A catalyst for synergistically removing toluene and NOx, and a preparation method and application thereof

Abstract

The application provides a catalyst for synergistically removing toluene and NOx, a preparation method and application thereof, and belongs to the technical field of atmospheric pollution control. The catalyst comprises a MnCuTi mixed oxide, has a particle size of 250-380 mu m, a specific surface area of 155.10-164.25 m 2 / g, a pore volume of 0.270-0.281 cm 3 / g, and an average pore size of 6.672-6.951 mm. The preparation method comprises the following steps: mixing copper nitrate, manganese nitrate solution, deionized water and glacial acetic acid with ethanol to obtain solution A; dissolving tetrabutyl titanate in ethanol to obtain solution B; adding solution B into solution A drop by drop under stirring to form a sol and continuing to stir; aging, drying, grinding and calcining; and tabletting and sieving to obtain the catalyst. The catalyst is used for synergistically removing toluene and NOx, has low raw material cost, simple and controllable preparation process, strong repeatability, good catalytic activity and high selectivity.

Description

Technical Field

[0001] This invention belongs to the field of air pollution control technology, and particularly relates to a catalyst for the synergistic removal of toluene and NOx, its preparation method, and its application. Background Technology

[0002] In recent years, air pollution has become increasingly serious, and environmental problems have frequently emerged. Nitrogen oxides (NOx) and volatile organic compounds (VOCs) are the main pollutants causing air pollution, leading to various environmental problems such as smog, acid rain, and photochemical smog, and posing significant harm to human health. Therefore, reducing NOx and VOC emissions is urgent and of great significance to improving air quality and the environment in my country.

[0003] Ammonia catalytic oxidation (NH3-SCR) is currently the most mature denitrification technology. Among various VOCs, toluene has been studied in greater depth, and major VOC emission sources, such as coal-fired power plants, the steel industry, the printing industry, and leather production, all contain toluene. Catalytic oxidation technology is currently considered the optimal technology for toluene removal. Since the activity temperature windows of NH3-SCR and toluene catalytic oxidation are close, and NH3-SCR catalysts also show activity for toluene oxidation, the synergistic removal of toluene and NOx is an economical and practical choice.

[0004] Catalysts used for the synergistic removal of toluene and NOx are mainly divided into two categories: noble metal catalysts and metal oxide catalysts. Although noble metal catalysts have excellent catalytic activity, they are limited in resources, expensive, and prone to sintering and poisoning. On the other hand, metal oxide catalysts, especially Mn-based catalysts, have good thermal stability and are inexpensive. Their surfaces have various oxidation states of metal ions and lattice oxygen, resulting in abundant surface active sites, making them a better choice for the synergistic removal of toluene and NOx.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a catalyst for the synergistic removal of toluene and NOx, its preparation method, and its application, in order to solve the above-mentioned problems.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] This invention provides a catalyst for the synergistic removal of toluene and NOx, the catalyst comprising a MnCuTi mixed oxide with a particle size of 250-380 μm and a specific surface area of ​​155.10-164.25 m². 2 / g, pore volume is 0.270-0.281cm³ 3 / g, with an average pore size of 6.672-6.951mm.

[0009] The present invention also provides a method for preparing the catalyst described above: mixing copper nitrate, manganese nitrate solution, deionized water, glacial acetic acid, and ethanol to obtain solution A;

[0010] Tetrabutyl titanate was dissolved in ethanol to obtain solution B;

[0011] Solution B is added to solution A under stirring to form a sol, and stirring continues. After aging, drying, grinding, calcination, tableting, and sieving, the product is obtained.

[0012] Furthermore, the tableting process involves placing the calcined product in a mold, maintaining it under a pressure of 15-25 MPa for 5-10 minutes, and then grinding and sieving it through a 40-60 mesh sieve to obtain 40-60 mesh particulate catalyst.

[0013] The resulting catalyst fully utilizes the synergistic effect among the three metals Mn, Cu, and Ti, forming abundant oxygen vacancies and active sites, which is beneficial for the adsorption of reactive oxygen species and the improvement of low-temperature synergistic reaction activity.

[0014] As another technical solution, further, the grinding process involves passing the product through a 40-mesh sieve and the product through a 100-mesh sieve respectively; the tableting process involves placing the product passing through the 40-mesh sieve and the product passing through the 100-mesh sieve alternately in a mold, maintaining a pressure of 15-25 MPa for 5-10 minutes, and then taking them out to grind and sieve through a 40-60 mesh sieve to obtain 40-60 mesh particulate catalyst. This process can maximize the balance between catalyst particle formation and catalytic activity, while also resulting in better catalytic activity and selectivity.

[0015] Furthermore, in solution A, the atomic molar ratio of Mn to Cu is 2-4:1, and the atomic molar ratio of the sum of Mn and Cu to Ti is 1:3-4.

[0016] Furthermore, the volume ratio of glacial acetic acid, deionized water and ethanol added to solution A is 1:1:2.5-3.

[0017] Furthermore, the volume ratio of tetrabutyl titanate to ethanol in solution B is 1:1-1.5.

[0018] Furthermore, the drying temperature is 70-90℃, and the drying time is 12-20h.

[0019] Furthermore, the calcination temperature is 430-470℃, and the calcination time is 4-5 hours.

[0020] Preferably, the heating rate during calcination is 5-10℃ / min;

[0021] Preferably, the calcination is carried out in an air atmosphere.

[0022] The present invention also provides an application of the catalyst described herein, namely, in a fixed-bed reactor, wherein the gas phase includes NO, NH3, O2, C7H8 and N2, the flue gas space velocity is 40000-60000 mL / (g·h), and the reaction temperature is 180-300℃.

[0023] Compared to existing technologies, the catalyst for the synergistic removal of toluene and NOx provided by this invention uses low-cost raw materials, has a simple and controllable preparation process, and high reproducibility. This catalyst possesses advantages such as excellent redox performance, uniformly dispersed active sites, large specific surface area, average pore size, and pore volume. Furthermore, it is an environmentally friendly catalyst, exhibiting good catalytic activity and high selectivity in the synergistic removal of toluene and NOx. Simultaneously, the catalyst has wide applicability, is simple to operate, and has good potential for industrial application. Attached Figure Description

[0024] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0025] Figure 1 The graphs show the activity evaluation of the catalysts obtained in Examples 1-4 for toluene removal.

[0026] Figure 2 The graphs show the NOx removal activity evaluation of the catalysts obtained in Examples 1-4;

[0027] Figure 3 The N2 selectivity evaluation charts are for the catalysts obtained in Examples 1-4;

[0028] Figure 4 The graph shows the CO2 selectivity evaluation of the catalysts obtained in Examples 1-4. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Where the proportions of substances in the embodiments are not specified, it should be understood that they can be matched in any proportion. Where the units of proportion of substances are not specified, it should be understood as mass ratios.

[0031] Example 1

[0032] A catalyst for the synergistic removal of toluene and NOx, wherein the catalyst is Mn 1.25 Cu 0.75 / TiO2, with a particle size of 345μm and a specific surface area of ​​164.247m². 2 / g, pore volume is 0.2739cm³ 3 / g, with an average pore size of 6.672mm. The preparation method is as follows:

[0033] S1: Take 1.14g of copper nitrate trihydrate, 2.79g of 50% manganese nitrate solution, 8mL of deionized water, and 8mL of glacial acetic acid and add them to 23mL of ethanol. Stir at room temperature until completely dissolved to form solution A.

[0034] S2: Take 17 mL of tetrabutyl titanate and add it to 23 mL of ethanol. Stir at room temperature until the mixture is homogeneous to form solution B.

[0035] S3: Under vigorous stirring, solution B is added dropwise to solution A, stirred at room temperature for 3 hours, and then aged for 2 hours to obtain a sol. The sol is then dried in a 70℃ oven for 20 hours and ground into powder.

[0036] S4: Under air atmosphere, the product of S3 was placed in a tube furnace and calcined at 450°C for 5 hours by a programmed temperature increase from room temperature. Finally, it was cooled to room temperature to obtain the MnCuTi mixed oxide catalyst.

[0037] S5: Place the catalyst prepared in S4 into a mold, maintain it under a pressure of 15 MPa for 10 minutes, then slowly transfer the pressed sample to a 40-60 mesh sieve for grinding and sieving to obtain 40-60 mesh catalyst particles, named Mn. 1.25 Cu 0.75 / TiO2.

[0038] The catalyst particles obtained from S5 were loaded into a fixed-bed continuous flow quartz reactor, and simulated flue gas at atmospheric pressure was introduced with NO concentration of 500 ppm, NH3 concentration of 500 ppm, O2 content of 10.0 vol.%, C7H8 concentration of 100 ppm, N2 as balance gas, reaction temperature of 180-300℃, and reaction space velocity controlled at 60000 mL / (g·h).

[0039] Test results: At steady state (240℃), the conversion rate of toluene was 99.29%, and the conversion rate of NOx was 66.48%.

[0040] Example 2

[0041] A catalyst for the synergistic removal of toluene and NOx, wherein the catalyst is Mn 1.5 Cu 0.5 / TiO2, with a particle size of 291μm and a specific surface area of ​​163.477m². 2 / g, pore volume is 0.2808cm³ 3 / g, with an average pore size of 6.8719mm. The preparation method is as follows:

[0042] S1: Take 0.75g of copper nitrate trihydrate, 3.36g of 50% manganese nitrate solution, 8mL of deionized water, and 8mL of glacial acetic acid and add them to 23mL of ethanol. Stir at room temperature until completely dissolved to form solution A.

[0043] S2: Take 17 mL of tetrabutyl titanate and add it to 23 mL of ethanol. Stir at room temperature until the mixture is homogeneous to form solution B.

[0044] S3: Under vigorous stirring, add solution B dropwise to solution A, stir at room temperature for 3 hours, then age for 2 hours to obtain a sol. Dry the sol in a 70℃ oven for 20 hours, then grind it into powder.

[0045] S4: Under air atmosphere, the product of S3 was placed in a tube furnace and calcined at 450°C for 5 hours by a programmed temperature increase from room temperature. Finally, it was cooled to room temperature to obtain the MnCuTi mixed oxide catalyst.

[0046] S5: Place the catalyst prepared in S4 into a mold, maintain it under a pressure of 15 MPa for 10 minutes, then slowly transfer the pressed sample to a 40-60 mesh sieve for grinding and sieving to obtain 40-60 mesh catalyst particles, named Mn. 1.5 Cu 0.5 / TiO2.

[0047] The catalyst particles obtained from S5 were loaded into a fixed-bed continuous flow quartz reactor, and simulated flue gas at atmospheric pressure was introduced with NO concentration of 500 ppm, NH3 concentration of 500 ppm, O2 content of 10.0 vol.%, C7H8 concentration of 100 ppm, N2 as balance gas, reaction temperature of 180-300℃, and reaction space velocity controlled at 60000 mL / (g·h).

[0048] Test results: At steady state (240℃), the conversion rate of toluene was 99.83%, and the conversion rate of NOx was 87.29%.

[0049] Example 3

[0050] A catalyst for the synergistic removal of toluene and NOx, wherein the catalyst is Mn 1.75 Cu 0.25 / TiO2, with a particle size of 367μm and a specific surface area of ​​155.098m². 2 / g, pore volume is 0.2695cm³ 3 / g, with an average pore size of 6.9509mm. The preparation method is as follows:

[0051] S1: Take 0.38g of copper nitrate trihydrate, 3.91g of 50% manganese nitrate solution, 8mL of deionized water, and 8mL of glacial acetic acid and add them to 23mL of ethanol. Stir at room temperature until completely dissolved to form solution A.

[0052] S2: Take 17 mL of tetrabutyl titanate and add it to 23 mL of ethanol. Stir at room temperature until the mixture is homogeneous to form solution B.

[0053] S3: Under vigorous stirring, add solution B dropwise to solution A, stir at room temperature for 3 hours, then age for 2 hours to obtain a sol. Dry the sol in a 70℃ oven for 20 hours, then grind it into powder.

[0054] S4: Under air atmosphere, the product of S3 was placed in a tube furnace and calcined at 450°C for 5 hours by a programmed temperature increase from room temperature. Finally, it was cooled to room temperature to obtain the MnCuTi mixed oxide catalyst.

[0055] S5: Place the catalyst prepared in S4 into a mold, maintain it under a pressure of 15 MPa for 10 minutes, then slowly transfer the pressed sample to a 40-60 mesh sieve for grinding and sieving to obtain 40-60 mesh catalyst particles, named Mn. 1.75 Cu 0.25 / TiO2.

[0056] The catalyst particles obtained from S5 were loaded into a fixed-bed continuous flow quartz reactor, and simulated flue gas at atmospheric pressure was introduced with NO concentration of 500 ppm, NH3 concentration of 500 ppm, O2 content of 10.0 vol.%, C7H8 concentration of 100 ppm, N2 as balance gas, reaction temperature of 180-300℃, and reaction space velocity controlled at 60000 mL / (g·h).

[0057] Test results: At steady state (240℃), the conversion rate of toluene was 98.24%, and the conversion rate of NOx was 85.05%.

[0058] Example 4

[0059] A catalyst for the synergistic removal of toluene and NOx, wherein the catalyst is Mn 1.5 Cu 0.5 / TiO2-γ, with a particle size of 278 μm and a specific surface area of ​​165.328 m². 2 / g, pore volume is 0.2845cm³ 3 / g, with an average pore size of 6.8392mm. The preparation method is as follows:

[0060] S1: Take 0.75g of copper nitrate trihydrate, 3.36g of 50% manganese nitrate solution, 8mL of deionized water, and 8mL of glacial acetic acid and add them to 23mL of ethanol. Stir at room temperature until completely dissolved to form solution A.

[0061] S2: Take 17 mL of tetrabutyl titanate and add it to 23 mL of ethanol. Stir at room temperature until the mixture is homogeneous to form solution B.

[0062] S3: Under vigorous stirring, solution B is added dropwise to solution A, stirred at room temperature for 3 hours, and then aged for 2 hours to obtain a sol. The sol is dried in a 70℃ oven for 20 hours, ground into powder, and passed through a 40-mesh sieve and a 100-mesh sieve, respectively.

[0063] S4: Under air atmosphere, two products of different mesh sizes from S3 were placed in a tube furnace and calcined at 450°C for 5 hours with a temperature program from room temperature. Finally, the temperature was lowered to room temperature to obtain two MnCuTi mixed oxide catalysts of different mesh sizes.

[0064] S5: The two MnCuTi mixed oxide catalysts with different mesh sizes prepared in S4 were placed alternately in a mold. After being held at a pressure of 15 MPa for 10 min, the pressed samples were slowly removed and ground through a 40-60 mesh sieve to obtain 40-60 mesh catalyst particles, named Mn 1.5 Cu 0.5 / TiO2-γ.

[0065] The catalyst particles obtained from S5 were loaded into a fixed-bed continuous flow quartz reactor, and simulated flue gas at atmospheric pressure was introduced with NO concentration of 500 ppm, NH3 concentration of 500 ppm, O2 content of 10.0 vol.%, C7H8 concentration of 100 ppm, N2 as balance gas, reaction temperature of 180-300℃, and reaction space velocity controlled at 60000 mL / (g·h).

[0066] Test results: At steady state (240℃), the conversion rate of toluene was 100%, and the conversion rate of NOx was 90.21%.

[0067] Table 1 Comparison of pore structures of catalysts obtained in Examples 1-4

[0068]

[0069] The MnCuTi mixed oxide catalysts prepared in Examples 1-4 are Mn 1.25 Cu 0.75 / TiO2、Mn 1.5 Cu 0.5 / TiO2、Mn 1.75 Cu 0.25 / TiO2、Mn 1.5 Cu 0.5 The performance parameters of / TiO2-γ are shown in Table 1. It can be seen that the catalysts prepared by the method provided in this invention all have high specific surface area and pore volume.

[0070] Its activity evaluation test results are as follows Figure 1 and Figure 2 As shown, its selectivity is as follows Figure 3 and Figure 4 As shown.

[0071] Depend on Figure 1-2 It can be seen that the catalyst prepared by the method provided by the present invention can achieve complete conversion of toluene at 240°C, and the NOx conversion rate is also relatively high, especially exceeding 90% in Example 4. Furthermore, when the MnCu ratio is 1.5:0.5, i.e., the catalyst is Mn... 1.5 Cu 0.5 / TiO2 and Mn 1.5 Cu 0.5 The catalyst exhibits the best overall activity when the catalyst is in the / TiO2-γ ratio.

[0072] Depend on Figure 3-4 It is known that the catalyst prepared by the method provided by the present invention is best in Example 4, with N2 selectivity reaching about 80% and CO2 selectivity reaching 73% at 240°C, followed by Example 2.

[0073] Please note that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments only illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A catalyst for the synergistic removal of toluene and NOx, characterized in that, The catalyst comprises a MnCuTi mixed oxide, with a particle size of 250-380 μm and a specific surface area of ​​155.10-164.25 m². 2 / g, pore volume is 0.270-0.281cm³ 3 / g, with an average pore size of 6.672-6.951mm; The catalyst is prepared by mixing copper nitrate, manganese nitrate solution, deionized water, glacial acetic acid, and ethanol to obtain solution A. Dissolve tetrabutyl titanate in ethanol to obtain solution B; Solution B is added to solution A under stirring to form a sol, and stirring continues. After aging, drying, grinding, calcination, tableting and sieving, the product is obtained. The tableting process involves placing the calcined product in a mold, maintaining it under a pressure of 15-25 MPa for 5-10 minutes, and then grinding and sieving it through a 40-60 mesh sieve to obtain 40-60 mesh particulate catalyst. The grinding process before calcination was followed by sieving through a 40-mesh sieve and a 100-mesh sieve, respectively. The tableting process involves placing the calcined product after passing through a 40-mesh sieve and the calcined product after passing through a 100-mesh sieve sequentially in a mold, maintaining the pressure at 15-25 MPa for 5-10 minutes, and then grinding and sieving the product through a 40-60 mesh sieve to obtain 40-60 mesh particulate catalyst. The atomic molar ratio of Mn to Cu in solution A is (2-4):1, and the atomic molar ratio of the sum of Mn and Cu to Ti is 1:(3-4). The calcination temperature is 430-470℃, and the calcination time is 4-5 hours; The heating rate for calcination is 5-10℃ / min; The calcination is carried out in an air atmosphere.

2. The catalyst according to claim 1, characterized in that, The volume ratio of glacial acetic acid, deionized water and ethanol added to solution A is 1:1:(2.5-3).

3. The catalyst according to claim 1, characterized in that, The volume ratio of tetrabutyl titanate to ethanol in solution B is 1:(1-1.5).

4. The catalyst according to claim 1, characterized in that, The drying temperature is 70-90℃, and the drying time is 12-20h.

5. The application of the catalyst according to claim 1, characterized in that, The experiment was conducted in a fixed-bed reactor, with the gas phase consisting of NO, NH3, O2, C7H8, and N2, and a flue gas space velocity of 40,000-60,000 mL / (g). h), the reaction temperature is 180-300℃.

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