CN112645328B - Preparation method and application of nitrogen-containing porous carbon material - Google Patents
Preparation method and application of nitrogen-containing porous carbon material Download PDFInfo
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- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
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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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- 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
- C01B32/342—Preparation characterised by non-gaseous activating agents
Abstract
The invention provides a preparation method of a nitrogen-containing porous carbon material, which comprises the following steps: the method comprises the following steps of activating, impregnating, carbonizing and purifying the tobacco material to obtain the nitrogen-containing porous carbon material, wherein the impregnating step comprises forming a coating layer on the surface of the tobacco material containing the activating agent. In the carbonization treatment process, nicotine escaping from the tobacco material is difficult to rapidly disperse outside the coating layer due to the constraint of the coating layer, and simultaneously participates in carbonization, wherein nitrogen element is used as a nitrogen source of a final carbon material, so that the utilization rate of endogenous nitrogen element and the yield of carbon products in the preparation process of the tobacco-based carbon material are effectively improved. The invention also provides an application of the nitrogen-containing porous carbon material prepared by the method, and the nitrogen-containing porous carbon material is applied to cigarette filters, soil conditioners, water treatment adsorbents or electrodes.
Description
Technical Field
The invention relates to recycling of tobacco waste, in particular to a preparation method and application of a nitrogen-containing porous carbon material.
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 according to statistics, only the waste is generatedTobacco stalks produced in 2015 year can 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 and discarding or burning mode, the comprehensive utilization rate is extremely low, not only is the environmental pollution caused, but also a large amount of the 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 activating agent 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 the condition of high temperature 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 Xianhong and the like respectively adopt carbon dioxide and water vapor activation methods to prepare microporous tobacco stem base granular activated carbon (Xianhong, peng Jinhui, zhang Libo and the like, oxidation by dioxideStudy on preparation of tobacco-stem-based granular activated carbon by carbon activation [ J]38-41. Xianhong, peng Jinhui, zhang Libo, and the like, research on preparation of tobacco stem-based granular activated carbon by water vapor activation [ J]Ion exchange and adsorption 2007 (02): 112-118. Summer flood, peng Jinhui, zhang Libo, and the like]Chemical engineering 2007 (01): 48-51). The carbon material prepared by the physical activation method has relatively low BET specific surface area, most of pores belong to micropores, and the contents of mesopores and macropores are 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. Chinese patent application No. CN021132704, entitled "method for manufacturing activated carbon by microwave radiation of tobacco stem solid waste" discloses a method for heating tobacco stems and zinc chloride solution after impregnation to obtain activated carbon products. The method has the problem of zinc chloride volatilization pollution in the actual production process. Chinese patent application No. CN2005100106702, entitled "a method for producing activated carbon with high specific surface area", discloses a method for producing activated carbon with high specific surface area by dipping tobacco stems in potassium hydroxide solution and then heating. Chinese patent application No. CN2009101846454, entitled "a preparation method of high-pore activated carbon", discloses a method for preparing an activated carbon product by mixing, soaking and heating activation of a biomass raw material, phosphoric acid and an activation aid (peroxy or peroxy compound). The invention patent applications CN2005100106702 and CN2009101846454 are in high temperature condition due to the use of alkali or acid, so the corrosion problem to equipment is serious, and the yield is low.
In the preparation strategy of nitrogen doping, the preparation method of the nitrogen-doped porous carbon mainly comprises the steps of pyrolyzing the carbon-containing material according to different nitrogen sourcesNitrogen precursors or carbonization with the aid of an exogenous 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 tobacco stalk carbon, ma and the like also make preliminary attempts by adopting an exogenous method, firstly, tobacco stalks are mixed with ethylenediamine (ethylene) 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, etc. uses cigarette butt as raw material to prepare nitrogen-doped multi-stage porous carbon material for super capacitor, and its preparation method includes soaking cigarette butt in acetonitrile solution, adding pyrrole, then adding FeCl 3 Polymerizing pyrrole, then carrying out ultrasonic treatment at 4 ℃ and maintaining the temperature at 4 ℃ of 10 h, cleaning to obtain a cigarette end/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 multistage porous carbon material, wherein the nitrogen element of the nitrogen-doped multistage porous carbon material 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, as of today, carbon materials made therefrom have generally not high nitrogen content due primarily to The low boiling point of nicotine (247 ℃), and The existing direct carbonization, physical activation and self-activation processes have a significant flux of nicotine during Thermal conversion, and most of The nicotine migrates from The tobacco substrate, such as under hydrothermal conditions of 150 ℃ to 160 ℃ in solution systems (The Journal of Supercritical Fluids, 153 (2019) 104593.), 20153-794 Energy & Fuels, 30 (2016) 1579-1588, applied Thermal theory, 106 (2016) 1579-1588, 20154 Energy & Fuels, 20158 (2018) 013112 Journal of Thermal Analysis and calibration, 136 (2018). 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, and no literature report or patent application exists.
Disclosure of Invention
In view of the above, the present invention provides a method for preparing a nitrogen-containing porous carbon material and applications thereof, so as to overcome the above problems.
The invention provides a preparation method of a nitrogen-containing porous carbon material, which comprises the following steps:
firstly, soaking a tobacco particle raw material into an activating agent solution to enable the tobacco particle raw material to load an activating agent in the activating agent solution; drying to obtain tobacco raw materials containing an activating agent, wherein the activating agent accounts for 1-20% of the mass of the activating agent in the activating agent solution;
firstly, dropwise adding an inorganic layer precursor solution into the tobacco raw material containing the activating agent, and then drying at 30-100 ℃ to obtain an inorganic coated tobacco material, wherein the inorganic coated tobacco material comprises the tobacco raw material containing the activating agent and an inorganic gel layer coated on the surface of the tobacco raw material containing the activating agent;
carbonizing the inorganic coated tobacco material to obtain an inorganic coated porous carbon composite material, wherein the inorganic coated porous carbon composite material comprises porous carbon particles and an inorganic layer wrapping the porous carbon particles;
and purifying the inorganic coated porous carbon composite material to remove the inorganic layer, washing and drying to obtain the nitrogen-containing porous carbon material.
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 to 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 activating step, 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 impregnating comprises: dropwise adding the inorganic layer precursor solution to the tobacco raw material containing the activating agent until the inorganic layer precursor solution just submerges the surface of the tobacco raw material containing the activating agent, standing and aging, forming a coating layer on the surface of the tobacco raw material containing the activating agent, and then drying at 30-100 ℃ to obtain the inorganic coated tobacco material; wherein the volume concentration of the inorganic layer precursor solution is 5-10%.
Wherein the thickness of the inorganic gel layer in the inorganic coated tobacco material can be adjusted by adjusting the concentration of the inorganic layer precursor solution or the number of times of performing the impregnation step according to actual conditions. Therefore, preferably, the above-described method for producing a nitrogen-containing porous carbon material further includes a step of repeating the impregnation a plurality of times.
The main purpose of the impregnation step is to reduce or avoid the escape of nicotine from the tobacco material during the subsequent carbonization treatment, thereby increasing the availability of nitrogen in the nicotine. The principle of formation of the inorganic gel layer is as follows: and forming an inorganic gel layer on the surface of the tobacco raw material containing the activating agent by hydrolyzing the inorganic layer precursor by means of the activating agent solution or air moisture.
If the thickness is thinner and is less than 3 nm, the inorganic gel layer is easily broken by the gas formed in the subsequent carbonization process, so that the nicotine escapes from the inorganic gel layer and is volatilized into the natural environment, the utilization of nitrogen elements in the nicotine is influenced, and the nitrogen content in the nitrogen-containing porous carbon material is also reduced. In the carbonization process, the inorganic gel layer becomes an inorganic layer, and if the thickness of the inorganic gel layer is relatively thick, the difficulty is increased for subsequent removal of the inorganic layer, and the preparation efficiency and cost are affected, so the thickness of the inorganic gel layer is preferably not more than 100 nm. Therefore, the thickness of the inorganic gel layer is preferably 3 to 100 nm.
Based on the above, the inorganic gel layer is a silica gel layer, and the inorganic layer is a silica layer.
Based on the above, the inorganic layer precursor solution is 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 step of carbonizing comprises: and transferring the inorganic coated tobacco material into a container, heating to 550-900 ℃, and maintaining the temperature at 0.5-5 h, preferably 1-2 h to obtain the inorganic coated porous carbon composite material.
In the carbonization process of the inorganic coated tobacco material, the inorganic gel material in the inorganic gel layer loses water to form the inorganic layer, meanwhile, the coated tobacco material containing an activating agent can shrink, a carbon source in the inorganic coated tobacco material is carbonized to form a carbon material, nicotine escaping from the tobacco material is decomposed and deposited on the surface of the carbon material, the carbon material is etched by the activating agent to form gradient porous carbon, and finally, the gradient nitrogen-containing porous carbon material is obtained.
Based on the above, the step of purifying comprises: and (2) cleaning the inorganic coated porous carbon composite material by using HF acid with the volume fraction of 5-40% to remove the inorganic layer and the residual activating agent, and then repeatedly washing the inorganic coated porous carbon composite material by using deionized water until the inorganic coated porous carbon composite material is neutral and drying the inorganic coated porous carbon composite material to obtain the nitrogen-containing porous carbon material.
Specifically, the inorganic coated porous carbon composite material is placed in an HF acid solution with the volume fraction of 5% -40%, soaked in 0.5-12 h at the temperature of 20-80 ℃, and then washed with water and dried to obtain the nitrogen-containing porous carbon material. Preferably, the inorganic coated porous carbon composite material is continuously stirred in the process of soaking in the HF acid solution. The step of purifying is mainly used for removing the inorganic layer coated on the surface of the nitrogen-containing porous carbon material, and basically has no influence on the nitrogen-containing porous carbon material and nitrogen elements contained in the nitrogen-containing porous carbon material.
The nitrogen-containing porous carbon material prepared by the method provided by the invention is applied to cigarette filters, soil conditioners, water treatment adsorbents or electrodes. Wherein, the water treatment adsorbent can be an adsorbent for heavy metal or organic dye in sewage. The nitrogen-containing porous carbon material 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, the preparation method of the nitrogen-containing porous carbon material provided by the invention has the following characteristics:
1. the tobacco material is rich in nitrogen elements and mainly exists in nicotine, and most of the nitrogen elements in the nicotine in the tobacco do not enter the final carbon material as raw materials in the process of preparing the carbon material by using the tobacco material. However, in the preparation method provided by the invention, the tobacco particle raw material is taken as an object, and the nitrogen-containing porous carbon material is prepared by sequentially carrying out treatments such as impregnation of a functional reagent activating agent, impregnation to form a coating layer, carbonization, purification to remove the coating layer, water washing and the like. According to the preparation method provided by the invention, the coating layer is formed on the surface of the tobacco material containing the activating agent, and the coating layer can bind nicotine in a certain time in the carbonization process so as to avoid dispersing outside the coating layer, so that the loss of nicotine is reduced or avoided.
2. The preparation method provided by the invention has universality for the nitrogen-containing porous carbon material prepared from the nitrogen-containing plant raw material, and particularly, the nitrogen-containing compound in the plant raw material is easy to decompose or volatilize, such as leguminous plants or seeds, coffee, oat, seaweed and the like.
3. The nitrogen-containing porous carbon material prepared by the method provided by the invention is a gradient pore carbon material, has certain distribution in the ranges of micropores (< 2 nm), mesopores (2-50 nm) and macropores (> 50 nm), is more suitable for adsorption of harmful ingredients of cigarettes with wider particle size distribution, and has obvious effect.
4. The nitrogenous porous carbon material prepared by the method is prepared by taking a tobacco particle material as a raw material, is a tobacco-based carbon material, is not a commercialized coconut shell carbon or other plant-based or petroleum coal-based raw material, and is difficult to introduce foreign flavor in the burning and smoking process of cigarettes without influencing the overall smoking taste of the cigarettes; the increase of the nitrogen content in the carbon material strengthens the adsorption of the carbon material to phenol and HCN in the flue gas.
Drawings
FIG. 1 is a flow chart of a process for producing a nitrogen-containing porous carbon material according to an embodiment of the present invention.
Detailed Description
The technical solution of the present invention is further described in detail by the following embodiments.
The preparation method of the nitrogen-containing porous carbon material provided by the invention mainly comprises the steps of forming a coating layer on the surface of a tobacco material, then carrying out high-temperature carbonization treatment, and finally carrying out purification treatment to obtain the nitrogen-containing porous carbon material. In the high-temperature carbonization treatment process, nicotine escaping from the tobacco material is difficult to disperse in the natural environment due to being bound by the coating layer, and the provided microenvironment can enable nitrogen elements to serve as nitrogen sources of the final carbon material, so that the nitrogen element doped carbon material is prepared by adopting endogenous nitrogen elements.
1. Influence of technological parameters on nitrogen-containing porous carbon material prepared by the invention
The utilization of endogenous nitrogen elements in the tobacco material and the nitrogen content in the nitrogen-containing porous carbon material are controlled mainly by controlling the thickness and compactness of the coating layer. Among the factors that influence the thickness and compactness of the coating are: the amount of activator supported, the concentration of the inorganic layer precursor solution, the aging time of the inorganic layer, and the number of repetitions of the impregnation step, wherein varying the concentration of the inorganic layer precursor solution and the number of impregnation steps is the most efficient way of preparation.
Referring to fig. 1, a method for preparing a nitrogen-containing porous carbon material includes:
1) The pretreatment comprises the steps of cleaning the tobacco leaf raw material, drying the cleaned tobacco leaf raw material in a drying oven at 50 ℃ until the water content is 10%, and crushing the tobacco leaf raw material into particles of 20-40 meshes to obtain the tobacco leaf particle raw material, wherein the tobacco leaf particle raw material is in an irregular spherical shape;
2) Activating and weighing the obtained tobacco leaf particle raw material 10 g, drying, soaking in a KOH aqueous solution with the mass fraction of 10% for 30 min, filtering, drying in a 50 ℃ oven, and repeatedly adjusting the load of the activating agent KOH for a plurality of times to obtain the tobacco raw material containing the activating agent, wherein the load of KOH on the tobacco raw material containing the activating agent is 0.5% -20% of the mass of the tobacco raw material;
3) Impregnating SiCl with the concentration of 5-10% according to the volume 4 Ether solution, adding the SiCl 4 Adding an ether solution and dropwise into the tobacco raw material containing the activator for isovolumetric impregnation, standing for 5-10 min, then carrying out suction filtration, placing in an oven for drying by blowing at 30 ℃, and forming a silica gel layer with the thickness of 10-40 nm on the surface of the tobacco raw material containing the activator to prepare the silica gel-coated tobacco material;
4) The carbonized and dried silicon dioxide gel coated tobacco material is placed in a tube furnace, the temperature is raised to 550 ℃ at the heating rate of 50 ℃/min under the nitrogen atmosphere, and 2 h is kept, and the SiO is prepared after cooling 2 Coating with a porous carbon composite material;
5) Purifying the SiO 2 Placing the porous carbon-coated composite material in HF aqueous solution with the mass concentration of 5 percent at room temperatureStirring for 60 min, filtering, and washing with water to neutrality to obtain the nitrogen-containing porous carbon material.
(1) Effect of activator loading on texture parameters, nitrogen content and yield of nitrogen-containing porous carbon material
The loading capacity of the activating agent is respectively 0.5%, 5%, 10% and 20%, and the content of SiCl is 4 Concentration of Ether solution 5%, siO 2 Aging for 5 min, and repeating the soaking step for 3 times; the structural parameters and the yield of the nitrogen-containing porous carbon material prepared under the conditions are shown in table 1.
Wherein the "nitrogen content" is measured by an elemental analyzer, and the calculation thereof is based on the mass of a comparative sample carbon material under corresponding conditions; the related parameters of the pore structure are determined by a BET method according to a nitrogen physical adsorption experiment; the "yield" is measured using an electronic balance and is the yield of the primary carbonized material relative to the tobacco material. Pore size of "micropores" in the tables below<2 nm, a "mesoporous" pore size of 2-50 nm, and a "macroporous" pore size>50 nm、“V T "represents the total volume of micropores, mesopores and macropores on the carbon material.
TABLE 1 influence of activator loading on texture parameters, nitrogen content and yield of nitrogen-containing porous carbon materials
As can be seen from table 1: the BET specific surface area of the obtained nitrogen-containing porous carbon material is increased along with the increase of the loading capacity of the activator, the total pore volume is in a consistent change trend, the nitrogen content is higher than 5 percent and can reach 11.5 percent at most, and the yield is between 40 and 60 percent.
(2) Influence of concentration of inorganic layer precursor solution on texture parameters, nitrogen content and yield of nitrogen-containing porous carbon material
SiCl 4 The concentration of the ether solution is respectively 5%, 8% and 10%, the load of KOH is 5%, and SiO is 2 Aging for 5 min, and performing the soaking step for 1 time; the structural parameters and the yield of the nitrogen-containing porous carbon material prepared under the conditions are shown in table 2.
TABLE 2 SiCl 4 Influence of concentration of ether solution on texture parameters, nitrogen content and yield of nitrogen-containing porous carbon material
As can be seen from table 2: followed SiCl 4 The BET specific surface area of the nitrogen-containing porous carbon material is reduced, and the nitrogen content and the yield of the carbon-based material are obviously increased due to the increase of the concentration of the ether solution.
(3) Influence of repetition number of impregnation steps on texture parameters, nitrogen content and yield of the nitrogen-containing porous carbon material
KOH loading 5%, siCl 4 Concentration of Ether solution 5%, siO 2 Aging for 5 min, wherein the repeated times of the dipping step are respectively as follows: 1 time, 2 times and 3 times; the structural parameters and the yield of the nitrogen-containing porous carbon material prepared under the conditions are shown in table 3.
TABLE 3 number of repetitions of the impregnation step versus texture parameters for nitrogen-containing porous carbon materials,
Influence of Nitrogen content and yield
As can be seen from table 3: with the increase of the number of times of impregnation, that is, with the increase of the number of times of modification of the coating layer, the BET specific surface area of the nitrogen-containing porous carbon material is reduced, and the nitrogen content and the yield of the carbon-based material are remarkably increased.
2. Influence of tobacco material on nitrogen-containing porous carbon material prepared by the invention
The effect of the tobacco material on the nitrogen-containing porous carbon material was mainly reflected by the texture parameters, nitrogen content and yield of the comparative example samples and the comparative example samples, as shown in table 4. The specific test method is as follows:
(1) The test subjects of examples 1 to 4 were tobacco leaves, tobacco flakes, tobacco stems, and cigarette butts, respectively, and examples 1 to 4 were carried out under the following test conditions.
The preparation method specifically comprises the following steps:
pretreating, placing a test object after cleaning in a drying oven at 50 ℃ until the moisture content is 5%, and crushing to 20-40 meshes to obtain tobacco particle raw materials, wherein the tobacco particle raw materials are irregular spheres;
activating and weighing the obtained tobacco particle raw material 10 g, drying and then placing the tobacco particle raw material into H with the mass fraction of 10% 3 PO 4 Soaking in the solution, filtering, drying in a 50 deg.C oven, and repeatedly adjusting ZnCl 2 To obtain tobacco raw material containing an activator, and the ZnCl 2 The loading amount of (A) is 5% of the mass of the tobacco raw material;
impregnating with 5% by volume SiCl 4 Ether solution, adding SiCl 4 Soaking the tobacco raw material containing the activating agent in an ether solution in an equal volume, standing for 5 min, then performing suction filtration, and placing in an oven for blast drying at 30 ℃ to obtain a silicon dioxide gel-coated tobacco material; wherein the thickness of the silica gel layer is about 10-40 nm;
the carbonized and dried silicon dioxide gel coated tobacco material is placed in a tube furnace, the temperature is raised to 900 ℃ at the heating rate of 50 ℃/min under the nitrogen atmosphere, 1 h is kept, and SiO is prepared after cooling 2 Coating a crude product of the porous carbon composite material;
purifying the SiO 2 And (3) placing the porous carbon-coated composite material in HF aqueous solution with the mass concentration of 5%, stirring for 60 min at room temperature, filtering, and washing to be neutral to obtain the sample of the embodiment. Wherein, the samples of examples in which the raw materials are respectively tobacco leaves, tobacco flakes, tobacco stems and cigarette butts are respectively marked as example 1, example 2, example 3 and example 4.
(2) Test conditions of comparative example the preparation method of the comparative example, which includes four steps of pretreatment, activation, carbonization, and purification, is substantially the same as the preparation method of the example, except that: the comparative example was prepared by omitting the "dipping" step and the other steps and process parameters were the same. Wherein, comparative samples of which the raw materials are tobacco leaves, tobacco flakes, tobacco stems and cigarette butts are respectively marked as comparative example 1, comparative example 2, comparative example 3 and comparative example 4.
TABLE 4 influence of tobacco material on texture parameters, nitrogen content and yield of nitrogen-containing porous carbon materials
As can be seen from table 4: under the same other conditions, compared with the condition that no coating layer is formed on the surface of the tobacco material, the nitrogen content of the nitrogen-containing porous carbon material prepared by the method provided by the invention can be increased by more than 3 times.
3. Application of nitrogen-containing porous carbon material prepared by using method provided by the invention
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 part of the filter is of a cavity structure and 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 6 is 20 mg for each cigarette; the control sample was prepared by adding an equal amount of quartz sand to the cavity section.
The rolled cigarette is placed under the conditions that the temperature is 22 +/-1 ℃ and the relative humidity is 60 +/-2 percent to balance 48 h, then a comprehensive test bench is adopted to represent physical parameters of cigarettes, and cigarettes with the average mass +/-0.01 g and the average suction resistance +/-49 Pa are selected to serve as test cigarette samples. A20H turntable type smoking machine is used according to GB/T16450-2004 smoking machine and test standard conditions thereof: wind speed 200 + -30 mm/s, suction capacity 35 + -0.3 ml, duration 2 s, suction interval 60s, smoking cigarettes, spreading the particulate phase of mainstream smoke with an electrostatic spreading tube, and collecting the gas phase with 20 ml of 10% (v/v) nitric acid solution. The detection and analysis of phenol and HCN in the smoke are respectively determined according to a standard method of high performance liquid chromatography for determining main phenolic compounds in main stream smoke of YC/T255-2008 cigarettes and a continuous flow method for determining hydrogen cyanide in the main stream smoke of YC/253-2008 cigarettes. The results are shown in Table 5.
As can be seen from the results in table 5, the carbon material is significantly effective in reducing phenol and HCN in flue gas, as compared to the control.
TABLE 5 reduction of phenol and HCN in cigarette smoke by nitrogen-containing porous carbon materials
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 the preferred embodiments, those skilled in the art should 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 (9)
1. A method for producing a nitrogen-containing porous carbon material, comprising:
firstly, soaking a tobacco particle raw material into an activating agent solution to enable the tobacco particle raw material to load an activating agent in the activating agent solution; drying to obtain tobacco raw materials containing an activating agent, wherein the mass fraction of the activating agent in the activating agent solution is 1-20%, and the loading capacity of the activating agent on the tobacco particle raw materials is 0.5-20% of the mass of the tobacco particle raw materials;
firstly, dropwise adding an inorganic layer precursor solution into the tobacco raw material containing the activating agent, and then drying at 30-100 ℃ to obtain an inorganic coated tobacco material, wherein the inorganic coated tobacco material comprises the tobacco raw material containing the activating agent and an inorganic gel layer coated on the surface of the tobacco raw material containing the activating agent, and the inorganic gel layer is a silicon dioxide gel layer;
carbonizing the inorganic coated tobacco material to prepare an inorganic coated porous carbon composite material, wherein the inorganic coated porous carbon composite material comprises porous carbon particles and an inorganic layer wrapping the porous carbon particles, and the inorganic layer is a silicon dioxide layer;
and purifying the inorganic coated porous carbon composite material to remove the inorganic layer, washing and drying to obtain the nitrogen-containing porous carbon material.
2. The method for producing a nitrogen-containing porous carbon material according to claim 1, wherein the activator is KOH or ZnCl 2 、H 3 PO 4 Or MnO 2 。
3. The method for producing a nitrogen-containing porous carbon material according to claim 1 or 2, characterized in that the step of impregnating comprises: dropwise adding the inorganic layer precursor solution to the tobacco raw material containing the activating agent until the inorganic layer precursor solution just submerges the surface of the tobacco raw material containing the activating agent, standing and aging, forming a coating layer on the surface of the tobacco raw material containing the activating agent, and then drying at 30-100 ℃ to obtain the inorganic coated tobacco material; wherein the volume concentration of the inorganic layer precursor solution is 5-10%.
4. The method for producing a nitrogen-containing porous carbon material according to claim 3, wherein the inorganic layer precursor solution is SiCl 4 Ether solution of (a), ethanol solution of organosilane or water glass.
5. The method for producing a nitrogen-containing porous carbon material according to claim 4, further comprising a step of repeating the impregnation.
6. The method for producing a nitrogen-containing porous carbon material according to claim 3, wherein the carbonizing step comprises: and transferring the inorganic coated tobacco material into a container, heating to 550-900 ℃, and maintaining the temperature at 0.5-5 h to obtain the inorganic coated porous carbon composite material.
7. The method according to claim 6, wherein the step of purging includes: and (2) cleaning the inorganic coated porous carbon composite material by using HF acid with the volume fraction of 5-40% to remove the inorganic layer and the residual activating agent, then repeatedly washing the inorganic coated porous carbon composite material to be neutral by using deionized water, and drying to obtain the nitrogen-containing porous carbon material.
8. The method for producing a nitrogen-containing porous carbon material according to claim 1, wherein the method for producing the tobacco particulate raw material comprises: and cleaning, drying and crushing the tobacco material to obtain the tobacco particle raw material.
9. The application of the nitrogen-containing porous carbon material is characterized in that the nitrogen-containing porous carbon material is prepared by the preparation method of the nitrogen-containing porous carbon material according to any one of claims 1 to 8, and the nitrogen-containing porous carbon material is applied to cigarette filters, soil improvement agents, water treatment adsorbents or electrodes.
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