A pitch-based carbon foam and a method for making the same

Abstract

The present application belongs to the technical field of coal chemical industry, petroleum chemical industry and carbon material, and particularly relates to a pitch-based foam carbon and a preparation method thereof. The preparation method comprises the following steps: (S1) impregnating polyurethane foam in a phenol formaldehyde resin solution, and then drying to obtain polyurethane modified foam; (S2) dissolving pitch in an organic solvent to form a pitch solution; (S3) impregnating the polyurethane modified foam in the pitch solution, and then drying to obtain pitch-loaded polyurethane modified foam; (S4) oxidizing and curing the pitch-loaded polyurethane modified foam to obtain a composite foam; and (S5) performing carbonization treatment on the composite foam to obtain pitch-based foam carbon. The present application utilizes coal direct liquefaction residue to prepare high-value-added foam carbon, and the obtained foam carbon has the advantages of high porosity, low density and high mechanical strength.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of coal chemical industry, petroleum chemical industry and carbon material, and particularly relates to a pitch-based foam carbon and a preparation method thereof. BACKGROUND

[0002] Under the context of global energy shortage, coal direct liquefaction technology as an important means of clean utilization of coal, the efficient utilization of its by-product, coal direct liquefaction residue (DCLR), becomes the key to improve the comprehensive utilization rate of coal resources. DCLR is rich in unconverted organic matter, which provides the possibility for the preparation of high value-added materials.

[0003] Foam carbon, as a kind of porous carbon material, has shown application potential in many fields due to its unique foam-like structure and excellent performance. However, the traditional foam carbon preparation methods such as supercritical foaming method have problems such as uneven pore structure, performance decline caused by inorganic interference when using DCLR. Although the template method can improve the pore structure, the mechanical strength of the prepared foam carbon still needs to be improved.

[0004] Considering that porosity and mechanical strength are the core indicators of the performance of foam carbon. High porosity is crucial for enhancing adsorption capacity and reducing material density, and is suitable for applications such as gas storage and pollutant capture; while high mechanical strength is the basis for applications as structural materials and catalyst carriers. Therefore, it is particularly important to develop a foam carbon that can combine DCLR resources and has high porosity and high mechanical strength. SUMMARY

[0005] The purpose of the present application is to solve the problems of uneven pore structure and insufficient mechanical performance of foam carbon mentioned in the background, and to provide a preparation method of foam carbon with high porosity, low density and high mechanical strength.

[0006] To achieve the above-mentioned purpose, the first aspect of the present application provides a preparation method of pitch-based foam carbon, comprising the following steps:

[0007] (S1) impregnating polyurethane foam in a phenol formaldehyde resin ethanol solution, and then drying to obtain polyurethane modified foam;

[0008] (S2) dissolving pitch in an organic solvent to form a pitch solution;

[0009] (S3) impregnating the polyurethane modified foam in the pitch solution, and then drying to obtain pitch-loaded polyurethane modified foam;

[0010] (S4) oxidizing and curing the pitch-loaded polyurethane modified foam to obtain a composite foam;

[0011] (S5) carbonizing the composite foam to obtain the pitch-based foam carbon.

[0012] The second aspect of the present application provides a pitch-based foam carbon obtained by the above preparation method.

[0013] Compared with the prior art, the present application has the following beneficial effects:

[0014] Firstly, the present application increases the adsorption amount of the template to the pitch solution by chemically modifying the template; meanwhile, the two-step impregnation, oxidation curing and high-temperature carbonization steps increase the mechanical strength of the pitch-based foam carbon, so that the pitch-based foam carbon of the present application has high mechanical strength on the basis of high open porosity and low density.

[0015] Secondly, the present application obtains a pitch-based foam carbon with adjustable pore structure, density and compressive strength by adjusting the pore size of the polyurethane foam template, the concentration of the pitch solution and the carbonization conditions. DETAILED DESCRIPTION

[0016] The present application will be further described below through specific examples, and the examples described in the present application are only used to illustrate the present application and do not mean that the scope of the present application is limited to the examples.

[0017] The preparation method of the pitch-based foam carbon provided by the present application comprises the following steps:

[0018] (S1) impregnating a polyurethane foam in a phenolic resin solution, and then drying to obtain a polyurethane modified foam;

[0019] (S2) dissolving pitch in an organic solvent to form a pitch solution;

[0020] (S3) impregnating the polyurethane modified foam in the pitch solution, and then drying to obtain a pitch-loaded polyurethane modified foam;

[0021] (S4) oxidizing and curing the pitch-loaded polyurethane modified foam to obtain a composite foam;

[0022] (S5) carbonizing the composite foam to obtain the pitch-based foam carbon.

[0023] In some embodiments, in step (S1), the polyurethane foam is a cuboid with a pore size of 30-60 PPI, and the size is (1-10) x (1-4) x (1-4) cm 3 to serve as a foam carbon template, and the pore size is closely related to the subsequent pitch impregnation amount and the strength of the prepared foam carbon; the size is determined by the size of the subsequent carbonization equipment.

[0024] Further, the polyurethane foam can be washed with deionized water and anhydrous ethanol in sequence before use to remove impurities on the polyurethane foam.

[0025] In step (S1), the solvent of the phenolic resin solution is selected from at least one of ethanol, acetone, methanol, toluene, xylene, preferably ethanol.

[0026] Further, the content of the phenolic resin in the phenolic resin solution is 5-10 wt.%.

[0027] In step (S1), after impregnation, drying is performed to eliminate the influence of water on the phenolic resin solution. In some embodiments, the drying temperature is 100-120°C, and the drying time is 1-12 h.

[0028] The present application finds that, by using a phenolic resin solution, the adsorption amount of the template to the asphalt solution in step (S2) is increased by chemically modifying the polyurethane foam template.

[0029] In step (S2), the asphalt is dissolved in an organic solvent, and the raw material components are screened according to the principle of similarity compatibility, so that components with appropriate molecular weight and polarity size are dissolved in the organic solvent to form an asphalt solution, and solid-liquid separation is performed to remove components with large molecular weight and strong polarity; in some embodiments, in step (S2), the asphalt is selected from at least one of coal liquefaction asphalt, coal tar pitch, biomass pitch, or asphalt obtained by cracking of waste plastics.

[0030] The organic solvent is selected from at least one of toluene, cyclohexane, tetrahydrofuran, xylene, pyridine, or kerosene.

[0031] Further, the concentration of the asphalt solution in the asphalt solution affects the effect of asphalt impregnation. The weight ratio of the asphalt to the organic solvent is 1:(2-3), and they are fully stirred at ambient temperature, for example, for 1-24 h.

[0032] In step (S3), the polyurethane modified foam is impregnated in the asphalt solution. The specific operation is to extrude the polyurethane foam multiple times and use the resilience of the polyurethane foam to fully soak the asphalt solution, so that the polyurethane foam uniformly adheres to the asphalt solution inside and outside, and then dried to remove the toluene solution; in some embodiments, in step (S3), the drying temperature is ambient temperature (for example, 10-40°C), and the drying time is 24-72 h.

[0033] In step (S4), the obtained asphalt-loaded polyurethane-modified foam is subjected to an oxidative curing treatment, for example, placed in a tubular cracking furnace for oxidative curing treatment, so as to increase the intermolecular crosslinking of asphalt and form a more stable network structure, thereby improving the thermal stability and mechanical strength of the asphalt and reducing shrinkage and cracking in the subsequent carbonization process; in some embodiments, in step (S4), the oxidative curing conditions are as follows: the asphalt-loaded polyurethane-modified foam is heated from ambient temperature to 200-450℃ at a heating rate of 1-5℃·min -1 , and kept at this temperature for 0.5-2h, and finally cooled to ambient temperature.

[0034] In step (S5), the obtained composite foam after oxidative curing is subjected to a carbonization treatment, for example, placed in a tubular cracking furnace for carbonization treatment; in some embodiments, in step (S5), the carbonization treatment conditions are as follows: the composite foam is heated from ambient temperature to 650-1050℃ at a heating rate of 1-5℃·min -1 , and kept at this temperature for 0.5-2h, and finally cooled to ambient temperature.

[0035] The second aspect of the present application provides an asphalt-based foam carbon obtained by the above preparation method.

[0036] In some embodiments, the asphalt-based foam carbon has a pore size of 400-550μm, an open porosity of 97-98%, and a density of 0.03-0.05g / cm 3 , has a highly open pore structure, and has a compressive strength of 0.6-1.2MPa.

[0037] The present application will be described in detail below through specific examples. In the following examples and comparative examples:

[0038] The coal liquefaction asphalt is from Shenhua Coal-to-Oil Chemical Company;

[0039] The pore size and pore structure are measured by scanning electron microscopy (SEM); wherein the pore structure is a honeycomb-like structure, and the pore structure is determined to be highly open or uneven by observing and measuring the size of the channels in the field of view by SEM;

[0040] The open porosity is measured by density measurement method, for example, by measuring the mass of a specific volume of foam carbon in dry state and saturated liquid state to calculate;

[0041] The compressive strength is calculated by pressure testing of foam carbon with fixed volume and cross section.

[0042] Example 1 (A1)

[0043] (S1) impregnating the polyurethane foam washed with deionized water and anhydrous ethanol in an ethanol solution of phenolic resin, and then drying in a forced air drying oven to obtain a polyurethane modified foam; wherein,

[0044] the size of the polyurethane foam is 2x2x2 cm 3 , and the pore size is 50 PPI;

[0045] the content of phenolic resin in the ethanol solution of phenolic resin is 8 wt.%;

[0046] the drying temperature is 105°C, and the drying time is 2h.

[0047] (S2) slowly adding bitumen into an organic solvent, and mixing to form a bitumen solution; wherein,

[0048] the bitumen is coal liquefied bitumen, and the amount is 10g;

[0049] the organic solvent is toluene, and the amount is 30ml;

[0050] the mixing temperature is 25°C, and the mixing time is 2h.

[0051] (S3) impregnating the polyurethane modified foam of step (S1) in the bitumen solution of step (S2), and then drying to obtain a bitumen-loaded polyurethane modified foam; wherein,

[0052] the drying temperature is 25°C, and the drying time is 48h.

[0053] (S4) oxidatively curing the bitumen-loaded polyurethane modified foam of step (S3) in a tube furnace under an air atmosphere to obtain a composite foam; wherein,

[0054] the oxidative curing conditions include: heating to 300°C at 2°C / min, holding for 1h, and then cooling.

[0055] (S5) high-temperature carbonizing the composite foam of step (S4) in a tube furnace under a nitrogen atmosphere to obtain a bitumen-based foam carbon; wherein,

[0056] the high-temperature carbonization conditions include: heating to 800°C at 2°C / min, holding for 1h, and then cooling.

[0057] Example 2 (A2)

[0058] Reference Example 1 is followed, with the only difference being:

[0059] In step (S1),

[0060] the size of the polyurethane foam is 5x3x3 cm 3, the aperture is 60 PPI;

[0061] The content of phenolic resin in the ethanol solution of phenolic resin is 9 wt.%;

[0062] The drying temperature is 110℃, and the drying time is 6h.

[0063] In step (S2),

[0064] The content of asphalt is 15g;

[0065] The content of organic solvent is 40ml;

[0066] The mixing temperature is 25℃, and the mixing time is 12h.

[0067] In step (S3),

[0068] The drying temperature is 25℃, and the drying time is 24h.

[0069] In step (S4),

[0070] The oxidation curing conditions include: increasing the temperature to 400℃ at 3℃ / min, keeping for 1.5h and then cooling.

[0071] In step (S5),

[0072] The high-temperature carbonization conditions include: increasing the temperature to 900℃ at 3℃ / min, keeping for 1.5h and then cooling.

[0073] Example 3 (A3)

[0074] Refer to Example 1, the only difference is:

[0075] In step (S1),

[0076] The size of the polyurethane foam is 1x1x1cm 3 , the aperture is 45 PPI;

[0077] The content of phenolic resin in the ethanol solution of phenolic resin is 10 wt.%;

[0078] The drying temperature is 120℃, and the drying time is 12h.

[0079] In step (S2),

[0080] The amount of asphalt is 5g;

[0081] The amount of organic solvent is 10ml;

[0082] The mixing temperature is 25℃, and the mixing time is 24h.

[0083] In step (S3),

[0084] The temperature of drying is 25℃, and the time of drying is 72h.

[0085] In step (S4), the conditions of oxidative curing include: increasing temperature to 200℃ at 1℃ / min, keeping for 0.5h, and then cooling.

[0086] In step (S5), the conditions of high-temperature carbonization include: increasing temperature to 650℃ at 1℃ / min, keeping for 0.5h, and then cooling.

[0087] Example 4 (A4)

[0088] Refer to Example 1, the only difference is:

[0089] In step (S1),

[0090] The size of the polyurethane foam is 10x4x4cm 3 , and the pore size is 30PPI;

[0091] The content of phenolic resin in the ethanol solution of phenolic resin is 5wt.%;

[0092] The temperature of drying is 100℃, and the time of drying is 4h.

[0093] In step (S2),

[0094] The amount of asphalt is 20g;

[0095] The amount of organic solvent is 50ml;

[0096] The temperature of mixing is 25℃, and the time of mixing is 6h.

[0097] In step (S3),

[0098] The temperature of drying is 25℃, and the time of drying is 24h.

[0099] In step (S4), the conditions of oxidative curing include: increasing temperature to 450℃ at 4℃ / min, keeping for 2h, and then cooling.

[0100] In step (S5), the conditions of high-temperature carbonization include: increasing temperature to 1050℃ at 4℃ / min, keeping for 2h, and then cooling.

[0101] Example 5 (A5)

[0102] Refer to Example 1, the only difference is:

[0103] In step (S1),

[0104] The size of the polyurethane foam is 3x2x2cm 3 , and the pore size is 40 PPI;

[0105] The content of the phenolic resin in the ethanol solution of the phenolic resin is 6wt.%.

[0106] The drying temperature is 115℃, and the drying time is 8h.

[0107] In step (S2),

[0108] The amount of the asphalt is 12g;

[0109] The amount of the organic solvent is 30ml;

[0110] The mixing temperature is 25℃, and the mixing time is 18h.

[0111] In step (S3),

[0112] The drying temperature is 25℃, and the drying time is 36h.

[0113] In step (S4), the conditions of the oxidative curing include: increasing the temperature to 350℃ at a rate of 5℃ / min, keeping for 1h and then cooling. In step (S5), the conditions of the high-temperature carbonization include: increasing the temperature to 850℃ at a rate of 5℃ / min, keeping for 1h and then cooling.

[0114] Comparative Example 1 (D1)

[0115] Comparative Example 1 (D1) is prepared according to the method of Reference Example 1, with the only difference being that:

[0116] In step (S1), the polyurethane foam is directly dried after being cut and washed, without being subjected to the impregnation treatment. The asphalt-based foam carbon obtained in the above examples and comparative examples is characterized, and the results are shown in Table 1 below.

[0117] Table 1: Characterization of the asphalt-based foam carbon obtained in the examples and comparative examples

[0118]

[0119]

[0120] As can be seen from A1-A5 in Table 1, the asphalt-based foam carbon prepared in the present application has a pore size of 400-600μm, an open porosity of 97-98%, a density of 0.03-0.05g / cm 3 , a highly open air bubble structure, and a compressive strength of 0.6-1.2MPa, indicating that the asphalt is uniformly distributed in the foam carbon and the structure is stable.

[0121] As can be seen from the comparison of A1-A5 and D1 in Table 1, during the oxidative curing stage, the presence of phenolic resin in the impregnated phenolic resin-foamed carbon affects the open porosity. The foamed carbon prepared has higher mechanical strength, which can prevent the collapse of the pores and is conducive to the increase of the open porosity.

[0122] It is noted that the compressive strength of A4 is lower than that of D1, which can be because the polyurethane used as a template in A4 has a slightly smaller pore size, the phenolic resin concentration is low, and the content is low; in addition, the temperature of the subsequent oxidative curing and high-temperature carbonization is too high and the time is too long, which can also cause excessive volatilization of the light components in the pitch, resulting in shrinkage and cracking of the material, and thus the mechanical properties of the foamed carbon obtained by A4 are slightly lower than those of D1.

Claims

1. A method for preparing asphalt-based foamed carbon, characterized in that, Includes the following steps: (S1) Impregnate polyurethane foam with phenolic resin solution and then dry to obtain polyurethane modified foam; (S2) Dissolve asphalt in an organic solvent to form an asphalt solution; (S3) The polyurethane modified foam is impregnated in the asphalt solution and then dried to obtain asphalt-loaded polyurethane modified foam. (S4) The polyurethane modified foam loaded with asphalt is oxidized and cured to obtain composite foam; (S5) The composite foam is carbonized to obtain asphalt-based foam carbon. The polyurethane foam has a pore size of 30-60 PPI; The phenolic resin solution has a mass fraction of 5-10 wt.%. The weight ratio of asphalt to organic solvent in the asphalt solution is 1:(2-3); The oxidation curing conditions include: in an air atmosphere, the asphalt-loaded polyurethane modified foam is cured at 1-5 °C·min. -1 The heating rate is from ambient temperature to 200-450 ℃, held at that temperature for 0.5-2 h, and finally cooled to ambient temperature.

2. The preparation method according to claim 1, characterized in that, In step (S1), the solvent of the phenolic resin solution is selected from at least one of ethanol, acetone, methanol, toluene, and xylene.

3. The preparation method according to claim 2, characterized in that, The solvent for the phenolic resin solution is ethanol.

4. The preparation method according to claim 1, characterized in that, In step (S1), the size of the polyurethane foam is (1-10)×(1-4)×(1-4) cm. 3 .

5. The preparation method according to any one of claims 1 to 4, characterized in that, In step (S1), the polyurethane foam is thoroughly washed with deionized water and anhydrous ethanol and then impregnated in the phenolic resin solution; In step (S1), the drying temperature is 100-120 °C and the drying time is 1-12 h.

6. The preparation method according to any one of claims 1, 2, and 4, characterized in that, In step (S2), the asphalt is selected from at least one of coal liquefaction pitch, coal tar pitch, biomass pitch, or asphalt obtained from the pyrolysis of waste plastics; The organic solvent is selected from at least one of toluene, cyclohexane, tetrahydrofuran, xylene, pyridine, or kerosene.

7. The preparation method according to claim 6, characterized in that, In step (S2), the asphalt is coal liquefaction pitch and the organic solvent is toluene.

8. The preparation method according to any one of claims 1, 2, 4 and 7, characterized in that, In step (S3), the drying temperature is 10-40 °C and the drying time is 24-72 h.

9. The preparation method according to any one of claims 1, 2, 4 and 7, characterized in that, In step (S5), the high-temperature carbonization conditions include: in an inert gas atmosphere, the composite foam is heated at 1-5 °C·min. -1 The heating rate is from ambient temperature to 650-1050 ℃, held at that temperature for 0.5-2 h, and finally cooled to ambient temperature.

10. A pitch-based foamed carbon obtained by any one of claims 1 to 9.

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