WO2021092831A1 - Method for preparing scr denitration catalyst - Google Patents

Abstract

A method for preparing a SCR denitration catalyst, specifically comprising the following steps: (1) weighing an appropriate amount of self-made or existing MOF nanoparticles; (2) preparing an Si-MOF support; (3) and taking the Si-MOF support obtained above, dispersing same in deionized water, adding an appropriate amount of water-soluble polymer thereto, and after same has dissolved completely, adding a potassium permanganate solution, adding potassium permanganate drop by drop and stirring to obtain a SCR denitration catalyst. The described method is able to prepare a porous spherical structure SCR denitration catalyst that has a large specific surface area and a good catalytic performance.

Description

A preparation method of SCR denitration catalyst Technical field

The invention mainly relates to the fields of industrial catalysts, industrial chemicals and the like, and specifically relates to a preparation method of an SCR denitration catalyst.

Background technique

Metal-organic framework (MOF) material is a new type of porous material with a three-dimensional porous structure composed of metals as nodes and organisms as supporting frameworks. It has attracted a high degree of attention in the past ten years and is a hot topic in academic and industrialization. It plays an important role in the field of catalysis, chemical energy storage, and material separation.

The current treatment methods for nitrogen oxides in my country mainly use SNCR and SCR, and most of the other methods are still in the experimental research stage or the pilot stage. Both SNCR and SCR technologies use some reducing gases to reduce nitrogen oxides into harmless nitrogen and water. Compared with SNCR, it needs a large amount of reducing gas and higher temperature control, and has the problems of high ammonia escape rate and low denitration efficiency. Therefore, SCR denitration technology is more and more sought after by everyone, and it is also the most mainstream in the world today. Denitration method.

As a common SCR denitration material, manganese-based materials have good low-temperature catalytic effects, a wide temperature window, and have no adverse effects on the environment. They are the best choice for denitration catalysts in the industry in the future. However, with the current country's further improvement of environmental protection requirements, higher denitration efficiency and catalytic performance are required under low temperature conditions.

Summary of the invention

Aiming at the above shortcomings of the prior art, the present invention provides a novel composite material method for preparing an SCR catalyst, which can prepare a porous spherical structure with a large specific surface area and good catalytic performance in the actual production process.

The technical scheme of the present invention is a preparation method of SCR denitration catalyst, which specifically includes the following steps:

(1) Weigh an appropriate amount of homemade or existing MOF nanoparticles;

(2) Preparation of Si-MOF support: place MOF nanoparticles in absolute ethanol for ultrasonic dispersion treatment, add tetraethyl silicate and hexadecyltrimethoxysilane dropwise to it under magnetic stirring, and Continue to stir to coat the MOF nanoparticles with a layer of organic silicon film. Finally, the Si-MOF material covered with a layer of organic silicon film is washed with anhydrous ethanol and deionized water for multiple times and then dried to prepare the corresponding Si -MOF support body;

(3) Take the Si-MOF support obtained above, disperse it in deionized water, add an appropriate amount of water-soluble polymer to it, and add potassium permanganate solution after it is completely dissolved. Potassium permanganate is added dropwise Add it in the method and stir to obtain the SCR denitration catalyst.

The present invention is a typical composite material and core-shell structure. The inside is made of MOF material, the middle layer is a thin layer of organic silicon film, and the outermost part is a catalytic manganese dioxide microsphere. The manganese dioxide shell layer can perform the catalytic effect of NH3-SCR. Due to the porous structure of the MOF material, the specific surface area is enhanced and the catalytic efficiency can be improved.

Preferably, the MOF nanoparticles are Zr-based MOF, one or two of PCN-44 or Uio-66, most preferably Uio-66.

Preferably, tetraethyl silicate and hexadecyltrimethoxysilane are mixed in a ratio of 1:1.

Preferably, the water-soluble polymer is polyallylamine hydrochloride or polyethylene glycol, preferably polyallylamine hydrochloride is used.

The purpose of the present invention is to provide a multilayer core-shell and composite material that can be used for NH3-SCR denitration catalyst MOF as a support material and manganese dioxide as a catalyst active material.

The present invention has the following beneficial technical effects:

(1) The composite material prepared by the present invention has a large specific surface area and good low-temperature SCR denitration activity.

(2) MOF as a support material can effectively expand the contact area of manganese dioxide and form a unique three-dimensional microsphere structure.

(3) The addition of the organic silicon film can effectively increase the thickness of the manganese dioxide catalytic layer and play a better catalytic effect.

(4) The preparation process of the method is convenient. Compared with other microsphere production preparation processes, the method is simple and easy to implement, and is more conducive to mass production.

Description of the drawings

Figure 1 is an electron micrograph of an SCR denitration catalyst obtained in an embodiment of the present invention.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments.

The embodiments provided below are not used to limit the scope of the present invention, and the steps described are not used to limit the execution order. Those skilled in the art combining existing common knowledge to make obvious improvements to the present invention also fall within the protection scope of the present invention.

Example one

A preparation method of SCR denitration catalyst, the specific steps are as follows:

Step 1, 100mg terephthalic acid, 300mg zirconium tetrachloride, 2g benzoic acid and 2mL glacial acetic acid are dissolved in 100mL N,N-dimethylformamide (DMF), and the mixture is heated at 90℃ by a magnetic stirrer. Stir in a water bath for 5 hours. After that, after 3-5 centrifugal treatments and DMF washing, the rotation speed of centrifugal separation is 15000 revolutions/min, and the time is 20 min. Then, the residual solvent and impurities are removed by washing with water to obtain the corresponding MOF nanoparticles.

Step 2. Place 1g of the MOF nanoparticles obtained above in 30mL of absolute ethanol for ultrasonic dispersion for 30min, and add 0.3mL of tetraethyl silicate and 0.3mL of hexadecyl group dropwise to it under magnetic stirring. Trimethoxysilane, and continue to stir for more than 1 hour to coat the MOF nanoparticles with a layer of organic silicon film to ensure the strength of the MOF support. Thereafter, the Si-MOF material was washed with anhydrous ethanol solution several times and then dried to prepare the corresponding Si-MOF material.

Step 3. Take 1 g of the Si-MOF nanoparticles obtained above and disperse them in 500 mL of deionized water to obtain a corresponding dispersion. Add about 2g of polyallylamine hydrochloride to it, add 1g of potassium permanganate solution after it is completely dissolved, and slowly add potassium permanganate to it in a dropwise manner, keep stirring in it, and wait to be dispersed The color of the agent changes to brown, and the SCR denitration catalyst is obtained.

Example two

A preparation method of SCR denitration catalyst, the specific steps are as follows:

Step 1. Dissolve 100 mg of terephthalic acid, 300 mg of zirconium tetrachloride and 2.8 g of benzoic acid in 100 mL of N,N-dimethylformamide (DMF), and use a magnetic stirrer in a water bath at 90°C. Stir for 5h. After that, after 3-5 centrifugal treatments and DMF washing, the rotation speed of centrifugal separation is 15000 revolutions/min, and the time is 20 min. Then, the residual solvent and impurities are removed by washing with water to obtain the corresponding MOF nanoparticles.

Step 2. Place 1g of the MOF nanoparticles obtained above in 30mL of absolute ethanol for ultrasonic dispersion for 30min, and add 0.3mL of tetraethyl silicate and 0.3mL of hexadecyl group dropwise to it under magnetic stirring. Trimethoxysilane, and continue to stir for more than 1 hour to coat the MOF nanoparticles with a layer of organic silicon film to ensure the strength of the MOF support. Thereafter, the Si-MOF material was washed with anhydrous ethanol solution several times and then dried to prepare the corresponding Si-MOF material.

Step 3. Take 1 g of the Si-MOF nanoparticles obtained above and disperse them in 500 mL of deionized water to obtain a corresponding dispersion. Add about 2g of polyallylamine hydrochloride to it, add 1g of potassium permanganate solution after it is completely dissolved, and slowly add potassium permanganate to it in a dropwise manner, keep stirring in it, and wait to be dispersed The color of the agent changes to brown, and the SCR denitration catalyst is obtained.

Example three

A preparation method of SCR denitration catalyst, the specific steps are as follows:

Step 1. Dissolve an appropriate amount of 100 mg terephthalic acid, 300 mg zirconium tetrachloride and 2.8 g benzoic acid in 100 mL of N, N-dimethylformamide (DMF), and use a magnetic stirrer at 90°C. Stir in a water bath for 5 hours. After that, after 3-5 centrifugal treatments and DMF washing, the rotation speed of centrifugal separation is 12000 rpm and the time is 25 min. Then, the residual solvent and impurities are removed by washing with water to obtain the corresponding MOF nanoparticles.

Step 2. Place 1g of the MOF nanoparticles obtained above in 30mL of absolute ethanol for ultrasonic dispersion for 30min, and add 0.3mL of tetraethyl silicate and 0.3mL of hexadecyl group dropwise to it under magnetic stirring. Trimethoxysilane, and continue to stir for more than 1 hour to coat the MOF nanoparticles with a layer of organic silicon film to ensure the strength of the MOF support. Thereafter, the Si-MOF material was washed with anhydrous ethanol solution several times and then dried to prepare the corresponding Si-MOF material.

Step 3. Take 1 g of the Si-MOF nanoparticles obtained above and disperse them in 500 mL of deionized water to obtain a corresponding dispersion. Add about 2g of polyallylamine hydrochloride to it, add 1g of potassium permanganate solution after it is completely dissolved, and slowly add potassium permanganate to it in a dropwise manner, keep stirring in it, and wait to be dispersed The color of the agent changes to brown, and the SCR denitration catalyst is obtained.

Example four

A preparation method of SCR denitration catalyst, the specific steps are as follows:

Step 1. Dissolve 100 mg of terephthalic acid, 300 mg of zirconium hydroxide and 2.8 g of benzoic acid in 100 mL of N,N-dimethylformamide (DMF), and use a magnetic stirrer in a 90°C water bath Stir for 5h. After that, after 3-5 centrifugal treatments and DMF washing, the rotation speed of centrifugal separation is 15000 revolutions/min, and the time is 20 min. Then, the residual solvent and impurities are removed by washing with water to obtain the corresponding MOF nanoparticles.

Step 2. Place 1g of the MOF nanoparticles obtained above in 30mL of absolute ethanol for ultrasonic dispersion for 30min, and add 0.3mL of tetraethyl silicate and 0.3mL of hexadecyl group dropwise to it under magnetic stirring. Trimethoxysilane, and continue to stir for more than 1 hour to coat the MOF nanoparticles with a layer of organic silicon film to ensure the strength of the MOF support. Thereafter, the Si-MOF material was washed with anhydrous ethanol solution several times and then dried to prepare the corresponding Si-MOF material.

Step 3. Take 1 g of the Si-MOF nanoparticles obtained above and disperse them in 500 mL of deionized water to obtain the corresponding dispersion. Add about 2g of polyethylene glycol to it. After it is completely dissolved, add 1g of potassium permanganate solution. Potassium permanganate is slowly added to it in a dropwise manner. Continue stirring in it until the color of the dispersant changes to Brown, that is, the SCR denitration catalyst is obtained.

Example five

A preparation method of SCR denitration catalyst, the specific steps are as follows:

Step 1. Dissolve an appropriate amount of 100mg of tetra(p-carboxyphenyl)porphyrin, 300mg of zirconium hydroxide and 2.8g of benzoic acid in 100mL of N,N-dimethylformamide (DMF), and stir by magnetic force. The device was stirred in a water bath at 90°C for 7 hours. After that, after 3-5 centrifugal treatments and DMF washing, the rotation speed of centrifugal separation is 15000 revolutions/min, and the time is 20 min. Then, the residual solvent and impurities are removed by washing with water to obtain the corresponding MOF nanoparticles.

Step 2. Place 1g of the MOF nanoparticles obtained above in 30mL of absolute ethanol for ultrasonic dispersion for 30min, and add 0.3mL of tetraethyl silicate and 0.3mL of hexadecyl group dropwise to it under magnetic stirring. Trimethoxysilane, and continue to stir for more than 1 hour to coat the MOF nanoparticles with a layer of organic silicon film to ensure the strength of the MOF support. Thereafter, the Si-MOF material was washed with anhydrous ethanol solution several times and then dried to prepare the corresponding Si-MOF material.

Step 3. Take 1 g of the Si-MOF nanoparticles obtained above and disperse them in 500 mL of deionized water to obtain a corresponding dispersion. Add about 2g of polyethylene glycol to it. After it is completely dissolved, add 1g of potassium permanganate solution. Potassium permanganate is slowly added to it in a dropwise manner. Continue stirring in it until the color of the dispersant changes to Brown, that is, the SCR denitration catalyst is obtained.

Comparison

A preparation method of SCR denitration catalyst, the specific steps are as follows:

Step 1. Dissolve an appropriate amount of 100mg of tetra(p-carboxyphenyl)porphyrin, 300mg of zirconium hydroxide and 2.8g of benzoic acid in 100mL of N,N-dimethylformamide (DMF), and stir by magnetic force. The device was stirred in a water bath at 90°C for 7 hours. After that, after 3-5 centrifugal treatments and DMF washing, the rotation speed of centrifugal separation is 15000 revolutions/min, and the time is 20 min. Then, the residual solvent and impurities are removed by washing with water to obtain the corresponding MOF nanoparticles.

Step 2: Take 1 g of the MOF nanoparticles obtained above and disperse them in 500 mL of deionized water to obtain a corresponding dispersion. Add about 2g of polyethylene glycol to it. After it is completely dissolved, add 1g of potassium permanganate solution. Potassium permanganate is slowly added to it in a dropwise manner. Continue stirring in it until the color of the dispersant changes to Brown, that is, the SCR denitration catalyst is obtained.

【Test Data】

Examples 1-5 and comparative examples were used to perform selective catalytic reduction reactions on low-temperature SCR catalysts. The reaction conditions and activity results are shown in Table 1.

Catalyst performance evaluation: The activity experiment was carried out on a self-made catalyst test platform. The catalyst volume was 5ml, the ammonia-nitrogen ratio was 1:1, the O2 concentration was 6% (V/V), and GHSV (gas space velocity per hour) = 20000h-1 For flue gas, measure the NO conversion rate at 8 temperature points of 100℃, 120℃, 140℃, 160℃, 180℃, 200℃, 220℃, 240℃. When the reactor temperature stabilizes to a certain temperature point, the simulated flue gas is introduced. After 10 minutes of reaction, the NO concentration in the gas before and after the reaction is measured with a flue gas analyzer (Testo350, Germany). The continuous measurement time at each temperature point is 15min, take the average value, and calculate the NO conversion rate according to formula 1, that is, the denitration rate.

NO conversion rate=[(NOin-NOout)/NOin]×100% (Equation 1)

Table 1 Low-temperature denitration catalyst reaction test activity results NO conversion rate/%

To	100°C	120°C	140°C	160°C	180°C	200°C	220°C	240°C
Example 1	40.3	52.6	62.3	71.2	85.3	90.2	96.4	97.2
Example 2	45.4	53.1	63.3	75.8	84	88.5	95.2	96.2
Example 3	35.2	46.7	60.2	70.1	81.5	94.5	94.5	94.3
Example 4	40.1	53.2	63.1	75	84.6	93.8	96.3	96.5
Example 5	47.3	55.3	62.3	78.3	85.3	91.6	97.5	97.6
Comparison	30.2	35.5	45.2	55.6	65.3	75.2	85.2	88.5

Taking Example 2 as an implementation, the MOF-manganese dioxide microspheres obtained are shown in Figure 1. According to Figure 1, it can be clearly seen that the surface layer is a shell layer of manganese dioxide, which plays a major catalytic role. The thickness of the manganese dioxide layer is thicker than that of the MOF-manganese dioxide material without an organic silicon layer, and its catalytic effect is better. The deeper part of the interior is the MOF support material and the organic silicon layer with a larger specific surface area. From the comparison between the comparative example and Example 5, it can be concluded that the addition of the organic silicon layer can also improve the low-temperature catalytic activity.

The above are only preferred embodiments of the present invention, and do not limit the present invention in any form. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention still belong to the present invention. Within the scope of the technical solution of the invention.

Claims (7)

1. A preparation method of SCR denitration catalyst is characterized in that it specifically includes the following steps:

   (1) Weigh an appropriate amount of homemade or existing MOF nanoparticles;

   (2) Preparation of Si-MOF support: place MOF nanoparticles in absolute ethanol for ultrasonic dispersion treatment, add tetraethyl silicate and hexadecyltrimethoxysilane dropwise to it under magnetic stirring, and Continue to stir to coat the MOF nanoparticles with a layer of organic silicon film. Finally, the Si-MOF material covered with a layer of organic silicon film is washed with anhydrous ethanol and deionized water for multiple times and then dried to prepare the corresponding Si -MOF support body;

   (3) Take the Si-MOF support obtained above, disperse it in deionized water, add an appropriate amount of water-soluble polymer to it, and add potassium permanganate solution after it is completely dissolved. Potassium permanganate is added dropwise Add it in the method and stir to obtain the SCR denitration catalyst.
2. The method for preparing an SCR denitration catalyst according to claim 1, wherein the MOF nanoparticles are Zr-based MOF.
3. The method for preparing the SCR denitration catalyst according to claim 2, wherein the MOF nanoparticles are one or two of PCN-44 or Uio-66, most preferably Uio-66.
4. The method for preparing an SCR denitration catalyst according to claim 3, wherein the MOF nanoparticles are Uio-66.
5. The method for preparing the SCR denitration catalyst according to claim 1, wherein the tetraethyl silicate and hexadecyltrimethoxysilane are mixed in a ratio of 1:1.
6. The method for preparing an SCR denitration catalyst according to claim 1, wherein the water-soluble polymer is polyallylamine hydrochloride or polyethylene glycol.
7. The method for preparing an SCR denitration catalyst according to claim 1, wherein the water-soluble polymer is polyallylamine hydrochloride.

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