A modified carbon-based catalyst for NH3-SCR denitrification and its preparation method

Abstract

This invention relates to the field of carbon-based modification technology, and discloses a modified carbon-based catalyst for NH3-SCR denitrification and its preparation method. By mass percentage, the modified carbon-based catalyst comprises 55-75% carbon-based raw materials, 5-15% organic acids, and 15-30% nitrogen-containing compounds. This invention improves the low-temperature (105-155℃) NH3 selective catalytic reduction (NH3-SCR) denitrification activity of carbon-based catalysts by introducing organic acids and nitrogen-containing compounds to modify the carbon-based catalyst, thereby increasing the content of nitrogen and oxygen functional groups on the surface of the carbon-based material. It also avoids the traditional method of oxidative modification of carbon-based catalysts by directly loading organic acids and nitrogen-containing compound precursors to enhance the low-temperature denitrification activity of the carbon-based catalyst. The modified carbon-based catalyst of this invention can achieve a denitrification efficiency of 97% under high space velocities, and the modification preparation process is simple and easy for industrial processing and production.

Description

Technical Field

[0001] This invention relates to the field of carbon-based catalysts, specifically to modified carbon-based catalysts and their preparation methods, particularly a method for preparing a modified carbon-based catalyst for NH3-SCR denitrification. Background Technology

[0002] Nitrogen oxides (NO) x NOx, primarily produced from the combustion of fossil fuels, is severely destructive to human health and the environment, leading to a series of environmental pollutants such as acid rain and photochemical smog. It seriously damages human health and the natural environment. Therefore, developing highly efficient NOx emission control technologies is crucial. x Removal technology is of great significance for improving the atmospheric environment.

[0003] Currently, NO x Control measures primarily focus on post-combustion treatment. Currently, the mainstream industrial denitrification methods are selective non-catalytic reduction (SNCR) and selective catalytic reduction (SCR). SNCR involves high reaction temperatures, generally above 1000℃; while SCR uses NH3 as a reducing agent and a denitrification catalyst to remove NO. x When combined with NH3, it is reduced to N2, and its denitrification efficiency can generally reach over 85%. The core of SCR is the catalyst, and VWTi, as the current mainstream SCR catalyst, exhibits good denitrification activity and selectivity at 300–400℃. However, although SCR technology has been widely used for medium-temperature flue gas denitrification in coal-fired power plants, its activation temperature is still relatively high (300–400℃), making it difficult to meet the denitrification requirements of low-temperature flue gas (below 160℃) generated in non-power industries. Furthermore, V species are biotoxic, posing a threat to the environment and organisms. Therefore, developing a highly efficient and green SCR catalyst for low-temperature flue gas is of great significance.

[0004] Carbon-based catalysts have attracted much attention as low-temperature SCR catalysts. Although they have been applied in fields such as low-temperature flue gas denitrification in steel sintering machines, they still suffer from problems such as large usage (i.e., low space velocity) and low denitrification activity, which urgently need to be addressed. Currently, the development of carbon-based low-temperature SCR catalysts mainly focuses on loading active metals onto the surface of activated carbon or changing the distribution of active components on the activated carbon surface. Existing activated carbon denitrification catalyst patents, such as CN111704132B and CN115155608A, utilize the modification of activated carbon by loading metal active sites, which is an effective means to improve the conversion efficiency of activated carbon for sulfides and nitrogen oxides. However, the metals loaded on activated carbon are mostly metal oxides, making the carbon-based materials easily oxidized by metal oxides. Furthermore, metal oxidation is easily poisoned by flue gas components, and the catalytic activity is often below 85%, still failing to meet the needs of industrial applications and increasingly stringent environmental protection requirements. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by using SCR technology with NH3 as a reducing agent and carbon-based catalysts as the research basis, and to provide a method for preparing a modified carbon-based catalyst for low-temperature flue gas denitrification that does not require metal loading and has strong industrial application value.

[0006] A modified carbon-based catalyst for NH3-SCR denitrification comprises, by mass percentage, 55-75% carbon-based feedstock, 5-15% organic acid precursor, and 15-30% nitrogen-containing compound precursor. Under the above formulation, the modified carbon-based catalyst can be prepared by the following three methods:

[0007] The preparation method of modified carbon-based catalysts involves the following steps:

[0008] (1) A certain amount of organic acid is loaded onto the surface of a carbon-based material by impregnation loading. After the loaded carbon-based material is dried and dehydrated, modified carbon-based material I is obtained.

[0009] (2) The modified carbon-based material I and the nitrogen-containing compound powder are thoroughly mixed to obtain the modified carbon-based material II;

[0010] (3) The modified carbon-based material II was heat-treated for 2 to 5 hours under the protection of an inert gas at a temperature of 550 to 700 °C to obtain the modified carbon-based catalyst.

[0011] The two-step method for preparing modified carbon-based catalysts is as follows:

[0012] (1) Organic acids and nitrogen-containing compounds are simultaneously loaded onto carbon-based raw materials by impregnation loading. After the loaded carbon-based material is dried and dehydrated, carbon-based material II is obtained.

[0013] (2) The modified carbon-based material II was heat-treated under inert gas protection for 2-5 hours at a temperature of 550-700℃.

[0014] A modified carbon-based catalyst was obtained.

[0015] The three steps for preparing modified carbon-based catalysts are as follows:

[0016] (1) The carbon-based material and the nitrogen-containing compound are thoroughly mixed in powder form to obtain modified carbon-based material III;

[0017] (2) A certain amount of organic acid was loaded onto the modified carbon-based material III by impregnation loading. After the loaded carbon-based material was dried and dehydrated, the modified carbon-based material IV was obtained.

[0018] (3) The modified carbon-based material IV was heat-treated under inert gas protection for 2–5 hours at a temperature of 550–700℃.

[0019] A modified carbon-based catalyst was obtained.

[0020] This invention utilizes organic acids loaded onto a carbon-based surface to generate a large number of oxygen-containing functional groups. Then, nitrogen-containing functional groups are pyrolyzed at high temperatures to generate a large number of nitrogen-containing functional groups on the catalyst surface. This significantly increases the active functional groups on the catalyst surface with minimal impact on the catalyst structure, promoting the catalytic conversion of NO to an active intermediate and enhancing the adsorption and activation capacity of NH3, thereby improving the SCR denitrification activity. Simultaneously, because the catalyst provided by this invention promotes the catalytic oxidation of NO (i.e., the ability to catalytically convert it to a denitrification active intermediate), the adsorbed and activated NH3 can react with NO in the gas phase (Eley-Rideal mechanism) and also react with NO and NO2 adsorbed on the surface (Langmuir-Hinshelwood mechanism). Both pathways can reduce NO to N2, thereby enhancing denitrification activity and reducing NO levels. x Emissions.

[0021] The significant advantages of this invention compared with the prior art are: (1) The modified carbon-based catalyst provided by this invention, while maintaining the existing advantages of carbon-based catalysts in denitration industrial applications, significantly improves the space velocity (120℃, 9000h) while achieving a denitration efficiency of over 90%. -1 Under the specified conditions, the catalytic activity can reach 97% at 155℃ for 9000 hours. -1 (1) Under certain conditions, the catalytic activity can reach 99%, making it more suitable for industrial applications; (2) By loading nitrogen-containing and oxygen-containing functional groups onto the catalyst surface using inexpensive organic acids and nitrogen-containing compounds (melamine, cyanuric acid, dicyandiamine, urea), the low-temperature SCR catalytic activity is significantly improved, and it has a significant price advantage compared to metal catalysts. Compared with activated carbon catalysts with strong oxidizing properties such as manganese and cerium as active components, the modified activated carbon catalyst of this invention has extremely high selectivity, with a catalytic selectivity of up to 98.7% at 120℃. (3) Experimental studies have shown that after loading nitrogen-containing and oxygen-containing functional groups onto the surface of activated carbon, the low-temperature catalytic activity of activated carbon is greatly improved, such as at NO concentration of 550ppm, NH3 / NO=1, O2 10 v%, 120℃, 9000h -1 Under the specified conditions, the NO removal rate of the modified carbon-based catalyst prepared by this invention far exceeds that of the unmodified carbon-based catalyst, reaching 97%. At 155℃, the NO removal rate of the modified activated carbon catalyst prepared by this invention reaches 99%, which has strong industrial application value and can be widely used for the removal of nitrogen oxides in low-temperature flue gas. Detailed Implementation

[0022] The endpoints of the ranges reported in this invention and any numerical values ​​are not limited to those precise ranges or values; such ranges or values ​​should be understood to include values ​​close to them. All numerical ranges can be combined with each other to obtain one or more new numerical ranges, which should be considered as specific disclosures herein.

[0023] The present invention will be further described in detail below with reference to the embodiments.

[0024] Example 1

[0025] Taking the preparation of the product of this invention as an example, the components and their mass ratios used in 100g of raw materials are as follows:

[0026]

[0027] (1) First, put activated coke and oxalic acid into 1000ml of water, heat and stir at 80℃ until the water evaporates, and then dry the obtained activated coke solid at 120℃ for 12h to remove water, and then obtain modified carbon-based material I.

[0028] (2) The modified carbon-based material I is thoroughly mixed with melamine powder to obtain the modified carbon-based material II;

[0029] (3) The modified carbon-based material II was calcined at 600℃ under nitrogen protection for 2h to obtain the modified active coke catalyst.

[0030] Example 2

[0031] Taking the preparation of the product of this invention as an example, the components and their mass ratios used in 100g of raw materials are as follows:

[0032]

[0033] (1) First, put activated coke and oxalic acid into 1000ml of water, heat and stir at 80℃ until the water evaporates, and then dry the obtained activated coke solid at 120℃ for 12h to further remove water, and then obtain modified carbon-based material I.

[0034] (2) The modified carbon-based material I is thoroughly mixed with melamine powder to obtain the modified carbon-based material II;

[0035] (3) The modified carbon-based material II was calcined at 700°C under nitrogen protection for 2 hours to obtain the modified active coke catalyst.

[0036] Example 3

[0037] Taking the preparation of the product of this invention as an example, the components and their mass ratios used in 100g of raw materials are as follows:

[0038]

[0039] (1) First, put activated coke and oxalic acid into 1000ml of water, heat and stir at 80℃ until the water evaporates, and then dry the obtained activated coke solid at 120℃ for 12h to further remove water, and then obtain modified carbon-based material I.

[0040] (2) The modified carbon-based material I is thoroughly mixed with melamine powder to obtain the modified carbon-based material II;

[0041] (3) The modified carbon-based material II was calcined at 550°C under nitrogen protection for 2 hours to obtain the modified active coke catalyst.

[0042] Example 4

[0043] Taking the preparation of the product of this invention as an example, the components and their mass ratios used in 100g of raw materials are as follows:

[0044]

[0045] (1) First, put activated coke and oxalic acid into 1000ml of water, heat and stir at 80℃ until the water evaporates, and then dry the obtained activated coke solid at 120℃ for 12h to further remove water, and then obtain modified carbon-based material I.

[0046] (2) The modified carbon-based material I is thoroughly mixed with melamine powder to obtain the modified carbon-based material II;

[0047] (3) The modified carbon-based material II was calcined at 600℃ under nitrogen protection for 5h to obtain the modified active coke catalyst.

[0048] Example 5

[0049] Taking the preparation of the product of this invention as an example, the components and their mass ratios used in 100g of raw materials are as follows:

[0050]

[0051] (1) First, put activated coke and oxalic acid into 1000ml of water, heat and stir at 80℃ until the water evaporates, and then dry the obtained activated coke solid at 120℃ for 12h to further remove water, and then obtain modified carbon-based material I.

[0052] (2) The modified carbon-based material I is thoroughly mixed with dicyandiamine powder to obtain the modified carbon-based material II;

[0053] (3) The modified carbon-based material II was calcined at 600℃ under nitrogen protection for 2h to obtain the modified active coke catalyst.

[0054] Example 6

[0055] Taking the preparation of the product of this invention as an example, the components and their mass ratios used in 100g of raw materials are as follows:

[0056]

[0057] (1) First, put activated coke and citric acid into 1000ml of water, heat and stir at 80℃ until the water evaporates, and then dry the obtained activated coke solid at 120℃ for 12h to further remove water, and then obtain modified carbon-based material I.

[0058] (2) The modified carbon-based material I is thoroughly mixed with melamine powder to obtain the modified carbon-based material II;

[0059] (3) The modified carbon-based material II was calcined at 600℃ under nitrogen protection for 3h to obtain the modified active coke catalyst.

[0060] Example 7

[0061] Taking the preparation of the product of this invention as an example, the components and their mass ratios used in 100g of raw materials are as follows:

[0062]

[0063] (1) First, put activated coke, oxalic acid and citric acid into 1000ml of water, heat and stir at 80℃ until the water evaporates, and then dry the obtained activated coke solid at 120℃ for 12h to further remove water, and then obtain modified carbon-based material I.

[0064] (2) The modified carbon-based material I is thoroughly mixed with melamine powder to obtain the modified carbon-based material II;

[0065] (3) The modified carbon-based material II was calcined at 600℃ under nitrogen protection for 2h to obtain the modified active coke catalyst.

[0066] Example 8

[0067] Taking the preparation of the product of this invention as an example, the components and their mass ratios used in 100g of raw materials are as follows:

[0068]

[0069] (1) First, put activated coke and oxalic acid into 1000ml of water, heat and stir at 80℃ until the water evaporates, and then dry the obtained activated coke solid at 120℃ for 12h to further remove water, and then obtain modified carbon-based material I.

[0070] (2) The dried activated coke solids are thoroughly mixed with melamine and dicyandiamine powder to obtain modified carbon-based material II;

[0071] (3) The modified carbon-based material II was calcined at 600℃ under nitrogen protection for 2h to obtain the modified active coke catalyst.

[0072] Example 9

[0073] Taking the preparation of the product of this invention as an example, the components and their mass ratios used in 100g of raw materials are as follows:

[0074]

[0075] (1) First, put activated coke and oxalic acid into 1000ml of water, heat and stir at 80℃ until the water evaporates, and then dry the obtained activated coke solid at 120℃ for 12h to further remove water, and then obtain modified carbon-based material I.

[0076] (2) The dried activated coke solids are thoroughly mixed with cyanuric acid powder to obtain modified carbon-based material II;

[0077] (3) The modified carbon-based material II was calcined at 600℃ under nitrogen protection for 2h to obtain the modified active coke catalyst.

[0078] Example 10

[0079] Taking the preparation of the product of this invention as an example, the components and their mass ratios used in 100g of raw materials are as follows:

[0080]

[0081] (1) First, put activated coke and oxalic acid into 1000ml of water, heat and stir at 80℃ until the water evaporates, and then dry the obtained activated coke solid at 120℃ for 12h to further remove water, and then obtain modified carbon-based material I.

[0082] (2) Mix modified carbon-based material I with urea powder thoroughly to obtain modified carbon-based material II;

[0083] (3) The modified carbon-based material II was calcined at 600℃ under nitrogen protection for 2h to obtain the modified active coke catalyst.

[0084] Example 11

[0085] Taking the preparation of 100g of the product of this invention as an example, the components and their mass ratios of the raw materials are as follows:

[0086]

[0087] (1) First, put activated coke and oxalic acid into 1000ml of water, heat and stir at 80℃ until the water evaporates, and then dry the obtained activated coke solid at 120℃ for 12h to further remove water, and then obtain modified carbon-based material I.

[0088] (2) The modified carbon-based material I is thoroughly mixed with dicyandiamine powder to obtain the modified carbon-based material II;

[0089] (3) The modified carbon-based material II was calcined at 600℃ under nitrogen protection for 2 hours to obtain the modified activated carbon catalyst.

[0090] Example 12

[0091] Taking the preparation of 100g of the product of this invention as an example, the components and their mass ratios of the raw materials are as follows:

[0092]

[0093] (1) First, put activated carbon, oxalic acid and dicyandiamine into 1000ml of water, heat and stir at 80°C until the water evaporates, and then dry the carbon-based solid at 120°C for 12h to further remove water, and then directly obtain modified carbon-based material II.

[0094] (2) The modified carbon-based material II was calcined at 600℃ under nitrogen protection for 2 hours to obtain the modified carbon-based catalyst.

[0095] Example 13

[0096] Taking the preparation of 100g of the product of this invention as an example, the components and their mass ratios of the raw materials are as follows:

[0097]

[0098] (1) First, activated carbon, oxalic acid and dicyandiamine are placed in 1000ml of water and heated and stirred at 80°C until the water is evaporated. The resulting carbon-based solid is dried at 120°C for 12h to further remove water, and then modified carbon-based material II is obtained directly.

[0099] (2) The modified carbon-based material II was calcined at 600℃ under nitrogen protection for 2 hours to obtain the modified activated carbon catalyst.

[0100] Example 14

[0101] Taking the preparation of 100g of the product of this invention as an example, the components and their mass ratios of the raw materials are as follows:

[0102]

[0103] (1) First, put the active semi-coke, oxalic acid and dicyandiamine into 1000ml of water, heat and stir at 80°C until the water evaporates, and then dry the carbon-based solid at 120°C for 12h to further remove water, and then obtain modified carbon-based material II.

[0104] (2) The modified carbon-based material II was calcined at 600℃ under nitrogen protection for 2 hours to obtain the modified carbon-based catalyst.

[0105] Example 15

[0106] Taking the preparation of 100g of the product of this invention as an example, the components and their mass ratios of the raw materials are as follows:

[0107]

[0108] (1) The carbon-based material and dicyandiamine were thoroughly mixed to obtain modified carbon-based material III;

[0109] (2) Oxalic acid was loaded onto modified carbon-based material III by impregnation loading. Oxalic acid and modified carbon-based material were placed in 1000 ml of water and heated and stirred at 80°C until the water was evaporated. The resulting carbon-based solid was dried at 120°C for 12 h to further remove water, and then modified carbon-based material IV was obtained.

[0110] (3) The modified carbon-based material IV was calcined at 600℃ under nitrogen protection for 2 hours to obtain the modified carbon-based catalyst.

[0111] Example 16

[0112] Taking the preparation of 100g of the product of this invention as an example, the components and their mass ratios of the raw materials are as follows:

[0113]

[0114] (1) First, put activated carbon, oxalic acid and dicyandiamine into 1000ml of water, heat and stir at 80°C until the water evaporates, and then dry the carbon-based solid at 120°C for 12h to further remove water, and then obtain modified carbon-based material II.

[0115] (2) The modified carbon-based material II was calcined at 600℃ under argon protection for 2h to obtain the modified carbon-based catalyst.

[0116] Example 17

[0117] Taking the preparation of 100g of the product of this invention as an example, the components and their mass ratios of the raw materials are as follows:

[0118]

[0119] (1) First, put activated coke and oxalic acid into 1000ml of water, heat and stir at 80℃ until the water evaporates, and then dry the obtained activated coke solid at 120℃ for 12h to further remove water, and then obtain modified carbon-based material I.

[0120] (2) The modified carbon-based material I and dicyandiamine powder were placed in 1000 ml of water and heated at 80°C with stirring until the water was evaporated to dryness, thus obtaining the modified carbon-based material II.

[0121] (3) The modified carbon-based material II was calcined at 600℃ under nitrogen protection for 2 hours to obtain the modified activated carbon catalyst.

[0122] Example 18

[0123] Taking the preparation of 100g of the product of this invention as an example, the components and their mass ratios of the raw materials are as follows:

[0124]

[0125] (1) The carbon-based material and dicyandiamine powder were placed in 1000 ml of water and heated and stirred at 80°C until the water was evaporated and the water was removed, thus obtaining modified carbon-based material III.

[0126] (2) Oxalic acid was loaded onto modified carbon-based material III by impregnation loading. Oxalic acid and modified carbon-based material were placed in 1000 ml of water and heated and stirred at 80°C until the water was evaporated. The resulting carbon-based solid was dried at 120°C for 12 h. After further dehydration, modified carbon-based material IV was obtained.

[0127] (3) The modified carbon-based material IV was calcined at 600℃ under nitrogen protection for 2 hours to obtain the modified carbon-based catalyst.

[0128] Comparative Example 1

[0129] The modified activated coke catalyst comparative example was prepared according to the formulation in Example 1, and the melamine powder component was removed.

[0130] (1) First, put the activated char and oxalic acid into 1000ml of water, heat and stir at 80℃ until the water evaporates, and then dry the obtained activated char solid at 120℃ for 12h.

[0131] (2) The dried activated coke was calcined at 600℃ under nitrogen protection for 2 hours to obtain the activated coke catalyst.

[0132] Comparative Example 2

[0133] The modified activated coke catalyst comparative example, according to the formulation in Example 1, removes oxalic acid and water.

[0134] (1) Thoroughly mix the activated coke solids with melamine powder;

[0135] (2) The obtained carbon-based solid was calcined at 600℃ under nitrogen protection for 2h to obtain an active coke catalyst.

[0136] Comparative Example 3

[0137] The modified activated coke catalyst comparative example was prepared according to the formulation in Example 1. The calcination temperature was adjusted to 400°C to obtain the activated coke catalyst.

[0138] Comparative Example 4

[0139] The activated coke feedstock is used as a carbon-based catalyst without any modification.

[0140] Comparative Example 5

[0141] Comparative examples of modified activated coke catalysts.

[0142] Taking the preparation of activated carbon products as an example, the components and their mass ratios used in 100g of raw materials are as follows:

[0143] Activated coke 80g;

[0144] 20g of dicyandiamine;

[0145] 1000 ml of 1M ammonium persulfate solution;

[0146] (1) First, put the activated carbon into 1000ml of 1M ammonium persulfate solution and stir at room temperature for 12h. Then filter and wash the activated carbon until pH=7. The obtained activated carbon solid is dried at 120℃ for 12h.

[0147] (2) The dried activated coke and dicyandiamine powder were thoroughly mixed and calcined at 600°C under nitrogen protection for 2 hours to obtain the activated coke catalyst.

[0148] Table 1 shows the main components and denitrification activities of the modified carbon-based catalysts in each example and comparative example. Denitrification activity refers to the NO conversion rate of flue gas after passing through the modified carbon-based catalyst using NH3 as a reducing agent, i.e., denitrification activity = (inlet NO concentration - outlet NO concentration) / inlet NO concentration.

[0149] Table 1. Main components and denitrification activity of the modified carbon-based catalyst. h represents hours; ℃ represents temperature; h -1 airspeed

[0150]

[0151]

[0152] As shown in Table 1, the denitrification activity of the modified activated coke catalysts obtained by modification with organic acids and nitrogen-containing compounds in Examples 1-16 of this invention is significantly better than that of the pure activated coke catalyst in Comparative Example 4. The effective components of the modified carbon-based catalyst are, by mass percentage, 55-75% carbon-based raw materials, 5-15% organic acid precursors, and 15-30% nitrogen-containing compound precursors. Among them, the organic acid precursors can be oxalic acid or citric acid, and the nitrogen compound precursors can be melamine, dicyandiamide, cyanuric acid, or urea.

[0153] Compared with Examples 1-16, no nitrogen-containing compounds were added to the formulations of Comparative Examples 1 and 4, resulting in a significant decrease in the denitrification activity of Comparative Examples 1 and 4 compared to Examples 1-16. This also indicates that the addition of nitrogen-containing compounds to carbon-based catalysts is necessary to improve denitrification activity.

[0154] Compared with Examples 1-16, no organic acid was added to the formulations of Comparative Examples 2 and 4, which resulted in a significant decrease in the denitrification activity of Comparative Examples 2 and 4 compared with Examples 1-16. This also shows that the addition of organic acid to carbon-based catalysts is necessary to improve the denitrification activity.

[0155] Examples 1-16 show modified carbon-based catalysts with added nitrogen-containing compounds and organic acids. Compared to carbon-based catalysts with added nitrogen-containing compounds or organic acids alone in Comparative Examples 1 and 2, the former exhibit significantly higher denitrification activities than the latter catalysts with added nitrogen-containing compounds or organic acids alone. For instance, the combined denitrification activities of Comparative Examples 1 and 2 are only 47%, while the lowest denitrification activities of Comparative Examples 1-13 all reach 61%. This indicates that the co-addition of nitrogen-containing compounds and organic acids has a synergistic coupling effect on the denitrification activity of modified carbon-based catalysts.

[0156] Among the denitrification activities of Examples 1, 2 and 3, the denitrification activity of Example 2 is relatively low. Therefore, when the calcination temperature reaches 700℃, the denitrification activity of the modified carbon-based catalyst will decrease.

[0157] Examples 11, 12, and 15 all exhibited high denitrification activity. The difference between these three examples lies in the order in which organic acids and nitrogen-containing compounds were added. Therefore, it is demonstrated that modified carbon-based catalysts prepared by adding organic acids and nitrogen-containing compounds in a specific order or together to carbon-based materials all possess high denitrification activity.

[0158] Examples 12, 13, and 14 all exhibit high denitrification activity. The difference between these three examples lies in the different carbon-based materials in the catalysts. Therefore, for modified carbon-based catalysts, the carbon-based material can be activated carbon, activated coke, or activated semi-coke.

[0159] Example 16 uses argon to calcine a carbon-based solid to obtain a modified carbon-based catalyst. Its denitrification activity is consistent with that of the modified carbon-based catalyst obtained by nitrogen calcination under the same formulation in Example 11. This shows that the denitrification effect of the modified carbon-based catalyst is not affected by using different inert gases for calcination, that is, by using gases that do not react with carbon-based materials.

[0160] Examples 11, 13, and 15 all exhibited high denitrification activity. The difference between these three examples lies in the method of adding nitrogen-containing compounds, which differs from that in Examples 11 and 15. Therefore, it can be concluded that the mixing of nitrogen-containing compounds involved in the preparation of modified carbon-based material II or modified carbon-based material III can be either pure solid-phase mixing or impregnation loading.

[0161] Example 11 shows higher denitrification activity than Examples 12, 13, 14, 15, 16, 17, and 18. The difference is that Example 11 uses a solid-state mixing method instead of an impregnation method to support nitrogen-containing compounds. Therefore, the modified carbon-based catalyst prepared by using the solid-state mixing method to support nitrogen-containing compounds has relatively higher denitrification activity. Examples 11, 15, 17, and 18 all exhibited high denitrification activity. The difference between these four examples lies in the method of adding nitrogen-containing compounds, which differs between Examples 11 and 15 and Examples 17 and 18. Therefore, it can be concluded that the mixing of nitrogen-containing compounds involved in the preparation of modified carbon-based material II or modified carbon-based material III can be either pure solid-phase mixing or impregnation loading.

[0162] The denitrification activity results of Examples 11, 12, 13, and 15 show that the modified carbon-based catalyst of the present invention has a denitrification activity of >90% at 105–155 °C, indicating good denitrification activity.

[0163] The denitrification activity of Comparative Example 4 shows that when the unmodified carbon-based catalyst (pure activated coke) has a reaction space velocity of 9000 h⁻¹ -1 At that time, the denitrification activity was only 10%, and after reducing the reaction space velocity, the denitrification activity only increased to 17%; while in Examples 11, 12, 13, and 15, after 9000 h... -1 and 4500h -1 The modified carbon-based catalyst of this invention exhibits high denitrification activity at high space velocities (up to 9000 h⁻¹). -1 It exhibits good denitrification activity at air velocity (at a certain air velocity).

[0164] In Comparative Example 5, the organic acid loading method was replaced by an oxidative modification method, and the denitrification activity was significantly reduced compared to Example 11 under the same test conditions.

Claims

1. A method for preparing a modified carbon-based catalyst for NH3-SCR denitrification, characterized in that, The preparation steps are as follows: (1) The carbon-based raw materials and nitrogen-containing compound powder are thoroughly mixed. The mixing is a pure solid phase mixing. The nitrogen-containing compound accounts for 15-30% of the total modified carbon-based catalyst raw materials to obtain modified carbon-based material III. (2) A certain amount of organic acid is loaded onto the modified carbon-based material III by impregnation loading. The proportion of organic acid to the total modified carbon-based catalyst raw material is 5-15%. After the loaded carbon-based material is dried and dehydrated, the modified carbon-based material IV is obtained. (3) The modified carbon-based material IV was heat-treated under the protection of an inert gas for 2-5 h at a temperature of 550-700 °C to obtain the modified carbon-based catalyst.

2. The preparation method according to claim 1, characterized in that, The organic acid precursor is oxalic acid or citric acid.

3. The preparation method according to claim 1, characterized in that, The nitrogen-containing compound is melamine, dicyandiamine, cyanuric acid, or urea.

4. The preparation method according to claim 1, characterized in that, The carbon-based raw material is activated carbon, activated coke, or activated semi-coke.

5. The preparation method according to claim 1, characterized in that, The inert gas refers to a gas that does not react with carbon-based materials at high temperatures.

6. The preparation method according to claim 5, characterized in that, The inert gas is nitrogen or argon.

7. The application of the modified carbon-based catalyst prepared by any one of claims 1 to 6, characterized in that, It can be used for flue gas denitrification at medium and low temperatures of 105~155 °C, while modified carbon-based catalysts are used at high space velocities.

8. The application according to claim 7, characterized in that, High airspeed is 9000 h -1 .

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