Method for separating ammonia gas by using protonated amine type ionic liquid membrane

Abstract

The invention discloses a method for separating ammonia gas by a protonated amine type ionic liquid membrane, and belongs to the technical field of gas separation. The protonated amine type ionic liquid membrane is prepared from protonated amine type ionic liquid and a block polyether amide polymer, and is characterized in that the protonated amine type ionic liquid membrane is prepared through hydrogen-bond interaction between proton hydrogen and hydroxyl sites and ammonia molecules and the free volume effect of the membrane; ammonia gas directly and selectively penetrates through the other side of the membrane from one side of the membrane, so that high-selectivity separation of the ammonia gas is realized. The method has the advantages of high ammonia gas separation performance, small occupied area of equipment, environment friendliness, simple process, capability of directly obtaining ammonia gas without phase change and the like, and has a great application prospect in the aspect of separation and purification of ammonia-containing gas.

Description

Technical Field

[0001] The present invention relates to the technical field of gas separation, and in particular to a method for separating ammonia gas by a protonated amine-based ionic liquid membrane. Background Art

[0002] Ammonia is an important basic raw material for agriculture and chemical industry, and is also considered as a flexible and effective energy storage medium. At the same time, the excessive emission of ammonia will also harm the environment and human health, even at very low concentrations of NH3. The amount of ammonia-containing gas is large and widespread. For example, a large amount of ammonia-containing gas will be generated in industrial processes such as ammonia synthesis, ammonium molybdate production, melamine production, and refrigeration systems. Therefore, the separation and recovery of ammonia is of great significance for circular low-carbon economy, resource utilization and environmental protection. Existing traditional ammonia treatment technologies generally have some problems. For example, the water washing method has a large water consumption, high regeneration energy consumption, and generates a large amount of wastewater during the treatment process, causing secondary pollution to the environment; the acid washing method will cause serious corrosion of equipment while generating a large amount of difficult-to-treat waste liquid, and the value-added of the generated ammonium salt is low. Therefore, there is an urgent need to develop new and efficient ammonia separation and recovery technologies.

[0003] Membrane separation technology has many advantages such as high efficiency, energy saving, environmental protection, and easy operation, and is one of the ammonia separation technologies with development potential. However, the ammonia separation performance of existing membrane materials still needs to be further improved to meet the application requirements. As a new type of functional solvent and green medium, ionic liquids have the characteristics of low volatility and strong structural tunability. By designing different cations and anions or introducing functional groups to adjust their acidity and alkalinity, polarity, site interaction strength, etc., high-selectivity separation of ammonia gas can be achieved. Introducing ionic liquids into membrane materials can promote the preferential penetration of ammonia molecules in the membrane by regulating the membrane microstructure and increasing the solubility of ammonia, thereby improving the permeability and selectivity of the membrane to ammonia.

[0004] Based on the above analysis, the present invention has developed a method for separating ammonia gas by a protonated amine-based ionic liquid membrane. Combining the advantages of high NH3 affinity of ionic liquids and membrane separation, a protonated amine-based ionic liquid membrane prepared from functional ionic liquids and block polyether amides is developed. High-selectivity separation of ammonia gas is achieved through the hydrogen bond interaction between the proton hydrogen and hydroxyl sites in the membrane and ammonia molecules, as well as the free volume effect of the membrane. This method has the advantages of high separation efficiency, simple process, flexible and convenient operation, no phase change and chemical pollution when separating ammonia-containing gas, and has broad application prospects. It is suitable for the separation and purification of ammonia-containing gases with different concentrations such as ammonium molybdate production tail gas, ammonia synthesis purge gas, chemical vapor deposition furnace tail gas, melamine tail gas, urea plant emission tail gas, coke oven gas, and nitric acid plant tail gas. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for separating ammonia gas by a protonated amine-based ionic liquid membrane.

[0006] The protonated amine-based ionic liquid membrane of the present invention interacts with ammonia through proton hydrogen and hydroxyl sites, and synergistically with the free volume effect of the membrane, promoting the preferential permeation of ammonia from one side of the membrane to the other side, thereby achieving the selective separation of ammonia.

[0007] The protonated amine-based ionic liquid membrane of the present invention is prepared from a protonated amine-based ionic liquid and a block polyether amide polymer in a certain proportion, where the mass percentage of the ionic liquid is 1%-200% of the polymer, preferably 1%-180%.

[0008] The anion of the protonated amine-based ionic liquid of the present invention is NO3 - , BF4 - , PF6 - , CF3COO - , CF3SO3 - (TfO - ), (CF3SO2)2N - (NTf2 - ), CH3SO3 - , HSO4 - , H2PO4 - , COO - , CH3COO - ; The cation has the following structure:

[0009]

[0010] In the structural formula, R1 is H or C n H 2n+1 ; R2, R3 and R4 are C n H 2n+1 ; R5 is C n H 2n ; R6 and R7 are C n H 2n O; n is an integer, 1≤n≤4;

[0011] The prepared protonated amine-based ionic liquid membrane is hermetically fixed in a membrane separation device, and the whole system is evacuated. Then, the test pressure is 0.01-5 MPa, and the test temperature is 10-120 °C. Ammonia directly permeates from one side of the membrane to the other side. By detecting the change of the pressure on the permeate side with time, the permeability and selectivity are calculated.

[0012] The method for separating ammonia by the protonated amine-based ionic liquid membrane of the present invention is applicable to the separation, purification and recovery of ammonia in the tail gas generated from ammonium molybdate production, ammonia synthesis purge gas, chemical vapor deposition furnace tail gas, urea production tail gas, ammonium nitrate production tail gas, coke oven gas, melamine production tail gas, and amino acid production tail gas.

[0013] Compared with the prior art, the method of the present invention has a high ammonia separation efficiency, is flexible and convenient to operate, environmentally friendly, has a simple process, and can directly obtain gaseous ammonia without phase change, and has broad application prospects in the field of ammonia separation and recovery. Detailed Embodiments

[0014] The technical solutions 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. Within the scope without departing from the foregoing, various changes and implementations are included in the technical scope of the present invention.

[0015] Example 1

[0016] 1) Using anhydrous ethanol and deionized water as a mixed solvent (mass ratio 7:3), prepare a polymer solution with a Pebax1657 mass concentration of 8%. After the solution is cooled to room temperature, add [N 222 [NTf2] with a mass 120% of the polymer to the Pebax1657 solution, stir at room temperature for 4 h, then pour the uniformly mixed membrane solution onto a customized mold, and after solvent evaporation at room temperature and vacuum drying at 60 °C, obtain the [N 222 [NTf2] / Pebax-120 ionic liquid membrane.

[0017] 2) Seal the prepared [N 222 [NTf2] / Pebax-120 ionic liquid membrane in a membrane gas separation device. The test temperature is 30 °C and the test pressure is 0.1 MPa. Pass N2, H2, and NH3 into the feed side. By detecting the change of the pressure on the permeate side of the membrane with time, the permeability of NH3 is calculated to be 3784 barrer, the separation selectivity of NH3 / H2 is 99, and the separation selectivity of NH3 / N2 is 495.

[0018] Example 2

[0019] 1) Using anhydrous ethanol and deionized water as a mixed solvent (mass ratio 7:3), prepare a polymer solution with a Pebax1657 mass concentration of 8%. After the solution is cooled to room temperature, add [N 222 [NTf2] with a mass 160% of the polymer to the Pebax1657 solution, stir at room temperature for 4 h, then pour the uniformly mixed membrane solution onto a customized mold, and after solvent evaporation at room temperature and vacuum drying at 60 °C, obtain the [N 222 [NTf2] / Pebax-160 ionic liquid membrane.

[0020] 2) The prepared [N 222[NTf2] / Pebax-160 ionic liquid membrane was sealed in a membrane gas separation device. The test temperature was 30 °C and the test pressure was 0.1 MPa. N2, H2 and NH3 were introduced on the feed side. By detecting the change of the pressure on the permeate side of the membrane over time, the permeability of NH3 was calculated to be 5563 barrer, the separation selectivity of NH3 / H2 was 108, and the separation selectivity of NH3 / N2 was 468.

[0021] Example 3

[0022] 1) Using absolute ethanol and deionized water as a mixed solvent (mass ratio 7:3), a polymer solution with a Pebax1657 mass concentration of 8% was prepared. After the solution was cooled to room temperature, [EdteH6][TfO] with a mass of 60% of the polymer was added to the Pebax1657 solution, and stirred at room temperature for 4 h. Then the uniformly mixed membrane solution was poured into a customized mold. After solvent evaporation at room temperature and vacuum drying at 60 °C, the [EdteH6][TfO] / Pebax-60 ionic liquid membrane was obtained.

[0023] 2) The prepared [EdteH6][TfO] / Pebax-60 ionic liquid membrane was sealed in a membrane gas separation device. The test temperature was 30 °C and the test pressure was 0.1 MPa. N2, H2 and NH3 were introduced on the feed side. By detecting the change of the pressure on the permeate side of the membrane over time, the permeability of NH3 was calculated to be 824 barrer, the separation selectivity of NH3 / H2 was 191, and the separation selectivity of NH3 / N2 was 1773.

[0024] Example 4

[0025] 1) Using absolute ethanol and deionized water as a mixed solvent (mass ratio 7:3), a polymer solution with a Pebax1657 mass concentration of 8% was prepared. After the solution was cooled to room temperature, [EdteH6][TfO] with a mass of 80% of the polymer was added to the Pebax1657 solution, and stirred at room temperature for 4 h. Then the uniformly mixed membrane solution was poured into a customized mold. After solvent evaporation at room temperature and vacuum drying at 60 °C, the [EdteH6][TfO] / Pebax-80 ionic liquid membrane was obtained.

[0026] 2) The prepared [EdteH6][TfO] / Pebax-80 ionic liquid membrane was sealed in a membrane gas separation device. The test temperature was 30 °C and the test pressure was 0.1 MPa. N2, H2 and NH3 were introduced on the feed side. By detecting the change of the pressure on the permeate side of the membrane over time, the permeability of NH3 was calculated to be 1223 barrer, the separation selectivity of NH3 / H2 was 311, and the separation selectivity of NH3 / N2 was 3511.

[0027] Example 5

[0028] 1) Using absolute ethanol and deionized water as a mixed solvent (mass ratio 7:3), a polymer solution with a Pebax 1657 mass concentration of 8% was prepared. After the solution was cooled to room temperature, [EdteH6][TfO] with a mass of 80% of the polymer was added to the Pebax 1657 solution, and the mixture was stirred at room temperature for 4 h. Then, the uniformly mixed membrane solution was poured onto a customized mold. After solvent evaporation at room temperature and vacuum drying at 60 °C, the [EdteH6][TfO] / Pebax-80 ionic liquid membrane was obtained.

[0029] 2) The prepared [EdteH6][TfO] / Pebax-80 ionic liquid membrane was sealed in a membrane gas separation device. The test temperature was 50 °C and the test pressure was 0.1 MPa. N2, H2, and NH3 were introduced on the feed side. By detecting the change in pressure on the permeate side of the membrane over time, the permeability of NH3 was calculated to be 1357 barrer, the separation selectivity of NH3 / H2 was 132, and the separation selectivity of NH3 / N2 was 743.

[0030] Example 6

[0031] 1) Using absolute ethanol and deionized water as a mixed solvent (mass ratio 7:3), a polymer solution with a Pebax 1657 mass concentration of 8% was prepared. After the solution was cooled to room temperature, [EdteH6][TfO] with a mass of 80% of the polymer was added to the Pebax 1657 solution, and the mixture was stirred at room temperature for 4 h. Then, the uniformly mixed membrane solution was poured onto a customized mold. After solvent evaporation at room temperature and vacuum drying at 60 °C, the [EdteH6][TfO] / Pebax-80 ionic liquid membrane was obtained.

[0032] 2) The prepared [EdteH6][TfO] / Pebax-80 ionic liquid membrane was sealed in a membrane gas separation device. The test temperature was 60 °C and the test pressure was 0.1 MPa. N2, H2, and NH3 were introduced on the feed side. By detecting the change in pressure on the permeate side of the membrane over time, the permeability of NH3 was calculated to be 1446 barrer, the separation selectivity of NH3 / H2 was 93, and the separation selectivity of NH3 / N2 was 449.

[0033] Example 7

[0034] 1) Using absolute ethanol and deionized water as a mixed solvent (mass ratio 7:3), a polymer solution with a Pebax 1657 mass concentration of 8% was prepared. After the solution was cooled to room temperature, [N with a mass of 140% of the polymer 222[NTf2] was added to the Pebax1657 solution, and the mixture was stirred at room temperature for 4 h. Then, the uniformly mixed membrane solution was poured into a customized mold. After solvent evaporation at room temperature and vacuum drying at 60 °C, [N 222 [NTf2] / Pebax-140 ionic liquid membrane was obtained.

[0035] 2) The prepared [N 222 [NTf2] / Pebax-140 ionic liquid membrane was sealed in a membrane gas separation device. The test temperature was 30 °C, and the test pressure was 0.2 MPa. N2, H2, and NH3 were introduced on the feed side. By detecting the change in the pressure on the permeate side of the membrane over time, the permeability of NH3 was calculated to be 7409 barrer, the separation selectivity of NH3 / H2 was 159, and the separation selectivity of NH3 / N2 was 778.

[0036] Example 8

[0037] 1) Using absolute ethanol and deionized water as a mixed solvent (mass ratio 7:3), a polymer solution with a Pebax1657 mass concentration of 8% was prepared. After the solution was cooled to room temperature, [EdteH6][TfO] with a mass of 80% of the polymer was added to the Pebax1657 solution, and the mixture was stirred at room temperature for 4 h. Then, the uniformly mixed membrane solution was poured into a customized mold. After solvent evaporation at room temperature and vacuum drying at 60 °C, [EdteH6][TfO] / Pebax-80 ionic liquid membrane was obtained.

[0038] 2) The prepared [EdteH6][TfO] / Pebax-80 ionic liquid membrane was sealed in a membrane gas separation device. The test temperature was 30 °C, and the test pressure was 0.3 MPa. N2, H2, and NH3 were introduced on the feed side. By detecting the change in the pressure on the permeate side of the membrane over time, the permeability of NH3 was calculated to be 3486 barrer, the separation selectivity of NH3 / H2 was 1234, and the separation selectivity of NH3 / N2 was 9408.

Claims

1. A method for separating ammonia by a protonated amine-based ionic liquid membrane, characterized in that, The protonated amine-based ionic liquid membrane has proton hydrogen and hydroxyl sites that interact with ammonia, enabling ammonia to preferentially permeate from one side of the membrane to the other, thereby achieving the selective separation of ammonia. The cationic structure of the protonated amine-based ionic liquid is as follows: In the structural formula, R1 is H or C n H 2n+1 ; R2, R3 and R4 are C n H 2n+1 ; R5 is C n H 2n ; R6 and R7 are C n H 2n O; n is an integer, 1 ≤ n ≤ 4; The anion of the protonated amine-based ionic liquid is NO3 - , BF4 - , PF6 - , CF3COO - , CF3SO3 - (TfO - ), (CF3SO2)2N - (NTf2 - ), CH3SO3 - , HSO4 - , H2PO4 - , COO - , CH3COO - .

2. The method according to claim 1, wherein The protonated amine-based ionic liquid membrane comprises a protonated amine-based ionic liquid and a block polyether amide, wherein the mass of the protonated amine-based ionic liquid is 1%-180% of that of the block polyether amide.

3. The method according to claim 1, wherein When the protonated amine-based ionic liquid membrane is used for ammonia separation, the pressure is 0.01-5 MPa, the temperature is 10-120 °C, and ammonia directly permeates from one side of the membrane to the other.

4. The method according to claim 1, wherein The method for separating ammonia using the protonated amine-based ionic liquid membrane is applicable to the separation and recovery of ammonia in the tail gas generated during the production of ammonium molybdate, the purge gas from ammonia synthesis, the tail gas from chemical vapor deposition furnaces, the tail gas from urea production, the tail gas from ammonium nitrate production, coke oven gas, the tail gas from melamine production, and the tail gas from amino acid production.

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