Metal self-supported carbon material as well as preparation method and application thereof

Abstract

The invention provides a preparation method of a metal self-supported carbon material, which comprises the following steps: (1) taking coal or a biomass material as a raw material for providing active metal elements and a carbon material, and crushing and screening to obtain a raw material sample; (2) mixing the obtained raw material sample with a nitric acid solution, and then performing hydrothermal treatment in a microwave hydrothermal kettle to obtain a carbon material precursor; and (3) after the carbon material precursor is molded, carrying out in-situ drying, carbonization and activation to prepare the metal self-supported carbon material. The method disclosed by the invention has the advantages of simplicity in operation, low energy consumption and the like, the raw materials are wide in source, low in price and relatively low in cost, and the obtained metal self-supported carbon material is rich in pore structure and excellent in catalytic performance.

Description

Technical Field

[0001] The present invention relates to the field of carbon materials, and in particular to a metal self-supporting carbon material and a preparation method and application thereof. Background Art

[0002] Carbon materials are widely used in gas purification, wastewater purification, catalytic reforming, and other fields. For example, carbon materials can be used to catalytically reform tar gas and control the reaction direction; carbon materials can be used to purify wastewater; and the adsorption properties of activated coke can be used to react SO2 in flue gas with water and oxygen to form sulfuric acid, which is then adsorbed on the surface of the activated coke, achieving gas purification. Modification of carbon materials with active metals can further enhance their performance.

[0003] CN103224235A uses pulverized coal as raw material and prepares powdered activated coke for desulfurization through rapid reaction with flue gas. The specific steps include: extracting flue gas with a temperature of 200-800°C from a boiler as feed air for carrying pulverized coal, sending it into an entrained flow rapid reaction furnace, mixing it with the reaction gas for rapid reaction, and then separating it through a separator to obtain powdered activated coke with desulfurization performance and reducing combustible gas.

[0004] CN102745686B crushes the raw bituminous coal A and bituminous coal B into a particle size of 180-325 mesh; the ground raw bituminous coal A and bituminous coal B are uniformly mixed with coal tar in proportion, and then heated at 800-1000 kgf / cm 2 The carbonized material is extruded into carbon strips under a high pressure and air-dried and aged; the aged carbon strips are carbonized to generate carbonized material, the final carbonization temperature is 400-700°C, the carbonization time is 30-60 minutes, and the heating rate is 2-8 minutes / °C; the carbonized material is activated by passing water vapor, the activation temperature is 800-900°C, the activation time is 30-90 minutes, and the product is obtained. CN102491323B crushes raw coal and mixes it with a catalyst in a mass ratio of 60-80:1-2 to produce composite coal powder. The composite coal powder and a binder in a mass ratio of 61-82:5-25 are mixed at 40-80°C for 3-12 minutes to obtain a mixture, which is then mixed with water in a mass ratio of 66-107:8-25. The mixture is then pressed into shape using a flat die rolling molding machine at a pressure of 8-30 MPa to obtain formed coke. The formed coke is then dried at 90-125°C for 0.5-2.5 hours to obtain formed charcoal. The formed charcoal is then carbonized in a rotary kiln or a Sterk at a carbonization temperature of 300-750°C, activated in the rotary kiln or Sterk at an activation temperature of 800-1000°C, and activated in a Sterk furnace for 24-72 hours or in a horizontal rotary kiln for 1-3 hours. The post-treated activated coke is then cooled and screened.

[0005] CN101538037B extrude anthracite particles into carbon bars, carbonize the aged carbon bars to obtain a carbonized product, and activate the carbonized product using a steam activation method at an activation temperature of 800-850° C. for 30-50 minutes to obtain activated coke.

[0006] The process of preparing carbon materials in the above-mentioned disclosed technology is complicated and requires additional addition of metal solution when loading metal, which wastes metal resources and is expensive.

[0007] Therefore, it is necessary to develop a method for preparing metal-loaded carbon materials with simple process, low energy consumption and low cost. Summary of the Invention

[0008] In order to solve the above technical problems, the present invention provides a method for preparing metal self-supported carbon materials. The method has the advantages of simple operation and low energy consumption. The raw materials are widely available and cheap, and the cost is relatively low. The obtained metal self-supported carbon materials have rich pore structures and excellent catalytic properties.

[0009] The basic concept of the technical solution adopted in the present invention is as follows: A method for preparing a metal self-supporting carbon material comprises the following steps: Coal or biomass materials are used as raw materials for providing active metal elements and carbon materials, which are crushed and screened to obtain raw material samples; The obtained raw material sample is mixed with a nitric acid solution, and then subjected to hydrothermal treatment in a microwave hydrothermal reactor to obtain a carbon material precursor; After the carbon material precursor is formed, it is dried, carbonized and activated in situ to obtain the metal self-supporting carbon material.

[0010] As one approach, the raw material sample has a particle size of less than 0.075 mm.

[0011] As one approach, the concentration of the nitric acid solution is 5 to 15 mol / L.

[0012] As a method, the hydrothermal treatment conditions in the microwave hydrothermal reactor are: 200-300 °C, constant temperature for 4-5 hours.

[0013] As one approach, in-situ drying, carbonization, and activation are performed in a mixed atmosphere of CO2 and H2O at 800-1000°C for 3-6 hours.

[0014] In one embodiment, the biomass material is corn cobs or straw; and the coal is lignite.

[0015] As a method, in a mixed atmosphere of CO2 and H2O, the volume fraction of CO2 is 30%~80%, and the volume fraction of H2O is 20%~70%.

[0016] The present invention also provides a metal self-supporting carbon material, which is prepared by any of the methods described above.

[0017] The present invention further provides the use of the metal self-supported carbon material as described above, that is, the metal self-supported carbon material is used for gas purification, sewage purification or catalytic reforming.

[0018] Compared with the prior art, the present invention has the following advantages: 1. The present invention utilizes the alkali metals, alkaline earth metals and carbon matrix contained in coal and biomass. The ground carbon-containing material is mixed with a nitric acid solution and then heated to a constant temperature in a hydrothermal kettle. The nitric acid solution is used to activate the metal and carbon materials in the coal or biomass. The strong oxidizing property of nitric acid can oxidize the surface of carbon sites in coal or biomass to increase functional groups, which serve as metal exchange active sites, promote in situ ion exchange between dissolved metals and carbon materials, and the acid dissolves the metal and expands the pore structure of the carbon material, thereby improving the adsorption performance of the carbon material.

[0019] 2. In the metal self-loaded carbon material prepared by the present invention, the ratio of metal to carbon material is closely related to the coal or biomass raw material itself, and the metal and carbon matrix contained in the coal or biomass itself are fully utilized. The metal stored in the raw material is generally in an inert state, and the metal is activated under acid, hydrothermal and other conditions to improve its reaction activity.

[0020] 3. The metal self-supported carbon material prepared by the present invention has a total metal content of (0.5-4) wt.%, including K, Na, Ca, Mg and Fe, and has a rich pore structure and excellent catalytic performance.

[0021] 4. The method of the present invention does not require the use of complex equipment, is simple to operate, has low energy consumption, and the coal or biomass materials are widely available and inexpensive, so the cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings are used to provide a further understanding of the technical solution of the present invention and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present invention and do not constitute a limitation on the technical solution of the present invention.

[0023] Figure 1 1 is a pore size distribution diagram of the metal self-supported carbon materials prepared in Example 1, Example 2 and Example 3.

[0024] Figure 2This is a graph showing the change in the light aromatic hydrocarbon peak area after the metal self-supported carbon materials prepared in Examples 1, 2 and 3 are used in the catalytic reforming process of coal pyrolysis tar. DETAILED DESCRIPTION

[0025] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] Example 1 Metal self-supported carbon materials are prepared using lignite as raw material.

[0027] (1) After grinding the lignite, screen the coal samples with a particle size less than 0.075 mm.

[0028] (2) A 15 mol / L nitric acid solution was mixed with 10 g of coal sample, where the mass fraction of coal was 10%, and stirred evenly. The mixture was heated to 210 °C in a microwave hydrothermal reactor and kept at this temperature for 4 h.

[0029] (3) After the reaction is completed, the mixture is cooled and pre-dried at 105°C. The pre-dried solid material is extruded and then in situ carbonized and activated at 1000°C for 3.5 h in a mixed atmosphere of CO2 (30 v%) and H2O (70 v%) to obtain a metal self-supported carbon material.

[0030] Example 2 Metal self-supported carbon materials were prepared using corn cobs as biomass raw materials.

[0031] (1) Corn cobs were selected as raw materials, and the part with a particle size less than 0.075 mm was crushed, ground, and screened as corn cob samples.

[0032] (2) 8 mol / L nitric acid solution was mixed with 20 g corn cob sample and stirred evenly, where the mass fraction of corn cob was 20%. The mixture was heated to 260°C in a microwave hydrothermal reactor and kept at this temperature for 5 h.

[0033] (3) After the reaction is completed, the mixture is cooled and dried, and the solid material containing water is extruded and formed. After in-situ carbonization and activation at 800 °C for 6 h in a mixed atmosphere of CO2 (60 v%) and H2O (40 v%), a metal self-supported carbon material is obtained.

[0034] Example 3 Metal self-supported carbon materials are prepared using straw as raw material.

[0035] (1) Straw was selected as the raw material, and the particles with a size less than 0.075 mm were crushed, ground and screened to form straw samples.

[0036] (2) 15 g of straw sample was mixed with 11 mol / L nitric acid solution and stirred evenly, with the mass fraction of straw being 30%. The mixture was heated to 290°C in a microwave hydrothermal reactor and kept at this temperature for 4.5 h.

[0037] (3) After the reaction is completed, the mixture is cooled and dried, and the solid material containing water is extruded and formed. After in-situ drying, carbonization and activation at 900 °C for 5 h in a mixed atmosphere of CO2 (80 v%) and H2O (20 v%), a metal self-supported carbon material is obtained.

[0038] Effect Examples The pore structure of the carbon material was analyzed using a fully automatic physical adsorption instrument. The adsorbent was nitrogen and the adsorption temperature was -196°C. Before the measurement, the sample was vacuum treated at 300°C for 7 hours to remove impurities in the sample. The pore size distribution was determined using the DFT method. Figure 1 shown.

[0039] The metal self-supporting carbon materials prepared in Examples 1, 2, and 3 above all have rich pore structures, exhibiting a multi-level pore structure. Furthermore, the metal contents of the carbon materials prepared in Examples 1, 2, and 3 were found to be 1.6%, 2.1%, and 3.3%, respectively.

[0040] The loaded carbon material prepared as above was used in the catalytic reforming process of coal pyrolysis tar: the performance of the metal self-loaded carbon material was investigated by pyrolysis-gas chromatography / mass spectrometry. 1 mg of coal and 0.6 mg of carbon material were separated by quartz wool. The reaction temperature was set to 700°C. The volatile matter produced by the in-situ pyrolysis of coal passed through the metal self-loaded carbon material. The mesoporous structure and active metal of the metal self-loaded carbon material cracked the heavy aromatic hydrocarbons therein and converted them into light aromatic hydrocarbons such as benzene, toluene, xylene and naphthalene. The gas chromatography / mass spectrometry can detect each product online, and finally the peak area of ​​light aromatic hydrocarbons such as benzene, toluene, xylene and naphthalene was obtained.

[0041] Compared with the pyrolysis of raw coal, after the metal self-supported carbon materials prepared in Example 1, Example 2, and Example 3 acted on the products, the light aromatic hydrocarbons such as benzene, toluene, xylene, and naphthalene increased by 114%, 125%, and 148%, respectively. Figure 2 shown.

[0042] Although the embodiments disclosed herein are as described above, the contents described herein are merely embodiments for facilitating understanding of the present invention and are not intended to limit the present invention. Any person skilled in the art may make any modifications and variations in the form and details of the embodiments without departing from the spirit and scope of the present invention. However, the scope of patent protection of the present invention shall remain subject to the scope defined by the appended claims.

Claims

1. A method for preparing a metal self-supporting carbon material, characterized in that: The steps include: (1) Using coal or biomass materials as raw materials for providing active metal elements and carbon materials, crushing and screening to obtain raw material samples; (2) mixing the obtained raw material sample with a nitric acid solution, and then performing a hydrothermal treatment in a microwave hydrothermal reactor to obtain a carbon material precursor; (3) After the carbon material precursor is formed, it is dried, carbonized and activated in situ to obtain the metal self-supporting carbon material.

2. The method for preparing the metal self-supporting carbon material according to claim 1, characterized in that: The particle size of the raw material sample is less than 0.075 mm.

3. The method for preparing the metal self-supporting carbon material according to claim 1, characterized in that: The concentration of the nitric acid solution is 5 to 15 mol / L.

4. The method for preparing the metal self-supporting carbon material according to claim 1, characterized in that: The hydrothermal treatment conditions in the microwave hydrothermal reactor are: 200-300 °C, constant temperature for 4-5 hours.

5. The method for preparing the metal self-supporting carbon material according to claim 1, characterized in that: The method for in-situ drying, carbonization and activation is: treating for 3 to 6 hours in a mixed atmosphere of CO2 and H2O at 800 to 1000°C.

6. The method for preparing the metal self-supporting carbon material according to claim 1, characterized in that: The biomass material is corn cob or straw; the coal is lignite.

7. The method for preparing the metal self-supporting carbon material according to claim 5, characterized in that: In the mixed atmosphere of CO2 and H2O, the volume fraction of CO2 is 30%~80%, and the volume fraction of H2O is 20%~70%.

8. A metal self-supporting carbon material, characterized in that: Prepared by the method described in any one of claims 1 to 7.

9. The use of the metal self-supporting carbon material according to claim 8, characterized in that: The metal self-supported carbon material is used for gas purification, sewage purification or catalytic reforming.

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