High-thermal-conductivity natural gas adsorbent and preparation method thereof

Abstract

The invention provides a high thermal conductivity natural gas adsorbent and a preparation method thereof, and the preparation method comprises the following steps: uniformly mixing a phenolic compound, an aldehyde solution, sodium carbonate and water to obtain a precursor solution; sequentially adding biomass fibers and a heat-conducting filler into the precursor solution, and uniformly mixing to obtain a mixed solution; carrying out crosslinking on the mixed solution by adopting an infrared-assisted crosslinking method, and then forming gel by adopting a gradient heating method; carrying out solvent replacement on the gel, and carrying out segmented drying on the organic gel by adopting infrared radiation; performing carbonization to obtain composite carbon aerogel; and performing hot pressing on the composite carbon aerogel in a mold, and carbonizing again to obtain the composite carbon aerogel. The biomass fibers and the heat-conducting filler are directly added into the precursor solution, and the precursor solution is subjected to a cross-linking reaction to obtain gel, so that the biomass fibers and the heat-conducting filler are uniformly dispersed in the carbon aerogel, the influence of the heat effect is further reduced, the reserve volume of natural gas with unit density is increased, and the performance of the adsorbent is further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of natural gas adsorption storage, and relates to a high thermal conductivity natural gas adsorbent and a preparation method thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] Adsorption storage of natural gas (ANG) is a technology that uses high-surface-area, microporous adsorbents to absorb and store natural gas at low and medium pressures. Compared to compressed natural gas (CNG) technology, ANG offers significant advantages in terms of bulk density, type, and system cost of gas storage equipment. Therefore, ANG technology has the potential to replace CNG technology, or at least be developed as an advanced gas storage technology. Carbon aerogel, as a new lightweight, nanoporous, amorphous adsorption material, possesses properties such as high surface area, low mass density, and nanoscale continuous pores. Compared to traditional ANG adsorption materials (such as activated carbon, MCM-41, fullerenes, metal-organic framework materials, and carbon nanotubes), carbon aerogel, with its large surface area and rich micro-nanoporous structure, exhibits excellent performance in the adsorption and storage of natural gas at room temperature and low pressure.

[0004] Since the implementation of ANG technology involves the adsorption and desorption of natural gas by the adsorbent, the adsorption process releases heat, causing the adsorption bed temperature to rise and resulting in a decrease in adsorption capacity. Conversely, the desorption process absorbs heat, causing the adsorption bed temperature to drop and the desorption capacity to decrease, ultimately significantly reducing the system's gas storage capacity. Therefore, effective measures must be taken to mitigate the impact of thermal effects. Furthermore, adsorbent parameters such as pore size and pore distribution directly affect its adsorption capacity for natural gas molecules. Generally speaking, adsorbents with moderately sized and uniformly distributed pores are more effective in adsorbing natural gas molecules, thereby improving the volumetric adsorption ratio. However, there is a certain trade-off between adsorbent density and pore structure: as the porosity of the adsorbent increases, its density generally decreases. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a natural gas adsorbent with high thermal conductivity and high density and a preparation method thereof.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: The first aspect of the present invention provides a method for preparing a natural gas adsorbent with high thermal conductivity and high density, comprising: The phenolic compound, the aldehyde solution, sodium carbonate and water are mixed uniformly to obtain a precursor solution; adding biomass fiber and thermal conductive filler to the precursor solution in sequence, mixing them evenly to obtain a mixed solution; The mixed solution is first cross-linked by infrared assisted cross-linking method, and then formed into a gel by gradient heating method; The gel is subjected to solvent replacement, and then the organic gel is dried in sections using infrared radiation; and carbonized to obtain a composite carbon aerogel; The composite carbon aerogel is hot-pressed in a mold and carbonized again to obtain the aerogel.

[0007] The second aspect of the present invention provides a natural gas adsorbent with high thermal conductivity and high density prepared by the above method.

[0008] The third aspect of the present invention provides the use of the above-mentioned high thermal conductivity, high density natural gas adsorbent in the field of natural gas adsorption storage.

[0009] Beneficial effects of the present invention 1. The present invention incorporates a thermally conductive filler into the adsorbent. This filler has a high thermal conductivity and can rapidly exchange heat with the environment outside the adsorbent particles, reducing thermal effects during natural gas adsorption and desorption, and increasing the natural gas storage capacity of the composite adsorbent. The addition of biomass fiber also enhances the mechanical properties of the composite adsorbent. The biomass fiber and thermally conductive filler are directly added to a precursor solution, which undergoes a crosslinking reaction to form a gel. This uniform dispersion of the biomass fiber and thermally conductive filler within the carbon aerogel further reduces the impact of thermal effects, increases natural gas reserves per unit density, and further improves the adsorbent's performance.

[0010] 2. During the sol-gel stage, the present invention utilizes infrared radiation-assisted cross-linking and gradient aging processes to enhance the skeleton strength. Infrared radiation can be selectively absorbed by polar groups in the sol, directly exciting molecular vibrations and reducing the activation energy of the polycondensation reaction, thereby accelerating the formation of the three-dimensional gel network. Furthermore, the thermally conductive filler also generates localized high temperatures due to its high infrared absorptivity, promoting chemical bonding with the three-dimensional gel network, and the gel polycondenses in situ on the filler surface. As a result, the number of cross-linking points within the final material increases, and the skeleton rigidity is enhanced.

[0011] 3. The present invention uses a multi-stage pressure-temperature synergistic control combination combined with an activation process to improve the packing density of the adsorbent material. Pre-pressing at room temperature can initially increase the bulk density of the carbon aerogel powder through physical compression, reducing internal voids. Subsequently, higher pressure is applied during the heating process to promote the formation of dense bonds at the particle interface and retain the pore structure, ultimately achieving an increase in the packing density of the adsorbent material. A mild physical activation step is combined to selectively etch the carbon aerogel's skeleton structure. While retaining the original pore structure, micro / mesopores are directionally generated, maximizing the porosity and specific surface area of the adsorbent material. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their description are used to explain the present invention and do not constitute improper limitations on the present invention.

[0013] Figure 1 SEM images of carbon aerogels at different scales in Example 1; Figure 2 Comparison of thermal conductivity of carbon aerogel before and after addition of thermal conductive filler in Example 1; Figure 3 CH4 adsorption isotherms of carbon aerogel before and after addition of thermal conductive filler in Example 1; Figure 4 Stress-strain curve of the composite carbon aerogel (with kapok fiber added) in Example 1; Figure 5 Stress-strain curve of the composite carbon aerogel (without kapok fiber) in Example 1. DETAILED DESCRIPTION

[0014] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0015] Unless otherwise defined, all professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. The reagents or raw materials used in the present invention can be purchased through conventional channels. Unless otherwise specified, the reagents or raw materials used in the present invention are used in accordance with conventional methods in the art or according to product specifications. Similarly, unless otherwise specified, the test methods of the present invention are also tested in accordance with conventional methods in the art or the common methods or standards in the industry. In addition, any methods and materials similar to or equivalent to the described contents can be applied to the inventive method. The preferred embodiments and materials described herein are for demonstration purposes only.

[0016] The present invention provides a method for preparing a natural gas adsorbent with high thermal conductivity and high density, comprising: The phenolic compound, the aldehyde solution, sodium carbonate and water are mixed uniformly to obtain a precursor solution; adding biomass fiber and thermal conductive filler to the precursor solution in sequence, mixing them evenly to obtain a mixed solution; The mixed solution is first cross-linked by infrared assisted cross-linking method, and then formed into a gel by gradient heating method; The gel is subjected to solvent replacement, and then the organic gel is dried in sections using infrared radiation; and carbonized to obtain a composite carbon aerogel; The composite carbon aerogel is hot-pressed in a mold and carbonized again to obtain the aerogel.

[0017] In some embodiments, the mass ratio of the phenolic compound, aldehyde solution, sodium carbonate and water is 1:(1.5-2.5):(0.003-0.04):(1.6-1.8); In some embodiments, the phenols are selected from one or more of phenol, m-cresol, resorcinol, phloroglucinol, o-cresol, o-chlorophenol, and cardanol; In some embodiments, the aldehyde is selected from one of formaldehyde, acetaldehyde, furfural, vanillin, benzaldehyde, and glutaraldehyde.

[0018] In some embodiments, the mass ratio of the biomass fiber, the thermally conductive filler, and the phenolic compound is (0.2-0.6):1:(0.05-0.2); the in-situ addition of the biomass fiber and the thermally conductive filler can produce a synergistic effect, thereby maximizing the thermal conductivity and mechanical properties of the composite system.

[0019] In some embodiments, the biomass fiber is selected from one or more of kapok fiber, pineapple fiber, banana leaf fiber, oil palm fiber, cotton fiber, flax fiber, bamboo pulp fiber, sisal fiber, corn fiber, wheat straw fiber, coconut fiber, and dracaena fiber; In some embodiments, the thermally conductive filler is selected from one or more of graphene, carbon fiber, expanded graphite, boron nitride, silicon nitride, aluminum oxide, and copper powder.

[0020] To enhance the sol-gel skeleton strength, the present invention has studied crosslinking methods. In some embodiments, the specific conditions of the infrared-assisted crosslinking method are as follows: an infrared lamp with a wavelength of 2.5 to 5 μm, a power of 50 to 300 W, a distance of 10 to 30 cm between the infrared source and the liquid surface, a temperature of 50 to 60°C, and an exposure time of 20 to 50 minutes. This further enhances the sol-gel skeleton strength.

[0021] To promote gel aging, the present invention investigates a temperature ramp. In some embodiments, the specific conditions for the gradient temperature ramp are first maintaining the temperature at 60-62°C for 10-14 hours, then maintaining the temperature at 65-68°C for 10-14 hours, and finally maintaining the temperature at 70-72°C for 12-20 hours. This gradient temperature ramp assists gel aging and gradually strengthens the gel's network structure.

[0022] In some embodiments, the specific steps of the solvent replacement are: first replacing the solvent with ethanol, and then replacing the solvent with acetone; To improve drying efficiency, the present invention has studied drying methods. In some embodiments, the specific steps of the staged drying are as follows: the infrared lamp has a wavelength range of 2-10 μm and a power of 100-380 W; the first stage is a drying temperature of 40-80°C for an exposure time of 10-60 minutes; the second stage is a drying temperature of 80-150°C, maintained at a constant temperature, with short-term radiation for 5-15 minutes. Compared to traditional supercritical drying, infrared drying time is shortened by over 50%.

[0023] In order to improve the porosity and specific surface area of the composite carbon aerogel, the present invention studies the carbonization conditions. In some embodiments, the carbonization conditions are: in an inert atmosphere, keeping the temperature at 350-400 ° C for 60-80 min, then raising the temperature to 800-1200 ° C and keeping the temperature for 3-6 h to better improve the porosity and specific surface area of the composite carbon aerogel.

[0024] In order to improve the packing density of the adsorbent material, the present invention studies the conditions of hot pressing. In some embodiments, the hot pressing conditions are: pre-pressing at a pressure of 5 to 10 MPa for 5 to 10 minutes; then heating to 120 to 140°C, applying a pressure of 10 to 30 MPa, and maintaining the temperature and pressure for 60 to 90 minutes; so as to better improve the packing density of the adsorbent material.

[0025] In order to further improve the porosity and specific surface area of the adsorbent material, the present application studies the conditions for re-carbonization. In some embodiments, the re-carbonization conditions are as follows: in an inert atmosphere, keep the temperature at 350~400°C for 60~80 min, then raise the temperature to 800~1200°C, and introduce water vapor or carbon dioxide at 170~190 mL / min and keep the temperature constant for 60~120 min, so as to further improve the porosity and specific surface area of the adsorbent material and optimize the adsorption performance, and finally obtain a composite carbon aerogel material with high thermal conductivity and high density.

[0026] More specifically, they include: S1. A phenolic compound, an aldehyde solution, sodium carbonate, and water are mixed in a mass ratio of 1:(1.5-2.5):(0.003-0.04):(1.6-1.8) to obtain a precursor solution.

[0027] S2. A certain mass of biomass fiber is added to the precursor solution and stirred at 400-600 rpm / min for 3-7 hours to fully mix to obtain a mixed solution A. A thermally conductive filler is then added to the mixed solution and stirred at 600-800 rpm / min for 4-6 hours to obtain a mixed solution B. The mass ratio of the biomass fiber, thermally conductive filler, and phenolic compound is (0.2-0.6):1:(0.05-0.2).

[0028] S3. Pour mixed solution B into a circular mold and place it on an infrared heating plate. Infrared-assisted crosslinking is used to enhance the sol-gel backbone strength. The infrared lamp wavelength is set between 2.5 and 5 μm to match the molecular vibrational energy levels, and the power is set between 50 and 300 W to accelerate the formation of covalent bonds between molecular chains. The distance between the infrared source and the liquid surface is 10 to 30 cm to ensure uniform energy distribution. The temperature is controlled between 50 and 60°C, and the exposure time is 20 to 50 minutes to promote the polycondensation reaction without causing violent volatilization. A gradient temperature ramp is then used to assist gel aging: maintaining the temperature at 60°C for 10 to 14 hours (to promote further condensation of unreacted groups and increase local crosslinking density), 65°C for 10 to 14 hours (to enhance the mobility of molecular chains and initiate the formation of pore structures), and finally at 70°C for 12 to 20 hours (to strengthen the rigidity of the gel backbone and regulate the mesopore-macropore distribution), gradually strengthening the gel network structure.

[0029] S4. Replace the obtained gel with a volatile organic solvent. First, replace it with ethanol for 2 days, once in the morning and once in the evening, with an interval of 12 hours; then replace the solvent with acetone for 3 days, once in the morning and once in the evening, with an interval of 12 hours; and obtain an organic gel.

[0030] S5. The organogel is then dried in stages using infrared radiation. The infrared lamp wavelength is set between 2 and 10 μm, and the power is set between 100 and 380 W. The first stage involves drying at a temperature between 40 and 80°C, increasing linearly at 10°C / min for 10 to 60 minutes to remove most of the solvent. The second stage involves drying at a constant temperature between 80 and 150°C, with short bursts of radiation for 5 to 15 minutes to completely remove any residual solvent, resulting in a dry composite aerogel. Compared to traditional supercritical drying, infrared drying reduces drying time by over 50%.

[0031] S6. The obtained composite aerogel is placed in a tubular furnace for carbonization. The temperature is raised to 350-400 °C at a rate of 5-7 °C / min in an inert atmosphere of nitrogen and kept at this temperature for 60-80 min. The temperature is then raised to 800-1200 °C at a rate of 5-7 °C / min and kept at the set temperature for 3-6 h. The carbonized composite aerogel is then naturally cooled to room temperature to obtain the composite carbon aerogel.

[0032] S7. A custom mold (1 cm × 1 cm × 3 cm) was used. A release agent was applied to the inner wall. The carbonized aerogel powder was filled into the mold. A pre-pressing pressure of 5–10 MPa was applied at room temperature for 5–10 minutes. The temperature was then raised to 120–140°C at a rate of 5–10°C / min, and a pressure of 10–30 MPa was applied. This pressure was maintained for 60–90 minutes. The mold was then slowly cooled to room temperature and demolded to obtain the final carbon aerogel material, thereby increasing the packing density of the adsorbent material.

[0033] S8. Place the pressed carbon aerogel back into the tubular furnace, first heat it to 350-400 °C at a rate of 5-7 °C / min in a nitrogen atmosphere and keep it constant at that temperature for 60-80 min, then heat it to 800-1200 °C at a rate of 5-7 °C / min in a nitrogen atmosphere, introduce water vapor or carbon dioxide at a rate of 170-190 mL / min and keep it constant at that temperature for 60-120 min, further improve the porosity and specific surface area of the adsorbent material, optimize the adsorption performance, and finally obtain a composite carbon aerogel material with high thermal conductivity and high density.

[0034] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are intended to explain the present invention rather than to limit it.

[0035] Thermal conductivity testing: Thermal conductivity was measured using a thermal conductivity tester (TPS 2500 S). Using the transient plane heat source method, a block module was selected for testing the thermal conductivity of the composite material. Probe model 5465 was used. Heating power and test time were adjusted based on the overall temperature rise, characteristic time, and average deviation after the test. Sample dimensions were 1 cm × 1 cm × 1 cm. Three tests were performed, with 15-minute intervals between each test. The thermal conductivity results were averaged.

[0036] CH4 Adsorption Isotherms: CH4 adsorption was performed in an automated high-pressure gas adsorption instrument (BSD-PH) using a static volumetric measurement technique with high-purity CH4 (99.999%) as the adsorbent. Prior to testing, all samples were degassed under vacuum at 423 K for 12 hours to remove adsorbed moisture and unwanted gases. Adsorption isotherms were measured at 298 K from 0 to 100 bar.

[0037] Stress-strain curves: Compression tests were performed on a tensile compressor (AI-7000S MTS system) at a speed of 1 mm / min until the sample was broken (sample size was 1 cm × 1 cm × 1 cm).

[0038] Example 1 The method for preparing the high thermal conductivity and high density natural gas adsorbent of this embodiment includes the following steps: S1. Phenol, formaldehyde, sodium carbonate, and water are mixed in a mass ratio of 1:1.5:0.003:1 to obtain a precursor solution.

[0039] S2. Add biomass fiber (kapok fiber) to the precursor solution and stir at 400 rpm / min for 7 hours to fully mix, thereby obtaining mixed solution A. Then, add a thermally conductive filler (boron nitride) to the mixed solution, followed by stirring at 600 rpm / min for 4 hours to obtain mixed solution B. The mass ratio of the biomass fiber, thermally conductive filler, and phenolic compound is (0.2):1:(0.05).

[0040] S3. Pour mixed solution B into a circular mold and place it on an infrared heating plate. Infrared-assisted crosslinking is used to strengthen the sol-gel skeleton. The infrared lamp wavelength is set to 2.5 μm, the power is set to 50 W, the distance between the infrared source and the liquid surface is 10 cm, the temperature is controlled at 50°C, and the exposure time is 50 minutes. A gradient temperature ramp is then used to assist in gel aging: maintain the temperature at 60°C for 10 hours, 65°C for 10 hours, and finally at 70°C for 12 hours.

[0041] S4. Solvent replacement is performed on the gel obtained in S3. First, the gel is replaced with anhydrous ethanol for 2 days, once in the morning and evening, with an interval of 12 hours; then the gel is replaced with acetone for 3 days, once in the morning and evening, with an interval of 12 hours; and an organogel is obtained.

[0042] S5. The organogel was then dried in stages using infrared radiation. The infrared lamp wavelength was set to 2 μm and the power was set to 100 W. The first stage was controlled at 40°C with a linear increase of 10°C / min for 60 minutes to remove most of the solvent. The second stage was controlled at 80°C with a constant temperature and short-term radiation for 15 minutes to completely remove the residual solvent and obtain a dry composite aerogel.

[0043] S6. The obtained composite aerogel was placed in a tubular furnace for carbonization. The temperature was raised to 350 °C at a rate of 5 °C / min in an inert atmosphere of nitrogen and kept at that temperature for 80 min. The temperature was then raised to 800 °C at a rate of 5 °C / min and kept at the set temperature for 6 h. The carbonized composite aerogel was then naturally cooled to room temperature to obtain the composite carbon aerogel.

[0044] S7. A custom mold (1 cm × 1 cm × 3 cm) was used. A release agent was applied to the inner wall. The carbonized aerogel powder was filled into the mold. A pre-pressing pressure of 5 MPa was applied at room temperature for 10 minutes. The temperature was then raised to 120°C at a rate of 5°C / min, and a pressure of 10 MPa was applied. This pressure was maintained at this temperature for 90 minutes. The mold was then slowly cooled to room temperature and demolded to obtain the final carbon aerogel material.

[0045] S8. Place the pressed carbon aerogel back into the tubular furnace, first heat it to 350 °C at a rate of 5 °C / min in a nitrogen atmosphere and keep it constant at that temperature for 80 min, then heat it to 800 °C at a rate of 5 °C / min in a nitrogen atmosphere, introduce water vapor at a rate of 170 mL / min and keep it constant at that temperature for 120 min, and obtain a composite carbon aerogel material with high thermal conductivity and high density.

[0046] Figure 1 is the SEM image of the carbon aerogel at different scales in Example 1, Figure 2 This is a comparison of the thermal conductivity of the carbon aerogel before and after the addition of the thermal conductive filler in Example 1; Figure 3 The CH4 adsorption isotherms of carbon aerogel before and after the addition of thermal conductive filler in Example 1 are shown. The adsorption amount is 231 cm 3 / g; Figure 4 、 Figure 5 The two stress-strain curves are obtained by testing different samples before and after adding biomass fiber in Example 1. One is the stress-strain curve obtained by adding kapok fiber ( Figure 4 ), the strain exceeded 60% without failure, and the maximum stress reached 9.3 MPa. Another one without adding kapok fiber ( Figure 5 ), during the initial strain increase, the region was slightly damaged, but the strain could reach over 80% without failure, and the maximum stress reached 6.93 MPa, which shows that the addition of biomass fibers is beneficial to the improvement of the mechanical properties of composite carbon aerogels.

[0047] Example 2 The method for preparing the high thermal conductivity and high density natural gas adsorbent of this embodiment includes the following steps: S1. A phenolic compound (m-cresol), an aldehyde solution (formaldehyde), sodium carbonate, and water are mixed in a mass ratio of 1:2:0.02:1.65 to obtain a precursor solution.

[0048] S2. Add biomass fiber (flax fiber) to the precursor solution and stir at 500 rpm / min for 5 hours to fully mix, thereby obtaining a mixed solution A. Then, add a thermally conductive filler (carbon fiber) to the mixed solution, followed by stirring at 700 rpm / min for 5 hours to obtain a mixed solution B. The mass ratio of the biomass fiber, thermally conductive filler, and phenolic compound is (0.4):1:(0.125).

[0049] S3. Pour mixed solution B into a circular mold and place it on an infrared heating plate. Infrared-assisted crosslinking is used to enhance the sol-gel skeleton strength. The infrared lamp wavelength is set to 3.75 μm, the power is set to 175 W, the distance between the infrared source and the liquid surface is 20 cm, the temperature is controlled at 55°C, and the exposure time is 35 minutes. A gradient temperature ramp is then used to assist in gel aging: maintain the temperature at 60°C for 12 hours, 65°C for 12 hours, and finally at 70°C for 16 hours.

[0050] S4. Solvent replacement is performed on the gel obtained in S3. First, the gel is replaced with anhydrous ethanol for 2 days, once in the morning and evening, with an interval of 12 hours; then the gel is replaced with acetone for 3 days, once in the morning and evening, with an interval of 12 hours; and an organogel is obtained.

[0051] S5. The organogel was then dried in stages using infrared radiation. The infrared lamp wavelength was set to 6 μm and the power was set to 240 W. The first stage was performed at a temperature of 60°C, increasing linearly at 10°C / min for 35 minutes to remove most of the solvent. The second stage was performed at a constant temperature of 115°C with a short-term irradiation for 10 minutes to completely remove any residual solvent, resulting in a dry composite aerogel.

[0052] S6. The obtained composite aerogel was placed in a tubular furnace for carbonization. The temperature was raised to 375 °C at a rate of 6 °C / min in an inert atmosphere of nitrogen and kept at this temperature for 70 min. The temperature was then raised to 1000 °C at a rate of 6 °C / min and kept at the set temperature for 4.5 h. The carbonized composite aerogel was then naturally cooled to room temperature to obtain the composite carbon aerogel.

[0053] S7. A custom mold (1 cm × 1 cm × 3 cm) was used. A release agent was applied to the inner wall. The carbonized aerogel powder was filled into the mold. A pre-pressing pressure of 7.5 MPa was applied at room temperature for 7.5 minutes. The temperature was then raised to 130°C at a rate of 7.5°C / min, and a pressure of 20 MPa was applied. This pressure was maintained at this temperature for 75 minutes. The mold was then slowly cooled to room temperature and demolded to obtain the final carbon aerogel material.

[0054] S8. The pressed carbon aerogel was placed in a tubular furnace again. The temperature was first raised to 375 °C at a rate of 6 °C / min in a nitrogen atmosphere and kept constant at this temperature for 70 min. The temperature was then raised to 1000 °C at a rate of 6 °C / min in a nitrogen atmosphere. Carbon dioxide was introduced at a rate of 180 mL / min and kept constant at this temperature for 90 min. A composite carbon aerogel material with high thermal conductivity and high density was obtained. The adsorption capacity was 212 cm 3 / g.

[0055] Example 3 The method for preparing the high thermal conductivity and high density natural gas adsorbent of this embodiment includes the following steps: S1. A phenolic compound (cardanol), an aldehyde solution (furfural), sodium carbonate, and water are mixed in a mass ratio of 1:2.5:0.04:1.8 to obtain a precursor solution.

[0056] S2. Biomass fiber (bamboo pulp fiber) was added to the precursor solution and stirred at 600 rpm / min for 3 h to obtain a mixed solution A. A thermally conductive filler (expanded graphite) was then added to the mixed solution and stirred at 800 rpm / min for 4 h to obtain a mixed solution B. The mass ratio of the biomass fiber, thermally conductive filler, and phenolic compound was (0.6):1:(0.2).

[0057] S3. Pour mixed solution B into a circular mold and place it on an infrared heating plate. Infrared-assisted crosslinking is used to strengthen the sol-gel skeleton. The infrared lamp wavelength is set to 5 μm, the power is set to 300 W, the distance between the infrared source and the liquid surface is 30 cm, the temperature is controlled at 60°C, and the exposure time is 20 minutes. A gradient temperature ramp is then used to assist in gel aging: maintain the temperature at 60°C for 14 hours, 65°C for 14 hours, and finally at 70°C for 20 hours.

[0058] S4. Solvent replacement is performed on the gel obtained in S3. First, the gel is replaced with anhydrous ethanol for 2 days, once in the morning and evening, with an interval of 12 hours; then the gel is replaced with acetone for 3 days, once in the morning and evening, with an interval of 12 hours; and an organogel is obtained.

[0059] S5. The organogel was then dried in stages using infrared radiation. The infrared lamp wavelength was set to 10 μm and the power was set to 380 W. The first stage was performed at a temperature of 80°C, increasing linearly at 10°C / min for 60 minutes to remove most of the solvent. The second stage was performed at a constant temperature of 150°C with short-term radiation for 15 minutes to completely remove any residual solvent, resulting in a dry composite aerogel.

[0060] S6. The obtained composite aerogel was placed in a tubular furnace for carbonization. The temperature was raised to 400 °C at a rate of 7 °C / min in an inert atmosphere of nitrogen and kept at that temperature for 80 min. The temperature was then raised to 1200 °C at a rate of 7 °C / min and kept at the set temperature for 6 h. The carbonized composite aerogel was then naturally cooled to room temperature to obtain the composite carbon aerogel.

[0061] S7. A custom mold (1 cm × 1 cm × 3 cm) was used. A release agent was applied to the inner wall. The carbonized aerogel powder was filled into the mold. A pre-pressing pressure of 10 MPa was applied at room temperature for 10 minutes. The temperature was then raised to 140°C at a rate of 10°C / min, and a pressure of 30 MPa was applied. This pressure was maintained at this temperature for 90 minutes. The mold was then slowly cooled to room temperature and demolded to obtain the final carbon aerogel material.

[0062] S8. The pressed carbon aerogel was placed in a tubular furnace again. The temperature was first raised to 400 °C at a rate of 7 °C / min in a nitrogen atmosphere and kept constant at that temperature for 80 min. The temperature was then raised to 1200 °C at a rate of 7 °C / min in a nitrogen atmosphere. Water vapor was introduced at a rate of 190 mL / min and kept constant at that temperature for 120 min. A composite carbon aerogel material with high thermal conductivity and high density was obtained. The adsorption capacity was 206 cm 3 / g.

[0063] Comparative Example 1 The difference from Example 2 is that no biomass fiber is added, the total amount remains unchanged, and the mass ratio of the thermal conductive filler to the phenolic compound is 1.4:0.125.

[0064] The test results show that the stress increase rate of the composite carbon aerogel without biomass fiber is greater than that of the composite carbon aerogel with biomass fiber in the low strain range (0~20%), and the maximum stress of the carbon aerogel without biomass fiber reaches 2 MPa. At 100 bar, the CH4 gas adsorption capacity is 172 cm 3 / g.

[0065] Comparative Example 2 The difference from Example 2 is that no thermal conductive filler is added, the total amount remains unchanged, and the mass ratio of biomass fiber to phenolic compound is 1.4:0.125.

[0066] The test results show that the addition of thermal conductive fillers can increase the thermal conductivity of composite carbon aerogels. Under the same test, the thermal conductivity of composite carbon aerogels without thermal conductive fillers is 0.05 W m -1 K -1 , the maximum stress reaches 3.6 MPa, and the CH4 adsorption capacity is 163 cm 3 / g.

[0067] Comparative Example 3 The difference from Example 2 is that the infrared-assisted cross-linking treatment in S3 is omitted.

[0068] The test results show that infrared-assisted cross-linking treatment can enhance the cross-linking degree of composite carbon aerogels and, to a certain extent, contribute to the improvement of mechanical properties and the increase of CH4 adsorption capacity. The maximum stress of composite carbon aerogels without infrared-assisted cross-linking treatment reaches 3.8 MPa, and the methane adsorption capacity is 156 cm 3 / g Comparative Example 4 The difference from Example 2 is that the gradient temperature increase process in S3 is omitted.

[0069] The test results show that the maximum stress of the composite carbon aerogel without gradient temperature treatment reaches 4.4 MPa, and the methane adsorption capacity is 143 cm 3 / g.

[0070] Comparative Example 5 The difference from Example 2 is that the hot pressing process in step S7 is omitted.

[0071] The test results show that the maximum stress of the composite carbon aerogel without hot pressing process reaches 6.6 MPa, and the methane adsorption capacity is 144 cm 3 / g.

[0072] Comparative Example 6 The difference from Example 2 is that the re-carbonization process in step S8 is omitted.

[0073] The test results show that the maximum stress of the composite carbon aerogel without re-carbonization process reaches 6.5 MPa, and the methane adsorption capacity is 186 cm 3 / g.

[0074] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing a natural gas adsorbent with high thermal conductivity and high density, characterized in that: include: The phenolic compound, the aldehyde solution, sodium carbonate and water are mixed uniformly to obtain a precursor solution; adding biomass fiber and thermal conductive filler to the precursor solution in sequence, mixing them evenly to obtain a mixed solution; The mixed solution is first cross-linked by infrared assisted cross-linking method, and then formed into a gel by gradient heating method; The gel is subjected to solvent replacement, and then the organic gel is dried in sections using infrared radiation; and carbonized to obtain a composite carbon aerogel; The composite carbon aerogel is hot-pressed in a mold and carbonized again to obtain the aerogel.

2. The method for preparing a natural gas adsorbent with high thermal conductivity and high density according to claim 1, wherein: The mass ratio of the phenolic compound, aldehyde solution, sodium carbonate and water is 1:(1.5-2.5):(0.003-0.04):(1.6-1.8); Or, the phenols are selected from one or more of phenol, m-cresol, resorcinol, phloroglucinol, o-cresol, o-chlorophenol, and cardanol; Alternatively, the aldehyde is selected from one of formaldehyde, acetaldehyde, furfural, vanillin, benzaldehyde, and glutaraldehyde.

3. The method for preparing a natural gas adsorbent with high thermal conductivity and high density according to claim 1, wherein: The mass ratio of the biomass fiber, the thermal conductive filler and the phenolic compound is (0.2-0.6):1:(0.05-0.2); Alternatively, the biomass fiber is selected from one or more of kapok fiber, pineapple fiber, banana leaf fiber, oil palm fiber, cotton fiber, flax fiber, bamboo pulp fiber, sisal fiber, corn fiber, wheat straw fiber, coconut fiber, and sedge fiber; Alternatively, the thermally conductive filler is selected from one or more of graphene, carbon fiber, expanded graphite, boron nitride, silicon nitride, aluminum oxide, and copper powder.

4. The method for preparing a natural gas adsorbent with high thermal conductivity and high density according to claim 1, wherein: The specific conditions of the infrared-assisted cross-linking method are as follows: the wavelength of the infrared lamp is 2.5-5 μm, the power is 50-300 W, the distance between the infrared source and the liquid surface is 10-30 cm, the temperature is 50-60 ° C, and the exposure time is 20-50 min.

5. The method for preparing a natural gas adsorbent with high thermal conductivity and high density according to claim 1, wherein: The specific conditions of the gradient temperature increase are: first maintaining at 60-62 ° C for 10-14 h, then maintaining at 65-68 ° C for 10-14 h, and finally maintaining at 70-72 ° C for 12-20 h.

6. The method for preparing a natural gas adsorbent with high thermal conductivity and high density according to claim 1, wherein: The specific steps of the solvent replacement are: first replacing the solvent with ethanol, and then replacing the solvent with acetone; Alternatively, the specific steps of the segmented drying are: the infrared lamp has a wavelength of 2-10 μm and a power of 100-380 W; the drying temperature of the first stage is 40-80°C and the exposure time is 10-60 min; the drying temperature of the second stage is 80-150°C, constant temperature, and short-term radiation for 5-15 min.

7. The method for preparing a natural gas adsorbent with high thermal conductivity and high density according to claim 1, wherein: The carbonization conditions are as follows: in an inert atmosphere, keeping the temperature at 350-400°C for 60-80 minutes, then raising the temperature to 800-1200°C and keeping the temperature for 3-6 hours.

8. The method for preparing a natural gas adsorbent with high thermal conductivity and high density according to claim 1, wherein: The hot pressing conditions are as follows: pre-pressing at a pressure of 5-10 MPa for 5-10 minutes; then heating to 120-140°C, applying a pressure of 10-30 MPa, and maintaining the temperature and pressure for 60-90 minutes; Alternatively, the re-carbonization conditions are: in an inert atmosphere, maintaining a constant temperature at 350-400°C for 60-80 min, then raising the temperature to 800-1200°C, and introducing water vapor or carbon dioxide at 170-190 mL / min and maintaining the constant temperature for 60-120 min.

9. A natural gas adsorbent with high thermal conductivity and high density prepared by the method according to any one of claims 1 to 8.

10. Use of the high thermal conductivity, high density natural gas adsorbent according to claim 9 in the field of natural gas adsorption storage.

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