Methane adsorbent as well as preparation method and application thereof

Abstract

The invention relates to the technical field of catalyst preparation, and discloses a methane adsorbent as well as a preparation method and application thereof. The method comprises the following steps: (1) mixing organic nickel with activated carbon, and then drying and roasting the obtained mixture to obtain nickel-loaded activated carbon; (2) mixing the SAPO-34 molecular sieve with alkali liquor and reacting to obtain a slurry seed crystal; and (3) mixing the nickel-loaded activated carbon, the SAPO-34 molecular sieve, white carbon black, sodium aluminate and sodium phosphate, crystallizing, and sequentially washing, drying, roasting and forming the obtained crystallized solid product. The methane adsorbent prepared by the method has the characteristics of high adsorption selectivity, adsorption capacity and methane removal efficiency, easiness in regeneration, long overall service life and the like, and the method is simple in process and suitable for large-scale industrial production, and has a wide application prospect in the field of adsorbing and separating methane from ultralow-temperature liquid inert gas or permanent gas.

Description

Technical Field

[0001] This invention relates to the field of catalyst preparation technology, specifically to a methane adsorbent, its preparation method, and its application. Background Technology

[0002] Krypton and xenon are widely used in the electronics, electric light source, medical, nuclear, high-energy physics, and aerospace industries due to their high density, low thermal conductivity, and high transmittance. In 2019, global demand for krypton was approximately 140 million liters, and for xenon, approximately 17 million liters. Therefore, krypton and xenon are considered extremely scarce strategic resources. Because krypton and xenon are present in very small amounts in the air (krypton at 1.14 ppm and xenon at 0.086 ppm), they can only be extracted using large-scale air separation equipment, which requires advanced extraction technology and is difficult to produce. However, based on current technological developments, extraction from liquid oxygen and liquid air are the most feasible solutions.

[0003] When extracting krypton and xenon from liquid oxygen or liquid air, removing trace amounts of high-boiling-point components such as methane dissolved in the liquid oxygen or liquid air is crucial to ensuring process safety. Current methods involve purifying the liquid oxygen or liquid air to convert the contained methane into carbon dioxide and water, and then re-liquefying the oxygen or air after removing the carbon dioxide and water. However, this method is energy-intensive, complex, and heavily reliant on compressors, hindering its widespread application. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of complex processes, high energy consumption, and limited application in existing processes for removing trace amounts of methane dissolved in liquid oxygen or liquid air. This invention provides a methane adsorbent, its preparation method, and its applications. The methane adsorbent prepared by this method exhibits high adsorption selectivity and capacity, high methane removal efficiency, easy regeneration, and long overall service life. Furthermore, the method is simple, suitable for large-scale industrial production, and has broad application prospects in the adsorption and separation of methane from cryogenic liquid inert gases or permanent gases.

[0005] To achieve the above objectives, the present invention provides a method for preparing a methane adsorbent, the method comprising the following steps: (1) Mix organic nickel with activated carbon, then dry and calcine the resulting mixture to obtain nickel-loaded activated carbon; (2) The SAPO-34 molecular sieve was mixed with an alkaline solution and reacted to obtain a slurry seed crystal; (3) The nickel-loaded activated carbon, the slurry seed crystal, white carbon black, sodium aluminate and sodium phosphate are mixed and crystallized, and then the resulting crystallized solid product is washed, dried, calcined and shaped in sequence.

[0006] Preferably, in step (1), the weight ratio of the organic nickel to the activated carbon is 1:5-25.

[0007] Preferably, the specific surface area of ​​the activated carbon is ≥700 m². 2 / g, pore size ≤10nm.

[0008] Preferably, in step (1), the organonickel is added in the form of an organonickel solution, and the content of the organonickel in the organonickel solution is 5-20 wt%.

[0009] Preferably, the organonitrile is nickel formate and / or nickel acetylacetonate.

[0010] Preferably, in step (1), the drying conditions include: a temperature of 80-220°C and a time of 2-15 hours.

[0011] Preferably, the calcination conditions include: a temperature of 300-500℃, a time of 3-10h, and a heating rate not exceeding 2℃ / min.

[0012] Preferably, in step (2), the solid-liquid ratio of the SAPO-34 molecular sieve to the alkaline solution is 1g:3-30mL.

[0013] Preferably, the specific surface area of ​​the SAPO-34 molecular sieve is ≥200 m². 2 / g.

[0014] Preferably, the alkaline solution is a sodium hydroxide solution, and the concentration of the sodium hydroxide solution is 2-10 mol / L.

[0015] Preferably, in step (2), the reaction conditions include: a temperature of 50-80°C and a time of 0.5-4h.

[0016] Preferably, the weight ratio of the nickel-loaded activated carbon, the SAPO-34 molecular sieve, silica, sodium aluminate, and sodium phosphate is 1:(0.01-0.1):(1-10):(0.1-0.5):(0.1-0.5).

[0017] Preferably, the specific surface area of ​​the silica is ≥300m². 2 / g.

[0018] Preferably, in step (3), the crystallization conditions include: a temperature of 80-220°C and a time of 4-20h.

[0019] Preferably, the drying conditions include a temperature of 80-130°C and a time of 2-15 hours.

[0020] Preferably, the calcination conditions include: a temperature of 300-500℃, a time of 3-10h, and a heating rate not exceeding 2℃ / min.

[0021] A second aspect of the present invention provides a methane adsorbent prepared by the above method.

[0022] The third aspect of this invention provides the application of the above-mentioned methane adsorbent in the process of adsorbing and separating methane in cryogenic liquid inert gas or permanent gas.

[0023] Preferably, the methane adsorbent is reduced with hydrogen before use.

[0024] More preferably, the reduction conditions include: a temperature of 300-500℃ and a time of 1-12h.

[0025] More preferably, the gas hourly space velocity of hydrogen is 200-10000 h⁻¹. -1 .

[0026] Preferably, the gross hourly space velocity (GHSV) of the cryogenic liquid inert gas or the permanent gas is 0.01-6 h⁻¹. -1 .

[0027] The method described in this invention improves the methane adsorption capacity of nickel-loaded activated carbon by uniformly loading nickel active adsorption centers with extremely high methane adsorption activity onto activated carbon with a high specific surface area. By introducing a SAPO-34 molecular sieve secondary structure, silica, sodium aluminate, and sodium phosphate, a dense molecular sieve membrane is coated onto the surface of the nickel-loaded activated carbon. This membrane's unique cage-like structure preferentially captures methane molecules and allows them to enter the nickel active adsorption centers of the nickel-loaded activated carbon. Simultaneously, it further restricts the diffusion of methane molecules outside the nickel-loaded activated carbon, creating a region with a higher methane concentration. This facilitates efficient adsorption, resulting in a methane adsorbent with high adsorption selectivity, high adsorption capacity, high methane removal efficiency, easy regeneration, and long overall service life. Furthermore, the method is simple, suitable for large-scale industrial production, and has broad application prospects in the adsorption and separation of methane from cryogenic liquid inert gases or permanent gases. Attached Figure Description

[0028] Figure 1 This is a photograph of the methane adsorbent S1 prepared in Example 1; Figure 2 This is the XRD pattern of methane adsorbent S1 prepared in Example 1. Detailed Implementation

[0029] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0030] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0031] The method for preparing the methane adsorbent described herein includes the following steps: (1) Mix organic nickel with activated carbon, then dry and calcine the resulting mixture to obtain nickel-loaded activated carbon; (2) The SAPO-34 molecular sieve was mixed with an alkaline solution and reacted to obtain a slurry seed crystal; (3) The nickel-loaded activated carbon, the slurry seed crystal, white carbon black, sodium aluminate and sodium phosphate are mixed and crystallized, and then the resulting crystallized solid product is washed, dried, calcined and shaped in sequence.

[0032] In the method described in this invention, the organonickel has nickel active centers, and when mixed with activated carbon, it ensures that the nickel active adsorption centers are highly dispersed on the activated carbon, further effectively improving the adsorption capacity of the methane adsorbent. Preferably, the organonickel is nickel formate and / or nickel acetylacetonate. More preferably, the organonickel is nickel formate.

[0033] In the method described in this invention, in step (1), the organonickel is added in the form of an organonickel solution, which is a mixture of the organonickel and a solvent. The content of the organonickel in the organonickel solution can be 5-20 wt%, preferably 7-19 wt%, and more preferably 9-17 wt%. Specifically, the content of the organonickel in the organonickel solution can be 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, or 17 wt%.

[0034] In the method described in this invention, the type of solvent is not limited; any solvent capable of dissolving the organonickel can be used. In some specific embodiments, when the organonickel is nickel formate, the solvent is water. In other specific embodiments, when the organonickel is nickel acetylacetonate, the solvent can be methanol or ethanol.

[0035] In the method described in this invention, to further improve the adsorption capacity and selectivity of the methane adsorbent, it is necessary to limit the specific surface area and pore size of the activated carbon. Specifically, the specific surface area of ​​the activated carbon is ≥700 m² / s. 2 / g, preferably 700-4000m 2 / g; the pore size of the activated carbon is ≤10nm, preferably 2-10nm. When the specific surface area and pore size of the activated carbon meet the above-defined ranges, the prepared methane adsorbent has high adsorption capacity and selectivity.

[0036] In the method described in this invention, the source of the activated carbon is not limited. Activated carbon from various sources commonly used in the art can be used. In specific embodiments, the activated carbon may be activated carbon purchased from Henan Songshan Technology Co., Ltd., activated carbon purchased from Chengde Sleip Activated Carbon Manufacturing Co., Ltd., or activated carbon purchased from Henan Weitai Environmental Protection Technology Co., Ltd.

[0037] In some embodiments, in step (1), to further improve the adsorption capacity of the methane adsorbent and achieve efficient adsorption of methane, the weight ratio of the organonickel to the activated carbon needs to be limited. Specifically, the weight ratio of the organonickel to the activated carbon is preferably 1:5-25, more preferably 1:6-20, and even more preferably 1:7-18. As a specific example, the weight ratio of the organonickel to the activated carbon can be 1:7, 1:8, 1:9, 1:10, 1:12, 1:14, 1:15, 1:16, or 1:18.

[0038] In some specific embodiments, the specific process of step (1) includes: mixing the organic nickel with the solvent to obtain an organic nickel solution, then adding the activated carbon to the organic nickel solution, then placing the resulting mixture in an oven for drying, and then placing it in a muffle furnace for calcination to obtain nickel-loaded activated carbon.

[0039] In some specific embodiments, in step (1), the drying conditions include: a temperature of 80-220℃, preferably 100-200℃; and a time of 2-15h, preferably 4-10h. Specifically, the drying temperature can be 100℃, 120℃, 140℃, 160℃, 180℃, or 200℃; and the drying time can be 4h, 6h, 8h, or 10h.

[0040] In some specific embodiments, in step (1), the calcination conditions include: a temperature of 300-500℃, preferably 320-480℃; a time of 3-10h, preferably 4-9h; and a heating rate not exceeding 2℃ / min. Specifically, the calcination temperature can be 320℃, 350℃, 380℃, 400℃, 420℃, 450℃, or 480℃; the calcination time can be 4h, 5h, 6h, 7h, 8h, or 9h; and the calcination heating rate can be 1℃ / min, 1.5℃ / min, or 2℃ / min. In this invention, the calcination time does not include the time required for the muffle furnace cavity temperature to rise from room temperature to the target calcination temperature.

[0041] In the method described in this invention, to further improve the adsorption capacity and selectivity of the methane adsorbent, it is necessary to limit the specific surface area of ​​the SAPO-34 molecular sieve. Specifically, the specific surface area of ​​the SAPO-34 molecular sieve is ≥200 m² / g. 2 / g.

[0042] In the method described in this invention, the SAPO-34 molecular sieve is reacted with the alkaline solution in order to utilize the dissolving and etching capabilities of the alkaline solution to break the SAPO-34 molecular sieve into nanoscale microparticles, while retaining the secondary structure of the SAPO-34 molecular sieve for use as seed crystals in the subsequent crystallization process.

[0043] In the method described in this invention, the type of alkaline solution is not limited; various alkaline solutions with dissolving and etching capabilities commonly used in the art can be used. In some specific embodiments, the alkaline solution is a sodium hydroxide solution, and the concentration of the sodium hydroxide solution can be 2-10 mol / L, preferably 3-9 mol / L, and more preferably 4-8 mol / L. Specifically, the concentration of the sodium hydroxide solution can be 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, or 8 mol / L.

[0044] In some embodiments, to ensure that the SAPO-34 molecular sieve is broken down into nanoscale particles by the alkaline solution while retaining its secondary structure, thereby improving the adsorption capacity and selectivity of the methane adsorbent, the solid-liquid ratio of the SAPO-34 molecular sieve to the alkaline solution needs to be limited. Specifically, the solid-liquid ratio of the SAPO-34 molecular sieve to the alkaline solution is preferably 1g:3-30mL, more preferably 1g:3.5-25mL, and even more preferably 1g:4-20mL. As a specific example, the solid-liquid ratio of the SAPO-34 molecular sieve to the alkaline solution can be 1g:4mL, 1g:5mL, 1g:10mL, 1g:15mL, or 1g:20mL.

[0045] In some specific embodiments, the specific process of step (2) includes: mixing the SAPO-34 molecular sieve with the alkaline solution, and then reacting it in a water bath environment under ultrasonic vibration conditions.

[0046] In some specific embodiments, in step (2), the reaction conditions include: a temperature of 50-80℃, preferably 60-75℃; and a time of 0.5-4h, preferably 1-3h. Specifically, the reaction temperature can be 60℃, 65℃, 70℃, or 75℃; and the reaction time can be 1h, 1.5h, 2h, 2.5h, or 3h.

[0047] In some embodiments, in order to coat the surface of the nickel-loaded activated carbon with a dense molecular sieve membrane, thereby further improving the adsorption capacity and selectivity of the methane adsorbent, it is necessary to limit the weight ratio of the nickel-loaded activated carbon, the SAPO-34 molecular sieve, silica, sodium aluminate, and sodium phosphate. Specifically, the weight ratio of the nickel-loaded activated carbon, the SAPO-34 molecular sieve, silica, sodium aluminate, and sodium phosphate is preferably 1:(0.01-0.1):(1-10):(0.1-0.5):(0.1-0.5), more preferably 1:(0.015-0.098):(2-9):(0.15-0.45):(0.15-0.45), and even more preferably 1:(0.019-0.095):(3-8):(0.19-0.4):(0.19-0.4).

[0048] In the method described in this invention, the silica can be used as a silicon source to crystallize with the slurry seed crystals, sodium aluminate, and sodium phosphate on the surface of nickel-loaded activated carbon, forming a dense molecular sieve membrane. In this invention, to further improve the adsorption capacity and selectivity of the methane absorbent, the specific surface area of ​​the silica needs to be limited. Specifically, the specific surface area of ​​the silica is ≥300 m² / g. 2 / g.

[0049] In the method described in this invention, the source of the silica is not limited, and silica from various sources commonly used in the art can be used. In specific embodiments, the silica may be M5 silica purchased from Cabot Corporation of the United States, 923 silica purchased from Guangzhou Liben Rubber Raw Material Trading Co., Ltd., or A200 silica purchased from Huainan Shengjie Anchoring Materials Co., Ltd.

[0050] In some specific embodiments, the specific process of step (3) includes: mixing the nickel-loaded activated carbon, the slurry seed crystal, white carbon black, sodium aluminate and sodium phosphate and crystallizing them, then washing the obtained crystallized solid product, drying the washed solid product in an oven, then placing the dried solid product in a muffle furnace for calcination, and finally shaping the calcined product.

[0051] In some specific embodiments, in step (3), the crystallization conditions include: a temperature of 80-220℃, preferably 100-200℃; and a time of 4-20h, preferably 5-15h. Specifically, the crystallization temperature can be 100℃, 120℃, 150℃, 160℃, 180℃, or 200℃; and the crystallization time can be 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, or 15h.

[0052] In some specific embodiments, in step (3), the drying conditions include: a temperature of 80-130℃, preferably 90-120℃; and a time of 2-15h, preferably 6-10h. Specifically, the drying temperature can be 90℃, 100℃, 110℃ or 120℃; and the drying time can be 6h, 7h, 8h, 9h or 10h.

[0053] In some specific embodiments, in step (3), the calcination conditions include: a temperature of 300-500℃, preferably 320-480℃; a time of 3-10h, preferably 4-9h; and a heating rate not exceeding 2℃ / min. Specifically, the calcination temperature can be 320℃, 350℃, 380℃, 400℃, 420℃, 450℃, or 480℃; the calcination time can be 4h, 5h, 6h, 7h, 8h, or 9h; and the calcination heating rate can be 1℃ / min, 1.5℃ / min, or 2℃ / min. In this invention, the calcination time does not include the time required for the muffle furnace cavity temperature to rise from room temperature to the target calcination temperature.

[0054] In the method described in this invention, no limitation is made to the forming method of the calcined product; various forming methods commonly used in the art can be used. In some specific embodiments, the forming method is a tableting method. In other specific embodiments, the forming method is a strip extrusion method.

[0055] This invention also provides a methane adsorbent prepared by the above method. The methane adsorbent comprises nickel-loaded activated carbon containing nickel active adsorption centers and a molecular sieve membrane coated on the surface of the nickel-loaded activated carbon. The nickel-loaded activated carbon provides a high methane adsorption capacity, and the nickel active adsorption centers have extremely high methane adsorption activity. Furthermore, due to the difference in kinetic diameter between methane molecules and inert or permanent gas molecules, the molecular sieve membrane exhibits good selectivity. Its unique cage-like structure preferentially captures methane molecules and allows them to enter the nickel active adsorption centers of the nickel-loaded activated carbon. Simultaneously, it further restricts the diffusion of methane molecules outside the nickel-loaded activated carbon, forming a region with a higher methane concentration. This facilitates efficient adsorption, resulting in a methane adsorbent with high adsorption selectivity, high adsorption capacity, high methane removal efficiency, easy regeneration, and a long overall service life.

[0056] The present invention further provides the application of the above-mentioned methane adsorbent in the process of adsorbing and separating methane in cryogenic liquid inert gas or permanent gas.

[0057] In some embodiments, in order to ensure the adsorption activity, selectivity and stability of the methane flushing adsorbent during the adsorption and separation of methane in cryogenic liquid inert gas or permanent gas, the methane adsorbent needs to be reduced with hydrogen before use.

[0058] In some specific embodiments, to ensure the adsorption activity, selectivity, and stability of the methane adsorbent during the adsorption and separation of methane in a cryogenic liquid inert gas or permanent gas, it is necessary to limit the gas hourly space velocity (GHSV) of the hydrogen. Specifically, the GHSV of the hydrogen is preferably 200-10000 h⁻¹. -1 More preferably 300-9000h -1 Further preferred is 1000-5000h -1 As a specific example, the 1000h of hydrogen gas -1 2000h -1 3000h -1 4000h -1 or 5000h -1 .

[0059] In some specific embodiments, the reduction conditions include: a temperature of 300-500℃, preferably 320-480℃; and a time of 1-12h, preferably 2-10h.

[0060] In some specific embodiments, to ensure the adsorption activity, selectivity, and stability of the methane adsorbent during the adsorption and separation of methane by a cryogenic liquid inert gas or a permanent gas, it is necessary to limit the total weight hourly space velocity (WHSV) of the cryogenic liquid inert gas or the permanent gas. Specifically, the WHSV of the cryogenic liquid inert gas or the permanent gas is preferably 0.01-6 h⁻¹. -1 More preferably 0.1-5h -1 More preferably 0.5-3h -1 .

[0061] The following examples further illustrate the methane adsorbent, its preparation method, and its application according to the present invention. These examples are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following examples.

[0062] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available.

[0063] Example 1 This embodiment provides a methane adsorbent and its preparation method, the preparation method of which includes the following steps: (1) Dissolve 39.8 g of nickel formate in 300 g of water to form a clear nickel formate solution. Add 500 g of activated carbon (purchased from Henan Songshan Technology Co., Ltd., with a specific surface area of ​​882 m²) 2 / g (pore size 2-8nm) is added to the nickel formate solution until the nickel formate solution is completely absorbed by the activated carbon; (2) The activated carbon that absorbed the nickel formate solution was placed in an oven and dried at 100°C for 6 hours. Then it was placed in a muffle furnace and heated to 400°C at a heating rate of 1°C / min for 4 hours. After cooling, 520 g of nickel-loaded activated carbon was obtained. (3) Take 10 g of SAPO-34 molecular sieve (specific surface area of ​​359 m²) 2 / g) was added to 200mL of 4 mol / L sodium hydroxide solution and placed in a water bath at 60℃. The mixture was then ultrasonically vibrated for 1h to obtain slurry-like seed crystals. (4) The nickel-loaded activated carbon prepared in step (2) and the slurry seed crystals prepared in step (3) are mixed with 2000 g of silica (Cabot M5 silica, with a specific surface area of ​​758 m²). 2 Mix 100 g of sodium aluminate and 100 g of sodium phosphate, and grind them to form a homogeneous mixture; (5) The mixture obtained in step (4) is transferred into a crystallization kettle and crystallized at 150°C for 10 hours. Then the solid obtained is taken out and washed. The washed solid product is dried at 100°C for 10 hours. The dried solid product is placed in a muffle furnace and heated to 400°C at a heating rate of 1°C / min for 6 hours. Finally, the calcined product is placed on an extruder to form a methane adsorbent S1. Figure 1 A physical image of the methane adsorbent S1 is shown; This embodiment also uses methane adsorbent S1 to adsorb and separate methane contained in cryogenic liquid oxygen. The specific process includes: Methane adsorbent S1 was crushed into particles with a diameter of 15 mesh. 2g of the crushed methane adsorbent S1 was then packed into a reaction tube with an inner diameter of 1.4cm, an outer diameter of 1.7cm, and a total length of 72cm. A gas hourly space velocity (GHSV) of 2000 h⁻¹ was then used. -1 Hydrogen gas was used to reduce the methane adsorbent S1 at 350°C for 4 hours, and then the methane adsorbent was introduced into the atmosphere at atmospheric pressure at a temperature of -196°C (cooled by liquid nitrogen) with a total weight hourly space velocity of 0.5 h⁻¹. -1 The cryogenic liquid oxygen (containing 600 ppm methane, the same below) was reacted for 80 h, and the methane concentration at the outlet of the reaction tube was measured. The results are shown in Table 1. In this invention, the pressure is absolute pressure.

[0064] Example 2 This embodiment provides a methane adsorbent and its preparation method, the preparation method of which includes the following steps: (1) Dissolve 29.8 g of nickel formate in 300 g of water to form a clear nickel formate solution. Add 500 g of activated carbon (purchased from Chengde Sleip Activated Carbon Manufacturing Co., Ltd., with a specific surface area of ​​972 m²) 2 / g (pore size 2-10nm) is added to the nickel formate solution until the nickel formate solution is completely absorbed by the activated carbon; (2) The activated carbon that absorbed the nickel formate solution was placed in an oven and dried at 120°C for 8 hours. Then it was placed in a muffle furnace and heated to 400°C at a heating rate of 1°C / min for 6 hours. After cooling, 515 g of nickel-loaded activated carbon was obtained. (3) Take 25g of SAPO-34 molecular sieve (specific surface area of ​​335m²) 2 / g) was added to 375mL of 5mol / L sodium hydroxide solution and placed in a water bath at 60℃. The mixture was then sonicated for 2h to obtain slurry-like seed crystals. (4) The nickel-loaded activated carbon prepared in step (2) and the slurry seed crystals prepared in step (3) are mixed with 3000 g of silica (purchased from Guangzhou Liben Rubber Raw Material Trading Co., Ltd., model 923, specific surface area 594 m²). 2Mix 150 g of sodium aluminate and 150 g of sodium phosphate, and grind them to form a homogeneous mixture; (5) The mixture obtained in step (4) is transferred into a crystallization kettle and crystallized at 180°C for 6 hours. Then the solid obtained is taken out and washed. The washed solid product is dried at 120°C for 8 hours. The dried solid product is placed in a muffle furnace and heated to 400°C at a heating rate of 1°C / min for 8 hours. Finally, the calcined product is placed on an extruder to form a methane adsorbent S2. This embodiment also uses methane adsorbent S2 to adsorb and separate methane contained in cryogenic liquid oxygen. The specific process includes: Methane adsorbent S2 was crushed into particles with a diameter of 15 mesh. 2g of the crushed methane adsorbent S2 was packed into a reaction tube with an inner diameter of 1.4cm, an outer diameter of 1.7cm, and a total length of 72cm. Then, a gas hourly space velocity (HSV) of 2000 h⁻¹ was used. -1 Hydrogen gas was used to reduce the methane adsorbent S2 at 350°C for 4 hours, and then the methane adsorbent was introduced into the atmosphere at atmospheric pressure (-196°C, kept cool with liquid nitrogen) at a total weight hourly space velocity (WHSV) of 0.5 h⁻¹. -1 The cryogenic liquid oxygen (containing 600 ppm methane, the same below) was reacted for 80 h, and the methane concentration at the outlet of the reaction tube was measured. The results are shown in Table 1.

[0065] Example 3 This embodiment provides a methane adsorbent and its preparation method, the preparation method of which includes the following steps: (1) Dissolve 59.7 g of nickel formate in 300 g of water to form a clear nickel formate solution. Add 500 g of activated carbon (purchased from Henan Weitai Environmental Protection Technology Co., Ltd., with a specific surface area of ​​1190 m²) 2 / g (pore size 2-9nm) is added to the nickel formate solution until the nickel formate solution is completely absorbed by the activated carbon; (2) The activated carbon that absorbed the nickel formate solution was placed in an oven and dried at 150°C for 4 hours. Then it was placed in a muffle furnace and heated to 450°C at a heating rate of 1°C / min for 8 hours. After cooling, 530 g of nickel-loaded activated carbon was obtained. (3) Take 50g of SAPO-34 molecular sieve (specific surface area of ​​424m²) 2 / g) was added to 200mL of 6mol / L sodium hydroxide solution and placed in a water bath at 65℃. The mixture was then ultrasonically vibrated for 2h to obtain slurry-like seed crystals. (4) The nickel-loaded activated carbon prepared in step (2) and the slurry seed crystals prepared in step (3) are mixed with 4000 g of silica (purchased from Huainan Shengjie Anchoring Materials Co., Ltd., model A200, specific surface area 981 m²). 2Mix 200 g of sodium aluminate and 200 g of sodium phosphate, and grind them to form a homogeneous mixture; (5) The mixture obtained in step (4) is transferred into a crystallization kettle and crystallized at 150°C for 6 hours. Then the solid obtained is taken out and washed. The washed solid product is dried at 120°C for 6 hours. The dried solid product is placed in a muffle furnace and heated to 400°C at a heating rate of 1°C / min for 4 hours. Finally, the calcined product is placed on an extruder to form a methane adsorbent S3. This embodiment also uses methane adsorbent S3 to adsorb and separate methane contained in cryogenic liquid oxygen. The specific process includes: Methane adsorbent S3 was crushed into particles with a diameter of 15 mesh. 2g of the crushed methane adsorbent S3 was then packed into a reaction tube with an inner diameter of 1.4cm, an outer diameter of 1.7cm, and a total length of 72cm. A gas hourly space velocity (GHSV) of 2000 h⁻¹ was then used. -1 Hydrogen gas was used to reduce the methane adsorbent S3 at 350°C for 4 hours, and then the methane adsorbent was introduced into the atmosphere at atmospheric pressure at a temperature of -196°C (cooled by liquid nitrogen) with a total weight hourly space velocity of 0.5 h⁻¹. -1 The cryogenic liquid oxygen (containing 600 ppm methane, the same below) was reacted for 80 h, and the methane concentration at the outlet of the reaction tube was measured. The results are shown in Table 1.

[0066] Example 4 The preparation was carried out according to the method of Example 1, except that in step (1), the amount of nickel formate added was 17g, and methane adsorbent S4 was finally obtained. Methane adsorbent S4 was used to adsorb and separate methane contained in cryogenic liquid oxygen.

[0067] Example 5 The preparation was carried out according to the method of Example 1, except that in step (1), the amount of nickel formate added was 110g, and methane adsorbent S5 was finally obtained. Methane adsorbent S5 was used to adsorb and separate methane contained in cryogenic liquid oxygen.

[0068] Example 6 The preparation was carried out according to the method of Example 1, except that in step (3), the amount of SAPO-34 molecular sieve added was 5g, and methane adsorbent S6 was finally obtained. Methane adsorbent S6 was used to adsorb and separate methane contained in cryogenic liquid oxygen.

[0069] Example 7 The preparation was carried out according to the method of Example 1, except that in step (3), the amount of SAPO-34 molecular sieve added was 60g, and methane adsorbent S7 was finally obtained. Methane adsorbent S7 was used to adsorb and separate methane contained in cryogenic liquid oxygen.

[0070] Example 8 The preparation was carried out according to the method of Example 1, except that in step (5), the crystallization temperature was 60°C, and methane adsorbent S8 was finally obtained. Methane adsorbent S8 was used to adsorb and separate methane contained in cryogenic liquid oxygen.

[0071] Example 9 The preparation was carried out according to the method of Example 1, except that in step (5), the crystallization temperature was 250°C, and methane adsorbent S9 was finally obtained. Methane adsorbent S9 was used to adsorb and separate methane contained in cryogenic liquid oxygen.

[0072] Comparative Example 1 The preparation was carried out according to the method of Example 1, except that in step (1), nickel formate was not added, but 300 mL of water was used instead of nickel formate solution to finally obtain methane adsorbent D1, and methane adsorbent D1 was used to adsorb and separate methane contained in cryogenic liquid oxygen.

[0073] Comparative Example 2 The methane adsorbent D2 was prepared according to the method of Example 1, except that in step (3), 200 mL of water was used instead of 200 mL of 4 mol / L sodium hydroxide solution to finally obtain methane adsorbent D2, and methane adsorbent D2 was used to adsorb and separate methane contained in cryogenic liquid oxygen.

[0074] Comparative Example 3 The preparation was carried out according to the method of Example 1. The difference is that in step (5), the mixture was not crystallized, but was directly dried, calcined and shaped to finally obtain methane adsorbent D3. Methane adsorbent D3 was used to adsorb and separate methane contained in cryogenic liquid oxygen.

[0075] Comparative Example 4 The preparation was carried out according to the method of Example 1, except that in step (3), the SAPO-34 molecular sieve was replaced with an equal mass of Y-type molecular sieve, and methane adsorbent D4 was finally prepared. Methane adsorbent D4 was then used to adsorb and separate methane contained in cryogenic liquid oxygen.

[0076] Test case (1) The present invention uses an X-ray diffractometer (Bruker D8 advance) to characterize the methane adsorbent S1 prepared in Example 1. Figure 2 The XPD spectrum of the methane adsorbent S1 prepared in Example 1 is shown. The results show that the sample can exhibit relatively regular SAPO-34 diffraction peaks, indicating that the adsorbent is coated with SAPO-34 molecular sieve membrane and has a relatively uniform texture.

[0077] (2) The present invention uses the formula: methane removal efficiency = (600 - average methane content at the outlet of the reaction tube) / 600 × 100% to calculate the methane removal efficiency of the methane composite material prepared in the examples and comparative examples for methane contained in cryogenic liquid oxygen. The results are shown in Table 1.

[0078] Table 1

[0079] As can be seen from the results in Table 1, the methane adsorbent prepared by the method described in this invention has the characteristics of high adsorption selectivity and adsorption capacity, high methane removal efficiency, easy regeneration, and long overall service life. Moreover, the method is simple and suitable for large-scale industrial production, and has broad application prospects in the field of methane adsorption and separation in ultra-low temperature liquid inert gas or permanent gas.

[0080] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a methane adsorbent, characterized in that, The method includes the following steps: (1) Mix organic nickel with activated carbon, then dry and calcine the resulting mixture to obtain nickel-loaded activated carbon; (2) The SAPO-34 molecular sieve was mixed with an alkaline solution and reacted to obtain a slurry seed crystal; (3) The nickel-loaded activated carbon, the slurry seed crystal, white carbon black, sodium aluminate and sodium phosphate are mixed and crystallized, and then the resulting crystallized solid product is washed, dried, calcined and shaped in sequence.

2. The method according to claim 1, characterized in that, In step (1), the weight ratio of the organonickel to the activated carbon is 1:5-25; and / or The specific surface area of ​​the activated carbon is ≥700m². 2 / g, pore size ≤10nm.

3. The method according to claim 1 or 2, characterized in that, In step (1), the organonickel is added in the form of an organonickel solution, and the content of the organonickel in the organonickel solution is 5-20 wt%; and / or The organonickel is nickel formate and / or nickel acetylacetonate.

4. The method according to any one of claims 1-3, characterized in that, In step (1), the drying conditions include: a temperature of 80-220°C and a time of 2-15 hours; and / or The calcination conditions include: a temperature of 300-500℃, a time of 3-10h, and a heating rate not exceeding 2℃ / min.

5. The method according to claim 1, characterized in that, In step (2), the solid-liquid ratio of the SAPO-34 molecular sieve to the alkaline solution is 1 g: 3-30 mL; and / or The specific surface area of ​​the SAPO-34 molecular sieve is ≥200m². 2 / g; and / or The alkaline solution is a sodium hydroxide solution, and the concentration of the sodium hydroxide solution is 2-10 mol / L.

6. The method according to claim 1 or 5, characterized in that, In step (2), the reaction conditions include a temperature of 50-80°C and a time of 0.5-4h.

7. The method according to claim 1, characterized in that, The weight ratio of the nickel-loaded activated carbon, the SAPO-34 molecular sieve, silica, sodium aluminate, and sodium phosphate is 1:(0.01-0.1):(1-10):(0.1-0.5):(0.1-0.5); and / or The specific surface area of ​​the silica is ≥300m². 2 / g.

8. The method according to claim 1 or 7, characterized in that, In step (3), the crystallization conditions include: a temperature of 80-220°C and a time of 4-20 hours; and / or The drying conditions include: a temperature of 80-130℃ and a time of 2-15 hours; and / or The calcination conditions include: a temperature of 300-500℃, a time of 3-10h, and a heating rate not exceeding 2℃ / min.

9. A methane adsorbent prepared by the method according to any one of claims 1-8.

10. The application of the methane adsorbent according to claim 9 in the process of adsorbing and separating methane in cryogenic liquid inert gas or permanent gas; Preferably, the methane adsorbent is reduced with hydrogen before use; More preferably, the conditions for the reduction include: The temperature is 300-500℃, and the time is 1-12 hours; More preferably, the gas hourly space velocity of hydrogen is 200-10000 h⁻¹. -1 ; Preferably, the gross hourly space velocity (GHSV) of the cryogenic liquid inert gas or the permanent gas is 0.01-6 h⁻¹. -1 .

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