Use of a polyazolate porous material for one-step purification of ethylene in a multi-component light hydrocarbon mixture

Abstract

The application discloses application of a multi-nitrogen azole porous material to one-step purification of ethylene in a multi-component light hydrocarbon mixture. Based on a customized geometric pore environment, the metal imidazole framework MAF-7 has higher adsorption of propane, propylene, ethane and acetylene than ethylene, so that ethylene can be directly obtained from binary, ternary and quinary gas mixtures. Further, one-step purification of ethylene can be completed by passing a five-component gas mixture through a container filled with the MAF-7 at a certain temperature and pressure, and desorption and regeneration of the adsorbent can be completed by inert gas blowing or vacuumizing at room temperature. The material exhibits high ethane adsorption capacity and high ethane / ethylene adsorption ratio under ambient conditions, and has superior adsorption performance, so that ethylene can be one-step purified in a complex light hydrocarbon mixture, and an effective method is provided for designing efficient and commercially valuable adsorbents to promote important industrial gas separation.

Description

Technical Field

[0001] This invention relates to the field of adsorption materials, specifically a method for synthesizing MAF-7 and its application in one-step purification of ethylene from a multi-component light hydrocarbon mixture. Background Technology

[0002] Ethylene is an important industrial raw material for the petrochemical industry. Ethylene production typically produces byproducts such as propane, propylene, ethane, and acetylene. Ethylene purification methods include liquid amine washing of carbon dioxide, catalytic hydrogenation of acetylene, and cryogenic distillation to remove ethane. However, these methods are cumbersome and complex, consuming significant energy. Pressure swing adsorption (PSA) technology, on the other hand, promises to significantly reduce energy consumption in the separation process. Metal-organic frameworks (MOFs) with customized porous structures and functions are considered ideal platforms for gas adsorption and separation.

[0003] In existing technologies, many MOF materials exhibit good gas adsorption performance, such as ZIF materials, which are metal-imidazolium salt frameworks (MAFs), also known as zeolite-imidazolium salt frameworks (ZIFs). These are zeolite-like topologies formed by linking transition metal (such as zinc and cobalt) ions with imidazolium or its derivatives, offering advantages such as high structural stability, simple synthesis processes, tunable pore size, and modifiable frameworks. However, currently reported ZIF materials for the separation and purification of ethylene face a significant challenge in balancing adsorption capacity and selectivity. This is particularly true for multi-component mixtures such as ternary mixtures (ethane / ethylene / acetylene and ethylene / acetylene / carbon dioxide) and quaternary mixtures (ethane / ethylene / acetylene / carbon dioxide), where direct separation of high-purity ethylene is even more difficult. For example, patent CN110237816B discloses a method for preparing a silver nitrate-modified metal-organic framework adsorbent and its application. Although silver nitrate forms a π complex bond with the C=C double bond in ethylene, and the bond energy of the π complex bond is stronger than that of van der Waals forces, and the adsorbent material has a higher adsorption capacity for ethylene than for ethane, thus achieving the separation of ethylene / ethane, its adsorption selectivity is limited to binary components. For multi-component gas mixtures such as ternary mixtures of ethane / ethylene / acetylene, quaternary mixtures to quinary light hydrocarbon mixtures, it is difficult to have high adsorption capacity and adsorption selectivity.

[0004] Therefore, it is essential to develop porous materials that can purify ethylene from multi-component gases in one step, especially suitable for five-component light hydrocarbon mixtures (propane / propylene / ethane / ethylene / acetylene), and that are low-cost, high-performance, and highly stable.

[0005] Technical content

[0006] This invention is achieved through the following technical solution:

[0007] An application of a polyazole porous material in one-step purification of ethylene from a multi-component light hydrocarbon mixture, wherein the polyazole porous material can efficiently separate ethylene from a five-component light hydrocarbon mixture (propane / propylene / ethane / ethylene / acetylene);

[0008] The synthesis method of the polyazole porous material is as follows: an aqueous solution of 3-methyl-1H-1,2,4-triazole is added dropwise to an aqueous solution of zinc nitrate hexahydrate, ammonia is added dropwise to the mixed solution, the mixture is stirred at room temperature, filtered, washed with methanol, and dried to obtain a metal imidazole framework MAF-7 adsorbent with the chemical formula [Zn(mtz)2].

[0009] Furthermore, the molar ratio of 3-methyl-1H-1,2,4-triazole to zinc nitrate hexahydrate is 2:1;

[0010] The amount of ammonia added is 2-10% of the total volume of the mixed solution; the concentration of zinc in the mixed solution is 0.01-0.1 mol / L.

[0011] This invention prepares MAF-7 by adjusting the amount of reactants and solvents, and then scales up the synthesis. Specifically, it is a method for synthesizing MAF-7 and its application in one-step purification of ethylene from a multi-component light hydrocarbon mixture.

[0012] Furthermore, a five-component mixed gas (propane / propylene / ethane / ethylene / acetylene) was introduced into an adsorption column packed with MAF-7 material. The flow rate was adjusted by a pressure valve and flow meter at the inlet of the adsorption column. A dynamic adsorption breakthrough experiment was conducted under certain temperature and pressure conditions. The gas concentration was monitored in real time at the outlet of the adsorption column using gas chromatography.

[0013] Furthermore, the sample packed in the adsorption column is 0.5~1 g, the flow rate of the five-component mixed gas entering the adsorption column is 0~5 mL / min, and the adsorption temperature is 0~25 ℃ and the pressure is 1 bar or above when the impurity gas is adsorbed on the adsorbent.

[0014] As a further improvement to the efficient separation method of the present invention, the MAF-7 can achieve efficient separation of ethylene from a five-component light hydrocarbon mixture (propane / propylene / ethane / ethylene / acetylene). Polymer-grade ethylene product gas can be generated through a single adsorption separation step, with a high-purity ethylene yield of 10-20 cm³ obtained in a single breakthrough experiment. 3 / g.

[0015] Technical effect

[0016] The synthesis method of MAF-7 provided by this invention employs room temperature stirring. MAF-7 material is obtained through simple room temperature stirring, filtration, and drying. By scaling up the production with equal proportions of metal and ligand, hundreds of grams of product can be obtained in a single step, enabling industrial-scale synthesis. Compared with previously reported metal imidazole porous materials, the ethane-selective adsorbent prepared by this invention exhibits both higher ethane adsorption capacity and ethane / ethylene separation selectivity. Furthermore, this adsorbent possesses better structural stability, thermal stability, and easy regeneration and high cycle stability, making it more suitable for industrial separation operations. The MAF-7 prepared by this invention can achieve one-step purification of ethylene from a five-component mixed gas. Polymer-grade ethylene product gas can be generated through one-step adsorption and separation, with a high-purity ethylene yield of 10-20 cm³ in a single breakthrough experiment. 3 / g. Compared with other ethane selective materials, the MAF-7 prepared by this invention has lower raw material prices and a simpler and greener preparation process, which can better realize the commercial application of one-step purification of ethylene from complex light hydrocarbon mixtures. Attached Figure Description

[0017] Figure 1 The image shows a SEM image of MAF-7 obtained in Example 1.

[0018] Figure 2 The image shows a comparison of the XRD patterns of MAF-7 obtained in Example 1 and the simulated peak.

[0019] Figure 3 The adsorption-desorption curve of MAF-7 obtained in Example 1 under nitrogen at 77 K;

[0020] Figure 4 The adsorption curve of MAF-7 on a five-component mixture gas at 298 K obtained in Example 1;

[0021] Figure 5 The XRD patterns of MAF-7 obtained in Example 1 after being processed under different conditions;

[0022] Figure 6 The XRD patterns of MAF-7 obtained in Example 1 after treatment with different pH values;

[0023] Figure 7 The isotherm of multiple ethane cycle adsorption of MAF-7 obtained in Example 1;

[0024] Figure 8 Diagram of the adsorption column and breakthrough experimental setup;

[0025] Figure 9 The breakthrough curve of MAF-7 for ethane:ethylene = 1:1 (v / v) mixture obtained in Example 1 under room temperature pressure and dry conditions;

[0026] Figure 10 The breakthrough curve of MAF-7 for a propylene:ethylene = 1:1 (v / v) mixture obtained in Example 1 under room temperature pressure and dry conditions;

[0027] Figure 11 The breakthrough curve of MAF-7 obtained in Example 1 for an ethane:ethylene:acetylene mixture of 9:90:1 (v / v / v) at room temperature and pressure under dry conditions.

[0028] Figure 12 The breakthrough curve of the MAF-7 obtained in Example 1 for a mixture of propane:propylene:ethane:ethylene:acetylene = 9:10:10:70:1 (v / v / v / v / v) under room temperature pressure and dry conditions. Detailed Implementation

[0029] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments. The technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0030] Detailed implementation method: A method for synthesizing MAF-7 includes the following steps: an aqueous solution of 3-methyl-1H-1,2,4-triazole is added dropwise to an aqueous solution of zinc nitrate hexahydrate, ammonia is added dropwise, the mixture is stirred at room temperature, filtered, washed with methanol, and dried to obtain a metal imidazole framework (MAF) adsorbent with the chemical formula [Zn(mtz)2].

[0031] A one-step purification process for ethylene from a five-component light hydrocarbon mixture (propane / propylene / ethane / ethylene / acetylene) at room temperature includes the following steps: The five-component gas mixture (propane / propylene / ethane / ethylene / acetylene) is passed into an adsorption column packed with MAF-7 material. The flow rate is regulated by a pressure valve and flow meter at the column inlet. A dynamic adsorption breakthrough experiment is conducted under specific temperature and pressure conditions. The gas concentration is monitored in real-time at the column outlet using gas chromatography. Desorption and regeneration of the adsorbent are achieved by purging with an inert gas at room temperature or under vacuum conditions.

[0032] The synthesis process involves adjusting the amounts of metal salts, ligands, and solvents to minimize synthesis costs. Furthermore, the synthesis is simple, requiring only simple room-temperature stirring to obtain MAF-7. This invention provides a one-step method for purifying ethylene from a five-component light hydrocarbon mixture (propane / propylene / ethane / ethylene / acetylene). This method is simple, widely applicable, and enables efficient separation of ethane and ethylene. Polymer-grade ethylene gas can be generated through a single adsorption separation step, potentially leading to the industrial application of MAF-7 materials.

[0033] In some specific embodiments, the molar ratio of 3-methyl-1H-1,2,4-triazole and zinc nitrate hexahydrate is 2:1, the amount of ammonia added is 2-10% of the total volume of the mixed solution, the reaction is carried out at room temperature, and the reaction time is 3-5 h, which can achieve the synthesis of 1g-100g.

[0034] In some specific embodiments, MAF-7 material is prepared by simple room temperature stirring, filtration, and drying. This invention is not limited to this specific yield; the same principle applies to obtaining hundreds of grams of product in a single batch by proportionally increasing the metal and ligand ratios.

[0035] In some specific embodiments, the volume fraction of impurity gases in the mixed gas is 0-50%, and it does not contain zero values.

[0036] In some specific embodiments, the sample packed in the adsorption column is 0.5 to 1 g, the flow rate of the five-component mixed gas entering the adsorption column is 0 to 5 mL / min, and the adsorption temperature is 0 to 25 °C and the pressure is 1 bar or above when the impurity gas is adsorbed on the adsorbent.

[0037] In some specific embodiments, MAF-7 can achieve efficient separation of ethylene from a five-component light hydrocarbon mixture (propane / propylene / ethane / ethylene / acetylene). Polymer-grade ethylene product gas can be generated through a single adsorption separation step, with a high-purity ethylene yield of 10–20 cm³ in a single breakthrough experiment. 3 / g.

[0038] The following are specific examples.

[0039] Example 1

[0040] 10 mL of an aqueous solution of 3-methyl-1H-1,2,4-triazole (0.168 g, 2.0 mmol) was added dropwise to 10 mL of an aqueous solution of zinc nitrate hexahydrate (0.297 g, 1.0 mmol), followed by the addition of 1 mL of ammonia (14% by mass) with stirring. The solution was stirred at room temperature for 4 hours, then filtered, washed with methanol, and dried in air to obtain the product MAF-7.

[0041] Example 2

[0042] 10 mL of an aqueous solution of 3-methyl-1H-1,2,4-triazole (0.168 g, 2.0 mmol) was added dropwise to 10 mL of an aqueous solution of zinc nitrate hexahydrate (0.297 g, 1.0 mmol), followed by the addition of 1.5 mL of 14% ammonia solution with stirring. The solution was stirred at room temperature for 4 hours, then filtered, washed with methanol, and dried in air to obtain the product MAF-7.

[0043] The MAF-7 prepared in Example 1 was used as the test sample. Before testing the adsorption and separation performance of the prepared sample, it was washed with methanol. The prepared white powder was washed with methanol three times. The activation conditions for the test sample were 100°C and degassing under vacuum for 6 hours. Then, the gas adsorption and separation performance of the sample was tested, with the pressure range being 0-1 bar.

[0044] To evaluate the actual separation performance of MAF-7 for five-component gas mixtures, Figure 8 The apparatus shown was used to conduct dynamic breakthrough experiments on ethane / ethylene, ethane / ethylene / acetylene, propylene / ethylene, and propane / propylene / ethane / ethylene / acetylene mixtures, respectively. Approximately 0.5–1 g of sample was packed into a stainless steel adsorption column with an inner diameter of 4 mm and a length of 125 mm. The column was purged with a high-purity inert gas to remove residual gas. The sample adsorption column was fixed in an indoor apparatus, and the flow rate of the mixed gas was regulated by a pressure valve and flow meter at the inlet of the adsorption column. The gas concentration was monitored in real-time at the outlet of the adsorption column using a gas chromatograph (490 Micro GC, Agilent Technologies). The entire experiment was conducted at 0–25 °C, with flow rates of 0–5 mL / min for mixtures of ethane:ethylene (1:1, v / v); ethane:ethylene:acetylene = (9:90:1, v / v / v); propylene:ethylene (1:1, v / v); and propane:propylene:ethane:ethylene:acetylene (9:10:10:70:1, v / v / v / v / v).

[0045] To characterize the microstructure of the MAF-7 material, the product obtained in Example 1 was subjected to SEM characterization, and the results are as follows: Figure 1 As shown.

[0046] To confirm the crystal structure of the synthesized sample, the sample synthesized in Example 1 was characterized by XRD, and the results were compared with the simulated peaks of the theoretical crystal structure of MAF-7. The comparison results are as follows: Figure 2 As shown in the figure, the XRD diffraction peaks of MAF-7 prepared by the method of this invention are consistent with the simulated peaks of the theoretical crystal structure of the original structure, indicating that the method successfully synthesized MAF-7 material.

[0047] To characterize the adsorption capacity of MAF-7 material for different gases, a Micromeritics ASAP 2020 instrument was used to test the adsorption performance of the product obtained in Example 1 for different gases. Adsorption curves for each gas were measured at 298 K. Figure 3 The nitrogen adsorption-desorption curves for this material at 77 K are shown below. Figure 4The adsorption-desorption curves are for ethane, ethylene, propane, propylene, and acetylene, respectively. From... Figure 3-4 As can be seen, MAF-7 has a high BET specific surface area and exhibits stronger adsorption and separation performance for ethane, propane, propylene, and acetylene than for ethylene within the test temperature range, indicating that MAF-7 is an excellent ethylene purification adsorbent.

[0048] To test the stability of the MAF-7 material, the acid-base stability and air stability of the material were tested, using the product prepared in Example 1 as an example. Figure 5 , Figure 6 As can be seen from the XRD pattern, when the sample is exposed to different acid and alkaline environments, or when the sample is placed in the air for six months, the sample still maintains its original crystal structure. Figure 7 The figure shows the cyclic adsorption isotherm of ethane gas. It can be seen that the performance of MAF-7 material is completely maintained after multiple adsorption-desorption cycle experiments.

[0049] (1) Experiment on the adsorption and separation effect of two-component mixed gases ethane: ethylene and propylene: ethylene

[0050] To test the actual performance of MAF-7 material in separating ethane:ethylene (1:1, v / v) and propylene:ethylene (1:1, v / v) mixtures, the product obtained in Example 1 was used as an example to conduct the above-mentioned mixture separation experiment. The specific process was as follows: the mixed gas was precisely controlled by a pressure reducing valve and a gas mass flow meter to pass through an adsorption column (Φ 4×125 mm) packed with adsorbent (sample amount: 0.8 g) at a pressure of 1.0 bar and a flow rate of 2 mL / min. The temperature of the adsorption column was controlled at 298 K. Timing was started simultaneously when the mixed gas began to enter the adsorption column, and the tail gas concentration was monitored in real time at the end of the adsorption column using chromatography (GC-2014C, TCD detector). Data was recorded until the mixed gas concentration reached the initial concentration, at which point both gases were considered to have completely exited, and adsorption was considered complete.

[0051] When the gas mixture is ethane / ethylene and propylene / ethylene (volume ratio 1 / 1), the breakthrough curve of this adsorbent material is as follows: Figure 8 a, b, from Figure 9 , 10 As can be seen, this material can effectively remove ethane and propylene from a mixture of ethane and ethylene, and propylene and ethylene, thus achieving effective separation of ethylene.

[0052] (2) Adsorption and separation effect experiment of three-component gas (ethane: ethylene: acetylene) and five-component gas (propane: propylene: ethane: ethylene: acetylene).

[0053] To test the actual performance of MAF-7 material in separating ethane:ethylene:acetylene (9:90:1, v / v / v) and propane:propylene:ethane:ethylene:acetylene (9:10:10:70:1, v / v / v / v / v) mixtures, the product obtained in Example 1 was used as an example to conduct the above-mentioned mixture separation experiment. The specific process was as follows: the mixed gas was precisely controlled by a pressure reducing valve and a gas mass flow meter to pass through an adsorption column (Φ 4×125 mm) filled with adsorbent (sample amount: 0.8 g) at a pressure (1.0 bar) and a flow rate (2 mL / min). The temperature of the adsorption column was controlled at 298 K. Timing was started simultaneously when the mixed gas began to enter the adsorption column, and the tail gas concentration was monitored in real time at the end of the adsorption column using chromatography (GC-2014C, TCD detector). Data was recorded until the mixed gas concentration reached the initial concentration, at which point the two gases were considered to have completely exited, and adsorption was considered complete.

[0054] When the gas mixture is ethane:ethylene:acetylene = (9:90:1, v / v / v); propane:propylene:ethane:ethylene:acetylene (9:10:10:70:1, v / v / v / v / v), the breakthrough curves of the adsorbent material are as follows: Figure 11 , 12 ,from Figure 11 , 12 As can be seen, this material can achieve one-step purification of ethylene in the aforementioned ternary and pentaneous gas mixtures. Polymer-grade ethylene product gas can be generated through one-step adsorption separation, and the yield of high-purity ethylene obtained in a single breakthrough experiment is 10–20 cm³. 3 / g.

[0055] As can be seen from the adsorption and separation effects of two-component and multi-component systems, the MAF-7 of the present invention has good adsorption selectivity for ethylene. It can achieve good separation effect for ethylene in both two-component and multi-component gas environments, and can achieve one-step adsorption and separation with excellent separation effect. This indicates that the product of the present invention can be applied to multi-component gas separation in industry, and can better realize the commercial application of one-step purification of ethylene from complex light hydrocarbon mixtures.

[0056] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An application of a polyazole-based porous material for one-step purification of ethylene from a multi-component light hydrocarbon mixture, characterized in that, Using the metal imidazole framework MAF-7 as the adsorbent, and taking advantage of the fact that MAF-7 has a stronger adsorption capacity for propane, propylene, ethane, and acetylene than for ethylene, ethylene was efficiently separated from a mixture of five light hydrocarbon components, namely propane, propylene, ethane, ethylene, and acetylene. The method for synthesizing the polyazole porous material includes the following steps: adding an aqueous solution of 3-methyl-1H-1,2,4-triazole dropwise to an aqueous solution of zinc nitrate hexahydrate to obtain a mixture; adding ammonia dropwise to the mixture to obtain a mixed solution for subsequent reactions; stirring at room temperature; filtering; washing with methanol; and drying to obtain MAF-7 with the chemical formula Zn(mtz)2 as a metal imidazole framework.

2. The application of the polyazole porous material as described in claim 1 for one-step purification of ethylene from a multi-component light hydrocarbon mixture, characterized in that, The molar ratio of 3-methyl-1H-1,2,4-triazole to zinc nitrate hexahydrate is 2:1; the amount of ammonia added is 5% of the total volume of the mixed solution; the concentration of zinc in the mixed solution is 0.01-0.1 mol / L.

3. The application of the polyazole porous material as described in claim 1 for one-step purification of ethylene from a multi-component light hydrocarbon mixture, characterized in that, Includes the following steps: A five-component gas mixture, consisting of propane, propylene, ethane, ethylene, and acetylene, is introduced into an adsorption column packed with MAF-7 material. The flow rate is regulated by a pressure valve and flow meter at the inlet of the adsorption column. A dynamic adsorption breakthrough experiment is conducted under certain temperature and pressure conditions. The gas concentration is monitored in real time at the outlet of the adsorption column using gas chromatography.

4. The application of the polyazole porous material as described in claim 1 for one-step purification of ethylene from a multi-component light hydrocarbon mixture, characterized in that, The mixture is a five-component gas mixture consisting of propane, propylene, ethane, ethylene, and acetylene, wherein the total volume fraction of propane, propylene, ethane, and acetylene as impurity gases is 0-50%, and there is no zero value.

5. The application of the polyazole porous material as described in claim 3 for one-step purification of ethylene from a multi-component light hydrocarbon mixture, characterized in that, When impurity gases are adsorbed on the adsorbent, the adsorption temperature is 0–25℃ and the pressure is 1 bar or higher.

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