CN112645324B - Porous carbon composite material with core-shell structure and preparation method and application thereof - Google Patents
Porous carbon composite material with core-shell structure and preparation method and application thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/30—Active carbon
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- C01B32/342—Preparation characterised by non-gaseous activating agents
- C01B32/348—Metallic compounds
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/30—Active carbon
- C01B32/312—Preparation
- C01B32/318—Preparation characterised by the starting materials
- C01B32/324—Preparation characterised by the starting materials from waste materials, e.g. tyres or spent sulfite pulp liquor
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/30—Active carbon
- C01B32/312—Preparation
- C01B32/318—Preparation characterised by the starting materials
- C01B32/33—Preparation characterised by the starting materials from distillation residues of coal or petroleum; from petroleum acid sludge
Abstract
The invention provides a porous carbon composite material with a core-shell structure, which comprises porous carbon particles and an inorganic porous layer coating the porous carbon particles. The invention also provides a preparation method of the porous carbon composite material, which comprises the steps of activation treatment, coating formation and carbonization treatment, wherein the coating formation step comprises the steps of firstly providing a coating solution, wherein the coating solution comprises an inorganic layer precursor and a pore-forming agent which are uniformly mixed, and then forming an inorganic gel coating on the surface of the tobacco activated particles. In the carbonization treatment process, the inorganic gel layer is changed into the inorganic porous layer, and meanwhile, nicotine escaping from the tobacco material is bound before the inorganic porous layer is formed, so that the provided microenvironment promotes the carbonization of the nicotine, and the utilization rate of endogenous nitrogen elements and the yield of carbon products in the preparation process of the tobacco-based carbon material are effectively improved. The invention also provides application of the porous carbon composite material in cigarette filters, soil conditioners, water treatment adsorbents or electrodes.
Description
Technical Field
The invention relates to recycling of tobacco waste, in particular to a porous carbon composite material with a core-shell structure and a preparation method and application thereof.
Background
China is a world tobacco big country, and the planting area, the total output, the cigarette output and the sales volume of China all live at the top of the world. The tobacco leaves and the processing process inevitably generate a large amount of waste, and the statistics shows that the tobacco stems generated in 2015 year only reach 1.163 multiplied by 10 6 Ton. Because the availability of the tobacco stalks is relatively poor, most of the tobacco stalks are treated in a burying disposal or burning mode, the comprehensive utilization rate is extremely low, not only is the environmental pollution caused, but also a large amount of existing resources are wasted.
The activated carbon is a porous solid carbon material, and has a developed void structure and a large specific surface area, so that the activated carbon is endowed with unique strong adsorption performance, and has stable chemical properties and is insoluble in water and most other solvents, so that the activated carbon is widely applied to the fields of adsorption, separation, catalysis and the like. Researches show that the binary composite filter stick prepared from the activated carbon and the cellulose acetate fiber according to a certain proportion has obvious effect on selectively reducing cigarette tar, benzopyrene, carbonyl compounds and the like, so that the preparation of the novel functional activated carbon has very important significance on reducing tar and harm of cigarettes.
The preparation of the tobacco-based porous carbon is mainly based on the thermal conversion process of raw materials and is divided into a direct carbonization method and a physical/chemical activation method according to whether an additional activator participates. The direct carbonization method (hydrothermal method) is the most traditional method for preparing the biochar, the process is relatively simple, the carbon material prepared by the method is usually incomplete in pyrolysis of raw materials, pore channels mainly comprise micropores and macropores, pores are not developed, the specific surface area is relatively low, and the carbon material is usually used as a soil conditioner. The activation method is a common method for preparing porous carbon with high specific surface area and high porosity, and is used for contacting a plant precursor or a carbonized material with an activating agent in a high-temperature inert atmosphere and carrying out chemical reaction to achieve the purpose of pore forming. Two methods, physical activation and chemical activation, are mainly included depending on the kind of the activator or the activation mechanism.
The physical activation process generally comprises two steps: firstly, directly carbonizing a biomass raw material, and then adopting H under a high-temperature condition 2 O、CO 2 Or O 2 And etching the carbonized material by using the oxidizing gas to further enlarge the pore diameter and increase the specific surface area. In the comprehensive utilization of tobacco stems, people who deal with summer flood and the like respectively adopt carbon dioxide and water vapor activation methods to prepare microporous tobacco stem base granular activated carbon. The carbon material prepared by the method has relatively low BET specific surface area, most of pores belong to micropores, and the contents of mesopores and macropores are very low. The chemical activation method comprises adding strong base, strong acid or strong oxidant chemical agent such as HNO to the raw material in the activation stage 3 、KOH、MnO 2 、ZnCl 2 And the like. Therefore, compared with a direct carbonization method and a physical activation method, the specific surface area and the porosity of the chemically activated porous carbon are more developed. However, a large number of high cost activators are used in the chemical activation step, and most activators are quite problematic in terms of corrosion of equipment at high temperatures.
In the preparation strategy of nitrogen doping, according to different nitrogen sources, the preparation method of the nitrogen-doped porous carbon mainly comprises two steps of pyrolyzing a nitrogen-containing precursor or carbonizing by means of an external nitrogen-containing reagent. For biomass with poor nitrogen elements, exogenous nitrogen-containing chemicals such as ammonia gas, urea, melamine, polypyrrole and other reagents are introduced in a carbonization or activation stage, and the purpose of introducing the nitrogen elements is achieved by means of the reaction of the nitrogen-containing reagents and oxygen-containing functional groups on the surface of a carbon material. In order to improve the nitrogen content of the tobacco stalk carbon, ma and the like also make a preliminary attempt by adopting an exogenous method, firstly, the tobacco stalks are mixed with ethylene diamine for hydrothermal carbonization, and then activated at high temperature to prepare an O, N-double-doped carbon material, but the N content is reduced rapidly along with the increase of the activation temperature, namely 5.22% at 500 ℃, and only 1.8% when the activation temperature is increased to 800 ℃ (Applied Surface Science 459 (2018) 657-664.). Xiong et al, used for preparing nitrogen-doped poly-element used for super capacitor by using cigarette butts as raw materialThe preparation method of the porous carbon material comprises immersing cigarette butts in acetonitrile solution, adding pyrrole, and adding FeCl 3 Polymerizing pyrrole, then carrying out ultrasonic treatment at 4 ℃ and maintaining the temperature at 4 ℃ for 10 hours, cleaning to obtain a cigarette butt/polypyrrole composite material, and drying; the dried cigarette butt/polypyrrole composite material is uniformly mixed with KOH and then carbonized at 800 ℃ to obtain the nitrogen-doped multi-stage porous carbon material, wherein the nitrogen element is derived from polypyrrole, and the nitrogen content can be 2.34% (Journal of the Taiwan Institute of Chemical Engineers 95 (2019) 315-323).
In addition, when the preparation is carried out by an external method, a new chemical reagent needs to be introduced into a reaction system (high-temperature liquid phase or gas phase), so that not only is higher requirement on materials of preparation equipment put forward, but also the treatment cost of tail gas or leacheate is increased. Compared with an exogenous method, the method has the advantages that the influence on the preparation link is undoubtedly minimum by means of the chemical composition of the precursor, and the method is most economical. The tobacco resources such as tobacco stems and the like are rich in nitrogen elements and mainly exist in nicotine, and the method has natural advantages in the aspect of preparing nitrogen-rich carbon material pseudocapacitors. However, carbon materials prepared by The method have low nitrogen content generally until now, mainly because The boiling point of nicotine is low (247 ℃), the existing direct carbonization, physical activation and self-activation methods have a large amount of nicotine overflow in The Thermal conversion process, and most of nicotine can migrate out of tobacco matrix, such as under The hydrothermal condition of 150 ℃ to 160 ℃ (The Journal of Supercritical Fluids, 153 (2019) 104593.), the temperature of less than 250 ℃ in The gas-solid system (Journal of Renewable and sustaineble Energy, 8 (2016) 013112, journal of Thermal Analysis Calorimeter, 136 (2018) 783-794 Energy & Fuels, 30 (2016) 9-1588; applied Engineering, 106 (2016) Thermal Analysis and 479, journal of 15780. At present, the randomness of the nitrogen content of carbon materials prepared from tobacco is large, and the endogenous nitrogen, especially volatile endogenous nitrogen, can be controllably utilized in plant precursors in various preparation methods of the carbon materials, so that no literature report or patent application exists; meanwhile, porous carbon materials having a core-shell structure are relatively rare.
Disclosure of Invention
In view of the above, the present invention provides a porous carbon composite material with a core-shell structure, and a preparation method and an application thereof, so as to overcome the above problems.
Therefore, the technical scheme provided by the invention is as follows: a porous carbon composite material with a core-shell structure comprises porous carbon particles and an inorganic porous layer coating the porous carbon particles.
Based on the above, the porous carbon particles are step nitrogen-containing porous carbon particles, and the particle size is 20 to 200 meshes.
Based on the above, the inorganic porous layer has a thickness of 200 nm or less, and includes a plurality of micropores having a pore diameter of 0.3 to 2 nm. Preferably, the inorganic porous layer has a thickness of 30 to 150 nm.
Based on the above, the inorganic porous layer is a porous silica layer, a porous titania layer, a porous aluminosilicate layer, a porous silicoaluminophosphate layer, a porous aluminosilicate doped material layer or a porous silicoaluminophosphate doped material layer.
The invention also provides a preparation method of the porous carbon composite material with the core-shell structure, which comprises the following steps:
activating to provide an activating solution, wherein the activating solution comprises an activating agent with the mass fraction of 1-20%; firstly, dipping tobacco particle raw materials into the activating solution, and then carrying out drying treatment to enable the tobacco particle raw materials to load the activating agent to obtain tobacco activated particles;
forming a coating layer to provide a coating solution, wherein the coating solution comprises an inorganic layer precursor and a pore-forming agent which are uniformly mixed; dripping the coating solution into the tobacco activated particles, and then drying at 30-100 ℃ to obtain inorganic layer gel coated tobacco particles, wherein the inorganic layer gel coated tobacco particles comprise the tobacco activated particles and inorganic gel coating layers coated on the surfaces of the tobacco activated particles, and the inorganic gel coating layers are composed of mixed inorganic gel materials and pore-forming agents;
and carbonizing the inorganic layer gel-coated tobacco particles to obtain the porous carbon composite material with the core-shell structure.
Based on the above, the preparation method of the tobacco particle raw material comprises the following steps: and cleaning, drying and crushing the tobacco material to obtain the tobacco particle raw material. Specifically, the tobacco material is cleaned, then dried at 50-120 ℃ until the moisture content is below 10%, and then ground to obtain the tobacco particle raw material, wherein the particle size of the tobacco particle raw material is below 200 meshes. Wherein, the tobacco particle raw material is preferably 20-150 meshes. The tobacco particle raw material is irregular strip-shaped or spherical and can be screened into a uniform size. The tobacco material is a tobacco-based material, a cigarette material or any combination of the two, wherein the tobacco-based material is tobacco leaves, tobacco stems, tobacco stalks or any combination of the tobacco leaves, the tobacco stems and the cigarette material can be cigarette butts.
Based on the above, in the step of activating treatment, the loading amount of the activating agent on the tobacco particle raw material is 0.5-20% of the mass of the tobacco particle raw material. The loading of the activator is preferably 4% to 12%, such as 5%, 10%, etc.
Based on the above, the activating agent is KOH or ZnCl 2 、H 3 PO 4 Or MnO 2 。
Based on the above, the step of forming the clad layer includes: providing the coating solution, wherein the volume concentration of the inorganic layer precursor is 5-10%; dropping the coating solution into the tobacco activated particles for isovolumetric impregnation, and then forming the inorganic gel coating layer on the surface of the tobacco activated particles; and then drying at 30-100 ℃ to obtain the inorganic layer gel-coated tobacco particles.
Wherein the thickness of the inorganic gel coating layer may be adjusted by adjusting the concentration of the inorganic layer precursor or the number of times of performing the step of forming the coating layer according to actual conditions. Therefore, preferably, the above method for preparing a porous carbon composite material having a core-shell structure further includes repeating the step of forming the coating layer a plurality of times.
The main purpose of the coating layer forming step is to reduce or avoid the escape of nicotine in the tobacco material during the subsequent carbonization treatment, thereby improving the utilization rate of nitrogen element in nicotine. The forming principle of the coating layer is as follows: and forming an inorganic gel coating layer on the surface of the tobacco activated particles by hydrolyzing the inorganic layer precursor by means of the activation solution or air moisture.
In the subsequent carbonization treatment process of the inorganic gel coating layer, the inorganic gel material in the inorganic gel coating layer can be dehydrated to form inorganic oxide, and when the thickness of the inorganic gel coating layer is smaller than 10 nm, the inorganic gel coating layer is easily broken by gas formed inside the inorganic gel coating layer in the subsequent carbonization process, so that a large amount of nicotine overflows from the inorganic gel coating layer, the utilization of nitrogen elements in the nicotine is influenced, the nitrogen content in the porous carbon particles is also reduced, and the uncontrollable property of the nitrogen content in the porous carbon particles is also increased. During carbonization, after the inorganic gel material in the inorganic gel coating layer loses water, the pore-forming agent therein decomposes to transform the inorganic gel coating layer into an inorganic porous layer. If the thickness of the inorganic gel coating layer is relatively thick, the difficulty of the subsequent decomposition of the pore-forming agent is increased, the formation of pores on the inorganic porous layer is affected, and the contact property of the porous carbon material of the inner layer is affected, so that the thickness of the inorganic gel coating layer is preferably not more than 200 nm. Therefore, the thickness of the inorganic gel coating layer is preferably 10 to 200 nm, and more preferably 30 to 150 nm.
Based on the above, the inorganic layer precursor is a silicon source material, and the coating solution includes SiCl 4 Ether solution of (a), ethanol solution of organosilane or water glass. Wherein the organosilane is methyl orthosilicate, ethyl orthosilicate or the like.
Based on the above, the pore-forming agent is organic ammonium, and the molar ratio of the organic ammonium to the porous silica layer is 0.5-6: 1.
Based on the above, the carbonizing step includes: and transferring the inorganic layer gel-coated tobacco particles into a container, heating to 550-900 ℃, and maintaining for 0.5-6 h, preferably 1-3 h to obtain the porous carbon composite material with the core-shell structure.
In the process of carbonizing the inorganic layer gel-coated tobacco particles, the inorganic gel coating layer generates inorganic oxide substances due to the dehydration of an inorganic gel material, and the pore-forming agent is decomposed to form pores, so that the conversion of the inorganic gel coating layer to the inorganic porous layer is completed; meanwhile, the tobacco material particles shrink, a carbon source in the tobacco material particles is carbonized to form a carbon material, nicotine escaping from the tobacco material particles is decomposed and deposited on the surface of the carbon material before the inorganic porous layer is formed, and the carbon material is etched by the activating agent to form the step porous carbon particles. In addition, when the activating solution further contains a coupling reagent, the coupling reagent promotes the organic nitride in the tobacco material to be coupled and grafted to the carbon material in the carbonization process, so that the utilization rate of the nitrogen-containing compound in the carbon material is further enhanced. And finally, coating the stepped nitrogen-containing porous carbon particles by the inorganic porous layer to obtain the porous carbon composite material with the core-shell structure.
The porous carbon composite material with the core-shell structure provided by the invention is applied to cigarette filters, soil conditioners, water treatment adsorbents or electrodes. Wherein, the water treatment adsorbent can be heavy metal adsorption or organic dye adsorbent for sewage treatment. The porous carbon composite material with the core-shell structure can be used as an electrode material or a formula of the electrode material when applied to an electrode, such as a super capacitor.
Therefore, compared with the prior art, the porous carbon composite material with the core-shell structure and the preparation method thereof provided by the invention have the following characteristics:
1. according to the porous carbon composite material with the core-shell structure, tobacco particle materials are used as raw materials, the surface of the tobacco particle materials is subjected to activation treatment, then a coating layer is formed, and finally carbonization treatment is carried out, so that the porous carbon composite material with the core-shell structure is obtained. Therefore, the preparation method provided by the invention has the advantages that the inorganic gel layer is formed on the surface of the tobacco activated particles, and the rapid overflow of nicotine is restrained in the carbonization process by virtue of the microenvironment of the formed coating layer, so that the loss of nicotine is slowed down or avoided, the contribution degree of the nicotine as a nitrogen source to the carbon material can be improved, the utilization rate of endogenous nitrogen elements in the preparation process of the tobacco-based carbon material can be improved, and the yield of carbon products is increased.
2. In the carbonization process, the coupling reagent can promote the organic nitrogen-containing compound to be coupled to the carbon material, so that the utilization rate of the nitrogen-containing compound in the carbonization process is improved, the content of nitrogen elements in the nitrogen-containing porous carbon particles can be effectively improved by adding the coupling reagent, the utilization rate of endogenous nitrogen elements is further improved, and the yield of carbon products is increased.
3. The preparation method provided by the invention has universality for nitrogen-rich carbon materials prepared from nitrogen-containing precursors, and particularly precursors in which nitrogen-containing compounds in the precursors are easy to decompose or volatilize, such as beans, seaweed, coffee and the like.
4. The porous carbon particles in the porous carbon composite material with the core-shell structure, which is provided by the invention and prepared by the provided method, have a step pore structure, are distributed in the ranges of micropores (less than 2 nm), mesopores (2-50 nm) and macropores (greater than 50 nm), are more suitable for adsorption of harmful components of cigarettes with wider particle size distribution, and have remarkable effect.
5. The porous carbon particles in the porous carbon composite material with the core-shell structure, which is provided by the invention and prepared by the provided method, are mainly prepared by taking a tobacco material as a raw material, are tobacco-based carbon materials, but are not commercialized coconut shell carbon or other plant-based or petroleum coal-based raw materials, and the inorganic porous layer has a protection effect on the carbon material, so that the porous carbon composite material with the core-shell structure is more difficult to introduce foreign flavor in the cigarette burning and smoking process, and the overall smoking taste of the cigarette is not influenced; the increase of the nitrogen content in the porous carbon particles strengthens the adsorption and adsorption stability of the porous carbon composite material to HCN in the flue gas.
Drawings
Fig. 1 is a flow chart of preparation of a porous carbon composite material having a core-shell structure according to an embodiment of the present invention.
Fig. 2 is a comparison graph of the performance of the porous carbon composite material with the core-shell structure for reducing HCN in cigarette smoke provided by the embodiment of the invention.
Detailed Description
The technical solution of the present invention is further described in detail by the following embodiments.
Example 1
The embodiment provides a porous carbon composite material with a core-shell structure, which is granular and consists of porous carbon particles and a silica porous layer wrapping the porous carbon particles. Wherein, the porous carbon particles are step nitrogen-containing porous carbon particles with the particle size of 20-40 meshes. The thickness of the silica porous layer is 150-200 nm, the silica porous layer comprises a plurality of micropores, and the pore diameter of each micropore is 1.2 nm.
Referring to fig. 1, the present embodiment further provides a method for preparing the porous carbon composite material with the core-shell structure, including:
raw material pretreatment, namely cleaning tobacco leaves, drying the cleaned tobacco leaves in a drying oven at 50 ℃ until the moisture content is below 10 percent, and crushing the tobacco leaves into 20-40 meshes to obtain tobacco particle raw materials;
10 g of the obtained tobacco particle raw material is weighed in an activating treatment, the tobacco particle raw material is dried and then is placed in KOH aqueous solution with the mass fraction of 10% for soaking, the tobacco particle raw material is filtered and dried in a 50 ℃ drying oven, and the load capacity of KOH is repeatedly adjusted for a plurality of times to obtain tobacco activated particles, wherein the load capacity of KOH is 5% of the mass of the tobacco particles;
formation of SiCl with 5% by volume of the coating 4 Ether solution to the SiCl 4 Adding a pore-forming agent ethylenediamine into the ether solution to prepare a silica-coated solution, wherein the molar ratio of ethylenediamine to the porous silica layer is 0.5; soaking the tobacco activated particles in the silicon dioxide coating solution for 5 min in an equal volume manner, then performing suction filtration, and placing the tobacco activated particles in an oven for blast drying at 30 ℃ to obtain a silicon dioxide gel coated tobacco material; this step was repeated 7 times;
placing the silicon dioxide gel-coated tobacco material subjected to carbonization treatment and drying in a tubular furnace, heating to 700 ℃ at a heating rate of 50 ℃/min under the nitrogen atmosphere, keeping the temperature for 20 min, and cooling to obtain the crude porous carbon composite material with the core-shell structure;
and purifying, namely ultrasonically cleaning the crude porous carbon composite material with the core-shell structure in an aqueous solution for 1 h, filtering, and washing with water to be neutral to obtain the finished porous carbon composite material with the core-shell structure.
Example 2
The embodiment provides a porous carbon composite material with a core-shell structure, which is granular and consists of porous carbon particles and a silica porous layer wrapping a plurality of the porous carbon particles. Wherein, the porous carbon particles are step nitrogen-containing porous carbon particles with the particle size of 100-200 meshes. The thickness of the silica porous layer is 100-150 nm, the silica porous layer comprises a plurality of micropores, and the pore diameter of each micropore is 1.7 nm.
The present embodiment also provides a preparation method of the porous carbon composite material with the core-shell structure, which is substantially the same as the preparation method provided in embodiment 1, and mainly differs in that "a coating layer is formed", specifically, siCl 4 The concentration of the ether solution was 3%, the molar ratio of ethylenediamine to the porous silica layer was 1.
Example 3
The embodiment provides a porous carbon composite material with a core-shell structure, which is granular and consists of porous carbon particles and a silica porous layer wrapping a plurality of the porous carbon particles. Wherein the porous particles are step nitrogen-containing porous carbon particles with the particle size of 40-80 meshes. The thickness of the silica porous layer is 50-100 nm, the silica porous layer comprises a plurality of micropores, and the pore diameter of each micropore is 0.9 nm.
This embodiment also provides a preparation method of the porous carbon composite material with the core-shell structure, which is substantially the same as the preparation method provided in embodiment 1, and mainly differs in that "forming a coating layer" is different, specifically, siCl 4 The concentration of the ether solution was 1%, the molar ratio of ethylenediamine to the porous layer of silica was 6: 1, and this "forming a coating layer" step was repeated 2 times.
Example 4
The embodiment provides a porous carbon composite material with a core-shell structure, which is granular and consists of porous carbon and a silica porous layer wrapping the porous carbon. The porous carbon particles are step nitrogen-containing porous carbon particles, the particle size length of the porous carbon particles is 2-5 mm, the thickness of the porous carbon particles is 1 mm, the thickness of the porous silicon dioxide layer is 60-80 nm, the porous silicon dioxide layer comprises a plurality of micropores, and the pore diameter of each micropore is 1.5 nm.
This example also provides a preparation method of the porous carbon composite material, which is substantially the same as the preparation method provided in example 1, and mainly differs in that the tobacco material in this example is a tobacco flake, and the step of "activation treatment" employs ZnCl with a mass fraction of 5% 2 The solution serves as an activation solution.
Example 5
The embodiment provides a porous carbon composite material with a core-shell structure, which is granular and consists of a plurality of porous carbon particles and a silica porous layer wrapping the plurality of porous carbon particles. The porous carbon particles are step nitrogen-containing porous carbon particles, the particle size of the step nitrogen-containing porous carbon particles is 40-60 meshes, the thickness of the silica porous layer is 40-50 nm, the silica porous layer comprises a plurality of micropores, and the pore diameter of each micropore is 1.1 nm.
The embodiment also provides a preparation method of the porous carbon composite material with the core-shell structure, which is basically the same as the preparation method provided in embodiment 1, and mainly differs in that the tobacco material in the embodiment is a tobacco stalk, and the step of activating treatment adopts 15% by mass of H 3 PO 4 Solution as activating solution, H 3 PO 4 The loading of (b) was 13%.
Example 6
The embodiment provides a porous carbon composite material with a core-shell structure, which is granular and consists of porous carbon particles and a silica porous layer wrapping a plurality of the porous carbon particles. Wherein the porous particles are step nitrogen-containing porous carbon particles with the particle size of 50-70 meshes. The thickness of the silica porous layer is 45-60 nm, the silica porous layer comprises a plurality of micropores, and the pore diameter of each micropore is 1.2 nm.
The embodiment also provides aThe preparation method of the porous carbon composite material with the core-shell structure is basically the same as that provided in the embodiment 1, and mainly differs from the embodiment in that the tobacco material is a cigarette butt, and the step of activating treatment adopts ZnCl with the mass fraction of 5% 2 Solution as activating solution, znCl 2 The loading of (b) was 10%.
Application of porous carbon composite material with core-shell structure
Adding the samples prepared in the embodiments 1 to 6 into a cigarette filter, wherein the filter is of a three-section structure, the middle of the filter is of a cavity structure, the filter is used for adding the samples prepared in the embodiments 1 to 6 of the adsorption material, and the adding amount of the samples prepared in the embodiments 1 to 7 is 20 mg per cigarette; the comparative sample is obtained by direct carbonization of the starting material of example 1 under the corresponding carbonization conditions, i.e. omitting the "formation of the coating".
The rolled sample is placed at the temperature of 22 +/-1 ℃ and the relative humidity of 60 +/-2% for balancing for 48 hours, then a comprehensive test bench is adopted to represent the physical parameters of all cigarettes, and cigarettes with the average mass of +/-0.01 g and the average suction resistance of +/-49 Pa are selected as test cigarette samples. A20H type turntable type smoking machine is used according to GB/T16450-2004 smoking machine and test standard conditions thereof: wind speed is 200 + -30 mm/s, suction capacity is 35 + -0.3 ml, duration is 2 s, suction interval is 60s, smoking cigarette, electrostatic laying pipe is used to lay out medium particle phase matter of mainstream smoke, 20 ml 10% (v/v) nitric acid solution is used to collect gas phase. The detection and analysis of HCN in the smoke are determined according to a standard method of YC/253-2008 continuous flow method for determining hydrogen cyanide in the main stream smoke of cigarettes. The results are shown in figure 2, in terms of cigarette reduction rate and number of reuses.
As can be seen from the results in fig. 2, compared with a control sample, the porous carbon composite material with the core-shell structure provided by the embodiment of the present invention has a significant effect on reduction of HCN in smoke, regardless of reduction rate or reusability, and can be used alone or as an additive for an external cigarette filter.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention and not to limit it; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art will understand that: modifications to the specific embodiments of the invention or equivalent substitutions for parts of the technical features may be made; without departing from the spirit of the present invention, it is intended to cover all aspects of the invention as defined by the appended claims.
Claims (10)
1. A porous carbon composite material with a core-shell structure is characterized in that: the porous carbon particle composite material comprises porous carbon particles and an inorganic porous layer coating the porous carbon particles, wherein the inorganic porous layer is a silicon dioxide porous layer with the thickness of less than or equal to 200 nm, the porous carbon particles are stepped-pore nitrogen-containing porous carbon particles, and the granularity is 20-200 meshes; the porous carbon composite material is mainly prepared by the following steps:
activating to provide an activating solution, wherein the activating solution comprises an activating agent with the mass fraction of 1-20%; firstly, soaking a tobacco particle raw material into the activating solution, and then drying to load the tobacco particle raw material with the activating agent, wherein the loading amount of the activating agent on the tobacco particle raw material is 0.5-20% of the mass of the tobacco particle raw material, so as to obtain tobacco activated particles;
forming a coating layer and providing a coating solution, wherein the coating solution comprises an inorganic layer precursor and a pore-forming agent which are uniformly mixed; dripping the coating solution into the tobacco activated particles, and drying at 30-100 ℃ to obtain inorganic layer gel coated tobacco particles, wherein the inorganic layer gel coated tobacco particles comprise the tobacco activated particles and inorganic gel coating layers coated on the surfaces of the tobacco activated particles, and the inorganic gel coating layers are composed of mixed inorganic gel materials and the pore-forming agent;
and carbonizing the inorganic layer gel-coated tobacco particles to obtain the porous carbon composite material with the core-shell structure.
2. Porous carbon composite according to claim 1, characterized in that: the inorganic porous layer comprises a plurality of micropores, and the pore diameter of each micropore is 0.3-2 nm.
3. A method of preparing a porous carbon composite as claimed in claim 1 or 2, comprising:
activating to provide an activating solution, wherein the activating solution comprises an activating agent with the mass fraction of 1-20%; firstly, soaking a tobacco particle raw material into the activating solution, and then drying to load the tobacco particle raw material with the activating agent, wherein the loading amount of the activating agent on the tobacco particle raw material is 0.5-20% of the mass of the tobacco particle raw material, so as to obtain tobacco activated particles;
forming a coating layer and providing a coating solution, wherein the coating solution comprises an inorganic layer precursor and a pore-forming agent which are uniformly mixed; dripping the coating solution into the tobacco activated particles, and then drying at 30-100 ℃ to obtain inorganic layer gel coated tobacco particles, wherein the inorganic layer gel coated tobacco particles comprise the tobacco activated particles and inorganic gel coating layers coated on the surfaces of the tobacco activated particles, and the inorganic gel coating layers are composed of mixed inorganic gel materials and the pore-forming agent;
and carbonizing the inorganic layer gel-coated tobacco particles to obtain the porous carbon composite material with the core-shell structure.
4. The method for preparing a porous carbon composite according to claim 3, characterized in that: the activating agent is KOH or ZnCl 2 、H 3 PO 4 Or MnO 2 。
5. The method for preparing a porous carbon composite according to claim 3 or 4, characterized in that: the step of forming the coating layer comprises providing the coating solution, wherein the volume concentration of the inorganic layer precursor is 5-10%; dripping the coating solution into the tobacco activated particles for equal-volume impregnation, and then forming the inorganic gel coating layer on the surfaces of the tobacco activated particles; and then drying at 30-100 ℃ to obtain the inorganic layer gel-coated tobacco particles.
6. The method for preparing a porous carbon composite according to claim 5, characterized in that: the inorganic layer precursor is a silicon source material, and the coating solution comprises SiCl 4 Ether solution of (a), ethanol solution of organosilane or water glass.
7. The method for preparing a porous carbon composite according to claim 6, characterized in that: further comprising repeating the step of forming a cladding layer.
8. The method for preparing a porous carbon composite according to claim 3 or 4, characterized in that: and the step of carbonizing comprises the steps of transferring the inorganic layer gel coated tobacco particles into a container, heating to 550-900 ℃, and maintaining for 0.5-6 hours to obtain the porous carbon composite material with the core-shell structure.
9. The method for preparing a porous carbon composite according to claim 3 or 4, characterized in that: the preparation method of the tobacco particle raw material comprises the steps of cleaning, drying and crushing the tobacco material to obtain the tobacco particle raw material.
10. Use of a porous carbon composite according to claim 1 or 2, characterized in that: the porous carbon composite material is applied to cigarette filters, soil conditioners, water treatment adsorbents or electrodes.
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