Metal-doped carbon material, preparation method and application thereof, and adsorption material and application thereof

Abstract

The present application relates to the technical field of carbon material preparation, in particular to a metal-doped carbon material, a preparation method and application thereof, and an adsorbing material. The method comprises the following steps: (1) mixing a carbon material precursor and an oxidizing agent, and pre-oxidizing the obtained mixture to obtain a pre-oxidized product; (2) under microwave and ultraviolet light irradiation, carbonizing and activating the pre-oxidized product and an activating agent in an inert gas atmosphere to obtain a carbonized and activated product; (3) immersing the carbonized and activated product in a soluble metal salt solution, and calcining the obtained immersion product to obtain a metal-doped carbon material; wherein the carbon material precursor is selected from coal chemical liquefaction residues and / or gasification furnace slag. The metal-doped carbon material obtained by the method has the characteristics of large specific surface area and small average pore size, and has excellent adsorption effect.

Description

Technical Field

[0001] This invention relates to the field of carbon material preparation technology, specifically to a metal-doped carbon material, its preparation method and application, and an adsorption material. Background Technology

[0002] Global warming has attracted increasing attention, and carbon emission reduction has also received more and more emphasis. CO2 adsorbents have low pollution, good regeneration efficiency, and no corrosion to equipment. Moreover, their precursors are widely available, making them a good carbon emission reduction technology with broad application prospects.

[0003] CN108963207A discloses a method for preparing porous metal-doped carbon. The method involves immersing radish slices in a metal ion solution of a certain concentration, then drying the immersed radish slices and performing carbonization-activation, ultimately synthesizing metal-doped carbon materials.

[0004] The paper "Potassium Tethered Carbons with Unparalleled Adsorption Capacity and Selectivity for Low-Cost Carbon Dioxide Capture from Flue Gas" (ACS Applied Materials & Interfaces 2018, 10, 3495) discloses a method for preparing a CO2 adsorbent suitable for CO2 capture in coal-fired power plants. This method first synthesizes mesoporous carbon materials, then oxidizes the mesoporous carbon with concentrated nitric acid and concentrated sulfuric acid, and then introduces the oxidized carbon materials into a KOH solution of a certain concentration for ion exchange, finally synthesizing a K-doped CO2 adsorbent. However, the synthesis process generates a large amount of waste nitric acid and waste sulfuric acid, which is not conducive to the promotion of the adsorbent.

[0005] The paper “SBiomass ash stabilized MgO adsorbents for CO2 capture application” (Fuel, 2020, 259, 116298) discloses a method for synthesizing CO2 adsorbent materials. The method involves impregnating sugarcane bagasse, coffee grounds, rice husks, and sawdust with a certain concentration of MgCl2·6H2O, and then calcining them at 600℃ for 2 hours to obtain CO2 adsorbents suitable for high-temperature conditions. However, the specific surface area of ​​the CO2 adsorbent is very small, making it unsuitable for CO2 adsorption under low-temperature conditions.

[0006] Therefore, there is an urgent need for a new method for preparing metal-doped carbon materials. Summary of the Invention

[0007] The purpose of this invention is to overcome the problems of complex processes, high costs, large amounts of waste liquid generated, and small specific surface area of ​​metal-doped carbon materials in the preparation process of existing technologies, which are not conducive to low-temperature adsorption of CO2. This invention provides a new metal-doped carbon material, its preparation method and application, and an adsorption material. The method uses coal chemical liquefaction residue and / or gasification slag as carbon material precursors to reduce costs. Simultaneously, this metal-doped carbon material has the characteristics of large specific surface area and small average pore size, exhibiting excellent adsorption performance.

[0008] To achieve the above objectives, the first aspect of the present invention provides a method for preparing a metal-doped carbon material, the method comprising the following steps:

[0009] (1) Mix the carbon material precursor and the oxidant, and pre-oxidize the resulting mixture to obtain the pre-oxidized product;

[0010] (2) The pre-oxidized product and the activator are carbonized and activated in an inert gas atmosphere under microwave and ultraviolet light irradiation to obtain a carbonized and activated product.

[0011] (3) The carbonization activation product is impregnated in a soluble metal salt solution, and the impregnated product is calcined to obtain a metal-doped carbon material;

[0012] The carbon material precursor is selected from coal chemical liquefaction residue and / or gasification slag.

[0013] The second aspect of the present invention provides a metal-doped carbon material prepared by the method provided in the first aspect.

[0014] A third aspect of the present invention provides an adsorbent material comprising the metal-doped carbon material provided in the second aspect.

[0015] The fourth aspect of this invention provides an application of the metal-doped carbon material provided in the second aspect, or the adsorption material provided in the third aspect, in the field of adsorption.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] (1) The method provided by the present invention uses coal chemical liquefaction residue and / or gasification furnace slag as carbon material precursor, and combines pre-oxidation, carbonization activation, impregnation and calcination processes to obtain metal-doped carbon materials with large specific surface area and small average pore size under the premise of reducing production costs; at the same time, the preparation process simplifies the process flow and does not generate a large amount of waste liquid.

[0018] (2) The metal-doped carbon material provided by the present invention has excellent adsorption effect, especially when the metal-doped carbon material is used to adsorb CO2 and / or VOCs, it has a high adsorption capacity. Detailed Implementation

[0019] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0020] The first aspect of this invention provides a method for preparing a metal-doped carbon material, the method comprising the following steps:

[0021] (1) Mix the carbon material precursor and the oxidant, and pre-oxidize the resulting mixture to obtain the pre-oxidized product;

[0022] (2) The pre-oxidized product and the activator are carbonized and activated in an inert gas atmosphere under microwave and ultraviolet light irradiation to obtain a carbonized and activated product.

[0023] (3) The carbonization activation product is impregnated in a soluble metal salt solution, and the impregnated product is calcined to obtain a metal-doped carbon material;

[0024] The carbon material precursor is selected from coal chemical liquefaction residue and / or gasification slag.

[0025] In some embodiments of the present invention, preferably, in step (1), the weight ratio of the carbon material precursor and the oxidant is 1:0.1-1, for example, 1:0.1, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:1, and any value in any range of any two values, preferably 1:0.3-0.7.

[0026] In some embodiments of the present invention, preferably, the coal chemical liquefaction residue is selected from direct coal liquefaction residue and / or indirect coal liquefaction residue.

[0027] In some embodiments of the present invention, preferably, the oxidant is selected from KNO3 and / or NaClO2.

[0028] In this invention, the pre-oxidation conditions have a wide range of selection. Preferably, in step (1), the pre-oxidation conditions include: a temperature of 180-350℃, more preferably 200-300℃; and a time of 0.1-5h, more preferably 1-3h. Using the preferred conditions is beneficial to improving the carbonization activation of the carbon material precursor.

[0029] In some embodiments of the present invention, preferably, the carbon material precursor is ground before the mixing; more preferably, the average particle size of the ground carbon material precursor is ≥40 mesh, and more preferably ≥100 mesh.

[0030] In some embodiments of the present invention, preferably, in step (2), the weight ratio of the pre-oxidized product to the activator is 1:0.2-5, for example, 1:0.2, 1:0.5, 1:1, 1:1.5, 1:2, 1:3, 1:4, 1:5, and any value in any range of any two values, preferably 1:0.5-2.

[0031] In some embodiments of the present invention, preferably, the activator is selected from at least one of KOH, K2CO3, KHCO3, NaOH, Na2CO3 and NaHCO3.

[0032] In some embodiments of the present invention, preferably, in step (2), the frequency of the microwave is 433MHz, 915MHz, 2450MHz, 5800MHz, or 22125MHz, preferably 915MHz or 2450MHz; the radiation intensity of the ultraviolet light is 50-500μW / cm². 2 Preferably 70-300 μW / cm 2 In this invention, different microwave and ultraviolet radiation intensities cause the material to undergo carbonization reactions of varying degrees of intensity.

[0033] In this invention, a wide range of types of inert gas can be selected. Preferably, the inert gas is selected from at least one of nitrogen, helium, argon, and neon, with nitrogen being the most preferred.

[0034] In this invention, the carbonization activation is a process of forming fixed carbon from a carbon source at high temperature and activating the fixed carbon. Preferably, the conditions for the carbonization activation include: a temperature of 500-1000℃, more preferably 600-900℃; and a time of 0.5-4h, more preferably 1-2h.

[0035] In some embodiments of the present invention, preferably, in step (3), the concentration of metal ions in the soluble metal salt solution is 0.1-5 mol / L, for example, 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 3 mol / L, 5 mol / L, and any value within the range of any two values, preferably 0.5-2 mol / L.

[0036] In this invention, unless otherwise specified, solubility refers to being easily soluble in water or being easily soluble in water with the aid of additives.

[0037] In some embodiments of the present invention, the soluble metal salt in the soluble metal salt solution is selected from at least one of nitrates, chlorates, and sulfates; the metal in the soluble metal salt is selected from at least one of Mg, Cu, and Fe. In the present invention, the soluble metal salt includes, but is not limited to, magnesium nitrate, magnesium chlorate, magnesium sulfate, copper nitrate, copper chlorate, copper sulfate, ferric nitrate, ferric chlorate, and ferric sulfate.

[0038] In this invention, the calcination is intended to sinter the impregnated product at high temperature to obtain a metal-doped carbon material. Preferably, the calcination conditions include: a temperature of 300-700℃, more preferably 450-650℃; and a time of 0.1-10h, more preferably 1-5h.

[0039] In some embodiments of the present invention, preferably, the method further includes: before the impregnation, sequentially acid washing and water washing of the carbonized activated product.

[0040] In some embodiments of the present invention, preferably, the pickling process includes: pickling the carbonization activation product and acid solution to obtain the pickled product.

[0041] In some embodiments of the present invention, preferably, the concentration of acid in the acid solution is 0.1-5 mol / L, for example, 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, and any value within any range of any two values, preferably 0.5-2 mol / L; more preferably, the acid is an inorganic acid, preferably selected from at least one of hydrochloric acid, nitric acid, and sulfuric acid.

[0042] In this invention, unless otherwise specified, the water washing is intended to remove residual acid from the pickling product until the water washing product is neutral.

[0043] According to a particularly preferred embodiment of the present invention, a method for preparing a metal-doped carbon material is characterized by comprising the following steps:

[0044] (1) Mix the carbon material precursor and the oxidant, and pre-oxidize the resulting mixture to obtain the pre-oxidized product;

[0045] (2) The pre-oxidized product and the activator are carbonized and activated in an inert gas atmosphere under microwave and ultraviolet light irradiation to obtain a carbonized and activated product.

[0046] (3) The carbonization activation product is impregnated in a soluble metal salt solution, and the impregnated product is calcined to obtain a metal-doped carbon material;

[0047] The carbon material precursor is selected from coal chemical liquefaction residue and / or gasification slag;

[0048] In step (2), the frequency of the microwave is 915MHz or 2450MHz; the radiation intensity of the ultraviolet light is 70-300μW / cm². 2 .

[0049] The second aspect of the present invention provides a metal-doped carbon material prepared by the method provided in the first aspect.

[0050] According to the present invention, preferably, the amount of metal doping is 0.1-5 wt%, for example, 0.1 wt%, 0.2 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 5 wt%, and any value within any range of any two values, based on the total weight of the metal-doped carbon material, preferably 0.2-3 wt%.

[0051] According to the present invention, preferably, the specific surface area of ​​the metal-doped carbon material is ≥800 m². 2 / g, preferably ≥1000m 2 / g; average pore size ≤3nm, preferably ≤2.5nm.

[0052] In this invention, unless otherwise specified, the specific surface area parameter and the average pore size parameter are measured using a BET analyzer with the N2 isothermal adsorption method.

[0053] A third aspect of the present invention provides an adsorbent material comprising the metal-doped carbon material provided in the second aspect.

[0054] In this invention, unless otherwise specified, the adsorbent material can be the metal-doped carbon material provided by this invention, or it can contain other components in addition to the metal-doped carbon material provided by this invention, which will not be elaborated here.

[0055] The fourth aspect of this invention provides an application of the metal-doped carbon material provided in the second aspect, or the adsorption material provided in the third aspect, in the field of adsorption.

[0056] The metal-doped carbon material provided by this invention has a large specific surface area and abundant pore structure, and has a high adsorption effect in the adsorption field, especially for adsorbing CO2 and / or VOCs, with a large adsorption capacity.

[0057] The present invention will be described in detail below through embodiments.

[0058] The physical properties of the metal-doped carbon materials (S1-S6 and D1-D4) prepared in Examples 1-6 and Comparative Examples 1-4 are listed in Table 1.

[0059] Example 1

[0060] (1) Mix 5g of ground carbon material precursor (coal direct liquefaction residue with an average particle size of 100 mesh) and 3g of oxidant (KNO3), and pre-oxidize the mixture at 300℃ for 1h to obtain the pre-oxidized product;

[0061] (2) At a microwave frequency of 2450MHz and a radiation intensity of 150μW / cm 2 Under ultraviolet light irradiation, the above pre-oxidized product and activator (KOH) were carbonized and activated at 800℃ for 2 hours in a nitrogen atmosphere at a weight ratio of 1:1 to obtain the carbonized and activated product.

[0062] (3) The above carbonization activation product and hydrochloric acid solution with a concentration of 0.5 mol / L were acid-washed to obtain the acid-washed product. The product was washed with water until neutral and then immersed in MgCl2 solution with a concentration of 1 mol / L for 1 h. The immersed product was calcined at 600℃ for 1 h to obtain metal-doped carbon material S1.

[0063] Example 2

[0064] (1) Mix 5g of ground carbon material precursor (coal indirect liquefaction residue with an average particle size of 100 mesh) and 3.5g of oxidant (KNO3), and pre-oxidize the mixture at 200℃ for 3h to obtain the pre-oxidized product;

[0065] (2) At a microwave frequency of 2450MHz and a radiation intensity of 300μW / cm 2 Under ultraviolet light irradiation, the above pre-oxidized product and activator (KOH) were carbonized and activated at a temperature of 900℃ for 1 hour in a nitrogen atmosphere at a weight ratio of 1:2 to obtain the carbonized and activated product.

[0066] (3) The above carbonization activation product and hydrochloric acid solution with a concentration of 1 mol / L were acid-washed to obtain the acid-washed product. The product was washed with water until neutral and then immersed in Mg(NO3)2 solution with a concentration of 0.5 mol / L for 1 h. The immersed product was calcined at 700℃ for 2 h to obtain metal-doped carbon material S2.

[0067] Example 3

[0068] (1) Mix 5g of ground carbon material precursor (gasification slag, average particle size of 200 mesh) and 1.5g of oxidant (KNO3), and pre-oxidize the mixture at 250℃ for 2h to obtain the pre-oxidized product;

[0069] (2) At a microwave frequency of 2450MHz and a radiation intensity of 70μW / cm 2Under ultraviolet light irradiation, the above pre-oxidized product and activator (KOH) were carbonized and activated at a temperature of 600℃ for 2 hours in a nitrogen atmosphere at a weight ratio of 1:0.5 to obtain the carbonized and activated product.

[0070] (3) The above carbonization activation product and hydrochloric acid solution with a concentration of 1 mol / L were acid washed to obtain the acid-washed product. The product was then washed with water until neutral and then immersed in Mg(NO3)2 solution with a concentration of 2 mol / L for 1 h. The immersed product was then calcined at 900℃ for 1.5 h to obtain metal-doped carbon material S3.

[0071] Example 4

[0072] The method of Example 1 is different except that in step (1), 5g of ground carbon material precursor (coal direct liquefaction residue with an average particle size of 100 mesh) and 3g of oxidant (KNO3) are replaced with 5g of ground carbon material precursor (coal direct liquefaction residue with an average particle size of 100 mesh) and 1g of oxidant (KNO3), while the other conditions are the same, and metal-doped carbon material S4 is obtained.

[0073] Example 5

[0074] The method of Example 1 is followed, except that in step (2), the weight ratio of the above pre-oxidized product and activator (KOH) is replaced with 1:3, and the other conditions are the same, to obtain metal-doped carbon material S5.

[0075] Example 6

[0076] The method of Example 1 is followed, except that in step (2), the carbonization activation conditions are replaced with a temperature of 500°C and a time of 4 hours, while the other conditions remain the same, to obtain metal-doped carbon material S6.

[0077] Comparative Example 1

[0078] The method of Example 1 is different except that in step (1), 5g of ground carbon material precursor (coal direct liquefaction residue with an average particle size of 100 mesh) is replaced with 5g of coal powder, and the other conditions are the same, to obtain metal-doped carbon material D1.

[0079] Comparative Example 2

[0080] The method of Example 1 is different except that step (1) is omitted, in which the ground carbon material precursor (coal direct liquefaction residue with an average particle size of 100 mesh) is directly carbonized and activated with activator (KOH) at a weight ratio of 1:1, while the other conditions are the same, to obtain metal-doped carbon material D2.

[0081] Comparative Example 3

[0082] The method of Example 1 is different except that in step (2), there is no microwave and ultraviolet light. In a nitrogen atmosphere, the above pre-oxidized product and activator (KOH) are directly carbonized and activated at 800°C for 2 hours in a weight ratio of 1:1. The other conditions are the same, and metal-doped carbon material D3 is obtained.

[0083] Comparative Example 4

[0084] The method of Example 1 is different except that in step (2), the microwave with a frequency of 2450MHz is replaced with electric heating of a tubular furnace with the same frequency, and the rest of the conditions are the same, so that metal-doped carbon material D4 is obtained.

[0085] Table 1

[0086]

[0087]

[0088] The results in Table 1 show that the metal-doped carbon materials prepared by using coal chemical liquefaction residue and / or gasification slag as carbon material precursors have the characteristics of large specific surface area and small average pore size. In particular, by limiting the weight ratio of carbon material precursor to oxidant, the weight ratio of pre-oxidation product to activator, and the carbonization activation conditions within the preferred protection range, it is more conducive to optimizing the relevant properties (high specific surface area and low average pore size) of the metal-doped carbon materials.

[0089] Test Example 1

[0090] The metal-doped carbon materials (S1-S6 and D1-D4) prepared in Examples 1-6 and Comparative Examples 1-4 were subjected to CO2 adsorption at 40°C. The CO2 adsorption amounts are listed in Table 2. The CO2 adsorption amounts were measured using a thermogravimetric analyzer.

[0091] Test Example 2

[0092] The metal-doped carbon materials (S1-S6 and D1-D4) prepared in Examples 1-6 and Comparative Examples 1-4 were subjected to benzene adsorption at 25 °C. The amount of benzene adsorbed is listed in Table 2. The amount of benzene adsorbed was determined by a fixed-bed breakthrough test.

[0093] Table 2

[0094]

[0095]

[0096] As shown in Table 2, compared with Comparative Examples 1-4, the adsorbent material prepared by the metal-doped carbon material provided by the present invention has a better adsorption effect on CO2 and also shows a good adsorption effect on VOCs gases such as benzene.

[0097] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a metal-doped carbon material, characterized in that, The method includes the following steps: (1) Mix the carbon material precursor and the oxidant, and pre-oxidize the resulting mixture to obtain the pre-oxidized product; (2) The pre-oxidized product and the activator are carbonized and activated in an inert gas atmosphere under microwave and ultraviolet light irradiation to obtain the carbonized and activated product; (3) The carbonization activation product is impregnated in a soluble metal salt solution, and the resulting impregnated product is calcined to obtain a metal-doped carbon material; The carbon material precursor is selected from coal chemical liquefaction residue and / or gasification slag; The oxidant is selected from KNO3 and / or NaClO2, and the weight ratio of the carbon material precursor to the oxidant is 1:0.3-0.7; the pre-oxidation conditions include: a temperature of 200-300℃ and a time of 1-3h. The weight ratio of the pre-oxidized product to the activator is 1:0.5-2; the microwave frequency is 915MHz or 2450MHz; and the ultraviolet radiation intensity is 70-300 µW / cm². 2 ; The carbonization activation conditions include: a temperature of 600-900℃; a time of 1-2 hours; and a heating rate of 3-5℃ / min.

2. The method according to claim 1, wherein, In step (1), The coal chemical liquefaction residue is selected from direct coal liquefaction residue and / or indirect coal liquefaction residue.

3. The method according to claim 1, wherein, In step (1), the carbon material precursor is ground before the mixing; The average particle size of the ground carbon material precursor is ≥40 mesh.

4. The method according to claim 3, wherein, In step (1), the average particle size of the ground carbon material precursor is ≥100 mesh.

5. The method according to claim 1, wherein, In step (2), The activator is selected from at least one of KOH, K2CO3, KHCO3, NaOH, Na2CO3 and NaHCO3.

6. The method according to claim 1, wherein, In step (3), the concentration of metal ions in the soluble metal salt solution is 0.1-5 mol / L; And / or, in the soluble metal salt solution, the soluble metal salt is selected from at least one of nitrates, chlorates and sulfates; the metal in the soluble metal salt is selected from at least one of Mg, Cu and Fe.

7. The method according to claim 6, wherein, In step (3), the concentration of metal ions in the soluble metal salt solution is 0.5-2 mol / L.

8. The method according to any one of claims 1-7, wherein, In step (3), the calcination conditions include: a temperature of 300-700℃ and a time of 0.1-10h; And / or, the method further includes: prior to the impregnation, sequentially acid washing and water washing of the carbonized activated product.

9. The method according to claim 8, wherein, In step (3), the calcination conditions include: a temperature of 450-650℃ and a time of 1-5 hours; And / or, the pickling process includes: pickling the carbonized activated product with an acid solution; The concentration of acid in the acid solution is 0.1-5 mol / L; The acid mentioned is an inorganic acid.

10. The method according to claim 9, wherein, The concentration of acid in the acid solution is 0.5-2 mol / L; The acid is selected from at least one of hydrochloric acid, nitric acid, and sulfuric acid.

11. The metal-doped carbon material prepared by the method according to any one of claims 1-10.

12. The metal-doped carbon material according to claim 11, wherein, Based on the total weight of the metal-doped carbon material, the metal doping amount is 0.1-5 wt%; And / or, the specific surface area of ​​the metal-doped carbon material is ≥800 m². 2 / g; average pore size ≤3 nm.

13. The metal-doped carbon material according to claim 12, wherein, Based on the total weight of the metal-doped carbon material, the metal doping amount is 0.2-3 wt%; And / or, the specific surface area of ​​the metal-doped carbon material is ≥1000 m² 2 / g; average pore size ≤2.5 nm.

14. An adsorbent material, characterized in that, The adsorbent material contains the metal-doped carbon material as described in any one of claims 11-13.

15. The application of the metal-doped carbon material according to any one of claims 11-13, or the adsorbent material according to claim 14, in the field of adsorption.

16. The application according to claim 15, wherein, The application of the metal-doped carbon material, or the adsorbent material, in the adsorption of CO2 and VOCs.

Images