Boron-nitrogen double-doped narrow microporous activated carbon capable of simultaneously removing various peculiar smell and odor pollutants and preparation method of boron-nitrogen double-doped narrow microporous activated carbon

Abstract

The invention belongs to the technical field of collaborative treatment of peculiar smell and odor pollutants, and particularly relates to boron-nitrogen double-doped narrow microporous activated carbon capable of simultaneously removing various peculiar smell and odor pollutants and a preparation method of the boron-nitrogen double-doped narrow microporous activated carbon. A boron source, a nitrogen source and the biomass carbonized material are ground and mixed, the obtained mixture is activated, an activated product is soaked in a hydrochloric acid solution, suction filtration, washing and drying are conducted, and the boron-nitrogen double-doped narrow-micropore activated carbon is obtained. The preparation method provided by the invention can regulate and control the aperture structure and the surface property of the activated carbon, endows the activated carbon with catalytic performance, and obtains the normal-temperature purification material with excellent purification performance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of synergistic treatment of odor malodor pollutants, and particularly relates to a boron-nitrogen double-doped narrow microporous activated carbon capable of simultaneously removing multiple odor malodor pollutants and a preparation method thereof. BACKGROUND

[0002] Odor malodor pollutants such as hydrogen sulfide (H2S), mercaptans (such as CH3SH) and ammonia (NH3) have a significant negative impact on human health, quality of life and the ecological environment. Odor malodor pollutants have a strong irritating odor, and short-term exposure to them can cause eye, nose and throat irritation; long-term exposure can cause respiratory inflammation, chronic bronchitis, and damage to the nervous system, which can cause respiratory paralysis and coma.

[0003] In industry, these pollutants are effectively treated by various methods. Absorption method has high efficiency, and alkali solution (NaOH) is used to absorb H2S and acidic solution (H3PO4) is used to absorb NH3 in places producing medium-high concentration waste gas (such as chemical plants and farms), but salt-containing wastewater is generated and needs subsequent treatment. Thermal combustion method is complete in treatment, and high temperature (600-800 °C) can oxidize H2S and CH3SH into SO2, but the energy consumption is high and secondary pollutants need to be controlled. Biological method is suitable for places producing medium-low concentration and large wind volume waste gas, such as food processing plants and composting sites, and has low operating cost and no secondary pollution, but it takes a long time to start and is greatly affected by temperature and humidity. Single technology often cannot meet the complex odor malodor treatment requirements, so multiple processes need to work together. However, the composite process increases the treatment steps and the complexity of the system. Activated carbon adsorption can simultaneously treat multiple odor malodor gases, and has low cost and simple operation, but ordinary commercial activated carbon has low adsorption capacity and needs to be replaced frequently. Therefore, it is necessary to develop activated carbon purification materials that can simultaneously and efficiently remove multiple odor malodor pollutants.

[0004] Currently, there are various activated carbons that can remove H2S or NH3 single component gas alone, but few adsorbents can simultaneously remove H2S and NH3. The Chinese invention patent application with publication number CN117019100A discloses a spherical impregnated carbon adsorbent that can simultaneously remove NH3 and H2S. The porous spherical carbon is first modified by nitrogen doping, then loaded with metal oxides, and finally loaded with CuSO4 and metal chlorides to prepare a spherical impregnated carbon adsorbent that can efficiently purify NH3 and H2S. Among them, the humidity is 50 10% when, after 30% urea doping, 8% magnesium oxide loading, 10% copper sulfate and 10% nickel chloride impregnation, the modified carbon has the highest NH3 and H2S breakthrough adsorption capacity, reaching 72 mg / g and 245 mg / g respectively. The Chinese invention patent application with publication number CN117019100A discloses a supported compound activated carbon fiber paper composite adsorbent for removing trace odor gas at room temperature, which can remove trace H2S and NH3 in a closed space. The adsorbent loaded with 18% cobalt has a breakthrough adsorption capacity of 51 mg / g for NH3, and the adsorbent loaded with cobalt and copper has a breakthrough adsorption capacity of 48 mg / g for H2S. The above two kinds of activated carbon can remove H2S and NH3 at the same time, but the preparation process of these two kinds of adsorbents is complex, both of them are loaded with metal ions, and the cost is high, which will be restricted by cost and process in large-scale application.

[0005] The principle of activated carbon for simultaneous removal of H2S, CH3SH and NH3 is to first adsorb them on the surface active sites, and then catalytically oxidize H2S and CH3SH to S element or SO4 2- , and then react with NH3 by using its acidity. Nitrogen doping is beneficial to improve the micropore structure of activated carbon, introduce basic sites to adsorb H2S and CH3SH. Boron doping can enhance the acidic sites of activated carbon and enhance the adsorption of NH3.

[0006] Therefore, it is of great significance to prepare a boron and nitrogen double-doped narrow microporous activated carbon which can simultaneously remove various odor and malodorous pollutants. SUMMARY

[0007] In view of the low performance of activated carbon catalyst in removing odor and malodorous pollutants in the prior art, the present application provides a boron and nitrogen double-doped narrow microporous activated carbon which can simultaneously remove various odor and malodorous pollutants and a preparation method thereof, which realizes the optimization and control of the pore structure of activated carbon and the amount of boron and nitrogen doping, and enhances the adsorption and catalytic oxidation performance of activated carbon for H2S, CH3SH and NH3 and other odor pollutants.

[0008] The technical scheme of the present application is as follows: A preparation method of a boron and nitrogen double-doped narrow microporous activated carbon which can simultaneously remove various odor and malodorous pollutants, comprising the following steps: Step S1, grinding and mixing a boron source, a nitrogen source and biomass carbonization material; Step S2, activating the mixture obtained in step S1; Step S3, immersing the activated product in a hydrochloric acid solution, and then performing suction filtration, washing and drying to obtain a boron and nitrogen double-doped narrow microporous activated carbon.

[0009] Preferably, the boron source is potassium borate.

[0010] Preferably, the nitrogen source is urea, cyanamide or melamine.

[0011] Preferably, the biomass carbonization material is bamboo carbonization material.

[0012] Preferably, the mass ratio of potassium borate to biomass carbonization material in step S1 is (0.1-2):1.

[0013] Preferably, the mass ratio of potassium borate to biomass carbonization material in step S1 is 1:1.

[0014] Preferably, the mass ratio of urea to biomass carbonization material is (0.1-0.5):1.

[0015] Preferably, the mass ratio of urea to biomass carbonization material is 0.2:1.

[0016] Preferably, the activation temperature in step S2 is 750-950℃, the activation time is 100-300min, and the heating rate is 5℃ / min.

[0017] Preferably, the activation temperature in step S2 is 850℃, the activation time is 200min, and the heating rate is 5℃ / min.

[0018] Preferably, step S3 specifically comprises: the activated product is immersed in a hydrochloric acid solution for 6h, washed with deionized water for 3-5 times after suction filtration until neutral, and dried at 80-120℃ for 8-16h.

[0019] Preferably, step S3 specifically comprises: the activated product is immersed in a hydrochloric acid solution for 6h, washed with deionized water for 3-5 times after suction filtration until neutral, and dried at 105℃ for 12h.

[0020] A boron-nitrogen double-doped narrow microporous activated carbon, the loading of boron element is 0.5-10%, the loading of nitrogen element is 0.5-2%, the specific surface area is >1200m 2 / g, the volume of narrow micropores with a pore size of less than 1nm is >0.3cm 3 / g.

[0021] The application of a boron-nitrogen double-doped narrow microporous activated carbon for simultaneously removing hydrogen sulfide, methyl mercaptan and ammonia in air.

[0022] Compared with the prior art, the present application has the following advantages: 1. The present application adopts a one-step synthesis method to prepare a boron-nitrogen double-doped narrow microporous activated carbon, which is simple and efficient, and has the conditions for large-scale production.

[0023] 2. This invention uses potassium borate as a raw material, which also acts as an activator and boron source, simplifying the preparation process and reducing the preparation cost.

[0024] 3. The boron-nitrogen dual-doped narrow-pore activated carbon prepared by this invention has abundant narrow micropores and a large number of acidic and basic sites on its surface, which is beneficial to the adsorption and catalytic conversion of H2S, CH3SH, NH3, etc.

[0025] 4. The boron-nitrogen dual-doped narrow microporous activated carbon prepared by this invention has excellent adsorption and catalytic performance. It can simultaneously catalyze the removal of H2S, CH3SH and NH3 at room temperature, with a breakthrough time of up to 3 hours, and the removal rates of H2S, CH3SH and NH3 are up to 95%, 90% and 90% respectively. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the embodiments will be briefly introduced below. The features and advantages of the present invention can be more clearly understood by referring to the accompanying drawings. The accompanying drawings are schematic and should not be construed as limiting the present invention in any way. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a comparison chart of the H2S catalytic performance of boron-nitrogen-doped activated carbon in Example 1 and Comparative Example 2 of the present invention.

[0028] Figure 2 This is a pore size distribution diagram of boron-nitrogen doped activated carbon in Embodiment 1 and Comparative Example 2 of the present invention.

[0029] Figure 3 This is a comparison chart of the H2S catalytic performance of activated carbon with different boron and nitrogen doping ratios in Example 1 of the present invention.

[0030] Figure 4 This is a comparison chart of the NH3 catalytic performance of boron-nitrogen-doped activated carbon in Examples 1, 1, and 2 of this invention.

[0031] Figure 5 This is a comparison chart of the CH3SH catalytic performance of boron-nitrogen-doped activated carbon in Examples 1, 1, and 2 of this invention.

[0032] Figure 6 This is a comparison chart of odor concentration changes when boron-nitrogen dual-doped activated carbon from Embodiment 1 of the present invention is applied to odor control in an underground sewage treatment plant. Detailed Implementation

[0033] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0034] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0035] H2S, CH3SH, and NH3 are all small molecule pollutants with molecular dynamic diameters ranging from 0.26 to 0.45 nm. Extensive research on activated carbon catalysts has revealed that narrow micropores smaller than 1 nm are beneficial for the adsorption of H2S, CH3SH, and NH3 onto activated carbon. However, the pore structure of activated carbon produced from different raw materials varies significantly. This invention has found that bamboo more readily generates abundant narrow micropores during the activation process compared to coal, phenolic resin, and various types of wood. Therefore, bamboo carbonization was selected as the carbon source.

[0036] Existing activated carbon has a limited number of surface active sites, resulting in weak removal capabilities for H2S and CH3SH. Therefore, activated carbon needs modification to improve its catalytic oxidation performance. This invention involves simultaneously doping activated carbon with B and N atoms. Nitrogen atoms increase the number of surface defects and active sites. The nitrogen doping process introduces nitrogen-containing functional groups, promoting the adsorption of H2S, CH3SH, O2, and H2O. The dissociation of H2S and oxygen generates free radicals, further enhancing catalytic oxidation performance. Nitrogen-doped activated carbon not only possesses a good pore structure and desulfurization performance but also concentrates the distribution of catalytic oxidation products, facilitating further adsorption and reaction with NH3. Boron doping can form Lewis acid sites on the surface, enhancing the interaction with the alkaline gas NH3. The lone pairs of electrons in NH3 molecules can combine with empty orbitals of boron, significantly improving the activated carbon's adsorption capacity for NH3. Preferably, potassium borate is chosen, serving as both an activator and a dopant.

[0037] An appropriate amount of potassium borate is beneficial for pore development and suitable boron doping. Excessive B2O3 will accumulate on the surface of activated carbon, hindering boron atom doping into the carbon framework. Furthermore, the accumulated B2O3 will clog the pores, preventing H2S, CH3SH, and NH3 from entering the inner surface of the activated carbon, thereby reducing its catalytic performance. In this invention, the mass ratio of potassium borate to bamboo carbonized material is 0.1:1 to 2:1. Preferably, the optimal ratio is 1:1.

[0038] Urea can enhance the activation process, resulting in a richer pore structure. However, when excessive urea is used, the activation process becomes more vigorous, and some micropores <1 nm will merge and grow into larger mesopores. The decrease in the volume of narrow micropores is detrimental to the adsorption of small molecule pollutants H2S, CH3SH, and NH3 by activated carbon, subsequently affecting catalytic performance. In this invention, the mass ratio of urea to bamboo carbonization material is 0.1:1 to 0.5:1. Preferably, the optimal ratio is 0.2:1.

[0039] Activation temperature and activation time affect the pore structure and boron-nitrogen doping form of activated carbon. In this invention, the activation temperature is 750~950℃, the activation time is 100~300min, and the heating rate is 5℃ / min. Preferably, the optimal activation process is: activation temperature 850℃, activation time 200min.

[0040] In summary, this invention proposes a method for preparing boron and nitrogen-doped narrow-pore activated carbon that can simultaneously remove multiple odorous pollutants. The method also includes targeted design of the doping ratio, activation temperature, and activation time, resulting in an activated carbon catalyst with abundant narrow micropores and uniformly dispersed heteroatoms.

[0041] Example 1 (1) Potassium borate, urea and bamboo carbonization material are ground together in different proportions to make them evenly mixed. The mass ratio of potassium borate to bamboo carbonization material is 0.1:1, 0.5:1, 1:1 and 2:1, and the mass ratio of urea to bamboo carbonization material is 0.1:1, 0.2:1 and 0.5:1. (2) Place the mixture obtained in step (1) in a tube furnace, introduce nitrogen gas, and heat it to 850°C at 5°C / min for 200 min to activate it; (3) The activated product obtained in step (2) was immersed in hydrochloric acid solution for 6 hours, filtered, washed 5 times with deionized water, and dried at 105°C for 12 hours to obtain a boron-nitrogen dual-doped narrow microporous activated carbon catalyst.

[0042] The boron-nitrogen dual-doped narrow-pore activated carbon described in this embodiment is denoted as B. x N y AC (x=0.1, 0.5, 1, 2; y=0.1, 0.2, 0.5).

[0043] Comparative Example 1 (1) Potassium borate and bamboo carbonized material are ground together in different proportions to make them evenly mixed. The mass ratio of potassium borate to bamboo carbonized material is 0.1:1, 0.5:1, 1:1, and 2:1. (2) Place the mixture obtained in step (1) in a tube furnace, introduce nitrogen gas, and heat it to 850°C at 5°C / min for 200 min to activate it; (3) The activated product obtained in step (2) was immersed in hydrochloric acid solution for 6 hours, filtered, washed 5 times with deionized water, and dried at 105°C for 12 hours to obtain a boron-nitrogen dual-doped narrow microporous activated carbon catalyst.

[0044] The boron-doped activated carbon catalyst described in this comparative example is denoted as B. x AC (x=0.1, 0.5, 1, 2).

[0045] Comparative Example 2 (1) Grind urea and bamboo carbonized material together in different proportions to make them evenly mixed, wherein the mass ratio of urea to carbonized material is 0.1:1, 0.2:1, and 0.5:1; (2) Place the mixture obtained in step (1) in a tube furnace, introduce nitrogen gas, and heat it to 850°C at 5°C / min for 200 min to activate it; (3) The activated product obtained in step (2) was immersed in hydrochloric acid solution for 6 hours, filtered, washed 5 times with deionized water, and dried at 105°C for 12 hours to obtain a boron-nitrogen dual-doped narrow microporous activated carbon catalyst.

[0046] The N-doped activated carbon catalyst described in this comparative example is denoted as N... y AC (y=0.1, 0.2, 0.5).

[0047] The performance of catalytic oxidation of H2S, CH3SH, and NH3 in Examples 1, 1, and 2 was tested. The test methods are as follows: The catalyst performance was evaluated using a quartz fixed-bed reactor. 100 mg of catalyst was packed into a quartz tube (6 mm inner diameter, 350 mm long), secured at both ends with quartz wool, and a mixed reaction gas (100 ppm H₂S + 30 ppm CH₃SH + 100 ppm NH₃ + 1% O₂ + H₂O + N₂) was introduced at a total flow rate of 100 mL. min -1 The reaction temperature was controlled at 25℃ and the humidity at 50%. During the test, the exhaust gas from the catalyst reaction was passed into a gas chromatograph (GC-2014) equipped with a flame ionization detector (FID) for online monitoring. The odor removal rate (the removal rate of H2S and CH3SH refers to the conversion rate of the catalytic reaction, and the removal rate of NH3 refers to the conversion rate of the reaction with H2SO4 or the removal rate of adsorption) was calculated using the following formula:

[0048]

[0049]

[0050] in, , , The values ​​represent the H2S removal rate (%), the initial H2S concentration (ppm), and the H2S concentration (ppm) after the catalytic reaction, respectively. , , The values ​​represent the CH3SH removal rate (%), the initial CH3SH concentration (ppm), and the CH3SH concentration (ppm) after the catalytic reaction, respectively. , , These represent the NH3 removal rate (%), initial NH3 concentration (ppm), and NH3 concentration (ppm) after the catalytic reaction, respectively. A breakthrough is defined as when the outlet concentration of any odorous pollutant reaches 10% of its initial concentration.

[0051] Figure 1 This is a comparison chart of the H2S catalytic performance of boron-nitrogen-doped activated carbon in Example 1 and Comparative Example 2 of this invention. As can be seen from the chart, the H2S removal rate of the potassium borate-doped activated carbon is significantly better than that of the undoped sample, mainly due to the pore-activating effect of potassium borate.

[0052] Figure 2 The figures show the pore size distribution of boron-nitrogen-doped activated carbon in Examples 1 and 2 of this invention. As can be seen from the figures, the micropores, especially the narrow micropores, of the activated carbon are further developed after potassium borate doping.

[0053] Figure 3 This is a comparison chart of the H2S catalytic performance of activated carbon with different boron-nitrogen doping ratios in Example 1 of the present invention. The results show that a urea to bamboo carbonization mass ratio of 0.2:1 is most conducive to pore development, while nitrogen doping introduces abundant alkaline sites, thereby enhancing the H2S removal effect.

[0054] Figure 4 This is a comparative graph showing the NH3 catalytic performance of boron-nitrogen-doped activated carbon in Examples 1, 1, and 2 of this invention. The removal rate of NH3 by the boron-doped activated carbon is higher than that of the nitrogen-doped activated carbon. This is mainly due to the fact that boron doping provides a large number of Lewis acid sites, which improves the adsorption capacity for NH3.

[0055] Figure 5 This is a comparison chart of the CH3SH catalytic performance of boron-nitrogen-doped activated carbon in Examples 1, 1, and 2 of this invention. The boron-nitrogen dual-doping method showed the best CH3SH removal effect.

[0056] Figure 6 The boron-nitrogen dual-doped activated carbon B1N of Example 1 of this invention 0.2A comparison chart of odor concentration changes when AC is applied to odor control at an underground wastewater treatment plant. After treatment with activated carbon catalysis, the odor concentration decreased significantly and the effect lasted for a long time.

[0057] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0058] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0059] In this invention, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The term "multiple" refers to two or more unless otherwise expressly defined.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing boron-nitrogen dual-doped narrow-pore activated carbon capable of simultaneously removing multiple odorous pollutants, characterized in that, Includes the following steps: Step S1: Grind and mix the boron source, nitrogen source, and biomass carbonization material; Step S2: Activate the mixture obtained in step S1; Step S3: Immerse the activated product in hydrochloric acid solution, and obtain boron-nitrogen dual-doped narrow microporous activated carbon by filtration, washing and drying.

2. The method for preparing narrow microporous activated carbon according to claim 1, characterized in that, The boron source is potassium borate, the nitrogen source is urea, cyanamide or melamine, and the biomass carbonized material is bamboo carbonized material.

3. The method for preparing narrow microporous activated carbon according to claim 2, characterized in that, The mass ratio of potassium borate to biomass carbonization material is (0.1~2):

1.

4. The method for preparing narrow microporous activated carbon according to claim 2, characterized in that, The mass ratio of urea to biomass carbonization material is (0.1~0.5):

1.

5. The method for preparing narrow microporous activated carbon according to claim 2, characterized in that, In step S1, the mass ratio of potassium borate to biomass carbonization material is 1:1, and the mass ratio of urea to biomass carbonization material is 0.2:

1.

6. The method for preparing narrow microporous activated carbon according to claim 2, characterized in that, In step S2, the activation temperature is 750~950℃, the activation time is 100~300min, and the heating rate is 5℃ / min.

7. The method for preparing narrow microporous activated carbon according to claim 2, characterized in that, In step S2, the activation temperature is 850℃, the activation time is 200min, and the heating rate is 5℃ / min.

8. The method for preparing narrow microporous activated carbon according to claim 2, characterized in that, Step S3 specifically includes: soaking the activated product in hydrochloric acid solution for 6 hours, filtering it, washing it with deionized water 3 to 5 times until neutral, and drying it at 80 to 120°C for 8 to 16 hours.

9. A boron-nitrogen dual-doped narrow-pore activated carbon obtained by the method for preparing narrow-pore activated carbon according to any one of claims 1-8, characterized in that, The loading of boron is 0.5-10%, the loading of nitrogen is 0.5-2%, and the specific surface area is >1200 m². 2 / g, narrow micropores with a pore size of less than 1nm have a volume >0.3cm³. 3 / g.

10. An application of boron-nitrogen dual-doped narrow microporous activated carbon obtained by the method for preparing narrow microporous activated carbon according to any one of claims 1-8, for the simultaneous removal of hydrogen sulfide, methanethiol and ammonia from the air.

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