Modified coal-based activated carbon for VOCs waste gas treatment and preparation method of modified coal-based activated carbon
By modifying coal-based activated carbon with composite modifiers to form a microporous-mesoporous hierarchical structure, the problems of pore size limitation and acid corrosion of existing coal-based activated carbon in treating industrial VOCs waste gas are solved, achieving efficient adsorption of acid/alkaline VOCs and long-term use.
Patent Information
- Application Number
- CN202511225951.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-29
- Publication Date
- 2025-11-11
AI Technical Summary
Existing coal-based activated carbon, when treating industrial VOCs waste gas, has the limitation that its pore size is mainly micropores, which cannot effectively absorb and purify polar VOCs, and acidic gases cause acid corrosion, resulting in a short service life.
A composite modifier composed of zinc sulfate and melamine is used to treat coal powder through impregnation and segmented temperature-controlled activation, forming a microporous-mesoporous hierarchical structure, which enhances the resistance to acid/alkaline VOCs and the chemical adsorption effect.
It significantly improves pore structure and service life, enhances adsorption capacity for acidic/alkaline VOCs, and is suitable for treating industrial VOCs waste gas with high humidity and complex composition.
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Abstract
Description
Technical Field
[0001] This application relates to the field of waste gas treatment materials technology, and more specifically, it relates to a modified coal-based activated carbon for VOCs waste gas treatment and a method for preparing the same. Background Technology
[0002] In recent years, heavy industry has begun to impose stricter controls on the emission of industrial VOCs. As a result, various filter materials that can effectively remove industrial VOCs have emerged, with activated carbon adsorption material being the most widely used example.
[0003] The activated carbon adsorption material used in related technologies can effectively trap most pollutants in industrial VOCs waste gas through the physical adsorption of its pore structure. However, due to its surface chemical inertness, it cannot absorb and purify pollutants in industrial VOCs waste gas. Therefore, some companies have tried to enhance the selective adsorption of polar VOCs (such as ketones and esters) by introducing functional groups such as amino (NH2) and sulfonic acid (-SO3H) groups into coal-based activated carbon. However, since its pore size is generally microporous and the industrial VOCs waste gas contains acidic gases that will cause acid corrosion, it is not conducive to the synergistic adsorption of complex components and has a short effective service life.
[0004] In summary, to address the drawbacks of traditional coal-based activated carbon applications, a modified coal-based activated carbon for VOCs waste gas treatment and its preparation method are provided. Summary of the Invention
[0005] To address the aforementioned technical problems, this application provides a modified coal-based activated carbon for VOCs waste gas treatment and its preparation method. This adsorption material still exhibits high adsorption efficiency (≥90%) and long-lasting effectiveness in the treatment of industrial VOCs waste gas containing acidic gases (SO2, NOx).
[0006] In a first aspect, this application provides a modified coal-based activated carbon for VOCs waste gas treatment, employing the following technical solution: A modified coal-based activated carbon for VOCs waste gas treatment, wherein the modified coal-based activated carbon is prepared by impregnating coal powder with a composite modifier and then activating it, wherein the composite modifier is composed of zinc sulfate, melamine and a solvent.
[0007] Preferably, the composite modifier is composed of the following components by weight percentage: 5-8 wt% zinc sulfate, 3-7 wt% melamine, and the balance being solvent.
[0008] Preferably, the ratio of coal powder to composite modifier is 1:(4-6).
[0009] Preferably, the pulverized coal is anthracite with an ash content of ≤5% and a particle size of 80-120 mesh.
[0010] Preferably, the activation is a segmented temperature-controlled activation.
[0011] By adopting the above technical solution, the pore structure of coal powder that has been activated after being impregnated with a composite modifier is significantly improved. At the same time, the resistance to acid / alkaline VOCs gas and the chemical adsorption effect are enhanced by the doping and introduction of nitrogen and sulfur elements. Based on the relevant test data and comparative experiments, the possible reasons are: 1) The improvement of its pore structure is due to the generation of ZnO template by ZnSO4 under high temperature decomposition, while the carbonization of melamine causes the expansion of the cracked gas to create pores, which in turn synergistically form a microporous-mesoporous hierarchical structure. 2) Its resistance to acidic gases and adsorption effect are mainly due to the introduction of melamine. The nitrogen-containing free radicals (-NH2, -CN) generated by its cracking are easy to combine with the carbon skeleton to form alkaline sites. 3) In addition, the alkaline sites (N doped) formed will also form CSC or C-SOx structures with the residual sulfur elements, i.e. acidic sites, to form amphoteric surfaces, which synergistically endow activated carbon with the effect of adsorbing acidic / alkaline VOCs gases.
[0012] Secondly, this application provides a method for preparing modified coal-based activated carbon for VOCs waste gas treatment, employing the following technical solution: A method for preparing modified coal-based activated carbon for VOCs waste gas treatment, comprising the following steps: S1. First, mix and impregnate the coal powder and composite modifier according to the corresponding weight ratio, and stir at a constant temperature of 60℃ for 6-8 hours. Then, dry and dehydrate the mixture, and grind it to a particle size of ≤0.10mm to obtain the coal precursor. S2. Then, the coal precursor obtained in S1 is activated in a segmented temperature-controlled atmosphere under nitrogen. S3, then acid washing and water washing are performed sequentially to remove the ZnO template and unreacted salts from the product obtained in S2. After drying, the modified coal-based activated carbon adsorbent material is obtained.
[0013] Preferably, the specific process of segmented temperature-controlled activation in S2 is as follows: That is, the coal precursor obtained in S1 is first pre-carbonized at 400-500℃ for 1-2 hours, and then the temperature is raised to 700-800℃ for further high-temperature activation for 2-3 hours.
[0014] Preferably, the pickling and washing processes in S3 are as follows: First, soak the product obtained in S2 in 1-2M HCl solution at a solid-liquid ratio of 1:(1-3) for 12-24 hours, then wash with deionized water until neutral, and finally dry at 100-120℃ to remove water.
[0015] By adopting the above technical solution, the modified coal-based activated carbon for VOCs waste gas treatment prepared by the above steps all have excellent pore structure and surface adsorption effect, and the acid resistance and service life of the coal-based activated carbon itself are also significantly improved. The specific reasons are analyzed as follows: 1) The main purpose of the pre-carbonization process is to control the initial decomposition of melamine, release NH3 gas to form initial pores, and ZnSO4 will initially generate ZnO precursor; 2) The purpose of the high-temperature activation process is to ensure that melamine is completely decomposed, thereby releasing a large amount of nitrogen-containing gas to achieve N doping. ZnO will be further generated and used as a hard template to form mesopores through etching. Residual sulfur does not need to be removed and can enhance surface acidity by generating CS bonds.
[0016] Thirdly, this application provides an application of modified coal-based activated carbon for VOCs waste gas treatment, which is suitable for industrial VOCs waste gas treatment with high humidity and complex composition, and is resistant to acid gases and has a long effective service life.
[0017] Fourthly, this application provides a composite modifier for modifying activated carbon adsorbent materials, which is composed of the following components in weight percentage: 5-8 wt% zinc sulfate, 3-7 wt% melamine, and the balance being solvent. This composite modifier has the effect of both pore size improvement and surface modification.
[0018] In summary, this application has the following beneficial effects: 1. In this application, the coal powder that has been impregnated and activated by the composite modifier has not only significantly improved its pore structure and formed a microporous-mesoporous hierarchical structure, but also formed an amphoteric surface through the doping of nitrogen and sulfur elements, thereby ensuring the resistance to acid / alkaline VOCs gases and the chemical adsorption effect. 2. The modified coal-based activated carbon for VOCs waste gas treatment prepared by the process described in this application has stable and uniform performance, excellent pore structure and surface adsorption effect, and the acid resistance and service life of the coal-based activated carbon itself are also significantly improved, making it suitable for industrial-scale production. 3. The modified coal-based activated carbon adsorption material for VOCs waste gas treatment in this application effectively overcomes the original application drawbacks compared with traditional coal-based activated carbon. It is more suitable for industrial VOCs waste gas treatment with high humidity and complex composition, and is resistant to acid gases and has a long effective service life. 4. The composite modifier for modifying activated carbon adsorption materials in this application has the effect of both pore size improvement and surface modification, and is suitable for long-term operation in acidic / alkaline environments. Therefore, its application prospects include, but are not limited to, carbon molecular sieves, carbon adsorption columns, and carbon nanotubes in air purification and wastewater treatment. Detailed Implementation
[0019] The following detailed description of this application is based on the embodiments. Except for some specifications that are explicitly limited, the raw materials used in this application are all commercially available common materials.
[0020] Preparation Examples 1-5
[0021] A composite modifier, comprising the following components by weight percentage (per 100 kg), is prepared as a suspension by dispersion and mixing at 60°C: Table: Components and their weights (kg) in Preparation Examples 1-5 Preparation Example Components 1 2 3 4 5 Zinc sulfate 3 5 6 8 10 melamine 2 3 5 7 10 Solvent (water) 95 92 89 85 80
[0022] The coal-based activated carbon prepared in the examples was selected as the test object, and its specific surface area, mesopore ratio, total adsorption capacity, and acid / alkali resistance were tested respectively, as follows: Unmodified coal-based activated carbon (ash content ≤5%, particle size ≤0.10mm) served as the control group.
[0023] 1) Specific surface area (BET) and mesoporous ratio (BJH) test
[0024] 1.1 Sample pretreatment: First, weigh 50 mg of coal-based activated carbon as a sample, place it in a sample tube, and then degas it under vacuum at 200℃ for 6 hours (degassing instrument: VacPrep061), avoiding contact with air.
[0025] 1.2 N2 adsorption-desorption test (Micromeritics ASAP 2460 surface area analyzer): The sample tube was first equilibrated in a liquid nitrogen bath (77K), and then the relative pressure range (P / P0: 0.05-0.30) and full range scan (P / P0: 0.01-0.99) were controlled to obtain the adsorption-desorption isotherm. Then, the specific surface area was calculated using the BET model, and the desorption branch data was analyzed using the BJH method to calculate the pore volume ratio in the 2-50 nm pore size range. The test standards were in accordance with GB / T 19587-2017 and ASTM D4641-2017.
[0026] 2) Total Adsorption Test (Dynamic Adsorption Column Method)
[0027] 2.1 Adsorption column packing: First, weigh 1.0g of coal-based activated carbon as a sample and fill it evenly into a 20 mm × 300 mm adsorption column. Fix both ends of the adsorption column with quartz wool to avoid channeling.
[0028] 2.2 Test conditions: The test was conducted using 500 ppm toluene vapor (nitrogen as the carrier gas stream) at a rate of 200 mL / min at 25 ± 1 °C. The outlet concentration was recorded over time at 1-minute intervals using an online gas chromatograph (GC-2010 Plus, FID detector) until the outlet concentration reached 5% of the inlet concentration. Calculation of total adsorption capacity Q:
[0029] Where Q is the total adsorption capacity (mg / g), C0 is the inlet concentration (mg / L), F is the flow rate (L / min), and t breakthrough denoted as penetration time (min), and m as sample mass (g).
[0030] 3) Acid / alkali resistance to weathering (mixed gas penetration test) 1.1 Acid / Alkali Pretreatment (Simulating Accelerated Aging) First, immerse the test sample (coal-based activated carbon) in 1M H2SO4 solution (pH=1) for 24 hours, then wash it with deionized water until neutral, and dry it at 80℃. Alternatively: Immerse the test sample (coal-based activated carbon) in 1M NaOH solution (pH=13) for 24 hours, then wash with deionized water until neutral, and dry at 80°C.
[0031] 1.2 Mixed gas penetration experiment: Test gas composition (40℃, same temperature as industrial waste gas, flow rate 1 L / min); SO2 (100 ppm), NOx (50 ppm), toluene (200 ppm), balance N2; Then, referring to the dynamic adsorption column method in the total adsorption test, the total adsorption capacity Q before and after coal-based activated carbon treatment was recorded respectively. before and Q after And based on the ratio of the two, the adsorption efficiency retention rate is obtained. Example Example 1
[0032] A modified coal-based activated carbon for VOCs waste gas treatment is prepared using the following steps: S1. First, mix and impregnate the coal powder (anthracite, ash content ≤5%, particle size 80-120 mesh) and the composite modifier obtained in Preparation Example 1 at a weight ratio of 1:3, and stir at a constant temperature of 60℃ for 8 hours. Then, dry and dehydrate at 120℃, and grind to a particle size ≤0.10mm to obtain the coal precursor.
[0033] S2. Then, the coal precursor obtained in S1 is activated in a segmented temperature-controlled manner under a nitrogen atmosphere. The specific process steps and conditions are as follows: the coal precursor obtained in S1 is pre-carbonized at 500℃ for 1 hour, and then the temperature is raised to 800℃ for high-temperature activation for 2 hours.
[0034] S3. Then, soak the product obtained in S2 in 1M HCl solution at a solid-liquid ratio of 1:1 for 24 hours, wash with deionized water until neutral, and finally dry at 120℃ to remove ZnO template and unreacted salts from the product obtained in S2. After drying, the modified coal-based activated carbon adsorbent material is obtained. Example 2
[0035] A modified coal-based activated carbon for VOCs waste gas treatment is prepared using the following steps: S1. First, mix and impregnate the coal powder (anthracite, ash content ≤5%, particle size 80-120 mesh) and the composite modifier obtained in Preparation Example 1 at a weight ratio of 1:4, and stir at a constant temperature of 60℃ for 8 hours. Then, dry and dehydrate at 120℃, and grind to a particle size ≤0.10mm to obtain the coal precursor.
[0036] S2. Then, the coal precursor obtained in S1 is activated in a segmented temperature-controlled manner under a nitrogen atmosphere. The specific process steps and conditions are as follows: the coal precursor obtained in S1 is pre-carbonized at 500℃ for 1 hour, and then the temperature is raised to 800℃ for high-temperature activation for 2 hours.
[0037] S3. Then, soak the product obtained in S2 in 1M HCl solution at a solid-liquid ratio of 1:1 for 24 hours, wash with deionized water until neutral, and finally dry at 120℃ to remove ZnO template and unreacted salts from the product obtained in S2. After drying, the modified coal-based activated carbon adsorbent material is obtained. Example 3
[0038] A modified coal-based activated carbon for VOCs waste gas treatment is prepared using the following steps: S1. First, mix and impregnate the coal powder (anthracite, ash content ≤5%, particle size 80-120 mesh) and the composite modifier obtained in Preparation Example 1 at a weight ratio of 1:5, and stir at a constant temperature of 60℃ for 8 hours. Then, dry and dehydrate at 120℃, and grind to a particle size ≤0.10mm to obtain the coal precursor.
[0039] S2. Then, the coal precursor obtained in S1 is activated in a segmented temperature-controlled manner under a nitrogen atmosphere. The specific process steps and conditions are as follows: the coal precursor obtained in S1 is pre-carbonized at 500℃ for 1 hour, and then the temperature is raised to 800℃ for high-temperature activation for 2 hours.
[0040] S3. Then, soak the product obtained in S2 in 1M HCl solution at a solid-liquid ratio of 1:1 for 24 hours, wash with deionized water until neutral, and finally dry at 120℃ to remove ZnO template and unreacted salts from the product obtained in S2. After drying, the modified coal-based activated carbon adsorbent material is obtained. Example 4
[0041] A modified coal-based activated carbon for VOCs waste gas treatment is prepared using the following steps: S1. First, mix and impregnate the coal powder (anthracite, ash content ≤5%, particle size 80-120 mesh) and the composite modifier obtained in Preparation Example 1 at a weight ratio of 1:6, and stir at a constant temperature of 60℃ for 8 hours. Then, dry and dehydrate at 120℃ and grind to a particle size ≤0.10mm to obtain the coal precursor.
[0042] S2. Then, the coal precursor obtained in S1 is activated in a segmented temperature-controlled manner under a nitrogen atmosphere. The specific process steps and conditions are as follows: the coal precursor obtained in S1 is pre-carbonized at 500℃ for 1 hour, and then the temperature is raised to 800℃ for high-temperature activation for 2 hours.
[0043] S3. Then, soak the product obtained in S2 in 1M HCl solution at a solid-liquid ratio of 1:1 for 24 hours, wash with deionized water until neutral, and finally dry at 120℃ to remove ZnO template and unreacted salts from the product obtained in S2. After drying, the modified coal-based activated carbon adsorbent material is obtained. Example 5
[0044] A modified coal-based activated carbon for VOCs waste gas treatment is prepared using the following steps: S1. First, mix and impregnate the coal powder (anthracite, ash content ≤5%, particle size 80-120 mesh) and the composite modifier obtained in Preparation Example 1 at a weight ratio of 1:10, and stir at a constant temperature of 60℃ for 8 hours. Then, dry and dehydrate at 120℃, and grind to a particle size ≤0.10mm to obtain the coal precursor.
[0045] S2. Then, the coal precursor obtained in S1 is activated in a segmented temperature-controlled manner under a nitrogen atmosphere. The specific process steps and conditions are as follows: the coal precursor obtained in S1 is pre-carbonized at 500℃ for 1 hour, and then the temperature is raised to 800℃ for high-temperature activation for 2 hours.
[0046] S3. Then, soak the product obtained in S2 in 1M HCl solution at a solid-liquid ratio of 1:1 for 24 hours, wash with deionized water until neutral, and finally dry at 120℃ to remove ZnO template and unreacted salts from the product obtained in S2. After drying, the modified coal-based activated carbon adsorbent material is obtained.
[0047] Ten groups of modified coal-based activated carbons for VOCs waste gas treatment prepared in Examples 1-5 were extracted, and their specific surface area, mesopore ratio, total adsorption capacity and acid / alkali resistance were tested respectively. The average value of the test results was recorded in the table below.
[0048] Table: Performance Test Results of Examples 1-5
[0049] As can be seen from the table above, the modified coal-based activated carbons prepared in Examples 1-5 for VOCs waste gas treatment all have excellent microporous structures and adsorption performance, showing varying degrees of improvement compared to the control group using unmodified coal-based activated carbon, as detailed below: Its specific surface area is as high as 1280-1440 m² / g, which is about 100-120% higher than that of the control group; Its mesoporous ratio is as high as 42-49%, which is about 220-250% higher than that of the control group; Its total adsorption capacity reached 1.5-1.7 mg / g, which was approximately 150-180% higher than that of the control group; Its acidity retention rate is as high as 90-95%, which is about 80-86% higher than that of the control group; Its alkalinity retention rate is as high as 86-92%, which is about 110-120% higher than that of the control group; In summary, coal powder that has been impregnated and activated by the composite modifier has a significantly improved pore structure. Furthermore, the doping and introduction of nitrogen and sulfur elements enhances its resistance to acid / alkaline VOCs gases and its chemical adsorption effect. The preferred ratio of coal powder to composite modifier is 1:(4-6).
[0050] The reasons can be deduced by combining various data as follows: 1) The improvement of its pore structure is due to the generation of ZnO template by ZnSO4 under high temperature decomposition, while the carbonization of melamine causes the expansion of the cracked gas to create pores, which in turn synergistically form a microporous-mesoporous hierarchical structure. 2) Its resistance to acidic gases and adsorption effect are mainly due to the introduction of melamine. The nitrogen-containing free radicals (-NH2, -CN) generated by its cracking are easy to combine with the carbon skeleton to form alkaline sites. 3) In addition, the alkaline sites (N doped) formed will also form CSC or C-SOx structures with the residual sulfur elements, i.e. acidic sites, to form amphoteric surfaces, which synergistically endow activated carbon with the effect of adsorbing acidic / alkaline VOCs gases. Therefore, the control group obviously cannot achieve the above effect.
[0051] Examples 6-9 A modified coal-based activated carbon for VOCs waste gas treatment differs from Example 3 in that the modified coal-based activated carbon used is used differently, and the specific correspondence is shown in the table below.
[0052] Table: Comparison of the use of modified coal-based activated carbon in Examples 6-9 Group Modified coal-based activated carbon Example 6 Prepared from Preparation Example 2 Example 7 Prepared from Preparation Example 3 Example 8 Prepared from Preparation Example 4 Example 9 Prepared from Preparation Example 5 Comparative Example 1 A modified coal-based activated carbon is prepared using the following steps: S1. First, mix and impregnate pulverized coal (anthracite, ash content ≤5%, particle size 80-120 mesh) and 20wt% KOH solution at a weight ratio of 1:5, and stir at a constant temperature of 60℃ for 8 hours. Then, dry and dehydrate at 120℃, and grind to a particle size ≤0.10mm to obtain the coal precursor. S2. Then the coal precursor obtained in S1 is activated at 800℃ for 2 hours under a nitrogen atmosphere. S3. Then, soak the product obtained in S2 in 1M HCl solution at a solid-liquid ratio of 1:1 for 24 hours, wash with deionized water until neutral, and finally dry at 120℃ to remove ZnO template and unreacted salts from the product obtained in S2. After drying, the modified coal-based activated carbon adsorbent material is obtained.
[0053] Comparative Example 2 A modified coal-based activated carbon for VOCs waste gas treatment is prepared using the following steps: S1. First, mix and impregnate pulverized coal (anthracite, ash content ≤5%, particle size 80-120 mesh) and 3wt% ZnSO4 aqueous solution at a weight ratio of 1:5, and stir at a constant temperature of 60℃ for 8 hours. Then, dry and dehydrate at 120℃, and grind to a particle size ≤0.10mm to obtain coal precursor. S2. Then, the coal precursor obtained in S1 is activated in a segmented temperature-controlled manner under a nitrogen atmosphere. The specific process steps and conditions are as follows: the coal precursor obtained in S1 is pre-carbonized at 500℃ for 1 hour, and then the temperature is raised to 800℃ for high-temperature activation for 2 hours.
[0054] S3. Then, soak the product obtained in S2 in 1M HCl solution at a solid-liquid ratio of 1:1 for 24 hours, wash with deionized water until neutral, and finally dry at 120℃ to remove ZnO template and unreacted salts from the product obtained in S2. After drying, the modified coal-based activated carbon adsorbent material is obtained.
[0055] Comparative Example 3 A modified coal-based activated carbon for VOCs waste gas treatment is prepared using the following steps: S1. First, mix and impregnate a suspension of 2wt% melamine (solvent-water) with coal powder (anthracite, ash content ≤5%, particle size 80-120 mesh) and 2wt% melamine at a weight ratio of 1:5, and stir at a constant temperature of 60℃ for 8 hours. Then, dry and dehydrate at 120℃ and grind to a particle size ≤0.10mm to obtain a coal precursor. S2. Then, the coal precursor obtained in S1 is activated in a segmented temperature-controlled manner under a nitrogen atmosphere. The specific process steps and conditions are as follows: the coal precursor obtained in S1 is pre-carbonized at 500℃ for 1 hour, and then the temperature is raised to 800℃ for high-temperature activation for 2 hours.
[0056] S3. Then, soak the product obtained in S2 in 1M HCl solution at a solid-liquid ratio of 1:1 for 24 hours, wash with deionized water until neutral, and finally dry at 120℃ to remove ZnO template and unreacted salts from the product obtained in S2. After drying, the modified coal-based activated carbon adsorbent material is obtained.
[0057] Ten groups of modified coal-based activated carbons for VOCs waste gas treatment were extracted from Examples 6-9 and Comparative Examples 1-3, and their specific surface area, mesopore ratio, total adsorption capacity and acid / alkali resistance were tested respectively. The average value of the test results was recorded in the table below.
[0058] Table: Performance test results of Examples 6-9 and Comparative Examples 1-3 As can be seen from the table above, the modified coal-based activated carbons prepared in Examples 6-9 for VOCs waste gas treatment all possess excellent microporous structures and adsorption performance, showing varying degrees of improvement compared to the coal-based activated carbons modified under other conditions in Comparative Examples 1-3. As can be seen from Examples 1 and 6-9, the composite modifier is preferably composed of the following components by weight percentage: 5-8 wt% zinc sulfate, 3-7 wt% melamine, and the remainder being solvent. The performance of Examples 1 and 9, which exceed this range, is slightly reduced. It is speculated that the reason is that the modification is incomplete due to insufficient dosage or that the voids are blocked due to excessive dosage.
[0059] In summary, it can be concluded that Examples 6-8 are preferred embodiments of this application, with a specific surface area as high as 1410-1450 m² / g, a mesoporous ratio as high as 48-50%, a total adsorption amount of 1.6-1.8 mg / g, an acidity retention rate of 95%, and an alkalinity retention rate of 92-93%. Obviously, Comparative Examples 1-3 cannot achieve the corresponding effects. The reasons for this can be analyzed in detail based on the data as follows: In Comparative Example 1, KOH was used for activation, which can improve the surface of coal-based activated carbon. However, it mainly achieves pore formation through alkaline etching at high temperature. Therefore, its specific surface area, mesopore ratio and total adsorption are only slightly improved. Furthermore, due to the lack of support sites, it does not have acid / alkali resistance.
[0060] Comparative Examples 2-3 show that because only one of ZnSO4 and melamine was used, the original synergistic pore-forming effect was lost. Furthermore, due to the change in the mesoporous structure, the doping amount of N / S elements was affected. Even if the corresponding acid / basic sites are present, the corresponding acid / basic resistance is weak. It can be seen that the two need to be used in combination, and the effect of using them alone is far below expectations.
[0061] Example 10 A modified coal-based activated carbon for VOCs waste gas treatment differs from Example 1 in that it is prepared using the following steps: S1. First, mix and impregnate the coal powder (anthracite, ash content ≤5%, particle size 80-120 mesh) and the composite modifier obtained in Preparation Example 1 at a weight ratio of 1:3, and stir at a constant temperature of 60℃ for 8 hours. Then, dry and dehydrate at 120℃, and grind to a particle size ≤0.10 mm to obtain the coal precursor. S2. Then, the coal precursor obtained in S1 is activated in a segmented temperature-controlled manner under a nitrogen atmosphere. The specific process steps and conditions are as follows: the coal precursor obtained in S1 is pre-carbonized at 500℃ for 1 hour, and then the temperature is raised to 600℃ for high-temperature activation for 2 hours.
[0062] S3. Then, soak the product obtained in S2 in 1M HCl solution at a solid-liquid ratio of 1:1 for 24 hours, wash with deionized water until neutral, and finally dry at 120℃ to remove ZnO template and unreacted salts from the product obtained in S2. After drying, the modified coal-based activated carbon adsorbent material is obtained.
[0063] Example 11 A modified coal-based activated carbon for VOCs waste gas treatment differs from Example 1 in that it is prepared using the following steps: S1. First, mix and impregnate the coal powder (anthracite, ash content ≤5%, particle size 80-120 mesh) and the composite modifier obtained in Preparation Example 1 at a weight ratio of 1:3, and stir at a constant temperature of 60℃ for 8 hours. Then, dry and dehydrate at 120℃, and grind to a particle size ≤0.10 mm to obtain the coal precursor. S2. Then, the coal precursor obtained in S1 is activated in a segmented temperature-controlled manner under a nitrogen atmosphere. The specific process steps and conditions are as follows: the coal precursor obtained in S1 is activated at 800℃ for 2 hours.
[0064] S3. Then, soak the product obtained in S2 in 1M HCl solution at a solid-liquid ratio of 1:1 for 24 hours, wash with deionized water until neutral, and finally dry at 120℃ to remove ZnO template and unreacted salts from the product obtained in S2. After drying, the modified coal-based activated carbon adsorbent material is obtained.
[0065] Ten groups of modified coal-based activated carbons for VOCs waste gas treatment prepared in Examples 10-11 above were selected, and their specific surface area, mesopore ratio, total adsorption capacity and acid / alkali resistance were tested respectively. The average value of the test results was recorded in the table below.
[0066] Table: Performance Test Results of Examples 10-11 As can be seen from the table above, the modified coal-based activated carbons prepared in Examples 10-11 for VOCs waste gas treatment all exhibit excellent microporous structure and adsorption performance. Under the same conditions, they all show varying degrees of degradation compared to Example 1, which used segmented activation at corresponding temperatures. Based on the data, it can be seen that both insufficient high-temperature activation temperature (600℃ - Example 10) and omission of pre-carbonization (Example 11) will affect the pore-forming efficiency, which in turn will affect the total adsorption and acid / alkali resistance. The preferred activation conditions are: first pre-carbonize the coal precursor obtained in S1 at 400-500℃ for 1-2 hours, and then raise the temperature to 700-800℃ for 2-3 hours of high-temperature activation.
[0067] The preparation method of modified coal-based activated carbon in this application is only based on typical examples 1, 10 and 11. Within the preferred range, those skilled in the art can change to other operating conditions according to actual operation, and the changes in various properties can be expected. Therefore, it will not be elaborated. As for the selection of reagents and conditions in the acid washing process, they can also be replaced or discarded according to the expected effect.
[0068] The above are all modifications that can be made to this embodiment without contributing any inventive step, or solutions that clearly constitute technical teaching, after reading this specification. However, as long as they are within the scope of the claims of this application, they should be protected by patent law.
Claims
1. A modified coal-based activated carbon for VOCs waste gas treatment, characterized in that, The modified coal-based activated carbon is prepared by impregnating coal powder with a composite modifier and then activating it. The composite modifier is composed of zinc sulfate, melamine and a solvent.
2. The modified coal-based activated carbon for VOCs waste gas treatment according to claim 1, characterized in that, The composite modifier is composed of the following components by weight percentage: 5-8 wt% zinc sulfate, 3-7 wt% melamine, and the balance being solvent.
3. The modified coal-based activated carbon for VOCs waste gas treatment according to claim 2, characterized in that, The ratio of coal powder to composite modifier is 1:(4-6).
4. The modified coal-based activated carbon for VOCs waste gas treatment according to claim 1, characterized in that, The pulverized coal is anthracite with an ash content of ≤5% and a particle size of 80-120 mesh.
5. The modified coal-based activated carbon for VOCs waste gas treatment according to claim 3, characterized in that, The activation is a segmented temperature-controlled activation.
6. The method for preparing modified coal-based activated carbon for VOCs waste gas treatment according to any one of claims 1-5, characterized in that, The steps are as follows: S1. First, mix and impregnate the coal powder and composite modifier according to the corresponding weight ratio, and stir at a constant temperature of 60℃ for 6-8 hours. Then, dry and dehydrate the mixture, and grind it to a particle size of ≤0.10mm to obtain the coal precursor. S2. Then, the coal precursor obtained in S1 is activated in a segmented temperature-controlled atmosphere under nitrogen. S3, then acid washing and water washing are performed sequentially to remove the ZnO template and unreacted salts from the product obtained in S2. After drying, modified coal-based activated carbon is obtained.
7. The method for preparing modified coal-based activated carbon for VOCs waste gas treatment according to claim 6, characterized in that, The specific process of segmented temperature-controlled activation in S2 is as follows: That is, the coal precursor obtained in S1 is first pre-carbonized at 400-500℃ for 1-2 hours, and then the temperature is raised to 700-800℃ for further high-temperature activation for 2-3 hours.
8. The method for preparing modified coal-based activated carbon for VOCs waste gas treatment according to claim 6, characterized in that, The pickling and washing processes in S3 are as follows: First, soak the product obtained in S2 in 1-2M HCl solution at a solid-liquid ratio of 1:(1-3) for 12-24 hours, then wash with deionized water until neutral, and finally dry at 100-120℃ to remove water.
9. The application of the modified coal-based activated carbon for VOCs waste gas treatment according to any one of claims 1-5, characterized in that: Suitable for treating industrial VOCs waste gas with high humidity and complex composition, and resistant to acidic gases with a long effective service life.
10. A composite modifier for modifying activated carbon adsorbent materials, characterized in that, It consists of the following components by weight percentage: zinc sulfate 5-8 wt%, melamine 3-7 wt%, and solvent as the balance.