Method for uniformly coating catalyst on integral foam material

Abstract

The invention belongs to the technical field of catalyst preparation, and particularly relates to a method for uniformly coating an integral foam material with a catalyst active component, which is suitable for catalyst manufacturing in the fields of chemical industry, environmental protection and energy. The invention discloses a method for uniformly coating a catalyst on an integral foam material. The method comprises the following steps: 1) preparing a precursor solution; 2) stirring the precursor solution and performing ultrasonic treatment; 3) dipping the integral foam material in the precursor solution, performing ultrasonic-assisted coating, and blowing away redundant liquid; 4) drying and quickly calcining; (5) repeatedly coating, namely repeating the step (3) and the step (4); and 6) finally calcining. Compared with the prior art, in the catalyst technology, the active components of the catalyst are uniformly distributed on the integral foam material and do not aggregate or fall off, so that the catalytic efficiency and the stability are improved; and through repeated coating, the loading capacity can be accurately controlled, and different application requirements can be met.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation technology, specifically relating to a method for uniformly coating catalyst active components on an integral foam material, applicable to catalyst manufacturing in the chemical, environmental protection and energy fields. Background Technology

[0002] Monolithic foam materials (such as metal or ceramic foams) exhibit great application potential in catalytic reactors due to their unique three-dimensional porous structure, low pressure drop, and excellent heat and mass transfer properties. They are particularly suitable for continuous flow, highly exothermic reaction processes, such as the catalytic oxidation of volatile organic compounds, partial oxidation of methane, and CO2 hydrogenation to methanol. Coating, as the most traditional and technologically mature loading method, offers advantages such as simple process, low cost, wide applicability, and the ability to easily achieve high catalyst loading by adjusting the solid content of the slurry. This process has low equipment requirements and is easily scaled up to industrial production.

[0003] For example, patent CN112999987A shows that FeCrAl metal is made into a spiral structure, oxidized to generate Al2O3 whiskers, coated with Al2O3-aluminum sol slurry, and then impregnated with Cu / Zn salt. The metal heats up rapidly when electricity is applied, but there is also the possibility that under thermal stress, the coating and the substrate may easily crack or even peel off due to the mismatch between expansion and contraction.

[0004] For example, patent CN112023909A demonstrates a method where a porous carbon skeleton with alternating pore walls is first 3D printed, then activated in a urea atmosphere and excessively impregnated with a copper nitrate solution. The conductive matrix can directly generate Joule heating, achieving second-level heating and uniform bed temperature. However, 3D printed materials may suffer from cracking, deformation, or structural collapse due to uneven slurry dispersion. Furthermore, the complex internal channels can lead to uneven distribution of active components.

[0005] While there are numerous reports on the application of coating methods for monolithic foam materials, the methods for simultaneously achieving high uniformity, strong adhesion, excellent thermal stability, and industrial-grade preparation of catalyst coatings still require optimization. Further research is needed to ensure that catalysts can effectively suppress sintering and maintain long-term stability under high-temperature conditions while constructing highly dispersed nanostructures. Summary of the Invention

[0006] This invention aims to solve the problems of uneven coating and poor adhesion of catalyst active components on the overall foam material, as well as the complexity of the preparation process in existing technologies. By optimizing the coating steps and parameters, uniform distribution of active components is achieved, thereby improving catalyst performance and stability.

[0007] The technical solution of this invention to solve the technical problem is as follows:

[0008] A method for uniformly coating a catalyst onto a monolithic foam material includes the following steps: 1) preparing a precursor solution; 2) stirring the precursor solution and subjecting it to ultrasonic treatment; 3) immersing the monolithic foam material in the precursor solution, ultrasonically assisted coating, and blowing off excess liquid; 4) drying and rapid calcination; 5) repeating the coating process, i.e., repeating steps 3) and 4); 6) final calcination; in step 1), the precursor solution contains copper nitrate, zinc nitrate, aluminum nitrate, and a structure directing agent, and the solvent is ethanol or water; the ratio of copper nitrate, zinc nitrate, aluminum nitrate, and the structure directing agent is 1-6:1-3:1:1-3.

[0009] Further, in step 1), the structure directing agent is selected from hexadecyltrimethylammonium bromide, citric acid or oleic acid, preferably hexadecyltrimethylammonium bromide (CTAB).

[0010] Furthermore, in step 2), the ultrasonic treatment time is 2-10 minutes to promote solution penetration and dispersion.

[0011] Furthermore, in step 3), the ultrasonic treatment time is 2-10 minutes, and the overall foam material is selected from silicon carbide (SiC) or silicon oxycarbide (SiOC).

[0012] Furthermore, in step 4), the drying temperature is 100-200℃, the drying time is 5-15 min, the rapid calcination temperature is 300-400℃, and the rapid calcination time is 2-10 min.

[0013] Furthermore, in step 5), the coating is repeated 2-10 times to achieve uniform loading of the active component.

[0014] Furthermore, in step 6), the final calcination temperature is 400-500℃, and the final calcination time is 2-4 hours.

[0015] In a preferred embodiment of the present invention, the method for uniformly coating the catalyst onto the integral foam material includes the following steps:

[0016] 1) Preparation of precursor solution: Use ethanol or water as solvent to dissolve a certain proportion of copper nitrate, zinc nitrate and aluminum nitrate, and add an appropriate amount of structure directing agent hexadecyltrimethylammonium bromide to improve metal dispersibility. The molar ratio of copper nitrate, zinc nitrate, aluminum nitrate and hexadecyltrimethylammonium bromide is 6:2:1:1.

[0017] 2) Stirring and sonication: Stir the precursor solution at room temperature to ensure that the components are fully dissolved and mixed, and then sonicate for 5 minutes to further eliminate bubbles and agglomeration.

[0018] 3) Impregnation and coating: Immerse the silicon carbide foam material completely in the precursor solution and sonicate for 2 minutes to promote the solution to penetrate into the foam pores; after removing the material, blow off the excess liquid on the surface with airflow to avoid localized excessive thickness.

[0019] 4) Drying and calcination: Place the material in an oven to dry and remove the solvent; then transfer it to a muffle furnace for rapid heating and calcination to initially solidify the active components. Specifically, dry at 150℃ for 10 minutes, then calcine at 350℃ in a muffle furnace for 5 minutes, with a heating rate of 10℃ / min.

[0020] 5) Repeated Coating: The obtained monolithic catalyst is immersed again in the precursor solution, and the steps of sonication, blowing, drying, and calcination are repeated, with the calcination time being consistent each time, until the precursor solution is completely consumed. This repeated process ensures the accumulation of active components layer by layer, improving coating uniformity and loading. Specifically, steps 3) and 4) are repeated 5 times.

[0021] 6) Final calcination: The material is placed in a muffle furnace and calcined at a slow temperature to achieve complete crystallization and stabilization of the active components, thus obtaining the final catalyst. Specifically, the temperature is slowly increased to 400℃ at a rate of 1℃ / min, and calcined for 2 hours.

[0022] The present invention has the following technical effects:

[0023] Compared with existing technologies, this invention, in terms of catalyst technology, ensures that the active catalyst components are uniformly distributed throughout the overall foam material without aggregation or shedding, thus improving catalytic efficiency and stability. Through repeated coating, the loading can be precisely controlled to adapt to different application requirements. Economically, the method is simple, easy to operate, and requires no complex equipment, reducing production costs and energy consumption. In terms of social impact, it is applicable to environmental catalysis (such as waste gas treatment) and energy conversion fields, helping to improve resource utilization and reduce pollution. Figure 1 As can be seen, the catalyst (the black part in the actual sample) is evenly distributed across the entire foam material. From... Figure 3 As can be seen from the EDS analysis, the distribution of CuZnAl (catalytically active elements) is relatively uniform. Figure 2 As can be seen, after repeated loading, the catalyst mass continued to increase, and the ultrasonic experiment showed that no active components fell off. Attached Figure Description

[0024] Figure 1 This represents the distribution of the catalyst active component on the overall foam material.

[0025] Figure 2 This represents the overall mass increase of the foam material after multiple loads.

[0026] Figure 3The SEM-EDS comparison results are shown for CZAC-E(a) and CZA-E(b).

[0027] Figure 4 The results show the influence of the overall structure of CTAB and the support on the catalyst's activity.

[0028] Figure 5 The results show the thermal stability and catalytic performance of CZAC-E. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments.

[0030] Example 1

[0031] The method for uniformly coating a catalyst onto the overall foam material in this embodiment includes the following steps:

[0032] 1) Preparation of precursor solution: Take 40 ml of ethanol as solvent to dissolve copper nitrate (0.18 mol), zinc nitrate (0.06 mol) and aluminum nitrate (0.03 mol), and add structure-directing agent CTAB (0.03 mol) as dispersant.

[0033] 2) Stirring and sonication: The precursor solution prepared in step 1) was magnetically stirred at room temperature for 2 hours, and then sonicated for 5 minutes (power 100W).

[0034] 3) Impregnation and coating: Immerse the silicon carbide foam material (size 1.7cm×6.5cm) in the solution prepared in step 2) and sonicate for 2 minutes; after removal, blow off the surface liquid with an air gun.

[0035] 4) Drying and calcination: Dry at 150℃ for 10 minutes, then calcine at 350℃ in a muffle furnace for 5 minutes (heating rate 10℃ / min).

[0036] 5) Repeat coating: Repeat the impregnation step in step 3) and the calcination step in step 4) 5 times until the solution is used up.

[0037] 6) Final calcination: Slowly heat to 400℃ (heating rate 1℃ / min) and calcine for 2 hours to obtain the catalyst. This is the CTAB-modified catalyst (CZAC-E@SNW / SiC).

[0038] The synthesized material was named CZAC-E@SNW / SiC, representing a precursor solution using ethanol (E) and a catalyst with added CTAB. In CZAC, C represents CuO, Z represents ZnO, A represents Al2O3, and C represents CTAB. The synthesized material was named CZAC-W@SNW / SiC, representing a precursor solution using deionized water (W) and a catalyst with added CTAB. The support portion was named SNW / SiC, representing a silicon carbide foam material with silicon carbide nanocrystals. Ultrasonic testing after synthesis revealed no signs of detachment of the surface-active components (CuO-ZnO-Al2O3), indicating that the synthesis method effectively attached the active components to the SiC support surface.

[0039] Comparative Example 1: Preparation of a catalyst without CTAB (CZA-E@SNW / SiC)

[0040] Preparation method: basically the same as in Example 1, except that in step 1), the structure directing agent CTAB is not added, and other operations are the same as in Example 1.

[0041] Comparative Example 2: Preparation of Powdered Catalyst (CZAC-E)

[0042] Preparation method: basically the same as in Example 1, except that silicon carbide foam material is not used in step 3), and other operations are the same as in Example 1.

[0043] Comparative Example 3: Preparation of a catalyst with water as the precursor solvent (CZA-W@SNW / SiC)

[0044] Preparation method: It is basically the same as in Example 1, except that in step 1), water is used as the precursor solution and the structure directing agent CTAB is not added. Other operations are the same as in Example 1.

[0045] from Figure 1 As can be seen, the catalyst CZAC-E@SNW / SiC (the black part in the actual product) of the present invention is uniformly covered on the entire foam material.

[0046] Figure 2 The effects of precursor solvent, structure-directing agent CTAB, and carrier structure on the loading of active components were compared (CZA-W@SNW / SiC; CZA-E@SNW / SiC; CZAC-E@SNW / SiC). The results show that Example 1 achieved the largest mass growth rate (mass difference before and after loading) after repeating the same coating loading method. The mass growth rate decreased when water was used as the solvent due to the different surface tensions, boiling points, and contact angles of water and ethanol. Figure 2 As can be seen, after repeated loading, the mass growth of the CZAC-E@SNW / SiC catalyst of the present invention continued to increase, and the active components did not fall off through ultrasonic experiments.

[0047] from Figure 3 SEM-EDS results showed that CuO-ZnO-Al2O3 was more uniformly dispersed after the addition of CTAB. SEM-EDS results of CZAC-E showed that Cu (green), Zn (pink), and Al (blue) were more uniformly distributed (in color) than those of CZA-E.

[0048] Figure 4 This study compared the methanol selectivity and CO2 conversion rates of a catalyst without CTAB (CZA-E@SNW / SiC), a CTAB-modified catalyst (CZAC-E@SNW / SiC), and a powdered catalyst (CZAC-E) under the same pressure hourly space velocity (PHSV) and varying temperatures. Specifically, the catalyst was packed into a fixed-bed flowing gas reaction system made of 316L stainless steel. To test catalytic performance, the sample was first reduced with flowing H2 (50 sccm) for 2 hours at atmospheric pressure and 275°C. After reduction, the catalyst was purged with argon (50 sccm) for 30 minutes, then pressurized to 3 MPa, and reaction tests were conducted at 175, 200, 225, 250, 275, and 300°C. The feed gas flow composition was H2:CO2:N2 = 30:10:10 sccm. The composition of the outlet gas was analyzed using an online gas chromatograph (HF-901, Huifen, China) equipped with a thermal conductivity detector (TCD) and a flame ionization detector (FID).

[0049] It was found that using SNW / SiC foam as a carrier, the CTAB-modified material (CZAC-E@SNW / SiC) can be used at 3 MPa, 275℃, H2:CO2 = 3:1, and GHSV = 221 h. -1 At the same time, a CO2 conversion rate of >15% and a methanol selectivity of >94% were obtained. Under the same conditions, CZA-E@SNW / SiC achieved a CO2 conversion rate of >12% and a methanol selectivity of >10%. Under the same conditions, CZAC-E achieved a CO2 conversion rate of >6% and a methanol selectivity of >99%.

[0050] Figure 5 The CZAC-E@SNW / SiC catalyst exhibits good methanol selectivity and thermal stability under this synthesis method, with a methanol selectivity of >94% in a 100-h continuous flow reaction.

[0051] The above are merely embodiments of the present invention and do not limit the scope of the patent. Any equivalent modifications made based on the content of this specification, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A method for uniformly coating a catalyst onto a monolithic foam material, characterized in that, Includes the following steps: 1) Prepare the precursor solution; 2) Stir the precursor solution and sonicate it; 3) Immerse the entire foam material in the precursor solution, apply with ultrasonic assistance, and blow away excess liquid; 4) Dry and rapidly calcine; 5) Repeat coating, i.e., repeat steps 3) and 4); 6) Final calcine; In step 1), the precursor solution contains copper nitrate, zinc nitrate, aluminum nitrate and a structure directing agent, and the solvent is ethanol or water; The ratio of copper nitrate, zinc nitrate, aluminum nitrate and structure directing agent is 1-6:1-3:1:1-3.

2. The method according to claim 1, characterized in that, In step 1), the structure directing agent is selected from hexadecyltrimethylammonium bromide, citric acid, or oleic acid.

3. The method according to claim 1, characterized in that, In step 2), the ultrasonic treatment time is 2-10 minutes.

4. The method according to claim 1, characterized in that, In step 3), the ultrasonic treatment time is 2-10 minutes, and the overall foam material is selected from silicon carbide (SiC) or silicon oxycarbide (SiOC).

5. The method according to claim 1, characterized in that, In step 4), the drying temperature is 100-200℃, the drying time is 5-15 min, the rapid calcination temperature is 300-400℃, and the rapid calcination time is 2-10 min.

6. The method according to claim 1, characterized in that, In step 5), the coating is repeated 2-10 times to achieve uniform loading of the active component.

7. The method according to claim 1, characterized in that, In step 6), the final calcination temperature is 400-500℃ and the final calcination time is 2-4 hours.

8. The method according to claim 1, characterized in that, The method for uniformly coating the catalyst onto the monolithic foam material includes the following steps: 1) Preparation of precursor solution: Use ethanol or water as solvent to dissolve a certain proportion of copper nitrate, zinc nitrate and aluminum nitrate, and add an appropriate amount of structure directing agent hexadecyltrimethylammonium bromide to improve metal dispersibility. The molar ratio of copper nitrate, zinc nitrate, aluminum nitrate and hexadecyltrimethylammonium bromide is 6:2:1:

1. 2) Stirring and sonication: Stir the precursor solution at room temperature to ensure that the components are fully dissolved and mixed, and then sonicate for 5 minutes to further eliminate bubbles and agglomeration; 3) Impregnation and coating: Immerse the silicon carbide foam material completely in the precursor solution and sonicate for 2 minutes to promote the solution to penetrate into the foam pores; after removing the material, blow off the excess liquid on the surface with airflow to avoid localized excessive thickness; 4) Drying and calcination: Dry at 150℃ for 10 minutes, calcin at 350℃ in a muffle furnace for 5 minutes, with a heating rate of 10℃ / min; 5) Repeat coating: Repeat steps 3) and 4) 5 times; 6) Final calcination: Slowly heat to 400℃ at a rate of 1℃ / min and calcine for 2 hours.

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