Silicon-modified alumina-based catalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of catalysts, in particular to a silicon-modified alumina-based catalyst and a preparation method and application thereof.The silicon-modified alumina-based catalyst comprises carrier silicon-modified alumina and supported metal, the supported metal comprises a first component and a second component, the first component comprises Pt, and the second component comprises one or two of Fe and Cu. According to the silicon-modified alumina-based catalyst as well as the preparation method and application thereof, the dosage of noble metal is reduced, and the activity of the catalyst is improved by utilizing the synergistic effect of the first component and the second component.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and particularly to a silicon-modified alumina-based catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] Today, with the increasing emphasis on environmental protection, reducing industrial emissions, especially the emissions of harmful gases and particulate matters, has become a global urgent task. As an important inorganic material, alumina is widely used as a catalyst support or a catalyst itself due to its excellent physical and chemical properties, such as high specific surface area, good thermal stability, and chemical inertness. However, unmodified alumina has limited activity in certain specific catalytic reactions and is difficult to meet the requirements for efficient tail gas purification.

[0003] In the field of diesel engine tail gas treatment, traditional catalyst materials, such as noble metals like platinum (Pt) and palladium (Pd), although showing good catalytic activity, their high costs and limited resource reserves restrict their wide application. In addition, noble metal catalysts are prone to deactivation under high temperature and harsh environments, reducing the catalytic efficiency and service life. Therefore, it is particularly important to develop a low-cost and high-performance catalyst substitute.

[0004] In recent years, researchers have been committed to improving the catalytic activity of silicon-modified alumina-based catalysts to meet the requirements of the tail gas purification field. Silicon-modified alumina-based catalysts not only maintain the stability of alumina itself but also can significantly enhance the catalytic efficiency for specific chemical reactions by introducing specific active components or structural adjustments. For example, by methods such as surface modification, doping with other metal oxides, or forming composite oxides, the catalytic performance of alumina can be effectively improved.

[0005] However, there are still some challenges in the existing preparation technologies of silicon-modified alumina-based catalysts. On the one hand, how to achieve uniform distribution and high loading of active components while maintaining the stability of the alumina support is the key to improving catalytic activity. On the other hand, the harmful impurities or by-products that may be introduced during the modification process, as well as the control of the preparation cost, are also important factors restricting the wide application of silicon-modified alumina-based catalysts.

[0006] Therefore, the present invention proposes a novel silicon-modified alumina-based catalyst, a preparation method thereof, and an application thereof, aiming to achieve the preparation of a low-cost and high-activity catalyst through an optimized modification strategy and preparation process. This method can not only significantly improve the catalytic conversion efficiency of alumina for harmful substances in the tail gas but also reduce the production cost, providing a more economical and efficient solution for diesel engine tail gas purification. Summary of the Invention

[0007] Aiming at the deficiencies of the above-mentioned existing technologies, the purpose of the present invention is to provide a silicon-modified alumina-based catalyst, its preparation method and application, which can effectively improve the activity of the catalyst while reducing the content of precious metals in the catalyst.

[0008] In the first aspect, the present invention provides a silicon-modified alumina-based catalyst, which includes a carrier silicon-modified alumina and a supported metal. The supported metal includes a first component and a second component. The first component includes Pt, and the second component includes one or two of Fe and Cu.

[0009] Furthermore, the weight ratio of the carrier to the supported metal is 1000:1 - 5.

[0010] Furthermore, the preparation method of the silicon-modified alumina includes: mixing γ-Al2O3, polydimethylsiloxane and acetone and stirring to obtain a paste, standing to obtain a white powder, drying the white powder at 200 °C for 1 h, then calcining at 400 °C for 1 h, then calcining at 600 °C for 1 h, and finally calcining at 800 °C for 1 h to obtain it.

[0011] Furthermore, the dosage ratio of γ-Al2O3, polydimethylsiloxane and acetone is 5 g: 2.05 g: 10 mL.

[0012] Furthermore, the second component is Fe.

[0013] Furthermore, the second component is Cu.

[0014] Furthermore, the second component is Fe and Cu.

[0015] Furthermore, the molar ratio of the first component to the second component is 10:1 - 10.

[0016] Furthermore, the molar ratio of the first component to the second component is 10:1 - 5.

[0017] Furthermore, the molar ratio of the first component to the second component is 10:1 - 3.

[0018] In the second aspect, the preparation method of the silicon-modified alumina-based catalyst in the present invention includes the steps of: mixing and dispersing the silicon-modified alumina with water, dropping a supported metal solution into it and stirring to obtain a mixed solution, concentrating the mixed solution under reduced pressure, and then calcining at 400 - 500 °C to obtain the silicon-modified alumina-based catalyst.

[0019] Furthermore, the preparation method of the supported metal solution includes: adding tetraammineplatinum nitrate, copper sulfate pentahydrate and ferric chloride hexahydrate to water and stirring evenly to obtain it.

[0020] Further, the weight ratio of tetraammineplatinum nitrate, copper sulfate pentahydrate, and ferric chloride hexahydrate is (0.05 - 0.15):(0 - 0.04):(0 - 0.04).

[0021] Thirdly, the modified alumina-based catalyst of the present invention is applied to the catalytic oxidation of diesel exhaust.

[0022] The beneficial effects of the present invention are as follows: The modified alumina-based catalyst of the present invention uses silicon-modified alumina as the carrier, and the supported metal is at least two components. The first component is Pt, and the second component is one or both of Fe and Cu. This combination not only optimizes the structure of the catalyst, reduces the amount of precious metal used, but also utilizes the synergistic effect of the first component and the second component to improve the activity of the catalyst. Description of the Drawings

[0023] Figure 1 It is a scanning electron microscope image of the modified alumina-based catalyst B1 obtained in Preparation Example 1 of the present invention. Detailed Embodiments

[0024] The technical solutions of the present invention will be described clearly and completely below. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art without making creative efforts based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0025] The present invention provides a silicon-modified alumina-based catalyst, including a carrier of silicon-modified alumina and a supported metal. The supported metal includes a first component and a second component. The first component includes Pt, and the second component includes one or both of Fe and Cu; the weight ratio of the carrier to the supported metal is 1000:1 - 5; the molar ratio of the first component to the second component is 10:1 - 10.

[0026] Among them, the preparation method of the silicon-modified alumina includes: taking 5.0 g of γ-Al2O3 and placing it in a 100 mL crucible, adding a solution prepared from 2.05 g of polydimethylsiloxane with a viscosity of 620 centipoise and 10 mL of acetone, stirring at 25°C for 15 min, allowing the obtained paste to stand at room temperature for 4 hours to obtain a white powder; drying the above white powder at 200°C for 1 h, then calcining it at 400°C for 1 h, then calcining it at 600°C for 1 h, and finally calcining it at 800°C for 1 h to obtain it.

[0027] The polydimethylsiloxane has the following structure:

[0028] Among them, in the polydimethylsiloxane, R1, R2, and R3 are all methyl groups, m is 8, and n is zero.

[0029] The present invention provides a method for preparing a silicon-modified alumina-based catalyst. The steps include: mixing and dispersing silicon-modified alumina with water, dropping a metal-loaded solution into it and stirring to obtain a mixed solution, concentrating the mixed solution under reduced pressure, and then calcining at 400-500 °C to obtain the silicon-modified alumina-based catalyst.

[0030] Among them, the preparation steps of the metal-loaded solution include: adding 100 ml of pure water into a three-necked flask, then adding platinum(II) diamine nitrate, copper sulfate pentahydrate, and iron(III) chloride hexahydrate, and stirring evenly to prepare a solution of the metal-loaded solution; the weight ratio of platinum(II) diamine nitrate, copper sulfate pentahydrate, and iron(III) chloride hexahydrate is (0.05-0.15):(0-0.04):(0-0.04).

[0031] The batch details of preparing the metal-loaded solution by the foregoing preparation method are shown in the following table:

[0032] Preparation Example 1 Preparation of Modified Alumina-Based Catalyst B1 Add 20 g of silicon-modified alumina powder into three-necked flask A, then add 100 ml of water, ultrasonically disperse for 60 min, and then add metal-loaded solution B1. The total amount of metal in the metal-loaded solution is 20 mg (the amount of metal-loaded solution B1 is 30.2 ml). Stir for 2 hours, and then concentrate under reduced pressure for 6 hours until no liquid comes out. Then calcine the obtained solid at 500 °C for 2 hours to obtain modified alumina-based catalyst B1.

[0033] Preparation Example 2 Preparation of Modified Alumina-Based Catalyst B2 Referring to the preparation of modified alumina-based catalyst B1 in Preparation Example 1, replace metal-loaded solution B1 with metal-loaded solution B2. In the used metal-loaded solution B2, the total amount of metal is 20 mg. Modified alumina-based catalyst B2 is prepared.

[0034] Preparation Example 3 Preparation of Modified Alumina-Based Catalyst B3 Referring to the preparation of modified alumina-based catalyst B1 in Preparation Example 1, replace metal-loaded solution B1 with metal-loaded solution B3. In the used metal-loaded solution B3, the total amount of metal is 20 mg. Modified alumina-based catalyst B3 is prepared.

[0035] Preparation Example 4 Preparation of Modified Alumina-Based Catalyst B4 Referring to the preparation of modified alumina-based catalyst B1 in Preparation Example 1, replace metal-loaded solution B1 with metal-loaded solution B4. In the used metal-loaded solution B4, the total amount of metal is 20 mg. Modified alumina-based catalyst B4 is prepared.

[0036] Preparation Example 5 Preparation of Modified Alumina-based Catalyst C2 Referring to the preparation of the modified alumina-based catalyst B1 in Preparation Example 1, replace the metal loading solution B1 with the metal loading solution C2. In the used metal loading solution C2, the total amount of metal is 20 mg. The modified alumina-based catalyst C2 is prepared.

[0037] Preparation Example 6 Preparation of Modified Alumina-based Catalyst D2 Referring to the preparation of the modified alumina-based catalyst B1 in Preparation Example 1, replace the metal loading solution B1 with the metal loading solution D2. In the used metal loading solution D2, the total amount of metal is 20 mg. The modified alumina-based catalyst D2 is prepared.

[0038] Comparative Preparation Example 1 Referring to the preparation of the modified alumina-based catalyst B1 in Preparation Example 1, replace the metal loading solution B1 with the metal loading solution E2. In the used metal loading solution E2, the total amount of metal is 20 mg. The modified alumina-based catalyst E2 is prepared.

[0039] Application Examples and Comparative Examples: A mixed gas containing CO, NO, H2O, O2, and N2 is introduced into a tubular furnace, where CO: 600 ppm, NO: 600 ppm, H2O: 5%, O2: 10%, with N2 as the balance gas, and the space velocity is 20,000 / h. First, adjust each gas, connect them to a gas mixing tank, and stabilize them to the set values as the initial emission data for calculating the conversion rate. Then, connect the uniformly mixed gas to the tubular furnace containing the catalyst and start heating from 50 °C to 500 °C at a heating rate of 5 °C / min. Record the values of each gas after passing through the catalyst at a rate of 2 s / each time and calculate the conversion rate.

[0040] The Fourier transform infrared spectrometer used in this test is: MKS Multigas2030HS.

[0041]

[0042] According to Application Examples 1-4, as the proportion of the first component increases, the performance of catalyzing CO first increases and then decreases. For the modified alumina-based catalyst B3 used in Application Example 3, the molar ratio of the first component Pt to the second components (Cu and Fe) is 10:3, and its performance is relatively excellent.

[0043] From Application Examples 1-4, as the proportion of the first component increases, the performance of catalyzing NO decreases. For the modified alumina-based catalyst B1 used in Application Example 1, the molar ratio of the first component Pt to the second components (Cu and Fe) is 10:10, and its performance is relatively excellent.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the present invention rather than limiting the technical solutions described in the present invention; those of ordinary skill in the art should understand that the present invention can still be modified or equivalently replaced; and all technical solutions and their improvements that do not depart from the spirit and scope of the present invention should be covered by the scope of the claims of the present invention.

Claims

1. A silicon-modified alumina-based catalyst, characterized in that, It includes a carrier of silicon-modified alumina and a supported metal. The supported metal includes a first component and a second component. The first component includes Pt, and the second component includes one or both of Fe and Cu.

2. The silicon-modified alumina-based catalyst according to claim 1, characterized in that, The weight ratio of the carrier to the supported metal is 1000:1 - 5.

3. The silica-modified alumina-based catalyst according to claim 1, characterized in that, The preparation method of the silicon-modified alumina includes: mixing γ-Al2O3, polydimethylsiloxane, and acetone and stirring to obtain a paste, allowing it to stand to obtain a white powder, drying the white powder at 200°C for 1 h, then calcining it at 400°C for 1 h, then calcining it at 600°C for 1 h, and finally calcining it at 800°C for 1 h to obtain it.

4. A silicon-modified alumina-based catalyst according to claim 3, characterized in that, The dosage ratio of the γ-Al2O3, polydimethylsiloxane, and acetone is 5 g: 2.05 g: 10 mL.

5. A silicon-modified alumina-based catalyst according to claim 1, characterized in that, The molar ratio of the first component to the second component is 10:1 - 10.

6. A method for preparing a silicon-modified alumina-based catalyst according to any one of claims 1-5, characterized in that the steps It includes: Mixing and dispersing the silicon-modified alumina with water, dropping a supported metal solution into it and stirring to obtain a mixed solution, concentrating the mixed solution under reduced pressure, and then calcining it at 400 - 500°C to obtain the silicon-modified alumina-based catalyst.

7. The preparation method of the silicon-modified alumina-based catalyst according to claim 6, characterized in that, The preparation method of the supported metal solution includes: adding tetraammineplatinum nitrate, copper sulfate pentahydrate, and ferric chloride hexahydrate to water and stirring evenly to obtain it.

8. The preparation method of the silicon-modified alumina-based catalyst according to claim 7, characterized in that, The weight ratio of the tetraammineplatinum nitrate, copper sulfate pentahydrate, and ferric chloride hexahydrate is (0.05 - 0.15):(0 - 0.04):(0 - 0.04).

9. Application of a silicon-modified alumina-based catalyst as described in any one of claims 1 - 5 in the catalytic oxidation of diesel exhaust gas.

Images