Gas-solid reaction device and preparation method of ZIF-8

Abstract

The invention discloses a gas-solid reaction device and a preparation method of ZIF-8. The gas-solid reaction device comprises a heating device, a solvent zone, a reaction zone, a pressure control device and a condensation zone; the solvent area is used for storing and heating a solvent to form a gas phase; the reaction zone is used for reacting a gas phase from the solvent zone with a solid phase in the reaction zone; the pressure control equipment is used for stabilizing reaction zone pressure. The preparation method comprises the following steps: heating a solvent in a solvent area to enter a second container in a gas phase form, reacting with zinc salt and dimethylimidazole powder which are uniformly mixed in the second container at a certain reaction temperature and pressure, and cooling, centrifuging, washing and drying a product to obtain white solid powder. The method disclosed by the invention is simple, low in energy consumption, green and environment-friendly, uniform in particle size, high in yield and easy for large-scale preparation.

Description

Technical Field

[0001] The invention belongs to the field of nano materials, and specifically relates to a gas-solid reaction device and a method for preparing ZIF-8. Background Art

[0002] Metal-organic frameworks (MOFs) are organic-inorganic hybrid porous crystalline materials composed of metal ion centers and organic ligands. MOFs have the advantages of large specific surface area, high porosity, diverse and adjustable structures, and are widely used in gas separation, optoelectronics, sensing, catalysis, energy storage and other fields.

[0003] Zeolite imidazole framework (ZIF-8) material is a typical MOF with high specific surface area, excellent thermal stability and chemical stability, and flexible and adjustable structure. ZIF-8 is self-assembled by zinc ions and imidazole ligands, and is generally prepared by hydrothermal synthesis or solvothermal synthesis. However, the disadvantages of hydrothermal synthesis and solvothermal synthesis are large solvent consumption, large amount of waste liquid, high energy consumption caused by separation, and low environmental friendliness. Therefore, it is very necessary to develop a synthetic route with simple preparation method, low energy consumption, and green environmental protection.

[0004] CN106905536B discloses a method for rapidly synthesizing a multi-level porous ZIF-8 material, using a surfactant diethanolamine as a structure directing agent, and the synthesis method comprises the following steps: dissolving zinc nitrate and 2-methylimidazole in methanol respectively, mixing the two solutions after stirring, and continuing to stir; adding a template agent diethanolamine to the mixed solution, stirring; filtering the obtained product, putting it into a vacuum drying oven for drying, and obtaining a multi-level porous ZIF-8 material. The present invention shortens the synthesis time and improves the yield by adding diethanolamine as a template agent.

[0005] CN114133584A discloses a green, efficient and uniform method for synthesizing ZIF-8 material. The method uses zinc salt, resorcinol and 2-methylimidazole as raw materials and water as solvent for preparation: zinc salt and resorcinol are added into water and stirred to dissolve to obtain solution A; 2-methylimidazole is added into water and stirred to dissolve to obtain solution B; solution A is mixed with solution B and stirred vigorously to obtain solution C; solution C is allowed to stand to obtain a white emulsion, the white emulsion is centrifuged, and the separated solid matter is first washed and then dried to obtain a white powdery ZIF-8 material.

[0006] CN116041717A discloses a green and economical method for synthesizing ZIF-8 materials on a large scale. The method is prepared with industrial-grade zinc acetate dihydrate and 2-methylimidazole as raw materials and tap water as solvent; the method comprises the following steps: adding 2-methylimidazole and triethylamine to tap water, stirring to fully dissolve them, and obtaining solution A; adding zinc acetate dihydrate to tap water, stirring to fully dissolve them, and obtaining solution B; adding solution B to solution A, stirring to fully dissolve them, and obtaining solution C; detecting the pH value of solution C, and stopping stirring after the pH value is stable; allowing solution C to stand at room temperature to obtain a sedimentation layer, and obtaining the target product by centrifugal separation and washing operations, and drying the obtained target product to obtain a white powdery ZIF-8 material.

[0007] The methods described in these inventions all introduce a third component, which needs to be removed in subsequent steps. Stirring is required in all synthesis steps, which consumes high energy. In addition, a certain amount of organic solvent or water is consumed in the preparation process, and a large amount of solvent is consumed and a large amount of waste liquid is generated. It is urgent to develop a synthesis route with a simple preparation method, low energy consumption, and green environmental protection. Summary of the invention

[0008] In view of the shortcomings of the prior art, such as large solvent consumption and high energy consumption, the present invention provides a gas-solid reaction device and a method for preparing ZIF-8. The method of the present invention is simple, low in energy consumption, and green and environmentally friendly. The prepared particles have uniform particle size and high yield, and are easy to prepare in large quantities.

[0009] The gas-solid reaction device of the present invention comprises a solvent zone, a reaction zone, a heating device, a pressure control device and a condensation zone; The solvent area is used to store and heat the solvent to form a gas phase; the solvent area includes a first container, and a first gas phase outlet is arranged at the top of the first container; A reaction zone is used for the gas phase from the solvent zone to react with the solid phase in the reaction zone; the reaction zone includes a second container, a gas phase inlet and a second gas phase outlet are arranged on the top or side wall of the second container, the gas phase inlet is connected to the first gas phase outlet via a first pipeline; the second gas phase outlet is connected to the condensation zone via a second pipeline; Heating equipment, used to heat the solvent zone and the reaction zone to the desired temperature; The pressure control device includes a pressure control valve and a pressure sensor. The pressure control valve is arranged on the second pipeline and is used to stably and accurately control the pressure of the reaction zone. When the pressure detected by the pressure sensor exceeds the set pressure, the pressure control valve will open and release a part of the gas through the second pipeline and the water cooling pipeline to reach the condensation zone, thereby maintaining the pressure of the reaction zone constant; The condensation zone includes a heat exchange device and a third container. The heat exchange device is used to condense the gas phase from the reaction zone into a liquid phase, and the third container is used to store the condensed liquid phase.

[0010] In the gas-solid reaction device of the present invention, the first container, the second container and the third container can be selected as pressure-resistant containers, such as high-pressure reactors, according to the reaction pressure.

[0011] In the gas-solid reaction device of the present invention, the solid phase is preferably placed in the second container at a position 1 / 4 to 3 / 4 of the central axis of the container, such as by a solid-phase container supported at the bottom or suspended from the top, further such as providing a bracket, providing a tray on the bracket, or providing a hanger on the top, hanging a tray on the hanger, etc.

[0012] The present invention also provides a method for preparing ZIF-8, comprising the following contents: The solvent in the first container in the solvent zone is heated and enters the second container in the reaction zone in the form of gas phase, and reacts with the uniformly mixed zinc salt and dimethylimidazole powder in the second container at a certain reaction temperature and pressure. The product is cooled, centrifuged, washed and dried to obtain a white solid powder.

[0013] In the method of the present invention, the zinc salt is one of zinc nitrate, zinc acetate and zinc carbonate.

[0014] In the method of the present invention, the molar ratio of the zinc salt to dimethylimidazole is 1:6-8 based on metal ions.

[0015] In the method of the present invention, the solvent is water or methanol, the solid-liquid mass ratio of the powder (zinc salt and dimethylimidazole) to the solvent is 1:16-23, and the amount of the solvent is about one third of the volume of the reaction device.

[0016] In the method of the present invention, the reaction temperature is 120-150° C., the reaction pressure is 0.44-1.0 MPa, and the reaction time is 24-36 h.

[0017] In the method of the present invention, during the reaction process, the reaction pressure is maintained constant through the pressure control valve and the pressure sensor, and the excess gas phase enters the condensation zone through the pressure control valve and is condensed and recycled.

[0018] In the method of the present invention, the washing solvent is methanol, which removes the excess solute and residual solvent that have not reacted completely.

[0019] In the method of the present invention, the drying temperature is 120-150° C. and the drying time is 12-15 hours.

[0020] The ZIF-8 nanoparticles of the present invention have a particle size of 140-160 nm and a BET specific surface area of ​​1180-1332 m 2 / g, can be used in gas storage, adsorption separation, heterogeneous catalysis, electrochemistry and analysis.

[0021] Compared with the prior art, the present invention has the following advantages: the present invention uses a specific reactor and a steam-assisted method to prepare ZIF-8 nanoparticles, with less waste liquid, simple method, low energy consumption, green and environmental protection, uniform particle size, high yield of 90-94%, and easy large-scale preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of a gas-solid reaction device of the present invention, wherein 1-heating device, 2-first container, 3-first pipeline, 4-second container, 5-support, 6-tray, 7-pressure sensor, 8-pressure control valve, 9-second pipeline, 10-water cooling pipeline, 11-third container.

[0023] Figure 2 3 is a scanning electron microscope image of the ZIF-8 nanoparticles prepared in Example 1 of the present invention.

[0024] Figure 3 It is the XRD spectrum of ZIF-8 nanoparticles prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and through specific embodiments, but the content of the present invention is not limited to the following embodiments. The reagents used in this embodiment are all commonly used or commercially available products in the industry unless otherwise specified. The size of the present invention is measured by scanning electron microscope images, and the BET specific surface area is tested by low-temperature liquid nitrogen adsorption method. Example 1

[0026] 2.97g zinc nitrate and 4.93g dimethylimidazole powder were mixed evenly and placed in a tray 6; 200mL methanol was poured into the first container 2 of the reaction device, and the methanol solvent was heated and entered the second container 4 through the first pipeline 3 in the gas phase; the temperature of the second container 4 was adjusted to be constant at 120°C, the pressure value was set to 0.44MPa, and the steam pressure was controlled to be stable. When the pressure sensor 7 detected that the pressure exceeded the set pressure, the pressure control valve 8 would automatically open until the set pressure was reached; the methanol vapor in the second container 4 reacted with the zinc salt and dimethylimidazole powder mixed evenly in the tray 6, and a white solid powder was obtained after 24 hours of reaction. The excess solvent vapor released by the pressure control valve 8 was recovered to the third container 11 through the second pipeline 9 and the water cooling pipeline 10, and the recovered solvent could be recycled to the first container 1. The product was washed with methanol, centrifuged three times, and vacuum dried at 120°C for 12 hours. The yield was 90% by weighing and calculation. SEM characterization shows that the particle size is uniform, 150 nm, and the BET specific surface area is 1262 m 2 / g. Example 2

[0027] 2.97g zinc nitrate and 6.57g dimethylimidazole powder were mixed evenly and placed in a tray 6; 200mL methanol was poured into the first container 2 of the reaction device, and the methanol solvent was heated and entered the second container 4 through the first pipeline 3 in the gas phase; the temperature of the second container 4 was adjusted to be constant at 150°C, the pressure value was set to 1.0MPa, and the steam pressure was controlled to be stable. When the pressure sensor 7 detected that the pressure exceeded the set pressure, the pressure control valve 8 would automatically open until the set pressure was reached; the methanol vapor in the second container 4 reacted with the zinc salt and dimethylimidazole powder mixed evenly in the tray 6, and a white solid powder was obtained after 24 hours of reaction. The excess solvent vapor released by the pressure control valve 8 was recovered to the third container 11 through the second pipeline 9 and the water cooling pipeline 10, and the recovered solvent could be recycled to the first container 11. The product was washed with methanol, centrifuged three times, and vacuum dried at 150°C for 15 hours. The yield was 94% after weighing and calculation. SEM characterization shows that the particle size is uniform, with a size of 140 nm and a BET specific surface area of ​​1332 m 2 / g. Example 3

[0028] 2.97g zinc nitrate and 4.93g dimethylimidazole powder were mixed evenly and placed in a tray 6; 200mL methanol was poured into the first container 2 of the reaction device, and the methanol solvent was heated and entered the second container 4 through the first pipeline 3 in the gas phase; the temperature of the second container 4 was adjusted to be constant at 130°C, the pressure value was set to 0.64MPa, and the steam pressure was controlled to be stable. When the pressure sensor 7 detected that the pressure exceeded the set pressure, the pressure control valve 8 would automatically open until the set pressure was reached; the methanol vapor in the second container 4 reacted with the zinc salt and dimethylimidazole powder mixed evenly in the tray 6, and a white solid powder was obtained after 36 hours of reaction. The excess solvent vapor released by the pressure control valve 8 was recovered to the third container 11 through the second pipeline 9 and the water cooling pipeline 10, and the recovered solvent could be recycled to the first container 1. The product was washed with methanol, centrifuged three times, and vacuum dried at 130°C for 15 hours. The yield was 92% by weighing. SEM characterization shows that the particle size is uniform, 150 nm, and the BET specific surface area is 1243 m 2 / g. Example 4

[0029] 2.97g zinc nitrate and 4.93g dimethylimidazole powder were mixed evenly and placed in a tray 6; 200mL methanol was poured into the first container 2 of the reaction device, and the methanol solvent was heated and entered the second container 4 through the first pipeline 3 in the gas phase; the temperature of the second container 4 was adjusted to be constant at 140°C, the pressure value was set to 0.8MPa, and the steam pressure was controlled to be stable. When the pressure sensor 7 detected that the pressure exceeded the set pressure, the pressure control valve 8 would automatically open until the set pressure was reached; the methanol vapor in the second container 4 reacted with the zinc salt and dimethylimidazole powder mixed evenly in the tray 6, and a white solid powder was obtained after 30 hours of reaction. The excess solvent vapor released by the pressure control valve 8 was recovered to the third container 11 through the second pipeline 9 and the water cooling pipeline 10, and the recovered solvent could be recycled to the first container 1. The product was washed with methanol, centrifuged three times, and vacuum dried at 130°C for 12 hours. The yield was 93% after weighing and calculation. SEM characterization shows that the particle size is uniform, 160 nm, and the BET specific surface area is 1180 m 2 / g.

[0030] Comparative Example 1 2.97g zinc nitrate and 4.93g dimethylimidazole powder were mixed evenly and placed in a 6-tray; 200mL methanol was poured into the 2-first container of the reaction device, and the methanol solvent was heated and entered the 4-second container in the gas phase through the 3-first pipeline; the temperature of the 4-second container was adjusted to be constant at 120°C, and the steam pressure was not controlled; the methanol vapor in the 4-second container reacted with the zinc salt and dimethylimidazole powder mixed evenly in the 6-tray, and a white solid powder was obtained after 24 hours of reaction. The product was washed with methanol, centrifuged three times, and vacuum dried at 120°C for 12 hours. The yield was calculated by weighing and was 90%. SEM characterization showed that the particle size was uneven, with a size of 120-170nm and a BET specific surface area of ​​1066 m 2 / g.

[0031] Comparative Example 2 2.97g zinc nitrate powder is placed in the 6-tray; 14.08g dimethylimidazole and 200mL methanol are added to the 2-first container of the reaction device to prepare a uniform ligand solution, and the ligand solution is heated and enters the 4-second container in the gas phase through the 3-first pipeline; the temperature of the 4-second container is adjusted to be constant at 120℃, the pressure value is set to 0.44MPa, and the steam pressure is controlled to be stable. When the pressure sensor 7 detects that the pressure exceeds the set pressure, the 8-pressure control valve will automatically open until the set pressure is reached; the ligand solution vapor in the 4-second container reacts with the zinc salt mixed uniformly in the 6-tray, and a white solid powder is obtained after 24 hours of reaction. The excess ligand solution vapor released by the 8-pressure control valve is recovered to the 11-third container through the 9-second pipeline and the 10-water cooling pipeline, and the recovered ligand solution can be recycled to the 1-first container. The product is washed with methanol, centrifuged three times, and vacuum dried at 120℃ for 12 hours. The yield is low, which is 78%, calculated by weighing. SEM characterization shows that the particle size is 150 nm and the BET specific surface area is 1057 m 2 / g.

Claims

1. A gas-solid reaction device, characterized in that: It includes solvent area, reaction area, heating equipment, pressure control equipment and condensation area; The solvent area is used to store and heat the solvent to form a gas phase; the solvent area includes a first container, and a first gas phase outlet is arranged at the top of the first container; A reaction zone is used for the gas phase from the solvent zone to react with the solid phase in the reaction zone; the reaction zone includes a second container, a gas phase inlet and a second gas phase outlet are arranged on the top or side wall of the second container, the gas phase inlet is connected to the first gas phase outlet via a first pipeline; the second gas phase outlet is connected to the condensation zone via a second pipeline; Heating equipment, used to heat the solvent zone and the reaction zone to the desired temperature; A pressure control device, used to maintain a constant pressure in the reaction zone, comprising a pressure control valve and a pressure sensor. The pressure control valve is arranged on the second pipeline. When the pressure detected by the pressure sensor exceeds the set pressure, the pressure control valve opens to release a portion of the gas to the condensation zone; The condensation zone includes a heat exchange device and a third container. The heat exchange device is used to condense the gas phase from the reaction zone into a liquid phase, and the third container is used to store the condensed liquid phase.

2. The gas-solid reaction device according to claim 1, characterized in that: The first container, the second container and the third container are pressure-resistant containers according to the reaction pressure.

3. The gas-solid reaction device according to claim 1, characterized in that: The solid phase is placed in the second container at a position 1 / 4 to 3 / 4 of the central axis of the container by means of a solid phase container supported at the bottom or suspended at the top.

4. The gas-solid reaction device according to claim 3, characterized in that: A bracket is arranged in the second container, and a tray is arranged on the bracket, or a hanging piece is arranged on the top of the second container, and a tray is hung on the hanging piece.

5. A method for preparing ZIF-8 using the gas-solid reaction device according to any one of claims 1 to 4, characterized in that The method comprises the following contents: the solvent in the first container of the solvent zone is heated and enters the second container of the reaction zone in the form of gas phase, and reacts with the uniformly mixed zinc salt and dimethylimidazole powder in the second container at a certain reaction temperature and pressure; the product is cooled, centrifuged, washed and dried to obtain a white solid powder.

6. The method according to claim 5, characterized in that: The zinc salt is one of zinc nitrate, zinc acetate and zinc carbonate.

7. The method according to claim 5, characterized in that: The molar ratio of the zinc salt to dimethylimidazole is 1:6-8 based on metal ions.

8. The method according to claim 5, characterized in that: The solvent is water or methanol, and the solid-liquid mass ratio of the zinc salt and dimethylimidazole in the reaction zone to the solvent in the solvent zone is 1:16-23.

9. The method according to claim 5, characterized in that: The reaction temperature is 120-150° C., the reaction pressure is 0.44-1.0 MPa, and the reaction time is 24-36 hours.

10. The method according to claim 5, characterized in that: During the reaction, the reaction pressure is maintained constant through a pressure control valve and a pressure sensor, and the excess gas phase enters the condensation zone through the pressure control valve and is condensed and recycled.

11. The method according to claim 5, characterized in that: The drying temperature is 120-150° C. and the drying time is 12-15 hours.

12. ZIF-8 prepared according to any one of claims 5 to 11, characterized in that: The particle size is 140-160 nm and the BET specific surface area is 1180-1332 m 2 / g.

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