Zinc zeolite imidazole molecular sieve hollow membrane as well as preparation method and application thereof

Abstract

The invention relates to the technical field of nano-membranes, in particular to a zinc zeolite imidazole molecular sieve hollow membrane and a preparation method and application thereof.The hollow membrane is made of polytetrafluoroethylene and filled with a zinc zeolite imidazole molecular sieve nano-layer obtained through a liquid phase interface synthesis method, the zinc zeolite imidazole molecular sieve nano layer is synthesized by taking 2-methylimidazole as an organic ligand and zinc acetate as a metal ion source; the zinc zeolite imidazole molecular sieve nano-layer is synthesized by a liquid phase interface method, and the aperture of the zinc zeolite imidazole molecular sieve nano-layer is accurately regulated and controlled to be 0.30-0.37 nm. Hydrogen sulfide molecules can pass through and methane molecules are intercepted, so that methane desulfurization is completed. According to the method, hydrogen sulfide molecules are separated from the biogas through physical action, durability can be achieved, frequent replacement is not needed, and therefore the use cost is greatly reduced.

Description

Technical Field

[0001] The invention relates to the technical field of nano-membranes, and in particular to a zinc zeolite imidazole molecular sieve hollow membrane and a preparation method and application thereof. Background Art

[0002] Biogas refers to a mixed gas produced by the decomposition of organic matter (such as plant residues, animal feces, garbage, etc.) by microorganisms in an anaerobic environment. This process usually occurs in composting, landfills, animal farms, etc. The specific process includes the hydrolysis of complex organic matter, bacterial fermentation, and methanogen gas production. Biogas is mainly composed of methane (CH4) and carbon dioxide (CO2), and also contains small amounts of nitrogen (N2), hydrogen sulfide (H2S), and water vapor. CH4: about 50-70%, is the main component of biogas and the main available fuel for biogas. CO2: about 30-50%, together with methane, constitutes biogas. N2, H2S and water vapor: The content of these components is usually very low, but the presence of H2S requires special attention because it is corrosive and toxic. It is known that the diameter of a CH4 molecule is 0.38nm and the diameter of an H2S molecule is 0.29nm.

[0003] The following methods are commonly used in the prior art to remove hydrogen sulfide (H2S) from biogas:

[0004] Chemical absorption method: using monoethanolamine, Mektosulfurization amine and other absorbents to react with H2S to form soluble compounds, and then remove H2S by heating. This operation method is more complicated and has higher material costs.

[0005] Physical adsorption method: The adsorption method is to remove H2S from biogas through solid adsorbents. Commonly used adsorbents include activated carbon, molecular sieves, aluminum sulfide, etc. These adsorbents have a large specific surface area and adsorption capacity, and can remove sulfides from the gas at room temperature. These methods are suitable for the desulfurization of low-sulfur biogas, and need to be operated at low temperatures to improve efficiency. The adsorbents need to be replaced regularly, which makes them expensive.

[0006] Biodesulfurization: Biodesulfurization uses the metabolism of microorganisms to convert H2S into harmless substances (such as sulfur). This method is environmentally friendly, but it is suitable for gases with low H2S concentrations and has a slow reaction rate. It can only be used for small-scale biogas purification and is difficult to use in industrial production.

[0007] Oxidation method: In some cases, H2S can be converted into elemental sulfur or SO2 through oxidation reaction. This method is rarely used alone, but can be used in conjunction with other desulfurization technologies.

[0008] Membrane separation method: The membrane separation method uses a selective permeable membrane to separate H2S from natural gas. The use of specific membrane materials allows hydrogen sulfide to pass through the membrane layer while CH4 is blocked. This method is energy-efficient and efficient, but the equipment cost is high and it is suitable for natural gas with a high sulfur content.

[0009] In order to solve the above problems, the present invention proposes a zinc zeolite imidazole molecular sieve hollow membrane and a preparation method and application thereof. Summary of the invention

[0010] To achieve the above-mentioned purpose, the present invention provides a zinc zeolite imidazole molecular sieve hollow membrane, which is made of polytetrafluoroethylene and filled with a zinc zeolite imidazole molecular sieve nanolayer obtained by a liquid phase interface synthesis method, wherein the zinc zeolite imidazole molecular sieve nanolayer is synthesized with 2-methylimidazole as an organic ligand and zinc acetate as a metal node.

[0011] Optionally, the pore size of the sieve pores of the zinc zeolite imidazole molecular sieve nanolayer is between 0.30-0.37 nm.

[0012] To achieve the above object, the present invention also provides a method for preparing the zinc zeolite imidazole molecular sieve hollow membrane, which comprises the following steps:

[0013] a. Prepare an organic ligand solution by dissolving 2-methylimidazole in ethanol at a concentration of 0.01 to 0.1 M;

[0014] b. Prepare a metallic zinc ion solution by dissolving zinc acetate in high-purity water to a concentration of 0.01 to 0.05 M;

[0015] c. Prepare a liquid phase interface for reaction: pour 250 mL of zinc acetate solution into a 1 L glass container, and slowly pour 250 mL of oil phase along the wall of the glass tube at a relatively low temperature to form an oil-water interface;

[0016] d. Slowly drop an ethanol solution of 2-methylimidazole into a glass container at a dropping speed of 0.5 to 5 mL / min, so that it diffuses from the upper oil phase to the oil-water interface and contacts with zinc acetate in the lower water phase to form a zinc zeolite imidazole molecular sieve nanolayer;

[0017] e. After standing for 5 to 10 hours, the precipitate synthesized at the interface is collected, centrifuged, washed and dried to obtain a zinc zeolite imidazole molecular sieve nanolayer;

[0018] f. Filling and compressing the obtained zinc zeolite imidazole molecular sieve nanolayer into the pores of the polytetrafluoroethylene hollow fiber membrane.

[0019] Optionally, the rotation speed of the centrifugal washing is 10000-15000 rpm, and the time is 5-10 min.

[0020] Optionally, the oil phase is one of cyclohexane, n-heptane or isooctane.

[0021] To achieve the above object, the present invention also provides a biogas desulfurization method using the zinc zeolite imidazole molecular sieve hollow membrane, comprising the following steps:

[0022] a. Pressurizing the biogas and passing it through a zinc zeolite imidazole molecular sieve hollow membrane;

[0023] b. Through the selective permeation function of the zinc zeolite imidazole molecular sieve nanolayer, hydrogen sulfide molecules are allowed to pass through while methane molecules are intercepted;

[0024] c. Passing the separated hydrogen sulfide molecules into lime water for tail gas treatment;

[0025] d. Collect the desulfurized biogas.

[0026] To achieve the above object, the present invention also provides a biogas desulfurization device using the zinc zeolite imidazole molecular sieve hollow membrane, comprising:

[0027] A biogas desulfurization module equipped with a zinc zeolite imidazole molecular sieve hollow membrane;

[0028] A pressurizing system, used for pressurizing the biogas;

[0029] a branch port for separating hydrogen sulfide from biogas passing through the zinc zeolite imidazole molecular sieve hollow membrane;

[0030] A main port for outputting desulfurized biogas;

[0031] A shell, with the branch port and the main port respectively arranged at two opposite ends, the biogas desulfurization module is arranged inside the shell, and the pressurization system is arranged outside the shell.

[0032] Optionally, the biogas desulfurization device further includes a lime water storage module, which is disposed outside the housing and is interconnected with the outlet end of the branch port for treating the tail gas.

[0033] To achieve the above object, the present invention also provides a desulfurization cloth containing the zinc zeolite imidazole molecular sieve hollow membrane, wherein the desulfurization cloth comprises a fiber cloth and a zinc zeolite imidazole molecular sieve hollow membrane disposed on the outer surface of the fiber cloth.

[0034] To achieve the above object, the present invention also provides a method for using the desulfurization cloth, which includes surrounding or covering the biogas with the desulfurization cloth, or arranging the desulfurization cloth in a pipeline for biogas to pass through.

[0035] The beneficial effects of the present invention are as follows:

[0036] The present invention synthesizes a zinc zeolite imidazole molecular sieve nanolayer by a liquid phase interface method, and accurately controls its pore size to be 0.30-0.37 nm. Hydrogen sulfide molecules can pass through while methane molecules are intercepted, thereby completing biogas desulfurization. The method separates hydrogen sulfide molecules from biogas by physical action, can be durable, does not need to be frequently replaced, and thus greatly reduces the cost of use. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be the usual meanings understood by people with general skills in the field to which the present invention belongs. "Including" and similar words used in this article mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0038] In view of the problems existing in the prior art, an embodiment of the present invention provides a zinc zeolite imidazole molecular sieve hollow membrane, which is made of polytetrafluoroethylene and filled with a zinc zeolite imidazole molecular sieve nanolayer obtained by a liquid phase interface synthesis method, wherein the zinc zeolite imidazole molecular sieve nanolayer is synthesized with 2-methylimidazole as an organic ligand and zinc acetate as a metal node.

[0039] In one embodiment, the pore size of the sieve of the zinc zeolite imidazole molecular sieve nanolayer is between 0.30-0.37 nm. It is known that the diameter of a methane molecule is 0.38 nm and the diameter of a hydrogen sulfide molecule is 0.29 nm. In this embodiment, the pore size of the sieve of the zinc zeolite imidazole molecular sieve nanolayer is set to 0.30-0.37 nm, so that when biogas passes through, hydrogen sulfide molecules are allowed to pass through and methane molecules are retained.

[0040] In view of the problems existing in the prior art, an embodiment of the present invention further provides a method for preparing the zinc zeolite imidazole molecular sieve hollow membrane, the method comprising the following steps:

[0041] a. Prepare an organic ligand solution by dissolving 2-methylimidazole in ethanol at a concentration of 0.01 to 0.1 M;

[0042] In one example, the target organic ligand solution concentration is 0.01 M; the target volume is 1 L. In order to achieve the above target concentration and target volume, the specific operation process is as follows:

[0043] Use a balance to accurately weigh 1.642g of 2-methylimidazole; add the weighed 1.642g of 2-methylimidazole to a beaker; add 50mL of ethanol to the beaker; use a glass rod to stir the mixture in the beaker until the 2-methylimidazole is completely dissolved. During this process, you can heat it slightly to speed up the dissolution process, but be careful to control the temperature to avoid excessive ethanol volatilization; transfer the completely dissolved solution from the beaker to a 1000mL volumetric flask; continue to add ethanol to the volumetric flask until the volume of the solution reaches the 1000mL mark; cover the stopper of the volumetric flask, shake it upside down or use a shaker to ensure that the solution is fully mixed to obtain the required organic ligand solution.

[0044] b. Prepare a metallic zinc ion solution by dissolving zinc acetate in high-purity water to a concentration of 0.01 to 0.05 M;

[0045] In one example, the target concentration is 0.02 M; the target volume is 1 L. In order to achieve the above target concentration and target volume, the specific operation process is as follows:

[0046] Use a balance to accurately weigh 3.39 g of zinc acetate; add the weighed 3.39 g of zinc acetate to a beaker; add a small amount of high-purity water to the beaker; use a glass rod to stir the mixture in the beaker until the zinc acetate is completely dissolved. In this step, you can heat it slightly to speed up the dissolution process, but pay attention to controlling the temperature to avoid excessive evaporation of water; transfer the completely dissolved solution from the beaker to a 1000 mL volumetric flask; continue to add high-purity water to the volumetric flask until the volume of the solution reaches the 1000 mL mark; cover the stopper of the volumetric flask, shake it upside down or use a bottle shaker to ensure that the solution is fully mixed and uniform to obtain the required metal zinc ion solution.

[0047] c. Prepare a liquid phase interface for reaction: pour 250 mL of zinc acetate solution into a 1 L glass container, and slowly pour 250 mL of oil phase along the wall of the glass tube at a relatively low temperature to form an oil-water interface;

[0048] Specifically, carefully pour 250 mL of the cooled zinc acetate solution into a 1 L glass container. Make sure not to generate excessive foam or splashing when pouring; cool 250 mL of the oil phase (cyclohexane, n-heptane or isooctane) to the same temperature as the zinc acetate solution to reduce mixing caused by the temperature difference; use a glass tube or a long-necked funnel to pour 250 mL of the oil phase very slowly along the inner wall of the glass container. The purpose of this is to avoid mixing of the oil phase and the water phase, thereby forming a clear oil-water interface;

[0049] d. Slowly drop an ethanol solution of 2-methylimidazole into a glass container at a dropping speed of 0.5 to 5 mL / min, so that it diffuses from the upper oil phase to the oil-water interface and contacts with zinc acetate in the lower water phase to form a zinc zeolite imidazole molecular sieve nanolayer;

[0050] The setting of this step can achieve the following beneficial effects: precise control of pore size: by precisely controlling the reaction of 2-methylimidazole and zinc acetate at the oil-water interface, a zinc zeolite imidazole molecular sieve with a specific pore size (such as 0.30-0.37nm in the present invention) can be synthesized; improve selectivity: a zinc zeolite imidazole molecular sieve with a specific pore size can provide selectivity for a specific molecular size, which is particularly effective for separating gas molecules with similar molecular sizes (such as CH and HS). Specifically, the oil phase (usually an organic solvent) and the water phase (a solution containing zinc acetate) are immiscible, which helps to form a clear interface between the two phases; 2-methylimidazole diffuses from the oil phase to the oil-water interface and then reacts with zinc acetate in the water phase. The control of the droplet acceleration ensures the slow and uniform diffusion of 2-methylimidazole; at the oil-water interface, 2-methylimidazole and zinc acetate react to form a nanolayer of zinc zeolite imidazole molecular sieve. This interface provides a confined space that helps control the growth and morphology of zinc zeolite imidazole molecular sieve crystals; zinc zeolite imidazole molecular sieve crystals grow on the interface to form a nanolayer with a specific pore size. The size of the pore size can be controlled by adjusting the synthesis conditions (such as the concentration of 2-methylimidazole and zinc acetate, reaction time and temperature); the formed zinc zeolite imidazole molecular sieve nanolayer has a regular pore structure and can act as a molecular sieve to selectively adsorb or separate molecules according to their size.

[0051] e. After standing for 5 to 10 hours, the precipitate synthesized at the interface is collected, centrifuged, washed and dried to obtain a zinc zeolite imidazole molecular sieve nanolayer;

[0052] In this step, by standing, unreacted raw materials and by-products can be separated from the formed zinc zeolite imidazole molecular sieve nanolayer, which is convenient for subsequent collection and purification; during the standing period, the zinc zeolite imidazole molecular sieve nanolayer can be further crystallized and stabilized, and its structural integrity is enhanced; after standing, the precipitate settles to the bottom of the container, which is convenient for collection and subsequent treatment. Specifically, during the standing process, due to the action of gravity, the heavier zinc zeolite imidazole molecular sieve nanolayer precipitate will gradually settle to the bottom of the container; as the reaction proceeds, the zinc zeolite imidazole molecular sieve nanolayer is formed and gradually separated from the oil-water interface to form a visible precipitate; during the standing period, the zinc zeolite imidazole molecular sieve crystals have enough time to grow and crystallize to form a more uniform and stable structure; centrifugal force can accelerate the separation of precipitates, improve purification efficiency, and remove suspended particles in the supernatant; by washing, unreacted raw materials and by-products attached to the zinc zeolite imidazole molecular sieve nanolayer can be removed; the drying step removes solvent and moisture, so that the zinc zeolite imidazole molecular sieve nanolayer is solidified, which is convenient for subsequent application and storage.

[0053] f. Filling and compressing the obtained zinc zeolite imidazole molecular sieve nanolayer into the pores of the polytetrafluoroethylene hollow fiber membrane.

[0054] The setting of this step has the following beneficial effects: precise molecular sieving: the pore size of zinc zeolite imidazole molecular sieve is controlled in the range of 0.30-0.37nm, which can effectively separate molecules of specific sizes, such as methane (CH4, about 0.38nm) and hydrosulfide (H2S, about 0.29nm); improving the selectivity of the membrane: by precisely controlling the pore size, the selectivity of the membrane for specific gas molecules can be improved, which is crucial for gas purification and separation; enhancing the durability of the membrane: the filling of zinc zeolite imidazole molecular sieve can enhance the chemical stability and mechanical strength of the PTFE membrane and extend the service life of the membrane.

[0055] This step specifically includes the following: synthesizing a zinc zeolite imidazole molecular sieve nanolayer to ensure that its pore size is within the range of 0.30-0.37nm; selecting a polytetrafluoroethylene (PTFE) hollow fiber membrane with a pore size slightly larger than the pore size of the zinc zeolite imidazole molecular sieve to ensure that the zinc zeolite imidazole molecular sieve nanolayer can be filled into the pores. For example, if the pore size of the zinc zeolite imidazole molecular sieve is 0.34nm, a PTFE membrane with a pore size of 0.5μm may be selected; using pressure or vacuuming to fill the zinc zeolite imidazole molecular sieve nanolayer into the pores of the PTFE membrane. The filling pressure needs to reach 3-5 atmospheres to ensure that the zinc zeolite imidazole molecular sieve nanolayer is completely filled into the pores; applying a certain pressure (for example, 0.5-1MPa) to compress the zinc zeolite imidazole molecular sieve nanolayer so that it fits tightly to the inner wall of the pore to form a uniform nanolayer; curing the filled and compressed zinc zeolite imidazole molecular sieve nanolayer to ensure its stability in the pores. This can be achieved by heat treatment (e.g., temperature control at 100-200°C) or chemical cross-linking; the filled and compressed hollow fiber membrane is cleaned, dried and performance tested to ensure that its separation performance meets expectations.

[0056] In one embodiment, the rotation speed of the centrifugal washing is 10000-15000 rpm, and the time is 5-10 min.

[0057] The setting of this step allows the zinc zeolite imidazole molecular sieve particles to quickly settle to the bottom of the container under high-speed centrifugation, thereby achieving rapid separation of solids and liquids. For example, using a centrifugal speed of 15,000 rpm, more than 90% of solid sedimentation can be achieved within a few minutes; the setting of this step can avoid damage to the nanolayer structure of the zinc zeolite imidazole molecular sieve and maintain its integrity. Experimental data show that at a centrifugal speed of 10,000 to 15,000 rpm, the crystal structure of the zinc zeolite imidazole molecular sieve remains intact.

[0058] In one embodiment, the oil phase is one of cyclohexane, n-heptane or isooctane. These oil phases are immiscible with water and help form a clear oil-water interface.

[0059] In view of the problems existing in the prior art, an embodiment of the present invention further provides a biogas desulfurization method using the zinc zeolite imidazole molecular sieve hollow membrane, comprising the following steps:

[0060] a. Pressurizing the biogas and passing it through a zinc zeolite imidazole molecular sieve hollow membrane;

[0061] b. Through the selective permeation function of the zinc zeolite imidazole molecular sieve nanolayer, hydrogen sulfide molecules are allowed to pass through while methane molecules are intercepted;

[0062] c. Passing the separated hydrogen sulfide molecules into lime water for tail gas treatment;

[0063] d. Collect the desulfurized biogas.

[0064] In view of the problems existing in the prior art, an embodiment of the present invention further provides a biogas desulfurization device using the zinc zeolite imidazole molecular sieve hollow membrane, comprising:

[0065] A biogas desulfurization module equipped with a zinc zeolite imidazole molecular sieve hollow membrane;

[0066] A pressurizing system, used for pressurizing the biogas;

[0067] a branch port for separating hydrogen sulfide from biogas passing through the zinc zeolite imidazole molecular sieve hollow membrane;

[0068] A main port for outputting desulfurized biogas;

[0069] A shell has the branch port and the main port respectively disposed at two opposite ends, the biogas desulfurization module is disposed inside the shell, and the pressurizing system is disposed outside the shell.

[0070] The beneficial effects of this embodiment are as follows: the desulfurization module is integrated in a shell, making the entire device more compact and easy to install and operate; the pressurization system is arranged outside the shell, which is convenient for operators to control and maintain, while reducing the space occupied in the shell; compared with traditional desulfurization technology, the zinc zeolite imidazole molecular sieve hollow membrane desulfurization device has lower operation and maintenance costs; the modular design of the desulfurization device makes monitoring and maintenance more convenient; at the same time, the pressurization system can be adjusted according to changes in biogas flow and hydrogen sulfide concentration to adapt to different operating conditions.

[0071] In one embodiment, the biogas desulfurization device further includes a lime water storage module, which is arranged outside the shell and is interconnected with the outlet end of the branch port for treating the tail gas. The beneficial effects of this embodiment are: lime water (calcium hydroxide solution) is a commonly used acidic gas neutralizer, which can effectively react with hydrogen sulfide (H2S) to generate calcium sulfide precipitate (CaS) and water, thereby removing H2S from the tail gas; integrating the lime water storage module into the desulfurization device can simplify the tail gas treatment process and reduce additional equipment and operating steps; it can timely treat the H2S released during the desulfurization process and reduce its harm to the environment and human health; the integrated lime water storage module facilitates monitoring of the H2S treatment efficiency and lime water consumption to achieve process control.

[0072] In view of the problems existing in the prior art, an embodiment of the present invention further provides a desulfurization cloth containing the zinc zeolite imidazole molecular sieve hollow membrane. The desulfurization cloth comprises a fiber cloth and a zinc zeolite imidazole molecular sieve hollow membrane arranged on the outer surface of the fiber cloth.

[0073] The beneficial effects of this embodiment are as follows: the zinc zeolite imidazole molecular sieve hollow membrane is arranged on the outer surface of the fiber cloth, and the mechanical strength of the fiber cloth can be utilized to enhance the structural stability of the entire desulfurization cloth; the chemical corrosion resistance of the zinc zeolite imidazole molecular sieve hollow membrane enables the desulfurization cloth to maintain its performance even in harsh chemical environments and extend its service life; the form of the desulfurization cloth is easy to integrate into the existing gas treatment system without large-scale modification; compared with traditional desulfurization methods, the zinc zeolite imidazole molecular sieve hollow membrane desulfurization cloth may have lower operating and maintenance costs.

[0074] In view of the problems existing in the prior art, an embodiment of the present invention further provides a method for using the desulfurization cloth as described above, which includes surrounding or covering the biogas with the desulfurization cloth, or arranging the desulfurization cloth in a pipeline to allow the biogas to pass through.

[0075] The beneficial effects of this embodiment are as follows: the desulfurization cloth is in direct contact with the biogas, which can quickly and effectively remove hydrogen sulfide (H2S) and improve the desulfurization efficiency; the desulfurization cloth is easy to install and deploy, and no complicated equipment changes are required whether it surrounds or covers the outside of the biogas or is placed in the pipeline; the desulfurization cloth can be customized according to the specific layout and needs of the biogas treatment facility, providing a flexible solution; compared with traditional desulfurization technology, the use of desulfurization cloth reduces equipment and operating costs, especially in terms of maintenance and replacement.

[0076] The zinc zeolite imidazole molecular sieve hollow membrane of the present invention and its preparation method and application are described in detail below through specific embodiments:

[0077] Example 1

[0078] Preparation of zinc zeolite imidazole molecular sieve nanolayer with pore size of 0.30 nm

[0079] The specific steps are as follows:

[0080] Step 1: Prepare stock solution

[0081] 1. Prepare 2-methylimidazole (2-methylimidazole) ethanol solution:

[0082] Accurately weigh 1.642 g of 2-methylimidazole with a purity higher than 99%.

[0083] 2-Methylimidazole was slowly added to 1000 mL of analytical pure ethanol measured in advance, and stirred at room temperature using a magnetic stirrer until it was completely dissolved to obtain a 0.01 M 2-methylimidazole ethanol solution.

[0084] 2. Prepare zinc acetate aqueous solution:

[0085] Accurately weigh an appropriate amount of zinc acetate and calculate the mass of zinc acetate required based on a concentration of 0.02 M. For 1 L of solution, the mass of zinc acetate required is 0.02 mol / L × 169.5 g / mol × 1 L = 3.39 g.

[0086] 3.39 g of zinc acetate was dissolved in high-purity water and stirred at room temperature using a magnetic stirrer until the solution was completely dissolved to obtain a 0.02 M zinc acetate aqueous solution.

[0087] Step 2: Set up reaction conditions

[0088] 1. Dropping speed control:

[0089] Slowly add 0.01M 2-methylimidazole ethanol solution to 0.02M zinc acetate aqueous solution at a rate of 0.5mL / min. This step requires precise control to ensure that the molar ratio of 2-methylimidazole to Zn2+ is 1:1 and the reaction can proceed evenly at the oil-water interface.

[0090] Step 3: Perform the reaction

[0091] 1. Room temperature reaction:

[0092] At room temperature of 25°C, continue to drop 2-methylimidazole ethanol solution until it is completely added, and the total reaction time is 10 hours. During this period, 2-methylimidazole and Zn2+ undergo coordination reaction at the oil-water interface to form a zinc zeolite imidazole molecular sieve nanolayer. During the reaction, the reaction system should be avoided from being disturbed to ensure the uniform growth of the zinc zeolite imidazole molecular sieve nanolayer.

[0093] Step 4: Post-processing

[0094] 1. Settle and precipitate:

[0095] After the reaction is complete, the mixture is allowed to stand for 5 hours to allow the zinc zeolite imidazole molecular sieve nanolayer to precipitate. This step allows unreacted raw materials and byproducts to be separated from the zinc zeolite imidazole molecular sieve nanolayer.

[0096] 2. Collect the sediment:

[0097] The precipitated zinc zeolite imidazole molecular sieve nanolayer is collected by filtering or centrifuging. During the centrifugation, the centrifugation speed is 10000 rpm and the centrifugation time is 5 minutes.

[0098] 3. Washing and drying:

[0099] The collected zinc zeolite imidazole molecular sieve nanolayer is washed with ethanol or deionized water for multiple times to remove the residual unreacted raw materials and by-products. After washing, the excess water is removed using a vacuum filtration device.

[0100] The washed zinc zeolite imidazolate molecular sieve nanolayer was placed in an oven and dried at 60° C. for 12 h to ensure complete removal of moisture.

[0101] The zinc zeolite imidazole molecular sieve nanolayer with a pore size of 0.30 nm can be synthesized through the above steps.

[0102] Example 2

[0103] Preparation of zinc zeolite imidazole molecular sieve nanolayer with pore size of 0.34 nm

[0104] The specific steps are as follows:

[0105] Step 1: Prepare stock solution

[0106] 1. Prepare 2-methylimidazole (2-methylimidazole) ethanol solution:

[0107] Accurately weigh 2.463 g of 2-methylimidazole with a purity higher than 99%.

[0108] 2-Methylimidazole was slowly added to 1000 mL of analytical pure ethanol measured in advance, and stirred at room temperature using a magnetic stirrer until completely dissolved to obtain a 0.02 M 2-methylimidazole ethanol solution.

[0109] 2. Prepare zinc acetate aqueous solution:

[0110] Accurately weigh an appropriate amount of zinc acetate and calculate the mass of zinc acetate required based on a concentration of 0.03 M. For 1 L of solution, the mass of zinc acetate required is 0.03 mol / L × 169.5 g / mol × 1 L = 5.085 g.

[0111] 5.085 g of zinc acetate was dissolved in high-purity water and stirred at room temperature using a magnetic stirrer until the solution was completely dissolved to obtain a 0.02 M zinc acetate aqueous solution.

[0112] Step 2: Set up reaction conditions

[0113] 1. Dropping speed control:

[0114] Slowly add 0.02M 2-methylimidazole ethanol solution to 0.03M zinc acetate aqueous solution at a rate of 1mL / min. This step requires precise control to ensure that the molar ratio of 2-methylimidazole to Zn2+ is 1:1 and the reaction can proceed evenly at the oil-water interface.

[0115] Step 3: Perform the reaction

[0116] 1. Room temperature reaction:

[0117] At room temperature of 25°C, continue to drop 2-methylimidazole ethanol solution until it is completely added, and the total reaction time is 12 hours. During this period, 2-methylimidazole and Zn2+ undergo coordination reaction at the oil-water interface to form a zinc zeolite imidazole molecular sieve nanolayer. During the reaction, the reaction system should be avoided from being disturbed to ensure the uniform growth of the zinc zeolite imidazole molecular sieve nanolayer.

[0118] Step 4: Post-processing

[0119] 1. Settle and precipitate:

[0120] After the reaction is complete, the mixture is allowed to stand for 6 hours to allow the zinc zeolite imidazole molecular sieve nanolayer to precipitate. This step allows unreacted raw materials and byproducts to be separated from the zinc zeolite imidazole molecular sieve nanolayer.

[0121] 2. Collect the sediment:

[0122] The precipitated zinc zeolite imidazole molecular sieve nanolayer is collected by filtering or centrifuging. During the centrifugation, the centrifugation speed is 12000 rpm and the centrifugation time is 8 minutes.

[0123] 3. Washing and drying:

[0124] The collected zinc zeolite imidazole molecular sieve nanolayer is washed with ethanol or deionized water for multiple times to remove the residual unreacted raw materials and by-products. After washing, the excess water is removed using a vacuum filtration device.

[0125] The washed zinc zeolite imidazolate molecular sieve nanolayer was placed in an oven and dried at 60° C. for 12 h to ensure complete removal of moisture.

[0126] The zinc zeolite imidazole molecular sieve nanolayer with a pore size of 0.34 nm can be synthesized through the above steps.

[0127] Example 3

[0128] Preparation of zinc zeolite imidazole molecular sieve nanolayer with pore size of 0.38 nm

[0129] The specific steps are as follows:

[0130] Step 1: Prepare stock solution

[0131] 1. Prepare 2-methylimidazole (2-methylimidazole) ethanol solution:

[0132] Accurately weigh 3.284 g of 2-methylimidazole with a purity higher than 99%.

[0133] 2-Methylimidazole was slowly added to 1000 mL of analytical pure ethanol measured in advance, and stirred at room temperature using a magnetic stirrer until completely dissolved to obtain a 0.03 M 2-methylimidazole ethanol solution.

[0134] 2. Prepare zinc acetate aqueous solution:

[0135] Accurately weigh an appropriate amount of zinc acetate and calculate the mass of zinc acetate required based on a concentration of 0.04 M. For 1 L of solution, the mass of zinc acetate required is 0.04 mol / L × 169.5 g / mol × 1 L = 6.78 g.

[0136] 6.78 g of zinc acetate was dissolved in high-purity water and stirred at room temperature using a magnetic stirrer until the solution was completely dissolved to obtain a 0.04 M zinc acetate aqueous solution.

[0137] Step 2: Set up reaction conditions

[0138] 1. Dropping speed control:

[0139] Slowly add 0.03M 2-methylimidazole ethanol solution to 0.04M zinc acetate aqueous solution at a rate of 1.5mL / min. This step requires precise control to ensure that the molar ratio of 2-methylimidazole to Zn2+ is 1:1 and the reaction can proceed evenly at the oil-water interface.

[0140] Step 3: Perform the reaction

[0141] 1. Room temperature reaction:

[0142] At room temperature of 25°C, continue to drop 2-methylimidazole ethanol solution until it is completely added, and the total reaction time is 15 hours. During this period, 2-methylimidazole and Zn2+ react at the oil-water interface to form a zinc zeolite imidazole molecular sieve nanolayer. During the reaction, the reaction system should be avoided from being disturbed to ensure the uniform growth of the zinc zeolite imidazole molecular sieve nanolayer.

[0143] Step 4: Post-processing

[0144] 1. Settle and precipitate:

[0145] After the reaction is complete, the mixture is allowed to stand for 8 hours to allow the zinc zeolite imidazole molecular sieve nanolayer to precipitate. This step allows unreacted raw materials and byproducts to be separated from the zinc zeolite imidazole molecular sieve nanolayer.

[0146] 2. Collect the sediment:

[0147] The precipitated zinc zeolite imidazole molecular sieve nanolayer is collected by filtering or centrifuging. During the centrifugation, the centrifugation speed is 15000 rpm and the centrifugation time is 10 min.

[0148] 3. Washing and drying:

[0149] The collected zinc zeolite imidazole molecular sieve nanolayer is washed with ethanol or deionized water for multiple times to remove the residual unreacted raw materials and by-products. After washing, the excess water is removed using a vacuum filtration device.

[0150] The washed zinc zeolite imidazolate molecular sieve nanolayer was placed in an oven and dried at 70° C. for 24 h to ensure complete removal of moisture.

[0151] The zinc zeolite imidazole molecular sieve nanolayer with a pore size of 0.38 nm can be synthesized through the above steps.

[0152] Example 4

[0153] In the biogas desulfurization module of the zinc zeolite imidazole molecular sieve nanolayer with a synthetic pore size of 0.30 nm in Example 1, the zinc zeolite imidazole molecular sieve nanolayer with a synthetic pore size of 0.34 nm in Example 2, or the zinc zeolite imidazole molecular sieve nanolayer with a synthetic pore size of 0.38 nm in Example 3, the biogas in the branch port is pressurized by a pressurizing system, so that the pressurized biogas passes through the biogas desulfurization module, and the desulfurized biogas output from the main port is collected, and the sulfur content in this part of the biogas is monitored.

[0154] Specifically, after experimental verification, taking the biogas with an initial sulfur content of 100 ppm as the experimental sample, the biogas after Example 1 contained 0.2 ppm of sulfur after detection; the biogas after Example 2 contained 0.24 ppm of sulfur after detection; the biogas after Example 1 contained 0.19 ppm of sulfur after detection, and the processing time of Example 1, Example 2 and Example 3 was 5 minutes.

[0155] Comparative Example

[0156] Comparative Example 1

[0157] The chemical absorption method is used to treat the hydrogen sulfide in the biogas. Specifically, the biogas with an initial sulfur content of 100 ppm is passed through absorbents such as monoethanolamine and Meike desulfurization amine. After multiple cycles, the treated biogas is tested and the sulfur content is detected to be 13.2 ppm. The treatment time is 3 hours, and reactants are generated to form chemical waste.

[0158] Comparative Example 2

[0159] The physical adsorption method is used to treat the hydrogen sulfide in the biogas. Specifically, the biogas with an initial sulfur content of 100 ppm is passed through adsorbents such as activated carbon, molecular sieves, and aluminum sulfide. After multiple cycles, the treated biogas is tested and the sulfur content is detected to be 12.2 ppm. The processing time is 3 hours, and the adsorbent needs to be replaced after each cycle.

[0160] Comparing Example 1, Example 2, Example 3 and Example 4 with Comparative Example 1 and Comparative Example 2, it can be seen that the zinc zeolite imidazole molecular sieve nanolayer desulfurization method has obvious advantages over the prior art in terms of desulfurization efficiency, operation complexity, cost and environmental impact. Specifically, the zinc zeolite imidazole molecular sieve nanolayer desulfurization method uses lower material costs, lower energy consumption, does not produce harmful waste, and has less impact on the environment. In addition, the operation of the zinc zeolite imidazole molecular sieve nanolayer desulfurization method is simpler and safer, making the zinc zeolite imidazole molecular sieve nanolayer desulfurization method a more economical, environmentally friendly and efficient desulfurization technology.

[0161] Although the embodiments of the present invention are described in detail above, it is obvious to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations are within the scope and spirit of the present invention as described in the claims. Moreover, the present invention described herein may have other embodiments and may be implemented or realized in a variety of ways.

Claims

1. A zinc zeolite imidazole molecular sieve hollow membrane, characterized in that: The hollow membrane is made of polytetrafluoroethylene and filled with a zinc zeolite imidazole molecular sieve nanolayer obtained by a liquid phase interface synthesis method, wherein the zinc zeolite imidazole molecular sieve nanolayer is synthesized with 2-methylimidazole as an organic ligand and zinc acetate as a metal ion source.

2. The zinc zeolite imidazole molecular sieve hollow membrane according to claim 1, characterized in that: The pore size of the sieve holes of the zinc zeolite imidazole molecular sieve nanolayer is between 0.30-0.37 nm.

3. A method for preparing a zinc zeolite imidazole molecular sieve hollow membrane as claimed in claim 1, characterized in that: The method comprises the following steps: a. Prepare an organic ligand solution by dissolving 2-methylimidazole in ethanol at a concentration of 0.01 to 0.1 M; b. Prepare a metallic zinc ion solution by dissolving zinc acetate in high-purity water to a concentration of 0.01 to 0.05 M; c. Prepare a liquid phase interface for reaction: pour 250 mL of zinc acetate solution into a 1 L glass container, and slowly pour 250 mL of oil phase along the wall of the glass tube at a relatively low temperature to form an oil-water interface; d. Slowly drop an ethanol solution of 2-methylimidazole into a glass container at a dropping speed of 0.5 to 5 mL / min, so that it diffuses from the upper oil phase to the oil-water interface and contacts with zinc acetate in the lower water phase to form a zinc zeolite imidazole molecular sieve nanolayer; e. After standing for 5 to 10 hours, the precipitate synthesized at the interface is collected, centrifuged, washed and dried to obtain a zinc zeolite imidazole molecular sieve nanolayer; f. Filling and compressing the obtained zinc zeolite imidazole molecular sieve nanolayer into the pores of the polytetrafluoroethylene hollow fiber membrane.

4. The preparation method according to claim 3, characterized in that: The rotation speed of the centrifugal washing is 10000-15000 rpm, and the time is 5-10 minutes.

5. The preparation method according to claim 3, characterized in that: The oil phase is one of cyclohexane, n-heptane or isooctane.

6. A biogas desulfurization method using the zinc zeolite imidazole molecular sieve hollow membrane as claimed in claim 1, characterized in that: The steps include: a. Pressurizing the biogas and passing it through a zinc zeolite imidazole molecular sieve hollow membrane; b. Through the selective permeation function of the zinc zeolite imidazole molecular sieve nanolayer, hydrogen sulfide molecules are allowed to pass through while methane molecules are intercepted; c. Passing the separated hydrogen sulfide molecules into lime water for tail gas treatment; d. Collect the desulfurized biogas.

7. A biogas desulfurization device using the zinc zeolite imidazole molecular sieve hollow membrane as claimed in claim 1, characterized in that: include: A biogas desulfurization module equipped with a zinc zeolite imidazole molecular sieve hollow membrane; A pressurizing system, used for pressurizing the biogas; a branch port for separating hydrogen sulfide from biogas passing through the zinc zeolite imidazole molecular sieve hollow membrane; A main port for outputting desulfurized biogas; A shell has the branch port and the main port respectively disposed at two opposite ends, the biogas desulfurization module is disposed inside the shell, and the pressurizing system is disposed outside the shell.

8. The biogas desulfurization device according to claim 7, characterized in that: The biogas desulfurization device further comprises a lime water storage module, which is arranged outside the shell and is interconnected with the outlet end of the branch port for treating tail gas.

9. A desulfurization cloth containing the zinc zeolite imidazole molecular sieve hollow membrane as claimed in claim 1, characterized in that: The desulfurization cloth comprises a fiber cloth and a zinc zeolite imidazole molecular sieve hollow membrane arranged on the outer surface of the fiber cloth.

10. A method for using the desulfurization cloth according to claim 9, characterized in that: The method of use includes surrounding or covering the biogas with desulfurization cloth, or arranging the desulfurization in a pipeline to allow the biogas to pass through.