A method for separating ammonia-containing gas mixtures using ionic liquid hollow fiber composite membranes

Abstract

This invention discloses a method for separating ammonia-containing mixed gases using an ionic liquid hollow fiber composite membrane, belonging to the field of gas separation and purification technology. The ionic liquid hollow fiber composite membrane is prepared from an ionic liquid, a polymer, and a porous hollow fiber substrate. The prepared hollow fiber composite membrane is filled and encapsulated within a module. The ionic liquid hollow fiber composite membrane module is placed in an ammonia-containing gas membrane separation device. The ammonia-containing mixed gas enters from the raw material side of the ionic liquid hollow fiber composite membrane module. Under the action of the ammonia sites in the ionic liquid, ammonia gas preferentially permeates through the hollow fiber membrane and is collected on the permeate side. The remaining gas is collected or discharged on the residual side, thereby achieving efficient separation of the ammonia-containing mixed gas. The membrane material and module in this method are easy to prepare on a large scale. The separation method has advantages such as simple process, convenient operation, high efficiency, ease of operation, and environmental friendliness. It is suitable for the separation, purification, and recovery of ammonia-containing gases such as synthetic ammonia off-gas, smelter tail gas, chemical vapor deposition furnace tail gas, melamine tail gas, urea plant exhaust gas, nitric acid plant tail gas, and amino acid production tail gas. It is a highly promising method and technology for the separation and recovery of ammonia-containing gases.

Description

Technical Field

[0001] This invention relates to the field of gas separation technology, and in particular to a method for separating ammonia-containing mixed gases using an ionic liquid hollow fiber composite membrane. Background Technology

[0002] Ammonia (NH3), a common chemical substance, can serve as a reaction substrate in the complex synthesis of various chemicals, such as synthetic fibers, antibacterial agents, ammonium salts, and fertilizers. Meanwhile, in recent years, NH3 has been widely recognized as an energy carrier due to its high hydrogen content. Therefore, the potential applications of NH3 in energy conversion and industrial production are enormous. However, it is undeniable that NH3 emissions into the atmosphere readily react with acidic substances (SOx, NOx, etc.) to form smog. Therefore, the separation and recovery of NH3-containing exhaust gases from industrial processes has become particularly important.

[0003] Currently, solvent absorption is a common method for treating NH3-containing gases. However, it suffers from unavoidable problems such as high energy consumption, low final product value, and environmental pollution. Membrane technology, with its advantages of small footprint, high operability, and ease of scalability, is considered a promising alternative technology. However, the trade-off between permeability and selectivity of polymer membranes limits their application, necessitating the development of high-performance membrane materials. Current literature reports the development of membrane materials for ammonia separation, such as polymer membranes (cellulose acetate, polydimethylsiloxane, polytetrafluoroethylene, etc.), inorganic membranes, and mixed matrix membranes. However, most studies focus on the preparation of laboratory flat-sheet membranes and research on the permeability and ideal selectivity for separating pure ammonia. There is a lack of high-efficiency membrane materials and corresponding technologies for the separation of ammonia-containing mixed gases in industrial applications. Gas flux is inversely proportional to the thickness of the selective layer; therefore, preparing thin composite membranes is one effective way to improve flux. Due to the high packing density of hollow fiber membranes in modules, hollow fibers are typically chosen as the porous support substrate. Coating a thin selective layer onto the porous support substrate can significantly increase flux and facilitates scalable preparation. Therefore, the development of hollow fiber composite membranes composed of selective layers and porous hollow fiber supporting base membranes and ammonia separation technology is of great significance for the industrial application of membrane separation of NH3-containing gases.

[0004] This invention utilizes a coating method to internally or externally coat an ionic liquid and a polymer membrane solution onto a porous hollow fiber substrate. The resulting ionic liquid hollow fiber composite membrane fibers are then filled and sealed within a tubular structure to obtain an ionic liquid hollow fiber composite membrane module for separating ammonia-containing mixed gases from different gas sources. The ammonia-containing mixed gas enters from the feed side of the ionic liquid hollow fiber composite membrane module. Under the influence of the ammonia sites in the ionic liquid, ammonia preferentially permeates through the hollow fiber membrane to the permeate side, while the remaining gas is discharged from the permeate side, thus achieving highly efficient separation of ammonia-containing mixed gases. The membrane materials and modules produced by this method are characterized by ease of large-scale preparation, simple and efficient separation process, flexible operation, and environmental friendliness. This technology is particularly suitable for the separation, purification, and recovery of various ammonia-containing gases, including exhaust gases from synthetic ammonia, smelters, melamine plants, urea plants, nitric acid plants, and chemical vapor deposition furnaces. Summary of the Invention

[0005] The purpose of this invention is to address the lack of engineering-application-oriented membrane materials and technologies for ammonia-containing gas separation in existing membrane separation systems. This invention provides a method for separating ammonia-containing gas mixtures using an ionic liquid hollow fiber composite membrane. The membrane materials and components used in this method are easy to mass-produce, exhibit a large flux for ammonia, and a high separation factor, thereby achieving efficient separation and recovery of ammonia-containing gas mixtures.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] The ionic liquid hollow fiber composite membrane in the method of this invention is prepared from an ionic liquid, a polymer, and a porous hollow fiber substrate. The prepared ionic liquid hollow fiber composite membrane is filled and encapsulated within a module. The ionic liquid hollow fiber composite membrane module is placed in an ammonia-containing gas membrane separation device. The ammonia-containing gas mixture enters from the raw material side of the ionic liquid hollow fiber composite membrane. Under the action of the ammonia sites in the ionic liquid, ammonia gas preferentially permeates through the hollow fiber membrane to the permeate side, while the remaining gas is discharged on the permeate side, achieving efficient separation of the ammonia-containing gas mixture. Specifically:

[0008] The ionic liquid hollow fiber composite membrane of this invention consists of a selective layer and a substrate. The substrate is a porous hollow fiber made of polyvinylidene fluoride, polyvinyl chloride, or polyacrylonitrile. The selective layer is prepared by mixing a functional ionic liquid and a block polyether amide polymer in a certain proportion, with the ionic liquid comprising 1-60% by mass. The structural formula of the functional ionic liquid is as follows:

[0009]

[0010] In the structural formula, R is C n H 2n+1 (n is an integer, 0 ≤ n ≤ 8) or C n H 2nOH (n is an integer, 1≤n≤4), but not limited to the imidazole cations mentioned above; the anion X of the ionic liquid - Including NO3 - SCN - HSO4 - CF3COO - CF3SO3 - (CF3SO2)2N - Co(SCN)4 2- Li(NTf2)2 - However, it is not limited to the anions mentioned above;

[0011] In the ionic liquid hollow fiber composite membrane of the present invention, the ionic liquid and polymer are first prepared into a membrane liquid, which is then coated onto a porous hollow fiber substrate by internal or external coating. After drying, the prepared ionic liquid hollow fiber composite membrane fibers are filled and sealed in a tube to obtain an ionic liquid hollow fiber membrane module.

[0012] The ionic liquid hollow fiber composite membrane module of the present invention is installed in an ammonia-containing gas membrane separation device. The ammonia-containing gas mixture enters from the raw material side of the hollow fiber composite membrane module. Under the action of the ionic liquid sites, ammonia gas preferentially permeates and is transported to the permeate side, while the remaining gas is discharged from the permeate side. It has a high permeation flux and separation factor for ammonia gas.

[0013] The ionic liquid hollow fiber composite membrane of the present invention can separate an ammonia-containing mixed gas with an ammonia concentration of 1.5-70%, and the remaining gases include one, two, three or more of air, nitrogen, hydrogen, methane and carbon dioxide, with an inlet pressure of 0.01-5 MPa and a temperature of 10-120℃.

[0014] This invention prepares an ionic liquid polymer selective layer on the surface of a hollow fiber membrane using a coating method. Under the action of the ionic liquid ammonia sites, ammonia gas preferentially permeates through the selective layer of the hollow fiber membrane and is transported to the permeate side, thereby achieving efficient separation of ammonia-containing gas mixtures. Compared with existing technologies, the ionic liquid hollow fiber composite membrane of this invention combines high ammonia permeability, separation selectivity, and good stability. The method of using ionic liquid hollow fiber composite membranes for separating ammonia-containing gases has advantages such as simple process, high separation efficiency, ease of operation, and environmental friendliness. It can be used for the separation and purification of ammonia synthesis off-gas, smelter tail gas, chemical vapor deposition furnace tail gas, melamine tail gas, urea plant emission tail gas, nitric acid plant tail gas, amino acid production tail gas, etc., and is a promising new technology for the separation and recovery of ammonia-containing gases. Detailed Implementation

[0015] The technical solution of the present invention will be described in more detail below through specific embodiments. However, the present invention is not limited to the following embodiments. Any variations are included within the technical scope of the present invention without departing from the scope described above.

[0016] Example 1

[0017] 1) Using ethanol / water (70wt% / 30wt%) as a mixed solvent, Pebax 1657 particles were dissolved by reflux at 80°C and stirred for 4 hours to obtain a Pebax 1657 membrane solution with a concentration of 3wt%. Ionic liquid [Eim][NTf2] was weighed and added to the above Pebax 1657 membrane solution, and stirred at room temperature for 2 hours to obtain a [Eim][NTf2] / Pebax 1657 membrane solution with a 15% ionic liquid mass fraction.

[0018] 2) The above membrane liquid is coated onto polyvinylidene fluoride (PVDF) hollow fiber membrane filaments and dried in an oven at 60°C to obtain 15wt% [Eim][NTf2] / Pebax 1657 / PVDF ionic liquid hollow fiber composite membrane filaments; the membrane filaments are further filled and encapsulated in a tube to prepare a 15wt% [Eim][NTf2] / Pebax1657 / PVDF ionic liquid hollow fiber composite membrane module.

[0019] 3) The prepared 15wt% [Eim][NTf2] / Pebax 1657 / PVDF ionic liquid hollow fiber composite membrane module was installed and connected to an ammonia-containing gas membrane separation device for separation testing. The feed gas was a 1.5% / 98.5% NH3 / N2 mixture, the feed-side pressure was 0.15 MPa, and the temperature was room temperature. Ammonia in the feed gas preferentially permeated through the ionic liquid hollow fiber composite membrane to the permeate side. Gas chromatography was used to detect the gas concentration on the permeate side and the residual gas concentration on the residual side, and the gas permeation flux and separation factor were calculated. The tail gas was absorbed by sulfuric acid solution.

[0020] 4) The separation performance of the 15wt% [Eim][NTf2] / Pebax 1657 / PVDF ionic liquid hollow fiber composite membrane for 1.5% / 98.5% NH3 / N2 mixture is as follows: NH3 permeation flux is 114.7 GPU and NH3 / N2 separation factor is 103.2.

[0021] Example 2

[0022] 1) Using ethanol / water (70wt% / 30wt%) as a mixed solvent, Pebax 1657 particles were dissolved by reflux at 80°C and stirred for 4 hours to obtain a Pebax 1657 membrane solution with a concentration of 3wt%. Ionic liquid [Eim][NTf2] was weighed and added to the above Pebax 1657 membrane solution, and stirred at room temperature for 2 hours to obtain a [Eim][NTf2] / Pebax 1657 membrane solution with a 15% ionic liquid mass fraction.

[0023] 2) The above membrane liquid is coated onto PVDF hollow fiber membrane fibers and dried in an oven at 60°C to obtain 15wt% [Eim][NTf2] / Pebax 1657 / PVDF ionic liquid hollow fiber composite membrane fibers; the membrane fibers are further filled and encapsulated in a tube to prepare a 15wt% [Eim][NTf2] / Pebax 1657 / PVDF ionic liquid hollow fiber composite membrane module.

[0024] 3) The prepared 15wt% [Eim][NTf2] / Pebax 1657 / PVDF ionic liquid hollow fiber composite membrane module was installed and connected to an ammonia-containing gas membrane separation device for separation testing. The feed gas was a 50% / 50% NH3 / N2 mixture, the feed-side pressure was 0.2 MPa, and the temperature was room temperature. Ammonia in the feed gas preferentially permeated through the ionic liquid hollow fiber composite membrane to the permeate side. Gas chromatography was used to detect the gas concentration on the permeate side and the residual gas concentration on the residual side, and the gas permeation flux and separation factor were calculated. The tail gas was absorbed by sulfuric acid solution.

[0025] 4) The separation performance of the 15wt% [Eim][NTf2] / Pebax 1657 / PVDF ionic liquid hollow fiber composite membrane for 50% / 50% NH3 / N2 mixture is as follows: NH3 permeation flux is 330 GPU, and NH3 / N2 separation factor is 72.

[0026] Example 3

[0027] 1) Using ethanol / water (70wt% / 30wt%) as a mixed solvent, Pebax 1657 particles were dissolved by reflux at 80°C and stirred for 4 hours to obtain a Pebax 1657 membrane solution with a concentration of 3wt%. Ionic liquid [Eim][NTf2] was weighed and added to the above Pebax 1657 membrane solution, and stirred at room temperature for 2 hours to obtain a [Eim][NTf2] / Pebax 1657 membrane solution with a 15% ionic liquid mass fraction.

[0028] 2) The above membrane liquid is coated onto PVDF hollow fiber membrane fibers and dried in an oven at 60°C to obtain 15wt% [Eim][NTf2] / Pebax 1657 / PVDF ionic liquid hollow fiber composite membrane fibers; the membrane fibers are further filled and encapsulated in a tube to prepare a 15wt% [Eim][NTf2] / Pebax 1657 / PVDF ionic liquid hollow fiber composite membrane module.

[0029] 3) The prepared 15wt% [Eim][NTf2] / Pebax 1657 / PVDF ionic liquid hollow fiber composite membrane module was installed and connected to an ammonia-containing gas membrane separation device for separation testing. The feed gas was a mixture of 15% / 25% / 60% NH3 / H2 / N2, with a feed-side pressure of 0.2 MPa and a temperature of room temperature. Ammonia in the feed gas preferentially permeated through the ionic liquid hollow fiber composite membrane to the permeate side. Gas chromatography was used to detect the gas concentration on the permeate side and the residual gas concentration on the residual side, and the gas permeation flux and separation factor were calculated. The tail gas was absorbed by sulfuric acid solution.

[0030] 4) The separation performance of the 15wt% [Eim][NTf2] / Pebax 1657 / PVDF ionic liquid hollow fiber composite membrane for 15% / 25% / 60% NH3 / H2 / N2 mixtures is as follows: NH3 permeation flux is 261.6 GPU, and NH3 / N2 separation factor is 74.7.

[0031] Example 4

[0032] 1) Using anhydrous ethanol as a solvent, Pebax 2533 particles were dissolved by reflux at 80°C and stirred for 4 hours to obtain a Pebax 2533 membrane solution with a concentration of 2 wt%. Ionic liquid [Bim][NTf2] was weighed and added to the above Pebax 2533 membrane solution, and stirred at room temperature for 2 hours to obtain a [Bim][NTf2] / Pebax 2533 membrane solution with a 50% ionic liquid mass fraction.

[0033] 2) Polyvinyl chloride (PVC) hollow fiber membrane filaments are filled and encapsulated inside a pipe to obtain a hollow fiber membrane module. The above membrane solution is internally coated onto the PVC hollow fiber membrane filaments and dried in an oven at 60°C to obtain a 50wt% [Bim][NTf2] / Pebax2533 / PVC ionic liquid hollow fiber composite membrane module.

[0034] 3) The prepared 50wt% [Bim][NTf2] / Pebax 2533 / PVC ionic liquid hollow fiber composite membrane module was installed and connected to an ammonia-containing gas membrane separation device for separation testing. The feed gas was a 1.5% / 98.5% NH3 / N2 mixture, the feed-side pressure was 0.3MPa, and the temperature was room temperature. Ammonia in the feed gas preferentially permeated through the ionic liquid hollow fiber composite membrane to the permeate side. Gas chromatography was used to detect the gas concentration on the permeate side and the residual gas concentration on the residual side, and the gas permeation flux and separation factor were calculated. The tail gas was absorbed by sulfuric acid solution.

[0035] 4) The separation performance of the 50wt% [Bim][NTf2] / Pebax 2533 / PVC ionic liquid hollow fiber composite membrane for 1.5% / 98.5% NH3 / N2 mixture is as follows: NH3 permeation flux is 200 GPU, and NH3 / N2 separation factor is 92.

[0036] Example 5

[0037] 1) Using anhydrous ethanol as a solvent, Pebax 2533 particles were dissolved by reflux at 80°C and stirred for 4 hours to obtain a Pebax 2533 membrane solution with a concentration of 2 wt%. Ionic liquid [Bim][NTf2] was weighed and added to the above Pebax 2533 membrane solution, and stirred at room temperature for 2 hours to obtain a [Bim][NTf2] / Pebax 2533 membrane solution with a 50% ionic liquid mass fraction.

[0038] 2) PVC hollow fiber membrane filaments are filled and encapsulated inside a pipe to obtain a hollow fiber membrane module. The above membrane solution is internally coated onto the PVC hollow fiber membrane filaments and dried in an oven at 60°C to obtain a 50wt% [Bim][NTf2] / Pebax 2533 / PVC ionic liquid hollow fiber composite membrane module.

[0039] 3) The prepared 50wt% [Bim][NTf2] / Pebax 2533 / PVC ionic liquid hollow fiber composite membrane module was installed and connected to an ammonia-containing gas membrane separation device for separation testing. The feed gas was a 10% / 90% NH3 / N2 mixture, the feed-side pressure was 0.2MPa, and the temperature was room temperature. Ammonia in the feed gas preferentially permeated through the ionic liquid hollow fiber composite membrane to the permeate side. Gas chromatography was used to detect the gas concentration on the permeate side and the residual gas concentration on the residual side, and the gas permeation flux and separation factor were calculated. The tail gas was absorbed by sulfuric acid solution.

[0040] 4) The separation performance of the 50wt% [Bim][NTf2] / Pebax 2533 / PVC ionic liquid hollow fiber composite membrane for 10% / 90% NH3 / N2 mixture is as follows: NH3 permeation flux is 215 GPU, and NH3 / N2 separation factor is 90.

[0041] Example 6

[0042] 1) Using anhydrous ethanol as a solvent, Pebax 2533 particles were dissolved by reflux at 80°C and stirred for 4 hours to obtain a Pebax 2533 membrane solution with a concentration of 2 wt%. Ionic liquid [Bim][NTf2] was weighed and added to the above Pebax 2533 membrane solution, and stirred at room temperature for 2 hours to obtain a [Bim][NTf2] / Pebax 2533 membrane solution with a 50% ionic liquid mass fraction.

[0043] 2) PVC hollow fiber membrane filaments are filled and encapsulated inside a pipe to obtain a hollow fiber membrane module. The above membrane solution is internally coated onto the PVC hollow fiber membrane filaments and dried in an oven at 60°C to obtain a 50wt% [Bim][NTf2] / Pebax 2533 / PVC ionic liquid hollow fiber composite membrane module.

[0044] 3) The prepared 50wt% [Bim][NTf2] / Pebax 2533 / PVC ionic liquid hollow fiber composite membrane module was installed and connected to an ammonia-containing gas membrane separation device for separation testing. The feed gas was a 50% / 50% NH3 / N2 mixture, the feed-side pressure was 0.2MPa, and the temperature was room temperature. Ammonia in the feed gas preferentially permeated through the ionic liquid hollow fiber composite membrane to the permeate side. Gas chromatography was used to detect the gas concentration on the permeate side and the residual gas concentration on the residual side, and the gas permeation flux and separation factor were calculated. The tail gas was absorbed by sulfuric acid solution.

[0045] 4) The separation performance of the 50wt% [Bim][NTf2] / Pebax 2533 / PVC ionic liquid hollow fiber composite membrane for 50% / 50% NH3 / N2 mixture is as follows: NH3 permeation flux is 337 GPU, and NH3 / N2 separation factor is 89.6.

[0046] Example 7

[0047] 1) Using ethanol / water (70wt% / 30wt%) as a mixed solvent, Pebax 1657 particles were dissolved by reflux at 80°C and stirred for 4 hours to obtain a Pebax 1657 membrane solution with a concentration of 1wt%. Ionic liquid [Im][NTf2] was weighed and added to the above Pebax 1657 membrane solution, and stirred at room temperature for 2 hours to obtain a [Im][NTf2] / Pebax 1657 membrane solution with a 50% ionic liquid mass fraction.

[0048] 2) PVC hollow fiber membrane filaments are filled and sealed inside a pipe to obtain a hollow fiber membrane module. The above membrane solution is internally coated onto the PVC hollow fiber membrane filaments and dried in an oven at 60°C to obtain a 50wt% [Im][NTf2] / Pebax 1657 / PVC ionic liquid hollow fiber composite membrane module.

[0049] 3) The prepared 50wt% [Im][NTf2] / Pebax 1657 / PVC ionic liquid hollow fiber composite membrane module was installed and connected to an ammonia-containing gas membrane separation device for separation testing. The feed gas was a 50% / 50% NH3 / N2 mixture, the feed-side pressure was 0.2MPa, and the temperature was room temperature. Ammonia in the feed gas preferentially permeated through the ionic liquid hollow fiber composite membrane to the permeate side. Gas chromatography was used to detect the gas concentration on the permeate side and the residual gas concentration on the residual side, and the gas permeation flux and separation factor were calculated. The tail gas was absorbed by sulfuric acid solution.

[0050] 4) The separation performance of the 50wt% [Im][NTf2] / Pebax 1657 / PVC ionic liquid hollow fiber composite membrane for 50% / 50% NH3 / N2 mixture is as follows: NH3 permeation flux is 234.3 GPU, and NH3 / N2 separation factor is 50.

[0051] Example 8

[0052] 1) Using ethanol / water (70wt% / 30wt%) as a mixed solvent, Pebax 1657 particles were dissolved by reflux at 80°C and stirred for 4 hours to obtain a Pebax 1657 membrane solution with a concentration of 1wt%. The ionic liquid [Bim][NO3] was weighed and added to the above Pebax 1657 membrane solution, and stirred at room temperature for 2 hours to obtain a [Bim][NO3] / Pebax 1657 membrane solution with a 35% ionic liquid mass fraction.

[0053] 2) PVC hollow fiber membrane filaments are filled and sealed inside a pipe to obtain a hollow fiber membrane module. The above membrane solution is internally coated onto the PVC hollow fiber membrane filaments and dried in an oven at 60°C to obtain a 35wt% [Bim][NO3] / Pebax 1657 / PVC ionic liquid hollow fiber composite membrane module.

[0054] 3) The prepared 35wt% [Bim][NO3] / Pebax 1657 / PVC ionic liquid hollow fiber composite membrane module was installed and connected to an ammonia-containing gas membrane separation device for separation testing. The feed gas was a 10% / 90% NH3 / N2 mixture, the feed-side pressure was 0.2MPa, and the temperature was room temperature. Ammonia in the feed gas preferentially permeated through the ionic liquid hollow fiber composite membrane to the permeate side. Gas chromatography was used to detect the gas concentration on the permeate side and the residual gas concentration on the residual side, and the gas permeation flux and separation factor were calculated. The tail gas was absorbed by sulfuric acid solution.

[0055] 4) The separation performance of the 35wt% [Bim][NO3] / Pebax 1657 / PVC ionic liquid hollow fiber composite membrane for 10% / 90% NH3 / N2 mixture is as follows: NH3 permeation flux is 54.3 GPU and NH3 / N2 separation factor is 21.6.

[0056] Example 9

[0057] 1) Using ethanol / water (70wt% / 30wt%) as a mixed solvent, Pebax 1657 particles were dissolved by reflux at 80°C and stirred for 4 hours to obtain a Pebax 1657 membrane solution with a concentration of 1wt%. The ionic liquid [Bim][NO3] was weighed and added to the above Pebax 1657 membrane solution, and stirred at room temperature for 2 hours to obtain a [Bim][NO3] / Pebax 1657 membrane solution with a 50% ionic liquid mass fraction.

[0058] 2) PVC hollow fiber membrane filaments are filled and sealed inside a pipe to obtain a hollow fiber membrane module. The above membrane solution is internally coated onto the PVC hollow fiber membrane filaments and dried in an oven at 60°C to obtain a 50wt% [Bim][NO3] / Pebax 1657 / PVC ionic liquid hollow fiber composite membrane module.

[0059] 3) The prepared 50wt% [Bim][NO3] / Pebax 1657 / PVC ionic liquid hollow fiber composite membrane module was installed and connected to an ammonia-containing gas membrane separation device for testing. The feed gas was a 50% / 50% NH3 / N2 mixture, the feed-side pressure was 0.2MPa, and the temperature was room temperature. Ammonia in the feed gas preferentially permeated through the ionic liquid hollow fiber composite membrane to the permeate side. Gas chromatography was used to detect the gas concentration on the permeate side and the residual gas concentration on the residual side, and the gas permeation flux and separation factor were calculated. The tail gas was absorbed by sulfuric acid solution.

[0060] 4) The separation performance of the 50wt% [Bim][NO3] / Pebax 1657 / PVC ionic liquid hollow fiber composite membrane for 50% / 50% NH3 / N2 mixture is as follows: NH3 permeation flux is 210.7 GPU, and NH3 / N2 separation factor is 45.8.

[0061] Example 10

[0062] 1) Using ethanol / water (70wt% / 30wt%) as a mixed solvent, Pebax 1657 particles were dissolved by reflux at 80°C and stirred for 4 hours to obtain a Pebax 1657 membrane solution with a concentration of 1wt%. Ionic liquid [Bim][TfO] was weighed and added to the above Pebax 1657 membrane solution, and stirred at room temperature for 2 hours to obtain a [Bim][TfO] / Pebax 1657 membrane solution with a 40% ionic liquid mass fraction.

[0063] 2) PVC hollow fiber membrane filaments are filled and sealed inside a pipe to obtain a hollow fiber membrane module. The above membrane solution is internally coated onto the PVC hollow fiber membrane filaments and dried in an oven at 60°C to obtain a 40wt% [Bim][TfO] / Pebax 1657 / PVC ionic liquid hollow fiber composite membrane module.

[0064] 3) The prepared 40wt% [Bim][TfO] / Pebax 1657 / PVC ionic liquid hollow fiber composite membrane module was installed and connected to an ammonia-containing gas membrane separation device for separation testing. The feed gas was a 50% / 50% NH3 / N2 mixture, the feed-side pressure was 0.2MPa, and the temperature was room temperature. Ammonia in the feed gas preferentially permeated through the ionic liquid hollow fiber composite membrane to the permeate side. Gas chromatography was used to detect the gas concentration on the permeate side and the residual gas concentration on the residual side, and the gas permeation flux and separation factor were calculated. The tail gas was absorbed by sulfuric acid solution.

[0065] 4) The separation performance of the 40wt% [Bim][TfO] / Pebax 1657 / PVC ionic liquid hollow fiber composite membrane for 50% / 50% NH3 / N2 mixture is as follows: NH3 permeation flux is 223.7 GPU, and NH3 / N2 separation factor is 31.2.

Claims

1. A method for separating ammonia-containing gas mixtures using an ionic liquid hollow fiber composite membrane, characterized in that, The ionic liquid hollow fiber composite membrane is prepared from ionic liquid, polymer, and porous hollow fiber substrate. The ionic liquid and polymer membrane solutions are internally or externally coated on the porous hollow fiber substrate layer. The prepared ionic liquid hollow fiber composite membrane is then filled and encapsulated into a module to obtain an ionic liquid hollow fiber composite membrane module. This module is placed in an ammonia-containing gas membrane separation device. The ammonia-containing gas mixture enters from the raw material side of the ionic liquid hollow fiber composite membrane. Under the action of the ammonia sites in the ionic liquid, ammonia gas preferentially permeates through the hollow fiber membrane to the permeate side, while the remaining gas is discharged on the permeate side, achieving efficient separation of the ammonia-containing gas mixture. The ionic liquid has the following structural formula: In the structural formula, R is C n H 2n+1 Where n is an integer, 0 ≤ n ≤ 8 or C n H 2n OH, where n is an integer, 1≤n≤4; the anion X of the ionic liquid - Including NO3 - SCN - HSO4 - CF3COO - CF3SO3 - (CF3SO2)2N - Co(SCN)4 2- and Li(NTf2)2 - ; The polymer is a block polyether amide; The porous hollow fiber substrate is made of polyvinylidene fluoride, polyvinyl chloride, or polyacrylonitrile. The mass percentage of ionic liquid in the ionic liquid hollow fiber composite membrane is 1-60%.

2. The method according to claim 1, characterized in that, The ionic liquid hollow fiber composite membrane module is placed in an ammonia-containing gas membrane separation device. The ammonia-containing gas mixture enters from the raw material side of the hollow fiber composite membrane module. Under the action of the ionic liquid sites, the ammonia gas preferentially permeates and is transported to the permeate side, while the remaining gas is discharged from the permeate side.

3. The method according to claim 1, characterized in that, The ionic liquid hollow fiber composite membrane separates an ammonia-containing gas mixture with an ammonia concentration of 1.5-70%, and the remaining gases include one or more of nitrogen, hydrogen, methane, and carbon dioxide. The inlet pressure is 0.01-5 MPa, and the temperature is 10-120 ℃.

4. The method according to claim 1, characterized in that, The ionic liquid hollow fiber composite membrane and components are suitable for the separation, purification and recovery of different ammonia-containing gases, including synthetic ammonia off-gas, smelter tail gas, chemical vapor deposition furnace tail gas, melamine tail gas, urea plant emission tail gas, nitric acid plant tail gas or amino acid production tail gas, and can achieve efficient separation and recovery of ammonia.

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