the Pd precursor solution volume was 500 g (perovskite) / L (immersion solution). The immersion temperature was 25°C for 5 hours. The powder was then dried at 40°C for 24 hours.

[0043] Step 3: The dried solid was calcined at 800° C. for 2 h in an air atmosphere to obtain a perovskite-supported Pd-based catalyst, which is denoted as Comparative Example 1. ICP characterization results showed that the loading mass percentage of Pd in ​​the catalyst was 0.051 wt %.

[0044] Figure 1 The samples obtained in Examples 1-3 of the present invention and the La in Comparative Example 1 0.6 Sr 0.4 Figure 3. Performance test of CoO3 sample catalytic oxidation of CO. Test conditions: Catalyst particles with a particle size of 0.075-0.1 mm were screened and selected for CO catalytic oxidation activity evaluation, 0.2 g catalyst, CO 6000 ppm, O2 15%, gas space velocity (GHSV) 90,000 mL h -1 g -1 .

[0045] from Figure 1 It can be seen that the CO conversion rates of Examples 1 and 2 samples at the same temperature are higher than that of the comparative example 1 sample, indicating that the perovskite-supported Pd catalyst prepared by this method has higher catalytic activity than the supported catalyst prepared by the traditional method.

[0046] Figure 2The stability test curve of the sample obtained in Example 1 of the present invention under a sulfur-containing atmosphere. Test conditions: Catalyst particles with a particle size of 0.075-0.11 mm were screened and selected for CO catalytic oxidation activity evaluation under a sulfur-containing atmosphere, 0.2 g catalyst, CO 6000 ppm, SO2 50 ppm, O2 15%, gas space velocity GHSV 90,000 mL h -1 g -1 , the reaction temperature is 250℃.

[0047] from Figure 2 It can be seen that after the SO2 atmosphere was introduced, the CO conversion rate of the sample in Example 1 remained above 95% after 50 hours of reaction. This result shows that the perovskite-loaded Pd-based catalyst prepared by this method has good sulfur resistance.

[0048] The present invention has been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above-described embodiments. Various modifications may be made within the scope of knowledge of those skilled in the art without departing from the spirit of the present invention. Many other changes and modifications that do not depart from the spirit and scope of the present invention should be considered within the scope of protection of the present invention.

[0049] In the description of this specification, specific features, structures, materials or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0050] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for preparing a perovskite-supported Pd catalyst, characterized in that: The following steps are involved: Step 1: pre-treating the perovskite oxide powder by reduction; Step 2: Immersing the pretreated powder in a solution containing a Pd precursor and then drying; Step 3: calcining the dried solid to obtain a perovskite-supported Pd-based catalyst.

2. The method for preparing a perovskite-supported Pd catalyst according to claim 1, wherein: The composition of the perovskite oxide in step 1 is ABO3, wherein A represents one or a combination of two or more rare earth and alkaline earth metal elements; B represents one or a combination of two or more transition metal elements, and the particle size of the perovskite oxide powder is less than 0.1 mm.

3. The method for preparing a perovskite-supported Pd catalyst according to claim 1, wherein: The reduction pretreatment in step 1 refers to heating the perovskite oxide powder in a hydrogen atmosphere or a mixed gas atmosphere of hydrogen and inert gas, with a heating temperature of 100 to 1000° C. and a heating time of 0.5 to 5 hours, followed by natural cooling; wherein the inert gas is one or more of nitrogen, argon, and helium.

4. The method for preparing a perovskite-supported Pd catalyst according to claim 1, wherein: The Pd precursor in step 2 is palladium acetylacetonate, palladium acetate, palladium nitrate or palladium chloride, and the concentration of the Pd precursor solution is 0.1 to 10 mmol / L.

5. The method for preparing a perovskite-supported Pd catalyst according to claim 1, wherein: The solvent in the solution containing the Pd precursor in step 2 is one or more solutions of ethanol, acetone, acetylacetone, tetrahydrofuran or water.

6. The method for preparing a perovskite-supported Pd catalyst according to claim 1, wherein: During the impregnation process described in step 2, the ratio of the mass of the perovskite oxide to the volume of the solution containing the Pd precursor is 100-1000 g (perovskite) / L (impregnation solution), the impregnation temperature is 5-50° C., and the impregnation time is 1-30 h.

7. The method for preparing a perovskite-supported Pd catalyst according to claim 1, wherein: The calcination process in step 3 is carried out in an air atmosphere, an inert gas atmosphere, or a mixed gas atmosphere of air and inert gas; wherein the inert gas is one or more of nitrogen, argon, and helium.

8. A perovskite-supported Pd-based catalyst prepared by the preparation method according to any one of claims 1 to 7.

9. A perovskite-supported Pd-based catalyst according to claim 8, characterized in that: The mass proportion of the Pd element detected on the surface of the perovskite-supported Pd-based catalyst by the ICP method is 0.01-2%.

10. Use of the perovskite-supported Pd-based catalyst according to claim 8 in the catalytic oxidation of carbon monoxide.

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