A manganese-based low-temperature alkali metal poisoning-resistant SCR denitrification catalyst and its preparation method

Abstract

The present invention discloses a manganese-based low-temperature alkali metal poisoning-resistant SCR denitrification catalyst and a preparation method thereof, comprising the following steps: adding methanol to a potassium permanganate aqueous solution to perform a reduction reaction to obtain birnessite-type MnO2; performing an acid treatment on the birnessite-type MnO2 to reduce H + The acid-treated birnessite catalyst is exchanged between the layers of birnessite; the obtained product is washed to neutrality and dried to obtain the acid-treated birnessite catalyst. + After poisoning, although the denitrification activity decreased, it still showed good denitrification activity, so the acid-treated birnessite catalyst can have good resistance to alkali metal poisoning.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas pollutant removal and catalyst materials, and particularly relates to a manganese-based low-temperature alkali metal poisoning-resistant SCR denitration catalyst and a preparation method thereof. Background Art

[0002] The statements herein merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] The flue gas emission temperature of biomass boilers is generally low (80-300℃), making it difficult to directly use medium and high temperature SCR catalytic process to reduce NO x Emissions are controlled. Furthermore, the high mass fraction of water-soluble alkali metals (represented by potassium (K)) in biomass fuels often leads to catalyst deactivation due to severe alkali metal poisoning. This has become a major bottleneck restricting the development of denitrification technology.

[0004] Birnessite (δ-MnO2) is a type of MnO2 with a stable layered structure consisting of MnO6 octahedral layers with shared edges. This special material contains a large number of alkali metal ions between the layers to stabilize the charge balance of the layered structure. In addition, birnessite material has a large specific surface area, and different valence states of manganese (Mn 3+ and Mn 4+ ) coexistence, active lattice oxygen, good ion exchange properties and a simple synthesis method. However, the inventors found that the existing birnessite is also easily deactivated by alkali metal poisoning. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a manganese-based low-temperature alkali metal poisoning-resistant SCR denitration catalyst and a preparation method thereof.

[0006] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing a manganese-based low-temperature alkali metal poisoning-resistant SCR denitration catalyst, comprising the following steps:

[0008] Methanol is added to the potassium permanganate aqueous solution to carry out a reduction reaction to obtain birnessite-type MnO2;

[0009] The birnessite-type MnO2 was treated with acid to convert H + exchanged to the birnessite interlayer;

[0010] The obtained product is washed to neutrality and dried to obtain an acid-treated birnessite catalyst.

[0011] In a second aspect, the present invention provides a manganese-based low-temperature alkali metal poisoning-resistant SCR denitrification catalyst prepared by the preparation method.

[0012] The beneficial effects achieved by one or more embodiments of the present invention are as follows:

[0013] Compared with the original birnessite catalyst, the denitrification activity of the acid-treated birnessite catalyst was slightly improved; K + After poisoning, the original birnessite catalyst was almost completely deactivated in the entire low temperature range (50-250℃), while the acid-treated birnessite catalyst was + After poisoning, although the denitrification activity decreased, it still showed good denitrification activity, so the acid-treated birnessite catalyst can have good resistance to alkali metal poisoning. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0015] Figure 1 The fixed-bed denitrification reaction test bench was used under the following reaction conditions: the simulated flue gas flow rate was 2000 mL / min, the percentages of NO, NH3, and O2 were 0.1%, 0.1%, and 3.0%, respectively, N2 was used as the balance gas, and the hourly velocity (GHSV) was set to 30,000 h -1 The temperature range of the catalytic reaction test is 200-500℃.

[0016] Figure 2 This is the denitration activity curve of the acid-treated birnessite catalyst prepared in Example 1;

[0017] Figure 3 In Example 1, K + Denitrification activity curve of poisoned acid-treated birnessite catalyst

[0018] Figure 4 is the denitration activity curve of the original birnessite catalyst prepared in Comparative Example 1;

[0019] Figure 5 For Comparative Example 1, K + Denitrification activity curve of poisoned original birnessite catalyst;

[0020] Figure 6 1 are the denitration activity curves of the SCR catalysts OL-1(H), K-OL-1(H), OL-1 and K-OL-1 prepared in Example 1 and Comparative Example 1;

[0021] In the figure: 1. Mass flow meter; 2. Gas premixer; 3. Flue gas preheating section; 4. Temperature controller; 5. Fixed bed quartz reactor; 6. Concentrated phosphoric acid; 7. Drying bottle; 8. Flue gas analyzer. DETAILED DESCRIPTION

[0022] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0023] In a first aspect, the present invention provides a method for preparing a manganese-based low-temperature alkali metal poisoning-resistant SCR denitration catalyst, comprising the following steps:

[0024] Methanol is added to the potassium permanganate aqueous solution to carry out a reduction reaction to obtain birnessite-type MnO2;

[0025] The birnessite-type MnO2 was treated with acid to convert H + exchanged to the birnessite interlayer;

[0026] The obtained product is washed to neutrality and dried to obtain an acid-treated birnessite catalyst.

[0027] Potassium permanganate (KMnO4) was used as an oxidant and methanol (CH3OH) as a reducing agent. Based on the preparation of birnessite-type MO2 catalyst by redox reaction, H + K in the birnessite layer + Exchange is carried out to improve the catalyst's resistance to alkali metal poisoning.

[0028] In some embodiments, in the potassium permanganate solution, the mass ratio of potassium permanganate to water is 15-20:1; the mass ratio of methanol to potassium permanganate is 1-5:1.

[0029] Preferably, the reaction time of methanol and potassium permanganate is 8-15 hours.

[0030] In some embodiments, the acid used to treat the birnessite-type MnO2 is nitric acid, and the concentration of the acid is 0.2-0.5 mol / L.

[0031] Nitric acid is chosen primarily because it can remove a large amount of nitrate ions during the filtration process. Even if nitrate ions remain on the catalyst surface, they can be decomposed and volatilized during the calcination process. However, chloride ions deposited with hydrochloric acid or sulfate ions deposited with sulfuric acid cannot be effectively removed.

[0032] Preferably, the mass ratio of birnessite-type MnO2 to acid solution is 1:15-20.

[0033] Preferably, the method for acid-treating birnessite-type MnO2 is: immersing birnessite-type MnO2 in an acid solution for 6-10 hours and stirring for 1-3 hours.

[0034] In some embodiments, the drying temperature of the acid-treated birnessite catalyst is 100-120° C., and the drying time is 12-24 hours.

[0035] In a second aspect, the present invention provides a manganese-based low-temperature alkali metal poisoning-resistant SCR denitrification catalyst prepared by the preparation method.

[0036] The present invention will be further described below with reference to the embodiments.

[0037] Example 1

[0038] Take a certain amount of potassium permanganate and deionized water in a liquid-solid ratio of 20:1 to form a turbid solution, and stir magnetically for 10 minutes. Then add a certain amount of deionized water and a certain amount of methanol (the amount of methanol added is calculated based on the mass ratio of methanol to potassium permanganate of 2.5:1) and keep stirring the mixture for 12 hours. The obtained precipitate is separated from the solid by vacuum filtration and then washed several times with deionized water until neutral. The neutral filter cake is placed in a forced air drying oven and dried at 105°C for 12 hours to constant weight. The obtained birnessite material is then ground and sieved to obtain original birnessite powder below 100 mesh.

[0039] Take a certain amount of 100-mesh original birnessite powder and mix it with 0.4 mol / L nitric acid solution at a liquid-solid ratio of 20:1, then heat it in an 80°C water bath, stir it magnetically for 3 hours, and immerse it for 7 hours. Use vacuum filtration to separate the suspension into solid and liquid, and then wash it with deionized water several times until it is neutral. Place the neutral filter cake in a blast drying oven and dry it at 105°C for 12 hours to constant weight to obtain an acid-treated birnessite catalyst, recorded as OL-1(H). Through the denitrification activity test, it can be found that the denitrification activity window of the OL-1(H) catalyst is 100-250°C, and the denitrification activity remains 100% in the temperature range of 125-225°C, such as Figure 2 shown.

[0040] Take a certain amount of potassium permanganate and deionized water in a liquid-solid ratio of 20:1 to form a turbid solution, and stir magnetically for 10 minutes. Then add a certain amount of deionized water and a certain amount of methanol (the amount of methanol added is calculated based on the mass ratio of methanol to potassium permanganate of 2.5:1) and keep stirring the mixture for 12 hours. The obtained precipitate is separated from the solid by vacuum filtration and then washed several times with deionized water until neutral. The neutral filter cake is placed in a forced air drying oven and dried at 105°C for 12 hours to constant weight. The obtained birnessite material is then ground and sieved to obtain original birnessite powder below 100 mesh.

[0041] A certain amount of 100-mesh raw birnessite powder was mixed with 0.4 mol / L nitric acid solution at a liquid-to-solid ratio of 20:1. The mixture was then heated in an 80°C water bath with magnetic stirring for 3 hours. The suspension was vacuum filtered for solid-liquid separation and then washed several times with deionized water until neutral. The neutral filter cake was dried in a forced air drying oven at 105°C for 12 hours to constant weight. The resulting acid-treated birnessite material was then ground and sieved to obtain acid-treated birnessite powder with a mesh size below 100.

[0042] Take a certain amount of acid-treated birnessite powder below 100 mesh, and add a KNO3 aqueous solution of corresponding concentration (mass fraction is 2wt%) to it. Soak for 8 hours, stir at room temperature for 2 hours, and then place the obtained sample in a blast drying oven and dry at 105°C for 12 hours to constant weight. Finally, heat from room temperature to 500°C at 5°C / min in a muffle furnace, calcine for 2 hours and then cool naturally. That is, a K-poisoned acid-treated birnessite catalyst is obtained, which is recorded as K-OL-1(H). Through the denitrification activity test, it can be found that the denitrification activity window of the K-OL-1(H) catalyst is 145-235°C, and the denitrification activity remains 100% in the temperature range of 150-210°C, such as Figure 3 shown.

[0043] Example 2

[0044] A certain amount of potassium permanganate and deionized water were mixed into a turbid solution at a liquid-solid ratio of 17:1 and magnetically stirred for 15 minutes. Then a certain amount of deionized water and a certain amount of methanol were added (the amount of methanol added was calculated based on a mass ratio of methanol to potassium permanganate of 5:1) and the mixture was stirred for 12 hours. The obtained precipitate was separated from the solid by vacuum filtration and then washed several times with deionized water until it was neutral. The neutral filter cake was placed in a forced air drying oven and dried at 105°C for 12 hours to constant weight. The obtained birnessite material was then ground and sieved to obtain the original birnessite powder below 100 mesh.

[0045] A certain amount of 100-mesh raw birnessite powder was mixed with 0.2 mol / L nitric acid solution at a liquid-to-solid ratio of 20:1. The mixture was then heated in an 80°C water bath with magnetic stirring for 3 hours and immersed for 9 hours. The suspension was vacuum filtered for solid-liquid separation and then washed several times with deionized water until neutral. The neutral filter cake was dried in a forced air drying oven at 105°C for 12 hours to constant weight, yielding the acid-treated birnessite catalyst.

[0046] Example 3

[0047] A certain amount of potassium permanganate and deionized water were mixed into a turbid solution at a liquid-solid ratio of 15:1 and magnetically stirred for 15 minutes. Then a certain amount of deionized water and a certain amount of methanol were added (the amount of methanol added was calculated based on a mass ratio of methanol to potassium permanganate of 1:1) and the mixture was stirred for 12 hours. The obtained precipitate was separated from the solid by vacuum filtration and then washed several times with deionized water until it was neutral. The neutral filter cake was placed in a forced air drying oven and dried at 105°C for 12 hours to constant weight. The obtained birnessite material was then ground and sieved to obtain the original birnessite powder below 100 mesh.

[0048] A certain amount of 100-mesh raw birnessite powder was mixed with a 0.5 mol / L nitric acid solution at a liquid-to-solid ratio of 15:1. The mixture was then heated in an 85°C water bath with magnetic stirring for 3 hours and immersed for 10 hours. The suspension was vacuum filtered for solid-liquid separation and then washed several times with deionized water until neutral. The neutral filter cake was dried in a forced air drying oven at 105°C for 12 hours to constant weight, yielding the acid-treated birnessite catalyst.

[0049] Comparative Example 1

[0050] Take a certain amount of potassium permanganate and deionized water and configure them into a turbid liquid at a liquid-solid ratio of 20:1, and stir magnetically for 10 minutes. Then add a certain amount of deionized water and a certain amount of methanol (the amount of methanol added is calculated based on the mass ratio of methanol to potassium permanganate of 2.5:1) and stir the mixture for 12 hours. The obtained precipitate is separated from the solid by vacuum filtration and then washed several times with deionized water until it is neutral. The neutral filter cake is placed in a blast drying oven and dried at 105°C for 12 hours to constant weight to obtain a birnessite catalyst, recorded as OL-1. Through the denitrification activity test, it can be found that the denitrification activity window of the OL-1 catalyst is 120-210°C. At 200°C, the denitrification activity reaches 100%, such as Figure 4 shown.

[0051] Take a certain amount of potassium permanganate and deionized water in a liquid-solid ratio of 20:1 to form a turbid solution, and stir magnetically for 10 minutes. Then add a certain amount of deionized water and a certain amount of methanol (the amount of methanol added is calculated based on the mass ratio of methanol to potassium permanganate of 2.5:1) and keep stirring the mixture for 12 hours. The obtained precipitate is separated from the solid by vacuum filtration and then washed several times with deionized water until neutral. The neutral filter cake is placed in a forced air drying oven and dried at 105°C for 12 hours to constant weight. The obtained birnessite material is then ground and sieved to obtain original birnessite powder below 100 mesh.

[0052] Take a certain amount of original birnessite powder below 100 mesh, and add a KNO3 aqueous solution of corresponding concentration (mass fraction is 2wt%) to it. Soak for 8 hours, stir at room temperature for 2 hours, and then place the obtained sample in a blast drying oven and dry at 105°C for 12 hours to constant weight. Finally, heat from room temperature to 500°C at 5°C / min in a muffle furnace, calcine for 2 hours and then cool naturally. The K-poisoned birnessite catalyst is obtained, which is recorded as K-OL-1. Through the denitrification activity test, it can be found that the denitrification activity of the K-OL-1 catalyst in the full low-temperature range of 50-250°C is only up to 10%, that is, the K-OL-1 catalyst is in a completely deactivated state, such as Figure 5 shown.

[0053] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing a manganese-based low-temperature alkali metal poisoning-resistant SCR denitration catalyst, characterized by: The steps include: Methanol is added to the potassium permanganate aqueous solution to carry out a reduction reaction to obtain birnessite-type MnO2; The birnessite-type MnO2 was treated with acid to convert H + exchanged to the birnessite interlayer; The obtained product is washed to neutrality and dried to obtain an acid-treated birnessite catalyst; In the potassium permanganate solution, the mass ratio of potassium permanganate to water is 15-20:1; the mass ratio of methanol to potassium permanganate is 1-5:1; The acid used for the acid treatment of birnessite-type MnO2 is nitric acid, and the concentration of nitric acid is 0.2-0.5 mol / L; The method for acid-treating birnessite-type MnO2 is as follows: immersing birnessite-type MnO2 in an acid solution for 6-10 hours and stirring for 1-3 hours; The temperature for impregnation of birnessite-type MnO2 in acid solution is 75-90℃; The mass ratio of birnessite-type MnO2 to acid solution is 1:15-20.

2. The method for preparing a manganese-based low-temperature alkali metal poisoning-resistant SCR denitration catalyst according to claim 1, characterized in that: The reaction time of methanol and potassium permanganate is 8-15h.

3. The method for preparing a manganese-based low-temperature alkali metal poisoning-resistant SCR denitration catalyst according to claim 1, characterized in that: The drying temperature of the acid-treated birnessite catalyst is 100-120° C., and the drying time is 12-24 hours.

4. The method for preparing a manganese-based low-temperature alkali metal poisoning-resistant SCR denitration catalyst according to claim 3, characterized in that: The drying temperature of the acid-treated birnessite catalyst is 100-110° C., and the drying time is 15-20 hours.

5. A manganese-based low-temperature alkali metal poisoning-resistant SCR denitrification catalyst, characterized by: Prepared by the preparation method according to any one of claims 1 to 4.

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