Microporous activated carbon and its use in flue gas purification

Abstract

The present application relates to the field of adsorbing material preparation, and particularly discloses a microporous activated carbon and its application in flue gas purification, wherein coal and zinc oxide aqueous solution are mixed and reacted, an ultrasonic bubble reaction is adopted to remove zinc oxide and form micropores by means of a complex solution, ultraviolet irradiation is used to promote the polymerization and reduction of alcohol acid solution in the activated carbon, and finally, the activated carbon is dispersed in an organic solution and subjected to surface modification by pressure and heating; the prepared activated carbon has a high proportion of micropores, high surface activity, high adsorption of organic matters and high removal rate, and overcomes the technical problem that the existing activated carbon is difficult to remove polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran.

Description

Technical Field

[0001] This invention relates to the field of adsorption material preparation, specifically to a microporous activated carbon and its application in flue gas purification. Background Technology

[0002] Currently, the widespread application of municipal solid waste incineration technology and the continued prevalence of industrial smelting produce extremely harmful flue gas containing various toxic and harmful gases. Direct emission of these gases not only causes environmental pollution but also harms human and biological health, with long-lasting effects. For example, dioxins, acidic gases such as sulfur dioxide, and nitrogen oxides are highly toxic gases that are easily produced in large quantities after waste incineration. These gases are classified as Group 1 carcinogens and possess characteristics such as low water solubility, low vapor pressure, and high octanol / water partition coefficient. They are easily soluble in organic matter, thus easily polluting the soil and being absorbed and utilized by organisms. They also have good chemical and thermal stability, a long half-life, are difficult to degrade, and are persistent. They easily accumulate in human adipose tissue, inducing multiple cancers and other physical ailments by affecting cell regeneration and apoptosis.

[0003] Currently, activated carbon is widely used in waste gas adsorption and purification processes due to its advantages of low cost, low energy consumption, high stability, and fast reaction. However, it also has some drawbacks. Activated carbon adsorbs substances by contacting them with organic matter, thus fixing the substances at the adsorption points. Therefore, its adsorption capacity is limited, and it is prone to saturation. It also has high consumption and limited adsorption capacity. When adsorbing mixed gases, some gases are difficult to remove, such as dioxins, a group of chlorinated aromatic hydrocarbons, including chlorinated dibenzo-dioxins, polychlorinated dibenzofurans, and polychlorinated biphenyls. Among them, polychlorinated dibenzo-dioxins and polychlorinated dibenzofurans are the most difficult to remove. Furthermore, the adsorption capacity of activated carbon tends to weaken with repeated use. Therefore, activated carbon with high microporosity and high adsorption rate has a promising market prospect. Summary of the Invention

[0004] To address the above problems, the present invention aims to provide a microporous activated carbon and its application in flue gas purification.

[0005] The technical content of this invention is as follows:

[0006] This invention provides a method for preparing microporous activated carbon, comprising the following steps:

[0007] Step 1: Anthracite, lignite, a 40-50% nano zinc oxide aqueous solution and coal tar are mixed in a mass ratio of 11-13:1-3:3-5:1-3. The mixture is heated under nitrogen, kept at a constant temperature for 20-30 minutes, cooled to room temperature, extruded and dried to form mixed particles with a particle size of 2.5-5 mm.

[0008] The heating reaction is to raise the temperature to 200-300℃ at a rate of 15-20℃ / min.

[0009] Step 2: The mixed particles are subjected to a porosity-reducing treatment to obtain porous mixed particles, and then a reduction reaction is carried out;

[0010] The porous treatment involves immersing the mixed particles in a complexing solution at a solid-liquid ratio of 2:9-11 g / mL, sonicating at a temperature of -5 to 5℃ for 40-50 min, and then filtering and drying.

[0011] The complexing solution is composed of sodium carbonate and sodium phenoxide mixed in a mass ratio of 11-13:3-5 and then added to water at a volume ratio of 6-10.

[0012] The frequency of the ultrasound is 40-60KHz;

[0013] The porous treatment uses ultrasonic physical energy to create microbubbles, which cause different degrees of reaction in the complexing solution, thereby forming activated carbon with a pore size of 2-5 nm. It also removes nano zinc oxide by dissolving, thus forming micropores. At the same time, nano zinc oxide has a certain adsorption and decontamination effect.

[0014] The reduction reaction involves spraying porous mixed particles with an alkyd solution followed by ultraviolet light irradiation.

[0015] The wavelength of the ultraviolet irradiation is 300-380nm;

[0016] The alkyd solution is composed of diethylene glycol and citric acid in a mass ratio of 15-18:5-7.

[0017] The reduction reaction promotes the polymerization and grafting reaction of the alkyd solution in the porous mixed particles by light irradiation, and reduces the oxides, thereby improving the chemical reactivity of activated carbon.

[0018] Step 3: Finally, disperse the mixture in an organic solution, pressurize and heat it, then cool and dry it to obtain the final product;

[0019] The organic solution is polyvinylpyrrolidone;

[0020] The pressure for pressurized heating is 0.2-0.4 MPa, the temperature is 40-60℃, and the time is 30-40 min;

[0021] The nitrogen groups in the structure of the organic solvent can undergo diazo coupling reactions with aromatic organic compounds, thereby increasing the adsorption capacity of activated carbon for organic compounds.

[0022] The present invention also provides microporous activated carbon obtained by the above preparation method.

[0023] The present invention also provides the application of the microporous activated carbon in flue gas purification.

[0024] The beneficial effects of the present invention are as follows: The present invention provides a method for preparing microporous activated carbon, which involves mixing coal raw material with nano zinc oxide aqueous solution to form a pore, then using ultrasonic bubble reaction to compound complex solution for pore-reducing treatment to remove zinc oxide and form micropores at the same time, then using ultraviolet irradiation to promote the polymerization and reduction of alkyd solution in activated carbon, and finally dispersing it in an organic solution for surface modification under pressure and heating. The resulting activated carbon particles are small and have a high content of micropores with a pore size distribution of 2-4 mm.

[0025] The present invention also provides the application of the prepared microporous activated carbon in flue gas purification. The prepared microporous activated carbon has the characteristics of high micropore content and uniform pore distribution. When applied in flue gas purification process, it has strong adsorption capacity and can adsorb organic matter that is difficult to remove. Its adsorption capacity does not decrease with the number of adsorption cycles. Detailed Implementation

[0026] The present invention will be further described in detail below through specific implementation examples. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of protection of the present invention. After reading the present invention, any modifications of the present invention in various equivalent forms by those skilled in the art fall within the scope of the appended claims.

[0027] Unless otherwise specified, all raw materials and reagents used in this invention are from the conventional market.

[0028] Example 1

[0029] A method for preparing microporous activated carbon includes the following steps:

[0030] Step 1: Anthracite, lignite, 45% nano zinc oxide aqueous solution and coal tar are mixed in a mass ratio of 12:2:4:2. The mixture is heated under nitrogen atmosphere to 250°C at a rate of 18°C / min, held at the temperature for 25 min and then cooled to room temperature. After extrusion molding and drying, mixed particles with a particle size of 3.5 mm are formed.

[0031] Step 2: The mixed particles were immersed in a complex solution containing a mixture of sodium carbonate and sodium phenolate in a mass ratio of 12:4 and then added to water at a volume ratio of 7. The mixture was sonicated at 50 kHz for 45 min at 0 ℃, filtered and dried. The porous mixed particles were then sprayed with an alkyd solution composed of diethylene glycol and citric acid in a mass ratio of 16:6 and then subjected to 340 nm ultraviolet light irradiation for reduction reaction.

[0032] Step 3: Finally, disperse the carbon in polyvinylpyrrolidone, pressurize and heat it, then cool and dry it to obtain microporous activated carbon;

[0033] The pressure for pressurization heating is 0.3 MPa, the temperature is 50°C, and the time is 35 min.

[0034] Example 2

[0035] A method for preparing microporous activated carbon includes the following steps:

[0036] Step 1: Anthracite, lignite, 40% nano zinc oxide aqueous solution and coal tar are mixed in a mass ratio of 11:1:3:1. The mixture is heated under nitrogen atmosphere at a rate of 15℃ / min to 200℃, held at that temperature for 20 min and then cooled to room temperature. After extrusion molding and drying, mixed particles with a particle size of 2.5 mm are formed.

[0037] Step 2: The mixed granules were immersed in a complex solution obtained by immersing the granules in a mixture of sodium carbonate and sodium phenolate in a mass ratio of 11:3 at a solid-liquid ratio of 2:9 g / mL and then adding 6 times the volume of water. The mixture was then sonicated at 40 kHz for 40 min at -5℃, filtered and dried to obtain porous mixed granules. The porous mixed granules were then sprayed with an alkyd solution composed of diethylene glycol and citric acid in a mass ratio of 15:5 and then irradiated with ultraviolet light at a wavelength of 300 nm to carry out a reduction reaction.

[0038] Step 3: Finally, disperse the carbon in polyvinylpyrrolidone, pressurize and heat it, then cool and dry it to obtain microporous activated carbon;

[0039] The pressure for pressurization heating is 0.2 MPa, the temperature is 40°C, and the time is 30 min.

[0040] Example 3

[0041] A method for preparing microporous activated carbon includes the following steps:

[0042] Step 1: Anthracite, lignite, 50% nano zinc oxide aqueous solution and coal tar are mixed in a mass ratio of 13:3:5:3. The mixture is heated under nitrogen atmosphere to 300℃ at a rate of 20℃ / min, then kept at the temperature for 30 min and cooled to room temperature. After extrusion molding and drying, mixed particles with a particle size of 5mm are formed.

[0043] Step 2: The mixed granules were immersed in a complex solution obtained by mixing sodium carbonate and sodium phenolate in a mass ratio of 13:5 and then adding 10 times the volume of water at a solid-liquid ratio of 2:11 g / mL. The mixture was then sonicated at 60 kHz for 50 min at 5℃, filtered and dried to obtain porous mixed granules. The porous mixed granules were then sprayed with an alkyd solution composed of diethylene glycol and citric acid in a mass ratio of 18:7 and then irradiated with ultraviolet light at a wavelength of 380 nm to carry out a reduction reaction.

[0044] Step 3: Finally, disperse the carbon in polyvinylpyrrolidone, pressurize and heat it, then cool and dry it to obtain microporous activated carbon;

[0045] The pressure for pressurization heating is 0.4 MPa, the temperature is 60°C, and the time is 40 min.

[0046] Example 4

[0047] A method for preparing microporous activated carbon includes the following steps:

[0048] Step 1: Anthracite, lignite, 43% nano zinc oxide aqueous solution and coal tar are mixed in a mass ratio of 13:1:5:2. The mixture is heated to 200°C at a rate of 20°C / min under nitrogen atmosphere, then kept at the temperature for 20 min and cooled to room temperature. After extrusion molding and drying, mixed particles with a particle size of 3 mm are formed.

[0049] Step 2: The mixed granules were immersed in a complex solution obtained by immersing the granules in a mixture of sodium carbonate and sodium phenolate in a mass ratio of 11:5 at a solid-liquid ratio of 2:9 g / mL and then adding 8 times the volume of water. The mixture was then sonicated at 40 kHz for 40 min at 5℃, filtered and dried to obtain porous mixed granules. The porous mixed granules were then sprayed with an alkyd solution composed of diethylene glycol and citric acid in a mass ratio of 15:7 and then irradiated with ultraviolet light at a wavelength of 380 nm to carry out a reduction reaction.

[0050] Step 3: Finally, disperse the carbon in polyvinylpyrrolidone, pressurize and heat it, then cool and dry it to obtain microporous activated carbon;

[0051] The pressure for pressurization heating is 0.2 MPa, the temperature is 60°C, and the time is 30 min.

[0052] Example 5

[0053] A method for preparing microporous activated carbon includes the following steps:

[0054] Step 1: Anthracite, lignite, a 47% nano zinc oxide aqueous solution and coal tar are mixed in a mass ratio of 11:3:3:1. The mixture is heated under nitrogen atmosphere to 300°C at a rate of 15°C / min, held at that temperature for 30 min, and then cooled to room temperature. After extrusion molding and drying, mixed particles with a particle size of 4 mm are formed.

[0055] Step 2: The mixed granules were immersed in a complex solution obtained by immersing the granules in a mixture of sodium carbonate and sodium phenolate in a mass ratio of 11:5 at a solid-liquid ratio of 2:11 g / mL and then adding 7 times the volume of water. The mixture was then sonicated at 40 kHz for 50 min at -5℃, filtered and dried to obtain porous mixed granules. The porous mixed granules were then sprayed with an alkyd solution composed of diethylene glycol and citric acid in a mass ratio of 15:5 and then irradiated with ultraviolet light at a wavelength of 380 nm to carry out a reduction reaction.

[0056] Step 3: Finally, disperse the carbon in polyvinylpyrrolidone, pressurize and heat it, then cool and dry it to obtain microporous activated carbon;

[0057] The pressure for pressurization heating is 0.2 MPa, the temperature is 60°C, and the time is 30 min.

[0058] Example 6

[0059] A method for preparing microporous activated carbon includes the following steps:

[0060] Step 1: Anthracite, lignite, 40% nano zinc oxide aqueous solution and coal tar are mixed in a mass ratio of 12:2:3:1. The mixture is heated under nitrogen atmosphere to 220°C at a rate of 16°C / min, held at the temperature for 30 min and then cooled to room temperature. After extrusion molding and drying, mixed particles with a particle size of 4.5 mm are formed.

[0061] Step 2: The mixed granules were immersed in a complex solution obtained by immersing the granules in a mixture of sodium carbonate and sodium phenolate at a solid-liquid ratio of 2:10 g / mL and then adding the mixture to water at a mass ratio of 9:10. The mixture was then sonicated at 42 kHz for 40 min at -2℃, filtered and dried to obtain porous mixed granules. The porous mixed granules were then sprayed with an alkyd solution composed of diethylene glycol and citric acid at a mass ratio of 18:6 and then irradiated with ultraviolet light at a wavelength of 320 nm to carry out a reduction reaction.

[0062] Step 3: Finally, disperse the carbon in polyvinylpyrrolidone, pressurize and heat it, then cool and dry it to obtain microporous activated carbon;

[0063] The pressure for pressurization heating is 0.3 MPa, the temperature is 42°C, and the time is 32 min.

[0064] Comparative Example 1

[0065] The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 does not undergo porosity treatment.

[0066] Comparative Example 2

[0067] The difference between Comparative Example 2 and Example 1 is that the low-temperature ultrasonic treatment was not performed in the porous treatment of Comparative Example 2. Instead, the mixed particles were directly immersed in the complexing solution at room temperature (25°C) with a solid-liquid ratio of 2:9-11 g / mL for 45 min.

[0068] Comparative Example 3

[0069] The difference between Comparative Example 3 and Example 1 is that the reduction reaction in Comparative Example 3 is not mixed with the alcoholic acid solution.

[0070] I. Activated Carbon Performance

[0071] The activated carbon prepared in the examples and comparative examples was characterized. The specific surface area and pore size distribution were measured. The iodine value, methylene blue adsorption value, desulfurization value and denitrification rate were tested. The iodine value was determined according to the national standard GB / T7702.15-1987, the methylene blue adsorption value was determined according to the national standard GB / T 7702.6-2008, the desulfurization value was determined according to the national standard GB / T30202.4-2013, and the denitrification rate was determined according to the national standard GB / T 35254-2017. The test results are shown in Table 1.

[0072] Table 1 Performance of Activated Carbon

[0073]

[0074] As shown in Table 1, the activated carbon prepared by this invention has a large specific surface area, a high micropore content in the pore size range of 2-5 nm (up to 48.3%), and also has a high iodine value, a high methylene blue adsorption value, and strong desulfurization and denitrification capabilities.

[0075] II. Adsorption Performance Test of Activated Carbon on Waste Incineration Flue Gas

[0076] Municipal solid waste was incinerated in a confined space. Activated carbon prepared in the examples and comparative examples was added to the flue gas generated. The concentration changes of dioxins, polychlorinated dibenzo-p-dioxins, and polychlorinated dibenzofurans were tested, and the adsorption efficiency of the activated carbon was obtained. The results are shown in Table 2.

[0077] Table 2 Dioxin Removal Rate

[0078]

[0079]

[0080] As shown in Table 2, the activated carbon prepared by this invention has a high removal rate of dioxins, and can also basically remove polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans, which are difficult to remove.

[0081] III. Adsorption Performance Test of Activated Carbon for Industrial Flue Gas

[0082] The test results are shown in Table 3.

[0083] Table 3 Removal rates of inorganic and organic substances

[0084]

[0085] As shown in Table 3, the activated carbon prepared by this invention has a high adsorption capacity for organic and inorganic substances in the adsorption test of industrial flue gas, with a removal rate of over 97%.

[0086] Compared with the prior art, the method for preparing activated carbon for removing dioxins provided by the present invention can form micropores by first incorporating and then removing nano zinc oxide and loading it with nano zinc oxide. The pore-reducing treatment is controlled by the microbubbles formed by ultrasound to regulate the reaction of the complexing solution, thereby forming pores concentrated in the micropores. The organic solution is pressurized, heated and reduced, which can enhance the strength and adsorption performance of the activated carbon and is suitable for various flue gas treatments.

Claims

1. A method for preparing microporous activated carbon, characterized in that, Includes the following steps: Step 1: Anthracite, lignite, a 40-50% nano zinc oxide aqueous solution and coal tar are mixed in a mass ratio of 11-13:1-3:3-5:1-3. The mixture is heated under nitrogen atmosphere at a rate of 15-20℃ / min to 200-300℃, then kept at the temperature for 20-30 min and cooled to room temperature. After extrusion molding and drying, mixed particles with a particle size of 2.5-5mm are formed. Step 2: The mixed particles are subjected to a porosity-reducing treatment to obtain porous mixed particles, and then a reduction reaction is carried out; The porous treatment involves immersing the mixed particles in a complexing solution at a solid-liquid ratio of 2:9-11 g / mL, sonicating at a temperature of -5-5℃ for 40-50 min, and then filtering and drying. The complexing solution is prepared by mixing sodium carbonate and sodium phenolate in a mass ratio of 11-13:3-5 and then adding 6-10 times the volume of water. The frequency of the ultrasound is 40-60 kHz. The reduction reaction involves spraying porous mixed particles with an alkyd solution followed by ultraviolet irradiation, wherein the wavelength of the ultraviolet irradiation is 300-380 nm. The alkyd solution is composed of diethylene glycol and citric acid in a mass ratio of 15-18:5-7; Step 3: Finally, disperse the mixture in an organic solution, pressurize and heat it, then cool and dry it to obtain the final product.

2. The method for preparing microporous activated carbon according to claim 1, characterized in that, The organic solution is polyvinylpyrrolidone.

3. The method for preparing microporous activated carbon according to claim 1, characterized in that, The pressure for pressurization heating is 0.2-0.4 MPa, the temperature is 40-60℃, and the time is 30-40 min.

4. A method according to any one of claims 1-3 yields microporous activated carbon.

5. The application of the microporous activated carbon according to claim 4 in flue gas purification.

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