Preparation method of carbon aerogel precursor with controllable particle size and morphology

Abstract

The invention discloses a preparation method of a carbon aerogel precursor with controllable particle size and morphology. The preparation method comprises the following steps: stirring and dissolving phenol, aldehyde and a catalyst to obtain a carbon aerogel precursor aqueous solution A; the preparation method comprises the following steps: refluxing a carbon aerogel precursor aqueous solution A to a critical state to be cured at a high temperature, quickly cooling in ice water, adding a polymerization inhibitor to stop a reaction process to obtain a carbon aerogel precursor aqueous solution B, extruding by an extruder, heating and curing in a curing agent solution, and cutting into granular phenolic resin particles, heating in a drying oven to increase the crosslinking degree to obtain a carbon aerogel precursor; the method provided by the invention has the advantages of concentrated product particle size, controllable morphology, no introduction of impurities, simple operation, high production efficiency, safety and environmental protection, the carbon aerogel precursor has a certain specific surface area after carbonization, the carbon aerogel precursor can be further activated to obtain the carbon aerogel with a higher specific surface area, and the method can be applied to carbon aerogel production.

Description

Technical Field

[0001] The invention belongs to the field of carbon aerogel material preparation, and in particular relates to a method for preparing a carbon aerogel precursor, which can be applied in the production of carbon aerogel. Background Art

[0002] Carbon aerogel has great application potential in national strategic emerging industries such as lithium battery silicon-carbon negative electrode, supercapacitors, and capacitor deionization. As a substitute for super activated carbon, it exhibits excellent properties of low resistivity, high specific capacitance, and strong cycle performance in supercapacitors; as a high-end resin-based porous carbon material, it has the characteristics of high specific surface area, good structural strength, and adjustable pore structure, which can provide effective support for the large-scale preparation of new silicon-carbon negative electrode materials. However, due to the high cost of raw materials, complex preparation process, long production cycle, and difficulty in industrial production, the industrialization of carbon aerogel products is difficult.

[0003] In recent years, the research on carbon aerogel production technology has increased in China, and mass production of hundreds of tons has been achieved. Among the more mature production processes, the following two methods are used to prepare carbon aerogel precursors:

[0004] The first is the reverse suspension polymerization method. In the reactor, phenolic aldehyde is adjusted into a solution in a certain proportion, then dispersed in the oil phase with a surfactant, and then polymerized at a certain temperature. The precursor particle size range produced by this method is wide, the fluctuation is large, and the production cycle is long, which is not conducive to the quality control of the production process; the prepared precursor oil needs to be washed with solvents, which increases the production cost; and the waste oil produced needs to be treated, which has a high environmental cost.

[0005] The second is the block crushing method. Phenolic formaldehyde is first prepared into block aerogel, and then mechanically crushed into powder. This method inevitably introduces impurities, which is very unfavorable for the application of carbon aerogel in the field of electrochemistry. The obtained powder particle size range is very wide, and there is a lot of dust, which is not conducive to the control of subsequent processes. In addition, the crushing process produces a lot of dust, which is harmful to the occupational health of operators.

[0006] Chinese patent application 201910020594.5 discloses a method for preparing carbon aerogel. The preparation method includes: dissolving a resorcinol compound, an aldehyde compound and a surfactant in a reaction solvent, so that the resorcinol compound and the aldehyde compound undergo a polymerization reaction to form a precursor solution containing a hydrogel. The resorcinol compound used in the preparation method is relatively expensive, which greatly increases the production cost of carbon aerogel. Chinese patent application 202111192453.5 discloses a method for preparing carbon aerogel, which uses an electrochemical method to electrolyze a raw material mixture including resorcinol and formaldehyde. Continuous power-on for a certain period of time can ensure that resorcinol and formaldehyde fully undergo a sol-gel reaction to obtain a carbon aerogel precursor, and the dried carbon dry gel is pyrolyzed to obtain the target carbon aerogel. This preparation method also uses expensive resorcinol, and a constant current of 50mA must be continuously passed through the electrolytic cell for 8 hours. The production cycle is long and the production cost is high, which is not conducive to large-scale production.

[0007] Therefore, as the demand for carbon aerogels increases, traditional preparation methods cannot meet the needs of large-scale production, which seriously restricts the mass production of carbon aerogels. Summary of the invention

[0008] The purpose of the present invention is to provide a method for preparing a carbon aerogel precursor with controlled particle size and morphology, which can achieve concentrated precursor particle size, controllable morphology, no introduction of impurities, simple operation, high production efficiency, safety and environmental protection, in order to address the technical difficulties existing in the existing carbon aerogel precursor preparation process, such as large fluctuations in precursor particle size range, difficult morphology control, high production cost, high environmental health risks, long production cycle, and unfavorable large-scale batch production.

[0009] In order to solve the above problems, the present invention provides a method for preparing a carbon aerogel precursor with controllable particle size and morphology, which is implemented by the following process:

[0010] (1) Preparation of carbon aerogel precursor aqueous solution: phenol, aldehyde and catalyst are added to water in a set ratio and stirred to dissolve to obtain carbon aerogel precursor aqueous solution A; the molar ratio of phenol to aldehyde is 1:(1.5-3), and the catalyst is an inorganic / organic acid or an inorganic / organic base; the stirring and dissolving is controlled in the range of 0-40° C.; the catalyst is added according to the activity of different phenol and aldehyde reactants, and the added catalyst accounts for 0-2.5% of the total mass of phenol, aldehyde and aqueous solution;

[0011] (2) High temperature reflux - ice water cooling: The carbon aerogel precursor aqueous solution A is refluxed at a high temperature of 45-95°C to a critical state of solidification, and then quickly cooled in ice water, and an inhibitor is added to terminate the reaction process to obtain a carbon aerogel precursor aqueous solution B with a certain molecular weight;

[0012] (3) Extrusion molding: extruding the carbon aerogel precursor aqueous solution B through a single-screw extruder / twin-screw extruder to obtain a strip of phenolic resin; controlling the size and morphology of the strip of phenolic resin by the model of the extrusion head of the single-screw extruder / twin-screw extruder;

[0013] (4) Curing: The extruded phenolic resin strips are placed in a curing agent solution for heating and curing, and then removed from the curing agent solution and drained;

[0014] (5) Cutting: Cutting the heat-cured strip-shaped phenolic resin into granular phenolic resin particles;

[0015] (6) Increasing the degree of crosslinking: The phenolic resin particles are heated in an oven to increase the degree of crosslinking to obtain a carbon aerogel precursor, and the heating temperature is controlled in the range of 60-120°C.

[0016] Preferably, in step (1), the catalyst is any one of hydrochloric acid, sulfuric acid, and acetic acid, or a mixed solvent of two or three thereof; the phenol used is one of resorcinol, phenol, phloroglucinol, and bisphenol A; and the aldehyde used is formaldehyde.

[0017] Preferably, in step (1), the catalyst may be any one of sodium hydroxide, potassium hydroxide, and triethylamine, or a mixed solvent of two or three thereof.

[0018] Preferably, in step (1), the stirring and dissolving is controlled in the range of 20 to 30°C.

[0019] Preferably, in step (1), the mass concentration of the formaldehyde aqueous solution used is 35-39%.

[0020] Preferably, in step (1), when the phenol used is resorcinol or phloroglucinol, no catalyst is required due to its high reaction activity; when a phenol with lower activity such as phenol or bisphenol A is used, a catalyst accounting for 0.1 to 2.2% of the total mass of the phenol, aldehyde and aqueous solution needs to be added.

[0021] Preferably, in step (6), the heating temperature is controlled in the range of 80-100°C.

[0022] Preferably, in step (2), the inhibitor is ethanol or methanol, and the amount added is 8-12% of the total mass of the carbon aerogel precursor aqueous solution A; and the curing agent used in step (4) is hexamethylenetetramine.

[0023] Furthermore, in step (6), the heating temperature in the oven is controlled within the range of 100-110° C.; and the curing agent solution used in step (4) is a 20% hexamethylenetetramine solution.

[0024] Compared with the prior art, the preparation method of the carbon aerogel precursor with controllable particle size and morphology of the present invention has the following beneficial effects:

[0025] (1) The method of the present invention uses extrusion molding to prepare carbon aerogel precursors. This method has better granulation characteristics than traditional reactors and can achieve precise control of morphology.

[0026] (2) The method of the present invention uses extrusion molding to prepare the carbon aerogel precursor. This method has better control over the powder particle size than the traditional block crushing method, does not generate dust, and is beneficial to improving product yield and reducing waste.

[0027] (3) The carbon aerogel precursor prepared by the method of the present invention does not require solvent washing, does not generate additional costs, and is beneficial to environmental protection.

[0028] (4) The method of the present invention only requires the preparation of a solution, does not require an oil phase, and does not require a surfactant, and is more environmentally friendly than traditional methods.

[0029] (5) Compared with the traditional carbon aerogel precursor production method, the production cost of the method of the present invention is reduced by more than 25%, the production cycle is shortened by more than 80%, and the economic effect is significant. DETAILED DESCRIPTION

[0030] To describe the present invention, a method for preparing a carbon aerogel precursor with controllable particle size and morphology is further described in detail below in conjunction with an embodiment. However, the present invention is not limited to the embodiment.

[0031] Embodiment 1:

[0032] (1) adding resorcinol and formaldehyde in a molar ratio of 1:1.5 into water and stirring and dissolving at 30° C. to obtain a carbon aerogel precursor aqueous solution A;

[0033] (2) reflux the carbon aerogel precursor aqueous solution A at 50° C. to a critical state of solidification, then quickly cool it in ice water, add ethanol accounting for 10% by weight of the carbon aerogel precursor aqueous solution A to terminate the reaction process, and obtain a carbon aerogel precursor aqueous solution B with a certain molecular weight;

[0034] (3) Extrusion molding: The carbon aerogel precursor aqueous solution B is extruded through a twin-screw extruder to obtain a strip of phenolic resin, and the size and morphology are controlled;

[0035] (4) Curing: The extruded phenolic resin strips are placed in a 20% urotropine solution and cured at 80° C., then removed from the urotropine solution and drained;

[0036] (5) Cutting: cutting the heat-cured strip phenolic resin into granular form;

[0037] (6) Increasing the degree of crosslinking: The phenolic resin particles are heated to 100° C. in an oven for 24 hours to increase the degree of crosslinking and obtain a carbon aerogel precursor.

[0038] Embodiment 2:

[0039] (1) adding phenol and formaldehyde in a molar ratio of 1:1.5 into water and stirring to dissolve at 60° C., then adding 0.1% of sodium hydroxide in an amount of the total mass of phenol, aldehyde and aqueous solution and stirring to dissolve, to obtain a carbon aerogel precursor aqueous solution A;

[0040] (2) reflux the carbon aerogel precursor aqueous solution A at 80° C. to a critical state of solidification, then quickly cool it in ice water, add methanol accounting for 10% of the total mass of the carbon aerogel precursor aqueous solution A to terminate the reaction process, and obtain a carbon aerogel precursor aqueous solution B with a certain molecular weight;

[0041] (3) Extrusion molding: The carbon aerogel precursor aqueous solution B is extruded through a twin-screw extruder to obtain a strip of phenolic resin, and the size and morphology are controlled;

[0042] (4) Curing: The extruded phenolic resin strips are placed in a 20% urotropine solution and cured at 80°C, then removed from the solution and drained;

[0043] (5) Cutting: cutting the heat-cured phenolic resin strip into granular form;

[0044] (6) Increasing the degree of crosslinking: The phenolic resin particles are heated to 100° C. in an oven for 24 hours to increase the degree of crosslinking and obtain a carbon aerogel precursor.

[0045] Embodiment 3:

[0046] (1) adding phloroglucinol and formaldehyde in a molar ratio of 1:3 into water and stirring and dissolving at 30° C. to obtain a carbon aerogel precursor aqueous solution A;

[0047] (2) reflux the carbon aerogel precursor aqueous solution A at 50° C. to a critical state of solidification, then quickly cool it in ice water, add ethanol accounting for 10% of the total mass of the carbon aerogel precursor aqueous solution A to terminate the reaction process, and obtain a carbon aerogel precursor aqueous solution B with a certain molecular weight;

[0048] (3) Extrusion molding: The carbon aerogel precursor aqueous solution B is extruded through a twin-screw extruder to obtain a strip of phenolic resin, and the size and morphology are controlled;

[0049] (4) Curing: The extruded phenolic resin strips are placed in a 20% urotropine solution and cured at 80°C, then removed from the solution and drained;

[0050] (5) Cutting: cutting the heat-cured strip phenolic resin into granular form;

[0051] (6) Increasing the degree of crosslinking: The phenolic resin particles were heated in an oven at 100°C for 24 hours to increase the degree of crosslinking and obtain a carbon aerogel precursor.

[0052] Embodiment 4:

[0053] (1) adding bisphenol A and formaldehyde in a molar ratio of 1:3 into water and stirring to dissolve at 60° C., then adding triethylamine in an amount of 0.5% by weight of the total weight of phenol, aldehyde and aqueous solution and stirring to dissolve to obtain a carbon aerogel precursor aqueous solution A;

[0054] (2) reflux the carbon aerogel precursor aqueous solution A at 90° C. to a critical state of solidification, then quickly cool it in ice water, add ethanol accounting for 10% of the total mass of the carbon aerogel precursor aqueous solution A to terminate the reaction process, and obtain a carbon aerogel precursor aqueous solution B with a certain molecular weight;

[0055] (3) Extrusion molding: The carbon aerogel precursor aqueous solution B is extruded through a twin-screw extruder to obtain a strip of phenolic resin, and the size and morphology are controlled;

[0056] (4) Curing: The extruded phenolic resin strips are placed in a 20% urotropine solution and cured at 80°C, then removed from the solution and drained;

[0057] (5) Cutting: cutting the heat-cured strip phenolic resin into granular form;

[0058] (6) Increasing the degree of crosslinking: The phenolic resin particles were heated in an oven at 110°C for 24 hours to increase the degree of crosslinking and obtain a carbon aerogel precursor.

[0059] Embodiment 5:

[0060] (1) adding phenol and formaldehyde in a molar ratio of 1:3 into water and stirring to dissolve at 60° C., then adding triethylamine accounting for 2% of the total mass of phenol, aldehyde and aqueous solution and stirring to dissolve to obtain a carbon aerogel precursor aqueous solution A;

[0061] (2) reflux the carbon aerogel precursor aqueous solution A at 90° C. to a critical state of solidification, then quickly cool it in ice water, add ethanol accounting for 10% of the total mass of the carbon aerogel precursor aqueous solution A to terminate the reaction process, and obtain a carbon aerogel precursor aqueous solution B with a certain molecular weight;

[0062] (3) Extrusion molding: The carbon aerogel precursor aqueous solution B is extruded through a twin-screw extruder to obtain a strip of phenolic resin, and the size and morphology are controlled;

[0063] (4) Curing: The extruded phenolic resin strips are placed in a 20% urotropine solution and cured at 95°C, then removed from the solution and drained;

[0064] (5) Cutting: cutting the heat-cured phenolic resin strip into granular form;

[0065] (6) Increasing cross-linking: The phenolic resin particles are heated in an oven at 100°C for 24 hours to increase the degree of cross-linking to obtain a carbon aerogel precursor.

[0066] Embodiment 6:

[0067] (1) adding phenol and formaldehyde in a molar ratio of 1:1.5 into water and stirring to dissolve at 60° C., then adding sodium hydroxide in an amount of 2% by weight of the total weight of phenol, aldehyde and aqueous solution and stirring to dissolve to obtain a carbon aerogel precursor aqueous solution A;

[0068] (2) reflux the carbon aerogel precursor aqueous solution A at 90° C. to a critical state of solidification, then quickly cool it in ice water, add ethanol accounting for 10% of the total mass of the carbon aerogel precursor aqueous solution A to terminate the reaction process, and obtain a carbon aerogel precursor aqueous solution B with a certain molecular weight;

[0069] (3) Extrusion molding: The carbon aerogel precursor aqueous solution B is extruded through a twin-screw extruder to obtain a strip of phenolic resin, and the size and morphology are controlled;

[0070] (4) Curing: The extruded phenolic resin strips are placed in a 20% urotropine solution and cured at 95°C, then removed from the solution and drained;

[0071] (5) Cutting: cutting the heat-cured phenolic resin strip into granular form;

[0072] (6) Increasing the degree of crosslinking: The phenolic resin particles are heated in an oven at 100°C for 24 hours to increase the degree of crosslinking and obtain a carbon aerogel precursor.

[0073] Comparative Example 1

[0074] (1) adding resorcinol and formaldehyde in a molar ratio of 1:1.5 into water and stirring and dissolving at 30° C. to obtain a carbon aerogel precursor aqueous solution A;

[0075] (2) adding surfactant Span 80 to 15# white oil, stirring evenly at 30° C. to prepare a white oil mixture, wherein Span 80 accounts for 10% of the volume of the white oil mixture;

[0076] (3) Continue stirring the white oil at a stirring speed of 1000 r / min, slowly pour in the carbon aerogel precursor aqueous solution A, and emulsify for 30 min to fully emulsify and mix the two into a suspension;

[0077] (4) heating the reactor to 80° C., reacting the suspension in the reactor for 12 hours, and obtaining a precursor white oil slurry;

[0078] (5) Finally, the precursor white oil slurry is filtered, washed with dichloromethane, and then filtered to obtain a porous carbon microsphere precursor.

[0079] After testing, the specific surface area of ​​the carbon aerogel precursors prepared in Examples 1-6 after carbonization is as follows:

[0080] Table 1 Carbonized tap density and specific surface area of ​​each example

[0081] Example 1 2 3 4 5 6 Comparative Example 1 <![CDATA[Specific surface area (m 2 / g)]]> 522 476 556 398 501 512 511

[0082] As can be seen from the above table, the carbon aerogel precursor prepared by the present invention has a certain specific surface area after drying and carbonization, which can achieve an effect close to that of the comparative example, and a carbon aerogel with a higher specific surface area can be obtained after further activation.

[0083] Calculation and experimental verification show that, compared with the currently commonly used comparative example 1, the method for preparing a carbon aerogel precursor with controllable particle size and morphology of the present invention reduces production costs by more than 25%, shortens production cycle by more than 80%, and achieves unexpected technical effects.

Claims

1. A method for preparing a carbon aerogel precursor with controllable particle size and morphology, characterized in that The following process is used: (1) Preparation of carbon aerogel precursor aqueous solution: phenol, aldehyde and catalyst are added to water in a set ratio and stirred to dissolve to obtain carbon aerogel precursor aqueous solution A; the molar ratio of phenol to aldehyde is 1:(1.5-3), and the catalyst is an inorganic / organic acid or an inorganic / organic base; the stirring and dissolving is controlled in the range of 0-40° C.; the catalyst is added according to the activity of different phenol and aldehyde reactants, and the added catalyst accounts for 0-2.5% of the total mass of phenol, aldehyde and aqueous solution; (2) High temperature reflux - ice water cooling: The carbon aerogel precursor aqueous solution A is refluxed at a high temperature of 45-95°C to a critical state of solidification, and then quickly cooled in ice water, and an inhibitor is added to terminate the reaction process to obtain a carbon aerogel precursor aqueous solution B with a certain molecular weight; (3) Extrusion molding: extruding the carbon aerogel precursor aqueous solution B through a single-screw extruder / twin-screw extruder to obtain a strip of phenolic resin; controlling the size and morphology of the strip of phenolic resin by the model of the extrusion head of the single-screw extruder / twin-screw extruder; (4) Curing: The extruded phenolic resin strips are placed in a curing agent solution for heating and curing, and then removed from the curing agent solution and drained; (5) Cutting: Cutting the heat-cured strip-shaped phenolic resin into granular phenolic resin particles; (6) Increasing the degree of crosslinking: The phenolic resin particles are heated in an oven to increase the degree of crosslinking to obtain a carbon aerogel precursor, and the heating temperature is controlled in the range of 60-120°C.

2. The method for preparing a carbon aerogel precursor with controllable particle size and morphology as claimed in claim 1, characterized in that: In step (1), the catalyst is any one of hydrochloric acid, sulfuric acid, and acetic acid, or a mixed solvent of two or three thereof; the phenol used is one of resorcinol, phenol, phloroglucinol, and bisphenol A; and the aldehyde used is formaldehyde.

3. The method for preparing a carbon aerogel precursor with controllable particle size and morphology as claimed in claim 1, characterized in that: In step (1), the catalyst is any one of sodium hydroxide, potassium hydroxide, and triethylamine, or a mixed solvent of two or three thereof; the phenol used is one of resorcinol, phenol, phloroglucinol, and bisphenol A; and the aldehyde used is formaldehyde.

4. The method for preparing a carbon aerogel precursor with controllable particle size and morphology as claimed in claim 1, 2 or 3, characterized in that: In step (1), the stirring and dissolving temperature is controlled in the range of 20 to 30°C.

5. The method for preparing a carbon aerogel precursor with controllable particle size and morphology as claimed in claim 1, 2 or 3, characterized in that: In step (1), the mass concentration of the formaldehyde aqueous solution used is 35-39%.

6. The method for preparing a carbon aerogel precursor with controllable particle size and morphology as claimed in claim 1, 2 or 3, characterized in that: In step (1), the added catalyst accounts for 0.1-2.2% of the total mass of phenol, aldehyde and aqueous solution.

7. The method for preparing a carbon aerogel precursor with controllable particle size and morphology as claimed in claim 1, 2 or 3, characterized in that: In step (6), the heating temperature is controlled in the range of 80-100°C.

8. The method for preparing a carbon aerogel precursor with controllable particle size and morphology as claimed in claim 1, 2 or 3, characterized in that: In step (2), the inhibitor is ethanol or methanol, and the added amount is 8-12% of the total mass of the carbon aerogel precursor aqueous solution A; and the curing agent used in step (4) is hexamethylenetetramine.

9. The method for preparing a carbon aerogel precursor with controllable particle size and morphology as claimed in claim 2 or 3, characterized in that: In step (1), the stirring and dissolving is controlled in the range of 20 to 30° C.; the mass concentration of the formaldehyde aqueous solution used is 35 to 39%; the added catalyst accounts for 0.1 to 2.2% of the total mass of phenol, aldehyde and aqueous solution; in step (2), the inhibitor is ethanol or methanol, and the added amount is 8 to 12% of the total mass of the carbon aerogel precursor aqueous solution A; the curing agent in step (4) is urotropine; in step (6), the heating temperature is controlled in the range of 80 to 100° C.

10. The method for preparing a carbon aerogel precursor with controllable particle size and morphology as claimed in claim 9, characterized in that: In step (6), the heating temperature in the oven is controlled within the range of 100-110° C.; the curing agent solution used in step (4) is a 20% hexamethylenetetramine solution.