A method to improve the water and sulfur resistance of low-temperature denitrification catalysts

Abstract

This invention discloses a method for improving the water and sulfur resistance of low-temperature denitrification catalysts, comprising the following steps: modifying the micropores of a hierarchical activated coke with nitrogen-containing functional groups; and loading the low-temperature denitrification catalyst into the meso- and macropores of the hierarchical activated coke to obtain a supported catalyst. This invention, by loading the low-temperature denitrification catalyst into the hierarchical activated coke, directly utilizes the NO2 generated during the reaction to decompose ammonium bisulfate in situ, without affecting the continuous and stable operation of the reaction. It eliminates the need for an additional heating and regeneration device, reducing equipment complexity and energy consumption.

Description

Technical Field

[0001] This invention relates to the field of low-temperature denitrification catalyst technology, and in particular to a method for improving the water and sulfur resistance of low-temperature denitrification catalysts. Background Technology

[0002] Nitrogen oxides (NOx) emitted from anthropogenic sources x NO3 is a major contributing factor to environmental problems such as acid rain, photochemical smog, and stratospheric ozone depletion, and its efficient removal has always been a key concern in the energy and environmental fields. NH3-SCR based on vanadium-tungsten-titanium catalysts is currently the most effective method for controlling NO3 in coal-fired power plants and mobile sources. x While NO is the mainstream technology, with the ongoing ultra-low emission retrofitting of coal-fired power plants, NO... x The main emitters of NO have gradually shifted from the thermal power industry to non-power industries such as industrial boilers (kilns), steel, and coking, making NO... x High-efficiency removal faces new challenges. Compared to the thermal power industry, the flue gas temperature in non-power industries is lower, generally not exceeding 280℃. SO2 and H2O in the flue gas easily interact with NH3 during the NH3-SCR reaction to form ammonium bisulfate. Ammonium bisulfate is difficult to remove due to its hygroscopic, corrosive, and sticky properties, causing damage to the catalytic bed and air preheater, and consequently affecting the stable operation of the NH3-SCR system.

[0003] Currently, catalyst regeneration is mainly achieved by installing dedicated heating devices. These include connecting a built-in direct-fired furnace to the flue gas duct to heat the flue gas and gasify the ammonium bisulfate on the catalyst surface, or installing a regeneration module including a fan and a heater alongside one side of the SCR denitrification tower. The heated regenerated flue gas then decomposes the ammonium bisulfate adhering to the catalyst. Both of these technologies require the introduction of heating and regeneration devices into existing NH3-SCR denitrification systems, increasing system complexity and energy consumption due to the externally introduced fans and heaters. Summary of the Invention

[0004] The present invention aims to at least partially solve one of the technical problems in the related art.

[0005] Therefore, embodiments of the present invention propose a method to improve the water and sulfur resistance of low-temperature denitrification catalysts.

[0006] This invention proposes a method to improve the water and sulfur resistance of low-temperature denitrification catalysts, comprising the following steps:

[0007] (a) Modifying the micropores of hierarchical activated carbon using nitrogen-containing functional groups;

[0008] (b) The low-temperature denitrification catalyst is loaded into the mesopores of the graded activated coke to obtain a supported catalyst.

[0009] In some embodiments, step (a) specifically involves thermally annealing the graded porous activated coke with a mixture of NH3 and N2 to modify the microporous structure of the graded porous activated coke, wherein the nitrogen content in the graded porous activated coke modified with nitrogen-containing functional groups is not less than 2.5 at%.

[0010] In some embodiments, the micropores of the hierarchical activated carbon serve as sites for the catalytic oxidation of NO, where NO is catalytically oxidized to NO2 within the microporous structure of the hierarchical activated carbon.

[0011] In some embodiments, the nitrogen-containing functional group is pyridine nitrogen and / or graphitic nitrogen.

[0012] In some embodiments, the pore size of the micropore is 0.7-1 nm.

[0013] In some embodiments, step (b) specifically involves impregnating the hierarchical porous activated coke modified with nitrogen-containing functional groups in an aqueous solution of a crushed low-temperature denitration catalyst and applying ultrasonic oscillation until the aqueous solution becomes clear.

[0014] In some embodiments, the proportion of medium and large pores in the graded activated carbon is 30%-60% of the total pore volume.

[0015] In some embodiments, the pore size of the medium and large pores in the graded activated carbon is not less than 2 nm.

[0016] In some embodiments, the loading of the low-temperature denitrification catalyst is not less than 10 wt%.

[0017] In some embodiments, the low-temperature denitrification catalyst is a titanium-based catalyst or a manganese-based catalyst.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] This invention loads a low-temperature denitrification catalyst into a staged porous activated coke, directly utilizing the NO2 generated during the reaction to decompose ammonium bisulfate in situ. This does not affect the continuous and stable operation of the reaction, eliminates the need for an additional heating and regeneration device, reduces the complexity of the equipment, and has low energy consumption. Attached Figure Description

[0020] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0021] Figure 1 This is a flowchart of the method for improving the water and sulfur resistance of low-temperature denitrification catalysts according to the present invention. Detailed Implementation

[0022] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0023] The following describes, with reference to the accompanying drawings, a method for improving the water and sulfur resistance of low-temperature denitrification catalysts according to embodiments of the present invention.

[0024] like Figure 1 As shown, the method of the present invention for improving the water and sulfur resistance of low-temperature denitrification catalysts includes the following steps:

[0025] (a) Modifying the micropores of hierarchical activated carbon using nitrogen-containing functional groups;

[0026] (b) The low-temperature denitrification catalyst was loaded into the mesopores of the graded activated coke to obtain a supported catalyst.

[0027] In step (a), the modification of the micropores of the hierarchical porous activated carbon using nitrogen-containing functional groups specifically involves thermal annealing the activated carbon with a mixture of NH3 and N2 gas to modify its microporous structure. The nitrogen-containing functional groups are pyridine nitrogen and / or graphitic nitrogen, and the pore size is 0.7-1 nm. The micropores of the hierarchical porous activated carbon serve as sites for the catalytic oxidation of NO. NO is catalytically oxidized to NO2 within the microporous structure of the activated carbon. The NO2 generated in the micropore space interacts with NO, O2, and ammonium bisulfate, achieving efficient decomposition of ammonium bisulfate under low-temperature conditions: NO2 + NO + O2 + NH4HSO4 → H2SO4 + N2 + H2O. The nitrogen content in the hierarchical porous activated carbon modified with nitrogen-containing functional groups is not less than 2.5 at%, to achieve efficient catalytic oxidation of NO to generate NO2 for in-situ decomposition of ammonium bisulfate.

[0028] In step (b), the low-temperature denitration catalyst is loaded into the meso- and macropores of a hierarchical activated coke to obtain a supported catalyst, i.e., an improved low-temperature denitration catalyst. Specifically, the low-temperature denitration catalyst is crushed and dispersed in water, and the hierarchical activated coke is impregnated in an aqueous solution containing the crushed low-temperature denitration catalyst and subjected to ultrasonic vibration until the aqueous solution becomes clear. At this point, the crushed low-temperature denitration catalyst is loaded into the hierarchical activated coke. The pore size of the meso- and macropores of the hierarchical activated coke is not less than 2 nm, and the pore volume of the meso- and macropores accounts for 30%-60% of the total pore volume. This ensures that the hierarchical activated coke maintains a certain microporosity while effectively loading the metal-based catalyst. Low-temperature denitration catalysts are generally monolithic catalysts, and even after crushing, their size is relatively large, generally exceeding 10 nm. Therefore, the low-temperature denitration catalyst loaded after impregnation is generally only loaded into the meso- and macropore structure of the hierarchical activated coke. The loading of the low-temperature denitration catalyst is not less than 10 wt%. The low-temperature denitration catalyst is a metal-based catalyst, which can be a titanium-based catalyst or a manganese-based catalyst. Among them, the titanium-based catalyst can be a V2O5-WO3 / TiO2 catalyst or a V2O5-MoO3 / TiO2 catalyst.

[0029] The following specific embodiments illustrate the method for simultaneous desorption and resource recovery of multiple pollutants in an adsorption-saturated activated char according to the present invention.

[0030] Example 1:

[0031] Hierarchical activated carbon with a macropore volume ratio of 40% and a micropore diameter of 0.7 nm was selected and subjected to thermal annealing at 900℃ for 1 h using a mixture of NH3 and N2 gas, with an NH3 to N2 ratio of 1:1. 0.4 g of V2O5-WO3 / TiO2 catalyst was crushed and dispersed in water. 2 g of hierarchical activated carbon with nitrogen-containing functional group-modified micropores was impregnated in the aqueous solution of the crushed V2O5-WO3 / TiO2 catalyst and subjected to ultrasonic vibration until the aqueous solution became clear. This process loaded the crushed V2O5-WO3 / TiO2 catalyst onto the obtained hierarchical activated carbon via impregnation. The resulting supported catalyst was placed in a fixed-bed system for SCR experiments. The total gas flow rate in the SCR experiment was 400 mL / min, with N2 as the carrier gas, 500 ppm NO, 500 ppm NH3, 200 ppm SO2, 10% H2O, and 5% O2. The SCR reaction temperature was 240℃. After the reaction reached steady state, the NO conversion rate remained at 90%.

[0032] Example 2:

[0033] Hierarchical activated carbon with a macropore volume ratio of 30% and a micropore diameter of 0.7 nm was selected and subjected to thermal annealing at 900℃ for 1 h using a mixture of NH3 and N2 gas, with an NH3 to N2 ratio of 1:1. 0.4 g of V2O5-WO3 / TiO2 catalyst was crushed and dispersed in water. 2 g of hierarchical activated carbon with nitrogen-containing functional group-modified micropores was impregnated in the aqueous solution of the crushed V2O5-WO3 / TiO2 catalyst and subjected to ultrasonic vibration until the aqueous solution became clear. This process loaded the crushed V2O5-WO3 / TiO2 catalyst onto the obtained hierarchical activated carbon via impregnation. The resulting supported catalyst was placed in a fixed-bed system for SCR experiments. The total gas flow rate in the SCR experiment was 400 mL / min, with N2 as the carrier gas, 500 ppm NO, 500 ppm NH3, 200 ppm SO2, 10% H2O, and 5% O2. The SCR reaction temperature was 240℃. After the reaction reached steady state, the NO conversion rate remained at 65%.

[0034] Example 3:

[0035] Hierarchical activated carbon with a macropore volume ratio of 60% and a micropore diameter of 0.7 nm was selected and subjected to thermal annealing at 900℃ for 1 h using a mixture of NH3 and N2 gas, with an NH3 to N2 ratio of 1:1. 0.4 g of V2O5-WO3 / TiO2 catalyst was crushed and dispersed in water. 2 g of hierarchical activated carbon with nitrogen-containing functional group-modified micropores was impregnated in the aqueous solution of the crushed V2O5-WO3 / TiO2 catalyst and subjected to ultrasonic vibration until the aqueous solution became clear. This process loaded the crushed V2O5-WO3 / TiO2 catalyst onto the obtained hierarchical activated carbon via impregnation. The resulting supported catalyst was placed in a fixed-bed system for SCR experiments. The total gas flow rate in the SCR experiment was 400 mL / min, with N2 as the carrier gas, 500 ppm NO, 500 ppm NH3, 200 ppm SO2, 10% H2O, and 5% O2. The SCR reaction temperature was 240℃. After the reaction reached steady state, the NO conversion rate remained at 70%.

[0036] Comparative Example 1:

[0037] SCR experiments were conducted using 0.4 g of V₂O₅-WO₃ / TiO₂ catalyst in a fixed-bed system. The total gas flow rate was 400 mL / min, with N₂ as the carrier gas, and the following concentrations of N₂, NH₃, SO₂, H₂O, and O₂. The SCR reaction temperature was 240 °C. After the reaction reached steady state, the NO conversion rate remained at 30%.

[0038] According to Comparative Example 1 and Examples 1-3, the NO conversion rate in the SCR experiment was low when the low-temperature denitrification catalyst was not loaded into the mesopores of the graded activated coke. The supported catalyst obtained by loading the low-temperature denitrification catalyst into the mesopores of the graded activated coke improved the performance of the low-temperature denitrification catalyst and enhanced its resistance to water and sulfur.

[0039] Comparative Example 2:

[0040] Hierarchical activated carbon with a macropore volume ratio of 10% and a micropore diameter of 0.7 nm was selected and subjected to thermal annealing at 900℃ for 1 h using a mixture of NH3 and N2 gas, with an NH3 to N2 ratio of 1:1. 0.4 g of V2O5-WO3 / TiO2 catalyst was crushed and dispersed in water. 2 g of hierarchical activated carbon with nitrogen-containing functional group-modified micropores was impregnated in the aqueous solution of the crushed V2O5-WO3 / TiO2 catalyst and subjected to ultrasonic vibration until the aqueous solution became clear. This process loaded the crushed V2O5-WO3 / TiO2 catalyst onto the obtained hierarchical activated carbon via impregnation. The resulting supported catalyst was placed in a fixed-bed system for SCR experiments. The total gas flow rate in the SCR experiment was 400 mL / min, with N2 as the carrier gas, 500 ppm NO, 500 ppm NH3, 200 ppm SO2, 10% H2O, and 5% O2. The SCR reaction temperature was 240℃. After the reaction reached steady state, the NO conversion rate remained at 40%.

[0041] Comparative Example 3:

[0042] Hierarchical activated carbon with a macropore volume ratio of 80% and a micropore diameter of 0.7 nm was selected and subjected to thermal annealing at 900℃ for 1 h using a mixture of NH3 and N2 gas, with an NH3 to N2 ratio of 1:1. 0.4 g of V2O5-WO3 / TiO2 catalyst was crushed and dispersed in water. 2 g of hierarchical activated carbon with nitrogen-containing functional group-modified micropores was impregnated in the aqueous solution of the crushed V2O5-WO3 / TiO2 catalyst and subjected to ultrasonic vibration until the aqueous solution became clear. This process loaded the crushed V2O5-WO3 / TiO2 catalyst onto the obtained hierarchical activated carbon via impregnation. The resulting supported catalyst was placed in a fixed-bed system for SCR experiments. The total gas flow rate in the SCR experiment was 400 mL / min, with N2 as the carrier gas, 500 ppm NO, 500 ppm NH3, 200 ppm SO2, 10% H2O, and 5% O2. The SCR reaction temperature was 240℃. After the reaction reached steady state, the NO conversion rate remained at 45%.

[0043] As can be seen from Examples 1-3 and Comparative Examples 2 and 3, when the proportion of medium and large pores in the graded activated carbon to the total pore volume is too high or too low, it is not conducive to the conversion of NO.

[0044] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms may refer to different embodiments or examples. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0045] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0046] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for improving the water and sulfur resistance of low-temperature denitrification catalysts, characterized in that, The following steps are involved: (a) Modifying the micropores of hierarchical activated carbon using nitrogen-containing functional groups; (b) The low-temperature denitration catalyst is supported in the meso- and macropores of the staged activated coke to obtain a supported catalyst. Step (a) specifically involves using a mixture of NH3 and N2 to perform thermal annealing on the graded porous activated coke, thereby modifying the microporous structure of the graded porous activated coke. The nitrogen content in the graded porous activated coke modified with nitrogen-containing functional groups is not less than 2.5 at%, and the pore size of the micropores is 0.7-1 nm. Step (b) specifically involves impregnating the hierarchical activated coke with nitrogen-containing functional groups-modified micropores in an aqueous solution of the crushed low-temperature denitration catalyst and applying ultrasonic vibration until the aqueous solution becomes clear. The proportion of mesopores and macropores in the hierarchical activated coke to the total pore volume is 30%-60%, and the loading of the low-temperature denitration catalyst is not less than 10 wt%. The micropores of the hierarchical activated carbon serve as sites for the catalytic oxidation of NO, where NO is catalytically oxidized to NO2 within the microporous structure of the hierarchical activated carbon.

2. The method as described in claim 1, characterized in that, The nitrogen-containing functional group is pyridine nitrogen and / or graphitic nitrogen.

3. The method as described in claim 1, characterized in that, The pore size of the medium and large pores in the graded activated carbon is not less than 2 nm.

4. The method as described in claim 1, characterized in that, The low-temperature denitrification catalyst is a titanium-based catalyst or a manganese-based catalyst.

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