Composite functional coating catalyst and preparation method thereof

Abstract

The present invention provides a composite functional coating catalyst and a preparation method thereof, belonging to the technical field of industrial waste gas treatment. The preparation method comprises at least the following steps: preparing a titanic acid-coated carrier, loading a catalytic oxidation active component, and coating a second active component. The present invention adopts a design concept of multiple coatings and sequential energization to prepare a new catalyst for the synergistic removal of NOx and benzene-related VOCs from industrial tail gas, achieving high nitrogen selectivity. The catalytic oxidation temperature T of the obtained catalyst is 100°C. 90 As low as 195°C, the NOx conversion rate and N2 selectivity at this temperature are as high as 95% and 98% respectively.

Description

Technical Field

[0001] The present invention belongs to the technical field of industrial waste gas treatment, and in particular relates to a composite functional coating catalyst and a preparation method thereof. Background Art

[0002] The production of steel, petrochemicals, coking, rubber, and coatings inevitably generates large amounts of waste gas. Among these waste gases, nitrogen oxides (NOx) contribute to environmental problems such as acid rain and photochemical smog. Volatile organic pollutants (VOCs) have multiple environmental impacts and are important precursors to ozone formation and smog, posing serious risks to human health and the environment. Therefore, efficiently removing NOx and VOCs from waste gas is a key issue in the environmental protection field. For NOx removal, relatively mature technologies (such as VW / TiO2 NH3-SCR) are currently available. For the removal of lower-concentration VOCs, catalytic oxidation offers advantages such as low energy consumption, low operating temperatures, no secondary pollution, and a wide range of applications, making it the most promising VOC abatement technology. Furthermore, the removal of NOx and VOCs from waste gas typically requires two separate operating units. The ability to achieve synergistic removal of both using a single catalyst would save equipment space, simplify the process flow, and reduce costs, with significant social benefits.

[0003] Among the many denitrification and VOCs removal catalysts, manganese-based catalysts are inexpensive, exhibit excellent VOCs catalytic oxidation activity and SCR denitrification activity, and have a high degree of overlap in their active temperature windows, making them highly promising as synergistic denitrification catalysts. However, a drawback is the over-oxidation of ammonia to nitrous oxide (N2O) during the SCR process, which reduces nitrogen selectivity and hinders their widespread use.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide a composite functional coating catalyst and a preparation method thereof, adopting a design concept of multiple coatings and sequential energization to prepare a new catalyst for synergistically removing NOx and benzene-related VOCs from industrial exhaust gas, achieving high nitrogen selectivity.

[0006] In order to achieve the above objectives, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for preparing a composite functional coating catalyst, which comprises at least the following steps in sequence: preparing a carrier coated with titanic acid, loading a catalytic oxidation active component, and coating a second active component.

[0008] Furthermore, the titanic acid-coated carrier is prepared by soaking the carrier in a titanium alkoxide solution for 0.5 to 3 hours, removing and draining the solution, and then passing superheated steam through the solution for 0.5 to 3 hours to obtain the titanic acid-coated carrier. The soaking time is preferably 1 hour, and the passing of superheated steam is preferably 1.5 hours.

[0009] Preferably, the carrier comprises a prepared and shaped plate-type, honeycomb-type or carrier with a specific geometric structure.

[0010] Preferably, the raw material of the carrier includes one or more of molecular sieve, titanium dioxide or porous ceramics.

[0011] Preferably, the carrier is pretreated before being placed in the titanium alkoxide solution; preferably, the pretreatment is to remove ash, clean and dry the carrier.

[0012] Furthermore, the amount of superheated steam introduced is 1.05 to 10 times the chemical consumption.

[0013] Preferably, the amount of superheated steam introduced is 3 to 5 times the chemical consumption.

[0014] Furthermore, the reaction temperature is 80-180°C.

[0015] Preferably, the reaction temperature is not lower than the boiling point of the alcohols produced by the reaction under the operating pressure, which can accelerate the reaction process.

[0016] The preparation of the titanic acid-coated carrier provides an active carrier and utilizes the strong bonding force of its own hydroxyl group to firmly bond it to the structural carrier, while providing abundant active component bonding sites for the step of loading the catalytic oxidation active component.

[0017] Furthermore, the loaded catalytic oxidation active component is prepared by soaking the titanic acid-coated carrier in a solution A of the catalytic oxidation active component for 0.5 to 2 hours, drying at 55 to 90° C. for 6 to 24 hours, and then calcining at 310 to 380° C. for 2 to 6 hours.

[0018] Preferably, the calcination temperature is 350±5° C., and the calcination time is 3 hours.

[0019] Preferably, the solution A comprises a mixed solution of one or more of copper acetate, manganese acetate, sodium acetate and citric acid.

[0020] Preferably, in the mixed solution, the molar ratio of copper acetate, manganese acetate, sodium acetate and citric acid is 5-7:10-12:0.5-1.5:11-18; more preferably, the molar ratio of copper acetate, manganese acetate, sodium acetate and citric acid is 6:12:1:11-18.

[0021] Preferably, the temperature of the mixed solution is controlled between 40°C and 50°C, with a total solute concentration of 280 g / L to 350 g / L. Increasing the temperature of the mixed liquid accelerates solute dissolution and improves solubility, while also reducing the liquid's viscosity and enhancing the wetting effect. Excessively high liquid temperatures accelerate the volatilization of acidic gases, leading to premature precipitation of solute components. On the other hand, excessively low liquid temperatures make it difficult for solutes to dissolve. Therefore, optimal overall liquid conditions are achieved in the 40°C to 50°C temperature range.

[0022] Preferably, the drying temperature is 65-80° C., and the drying time is 16-20 hours.

[0023] During the drying process, as the acidic gas evaporates, the active components Cu, Mn, and Na are deposited in the form of citrate and evenly dispersed on the surface and internal pores of the support.

[0024] The two steps of preparing the titanic acid-coated carrier and loading the catalytic oxidation active components fully utilize the strong bonding force between the rich hydroxyl groups of titanic acid and copper and manganese ions, making it highly dispersed and tightly bonded to titanium atoms. After the above treatment process, a highly active VOCs removal catalyst is obtained, which also has good NOx removal efficiency, but poor SCR nitrogen selectivity.

[0025] Furthermore, the coating of the second active component is carried out by soaking the product of the loaded catalytic oxidation active component in mixed liquid B for 0.5 to 2 hours, taking it out and draining it, drying it at 80 to 150° C. for 1 to 6 hours, and then calcining it at 310 to 420° C. for 2 to 6 hours.

[0026] Preferably, the mixed liquid B comprises a mixed solution of iron acetate and vanadium oxalate.

[0027] Preferably, the molar ratio of the iron acetate to the vanadium oxalate is 1:15-20.

[0028] Preferably, the total solute concentration of the mixed liquid B is 55 to 165 g / L.

[0029] The applicant has found that the addition of iron can inhibit the agglomeration of the active component vanadium and reduce the cluster size, thereby improving the coating effect and enhancing the NH3-SCR activity in the low-temperature section.

[0030] Preferably, the calcination temperature is 380-400° C., and the calcination time is 5 hours.

[0031] The design principle of the coated second active component is to utilize its strong adsorption effect on NH3, so that the vast majority of NH3 in the gas is preferentially adsorbed on the outer coating layer of the catalyst to participate in the SCR reaction, thereby avoiding excessive oxidation by the inner layer active components copper and manganese to produce nitrous oxide, thereby significantly improving nitrogen selectivity.

[0032] The coating structure design not only significantly improves the catalyst's nitrogen selectivity, but also eliminates the inhibitory effect of NH3 on the VOC oxidation process. This enhanced effect offsets the adverse effects of the outer coating on mass transfer, maintaining the catalyst's VOC removal activity.

[0033] The present invention also provides a composite functional coating catalyst prepared by the preparation method, which is used for collaborative removal of NOx and benzene series VOCs.

[0034] Compared to the existing technology, the catalyst structure of the present invention adopts a coating process, which utilizes the strong bonding force of titanate hydroxyl groups to achieve a strong bond between the structural carrier, the active carrier, and the active component. In the design of the active component coating, a separate energization method is adopted, and a copper-manganese catalytic oxidation functional layer mainly for VOC removal and an NH3-SCR coating layer mainly for NOx removal are sequentially coated to obtain a composite functional coating catalyst. The catalytic oxidation temperature of the obtained catalyst is T 90 As low as 195°C, the NOx conversion rate and N2 selectivity at this temperature are as high as 95% and 98% respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0036] Figure 1 This is a curve diagram of NOx and toluene conversion rates at different temperatures for the catalyst obtained in Example 5. DETAILED DESCRIPTION

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0038] Where the ratio of substances in the examples is not indicated, it should be understood that they can be matched in any ratio. Where the unit of the ratio of substances is not indicated, it should be understood that it is a mass ratio.

[0039] Catalyst NOx removal activity test conditions: reaction temperature 150-300°C, catalyst loading volume 5L, simulated gas flow rate 25Nm 3 / h, NO concentration 500ppm, ammonia nitrogen molar ratio = 1.0, oxygen concentration 6.0%, water content 8.0%, nitrogen as the balance gas.

[0040] The test conditions for the catalyst VOCs removal activity test using toluene as a model compound are: reaction temperature 150-300°C, catalyst loading volume 5L, simulated gas flow rate 25Nm 3 / h, the VOCs model compound toluene concentration was 1000ppm, the oxygen concentration was 6.0%, the water content was 8.0%, and nitrogen was the balance gas.

[0041] Example 1

[0042] A method for preparing a composite functional coating catalyst:

[0043] (1) The honeycomb ceramic carrier after ash removal, cleaning and drying was immersed in a titanium n-butoxide solution for 3 hours, taken out and drained, and then superheated steam with a chemical consumption of 10 times was introduced and reacted at 80° C. for 3 hours to obtain a carrier coated with titanic acid.

[0044] (2) Soak the support obtained in step (1) in a mixed solution of copper acetate, manganese acetate, sodium acetate, and citric acid in a molar ratio of 6:12:1:18 for 2 hours. The temperature of the mixed solution is controlled to be 50°C and the total solute concentration is 350 g / L. After draining, the support is dried at 90°C for 6 hours. The dried product is then calcined at 310°C for 6 hours.

[0045] (3) Soaking the product obtained in step (2) in a mixed solution of ferric acetate and vanadyl oxalate at a molar ratio of 1:20 for 2 hours, wherein the total solute concentration of the mixed solution is 165 g / L, taking it out and draining it, drying it at 150° C. for 1 hour, and calcining the dried product at 420° C. for 2 hours.

[0046] After calcination, a composite functional coating catalyst was obtained for the synergistic removal of NOx and benzene-related VOCs. The catalyst performance is shown in Table 1.

[0047] Example 2

[0048] A method for preparing a composite functional coating catalyst:

[0049] (1) The honeycomb ceramic carrier after ash removal, cleaning and drying was placed in a titanium isopropoxide solution and soaked for 0.5 hours. After being taken out and drained, superheated steam with a chemical consumption of 1.05 times was introduced and reacted at 180° C. for 0.5 hours to obtain a carrier coated with titanic acid.

[0050] (2) Soak the support obtained in step (1) in a mixed solution of copper acetate, manganese acetate, sodium acetate, and citric acid in a molar ratio of 6:12:1:11 for 0.5 hours. The temperature of the mixed solution is controlled to be 40°C and the total solute concentration is 350 g / L. After draining, the support is dried at 55°C for 24 hours. The dried product is then calcined at 380°C for 2 hours.

[0051] (3) The product obtained in step (2) was soaked in a mixed solution of ferric acetate and vanadium oxalate with a molar ratio of 1:15 for 0.5 hours, and the total solute concentration of the mixed solution was 55 g / L. After being taken out and drained, the dried support was dried at 80°C for 6 hours, and the dried support was calcined at 310°C for 6 hours.

[0052] After calcination, a composite functional coating catalyst was obtained for the synergistic removal of NOx and benzene-related VOCs. The catalyst performance is shown in Table 1.

[0053] Example 3

[0054] A method for preparing a composite functional coating catalyst:

[0055] (1) The honeycomb ceramic carrier after ash removal, cleaning and drying was placed in a titanium n-butoxide solution and soaked for 1 hour. After being taken out and drained, superheated steam 3 times the chemical consumption was introduced and reacted at 170°C for 1.5 hours to obtain a carrier coated with titanic acid.

[0056] (2) Soak the support obtained in step (1) in a mixed solution of copper acetate, manganese acetate, sodium acetate, and citric acid in a molar ratio of 6:12:1:16 for 1 hour. The temperature of the mixed solution is controlled to be 45°C and the total solute concentration is 350 g / L. After draining, the support is dried at 65°C for 16 hours. The dried product is then calcined at 350°C for 3 hours.

[0057] (3) The product obtained in step (2) was soaked in a mixed solution of ferric acetate and vanadyl oxalate with a molar ratio of 1:18 for 1.5 hours, and the total solute concentration of the mixed solution was 155 g / L. After being taken out and drained, the dried support was dried at 100°C for 3 hours, and the dried support was calcined at 380°C for 5 hours.

[0058] After calcination, a composite functional coating catalyst was obtained for the synergistic removal of NOx and benzene-related VOCs. The catalyst performance is shown in Table 1.

[0059] Example 4

[0060] A method for preparing a composite functional coating catalyst:

[0061] (1) The plate-type titanium dioxide support after ash removal, cleaning and drying is placed in a titanium n-butoxide solution and soaked for 1 hour. After being taken out and drained, superheated steam 5 times the chemical consumption is introduced and reacted at 170°C for 1.5 hours to obtain a support coated with titanic acid.

[0062] (2) Soak the support obtained in step (1) in a mixed solution of copper acetate, manganese acetate, sodium acetate, and citric acid in a molar ratio of 6:12:1:16 for 1 hour. The temperature of the mixed solution is controlled to be 45°C and the total solute concentration is 350 g / L. After draining, the support is dried at 80°C for 20 hours. The dried product is then calcined at 355°C for 3 hours.

[0063] (3) The product obtained in step (2) was soaked in a mixed solution of ferric acetate and vanadyl oxalate with a molar ratio of 1:18 for 1.5 hours, and the total solute concentration of the mixed solution was 155 g / L. After being taken out and drained, the dried support was dried at 120°C for 3 hours, and the dried support was calcined at 420°C for 5 hours.

[0064] After calcination, a composite functional coating catalyst was obtained for the synergistic removal of NOx and benzene-related VOCs. The catalyst performance is shown in Table 1.

[0065] Example 5

[0066] A method for preparing a composite functional coating catalyst:

[0067] (1) The honeycomb ceramic support after ash removal, cleaning and drying is placed in a titanium n-butoxide solution and soaked for 1 hour. After being taken out and drained, superheated steam 5 times the chemical consumption is introduced and reacted at the boiling point of the generated alcohol for 2.5 hours to obtain a support coated with titanic acid.

[0068] (2) Soak the support obtained in step (1) in a mixed solution of copper acetate, manganese acetate, sodium acetate, and citric acid in a molar ratio of 6:12:1:17 for 1 hour. The temperature of the mixed solution is controlled to be 50°C and the total solute concentration is 350 g / L. After draining, the support is dried at 80°C for 18 hours. The dried product is then calcined at 350°C for 3 hours.

[0069] (3) The product obtained in step (2) was soaked in a mixed solution of ferric acetate and vanadyl oxalate with a molar ratio of 1:18 for 1 hour, and the total solute concentration of the mixed solution was 155 g / L. After being taken out and drained, the dried support was dried at 120°C for 3 hours, and the dried support was calcined at 420°C for 3 hours.

[0070] After calcination, a composite functional coating catalyst for synergistic removal of NOx and benzene VOCs was obtained. The performance of the obtained catalyst is shown in Figure 1 and Table 1.

[0071] Example 6

[0072] A method for preparing a composite functional coating catalyst:

[0073] (1) The honeycomb ceramic carrier after ash removal, cleaning and drying is placed in a titanium n-butoxide solution and soaked for 1 hour. After being taken out and drained, superheated steam 5 times the chemical consumption is introduced and reacted for 2.5 hours at a temperature not lower than the boiling point of the generated alcohol to obtain a carrier coated with titanic acid.

[0074] (2) Soak the support obtained in step (1) in a mixed solution of copper acetate, manganese acetate, sodium acetate, and citric acid in a molar ratio of 5:11:1.5:15 for 2 hours. The temperature of the mixed solution is controlled to be 50°C and the total solute concentration is 350 g / L. After draining, the support is dried at 80°C for 16 hours. The dried product is calcined at 350°C for 3 hours.

[0075] (3) The product obtained in step (2) was soaked in a mixed solution of ferric acetate and vanadyl oxalate with a molar ratio of 1:18 for 1 hour, and the total solute concentration of the mixed solution was 155 g / L. After being taken out and drained, the dried support was dried at 120°C for 3 hours, and the dried support was calcined at 400°C for 5 hours.

[0076] After calcination, a composite functional coating catalyst was obtained for the synergistic removal of NOx and benzene-related VOCs. The catalyst performance is shown in Table 1.

[0077] Comparative Example 1

[0078] A method for preparing a catalyst for synergistic removal of NOx and benzene-related VOCs:

[0079] (1) The honeycomb ceramic carrier after ash removal, cleaning and drying was placed in a titanium n-butoxide solution and soaked for 1 hour. After being taken out and drained, superheated steam 5 times the chemical consumption was introduced and reacted at 170°C for 1.5 hours to obtain a carrier coated with titanic acid.

[0080] (2) Soak the support obtained in step (1) in a mixed solution of copper acetate, manganese acetate, sodium acetate, and citric acid in a molar ratio of 6:12:1:16 for 1 hour. The temperature of the mixed solution is controlled to be 45°C and the total solute concentration is 350 g / L. After draining, the support is dried at 80°C for 20 hours. The dried support is then calcined at 355°C for 3 hours.

[0081] The catalyst was obtained after calcination. The properties of the obtained catalyst are shown in Table 1.

[0082] Comparative Example 2

[0083] A method for preparing a catalyst for synergistic removal of NOx and benzene-related VOCs:

[0084] (1) The honeycomb ceramic after ash removal, cleaning and drying was placed in a titanium n-butoxide solution and soaked for 1 hour. After being taken out and drained, superheated steam 5 times the chemical consumption was introduced and reacted at 170° C. for 1.5 hours to obtain a support coated with titanic acid.

[0085] (2) The carrier obtained in step (1) was soaked in a mixed solution of ferric acetate and vanadyl oxalate with a molar ratio of 1:18 for 1.5 hours, and the total solute concentration of the mixed solution was 155 g / L. After being taken out and drained, the carrier was dried at 120°C for 3 hours, and the dried carrier was calcined at 420°C for 5 hours.

[0086] The catalyst was obtained after calcination. The properties of the obtained catalyst are shown in Table 1.

[0087] Comparative Example 3

[0088] A method for preparing a catalyst for synergistic removal of NOx and benzene-related VOCs:

[0089] (1) The ash-removed, cleaned, and dried honeycomb ceramic substrate was immersed in a mixed solution of copper acetate, manganese acetate, sodium acetate, and citric acid in a molar ratio of 6:12:1:16 for 1 hour. The temperature of the mixed solution was controlled to be 45°C and the total solute concentration was 350 g / L. The substrate was drained and dried at 80°C for 20 hours. The dried product was calcined at 355°C for 3 hours.

[0090] (2) The product obtained in step (1) was soaked in a mixed solution of ferric acetate and vanadyl oxalate with a molar ratio of 1:18 for 1.5 hours, and the total solute concentration of the mixed solution was 155 g / L. After being taken out and drained, the dried support was dried at 120°C for 3 hours, and the dried support was calcined at 420°C for 5 hours.

[0091] The catalyst was obtained after calcination. The properties of the obtained catalyst are shown in Table 1.

[0092] Table 1 Performance test results of catalysts at 240°C for Examples 1 to 6 and Comparative Examples 1 to 3

[0093]

[0094] Depend on Figure 1 As can be seen from Table 1, the catalysts obtained in Examples 1 to 6 of the present invention have a lower VOCs catalytic oxidation removal temperature and exhibit excellent NOx removal rate and N2 selectivity.

[0095] The results of comparative examples 1 to 3 show that in the catalyst preparation process, the active carrier layer, VOCs catalytic oxidation layer, and NH3-SCR coating layer are indispensable. Only by close cooperation and division of labor among the three can efficient removal of NOx and VOCs and high N2 selectivity be achieved.

[0096] Please note that the technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. The above embodiments only express several implementation methods of the present application. The description is relatively specific and detailed, but it cannot be understood as a limitation on the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, without departing from the concept of this application, several variations and improvements can be made, which all fall within the scope of protection of this application. Therefore, the scope of protection of the patent in this application shall be based on the attached claims.

Claims

1. A method for preparing a composite functional coating catalyst, characterized in that: The method comprises at least the following steps: preparing a support coated with titanic acid, loading a catalytic oxidation active component, and coating a second active component; The preparation of the titanic acid-coated carrier comprises placing the carrier in a titanium alkoxide solution and soaking it for 0.5 to 3 hours, taking it out and draining it, and then passing superheated steam into it for a reaction of 0.5 to 3 hours to obtain the titanic acid-coated carrier; wherein the carrier includes a prepared plate-shaped, honeycomb-shaped or specific geometric structure carrier; the raw material of the carrier includes one or more of molecular sieve, titanium dioxide or porous ceramics; The loaded catalytic oxidation active component is prepared by placing the titanic acid-coated carrier in a solution A of the catalytic oxidation active component and soaking it for 0.5 to 2 hours, drying it at 55 to 90° C. for 6 to 24 hours, and then calcining it at 310 to 380° C. for 2 to 6 hours; wherein the solution A comprises a mixed solution of copper acetate, manganese acetate, sodium acetate and citric acid; the coated second active component is prepared by placing the product of the loaded catalytic oxidation active component in a mixed liquid B and soaking it for 0.5 to 2 hours, taking it out and draining it, drying it at 80 to 150° C. for 1 to 6 hours, and then calcining it at 310 to 420° C. for 2 to 6 hours; wherein the mixed liquid B comprises a mixed solution of iron acetate and vanadium oxalate.

2. The preparation method according to claim 1, characterized in that The amount of superheated steam introduced is 1.05 to 10 times the chemical consumption.

3. The preparation method according to claim 2, characterized in that The amount of superheated steam introduced is 3 to 5 times the chemical consumption.

4. The preparation method according to claim 1, characterized in that The reaction temperature is 80-180°C.

5. The preparation method according to claim 4, characterized in that The reaction temperature is not lower than the boiling point of the alcohols produced by the reaction under the operating pressure.

6. The preparation method according to claim 1, characterized in that In the mixed solution, the molar ratio of copper acetate, manganese acetate, sodium acetate and citric acid is 5-7:10-12:0.5-1.5:11-18.

7. The preparation method according to claim 6, characterized in that The temperature of the mixed solution is controlled at 40-50° C., and the total solute concentration is 280-350 g / L.

8. The preparation method according to claim 1, characterized in that The molar ratio of the iron acetate to the vanadium oxalate is 1:15-20.

9. The preparation method according to claim 8, characterized in that The total solute concentration of the mixed liquid B is 55-165 g / L.

10. A composite functional coating catalyst prepared by the preparation method according to any one of claims 1 to 9, characterized in that: Used to remove NOx and benzene VOCs simultaneously.

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