Composite catalyst for degrading vocs and method for preparing the same

Abstract

The present application belongs to the technical field of catalysts, and provides a composite catalyst for degrading VOCs and a preparation method thereof, which comprises the following steps: S1, weighing 1.9 g of copper nitrate and 3.6 g of manganese nitrate, dissolving them in water, and then adding lanthanum nitrate to obtain a multi-element solution; S2, adding 1-1.05 g of a water slat-silicon dioxide modified product to the multi-element solution and ultrasonicating; then adding 1.5-1.6 mL of a cerium nitrate solution with a concentration of 0.5 mol / L and stirring to obtain a suspension solution; S3, adjusting the pH of the suspension solution to 9-10, stirring, and aging; filtering and drying, grinding, and calcining to obtain an initial catalyst powder; S4, adding water to the initial catalyst powder, mixing, adjusting the pH to 3-4, and grinding; then coating the mixture on a honeycomb ceramic substrate, drying, and calcining to obtain the composite catalyst. The composite catalyst prepared by the method can be used in the catalytic decomposition of ethyl acetate, and can reduce the complete conversion temperature to below 220 DEG C to match the industrial low-temperature waste heat exhaust gas at 160-220 DEG C, thereby reducing the energy consumption for heating and the operation cost of the equipment.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a composite catalyst for the degradation of VOCs and its preparation method. Background Technology

[0002] Volatile organic compounds (VOCs) are key precursors to smog and ozone pollution. If released directly into the atmosphere without treatment, they not only exacerbate air pollution but also pose a significant threat to human health. Among various VOCs treatment technologies, catalytic combustion technology has the highest application rate. Currently, catalysts used for the catalytic combustion of VOCs primarily rely on noble metals and transition metal oxides as their active components. Although noble metal catalysts exhibit excellent catalytic activity at low temperatures, their high cost is a limiting factor for their widespread application.

[0003] In existing technologies, the effective catalytic decomposition of ethyl acetate can be achieved by loading rare-earth (La) modified Cu-Mn spinel oxide onto a honeycomb ceramic support. Specifically, the CuMn2O4 spinel synthesized using (NH4)2CO3 as a precipitant can construct a large specific surface area and suitable pore structure, a characteristic that significantly enhances the catalyst's adsorption capacity for ethyl acetate. The doping of rare-earth elements does not significantly alter the catalyst's crystal phase structure, but effectively improves its reduction performance and lowers the temperature required for the catalytic decomposition reaction. For the catalytic decomposition of ethyl acetate, 99% conversion can be achieved at 239℃, but the temperature is still relatively high. The waste heat from coating, printing, and drying ovens is mostly between 160-220℃, and the heat of the waste gas itself is insufficient to reach 239℃, requiring additional electric / gas heating, significantly increasing operating energy consumption and equipment operating costs. Summary of the Invention

[0004] To address the problems existing in the background technology, the present invention provides a composite catalyst for the degradation of VOCs and its preparation method. The composite catalyst is used in the catalytic decomposition of ethyl acetate, which can reduce the complete conversion temperature to below 220°C, so as to match the industrial low-temperature waste heat exhaust gas at 160-220°C, thereby reducing the energy consumption and operating cost of equipment reheating.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing a composite catalyst for degrading VOCs, comprising the following steps: S1. Weigh 1.9g of copper nitrate and 3.6g of manganese nitrate, dissolve them in 100mL of distilled water, stir, and then add lanthanum nitrate to obtain a multi-element solution; the mass fraction of lanthanum in the multi-element solution is 3%; (the amount of lanthanum nitrate is 0.17g). S2. Add 1-1.05g of hydrotalcite-silica modifier to the multi-element solution obtained in S1 and stir ultrasonically for 25-35min; then add 1.5-1.6mL of 0.5mol / L cerium nitrate Ce(NO3)3 solution, stir and mix to obtain a suspension. S3. Adjust the pH of the suspension obtained in S2 to 9-10, stir for 4 hours, and age for 11-12 hours to allow it to separate into layers; filter and dry the resulting precipitate, grind it, and calcine it to obtain the initial catalyst powder; S4. Add deionized water to the initial catalyst powder obtained in S3, mix well, and obtain a catalyst slurry with a solid content of 20±0.5wt%; adjust its pH to 3-4, grind for 5h; then coat the catalyst slurry onto a honeycomb ceramic substrate (48μm cordierite honeycomb) by vacuum coating technology, dry, and calcine to obtain the composite catalyst for VOCs degradation.

[0006] Further, in S3, under stirring conditions, an ammonium carbonate solution with a concentration of 1 mol / L is added to the suspension to adjust its pH.

[0007] Furthermore, in S3, the drying temperature is 100±5℃ and the drying time is 2-3h; the calcination temperature is 550±10℃ and the calcination time is 4-4.5h.

[0008] Furthermore, in S4, the pH is adjusted using a 0.1 mol / L nitric acid solution.

[0009] Further, in S4, the drying temperature is 110±5℃ and the drying time is 5.5-6.5h; the calcination temperature is 550±10℃ and the calcination time is 2-2.5h.

[0010] Furthermore, the preparation method of the hydrotalcite-silica modified material is as follows: A1. Prepare a 50 mL first mixed solution by mixing 0.05 mol sodium hydroxide and 0.02 mol sodium carbonate; prepare a 50 mL second mixed solution by mixing 0.03 mol magnesium nitrate hexahydrate and 0.01 mol aluminum nitrate nonahydrate. Under stirring, the first mixed solution was added to the second mixed solution, and stirred at 65±2℃ for 24h to obtain hydrotalcite gel; A2. Add 10 mL of the hydrotalcite gel obtained in A1 to 3 g of amorphous silica, add deionized water to obtain 50 mL of suspension; stir at 25±2℃ for 12 h, filter, dry, and calcine to obtain the hydrotalcite-silica modified product.

[0011] Furthermore, in A2, the drying temperature is 98-100℃, and the drying time is 3-5 hours.

[0012] Furthermore, in A2, the calcination temperature is 500±10℃, and the calcination time is 2-3h.

[0013] Secondly, the present invention provides a composite catalyst for the degradation of VOCs, which is prepared by the above-described preparation method.

[0014] This application has the following beneficial effects: 1. In the preparation of the composite catalyst of this invention, a hydrotalcite-silica modifier and cerium nitrate are added simultaneously; CeO2 depends on Ce 3+ / Ce 4+ The reversible cycle provides a large amount of lattice oxygen and oxygen vacancies; Ce and CuMn2O4 form a heterojunction to accelerate electron transfer, promote the low-temperature ester bond breaking of ethyl acetate and complete oxidation of intermediates; at the same time, it balances the precipitation rate of co-precipitated metals, reduces the inert impurities of CuO and MnO2, and improves the purity of spinel; La and Ce, two rare earth elements, work together to stabilize the crystal structure and reduce the conversion temperature of ethyl acetate.

[0015] 2. After simultaneous modification with hydrotalcite-silica and cerium dioxide, the hydrotalcite-silica modified product and cerium dioxide form multiple synergistic catalytic effects: Ce 4+ Ions penetrate the hydrotalcite-silica modified barrier layer, opening gas diffusion channels and counteracting the negative effects of the hydrotalcite-silica physical shielding, thus reducing the activation energy for the catalytic oxidation of ethyl acetate. The basic adsorption sites of the hydrotalcite-silica modified compound and the acidic oxygen vacancies of CeO2 synergistically activate the ester bonds of ethyl acetate; Ce... 3+ / Ce 4+ A continuous supply of active lattice oxygen accelerates the complete mineralization of intermediates at low temperatures; simultaneously, the porous framework of the hydrotalcite-silica modifier confines and disperses CeO2, preventing the cerium component from sintering at high temperatures. Multiple synergistic effects work together to reduce the activation energy of ethyl acetate catalytic oxidation, lowering the complete conversion temperature to below 220℃, matching the 160-220℃ low-temperature industrial waste heat exhaust gas, thus reducing equipment reheating energy consumption and operating costs. Attached Figure Description

[0016] Figure 1 This is a comparison graph showing the change in the conversion rate of ethyl acetate with temperature under the action of the composite catalyst prepared in Example 1 and Comparative Examples 1-3 of the present invention. Detailed Implementation

[0017] The present application will be further described in detail below with reference to the embodiments.

[0018] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application are all commercially available.

[0019] The preparation method of the hydrotalcite-silica modified material involved in the embodiments / comparative examples of this invention is as follows: A1. Prepare a 50 mL first mixed solution by mixing 0.05 mol sodium hydroxide and 0.02 mol sodium carbonate; prepare a 50 mL second mixed solution by mixing 0.03 mol magnesium nitrate hexahydrate and 0.01 mol aluminum nitrate nonahydrate. Under stirring, the first mixed solution was added to the second mixed solution, and the mixture was stirred at 65°C for 24 hours to obtain hydrotalcite gel.

[0020] A2. Add 10 mL of the hydrotalcite gel obtained in A1 to 3 g of amorphous silica, add deionized water to obtain 50 mL of suspension; stir at 25 °C for 12 h, filter, dry at 100 °C for 4 h; calcine at 500 °C for 2.5 h to obtain the modified hydrotalcite-silica.

[0021] The amorphous silica (100-200 mesh) was purchased from Qingdao Chenrong New Materials Co., Ltd.

[0022] Other specific details of the embodiments / comparative examples of the present invention are as follows.

[0023] Example 1:

[0024] A method for preparing a composite catalyst for VOCs degradation includes the following steps: S1. Weigh 1.9g of copper nitrate and 3.6g of manganese nitrate, dissolve them in 100mL of distilled water, stir, and then add lanthanum nitrate to obtain a multi-element solution; the mass fraction of lanthanum in the multi-element solution is 3%; (the amount of lanthanum nitrate used is 0.17g).

[0025] S2. Add 1.02g of hydrotalcite-silica modifier to the multi-element solution obtained in S1 and stir ultrasonically for 30min; then add 1.55mL of 0.5mol / L cerium nitrate Ce(NO3)3 solution and stir to mix to obtain a suspension.

[0026] S3. Under stirring conditions, a 1 mol / L ammonium carbonate solution was added to the suspension to adjust its pH to 9.5, stirred for 4 h, and aged for 11.5 h to allow it to separate into layers; the resulting precipitate was filtered and dried at 100 °C for 2.5 h; it was then ground and calcined at 550 °C for 4.2 h to obtain the initial catalyst powder.

[0027] S4. Add deionized water to the initial catalyst powder obtained in S3, mix well, and obtain a catalyst slurry with a solid content of 20wt%; adjust its pH to 3.7 using a 0.1 mol / L nitric acid solution, and grind for 5 hours; then coat the catalyst slurry onto a honeycomb ceramic substrate (48μm cordierite honeycomb) using vacuum coating technology, dry at 110℃ for 6 hours; calcine at 550℃ for 2.2 hours; thus obtaining the composite catalyst for VOCs degradation.

[0028] Example 2:

[0029] A method for preparing a composite catalyst for VOCs degradation includes the following steps: S1. Weigh 1.9g of copper nitrate and 3.6g of manganese nitrate, dissolve them in 100mL of distilled water, stir, and then add lanthanum nitrate to obtain a multi-element solution; the mass fraction of lanthanum in the multi-element solution is 3%; (the amount of lanthanum nitrate used is 0.17g).

[0030] S2. Add 1g of hydrotalcite-silica modifier to the multi-element solution obtained in S1 and stir ultrasonically for 25min; then add 1.5mL of 0.5mol / L cerium nitrate Ce(NO3)3 solution and stir to mix to obtain a suspension.

[0031] S3. Under stirring conditions, a 1 mol / L ammonium carbonate solution was added to the suspension to adjust its pH to 9.3, stirred for 4 h, and aged for 12 h to allow it to separate into layers; the resulting precipitate was filtered and dried at 100 °C for 2.5 h; it was then ground and calcined at 550 °C for 4.2 h to obtain the initial catalyst powder.

[0032] S4. Add deionized water to the initial catalyst powder obtained in S3, mix well, and obtain a catalyst slurry with a solid content of 20wt%; adjust its pH to 3.6 using a 0.1 mol / L nitric acid solution, and grind for 5 hours; then coat the catalyst slurry onto a honeycomb ceramic substrate (48μm cordierite honeycomb) using vacuum coating technology, dry at 110℃ for 6 hours; calcine at 550℃ for 2.2 hours; thus obtaining the composite catalyst for VOCs degradation.

[0033] Example 3:

[0034] A method for preparing a composite catalyst for VOCs degradation includes the following steps: S1. Weigh 1.9g of copper nitrate and 3.6g of manganese nitrate, dissolve them in 100mL of distilled water, stir, and then add lanthanum nitrate to obtain a multi-element solution; the mass fraction of lanthanum in the multi-element solution is 3%; (the amount of lanthanum nitrate used is 0.17g).

[0035] S2. Add 1.05g of hydrotalcite-silica modifier to the multi-element solution obtained in S1 and stir ultrasonically for 35min; then add 1.6mL of 0.5mol / L cerium nitrate Ce(NO3)3 solution and stir to mix to obtain a suspension.

[0036] S3. Under stirring conditions, a 1 mol / L ammonium carbonate solution was added to the suspension to adjust its pH to 9.8, stirred for 4 h, and aged for 12 h to allow it to separate into layers; the resulting precipitate was filtered and dried at 100 °C for 2.5 h; it was then ground and calcined at 550 °C for 4.2 h to obtain the initial catalyst powder.

[0037] S4. Add deionized water to the initial catalyst powder obtained in S3, mix well, and obtain a catalyst slurry with a solid content of 20wt%; adjust its pH to 3.8 using a 0.1 mol / L nitric acid solution, and grind for 5 hours; then coat the catalyst slurry onto a honeycomb ceramic substrate (48μm cordierite honeycomb) using vacuum coating technology, dry at 110℃ for 6 hours; calcine at 550℃ for 2.2 hours; thus obtaining the composite catalyst for VOCs degradation.

[0038] Comparative Example 1: The difference between this comparative example and Example 1 is that no hydrotalcite-silica modifier and cerium nitrate are added in the preparation of the composite catalyst.

[0039] Specifically, a method for preparing a composite catalyst for degrading VOCs includes the following steps: S1. Weigh 1.9g of copper nitrate and 3.6g of manganese nitrate, dissolve them in 100mL of distilled water, stir, and then add lanthanum nitrate to obtain a multi-element solution; the mass fraction of lanthanum in the multi-element solution is 3%; (the amount of lanthanum nitrate used is 0.17g).

[0040] S2. Under stirring conditions, a 1 mol / L ammonium carbonate solution was added to the multi-element solution to adjust its pH to 9.5, stirred for 4 h, and aged for 11.5 h to allow it to separate into layers; the resulting precipitate was filtered and dried at 100 °C for 2.5 h; it was then ground and calcined at 550 °C for 4.2 h to obtain the initial catalyst powder.

[0041] S3. Add deionized water to the initial catalyst powder obtained in S2, mix well, and obtain a catalyst slurry with a solid content of 20 wt%. Adjust its pH to 3.7 using a 0.1 mol / L nitric acid solution and grind for 5 h. Then, coat the catalyst slurry onto a honeycomb ceramic substrate (48 μm cordierite honeycomb) using vacuum coating technology, dry it at 110℃ for 6 h, and calcine it at 550℃ for 2.2 h to obtain the composite catalyst for VOCs degradation.

[0042] Comparative Example 2: The difference between this comparative example and Example 1 is that no hydrotalcite-silica modifier is added in the preparation of the composite catalyst.

[0043] Specifically, a method for preparing a composite catalyst for degrading VOCs includes the following steps: S1. Weigh 1.9g of copper nitrate and 3.6g of manganese nitrate, dissolve them in 100mL of distilled water, stir, and then add lanthanum nitrate to obtain a multi-element solution; the mass fraction of lanthanum in the multi-element solution is 3%; (the amount of lanthanum nitrate used is 0.17g).

[0044] S2. Add 1.55 mL of 0.5 mol / L cerium nitrate Ce(NO3)3 solution to the multi-element solution obtained in S1, stir and mix to obtain a suspension.

[0045] S3. Under stirring conditions, a 1 mol / L ammonium carbonate solution was added to the suspension to adjust its pH to 9.5, stirred for 4 h, and aged for 11.5 h to allow it to separate into layers; the resulting precipitate was filtered and dried at 100 °C for 2.5 h; it was then ground and calcined at 550 °C for 4.2 h to obtain the initial catalyst powder.

[0046] S4. Add deionized water to the initial catalyst powder obtained in S3, mix well, and obtain a catalyst slurry with a solid content of 20wt%; adjust its pH to 3.7 using a 0.1 mol / L nitric acid solution, and grind for 5 hours; then coat the catalyst slurry onto a honeycomb ceramic substrate (48μm cordierite honeycomb) using vacuum coating technology, dry at 110℃ for 6 hours; calcine at 550℃ for 2.2 hours; thus obtaining the composite catalyst for VOCs degradation.

[0047] Comparative Example 3: The difference between this comparative example and Example 1 is that cerium nitrate is not added in the preparation of the composite catalyst.

[0048] Specifically, a method for preparing a composite catalyst for degrading VOCs includes the following steps: S1. Weigh 1.9g of copper nitrate and 3.6g of manganese nitrate, dissolve them in 100mL of distilled water, stir, and then add lanthanum nitrate to obtain a multi-element solution; the mass fraction of lanthanum in the multi-element solution is 3%; (the amount of lanthanum nitrate used is 0.17g).

[0049] S2. Add 1.02g of hydrotalcite-silica modifier to the multi-element solution obtained in S1, and stir ultrasonically for 30min to obtain a suspension.

[0050] S3. Under stirring conditions, a 1 mol / L ammonium carbonate solution was added to the suspension to adjust its pH to 9.5, stirred for 4 h, and aged for 11.5 h to allow it to separate into layers; the resulting precipitate was filtered and dried at 100 °C for 2.5 h; it was then ground and calcined at 550 °C for 4.2 h to obtain the initial catalyst powder.

[0051] S4. Add deionized water to the initial catalyst powder obtained in S3, mix well, and obtain a catalyst slurry with a solid content of 20wt%; adjust its pH to 3.7 using a 0.1 mol / L nitric acid solution, and grind for 5 hours; then coat the catalyst slurry onto a honeycomb ceramic substrate (48μm cordierite honeycomb) using vacuum coating technology, dry at 110℃ for 6 hours; calcine at 550℃ for 2.2 hours; thus obtaining the composite catalyst for VOCs degradation.

[0052] Experimental Example: Test Subjects: Composite catalysts prepared in Example 1 and Comparative Examples 1-3. Test Items and Results: The conversion rate of ethyl acetate under each catalyst as a function of temperature is shown in the figure below. Figure 1 .

[0053] Results analysis: Combining Figure 1 Analysis of Example 1 and Comparative Examples 1-3: Specifically, by comparing Comparative Example 1 and Comparative Example 2, it can be seen that, compared with Comparative Example 1, the addition of cerium nitrate in the preparation of the composite catalyst in Comparative Example 2 resulted in a significant reduction in the complete conversion temperature of ethyl acetate under the action of the composite catalyst.

[0054] Specifically, comparing Comparative Examples 1 and 3, it can be seen that, compared to Comparative Example 1, the addition of hydrotalcite-silica modifier alone in the preparation of the composite catalyst in Comparative Example 3 actually increased the complete conversion temperature of ethyl acetate under the action of the composite catalyst. This is mainly because, when hydrotalcite-silica modifier is added alone, the inert silica-hydrotalcite composite powder coats Cu-Mn-La spinel, blocks the pores, and the excess alkaline sites inhibit the low-temperature activation of ester groups, thus increasing the conversion temperature of ethyl acetate, exhibiting a significant reverse inhibitory effect.

[0055] In comparison with Example 1, it can be seen that the simultaneous introduction of cerium nitrate and hydrotalcite-silica modifiers in the preparation of the composite catalyst can produce a synergistic effect, which can synergistically reduce the complete conversion temperature of ethyl acetate and lower the complete conversion temperature to below 220°C, so as to match the industrial low-temperature waste heat exhaust gas of 160-220°C, and reduce the energy consumption and operating cost of equipment reheating.

[0056] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0057] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing a composite catalyst for degrading VOCs, characterized in that, Includes the following steps: S1. Weigh 1.9g of copper nitrate and 3.6g of manganese nitrate, dissolve them in 100mL of distilled water, stir, and then add lanthanum nitrate to obtain a multi-element solution; the mass fraction of lanthanum in the multi-element solution is 3%. S2. Add 1-1.05g of hydrotalcite-silica modifier to the multi-element solution obtained in S1 and stir ultrasonically for 25-35min; then add 1.5-1.6mL of 0.5mol / L cerium nitrate solution, stir and mix to obtain a suspension. S3. Adjust the pH of the suspension obtained in S2 to 9-10, stir for 4 hours, and age for 11-12 hours; filter and dry the obtained precipitate, grind it, and calcine it to obtain the initial catalyst powder; S4. Add water to the initial catalyst powder obtained in S3, mix well, and obtain a catalyst slurry with a solid content of 20±0.5wt%; adjust its pH to 3-4, grind, then coat it on a honeycomb ceramic substrate, dry, and calcine to obtain the composite catalyst for VOCs degradation.

2. The method for preparing the composite catalyst for VOCs degradation according to claim 1, characterized in that, In S3, under stirring conditions, a 1 mol / L ammonium carbonate solution is added to the suspension to adjust its pH.

3. The method for preparing the composite catalyst for VOCs degradation according to claim 1, characterized in that, In S3, the drying temperature is 100±5℃ and the drying time is 2-3h; the calcination temperature is 550±10℃ and the calcination time is 4-4.5h.

4. The method for preparing the composite catalyst for VOCs degradation according to claim 1, characterized in that, In S4, the pH was adjusted using a 0.1 mol / L nitric acid solution.

5. The method for preparing the composite catalyst for VOCs degradation according to claim 1, characterized in that, In step S4, the drying temperature is 110±5℃ and the drying time is 5.5-6.5h; the calcination temperature is 550±10℃ and the calcination time is 2-2.5h.

6. The method for preparing the composite catalyst for VOCs degradation according to claim 1, characterized in that, The preparation method of the hydrotalcite-silica modified material is as follows: A1. Prepare a 50 mL first mixed solution by mixing 0.05 mol sodium hydroxide and 0.02 mol sodium carbonate; prepare a 50 mL second mixed solution by mixing 0.03 mol magnesium nitrate hexahydrate and 0.01 mol aluminum nitrate nonahydrate. Under stirring, the first mixed solution was added to the second mixed solution, and stirred at 65±2℃ for 24h to obtain hydrotalcite gel; A2. Add 10 mL of the hydrotalcite gel obtained in A1 to 3 g of silica, add deionized water to obtain 50 mL of suspension; stir at 25±2℃ for 12 h, filter, dry, and calcine to obtain the hydrotalcite-silica modified product.

7. The method for preparing the composite catalyst for VOCs degradation according to claim 6, characterized in that, In A2, the drying temperature is 98-100℃ and the drying time is 3-5 hours.

8. The method for preparing the composite catalyst for VOCs degradation according to claim 6, characterized in that, In A2, the calcination temperature is 500±10℃ and the calcination time is 2-3h.

9. A composite catalyst for degrading VOCs, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 8.

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