Preparation method of temperature-resistant nano-olefin-based gas desorption agent and application in coal mine drainage

Abstract

The present application relates to the technical field of coal mine safety, and discloses a preparation method of a temperature-resistant nano-olefin-based gas desorber and application of the desorber in coal mine drainage and extraction. The method comprises the following steps: pre-oxidizing natural flake graphite with concentrated sulfuric acid and potassium permanganate to obtain a pre-oxidized graphite phase mixture; extending the layer of the mixture under high temperature and nitrogen protection to obtain a three-dimensional porous nano-olefin-based carrier; immersing the carrier in an ethanol solution containing a silane coupling agent and a polyimide precursor, and then performing ultrasonic treatment and vacuum drying to form a temperature-resistant coating layer; loading palladium chloride and nickel nitrate on the modified carrier by using an equal-volume impregnation method; and finally performing reduction activation treatment in a hydrogen atmosphere to obtain the temperature-resistant nano-olefin-based gas desorber. The desorber has excellent thermal stability and gas adsorption and desorption performance, and is suitable for gas extraction treatment in a high-temperature environment in a coal mine.

Description

Technical Field

[0001] This invention relates to the field of coal mine safety technology, specifically to a method for preparing a heat-resistant nano-olefinic gas desorbent and its application in coal mine drainage. Background Technology

[0002] Coal mine gas hazards are a major safety issue during coal mining. Gas, primarily composed of methane, is adsorbed and stored within the coal seam. Under mining stress, it desorbs and escapes, easily leading to gas exceedances and even explosions. Therefore, effectively promoting the desorption and capture of gas from the coal seam is one of the core aspects of coal mine gas control.

[0003] In existing technologies, desorbents used for gas drainage mostly employ porous materials such as activated carbon and molecular sieves, relying on their physical adsorption properties to enrich gas. However, these materials have significant limitations in application. The underground environment of coal mines is complex, especially during deep mining, where formation temperatures can reach over 50 degrees Celsius, or even higher. Under high-temperature conditions, the physical adsorption capacity of conventional porous materials decreases significantly, resulting in unsatisfactory gas desorption efficiency. Furthermore, the physical adsorption forces are relatively weak, and adsorbed gas molecules are prone to desorption under temperature and pressure fluctuations, posing a risk of secondary release.

[0004] On the other hand, some studies have attempted to introduce metal-active components to alter the adsorption and desorption behavior of gas molecules through catalysis. For example, loading metals such as palladium and nickel, utilizing their activation ability for methane molecules, is expected to enhance the desorption performance of materials. However, directly loading metals onto traditional supports often results in problems such as easy sintering of metal particles and uneven dispersion. In the harsh environment of high temperature and high humidity underground, metal active sites are prone to deactivation, leading to short material lifespan and rapid performance degradation.

[0005] The structural stability of materials is also a major challenge in practical applications. Underground gas extraction operations in coal mines are long-term, and materials need to withstand various stresses such as ground pressure and mechanical vibration. Ordinary porous materials lack sufficient mechanical strength and may experience structural collapse during long-term use, clogging pores, reducing the effective specific surface area, and thus losing their desorption capacity.

[0006] In recent years, carbon nanomaterials such as graphene and graphene oxide have been explored as novel adsorbent carriers due to their high specific surface area, excellent chemical stability, and mechanical strength. However, the original carbon nanomaterials have inert surfaces, and their attraction to gas molecules is mainly physical adsorption. Furthermore, the strong van der Waals forces between the layers easily lead to stacking and aggregation, reducing effective adsorption sites. How to modify the structure and surface of carbon nanomaterials to construct stable composite materials with high desorption activity to meet the needs of the special environment in coal mines remains a key technological challenge. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing a heat-resistant nano-olefinic gas desorbent and its application in coal mine drainage, so as to solve the problems mentioned in the background art.

[0008] To achieve the above objectives, this invention provides a method for preparing a heat-resistant nano-olefinic gas desorbent and its application in coal mine drainage, the method comprising:

[0009] S1. Pretreatment of graphite phase raw materials: Natural flake graphite is mixed with concentrated sulfuric acid and potassium permanganate at a mass ratio of 1:3:0.5 and mechanically stirred for 2-4 hours under ice bath conditions to obtain a pre-oxidized graphite phase mixture.

[0010] S2. High-temperature thermal exfoliation and expansion: The pre-oxidized graphite phase mixture is placed in a tube furnace and heated to 800-1000℃ at a rate of 5-10℃ / min under nitrogen protection, and held for 30-60 minutes to obtain a three-dimensional porous nano-olefinic support.

[0011] S3. Surface temperature resistance modification: The nano-olefin support is immersed in an ethanol solution containing silane coupling agent KH-550 and polyimide precursor. After ultrasonic treatment for 1-2 hours, it is vacuum dried at 60-80℃ to form a temperature-resistant coating layer.

[0012] S4. Loading of active metal components: Palladium chloride and nickel nitrate were loaded onto the modified support at a metal molar ratio of 1:2 using an equal-volume impregnation method, with the total metal loading controlled at 3-5 wt%.

[0013] S5. Reduction and activation treatment: Reduce at 300-400℃ for 2-3 hours in a hydrogen atmosphere to obtain a nanocomposite material with gas adsorption-desorption activity.

[0014] Preferably, the natural flake graphite in step S1 has a particle size of 50-100 μm, a fixed carbon content of ≥99.5%, a concentrated sulfuric acid concentration of 98%, and potassium permanganate of analytical grade.

[0015] Preferably, the heating program of the tubular furnace in step S2 is as follows: from room temperature, the temperature is increased to 300°C at 5°C / min and held for 20 min, and then increased to the target temperature at 10°C / min, while the nitrogen flow rate is maintained at 100-200 mL / min.

[0016] Preferably, the ethanol solution in step S3 is prepared by mixing silane coupling agent KH-550, polyimide prepolymer and anhydrous ethanol in a mass ratio of 1:2:20, with an ultrasonic power of 400-600W and a frequency of 40kHz.

[0017] Preferably, the specific operation of the medium-volume impregnation method in step S4 includes: placing the nano-olefin support in a mixed solution of 0.1 mol / L palladium chloride and 0.2 mol / L nickel nitrate, impregnating for 12 hours, and then drying at 110°C.

[0018] Preferably, the reduction and activation process in step S5 uses programmed temperature control, first raising the temperature from room temperature to 200°C at 2°C / min to remove physically adsorbed water, and then raising the temperature to the target temperature at 5°C / min for reduction.

[0019] Preferably, the process further includes step S6, surface hydrophobic modification, in which the reduced material is immersed in a toluene solution of perfluorodecyltriethoxysilane and refluxed at 80°C for 4 hours to make the water contact angle of the material surface ≥120°.

[0020] Preferably, in step S6, the concentration of perfluorodecyltriethoxysilane is 0.5-1.0 wt%, the mass ratio of toluene to material is 10:1, and the material is washed three times with anhydrous ethanol after reflux.

[0021] Preferably, the thickness of the heat-resistant coating layer formed in step S3 is 10-50 nm, so that the material maintains more than 90% of its specific surface area at 300°C.

[0022] Preferably, the present invention also includes the application of a heat-resistant nano-olefinic gas desorber prepared by the above method in coal mine drainage.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] The three-dimensional porous nano-olefin-based support prepared in this invention possesses a unique interconnected porous structure that significantly increases the specific surface area of ​​the material, providing abundant space and diffusion channels for gas molecules. This open-pore structure effectively alleviates the problem of nanosheet re-stacking, allowing full utilization of the internal surface. The support framework itself possesses excellent mechanical strength and structural stability, enabling it to adapt to the complex mechanical environment downhole. The heat-resistant coating layer constructed on the material surface acts as a robust protective shell, isolating the nano-olefin-based support from the harsh high-temperature environment to a certain extent. It effectively enhances the overall thermal stability of the material, allowing the active components to maintain their structure and function at higher temperatures. Simultaneously, the presence of this coating layer may have a positive impact on the diffusion and interaction of gas molecules on the material surface.

[0025] High dispersion of palladium and nickel bimetallic active components on the support surface was achieved through equal-volume impregnation. The potential synergistic effect between the bimetals enhances the activation ability for gas molecules, particularly methane. This activation alters the traditional simple physical adsorption mode, promoting the desorption of gas from the coal and its transformation behavior on the material surface, thus making the desorption process more efficient and thorough. The reduction activation process not only transforms the metal precursor into a catalytically active metallic state but may also, to some extent, repair structural defects in the nanomaterials and optimize their electronic properties. This helps to enhance the interaction between the material support and the active components, improving the overall conductivity and structural integrity of the composite material. Attached Figure Description

[0026] Figure 1 This diagram illustrates the working steps of a method for preparing a heat-resistant nano-olefin-based gas desorbent according to the present invention. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to specific embodiments and comparative examples. The following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. All technologies implemented based on the above description of the present invention fall within the scope of protection of the present invention.

[0028] The raw materials used in this embodiment are as follows: natural flake graphite (particle size 50-100μm, fixed carbon content ≥99.5%, Qingdao Graphite Co., Ltd.); concentrated sulfuric acid (concentration 98%, analytical grade, Sinopharm Chemical Reagent Co., Ltd.); potassium permanganate (analytical grade, Sinopharm Chemical Reagent Co., Ltd.); silane coupling agent KH-550 (industrial grade, purity ≥98%, Nanjing Shuguang Chemical Group Co., Ltd.); polyimide prepolymer (model PI-2500, solid content 20%, Changchun Gaoqi Polyimide Materials Co., Ltd.); anhydrous ethanol (analytical grade, purity ≥99.5%). ≥99.7%, Sinopharm Chemical Reagent Co., Ltd.); Palladium chloride (analytical grade, purity ≥99.5%, Shanghai Aladdin Biochemical Technology Co., Ltd.); Nickel nitrate (analytical grade, purity ≥99.0%, Shanghai Aladdin Biochemical Technology Co., Ltd.); Perfluorodecyltriethoxysilane (purity ≥97%, Shanghai Maclean Biochemical Technology Co., Ltd.); Toluene (analytical grade, purity ≥99.5%, Sinopharm Chemical Reagent Co., Ltd.); Nitrogen (purity ≥99.999%, local gas company); Hydrogen (purity ≥99.999%, local gas company).

[0029] The performance testing methods in this embodiment and comparative example are as follows:

[0030] Specific surface area test: The specific surface area of ​​the material was tested using the liquid nitrogen adsorption-desorption method (BET method) and a fully automated specific surface area and porosity analyzer (model ASAP2460, Micron Instruments, USA). Before the test, the sample was degassed at 150°C for 4 hours.

[0031] Temperature resistance test: The sample was placed in a muffle furnace and kept at 300℃, 400℃ and 500℃ for 2 hours respectively. After cooling to room temperature, its specific surface area retention rate was tested. Specific surface area retention rate = (specific surface area after high temperature treatment / specific surface area before treatment) × 100%.

[0032] Gas desorption performance test: A self-built gas desorption simulation device was used. 1g of sample was placed in the reaction vessel, and methane gas was introduced until the pressure reached 0.8MPa. After adsorption equilibrium was reached at a constant temperature of 25℃, the amount of methane desorbed at different times was recorded, and the desorption rate (mL·g) was calculated. -1 ·min -1 ) and cumulative desorption volume (mL·g -1 The test lasted 120 minutes.

[0033] Hydrophobicity test: The water contact angle of the sample surface was tested using a contact angle meter (model SL200KB, Shanghai Solon Information Technology Co., Ltd.). Five different locations were tested for each sample, and the average value was taken.

[0034] Mechanical stability test: The sample was placed in a vibratory mill and vibrated at 200 r / min for 30 minutes. The change rate of specific surface area and the retention rate of desorption performance of the sample before and after vibration were tested to evaluate the mechanical stability.

[0035] Example 1

[0036] See Figure 1 A method for preparing a heat-resistant nano-olefinic gas desorbent includes the following steps:

[0037] S1. Pretreatment of graphite phase raw materials: Weigh 10g of natural flake graphite (particle size 50μm, fixed carbon content 99.6%), 30g of 98% concentrated sulfuric acid, and 5g of analytical grade potassium permanganate, and place them in a 500mL three-necked flask. Place the three-necked flask in an ice bath (temperature controlled at 0-5℃), turn on the mechanical stirrer, and stir at a stirring speed of 300r / min for 2 hours. During the process, control the system temperature to not exceed 10℃. After stirring, a pre-oxidized graphite phase mixture is obtained and set aside for later use.

[0038] S2. High-Temperature Thermal Exfoliation and Expansion: The pre-oxidized graphite phase mixture obtained in step S1 is uniformly spread in a quartz boat, placed in a tube furnace, and the furnace door is closed. Nitrogen gas is introduced for displacement for 30 minutes at a flow rate of 100 mL / min. After displacement, the tube furnace heating program is started: from room temperature to 300°C at a rate of 5°C / min, held for 20 minutes; then at a rate of 10°C / min to 800°C, held for 30 minutes after reaching the target temperature. After holding, the heating device is turned off, and nitrogen gas is continued to be introduced until the tube furnace cools naturally to room temperature. The product is then removed, ground, and passed through a 200-mesh sieve to obtain a three-dimensional porous nano-olefinic support.

[0039] S3. Surface Temperature Resistance Modification: Prepare an ethanol solution by weighing 1g of silane coupling agent KH-550, 2g of polyimide prepolymer, and 20g of anhydrous ethanol, placing them in a 250mL beaker, and stirring until completely dissolved to obtain a modified solution. Immerse 10g of the nano-olefinic support obtained in step S2 into the above modified solution, transfer it to an ultrasonic cleaner, set the ultrasonic power to 400W, the frequency to 40kHz, and ultrasonically treat for 1 hour. After ultrasonic treatment, transfer the mixture to a vacuum drying oven, set the temperature to 60℃, the vacuum degree to -0.09MPa, and dry for 8 hours to form a temperature-resistant coating layer, obtaining the modified nano-olefinic support. The thickness of this temperature-resistant coating layer is measured to be 10nm.

[0040] S4. Loading of Metal Active Components: The metal active components were loaded using an equal-volume impregnation method. First, a mixed metal salt solution was prepared. A certain amount of palladium chloride and nickel nitrate were weighed, ensuring a molar ratio of 1:2. These were dissolved in deionized water to prepare a 0.1 mol / L palladium chloride and 0.2 mol / L nickel nitrate mixed solution, ensuring the volume of the mixed solution was equal to the pore volume of the nano-olefin support (the support pore volume was measured to be 1.2 mL / g, therefore 12 mL of mixed solution was prepared). 10 g of the modified nano-olefin support obtained in step S3 was placed in the mixed metal salt solution and immersed at room temperature for 12 hours. After impregnation, the sample was transferred to a forced-air drying oven and dried at 110°C for 6 hours to obtain the precursor loaded with the metal active components. The total metal loading was calculated to be 3 wt%.

[0041] S5. Reduction and Activation Treatment: The precursor obtained in step S4 is placed in a tube furnace, the furnace door is closed, and hydrogen gas is introduced for displacement for 30 minutes at a flow rate of 50 mL / min. After displacement, a programmed temperature-controlled reduction is initiated: the temperature is increased from room temperature to 200°C at a rate of 2°C / min and held for 1 hour to remove physically adsorbed water; then the temperature is increased to 300°C at a rate of 5°C / min, and held for 2 hours after reaching the target temperature for reduction and activation. After reduction, the heating device is turned off, and hydrogen gas is continued to be introduced until the tube furnace cools to room temperature, yielding the primary nanocomposite material.

[0042] S6. Surface Hydrophobic Modification: Prepare a hydrophobic modification solution by dissolving 0.5 wt% of perfluorodecyltriethoxysilane (based on toluene mass) in toluene to obtain a hydrophobic modification solution, controlling the mass ratio of toluene to the primary nanocomposite material to be 10:1. Immerse 10 g of the primary nanocomposite material obtained in step S5 into the above hydrophobic modification solution, transfer it to a reflux apparatus, set the temperature to 80℃, and reflux for 4 hours. After the reaction is complete, remove the sample, wash it three times with anhydrous ethanol, each time using 50 mL, and then dry it in a 110℃ forced-air drying oven for 4 hours to obtain a heat-resistant nano-olefinic gas desorbent.

[0043] Example 2

[0044] A method for preparing a heat-resistant nano-olefinic gas desorbent includes the following steps:

[0045] S1. Pretreatment of graphite phase raw materials: Weigh 10g of natural flake graphite (particle size 80μm, fixed carbon content 99.7%), 30g of 98% concentrated sulfuric acid, and 5g of analytical grade potassium permanganate, and place them in a 500mL three-necked flask. Place the three-necked flask in an ice bath (temperature controlled at 0-5℃), turn on the mechanical stirrer, and stir at a stirring speed of 400r / min for 3 hours. During the process, control the system temperature to not exceed 10℃. After stirring, a pre-oxidized graphite phase mixture is obtained and set aside for later use.

[0046] S2. High-Temperature Thermal Exfoliation and Expansion: The pre-oxidized graphite phase mixture obtained in step S1 is uniformly spread in a quartz boat, placed in a tube furnace, and the furnace door is closed. Nitrogen gas is introduced for displacement for 30 minutes at a flow rate of 150 mL / min. After displacement, the tube furnace heating program is started: from room temperature to 300°C at a rate of 5°C / min, held for 20 minutes; then increased to 900°C at a rate of 10°C / min, held for 45 minutes after reaching the target temperature. After holding, the heating device is turned off, and nitrogen gas is continued to be introduced until the tube furnace cools naturally to room temperature. The product is then removed, ground, and passed through a 200-mesh sieve to obtain a three-dimensional porous nano-olefinic support.

[0047] S3. Surface Temperature Resistance Modification: Prepare an ethanol solution by weighing 1g of silane coupling agent KH-550, 2g of polyimide prepolymer, and 20g of anhydrous ethanol, placing them in a 250mL beaker, and stirring until completely dissolved to obtain a modified solution. Immerse 10g of the nano-olefinic support obtained in step S2 into the above modified solution, transfer it to an ultrasonic cleaner, set the ultrasonic power to 500W, the frequency to 40kHz, and ultrasonically treat for 1.5 hours. After ultrasonic treatment, transfer the mixture to a vacuum drying oven, set the temperature to 70℃, the vacuum degree to -0.09MPa, and dry for 8 hours to form a temperature-resistant coating layer, obtaining the modified nano-olefinic support. The thickness of this temperature-resistant coating layer is measured to be 30nm.

[0048] S4. Loading of Metal Active Components: The metal active components were loaded using an equal-volume impregnation method. First, a mixed metal salt solution was prepared. A certain amount of palladium chloride and nickel nitrate were weighed, ensuring a molar ratio of 1:2. These were dissolved in deionized water to prepare a 0.1 mol / L palladium chloride and 0.2 mol / L nickel nitrate mixed solution, ensuring the volume of the mixed solution was equal to the pore volume of the nano-olefin support (the support pore volume was measured to be 1.3 mL / g, therefore 13 mL of mixed solution was prepared). 10 g of the modified nano-olefin support obtained in step S3 was placed in the mixed metal salt solution and immersed at room temperature for 12 hours. After impregnation, the sample was transferred to a forced-air drying oven and dried at 110℃ for 6 hours to obtain the precursor loaded with the metal active components. The total metal loading was calculated to be 4 wt%.

[0049] S5. Reduction and Activation Treatment: The precursor obtained in step S4 is placed in a tube furnace, the furnace door is closed, and hydrogen gas is introduced for displacement for 30 minutes at a flow rate of 50 mL / min. After displacement, a temperature-controlled reduction program is started: the temperature is increased from room temperature to 200°C at a rate of 2°C / min and held for 1 hour to remove physically adsorbed water; then the temperature is increased to 350°C at a rate of 5°C / min and held for 2.5 hours after reaching the target temperature for reduction and activation. After reduction, the heating device is turned off, and hydrogen gas is continued to be introduced until the tube furnace cools to room temperature, yielding the primary nanocomposite material.

[0050] S6. Surface Hydrophobic Modification: Prepare a hydrophobic modification solution by dissolving 0.8 wt% of perfluorodecyltriethoxysilane (based on toluene mass) in toluene to obtain a hydrophobic modification solution, controlling the mass ratio of toluene to the primary nanocomposite material to be 10:1. Immerse 10 g of the primary nanocomposite material obtained in step S5 into the above hydrophobic modification solution, transfer it to a reflux apparatus, set the temperature to 80℃, and reflux for 4 hours. After the reaction is complete, remove the sample, wash it three times with anhydrous ethanol, each time using 50 mL, and then dry it in a 110℃ forced-air drying oven for 4 hours to obtain a heat-resistant nano-olefinic gas desorbent.

[0051] Example 3

[0052] A method for preparing a heat-resistant nano-olefinic gas desorbent includes the following steps:

[0053] S1. Pretreatment of graphite phase raw materials: Weigh 10g of natural flake graphite (particle size 100μm, fixed carbon content 99.8%), 30g of 98% concentrated sulfuric acid, and 5g of analytical grade potassium permanganate, and place them in a 500mL three-necked flask. Place the three-necked flask in an ice bath (temperature controlled at 0-5℃), turn on the mechanical stirrer, and stir at a stirring speed of 500r / min for 4 hours. During the process, control the system temperature to not exceed 10℃. After stirring, a pre-oxidized graphite phase mixture is obtained and set aside for later use.

[0054] S2. High-Temperature Thermal Exfoliation and Expansion: The pre-oxidized graphite phase mixture obtained in step S1 is uniformly spread in a quartz boat, placed in a tube furnace, and the furnace door is closed. Nitrogen gas is introduced for displacement for 30 minutes at a flow rate of 200 mL / min. After displacement, the tube furnace heating program is started: from room temperature to 300°C at a rate of 5°C / min, held for 20 minutes; then increased to 1000°C at a rate of 10°C / min, held for 60 minutes after reaching the target temperature. After holding, the heating device is turned off, and nitrogen gas is continued to be introduced until the tube furnace cools naturally to room temperature. The product is then removed, ground, and passed through a 200-mesh sieve to obtain a three-dimensional porous nano-olefinic support.

[0055] S3. Surface Temperature Resistance Modification: Prepare an ethanol solution by weighing 1g of silane coupling agent KH-550, 2g of polyimide prepolymer, and 20g of anhydrous ethanol into a 250mL beaker and stirring until completely dissolved to obtain a modified solution. Immerse 10g of the nano-olefinic support obtained in step S2 into the above modified solution and transfer it to an ultrasonic cleaner. Set the ultrasonic power to 600W and the frequency to 40kHz, and ultrasonically treat for 2 hours. After ultrasonic treatment, transfer the mixture to a vacuum drying oven, set the temperature to 80℃ and the vacuum degree to -0.09MPa, and dry for 8 hours to form a temperature-resistant coating layer, obtaining the modified nano-olefinic support. The thickness of the temperature-resistant coating layer is measured to be 50nm.

[0056] S4. Loading of Metal Active Components: The metal active components were loaded using an equal-volume impregnation method. First, a mixed metal salt solution was prepared. A certain amount of palladium chloride and nickel nitrate were weighed, ensuring a molar ratio of 1:2. These were dissolved in deionized water to prepare a 0.1 mol / L palladium chloride and 0.2 mol / L nickel nitrate mixed solution, ensuring the volume of the mixed solution was equal to the pore volume of the nano-olefin support (the support pore volume was measured to be 1.4 mL / g, therefore 14 mL of mixed solution was prepared). 10 g of the modified nano-olefin support obtained in step S3 was placed in the mixed metal salt solution and immersed at room temperature for 12 hours. After impregnation, the sample was transferred to a forced-air drying oven and dried at 110℃ for 6 hours to obtain the precursor loaded with the metal active components. The total metal loading was calculated to be 5 wt%.

[0057] S5. Reduction and Activation Treatment: The precursor obtained in step S4 is placed in a tube furnace, the furnace door is closed, and hydrogen gas is introduced for displacement for 30 minutes at a flow rate of 50 mL / min. After displacement, a programmed temperature-controlled reduction is initiated: the temperature is increased from room temperature to 200°C at a rate of 2°C / min and held for 1 hour to remove physically adsorbed water; then the temperature is increased to 400°C at a rate of 5°C / min, and held for 3 hours after reaching the target temperature for reduction and activation. After reduction, the heating device is turned off, and hydrogen gas is continued to be introduced until the tube furnace cools to room temperature, yielding the primary nanocomposite material.

[0058] S6. Surface Hydrophobic Modification: Prepare a hydrophobic modification solution by dissolving 1.0 wt% of perfluorodecyltriethoxysilane (based on toluene mass) in toluene to obtain a hydrophobic modification solution, controlling the mass ratio of toluene to the primary nanocomposite material to be 10:1. Immerse 10 g of the primary nanocomposite material obtained in step S5 into the above hydrophobic modification solution, transfer it to a reflux apparatus, set the temperature to 80℃, and reflux for 4 hours. After the reaction is complete, remove the sample, wash it three times with anhydrous ethanol, each time using 50 mL, and then dry it in a 110℃ forced-air drying oven for 4 hours to obtain a heat-resistant nano-olefinic gas desorbent.

[0059] Comparative Example 1

[0060] The difference between this comparative example and Example 2 is that the surface temperature resistance modification treatment in step S3 is omitted. The remaining steps and process parameters are completely consistent with Example 2, as follows:

[0061] S1. Pretreatment of graphite phase raw materials: Same as step S1 in Example 2.

[0062] S2, High-temperature thermal peeling and expansion: Same as step S2 in Example 2.

[0063] S3. Loading of active metal components: The active metal components are loaded using the equal volume impregnation method, and the process parameters are the same as those in step S4 of Example 2.

[0064] S4. Reduction and activation treatment: Same as step S5 in Example 2.

[0065] S5. Surface hydrophobic modification: Same as step S6 in Example 2, to obtain a gas desorbent sample.

[0066] Comparative Example 2

[0067] The difference between this comparative example and Example 2 is that only palladium chloride is used as the active metal component, without the addition of nickel nitrate, and the total metal loading is still 4 wt%. The remaining steps and process parameters are completely consistent with Example 2, as follows:

[0068] S1. Pretreatment of graphite phase raw materials: Same as step S1 in Example 2.

[0069] S2, High-temperature thermal peeling and expansion: Same as step S2 in Example 2.

[0070] S3. Surface temperature resistance modification: Same as step S3 in Example 2.

[0071] S4. Loading of metal active components: The metal active components were loaded using an equal-volume impregnation method. A 0.16 mol / L palladium chloride solution was prepared, ensuring that the solution volume was equal to the pore volume of the nano-olefin support (13 mL). 10 g of the modified nano-olefin support was immersed in the solution and impregnated for 12 hours. Then, it was dried at 110 °C for 6 hours, and the total metal loading was 4 wt%.

[0072] S5. Reduction and activation treatment: Same as step S5 in Example 2.

[0073] S6. Surface hydrophobic modification: Same as step S6 in Example 2, to obtain a gas desorbent sample.

[0074] Comparative Example 3

[0075] The difference between this comparative example and Example 2 is that the surface hydrophobic modification treatment in step S6 is not performed. The remaining steps and process parameters are completely the same as in Example 2, as follows:

[0076] S1. Pretreatment of graphite phase raw materials: Same as step S1 in Example 2.

[0077] S2, High-temperature thermal peeling and expansion: Same as step S2 in Example 2.

[0078] S3. Surface temperature resistance modification: Same as step S3 in Example 2.

[0079] S4, Loading of metal active components: Same as step S4 in Example 2.

[0080] S5. Reduction and activation treatment: Same as step S5 in Example 2, to obtain a gas desorbent sample.

[0081] The specific surface area, temperature resistance, and gas desorption performance of the gas desorbent samples prepared in Examples 1-3 and Comparative Examples 1-3 were tested. The test results are shown in Tables 1-3 below.

[0082] Table 1: Test results of specific surface area and temperature resistance of each sample

[0083]

[0084] As shown in Table 1, the samples prepared in Examples 1-3 all exhibit excellent specific surface area and temperature resistance. Among them, Sample 2 has the largest initial specific surface area, reaching 956 m² / g. This is attributed to the optimized combination of its thermal exfoliation temperature (900℃), ultrasonic power (500W), and metal loading (4wt%), which resulted in a richer three-dimensional porous structure on the carrier. Furthermore, the active metal components were uniformly dispersed on the carrier surface and within the pores, without significant pore blockage. After high-temperature treatment at 300℃, the specific surface area retention rates of Samples 1-3 all exceeded 91%, with Sample 2 reaching 92.8%, indicating that the polyimide-KH-550 composite coating layer formed by surface temperature modification played a significant role. This coating layer possesses excellent high-temperature stability, effectively inhibiting the aggregation and structural collapse of the nano-olefinic carrier at high temperatures, while protecting the active metal components from oxidation, thereby maintaining the porous structure and specific surface area of ​​the material.

[0085] Comparing Example 2 and Comparative Example 1, it can be seen that the specific surface area retention rate of the sample in Comparative Example 1 without surface temperature resistance modification was only 72.7% after treatment at 300℃, and the retention rates after treatment at 400℃ and 500℃ further decreased to 48.0% and 23.1%, respectively, significantly lower than that of Example 2. This is because without the protection of the temperature-resistant coating layer, the nano-olefinic support is prone to interlayer aggregation at high temperatures, and the pore structure is destroyed. At the same time, the active metal components oxidize and sinter at high temperatures, further blocking the pores, resulting in a sharp decrease in specific surface area. Therefore, the surface temperature resistance modification in step S3 is the key to improving the temperature resistance performance of the material.

[0086] The temperature resistance of Comparative Example 2 was similar to that of Examples 1-3. After treatment at 300℃, the specific surface area retention rate was 91.9%, indicating that the type and ratio of the active metal components had little impact on the temperature resistance of the material, and that the temperature resistance was mainly determined by the surface coating layer. The temperature resistance of Comparative Example 3 was basically consistent with that of Example 2, indicating that surface hydrophobic modification had no significant negative impact on the specific surface area and temperature resistance of the material. The hydrophobic modified layer only adhered to the material surface and did not damage the porous structure of the carrier or the integrity of the temperature-resistant coating layer.

[0087] As the processing temperature increased, the specific surface area and retention rate of all samples showed a decreasing trend, but the decrease in Examples 1-3 was significantly less than that in Comparative Example 1. At a high temperature of 500℃, the specific surface area retention rate of Examples 1-3 remained above 65%, while that of Comparative Example 1 was only 23.1%, further demonstrating that the heat-resistant coating prepared by this invention can protect the structural stability of materials within a high temperature range and meet the usage requirements of high-temperature environments in underground coal mines.

[0088] Table 2: Test results of gas desorption performance of each sample

[0089]

[0090] As shown in Table 2, the samples prepared in Examples 1-3 all exhibited excellent gas desorption performance and maintained high stability of desorption performance even after high-temperature treatment. Among them, the sample in Example 2 showed the best gas desorption performance, with a desorption rate of 3.21 mL·g⁻¹ in 10 min. -1 ·min -1 The cumulative desorption volume over 120 minutes was 172.3 mL·g. -1 After treatment at 300℃, the desorption performance retention rate was 93.2%. This excellent performance stems from the synergistic effect of the materials: the three-dimensional porous nano-olefinic support provides an ultra-large specific surface area and abundant pore structure, providing sufficient active sites and transport channels for the adsorption and desorption of gas molecules; the surface heat-resistant coating layer protects the stability of the support structure and the metal active component at high temperatures; the bimetallic active component formed by loading palladium chloride and nickel nitrate in a 1:2 molar ratio can effectively reduce the adsorption energy barrier of gas molecules, promote the desorption of gas molecules from the support surface, and improve the desorption rate and cumulative desorption amount.

[0091] Comparing Example 2 and Comparative Example 1, it can be seen that the gas desorption performance of the sample in Comparative Example 1 at room temperature is similar to that in Example 2, with a cumulative desorption amount of 165.4 mL·g in 120 min. -1 However, after treatment at 300℃, the cumulative desorption amount decreased to 98.3 mL·g. -1 The desorption retention rate in Comparative Example 1 was only 59.4%, far lower than that in Example 2. This is because Comparative Example 1 lacked a heat-resistant coating layer, leading to structural collapse and oxidation sintering of the active metal components at high temperatures. This resulted in a reduction of active sites and pore blockage, making it difficult for gas molecules to achieve adsorption-desorption cycles, causing a sharp decline in desorption performance. Therefore, surface heat-resistant modification not only improves the structural stability of the material but also ensures the stability of its gas desorption performance under high-temperature conditions, which is crucial for its application in high-temperature conditions in coal mines.

[0092] Comparative Example 2, which used only palladium chloride as the active metal component, exhibited significantly lower gas desorption performance than Examples 1-3, with a cumulative desorption amount of only 132.7 mL·g over 120 minutes.-1 The desorption rate also decreased significantly. This indicates that the bimetallic system formed by palladium chloride and nickel nitrate has a synergistic catalytic effect. The introduction of nickel can regulate the electronic structure of palladium, enhance the interaction between the active metal component and gas molecules, thereby lowering the desorption energy barrier and improving desorption performance. A single active metal component cannot achieve the synergistic effect of the bimetallic system, further proving the rationality of the ratio design of the active metal components in this invention.

[0093] The sample in Comparative Example 3 was not modified to be hydrophobic on the surface. Its gas desorption performance and high-temperature stability were basically the same as those in Example 2. The cumulative desorption amount at room temperature for 120 min was 170.5 mL·g. -1 The retention rate after high-temperature treatment was 93.0%, indicating that hydrophobic modification had no significant impact on gas desorption performance. However, it should be noted that the main function of hydrophobic modification is to improve the stability of the material in humid environments. The underground environment of coal mines is humid, and hydrophobic modification can prevent the material from clogging its pores due to water absorption, thereby maintaining the stability of long-term desorption performance. This advantage will be demonstrated in practical applications.

[0094] From the trend of desorption rate changes, the desorption rate of all samples gradually decreased with time. The desorption rate was faster in the early stage (0-30 min) and tended to level off in the later stage (60-120 min), which is consistent with the kinetic law of gas desorption. The desorption rates of Examples 1-3 were higher than those of Comparative Example 2 at all time periods, and the rate decrease was smaller after high-temperature treatment, further verifying the advantages of the desorbent prepared in this invention in terms of gas desorption efficiency and high-temperature stability.

[0095] Table 3: Test results of hydrophobic properties and mechanical stability of each sample

[0096]

[0097] As shown in Table 3, after surface hydrophobic modification, the water contact angles of samples 1-3 and Comparative Examples 1-2 all reached over 120°, exhibiting excellent hydrophobic properties. In contrast, the water contact angle of Comparative Example 3, which was not modified, was only 78.2°, indicating it is a hydrophilic material. Sample 3 exhibited the largest water contact angle at 131.6°. This is because it was modified with 1.0 wt% perfluorodecyltriethoxysilane, and the higher concentration of hydrophobic reagent formed a denser hydrophobic layer on the material surface, effectively reducing the surface energy and improving the hydrophobic effect. Sample 2 had a water contact angle of 128.3°, which meets the requirements of the humid environment in underground coal mines, preventing water absorption and aggregation or water blockage of the pores.

[0098] Mechanical stability tests showed that after vibration treatment, the specific surface area and gas desorption performance of all samples decreased slightly, but the changes were small. The specific surface area change rate was within -2.0%, and the desorption performance retention rate was above 96%, indicating that the desorbent prepared by this invention has excellent mechanical stability. Among them, the sample of Example 3 had the best mechanical stability, with a specific surface area change rate of -1.4% and a desorption performance retention rate of 97.8% after vibration. This is related to its experimental parameters: the higher thermal exfoliation temperature (1000℃) and the longer holding time (60 minutes) enabled the nano-olefinic carrier to form a more robust three-dimensional porous structure. The surface heat-resistant coating layer and hydrophobic layer further enhanced the structural integrity of the material, thereby improving mechanical stability.

[0099] The mechanical stability of the sample in Example 2 was slightly better than that in Example 1. The retention rate of desorption performance after vibration was 97.4%, higher than the 96.6% in Example 1. This is because the ultrasonic treatment time (1.5 hours) and reduction temperature (350℃) in Example 2 were more optimized, resulting in a tighter bond between the active metal component and the carrier. The coating thickness (30nm) was also moderate, ensuring both temperature resistance and enhanced structural strength. Comparing Example 2 and Comparative Example 3, it can be seen that hydrophobic modification had no significant impact on mechanical stability. The specific surface area change rate and desorption performance retention rate were basically the same for both, indicating that the adhesion of the hydrophobic layer did not affect the overall structural stability of the material.

[0100] The mechanical stability of the samples in Comparative Examples 1-2 is similar to that in Examples 1-3, indicating that the surface temperature modification and the proportion of active metal components have little impact on mechanical stability. The mechanical stability of the material is mainly determined by the structure of the nano-olefinic carrier itself. The three-dimensional porous nano-olefinic carrier prepared by high-temperature thermal exfoliation and layer expansion in this invention has high structural strength and can withstand mechanical actions such as vibration and impact in coal mines, and is not prone to structural damage, thus ensuring the long-term stable operation of the material.

[0101] It is important to emphasize that hydrophobic properties are crucial for underground coal mine applications. Comparative Example 3 is a hydrophilic material, which easily absorbs water in humid environments, leading to pore blockage and a continuous decline in desorption performance over long-term use. In contrast, Examples 1-3 and Comparative Examples 1-2 exhibit excellent hydrophobic properties, effectively resisting the effects of humid environments, maintaining pore patency and exposure of active sites, thereby ensuring long-term stable gas desorption performance.

[0102] Based on the test results and analysis in the three tables above, the method for preparing the heat-resistant nano-olefinic gas desorbent provided by this invention has the following advantages:

[0103] First, the three-dimensional porous nano-olefinic support prepared by pretreatment of graphite phase raw materials and high-temperature thermal exfoliation and layer expansion possesses an ultra-large specific surface area and abundant pore structure, providing sufficient active sites and transport channels for gas desorption, thus laying the foundation for excellent desorption performance. The initial specific surface area of ​​the sample in Example 2 reached 956 m² / g, providing favorable structural conditions for the adsorption and desorption of gas molecules.

[0104] Secondly, the polyimide-KH-550 composite coating layer formed by surface temperature modification significantly improves the high-temperature stability of the material. After high-temperature treatment at 300℃, the specific surface area retention rate of samples in Examples 1-3 all exceeded 91%, and the desorption performance retention rate exceeded 91%, while the retention rate of the unmodified Comparative Example 1 sample was only 59.4%. This indicates that the coating layer can effectively inhibit carrier agglomeration and oxidation of active metal components, ensuring structural and performance stability under high-temperature conditions.

[0105] Third, the bimetallic active component formed by loading palladium chloride and nickel nitrate in a 1:2 molar ratio exhibits a synergistic catalytic effect, significantly improving the gas desorption rate and cumulative desorption capacity compared to a single metal component (Comparative Example 2). In Example 2, the cumulative desorption capacity reached 172.3 mL·g in 120 min. -1 This represents an increase of over 30% compared to control 2.

[0106] Fourth, the surface hydrophobic modification enables the material to achieve a water contact angle of over 120°, exhibiting excellent hydrophobic properties. This allows it to adapt to the humid environment of underground coal mines, preventing water absorption and blockage of the pores. At the same time, the material has good mechanical stability, with a desorption retention rate of over 96% after vibration, meeting the usage requirements of complex underground working conditions.

[0107] Example 2 is the optimal example, with the most reasonable combination of process parameters (thermal stripping temperature 900℃, holding time 45 minutes, ultrasonic power 500W, treatment time 1.5 hours, metal loading 4wt%, reduction temperature 350℃, holding time 2.5 hours, hydrophobic reagent concentration 0.8wt%). The prepared desorbent achieved optimal levels in specific surface area, temperature resistance, gas desorption performance, hydrophobicity, and mechanical stability. After treatment at 300℃, the specific surface area retention rate was 92.8%, the desorption performance retention rate was 93.2%, and the cumulative desorption amount in 120 minutes was 172.3 mL·g. -1 With a water contact angle of 128.3° and a desorption performance retention rate of 97.4% after vibration, it can be efficiently and stably applied in the complex environment of high temperature, humidity and high vibration in underground coal mines to achieve rapid desorption and drainage of gas and ensure the safety of coal mine production.

[0108] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a heat-resistant nano-olefinic gas desorbent, characterized in that, Includes the following steps: S1. Pretreatment of graphite phase raw materials: Natural flake graphite is mixed with concentrated sulfuric acid and potassium permanganate at a mass ratio of 1:3:0.5 and mechanically stirred for 2-4 hours under ice bath conditions to obtain a pre-oxidized graphite phase mixture. S2. High-temperature thermal exfoliation and expansion: The pre-oxidized graphite phase mixture is placed in a tube furnace and heated to 800-1000℃ at a rate of 5-10℃ / min under nitrogen protection, and held for 30-60 minutes to obtain a three-dimensional porous nano-olefinic support. S3. Surface temperature resistance modification: The nano-olefin support is immersed in an ethanol solution containing silane coupling agent KH-550 and polyimide prepolymer, ultrasonically treated for 1-2 hours, and then vacuum dried at 60-80℃ to form a temperature-resistant coating layer. S4. Loading of active metal components: Palladium chloride and nickel nitrate were loaded onto the modified support at a metal molar ratio of 1:2 using an equal-volume impregnation method, with the total metal loading controlled at 3-5 wt%. S5. Reduction and activation treatment: Reduce at 300-400℃ for 2-3 hours in a hydrogen atmosphere to obtain a nanocomposite material with gas adsorption-desorption activity.

2. The method for preparing a heat-resistant nano-olefinic gas desorbent according to claim 1, characterized in that: The natural flake graphite mentioned in step S1 has a particle size of 50-100 μm, a fixed carbon content of ≥99.5%, a concentrated sulfuric acid concentration of 98%, and potassium permanganate of analytical grade.

3. The method for preparing a heat-resistant nano-olefinic gas desorbent according to claim 1, characterized in that: The specific heating program for the tubular furnace in step S2 is as follows: heat from room temperature to 300℃ at 5℃ / min and hold for 20min, then heat to the target temperature at 10℃ / min, while maintaining a nitrogen flow rate of 100-200mL / min.

4. The method for preparing a heat-resistant nano-olefinic gas desorbent according to claim 1, characterized in that: The ethanol solution in step S3 is prepared by mixing silane coupling agent KH-550, polyimide prepolymer and anhydrous ethanol in a mass ratio of 1:2:20, with an ultrasonic power of 400-600W and a frequency of 40kHz.

5. The method for preparing a heat-resistant nano-olefinic gas desorbent according to claim 1, characterized in that: The specific operation of step S4, the medium-volume impregnation method, includes: placing the nano-olefin support in a mixed solution of 0.1 mol / L palladium chloride and 0.2 mol / L nickel nitrate, impregnating for 12 hours, and then drying at 110°C.

6. The method for preparing a heat-resistant nano-olefinic gas desorbent according to claim 1, characterized in that: In step S5, the reduction and activation process adopts programmed temperature control. First, the temperature is raised from room temperature to 200℃ at a rate of 2℃ / min to remove physically adsorbed water, and then the temperature is raised to the target temperature at a rate of 5℃ / min for reduction.

7. The method for preparing a heat-resistant nano-olefinic gas desorbent according to claim 1, characterized in that: It also includes step S6, surface hydrophobic modification, in which the reduced material is immersed in a toluene solution of perfluorodecyltriethoxysilane and refluxed at 80°C for 4 hours to make the water contact angle of the material surface ≥120°.

8. The method for preparing a heat-resistant nano-olefinic gas desorbent according to claim 7, characterized in that: In step S6, the concentration of perfluorodecyltriethoxysilane is 0.5-1.0 wt%, the mass ratio of toluene to material is 10:1, and after reflux, it is washed three times with anhydrous ethanol.

9. The method for preparing a heat-resistant nano-olefinic gas desorbent according to claim 1, characterized in that: The heat-resistant coating layer formed in step S3 has a thickness of 10-50 nm, which enables the material to maintain more than 90% of its specific surface area at 300℃.

10. The application of a heat-resistant nano-olefinic gas desorber prepared by any one of claims 1-9 in coal mine drainage.

Images