CN114558603B - Nitrogen-doped hollow hierarchical pore carbon microsphere with high oxygen content and preparation method and application thereof - Google Patents

Nitrogen-doped hollow hierarchical pore carbon microsphere with high oxygen content and preparation method and application thereof Download PDF

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CN114558603B
CN114558603B CN202210229951.0A CN202210229951A CN114558603B CN 114558603 B CN114558603 B CN 114558603B CN 202210229951 A CN202210229951 A CN 202210229951A CN 114558603 B CN114558603 B CN 114558603B
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oxygen content
nitrogen
high oxygen
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microspheres
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CN114558603A (en
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吴铎
蒋管赟
吴张雄
高兴敏
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Suzhou University
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
    • B01J27/24—Nitrogen compounds
    • B01J35/50—
    • B01J35/51—
    • B01J35/617—
    • B01J35/618—
    • B01J35/633—
    • B01J35/635—
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/0009—Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst
    • B01J37/0018—Addition of a binding agent or of material, later completely removed among others as result of heat treatment, leaching or washing,(e.g. forming of pores; protective layer, desintegrating by heat)
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/08—Heat treatment
    • B01J37/082—Decomposition and pyrolysis
    • B01J37/084—Decomposition of carbon-containing compounds into carbon
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/72—Treatment of water, waste water, or sewage by oxidation
    • C02F1/725—Treatment of water, waste water, or sewage by oxidation by catalytic oxidation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/72—Treatment of water, waste water, or sewage by oxidation
    • C02F1/78—Treatment of water, waste water, or sewage by oxidation with ozone
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/30—Organic compounds
    • C02F2101/34—Organic compounds containing oxygen
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Abstract

The invention provides a preparation method of nitrogen-doped hollow hierarchical pore carbon microspheres with high oxygen content, which comprises the following steps: dissolving histidine and a salt template agent in a hydrochloric acid aqueous solution, and stirring and mixing at room temperature to obtain a precursor solution; carrying out spray drying on the precursor solution to obtain hollow microspheres with unique forms, wherein the temperature of the top of the tower in the spray drying process is 150-200 ℃; calcining the hollow microspheres in an inert atmosphere at 600-1000 ℃; and removing the salt template agent by water washing to obtain the nitrogen-doped hollow multistage pore carbon microsphere with high oxygen content. The hollow carbon microsphere prepared by combining a salt template method with a spray drying technology has good catalytic performance on ozone oxidation reaction.

Description

Nitrogen-doped hollow hierarchical pore carbon microsphere with high oxygen content and preparation method and application thereof
Technical Field
The invention belongs to the technical fields of microsphere preparation and ozone oxidation catalysis, and particularly relates to a nitrogen-doped hollow hierarchical pore carbon microsphere with high oxygen content, and a preparation method and application thereof.
Background
Hierarchical pore carbon materials have great potential in energy storage and conversion, heterogeneous catalysis, adsorption, separation, and life sciences applications. In recent years, remarkable progress is made in the aspects of design and synthesis of the materials, and salt templates are widely applied to synthesis of hierarchical pore carbon materials due to the advantages of low price, rich types, easy removal and the like.
At present, in the research on the preparation of hierarchical pore carbon materials using a salt template method, most of the research involves dissolving a carbon precursor and an inorganic salt in ultrapure water, except for a few of the research involving directly mixing and grinding the carbon precursor with a selected salt and then calcining the mixture, and thus drying the mixture is necessary thereafter. The solvent is generally evaporated to dryness by water bath drying or freeze drying, but both methods have their disadvantages. For water bath drying, thermal stress is inevitably generated in the drying process, so that cracks with different degrees appear in the finally obtained dried material, and the structure of the material is damaged; for freeze-drying, although thermal stress can be avoided and sublimation of ice crystals during drying can also create a macroporous structure, the drying time is too long (1-3 days) and the electric power cost is too high.
In addition, the high temperature carbonization process tends to result in a reduction of a large number of oxygen-containing functional groups, so that the carbon material lacks sufficient active sites, which greatly limits the practical application of porous carbon in the field of water treatment. For this reason, the present inventors have conducted intensive studies on functional modification of porous carbon materials, and among them, wet oxidation, i.e., immersing the carbon material in a strongly oxidizing solution such as nitric acid, sulfuric acid, hydrogen peroxide, etc., and refluxing for a certain period of time, is the most effective method. Although a large amount of oxygen-containing functional groups can be introduced in the method, the porous structure of the porous carbon can be obviously destroyed, and toxic and harmful gases can be emitted in the reflux treatment process.
Disclosure of Invention
In view of the above, the invention aims to provide a nitrogen-doped hollow hierarchical pore carbon microsphere with high oxygen content, and a preparation method and application thereof, so as to overcome the defects of the prior art.
The invention provides a preparation method of nitrogen-doped hollow hierarchical pore carbon microspheres with high oxygen content, which comprises the following steps:
(1) Uniformly mixing histidine, a salt template agent and a hydrochloric acid aqueous solution to obtain a precursor solution;
(2) Spray drying the precursor liquid to obtain hollow microspheres;
(3) Calcining the hollow microspheres to obtain a calcined product;
(4) And washing the calcined product with water to remove the template agent, thereby obtaining the nitrogen-doped hollow multistage pore carbon microsphere with high oxygen content.
Preferably, the top temperature of the spray drying process is 150-200 ℃.
Preferably, the pressure during the spray drying is 0.1 to 0.5kg/cm 2 The method comprises the steps of carrying out a first treatment on the surface of the The vibration frequency is 5-15 kHz; the amplitude is 10-20 Vpp.
Preferably, the calcination temperature is 600-1000 ℃.
Preferably, the total mass concentration of histidine and salt template in the precursor solution is 6-12 wt%.
Preferably, the salt templating agent is selected from potassium chloride and/or sodium chloride.
Preferably, the mass ratio of the histidine to the salt template agent is 1: (1-10).
Preferably, the hollow microspheres have a diameter of 85-95 μm.
The invention provides the nitrogen-doped hollow hierarchical pore carbon microsphere with high oxygen content, which is prepared by the method, and the specific surface area of the nitrogen-doped hollow hierarchical pore carbon microsphere is 695-1224 m 2 Per gram, pore volume of 0.33-0.70 cm 3 And/g, the oxygen content is 11.15-25.88 wt%.
In yet another aspect, the present invention provides an ozone oxidation catalyst comprising:
the nitrogen-doped hollow hierarchical pore carbon microsphere with high oxygen content prepared by the method of the technical scheme.
By means of the technical scheme, the invention has at least the following advantages:
the inorganic salt (such as sodium chloride or potassium chloride and the like) with high thermal stability used in the invention is a good coating agent, template agent and pore-forming agent; the carbon source can be limited in the gaps among salt grains stacked layer by layer in the whole calcination process, so that the thermal decomposition of the original oxygen-containing functional group can be inhibited to a certain extent; when the calcining temperature is below the melting temperature of the inorganic salt, it can exist as a structural template; when the calcination temperature exceeds its melting temperature, energetic ions from the molten salt may etch the carbon skeleton to create pores, thereby forming a multi-stage pore structure.
According to the invention, a spray drying technology is utilized, the conversion from atomized small liquid drops to dry microspheres is only within 2 seconds, and the limited-domain assembly of histidine and a salt template agent can be realized in the micro liquid drops in the drying process, so that histidine crystal particles coat salt grains, and meanwhile, the histidine crystal particles are limited to be among salt grains stacked layer by layer, thus the method has important effects on the maintenance of hollow spherical morphology, the improvement of specific surface area and oxygen content and the formation of a hierarchical pore structure.
Drawings
FIG. 1 is an SEM image of a spray-dried sample prepared according to example 1 of the invention;
FIG. 2 is an SEM image of a carbon material prepared according to example 1 of the present invention;
FIG. 3 is an SEM image of the carbon material prepared according to comparative example 1 of the present invention;
FIG. 4 shows N of the carbon materials prepared in examples 1 to 3 and comparative example 1 of the present invention 2 Adsorption and desorption isotherms and pore size distribution diagrams;
FIG. 5 shows the results of analysis of the elemental content of the carbon materials prepared in examples 1 to 3 and comparative example 1 of the present invention (analysis data obtained by quantitative analysis by a Thermo Fisher Scientific FlashSmart CHNS/O elemental analyzer);
FIG. 6 shows the results of the test of the carbon material prepared in examples 1 to 3 and comparative example 1 for catalyzing the oxidation of sodium oxalate by ozone;
FIG. 7 shows the physical and chemical properties of the carbon materials prepared in examples 2 and 5 of the present invention and the results of the test for catalyzing the oxidation of sodium oxalate by ozone.
Detailed Description
The following description of the technical solutions in the embodiments of the present invention will be clear and complete, and it is obvious that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention provides a preparation method of nitrogen-doped hollow hierarchical pore carbon microspheres with high oxygen content, which comprises the following steps:
(1) Uniformly mixing histidine, a salt template agent and a hydrochloric acid aqueous solution to obtain a precursor solution;
(2) Spray drying the precursor liquid to obtain hollow microspheres;
(3) Calcining the hollow microspheres to obtain a calcined product;
(4) And washing the calcined product with water to remove the template agent, thereby obtaining the nitrogen-doped hollow multistage pore carbon microsphere with high oxygen content.
In the present invention, the salt template is preferably selected from potassium chloride and/or sodium chloride.
In the present invention, the mass concentration of the aqueous hydrochloric acid solution is preferably 0 to 0.3wt% (excluding 0), more preferably 0.1 to 0.2wt%.
In the invention, the mass ratio of the histidine to the salt template agent is preferably 1: (1 to 10), more preferably 1: (2 to 8), more preferably 1: (4-8), most preferably 1: (5-6).
In the present invention, the total mass concentration of histidine and salt template in the precursor solution is preferably 6 to 12wt%, more preferably 7 to 9wt%, and most preferably 8wt%.
In the present invention, the method of mixing preferably comprises: histidine and salt template are dissolved in aqueous solution of hydrochloric acid for mixing.
In the present invention, the mixing is preferably performed under stirring; the temperature of the mixing is preferably room temperature, more preferably 20 to 30 ℃, most preferably 25 ℃.
In the present invention, the spray drying is preferably performed by breaking up the microfluidic aerosol nozzle into uniform droplets.
In the present invention, the temperature of the top of the tower in the spray drying process is preferably 150 to 200 ℃, more preferably 160 to 190 ℃, and most preferably 170 to 180 ℃; the pressure during spray drying is preferably from 0.1 to 0.5kg/cm 2 More preferably 0.2 to 0.4kg/cm 2 Most preferably 0.3kg/cm 2 The method comprises the steps of carrying out a first treatment on the surface of the The working vibration frequency of the atomizer is preferably 5-15 kHz, more preferably 8-12 kHz, and most preferably 10kHz; the amplitude is preferably 10 to 20Vpp, more preferably 13 to 17Vpp, most preferably 15Vpp; the flow rate of the hot air is preferably 250 to 350L/min, more preferably 280 to 320L/min, and most preferably 300L/min.
In the present invention, the hollow microspheres preferably have a diameter of 85 to 95. Mu.m, more preferably 88 to 92. Mu.m, and most preferably 90. Mu.m. In the invention, the particle size of the obtained hollow microspheres can be regulated and controlled by controlling the nozzle size and the air speed in the spray drying process.
In the present invention, as long as the spray-drying conditions are kept constant, the properties of the resulting dried microspheres remain unchanged; the spray drying device is very easy to operate, can continuously feed, has high drying speed and high yield, and is suitable for industrial mass production.
In the present invention, the calcination is preferably carried out by charging the spray-dried powder into a corundum ark and placing the corundum ark into a tube furnace.
In the present invention, the calcination is preferably performed in an inert atmosphere, preferably argon and/or nitrogen; the temperature of the calcination is preferably 600 to 1000 ℃, more preferably 700 to 950 ℃, more preferably 800 to 950 ℃, and most preferably 900 to 950 ℃; the calcination time is preferably 2 to 4 hours, more preferably 3 hours.
In the present invention, the temperature is preferably raised from room temperature to the calcination temperature (600 to 1000 ℃); the rate of the temperature increase is preferably 2 to 5℃per minute, more preferably 3 to 4℃per minute.
In the invention, the water washing is preferably carried out in a shaking table to remove the salt template agent by water washing and shaking; after the water washing is finished, the obtained water washing liquid is preferably dried to recover the salt template agent, so that the cyclic utilization of the salt template agent is realized; the drying method is preferably drying.
In the present invention, the method of washing with water preferably comprises: and soaking the calcined product in water for constant-temperature oscillation.
In the present invention, the water is preferably ultrapure water; the soaking is preferably performed in a glass vessel containing ultrapure water; the constant temperature oscillation is preferably performed in a constant temperature oscillator; the time of the constant temperature oscillation is preferably 2 to 4 hours, more preferably 3 hours.
In the present invention, the washing with water preferably further comprises: and filtering, washing and drying the product after water washing to obtain the nitrogen-doped hollow multistage pore carbon microsphere with high oxygen content.
In the invention, the filtering method is preferably vacuum filtration; the washing method is preferably washing with ultrapure water to thoroughly remove salt components in the carbon material; the drying temperature is preferably 50 to 70 ℃, more preferably 55 to 65 ℃, and most preferably 60 ℃; the drying method is preferably vacuum drying; more preferably overnight vacuum drying.
The invention provides the nitrogen-doped hollow hierarchical pore carbon microsphere with high oxygen content, which is prepared by the method; the specific surface area is preferably 695-1224 m 2 Preferably, the pore volume per gram is from 0.33 to 0.70cm 3 The oxygen content per gram is preferably from 11.15 to 25.88% by weight.
The invention provides an ozone oxidation catalyst, comprising:
the nitrogen-doped hollow hierarchical pore carbon microsphere with high oxygen content prepared by the method of the technical scheme.
In the present invention, the ozone oxidation catalyst may be used to catalyze an ozone oxidation reaction, such as catalyzing ozone to oxidize sodium oxalate.
The foregoing description is only an overview of the present invention, and is intended to provide a better understanding of the present invention, as it is embodied in the following description, with reference to the preferred embodiments of the present invention and the accompanying drawings. The following describes in further detail the embodiments of the present invention with reference to the drawings and examples. The following examples are illustrative of the invention and are not intended to limit the scope of the invention.
Example 1
Weighing 4g of histidine and 16g of potassium chloride, adding into 0.2wt% of HCl aqueous solution, and stirring for 3 hours at room temperature, wherein the total mass concentration of histidine and potassium chloride in the precursor solution is 8wt%;
pouring the precursor liquid into a polytetrafluoroethylene material tank, and crushing the precursor liquid in the material tank into uniform small liquid drops through a microfluidic aerosol nozzle by compressed air; spray drying the precursor solution under the conditions that the temperature of the tower top is 170 ℃ and the flow rate of hot air is 300L/min;
placing the collected dry powder into a corundum ark, then placing the corundum ark into a tube furnace for calcination, heating to the corresponding temperature of 950 ℃ at a heating rate of 2 ℃/min under argon atmosphere, and keeping for 3 hours; immersing the calcined sample in a glass container containing ultrapure water, placing the glass container into a constant temperature oscillator for shaking for 3 hours, vacuum-filtering and washing with a certain amount of ultrapure water to thoroughly remove salt components in the carbon material, and finally vacuum-drying the carbon material at 60 ℃ overnight to obtain the nitrogen-doped hollow multistage pore carbon microsphere with high oxygen content.
Fig. 1 shows SEM test results of a sample spray-dried in example 1 of the present invention, and it can be seen that diamond-shaped wrinkles appear on the surface of the obtained dried microsphere particles, which is caused by some crystal angular protrusions of potassium chloride, the microsphere particle size is mainly distributed between 85 and 95 μm, and the interior of the particles presents a hollow structure.
Fig. 2 shows SEM test results of nitrogen-doped hollow hierarchical pore carbon microspheres with high oxygen content obtained by calcining, washing and drying in example 1 of the present invention, and it can be seen that the particles calcined at 950 ℃ still maintain the original hollow spherical morphology well, and the surface and the interior of the particles are covered with diamond-shaped macropores.
Example 2
Nitrogen-doped hollow, multi-stage pore carbon microspheres with high oxygen content were prepared as in example 1, differing from example 1 in that the mass of histidine was 4g and the mass of potassium chloride was 24g.
Example 3
Nitrogen-doped hollow, multi-stage pore carbon microspheres with high oxygen content were prepared as in example 1, differing from example 1 in that the mass of histidine was 4g and the mass of potassium chloride was 32g.
Comparative example 1
A carbon material was prepared in the same manner as in example 1, except that potassium chloride was not added.
Fig. 3 is an SEM test result of the carbon material obtained in comparative example 1 after the calcination, water washing and drying processes, and it can be seen that the spherical morphology of the microsphere particles obtained by spray-drying pure histidine cannot be maintained after calcination at 950 ℃, and a compact lamellar structure is exhibited.
Performance detection
N was conducted on the carbon materials prepared in examples 1 to 3 of the present invention and comparative example 1 2 The adsorption and desorption isotherms and pore size distribution are detected by the following steps: obtained by testing at-196 c using a Micromeritics ASAP2020 instrument.
The test results are shown in FIG. 4 and the following table, S in the following table BET Refers to the specific surface area, V, of the material calculated according to the BET model total Is the pore volume of the material:
S BET (m 2 /g) V total (cm 3 /g)
example 1 1080 0.57
Example 2 1224 0.70
Example 3 958 0.50
Comparative example 1 470 0.22
As can be seen from fig. 4 and the above table, the use of potassium chloride as a salt template has a great promoting effect on the increase of the specific surface area of the carbon material and the generation of the hierarchical pore structure.
As a result of analyzing the elemental contents of the carbon materials prepared in examples 1 to 3 and comparative example 1, fig. 5 shows the elemental contents of the carbon materials prepared in examples 1 to 3 and comparative example 1, it can be seen that the introduction of potassium chloride suppresses the decomposition of the oxygen-containing functional group of the material, thereby increasing the oxygen content of the carbon material, compared with the oxygen content of the carbon material obtained without adding potassium chloride.
Example 4 catalytic ozone oxidation of sodium oxalate
The carbon materials prepared in examples 1 to 3 and comparative example 1 were used as catalysts for catalytic ozonation of sodium oxalate, and both ozone oxidation and catalytic ozonation were carried out in a semi-batch mode in a two-necked flask, and the specific method was as follows:
100mL of a 50ppm sodium oxalate solution and 20mg of a catalyst were added to the reactor while stirring with a magnetic stirrer; ozone is prepared from dry high-purity oxygen (18 mL/min) by an ozone generator, the concentration of gas phase ozone is 50ppm, and the ozone is continuously introduced into sodium oxalate solution; taking water sample in a certain time, immediately coating the water sample with a film, and then adding a quencher Na 2 S 2 O 3 The oxidation-reduction reaction in the water sample is stopped (ozone remaining in the water sample is quenched).
Determination of sodium oxalate content in water sample by ion chromatograph (ICS-600, siemens technologies Co., ltd.) with Na 2 CO 3 /NaHCO 3 The mobile phase was a mobile phase with a mobile phase velocity of 0.8mL/min.
Comparative example 2
The method of example 4 was followed to catalyze the ozonation of sodium oxalate, differing from example 4 in that no catalyst was added.
Fig. 6 is a graph of the degradation of sodium oxalate by catalytic ozonation of different carbon materials prepared in examples and comparative examples, wherein the degradation of sodium oxalate is obviously accelerated after the catalyst is added compared with that of sodium oxalate by ozone oxidation (comparative example 2), and the removal rate of sodium oxalate by ozone oxidation alone is increased to 74.7% from less than 10%, which shows that the nitrogen-doped hollow multistage pore carbon microsphere with high oxygen content prepared in the invention has good catalytic activity in catalyzing the degradation of sodium oxalate by ozone oxidation as a catalyst.
Example 5
Weighing 4g of histidine and 24g of potassium chloride, adding into 0.2wt% of HCl solution, and stirring for 3 hours at room temperature, wherein the total mass concentration of histidine and potassium chloride in the precursor solution is 8wt%;
subsequently, the solvent was removed using a rotary evaporator under a vacuum of 50mbar, the rotary flask was rotated at 60rpm and immersed in a water bath at 60℃and the resulting product was dried in an oven at 60℃overnight under vacuum to remove residual solvent;
the dried product was subjected to subsequent calcination, washing, drying, in the same manner as in example 1.
Fig. 7 is a graph of specific surface area and pore volume, element content, XRD diffractions, sodium oxalate degradation (test procedure and detection method as in example 4) of the nitrogen-doped carbon microspheres prepared in examples 2 and 5, and it can be seen that changing the drying mode does not affect the specific surface area and pore volume of the prepared carbon microspheres, but does not mean that the pore structures of the two are the same, because ASAP2020 equipment is not sensitive to detect macropores. Carbon microspheres prepared by rotary evaporation drying techniques have a higher degree of graphitization (as shown by XRD diffractograms) than carbon microspheres prepared by spray drying techniques, but have a lower oxygen content, and in the case of almost the same specific surface area and pore volume, the carbon material with a lower oxygen content has poorer catalytic properties, which not only indicates that the high oxygen content can promote the catalytic degradation of the carbon material, but also indicates the importance of spray drying techniques.
According to the invention, a spray drying technology is utilized, the conversion from atomized small liquid drops to dry microspheres only needs 0-2 s, and the limited-area assembly of histidine and a salt template agent can be realized in the micro liquid drops in the drying process, so that histidine crystal particles coat salt grains, and meanwhile, the histidine crystal particles are limited to be among salt grains stacked layer by layer, thus the method has important effects on the maintenance of hollow spherical morphology, the improvement of specific surface area and oxygen content and the formation of a hierarchical pore structure.
The above-described embodiments are merely preferred embodiments for fully explaining the present invention, and the scope of the present invention is not limited thereto. Equivalent substitutions and modifications will occur to those skilled in the art based on the present invention, and are intended to be within the scope of the present invention. The protection scope of the invention is subject to the claims.
While the invention has been described and illustrated with reference to specific embodiments thereof, the description and illustration is not intended to limit the invention. It will be apparent to those skilled in the art that various changes may be made in this particular situation, material, composition of matter, substance, method or process without departing from the true spirit and scope of the invention as defined by the following claims, so as to adapt the objective, spirit and scope of the present application. All such modifications are intended to be within the scope of this appended claims. Although the methods disclosed herein have been described with reference to particular operations being performed in a particular order, it should be understood that these operations may be combined, sub-divided, or reordered to form an equivalent method without departing from the teachings of the present disclosure. Thus, unless specifically indicated herein, the order and grouping of operations is not a limitation of the present application.

Claims (6)

1. A preparation method of nitrogen-doped hollow hierarchical pore carbon microspheres with high oxygen content comprises the following steps:
(1) Uniformly mixing histidine, a salt template agent and a hydrochloric acid aqueous solution to obtain a precursor solution;
(2) Spray drying the precursor liquid to obtain hollow microspheres;
(3) Calcining the hollow microspheres to obtain a calcined product;
(4) Washing the calcined product with water to remove a template agent, so as to obtain the nitrogen-doped hollow multistage pore carbon microsphere with high oxygen content;
the pressure in the spray drying process is 0.1-0.5 kg/cm 2 The method comprises the steps of carrying out a first treatment on the surface of the The vibration frequency is 5-15 kHz; amplitude is 10-20 Vpp;
the total mass concentration of histidine and salt template agent in the precursor solution is 6-12wt%;
the mass ratio of the histidine to the salt template agent is 1: (1-10);
the salt template is selected from potassium chloride and/or sodium chloride.
2. The method of claim 1, wherein the top temperature during the spray drying is 150-200 ℃.
3. The method of claim 1, wherein the calcination temperature is 600-1000 ℃.
4. The method of claim 1, wherein the hollow microspheres have a diameter of 85-95 μm.
5. A nitrogen-doped hollow hierarchical pore carbon microsphere with high oxygen content prepared by the method of claim 1, wherein the specific surface area is 695-1224 m 2 Per gram, pore volume of 0.33-0.70 cm 3 And/g, wherein the oxygen content is 11.15-25.88 wt%.
6. An ozone oxidation catalyst comprising: the nitrogen-doped hollow hierarchical pore carbon microsphere with high oxygen content prepared by the method of claim 1.
CN202210229951.0A 2022-03-10 2022-03-10 Nitrogen-doped hollow hierarchical pore carbon microsphere with high oxygen content and preparation method and application thereof Active CN114558603B (en)

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PCT/CN2022/087828 WO2023168800A1 (en) 2022-03-10 2022-04-20 Nitrogen-doped hollow hierarchically-porous carbon microsphere with high oxygen content, and preparation method therefor and use thereof

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