A Ni(ina)2 particulate material for methane adsorption and separation and its molding and granulation method

Abstract

This invention discloses a Ni(ina)₂ particulate material for methane adsorption and separation, and its molding and granulation method, belonging to the field of adsorption material preparation technology. The method involves bonding Ni(ina)₂ with a binder, polyvinylpyrrolidone (PVP), followed by drying to prepare MOF particles with controllable size. Simultaneously, doping the MOFs with a small amount of composite reinforcing agents (graphite and PVP) significantly improves the compressive strength of the material, meeting the strength requirements of industrial adsorption tower packing. The reinforced PVP molding method of this invention has simple operating steps, good guiding significance in practical industrial applications, and significant industrial value. It is applicable not only to Ni(ina)₂ but also to the molding and granulation of other organometallic materials.

Description

Technical Field

[0001] This invention belongs to the field of adsorption material preparation technology, specifically relating to a Ni(ina)2 particulate material for methane adsorption and separation and its molding and granulation method. Background Technology

[0002] Natural gas, as a low-carbon, efficient, and clean energy source and chemical feedstock, is widely developed and utilized worldwide. However, with the continuous and increasing use of unsustainable fossil fuels, the supply and demand imbalance of natural gas has become increasingly prominent, leading to energy crises and environmental pollution. Therefore, separating and purifying methane from oilfield gas, biogas, coalbed methane, landfill gas, and other low-quality methane gases is an effective way to address the insufficient natural gas supply. Coalbed methane is a major source of unconventional natural gas and an excellent supplement to conventional natural gas. Compared to cryogenic separation, membrane separation, and absorption separation, adsorption separation has advantages such as economy, flexibility, cleanliness, and adaptability in concentrating and purifying low-concentration methane (30%) coalbed methane. The key to the separation and purification of low-quality methane gas lies in the CH4 / N2 adsorbent. Currently, activated carbon adsorbents are most widely used in the adsorption separation of low-quality methane due to their wide availability of raw materials, large specific surface area, low price, and good stability. However, they also have disadvantages such as large circulating gas volume and low efficiency, limiting their application to the purification of trace impurities in natural gas.

[0003] Metal-organic frameworks (MOFs) possess advantages such as high specific surface area, tunable pore size and open surface functional groups. Rationally designed MOFs can further improve the efficiency of CH4 / N2 adsorption and separation. Ni(ina)2, with its optimized pore structure, can adsorb 40 ml / g of CH4 at room temperature and pressure, making it one of the MOFs with the highest adsorption capacity for methane. Generally, MOFs are crystalline particles with a diameter of less than 0.5 mm. In practical applications, the material needs to be molded into particles with a diameter of approximately 5 mm. This is because in the treatment of high-throughput gases in actual industrial processes, adsorption towers filled with powdered adsorbents face significant pressure drops or even complete impediment of the gas to be treated, thus limiting the application of Ni(ina)2 in the adsorption, separation, and purification of low-quality methane.

[0004] It can be seen that a reasonable molding and granulation method can effectively reduce pressure drop, thereby increasing the adsorption rate of the gas to be treated. However, the adsorbent particles prepared by common binder granulation methods still suffer from high pore blockage and low pressure resistance. Some binders need to be applied in aqueous solutions, such as using sodium alginate and calcium chloride aqueous solutions to coat the material, because the presence of water will damage most water-sensitive MOF materials. In actual use, the adsorbent in the lower layer of the adsorption tower is squeezed and crushed back into powder as the filling height increases, which greatly limits the adsorption capacity of the adsorption tower. Therefore, it is essential to research and develop a new molding method with low pore blockage and high pressure resistance for Ni(ina)2 material to achieve high-throughput adsorption separation and purification of low-quality methane in industrial applications. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a Ni(ina)2 particulate material for methane adsorption and separation and its molding and granulation method, so as to solve the technical problem that the existing Ni(ina)2 material has a high pore blockage rate and low pressure resistance, which makes it impossible to achieve high-throughput adsorption.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] This invention discloses a method for molding and granulating Ni(ina)2 particulate materials for methane adsorption and separation, comprising: adding graphite and polyvinylpyrrolidone as composite reinforcing agents to Ni(ina)2 powder, mixing them evenly, adding polyvinyl butyral ethanol solution as a binder, mixing them evenly to obtain a mixed slurry; extruding and granulating the mixed slurry, and drying it to obtain Ni(ina)2 particulate materials for methane adsorption and separation.

[0008] Preferably, graphite is used as a reinforcing agent, and the amount of graphite added is 1%-4% of the mass of Ni(ina)2 powder. Polyvinylpyrrolidone is used as another reinforcing agent, and the amount of polyvinylpyrrolidone added is 1%-10% of the mass of Ni(ina)2 powder.

[0009] Preferably, the mass fraction of the polyvinyl butyral ethanol solution is 6% to 8%.

[0010] More preferably, the polyvinyl butyral ethanol solution is prepared by first adding 6-8g of polyvinyl butyral, and then gradually adding anhydrous ethanol dropwise to 100g to obtain a PVB ethanol solution with a mass fraction of 6%-8%.

[0011] More preferably, the mass ratio of polyvinyl butyral ethanol solution to Ni(ina)2 powder is (0.8-1):1.

[0012] Preferably, vacuum drying is used, and the vacuum drying temperature is 60-65℃.

[0013] Preferably, the Ni(ina)2 powder is prepared according to the following method:

[0014] Metal salts and organic ligands are dissolved in a solvent in a certain proportion and stirred at room temperature to form a mixture. Triethylamine is added to the mixture and stirring is continued until a homogeneous mixture is obtained.

[0015] The homogeneous mixture was solvothermal reacted at 150℃ for 60-72 h to obtain a crystalline precipitate. The crystalline precipitate was then filtered, washed, and vacuum activated to obtain Ni(ina)2 powder.

[0016] More preferably, the metal salt used is nickel acetate tetrahydrate, the ligand used is isonicotinic acid, and the molar ratio of nickel acetate tetrahydrate to isonicotinic acid is (1:2) to (1.2:2).

[0017] The activation treatment is a vacuum activation treatment at 160-165℃ for 12-24 hours.

[0018] The present invention also discloses a Ni(ina)2 particulate material for methane adsorption and separation prepared by the above-mentioned molding and granulation method, wherein the average particle size of the Ni(ina)2 particulate material is 4 to 6 mm.

[0019] Furthermore, the adsorption capacity of this Ni(ina)2 particle material for methane reaches 30 mL / g at room temperature and pressure.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] This invention discloses a method for molding and granulating Ni(ina)2 particles for methane adsorption and separation. The method involves bonding Ni(ina)2 with a binder, polyvinylpyrrolidone (PVP), followed by drying to prepare MOF particles with controllable size. Furthermore, doping the MOFs with a small amount of composite reinforcing agents (graphite and PVP) significantly improves the compressive strength of the material, meeting the strength requirements of industrial adsorption tower packing. This reinforced PVP molding method is simple to operate, has good guiding significance in practical industrial applications, and possesses significant industrial value. It is applicable not only to Ni(ina)2 but also to the molding and granulation of other organometallic materials.

[0022] The Ni(ina)2 particulate material prepared using this invention for methane adsorption and separation exhibits good methane adsorption and separation performance, achieving an adsorption capacity of 30 ml / g at room temperature and pressure. The resulting methane adsorbent demonstrates high selectivity, large adsorption capacity, high pressure resistance, and good cycle performance. Attached Figure Description

[0023] Figure 1 A photograph of Ni(ina)2 powder crystals in Example 1 of this invention;

[0024] Figure 2 The XRD diffraction pattern of Ni(ina)2 powder crystal in Example 1 of this invention;

[0025] Figure 3 This is a photograph of the Ni(ina)2@1-10 molded particles in Example 1 of the present invention;

[0026] Figure 4 The isotherms of Ni(ina)2 powder crystals and Ni(ina)2@1-10 molded particles for CH4 adsorption at room temperature are shown in Example 1 of this invention.

[0027] Figure 5 The adsorption isotherms of Ni(ina)2 powder crystals and Ni(ina)2@1-5 molded particles for CH4 and N2 at room temperature are shown in Example 2 of this invention.

[0028] Figure 6 The adsorption isotherms of Ni(ina)2 powder crystals and Ni(ina)2@1-1 molded particles at room temperature for CH4 and N2 in Example 3 of this invention are shown. Detailed Implementation

[0029] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0030] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0031] The present invention will now be described in further detail with reference to the accompanying drawings:

[0032] The raw materials and reagents used in this invention are: nickel acetate tetrahydrate (Ni(CH3COO)2·4H2O), isonicotinic acid (Hina), polyvinyl butyral (PVB), polyvinylpyrrolidone (PVP), N,N-dimethylformamide (DMF), anhydrous ethanol, and graphite powder. All reagents used are of analytical grade (AR) and no further purification was performed.

[0033] The nickel acetate and isonicotinic acid used in this invention form coordination bonds in DMF solution to synthesize MOF materials, which are raw materials for synthesizing Ni(ina)2 framework; the ethanol solution of PVB is a binder for powder materials. After drying, the ethanol evaporates, and the remaining PVB will bind the powder particles together; graphite and PVP are material reinforcing agents used to improve the compressive strength of PVB-bonded powder particles.

[0034] This invention synthesizes Ni(ina)2 particulate materials for methane separation and purification using a hydrothermal method in a polytetrafluoroethylene-lined reactor at high temperature. The adsorption capacity of methane and nitrogen in the prepared Ni(ina)2 particulate materials is determined using a BSD-PM2 microporous adsorption instrument.

[0035] A method for molding and granulating Ni(ina)2 particulate materials for methane adsorption and separation includes the following steps:

[0036] 1) Dissolve the metal salt and organic ligand in a solvent in a certain proportion and stir evenly at room temperature to form a mixture;

[0037] Preferably, the metal salt used in this invention is nickel acetate tetrahydrate, the ligand used is isonicotinic acid, and the solvent used is a mixture of N,N-dimethylformamide and acetonitrile, wherein the volume ratio of N,N-dimethylformamide to acetonitrile is 6:4.

[0038] Preferably, the stirring time at room temperature is 30 minutes;

[0039] 2) Add triethylamine to the mixture and continue stirring for 30 minutes to obtain a homogeneous mixture. Triethylamine acts as a reaction solution regulator, providing a weakly basic coordination environment for nickel acetate tetrahydrate and isonicotinic acid, which is more conducive to MOF crystallization. Only a trace amount of triethylamine is needed to achieve the desired effect. The specific dosage is approximately 0.03-0.032 mL of triethylamine per 100 mg of nickel acetate tetrahydrate.

[0040] 3) React the homogeneous mixture in a closed reactor for 60-72 hours to form a crystal precipitate. After cooling, filter and wash the crystal precipitate, and activate it under vacuum at 160℃ for 12-24 hours to obtain Ni(ina)2 powder.

[0041] 4) Add 1%-4% graphite and 1%-10% polyvinylpyrrolidone (based on the mass of unformed Ni(ina)2 powder) to Ni(ina)2 powder and mix thoroughly. Continue to add 6%-8% polyvinyl butyral ethanol solution (based on the mass of the dissolved solution) and mix thoroughly to obtain a paste mixture. Feed the paste mixture into an extruder and extrude it in stages. After vacuum drying at 160-165℃, Ni(ina)2 particulate material for methane adsorption and separation is formed.

[0042] The above method will be further described in detail below with reference to specific embodiments:

[0043] Example 1

[0044] Preparation of Ni(ina)₂ powder: 249 mg of nickel acetate tetrahydrate and 246 mg of isonicotinic acid were placed in a mixture of 6 mL of N,N-dimethylformamide and 4 mL of acetonitrile, and stirred at room temperature for 30 min. Then, 0.075 mL of triethylamine was added to the mixture, and stirring was continued for another 30 min. The homogeneous mixture was placed in a 20 mL reactor and heated at 150 °C for 72 h. After cooling to room temperature, the reaction product was filtered, washed, and dried in a vacuum oven at 160 °C for 12 h to obtain a dark green powder, which is Ni(ina)₂ powder crystal. (Image shown). Figure 1 As shown. See also Figure 2 The XRD diffraction results of Ni(ina)2 powder crystals show that the diffraction peaks and simulated peaks are identical, indicating that the material was successfully synthesized.

[0045] Preparation of Ni(ina)2@1-10 particulate material: Take 1.5g of Ni(ina)2 powder, mix it with 0.015g of graphite (1%) and 0.15g of polyvinylpyrrolidone (10%), grind it for 2-5 minutes, then add 1.2-1.5g of 8% (w / w) polyvinyl butyral ethanol solution and stir until a mixture is formed. Quickly transfer the mixture to a sealed extruder and extrude sample particles of suitable size as needed. Dry the particles in a vacuum oven at 60℃ for 12 hours to obtain the shaped Ni(ina)2@1-10 particulate material. (Image shown) Figure 3 As shown, the particle diameter is approximately 4 mm.

[0046] The compressive strength of the Ni(ina)2@1-10 granular material was tested using a tension-torsion tester, and the results showed that its compressive strength reached 25N.

[0047] Simultaneously, the adsorption capacities of methane and nitrogen at room temperature and pressure were tested on the Ni(ina)2 powder before molding and the prepared Ni(ina)2@1-10 granular material, respectively, to determine the CH4 / N2 adsorption and separation effect. The comparison results of the CH4 adsorption curves at room temperature and pressure are shown below. Figure 4 As shown in the figure, solid squares represent the adsorption curves of powdered Ni(ina)₂, and unfilled squares represent the desorption curves of powdered Ni(ina)₂; solid circles represent the adsorption curves of Ni(ina)₂@1-10 particles, and unfilled circles represent the desorption curves of Ni(ina)₂@1-10 particles. Although the maximum adsorption capacity of the shaped Ni(ina)₂@1-10 particle material decreased from 40 mL / g to 30 mL / g, and the pore blockage rate was approximately 30%, it is still a very good selective adsorbent for methane. In other words, due to the introduction of shaping and reinforcing agents without adsorption properties, a certain loss of adsorption performance is inevitable. However, the existing adsorption capacity can still be used for methane adsorption. The most critical improvement lies in the significant increase in its pressure resistance, which is equivalent to sacrificing a small portion of the adsorption performance to achieve material shaping and strength enhancement. This allows it to be effectively filled into the adsorption tower, thereby achieving high-throughput adsorption separation and purification in industry.

[0048] Comparative Example 1

[0049] Preparation of Ni(ina)₂: 249 mg of nickel acetate tetrahydrate and 246 mg of isonicotinic acid were placed in a mixture of 6 mL of N,N-dimethylformamide and 4 mL of acetonitrile, and stirred at room temperature for 30 min. Then, 0.075 mL of triethylamine was added to the mixture, and stirring was continued for another 30 min. The homogeneous mixture was placed in a 20 mL reactor and heated at 150 °C for 72 h. After cooling to room temperature, the reaction product was filtered, washed, and dried in a vacuum oven at 160 °C for 12 h to obtain a dark green powder, which is Ni(ina)₂ powder.

[0050] Preparation of Ni(ina)2 particles: Take 1.5g of Ni(ina)2 and add 1.2-1.5g of ethanol solution of polyvinyl butyral with a mass fraction of 8% and stir evenly to form a mixture. Quickly transfer the mixture to a sealed extruder and extrude sample particles of suitable size as needed. Dry the sample particles in a vacuum oven at 60℃ for 12h to obtain the shaped Ni(ina)2 particles.

[0051] As can be seen, unlike Example 1, this comparative example did not add binder or reinforcing agent to treat Ni(ina)2 powder, and finally prepared Ni(ina)2 particles. However, after pressure resistance test, its pressure resistance was only 12N, which is far less than the Ni(ina)2 particles formed in Example 1.

[0052] Example 2

[0053] Unlike Example 1, the amount of polyvinylpyrrolidone used is 5%.

[0054] Preparation of Ni(ina)₂: 249 mg of nickel acetate tetrahydrate and 246 mg of isonicotinic acid were placed in a mixture of 6 mL of N,N-dimethylformamide and 4 mL of acetonitrile, and stirred at room temperature for 30 min. Then, 0.075 mL of triethylamine was added to the mixture, and stirring was continued for another 30 min. The homogeneous mixture was placed in a 20 mL reactor and heated at 150 °C for 72 h. After cooling to room temperature, the reaction product was filtered, washed, and dried in a vacuum oven at 160 °C for 12 h to obtain a dark green powder, which is Ni(ina)₂.

[0055] Preparation of Ni(ina)2@1-5: Take 1.5g Ni(ina)2, mix it with 0.015g graphite (1%) and 0.075g polyvinylpyrrolidone (5%), grind it for 2-5 minutes, then add 1.2-1.5g of ethanol solution of 8% polyvinyl butyral and stir it evenly to form a mixture. Quickly transfer it to a closed extruder and extrude sample particles of suitable size as needed. Dry them in a vacuum oven at 60℃ for 12h to obtain the shaped Ni(ina)2@1-5 particles.

[0056] The adsorption and separation efficiency of CH4 / N2 can be determined by testing the adsorption of methane and nitrogen at room temperature and pressure on the Ni(ina)2 powder before molding and the obtained Ni(ina)2@1-5 particles, respectively. Figure 5 As shown, the adsorption capacity of Ni(ina)2@1-5 for methane at 298 K is much higher than that for nitrogen. (The solid squares represent the adsorption curves of powdered Ni(ina)2 for CH4 at 298 K, and the unfilled squares represent the desorption curves of powdered Ni(ina)2 for CH4 at 298 K; the solid circles represent the adsorption curves of Ni(ina)2@1-5 particles for N2 at 298 K, and the unfilled circles represent the desorption curves of Ni(ina)2@1-5 particles for N2 at 298 K.)

[0057] Example 3

[0058] Unlike Example 1, the amount of polyvinylpyrrolidone used is 1%.

[0059] Preparation of Ni(ina)₂: 249 mg of nickel acetate tetrahydrate and 246 mg of isonicotinic acid were placed in a mixture of 6 mL of N,N-dimethylformamide and 4 mL of acetonitrile, and stirred at room temperature for 30 min. Then, 0.075 mL of triethylamine was added to the mixture, and stirring was continued for another 30 min. The homogeneous mixture was placed in a 20 mL reactor and heated at 150 °C for 72 h. After cooling to room temperature, the reaction product was filtered, washed, and dried in a vacuum oven at 160 °C for 12 h to obtain a dark green powder, which is Ni(ina)₂.

[0060] Preparation of Ni(ina)2@1-1: Take 1.5g Ni(ina)2, mix it with 0.015g graphite (1%) and 0.015g polyvinylpyrrolidone (1%), grind it for 2-5 minutes, then add 1.2-1.5g of ethanol solution of 8% polyvinyl butyral and stir it evenly to form a mixture. Quickly transfer it to a closed extruder and extrude sample particles of suitable size as needed. Dry them in a vacuum oven at 60℃ for 12h to obtain the shaped Ni(ina)2@1-1 particles.

[0061] The adsorption and separation efficiency of CH4 / N2 can be determined by testing the adsorption of methane and nitrogen at room temperature and pressure on the unformed Ni(ina)2 powder and the obtained Ni(ina)2@1-1 particles. Figure 6 As shown, the adsorption capacity of Ni(ina)2@1-1 for methane at 298 K is much higher than that for nitrogen. (The solid squares represent the adsorption curves of powdered Ni(ina)2 for CH4 at 298 K, and the unfilled squares represent the desorption curves of powdered Ni(ina)2 for CH4 at 298 K; the solid circles represent the adsorption curves of Ni(ina)2@1-1 particles for N2 at 298 K, and the unfilled circles represent the desorption curves of Ni(ina)2@1-1 particles for N2 at 298 K.)

[0062] In summary, this invention addresses the current challenges in preparing and molding high-efficiency adsorbents for natural gas purification. Based on the requirements for methane adsorption and separation performance, it designs, prepares, and granulates a novel metal-organic framework material, Ni(ina)2, for methane purification. The Ni(ina)2 material preparation process is simple, with high yield, readily available and inexpensive raw materials, and good stability, exhibiting excellent performance in the CH4 / N2 separation process. The enhanced PVB molding and granulation method applicable to this material offers advantages such as low pore blockage rate, controllable particle size, high compressive strength, inexpensive materials, and simple process, showing broad prospects for industrial application. The method involves bonding Ni(ina)2 with an adhesive followed by drying to prepare MOF particles with controllable size. Adding a small amount of reinforcing agent to the MOFs significantly improves the material's compressive strength, meeting the strength requirements of industrial adsorption tower packing. This enhanced PVB molding method is not only applicable to Ni(ina)2 but also to the molding and granulation of other metal-organic materials.

[0063] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for molding and granulating Ni(ina)2 particulate materials for methane adsorption and separation, characterized in that, include: Graphite and polyvinylpyrrolidone were added to Ni(ina)2 powder as composite reinforcing agents. After mixing evenly, polyvinyl butyral ethanol solution was added as a binder and mixed evenly to obtain a slurry. The mixed slurry was extruded and granulated, and then dried to obtain Ni(ina)2 particulate material for methane adsorption and separation. The Ni(ina)2 powder is prepared according to the following method: Metal salts and organic ligands are dissolved in a solvent in a certain proportion and stirred at room temperature to form a mixture. Triethylamine is added to the mixture and stirring is continued until a homogeneous mixture is obtained. A homogeneous mixture was solvothermally reacted at 150℃ for 60–72 h to obtain a crystalline precipitate. The precipitate was then filtered, washed, and vacuum activated to obtain Ni(ina)₂ powder. The solvent used was N₂, N₂. A mixture of dimethylformamide and acetonitrile, N,N The volume ratio of dimethylformamide to acetonitrile is 6:4; the metal salt used is nickel acetate tetrahydrate, the ligand used is isonicotinic acid, and the molar ratio of nickel acetate tetrahydrate to isonicotinic acid is (1:2)~(1.2:2); the activation treatment is a vacuum activation treatment at 160~165℃ for 12~24 h.

2. The method for molding and granulating Ni(ina)2 particulate material for methane adsorption and separation according to claim 1, characterized in that, The amount of graphite added is 1%-4% of the mass of Ni(ina)2 powder.

3. The method for molding and granulating Ni(ina)2 particulate material for methane adsorption and separation according to claim 1, characterized in that, The amount of polyvinylpyrrolidone added is 1%-10% of the mass of Ni(ina)2 powder.

4. The method for molding and granulating Ni(ina)2 particulate material for methane adsorption and separation according to claim 1, characterized in that, The mass fraction of the polyvinyl butyral ethanol solution is 6%~8%.

5. The method for molding and granulating Ni(ina)2 particulate material for methane adsorption and separation according to claim 1, characterized in that, The mass ratio of polyvinyl butyral ethanol solution to Ni(ina)2 powder is (0.8~1):

1.

6. The method for molding and granulating Ni(ina)2 particulate material for methane adsorption and separation according to claim 1, characterized in that, Vacuum drying is used, and the vacuum drying temperature is 60-65℃.

7. A Ni(ina)2 particulate material for methane adsorption and separation prepared by the molding and granulation method according to any one of claims 1 to 6, characterized in that, The average particle size of this Ni(ina)2 material is 4~6 mm.

8. The Ni(ina)₂ particulate material for methane adsorption and separation according to claim 7, characterized in that, At room temperature and pressure, the adsorption capacity of this Ni(ina)2 particulate material for methane reaches 30 mL / g.

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