A silicon poisoning-resistant catalyst and its preparation method

Abstract

The present invention relates to a silicon poisoning-resistant catalyst and a preparation method thereof in the field of catalysts, including: S1, immersing high-aluminum ceramic fiber cotton in a zirconium acetate solution for aging treatment, and forming a carrier of three-dimensional reticulated ceramic fiber cotton through filtration, drying, and roasting; S2, placing the carrier prepared in step S1 in a mixed solution of manganese nitrate and cerium nitrate, and forming an intermediate through vacuum drying and roasting; S3, placing the intermediate prepared in step S2 in a closed container, evacuating the air and then injecting copper sol for pressure maintaining treatment, and drying and activating after centrifugally removing the excess sol on the surface of the intermediate to form a structure with transition metal oxides loaded on the fiber surface of three-dimensional reticulated ceramic fiber cotton, and the transition metal oxides are MnO x -CeO2-CuO. When the catalyst prepared by the present invention is used to treat silane waste gas at 350 °C, its service life can reach more than 5 times that of traditional catalysts, and it has significant economic benefits.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation, and specifically, to a silicon poisoning-resistant catalyst and a preparation method thereof. Background Art

[0002] In the manufacture of silicone compounds, substances such as siloxane, isopropanol, methyl chloride, and methanol will volatilize or be generated during chemical reaction stages such as synthesis and polycondensation. For example, organic compounds such as siloxane volatilize due to the high-temperature conditions of the polymerization reaction. The silicone waste gas contains harmful substances such as volatile organic compounds (VOC s ), chlorine, silane, etc., which may cause problems such as respiratory tract irritation and skin allergies. Long-term exposure to such waste gas may cause chronic damage to the nervous system, liver, and kidneys, and even increase the risk of cancer. At high temperatures, silicone volatilizes more rapidly and may enter the human body through the air, resulting in symptoms such as headache, insomnia, and decreased liver and kidney function.

[0003] During the catalytic oxidation of silicone compounds, SiO2 will be deposited, resulting in the coverage of the active sites of the catalyst (referred to as silicon poisoning). For traditional catalysts such as Pt honeycomb catalysts, the specific surface area of the honeycomb ceramic used as the carrier is usually <50 m² / g, and the silicon deposits are likely to block the pores, resulting in a service life of the catalyst often less than 200 hours. Those skilled in the art have made further explorations. Using ceramic fiber as the carrier, taking advantage of the characteristics of the large specific surface area and high porosity of the fiber cotton. For example, the publication number CN103806990A discloses a preparation method of an automotive exhaust gas processor with a ceramic fiber catalyst carrier. In distilled water, inorganic salts of cerium, zirconium, lanthanum, strontium, and cobalt are added and stirred evenly to obtain a catalyst aqueous solution. In the catalyst aqueous solution, a sol-forming agent is added and stirred evenly, and then a colloidal particle suspending agent is added to obtain a stable catalyst sol. The ceramic fiber cotton column is immersed in the catalyst sol to obtain a ceramic fiber cotton column with a catalyst colloid adhered to the surface; then, after drying and calcination, a ceramic fiber cotton column carrying the catalyst is obtained and installed in a metal shell with an inner insulation layer, thus obtaining an automotive exhaust gas purifier. This patented technology has achieved certain results using ceramic fiber as the carrier compared to using honeycomb ceramic as the carrier. However, with the simple impregnation process, it is easy to have poor adhesion between the catalyst and the ceramic fiber. Therefore, sintering at a high temperature of 800 - 1200 degrees is required to obtain a better loading effect. However, the nano-catalyst is prone to high-temperature deactivation at a high temperature of 800 - 1200 degrees, resulting in a decline in catalytic performance and a poor service life of the catalyst. Summary of the Invention

[0004] Aiming at the defects in the prior art, the purpose of the present invention is to provide a silicon poisoning-resistant catalyst and a preparation method thereof.

[0005] According to the present invention, a preparation method of a silicon poisoning-resistant catalyst includes:

[0006] S1. Immerse the high-aluminum ceramic fiber cotton in a zirconium acetate solution for aging treatment, and form a carrier of three-dimensional network ceramic fiber cotton composed of Al2O3 - SiO2 - ZrO2 composite oxide through filtration, drying, and roasting.

[0007] S2. Place the carrier prepared in step S1 in a mixed solution of manganese nitrate and cerium nitrate, and form an intermediate through vacuum drying and roasting. The intermediate is a carrier with a MnO x -CeO2 primary active layer on the fiber surface.

[0008] S3. Place the intermediate prepared in step S2 in a closed container, evacuate the air, inject copper sol, and perform pressure-holding treatment. After centrifuging to remove the excess sol on the surface of the intermediate, perform drying and activation treatment to form a structure with transition metal oxides loaded on the fiber surface of the three-dimensional network ceramic fiber cotton. The transition metal oxides are MnO x -CeO2 - CuO.

[0009] In some embodiments, in step S1, nitric acid is added to the zirconium acetate solution as a hydrolysis catalyst.

[0010] In some embodiments, in step S1, the fiber diameter of the carrier is 3 - 10 μm, the porosity is ≥85%, and the BET specific surface area is 200 - 500 m² / g.

[0011] In some embodiments, in step S1, the mass ratio of aluminum to silicon in the high-aluminum ceramic fiber cotton is 6:3.

[0012] In some embodiments, in step S1, the mass ratio of aluminum, silicon, and zirconium in the carrier is 6:3:1.

[0013] In some embodiments, in step S2, manganese nitrate (Mn(NO3)2·4H2O) and cerium nitrate (Ce(NO3)3·6H2O) are mixed in a molar ratio of Mn:Ce = 4:1 and then formulated into a solution with deionized water.

[0014] In some embodiments, in step S3, the copper sol is formed by dissolving Cu(NO3)2·3H2O and citric acid in ethanol at a molar ratio of 1:1.2 and refluxing at a predetermined temperature to form a transparent sol.

[0015] In some embodiments, in step S3, the drying and activation are carried out as follows: Dry the intermediate with the excess sol removed on the surface at a temperature of 120°C for 2 h, then heat it to 600°C at a rate of 5°C / min, and reduce it in a mixed gas of hydrogen and nitrogen for 2 h. In the mixed gas of hydrogen and nitrogen, the volume ratio of hydrogen is 5%.

[0016] The present invention also provides a silicon poisoning-resistant catalyst, which comprises a transition metal oxide supported on a carrier;

[0017] The transition metal oxide is MnO x -CeO2-CuO, and the mass fraction of the transition metal oxide is 15-20%;

[0018] The carrier is a three-dimensional network ceramic fiber cotton composed of Al2O3-SiO2-ZrO2 composite oxide. The fiber diameter of the three-dimensional network ceramic fiber cotton is 3-10 μm, the porosity is ≥85%, and the BET specific surface area is 200-500 m² / g.

[0019] In some embodiments, the mass ratio of aluminum, silicon, and zirconium in the carrier is 6:3:1.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The structure of the catalyst prepared by the present invention is that the transition metal oxide is supported on the surface of the fibers of the three-dimensional network ceramic fiber cotton. The catalyst on the fiber surface preferentially converts organosilicon into silicon dioxide particles with a particle size of 0.1-1 μm, and uses the large specific surface area to provide a silicon deposition capacity 5-10 times that of the traditional catalyst. At the same time, the fiber network structure has a filtration interception rate of more than 90% for silicon deposits, realizing the dynamic interception and capacity buffering of silicon deposits, and improving the performance of the catalyst as a pretreatment agent. When treating silane waste gas at 350 °C, the service life of this catalyst can reach more than 5 times that of the traditional catalyst, with significant economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] By reading the following detailed description of non-limiting embodiments with reference to the accompanying drawings, other features, objects, and advantages of the present invention will become more apparent:

[0023] Figure 1 It is a comparison chart of the silicon poisoning-resistant catalytic performance of the present invention and the catalytic performance of a honeycomb ceramic carrier;

[0024] Figure 2 It is a schematic electron microscope structure diagram of the three-dimensional network ceramic fiber cotton of the present invention;

[0025] Figure 3 It is a schematic electron microscope structure diagram of the transition metal oxide supported on the fiber surface of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The present invention will be described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several changes and improvements can still be made. These all belong to the protection scope of the present invention. Embodiment

[0027] This embodiment provides a method for preparing a silicon poisoning-resistant catalyst, which includes the following steps:

[0028] S1. Preparation of a three-dimensional reticulated ceramic fiber cotton support, which includes soaking with a precursor sol and high-temperature calcination, where:

[0029] The soaking with the precursor sol specifically includes:

[0030] S1-1. Dissolve zirconium acetate Zr(OCH2CH3)4 in deionized water to form a solution with a concentration of 10 wt%, add 0.1 mol / L nitric acid as a hydrolysis catalyst, and stir magnetically for 30 min;

[0031] S1-2. Immerse a high-aluminum type ceramic fiber cotton with a mass ratio of aluminum to silicon of 6:3 into the solution prepared in step S1-1, age at 60 °C for 12 h, then filter and dry to form a precursor. In this embodiment, the average fiber diameter of the high-aluminum type ceramic fiber cotton is about 5 μm.

[0032] The high-temperature calcination procedure specifically includes:

[0033] S1-3. First raise the precursor prepared in step S1-2 to 600 °C at a rate of 2 °C / min and hold for 2 hours, then raise it to 1200 °C at a rate of 5 °C / min and hold for 4 hours to obtain a three-dimensional reticulated ceramic fiber cotton support composed of an Al2O3-SiO2-ZrO2 composite oxide. The mass ratio of aluminum, silicon, and zirconium in the prepared support is 6:3:1. The fiber diameter of the prepared support is 3 - 10 μm, the porosity is ≥85%, and the BET specific surface area is 200 - 500 m² / g.

[0034] S2. Preparation of an intermediate, which specifically includes:

[0035] S2-1. Mix manganese nitrate (Mn(NO3)2·4H2O) and cerium nitrate (Ce(NO3)3·6H2O) in a molar ratio of Mn:Ce = 4:1, and prepare a 0.5 mol / L solution with deionized water;

[0036] S2-2. Immerse the support prepared in step S1 into the solution formed in step S2-1, ultrasonically treat it at a power of 200 W for 30 min, and then vacuum dry it at 80 °C for 6 h;

[0037] S2-3. Heat the structure prepared in step S2-2 to 400 °C at a rate of 3 °C / min and then hold for 3 h to form an intermediate, which is a structure with a MnO x -CeO2 initial active layer on the fiber surface of the three-dimensional network ceramic fiber cotton carrier.

[0038] S3. Load the transition metal oxide on the carrier, specifically including:

[0039] S3-1. Dissolve Cu(NO3)2·3H2O and citric acid in ethanol at a molar ratio of 1:1.2 and reflux at 60 °C for 4 h to form a transparent sol;

[0040] S3-2. Place the intermediate prepared in step S2 in a sealed container, evacuate to -0.08 MPa, and then inject the copper sol prepared in step S3-1, and keep the pressure for 30 min;

[0041] S3-3. Centrifuge the carrier prepared in step S3-2 at a speed of 2000 rpm for 2 min to remove the excess sol on the surface of the intermediate;

[0042] S3-4. Dry the intermediate with the copper sol on its surface prepared in step S3-3 at 120 °C for 2 h, then heat it to 600 °C at a rate of 5 °C / min and reduce it in a mixed gas of hydrogen and nitrogen for 2 h. In the mixed gas of hydrogen and nitrogen, the volume ratio of hydrogen is 5%, to form a structure with a transition metal oxide loaded on the fiber surface of the three-dimensional network ceramic fiber cotton, and the transition metal oxide is MnO x -CeO2-CuO, and the loading amount is about 18 wt%. Example

[0043] In this Example 2 compared with Example 1, the preparation steps of the carrier three-dimensional network ceramic fiber cotton are the same. The difference is that the loading step of the transition metal oxide adopts a one-step impregnation molding method. Specifically:

[0044] S1. This step is the same as step S1 in Example 1, and the process will not be elaborated here.

[0045] S2-1. Mix manganese nitrate (Mn(NO3)2·4H2O) and cerium nitrate (Ce(NO3)3·6H2O) at a molar ratio of Mn:Ce = 4:1, and prepare a 0.5 mol / L catalyst solution with deionized water;

[0046] S2-2. Add the transparent sol formed by dissolving Cu(NO3)2·3H2O and citric acid in ethanol at a molar ratio of 1:1.2 and refluxing at 60 °C for 4 h to the catalyst solution prepared in step S2-1, and stir evenly to form a sol;

[0047] S2-3. Immerse the three-dimensional network ceramic fiber cotton carrier prepared in step S1 into the sol in step S2-2 for 3-5 h to obtain three-dimensional network ceramic fiber cotton with a catalyst colloid adhered to its surface.

[0048] S2-4. Heat-treat the three-dimensional network ceramic fiber cotton with a catalyst colloid adhered to its surface obtained in step S2-3 to obtain three-dimensional network ceramic fiber cotton loaded with a catalyst. The catalyst is a transition metal oxide, and the transition metal oxide is MnO x -CeO2-CuO, and the loading amount is about 18 wt%.

[0049] This comparative example has the same process as step S2 in Example 2, except that in step S1 of this comparative example, the carrier is a honeycomb ceramic, and the honeycomb ceramic is 200-mesh cordierite.

[0050] Test conditions: Concentration of dimethylsilane is 1000 ppm, space velocity is 10000 h -1 , and temperature is 350 °C

[0051] Test results: See Table 1 below and Appendix Figure 2 :

[0052] Table 1

[0053] Test item Example 1 Example 2 Comparative example Initial conversion rate (350 °C) 98.2% 97.8% 98.5% Conversion rate after 1000 h 95.1% 77.3% <40% Silicon deposition capacity 21.7 g / 100 g catalyst 20.3 g / 100 g catalyst 3.2 g / 100 g catalyst

[0054] According to the test data in Table 1:

[0055] Compared with Example 2, the conversion rate of Example 1 is about 23% higher after 1000 h. The main difference between the two is that Example 1 uses stepwise impregnation, while Example 2 uses one-time impregnation. The main reason is that during the stepwise impregnation process, the MnO x -CeO2 active layer is first loaded onto the carrier to form a convex intermediate, and the subsequently loaded CUO can not only combine with the MnO x -CeO2 active layer, which not only increases the volume of the convex intermediate, but also can further form a composite active layer convex in the gaps between the convex intermediates, as Figure 3 shown, effectively increasing the amount of transition metal oxide on the carrier. Since the transition metal oxide on the carrier is in the shape of a convex, it correspondingly increases the surface area of the catalyst on the fiber surface of the carrier, thereby enabling higher reaction activity and more active sites, making the prepared catalyst more tolerant to silicon poisoning and improving the service life of the catalyst. In addition, the active components formed on the surface of the carrier by distributed impregnation can effectively ensure the active components due to the heating temperature during the heating process relative to one-time forming.

[0056] In Example 1, compared with the comparative example, the silicon deposition capacity is about 6.7 times that of the comparative example, and the conversion rate after 1000 h is about 2.4 times that of the comparative example. The main reason lies in that: the specific surface area of the three-dimensional network ceramic fiber cotton as the carrier has an order-of-magnitude increase compared with that of the honeycomb ceramic. For example, the specific surface area of the honeycomb ceramic in the comparative example is generally about 10 m² / g, while the specific surface area of the three-dimensional ceramic fiber cotton in Example 1 of this application is 200 - 500 m² / g. In addition, in the carrier with a specific ratio, the addition of zirconia can further increase the specific surface area by about 20%, increasing more contact areas to improve the adhesion of the catalyst, and can effectively enhance the high-temperature stability of the catalyst, enabling a silicon deposition capacity 5 - 10 times that of the traditional catalyst. Moreover, after continuous operation at high temperature for 1000 hours, the conversion rate is maintained >95%, and the pressure drop increase <30%, greatly improving the service life of the catalyst. In addition, the filtration interception rate of the fiber mesh structure for silicon deposits is above 90%, realizing the dynamic interception and capacity buffering of silicon deposits, and can effectively improve the performance of the catalyst as a pretreatment agent.

[0057] In summary, for the three-dimensional network ceramic fiber cotton prepared by the present invention, the fiber surface is loaded with transition metal oxides. The catalyst on the fiber surface preferentially converts organosilicon into silicon dioxide particles with a particle size of 0.1 - 1 μm, providing a silicon deposition capacity 5 - 10 times that of the traditional catalyst by using the large specific surface area. At the same time, the filtration interception rate of the fiber mesh structure for silicon deposits is above 90%, realizing the dynamic interception and capacity buffering of silicon deposits, and improving the performance of the catalyst as a pretreatment agent. When treating silane waste gas at 350 °C, the service life of this catalyst can reach more than 5 times that of the traditional catalyst, with significant economic benefits.

[0058] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. Without conflict, the embodiments of the present application and the features in the embodiments can be combined arbitrarily.

Claims

1. A preparation method of a silicon poisoning-resistant catalyst, characterized in that, Including: S1. Immerse high-alumina ceramic fiber cotton in a zirconium acetate solution for aging treatment, and form a carrier of three-dimensional network ceramic fiber cotton composed of Al2O3-SiO2-ZrO2 composite oxide through filtration, drying, and calcination. The fiber diameter in the carrier is 3-10 μm, the porosity is ≥85%, and the BET specific surface area is 200-500 m² / g. S2. Place the carrier prepared in step S1 into a mixed solution of manganese nitrate and cerium nitrate, and form an intermediate through vacuum drying and calcination. The intermediate is a structure with a primary active layer loaded on the fiber surface of the carrier, and the primary active layer is MnO x -CeO2; S3. Place the intermediate prepared in step S2 in a closed container, evacuate the air, inject copper sol, and perform pressure-holding treatment. After centrifuging to remove the excess sol on the surface of the intermediate, perform drying and activation treatment to form a structure with transition metal oxides loaded on the fiber surface of the carrier, where the transition metal oxides are MnO x -CeO2-CuO.

2. The preparation method of the silicon poisoning resistant catalyst according to claim 1, characterized in that, In step S1, nitric acid is added to the zirconium acetate solution as a hydrolysis catalyst.

3. The preparation method of the silicon poisoning-resistant catalyst according to claim 1, characterized in that, In step S1, the mass ratio of aluminum to silicon in the high-alumina ceramic fiber cotton is 6:

3.

4. The preparation method of the silicon poisoning resistant catalyst according to claim 3, characterized in that, In step S1, the mass ratio of aluminum, silicon, and zirconium in the carrier is 6:3:

1.

5. The preparation method of the silicon poisoning resistant catalyst according to claim 1, characterized in that, In step S2, manganese nitrate (Mn(NO3)2·4H2O) and cerium nitrate (Ce(NO3)3·6H2O) are mixed according to a molar ratio of Mn:Ce = 4:1 and then prepared into a solution with deionized water.

6. The preparation method of the silicon poisoning-resistant catalyst according to claim 1, characterized in that, In step S3, the copper sol is formed by dissolving Cu(NO3)2·3H2O and citric acid in ethanol according to a molar ratio of 1:1.

2.

7. The preparation method of the silicon poisoning resistant catalyst according to claim 6, wherein In step S3, the drying and activation are carried out in the following manner: The intermediate with the excess sol on the surface removed is dried at a temperature of 120°C for 2 h, then heated to 600°C at a rate of 5°C / min and reduced in a mixed gas of hydrogen and nitrogen for 2 h, where the volume ratio of hydrogen in the mixed gas of hydrogen and nitrogen is 5%.

8. A catalyst resistant to silicon poisoning, characterized in that, Prepared by using the preparation method of the silicon-poisoning-resistant catalyst according to any one of claims 1-7, including transition metal oxides supported on a carrier; The transition metal oxide is MnO x -CeO2-CuO, and the mass fraction of the transition metal oxide is 15 to 20%; The carrier is a three-dimensional network ceramic fiber cotton composed of Al2O3-SiO2-ZrO2 composite oxide. The fiber diameter of the three-dimensional network ceramic fiber cotton is 3-10 μm, the porosity is ≥85%, and the BET specific surface area is 200-500 m² / g.

9. The anti-silicon poisoning catalyst according to claim 8, characterized in that, The mass ratio of aluminum, silicon, and zirconium in the carrier is 6:3:1.

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