A mixed matrix membrane for ammonia separation and a method of making the same

Abstract

This invention discloses a mixed matrix membrane for ammonia separation and its preparation method. A polyether-block polyamide (Pebax) rich in ether bonds and a liquid adsorbent are dissolved in a solvent, and the mixture is refluxed and stirred to obtain a casting solution. The casting solution is then coated onto a substrate, and the solvent is evaporated by heating to obtain the final mixed matrix membrane. Benefiting from the strong ammonia affinity of the Pebax polyether segments and the liquid adsorbent, the mixed matrix membrane obtained by this invention exhibits highly efficient ammonia separation. When separating residual gases from synthetic ammonia, its ammonia permeability can reach as high as 2656.9 Barrer, and its ammonia / nitrogen and ammonia / hydrogen selectivities can reach as high as 594.1 and 150.8, respectively.

Description

Technical Field

[0001] This invention relates to the field of new chemical materials technology, specifically to a mixed matrix membrane for ammonia separation and its preparation method. Background Technology

[0002] Ammonia plays a crucial role in the chemical industry, with important applications in agricultural fertilizers, pharmaceuticals, organic compounds, and polymer synthesis. Currently, the vast majority of ammonia is still produced using the traditional Haber-Bosch process, which involves the catalytic reaction of nitrogen and hydrogen under high temperature and pressure. It must be noted that the Haber-Bosch process has a low ammonia conversion rate of only 10-20%, and collection typically relies on physical cooling and liquefaction. However, approximately 3% of the ammonia remains in the recycle gas, reducing synthesis efficiency and impacting production capacity. Therefore, recovering low-concentration ammonia is essential.

[0003] Common ammonia separation methods include physical condensation, liquid absorption, solid adsorption, and membrane separation. Physical condensation requires cooling ammonia to its condensation point (typically around -33°C), resulting in high energy consumption and cost. Liquid absorption utilizes the higher solubility of ammonia hydrogen compared to hydrogen and nitrogen in liquid solvents to achieve ammonia separation. Water and inorganic acids were the earliest liquid adsorbents used. However, they suffer from drawbacks such as high volatility and thermal melting, high corrosiveness, and irreversible absorption. Ionic liquids and eutectic solvents are emerging liquid ammonia absorbents; ammonia absorption and separation processes based on these can reduce energy consumption, operating costs, and net carbon dioxide emissions to some extent. However, the high viscosity of ionic liquids and eutectic solvents makes their transport in reaction towers and pipelines difficult. Compared to liquid absorption, solid adsorption does not have the problems of volatility, viscosity, or corrosiveness. However, solid adsorption and liquid adsorption share a significant common problem: desorption is necessary after adsorption to obtain the ammonia product. The ammonia phase change in this process increases energy consumption, and polyurethane cannot be produced after the adsorbent reaches saturation, meaning that continuous ammonia separation cannot be achieved.

[0004] In recent years, membrane separation technology has been increasingly applied to the ammonia separation process in ammonia synthesis. Compared to absorption and adsorption methods, membrane separation does not involve phase changes in components, resulting in lower energy consumption. Furthermore, membrane separation offers advantages such as continuous production, process simplicity, and environmental friendliness. However, existing ammonia separation membranes suffer from low ammonia selectivity and low ammonia permeation flux. To date, developing ammonia separation membranes that combine high performance and low cost remains a significant technological challenge. Summary of the Invention

[0005] To address the problems of low ammonia selectivity and low ammonia permeation flux in existing ammonia separation membranes, this invention provides a mixed matrix membrane for ammonia separation and its preparation method. The mixed matrix membrane is prepared by blending a block polymer rich in ether bonds with a liquid adsorbent that has both high ammonia selective adsorption and high ammonia adsorption capacity, thereby providing a mixed matrix ammonia separation membrane with both high ammonia selective permeability and high ammonia permeation flux.

[0006] The present invention adopts the following technical solution:

[0007] A method for preparing a mixed matrix membrane for ammonia separation includes the following steps:

[0008] S1. Dissolve polyether block polyamide (Pebax) and liquid adsorbent in a solvent, reflux and stir to obtain casting solution;

[0009] S2. After cooling the casting solution to room temperature, coat the substrate with the film and then heat for 1-24 hours to obtain a mixed matrix film.

[0010] In step S1, the liquid adsorbent is selected from one of the following: ethylamine hydrochloride + phenol eutectic solvent (molar ratio 1:1-8), ethylamine hydrochloride + resorcinol eutectic solvent (molar ratio 1:0.5-2), ethylamine hydrochloride + phloroglucinol eutectic solvent (molar ratio 1:0.5-2), imidium hydrochloride + glycerol eutectic solvent (molar ratio 1:1-4), ethylamine hydrochloride + cobalt chloride + glycerol eutectic solvent (molar ratio 1:(0.2-1):3), ethanolamine hydrochloride + glycerol eutectic solvent (molar ratio 1:2-6), ethanolamine hydrochloride + phenol eutectic solvent (molar ratio 1:2-6), glycolic acid + phenol eutectic solvent (molar ratio 1:1-5), lithium-triethylene glycol chelate ionic liquid, and diethanolamine hydrochloride ionic liquid. The structural formulas of each liquid adsorbent are as follows: Figure 1 As shown;

[0011] In step S1, the mass ratio of polyether block polyamide to liquid adsorbent is 1:4 to 4:1.

[0012] In step S1, the solvent is an organic solvent that can dissolve both polyether block polyamide and liquid adsorbent.

[0013] Preferably, the solvent is one or a combination of N-methylpyrrolidone, N,N-dimethylformamide, dimethyl sulfoxide, and ethanol.

[0014] The reflux stirring time in step S1 is 1-24 hours.

[0015] The mass concentration of the casting solution in step S1 is 1%-20%.

[0016] In step S2, the heating temperature of the coating is 40-120℃.

[0017] A mixed matrix membrane for ammonia separation prepared according to the above preparation method.

[0018] The technical solution of this invention has the following advantages:

[0019] A. This invention uses a blend of Pebax and liquid adsorbents to prepare a hybrid matrix membrane. Pebax is a block polymer composed of polyethylene oxide (PEO) and polyamide (PA) segments. The former promotes selective ammonia permeation through interaction with ammonia gas, while the latter provides strong membrane-forming mechanical properties. The selected liquid adsorbents exhibit high ammonia selective adsorption and high ammonia adsorption capacity. Through the synergistic effect of Pebax and the liquid adsorbents, both high selectivity and high flux ammonia permeation are simultaneously promoted. The hybrid matrix membrane prepared according to the method of this invention, and ammonia separation via membrane separation, can achieve continuous, rapid, and low-energy-consumption ammonia separation.

[0020] B. The mixed matrix membrane obtained by the present invention has a high efficiency in ammonia separation. When separating residual gas from synthetic ammonia, its ammonia permeability is as high as 2656.9 Barrer, and its ammonia / nitrogen and ammonia / hydrogen selectivity are as high as 594.1 and 150.8, respectively.

[0021] C. The raw materials for preparing the mixed matrix membrane of the present invention are either commercially available or can be synthesized at low cost, thereby significantly reducing the cost of membrane preparation and facilitating its large-scale application. Attached Figure Description

[0022] Figure 1 The structural formulas of various liquid adsorbents are described below. Detailed Implementation

[0023] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1:

[0025] 1g Pebax, 0.25g ethylamine hydrochloride + phenol eutectic agent (mass ratio of Pebax to liquid adsorbent is 4:1) and 11.25g dimethyl sulfoxide were added to a single-necked flask. After reflux and stirring for 8 hours, a casting solution with a mass concentration of 10% was obtained. After cooling, the solution was coated onto a glass plate and heated at 120℃ for 12 hours to obtain a mixed matrix membrane.

[0026] A gas separation device was used to separate a mixture of ammonia, nitrogen, and hydrogen. The permeability of the three gases was tested, and the ammonia / nitrogen and ammonia / hydrogen selectivities were calculated. The results showed that the pure ammonia permeability of the mixed matrix membrane was 658.3 Barrer, and the ammonia / nitrogen and ammonia / hydrogen selectivities were 480.5 and 85.7, respectively.

[0027] Example 2:

[0028] Add 1g Pebax, 1g ethylamine hydrochloride + phenol eutectic agent (the mass ratio of Pebax to liquid adsorbent is 1:1) and 18g dimethyl sulfoxide to a single-necked flask, reflux and stir for 8 hours to obtain a casting solution with a mass concentration of 10%. After cooling, coat the solution onto a glass plate and heat at 120℃ for 24 hours to obtain a mixed matrix membrane.

[0029] A gas separation device was used to separate a mixture of ammonia, nitrogen, and hydrogen. The permeability of the three gases was tested, and the ammonia / nitrogen and ammonia / hydrogen selectivities were calculated. The results showed that the pure ammonia permeability of the mixed matrix membrane was 813.7 Barrer, and the ammonia / nitrogen and ammonia / hydrogen selectivities were 529.5 and 114.3, respectively.

[0030] Example 3:

[0031] 1g Pebax, 4g ethylamine hydrochloride + phenol eutectic agent (mass ratio of Pebax to liquid adsorbent is 1:4) and 45g dimethyl sulfoxide were added to a single-necked flask. After reflux and stirring for 8 hours, a casting solution with a mass concentration of 10% was obtained. After cooling, the solution was coated on a glass plate and heated at 120℃ for 24 hours to obtain a mixed matrix membrane.

[0032] A gas separation device was used to separate a mixture of ammonia, nitrogen, and hydrogen. The permeability of the three gases was tested, and the ammonia / nitrogen and ammonia / hydrogen selectivities were calculated. The results showed that the ammonia permeability of the mixed matrix membrane was 2656.9 Barrer, and the ammonia / nitrogen and ammonia / hydrogen selectivities were 594.1 and 150.8, respectively.

[0033] Comparative Example 1:

[0034] 1 g of Pebax and 9 g of dimethyl sulfoxide were added to a single-necked flask and stirred under reflux for 8 hours to obtain a casting solution with a mass concentration of 10%. After cooling, the solution was coated onto a glass plate and heated at 120°C for 24 hours to obtain a Pebax membrane.

[0035] A gas separation device was used to separate a mixture of ammonia, nitrogen, and hydrogen. The permeability of the three gases was tested, and the ammonia / nitrogen and ammonia / hydrogen selectivities were calculated. The results showed that the pure ammonia permeability of the Pebax membrane was 590.2 Barrer, and the ammonia / nitrogen and ammonia / hydrogen selectivities were 404.3 and 68.5, respectively, which are close to those reported in the literature. This is because the polyether units of Pebax have a strong affinity for polar gases and exhibit good polar gas separation performance. Ammonia is a strongly polar alkaline gas; therefore, the Pebax membrane possesses certain ammonia separation performance.

[0036] As can be seen from Examples 1-3 and Comparative Example 1, the addition of liquid adsorbent significantly improves the ammonia separation performance of the mixed matrix membrane. At the same time, with the increase of the amount of liquid adsorbent added, the ammonia permeability and ammonia selectivity of the mixed matrix membrane are simultaneously improved.

[0037] Example 4:

[0038] A mixed matrix membrane was prepared using a method similar to that in Example 3, except that the mass concentration of the casting solution was changed to 1%, and similar results were obtained.

[0039] Example 5:

[0040] A mixed matrix membrane was prepared using a method similar to that in Example 3, except that the mass concentration of the casting solution was changed to 20%, and similar results were obtained.

[0041] Example 6:

[0042] A mixed matrix membrane was prepared using a method similar to that in Example 3, except that the organic solvent was replaced with ethanol, the heating temperature of the casting solution was changed to 40°C, and the heating time was changed to 1 hour, and similar results were obtained.

[0043] Example 7:

[0044] A mixed matrix membrane was prepared using a method similar to that in Example 3, except that the organic solvent was changed to N-methylpyrrolidone, and similar results were obtained.

[0045] Example 8:

[0046] A mixed matrix membrane was prepared using a method similar to that in Example 3, except that the organic solvent was replaced with N,N dimethylformamide and the reflux stirring time was 24 h, yielding similar results.

[0047] Example 9:

[0048] A mixed matrix membrane was prepared using a method similar to that in Example 3, except that the organic solvent was replaced with N,N-dimethylacetamide and the reflux stirring time was 1 h, yielding similar results.

[0049] Example 10:

[0050] A mixed matrix membrane was prepared using a method similar to that in Example 3, except that the organic solvent was replaced with methanol, and similar results were obtained.

[0051] Example 11:

[0052] A mixed matrix membrane was prepared using a method similar to that in Example 3, except that the liquid adsorbent was replaced with ethylamine hydrochloride + resorcinol eutectic agent, and similar results were obtained.

[0053] Example 12:

[0054] A mixed matrix membrane was prepared using a method similar to that in Example 3, except that the liquid adsorbent was replaced with ethylamine hydrochloride + phloroglucinol eutectic agent, and similar results were obtained.

[0055] Example 13:

[0056] A mixed matrix membrane was prepared using a method similar to that in Example 3, except that the liquid adsorbent was replaced with imidimid hydrochloride + glycerol eutectic agent, and similar results were obtained.

[0057] Example 14:

[0058] A mixed matrix membrane was prepared using a method similar to that in Example 3, except that the liquid adsorbent was replaced with an ethylamine hydrochloride + cobalt chloride + glycerol eutectic solvent, and similar results were obtained.

[0059] Example 15:

[0060] A mixed matrix membrane was prepared using a method similar to that in Example 3, except that the liquid adsorbent was replaced with ethanolamine hydrochloride + glycerol eutectic solvent, and similar results were obtained.

[0061] Example 16:

[0062] A mixed matrix membrane was prepared using a method similar to that in Example 3, except that the liquid adsorbent was replaced with ethanolamine hydrochloride + phenol eutectic solvent, and similar results were obtained.

[0063] Example 17:

[0064] A mixed matrix membrane was prepared using a method similar to that in Example 3, except that the liquid adsorbent was replaced with a eutectic solvent of glycolic acid and phenol, and similar results were obtained.

[0065] Example 18:

[0066] A mixed matrix membrane was prepared using a method similar to that in Example 3, except that the liquid adsorbent was replaced with a lithium-triethylene glycol chelate ionic liquid, and similar results were obtained.

[0067] Example 19:

[0068] A mixed matrix membrane was prepared using a method similar to that in Example 3, except that the liquid adsorbent was replaced with diethanolamine hydrochloride ionic liquid, and similar results were obtained.

[0069] In summary, this invention uses a blend of Pebax and liquid adsorbents to prepare a hybrid matrix membrane. Pebax is a block polymer composed of polyethylene oxide (PEO) and polyamide (PA) segments. The former promotes selective ammonia permeation through interaction with ammonia gas, while the latter provides strong membrane-forming mechanical properties. The selected liquid adsorbents exhibit high ammonia selective adsorption and high ammonia adsorption capacity. Through the synergistic effect of Pebax and liquid adsorbents, both high selectivity and high flux permeation of ammonia gas are simultaneously promoted. The hybrid matrix membrane prepared according to the method of this invention, and ammonia separation via membrane separation, can achieve continuous, rapid, and low-energy-consumption ammonia separation.

[0070] The hybrid matrix membrane obtained by this invention has a high efficiency in ammonia separation. When separating residual gas from synthetic ammonia, its ammonia permeability can reach up to 2656.9 Barrer, and its ammonia / nitrogen and ammonia / hydrogen selectivity can reach up to 594.1 and 150.8, respectively.

[0071] The raw materials for preparing the mixed matrix membrane of this invention are either commercially available or can be synthesized at low cost, thereby significantly reducing the cost of membrane preparation and facilitating its large-scale application.

[0072] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a mixed matrix membrane for ammonia separation, characterized in that, Includes the following steps: S1. Dissolve polyether block polyamide and liquid adsorbent in a solvent, reflux and stir to obtain casting solution; S2. After cooling the casting solution to room temperature, coat the substrate with the film, and then heat for 1-24 hours to obtain a mixed matrix film. In step S1, the liquid adsorbent is selected from one of the following: ethylamine hydrochloride + phenol eutectic solvent, ethylamine hydrochloride + resorcinol eutectic solvent, ethylamine hydrochloride + phloroglucinol eutectic solvent, imidium hydrochloride + glycerol eutectic solvent, ethylamine hydrochloride + cobalt chloride + glycerol eutectic solvent, ethanolamine hydrochloride + glycerol eutectic solvent, ethanolamine hydrochloride + phenol eutectic solvent, and glycolic acid + phenol eutectic solvent. In step S1, the mass ratio of polyether block polyamide to liquid adsorbent is 1:4-4:

1.

2. The preparation method according to claim 1, characterized in that: In step S1, the solvent is an organic solvent that can dissolve both polyether block polyamide and liquid adsorbent.

3. The preparation method according to claim 2, characterized in that: The solvent is one or more combinations of N-methylpyrrolidone, N,N-dimethylformamide, dimethyl sulfoxide, and ethanol.

4. The preparation method according to claim 1, characterized in that: The reflux stirring time in step S1 is 1-24 hours.

5. The preparation method according to claim 1, characterized in that: The mass concentration of the casting solution in step S1 is 1%-20%.

6. The preparation method according to claim 1, characterized in that: In step S2, the heating temperature of the coating is 40-120℃.

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