A quaternary ammonium salt modified molecular sieve for adsorbing and purifying the electron gas octafluoropropane, its preparation method and application.

Abstract

This invention discloses a quaternary ammonium salt modified molecular sieve for adsorbing and purifying the electronic gas octafluoropropane, its preparation method, and its application. The synthesis method involves adding ZSM-5 molecular sieve powder to a quaternary ammonium salt aqueous solution, stirring at a second preset temperature for a second preset time, filtering with water, and drying to obtain the quaternary ammonium salt modified molecular sieve. In this invention, a TMAZ microporous material with uniform pore size is prepared by precisely performing quaternary ammonium salt single-ion exchange on the ZSM-5 molecular sieve. This material not only exhibits a high adsorption capacity for pentachlorofluoroethane but also significantly inhibits the adsorption of octafluoropropane. This material has a high pentachlorofluoroethane / octafluoropropane separation factor, thereby enabling the adsorption and purification of trace amounts of pentachlorofluoroethane from octafluoropropane.

Description

Technical Field

[0001] This invention relates to the field of gas adsorption and separation materials, specifically a quaternary ammonium salt modified molecular sieve for adsorbing and purifying the electronic gas octafluoropropane, its preparation method, and its application. Background Technology

[0002] Octafluoropropane is an important electronic gas widely used in semiconductor manufacturing processes such as cleaning and etching. For example, a mixture of octafluoropropane and oxygen is used as a plasma etching material, selectively reacting with the metal substrate of silicon wafers. During octafluoropropane preparation, pentachlorofluoroethane impurities (100 ppm) are inevitably generated. Even extremely low concentrations of pentachlorofluoroethane impurities can severely affect the precision of semiconductor etching processes. Obtaining ultra-high purity octafluoropropane (7N) is of great significance for the manufacture of very large-scale integrated circuits. Furthermore, considering the high ozone depletion potential (ODP) and global warming potential (GHP) of pentachlorofluoroethane, capturing pentachlorofluoroethane from octafluoropropane is an indispensable step in promoting the greening of the electronics industry.

[0003] Current methods for purifying octafluoropropane mostly employ low-temperature, high-pressure distillation. Patent CN103664502A describes a method for purifying octafluoropropane by subjecting the octafluoropropane feed gas to two distillations at -37℃ to 10℃ and 1 to 6 bar, combined with multiple low-temperature, high-pressure adsorption processes, ultimately achieving a target product with chlorofluorocarbon impurities ≤1ppm. However, this method requires multiple distillations, resulting in high energy consumption, and necessitates the integration of low-temperature / high-pressure adsorption processes, making operation complex. In practical applications, due to the only 1.1℃ difference in boiling points between octafluoropropane and monochloropentafluoroethane, they readily form low-boiling-point azeotropes, making the separation and purification of this mixture difficult, energy-intensive, and costly. Adsorption separation processes for separating azeotropes offer advantages such as low energy consumption, low cost, simple operation, high efficiency, environmental friendliness, and recyclability. Therefore, achieving efficient purification of octafluoropropane at room temperature using a more environmentally friendly and low-energy adsorption separation process would be of significant scientific and industrial value.

[0004] In fact, for gases that are difficult to separate, thermodynamic separation can be achieved as long as the adsorbent has different forces acting on the two gases; kinetic separation can be achieved if the adsorbent diffuses differently on the two gases. If the pore size of the adsorbent is between that of the two gas molecules, separation can be achieved based on the principle of "adsorbing smaller molecules and displacing larger ones." These three mechanisms are widely used in the separation of similar gas molecules such as ethylene, ethane, and propylene, but there are no reports on their application in the purification of the electronic gas octafluoropropane. Patent CN1220548C discloses an adsorbent for purifying perfluorinated carbon, its production method, high-purity octafluoropropane and octafluorocyclobutane, and their uses. This adsorbent is a carbon-based adsorbent that can remove 10–10,000 ppm of monochloropentafluoroethane from crude octafluoropropane. The adsorbent comprises: (1) acid washing and then water washing of the raw carbon; (2) deoxygenation of the raw carbon in an inert gas stream at 50–250°C; (3) recarbonization in an inert gas stream at 500–700°C; and (4) activation in a mixed gas stream containing inert gas, carbon dioxide, and water vapor. The synthesis steps of this adsorbent are relatively complicated, and the repeated high-temperature calcination results in low yield. Furthermore, calcination produces toxic and harmful substances such as greenhouse gases. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a simple and easily synthesized adsorption and separation material for the deep removal of trace azeotropic impurities from octafluoropropane at room temperature. Specifically, it is a quaternary ammonium salt modified molecular sieve for adsorbing and purifying the electronic gas octafluoropropane, along with its preparation method and application. The synthesis method of the adsorption material involves introducing bulky hydrogen-rich quaternary ammonium salt cations to adjust the surface chemical properties and pore size of the ZSM-5 molecular sieve pores, thereby achieving the separation of chloropentafluoroethane / octafluoropropane.

[0006] The objective of this invention is achieved through the following technical solution: a method for synthesizing quaternary ammonium salt modified molecular sieves for adsorbing and purifying octafluoropropane, comprising the following steps:

[0007] (1) Add the quaternary ammonium salt to the aqueous solution and stir for a first preset time at a first preset temperature to obtain the quaternary ammonium salt aqueous solution. Preferably, water bath heating is used.

[0008] (2) Add ZSM-5 molecular sieve powder to a quaternary ammonium salt aqueous solution, stir in a water bath at a second preset temperature for a second preset time, filter with water, and dry to obtain a quaternary ammonium salt modified molecular sieve.

[0009] ZSM-5 molecular sieve has a suitable pore size (sine: Straight channel: With its alternating linear and sinusoidal orbitals, excellent hydrothermal stability and ion exchange capacity, the pore size and internal surface chemical properties can be adjusted by replacing the equilibrium cations outside its framework, thereby enhancing its shape selectivity and separation ability for mixtures. As a result, it is widely used in gas separation and petrochemical fields.

[0010] The technical solution of this invention replaces the H in ZSM-5 molecular sieve with a large-volume, hydrogen-rich quaternary ammonium salt cation. + The diameter of the quaternary ammonium salt cation is much larger than that of the hydrogen ion, which increases the volume of the cation within the ZSM-5 molecular sieve and thus reduces the average pore size of the material. This inhibits the entry of octafluoropropane into the material's channels, thereby reducing the adsorption capacity of the material for octafluoropropane. Simultaneously, the introduced quaternary ammonium salt cation is anchored in the cross-cavity of the two orbitals, enhancing the adsorption affinity of pentachlorofluoroethane within the confined space through F / Cl…H van der Waals interactions. This increases the thermodynamic affinity of the material for pentachlorofluoroethane, thereby maintaining a high adsorption capacity for it. The quaternary ammonium salt modified molecular sieve obtained using the synthesis method provided in this invention can adsorb and remove trace azeotropic impurities of pentachlorofluoroethane from octafluoropropane. The modified molecular sieve can achieve a high-purity (99.99999%, 7N grade) octafluoropropane yield of up to 61830 L / t, exhibiting superior separation performance compared to existing industrial adsorbents.

[0011] Preferably, in step (1), the quaternary ammonium salt is any one of tetramethylammonium chloride, choline chloride, and tetraethylammonium chloride. Using the above three quaternary ammonium salts can yield quaternary ammonium salt modified molecular sieves with better separation and purification capabilities for octafluoropropane.

[0012] Preferably, the concentration of the quaternary ammonium salt aqueous solution is 5–55 g / L. As the volume of the quaternary ammonium salt cation increases, a higher salt concentration is required to promote the completion of the ion exchange process; however, excessively high salt concentrations can also clog the pores, resulting in insufficient adsorption. More preferably, the concentration of the quaternary ammonium salt aqueous solution is 8–38 g / L.

[0013] Preferably, in step (1), the first preset temperature is 25℃~35℃.

[0014] Preferably, in step (1), the first preset time is 20 to 30 minutes.

[0015] Preferably, before step (1), the process further includes a primary activation treatment of the ZSM-5 molecular sieve, wherein the primary activation treatment includes:

[0016] The ZSM-5 molecular sieve is heated to 550-650℃ at a rate of 10℃ / min, maintained at this temperature for 5 hours, and then cooled to 100℃ at a rate of 10℃ / min. The primary activation treatment is used to activate the ZSM-5 molecular sieve before step (1) to remove residual organic template agents and adsorbed small molecules such as water and carbon dioxide in the pores, making the activated molecular sieve more likely to exchange cations in the quaternary ammonium salt.

[0017] Preferably, the amount of ZSM-5 molecular sieve powder added in step (2) is 0.016 to 0.024 g / mL. That is, 0.016 to 0.024 g of ZSM-5 molecular sieve powder is added per mL of quaternary ammonium salt aqueous solution.

[0018] More preferably, the amount of ZSM-5 molecular sieve powder added in step (2) is 0.02 g / mL.

[0019] Preferably, in step (2), the second preset temperature is 60℃~100℃. As the volume of the quaternary ammonium salt cation increases, a longer exchange time is required to allow the H+ in the molecular sieve powder to be released. + The material is fully displaced. More preferably, the second preset time is 4 to 9 hours.

[0020] Preferably, in step (2), the modified ZSM-5 molecular sieve is filtered with sufficient water to prevent quaternary ammonium salts from adhering to the material surface and reducing adsorption performance. More preferably, the mass ratio of molecular sieve to water is 1:200.

[0021] Preferably, in step (2), the drying operation includes:

[0022] The filtered product was heated to 100–110°C at a rate of 5°C / min, maintained at this temperature for 2 hours, then heated to 195–205°C at a rate of 5°C / min, maintained at this temperature for 4 hours, and then cooled to 30–35°C at a rate of 5°C / min. The setting of the heating rate, temperature, and time in the drying operation removed most of the moisture in the synthesized material without causing the decomposition of quaternary ammonium cations.

[0023] This invention also provides a quaternary ammonium salt modified molecular sieve obtained according to any of the above-described synthesis methods. The quaternary ammonium salt modified molecular sieve provided by this invention exhibits high separation performance for pentachlorofluoroethane / octafluoropropane.

[0024] This invention also provides a method for synthesizing a quaternary ammonium salt modified molecular sieve, characterized in that the quaternary ammonium salt modified molecular sieve comprises a ZSM-5 molecular sieve and a quaternary ammonium salt cation, wherein the quaternary ammonium salt cation is adsorbed in the channels of the ZSM-5 molecular sieve, and the mass ratio of ZSM-5 molecular sieve to quaternary ammonium salt cation is 100:3.5-9.5. More preferably, the mass ratio of ZSM-5 molecular sieve to quaternary ammonium salt cation is 100:4.0-8.8.

[0025] This invention also provides an application of quaternary ammonium salt modified molecular sieves in the adsorption and purification of electronic gas octafluoropropane.

[0026] Preferably, in the application of the quaternary ammonium salt modified molecular sieve provided by the present invention in the adsorption and purification of electronic gas octafluoropropane, 1g of the quaternary ammonium salt modified molecular sieve treats 70-120mL of crude chloropentafluoroethane / octafluoropropane gas, wherein the ratio of chloropentafluoroethane / octafluoropropane in the crude gas is 1:9999 (v / v), and the pressure is 1 standard atmosphere.

[0027] The mechanism of this invention is as follows:

[0028] This invention introduces large-volume, hydrogen-rich quaternary ammonium salt cations into the pores of ZSM-5 molecular sieves, which reduces the adsorption pore size of the ZSM-5 molecular sieve, thereby reducing the adsorption of octafluoropropane with a larger molecular size. This allows the material to retain more adsorption sites for storing the impurity chloropentafluoroethane. Simultaneously, the introduced quaternary ammonium salt cations interact with chloropentafluoroethane via F / Cl…H interactions, enhancing the adsorption affinity of chloropentafluoroethane within the confined pores. The adsorbent material provided by this invention reduces the amount of octafluoropropane entering the pores when removing trace amounts of chloropentafluoroethane from octafluoropropane, enhances chloropentafluoroethane adsorption, increases the yield of high-purity octafluoropropane per unit mass of adsorbent, and achieves cost reduction and efficiency improvement.

[0029] The present invention has the following advantages and effects compared with the prior art:

[0030] (1) The adsorption separation method used in this invention can solve the bottleneck in the traditional octafluoropropane purification process, where octafluoropropane and impurity monochloropentafluoroethane (100ppm) form an azeotrope, making it difficult to achieve deep removal (reducing the impurity to below 1ppm). Moreover, the separation conditions have low energy consumption and simple operation.

[0031] (2) The ZSM-5 molecular sieve raw material used in this invention is widely available and has a low synthesis cost. It has been widely used in industrial catalysis and separation. The quaternary ammonium salt modification preparation method described in this invention has mild conditions and great industrial application prospects.

[0032] (3) The quaternary ammonium salt modified molecular sieve synthesized in this invention can treat crude octafluoropropane gas containing 100 ppm monochloropentafluoroethane at 25℃ and 101.325 kPa. Its 7N grade octafluoropropane yield is 61.83 L / kg, which is much higher than that of currently commercial porous adsorbents. Attached Figure Description

[0033] Figure 1 The XRD pattern of the TZEO-1# molecular sieve material synthesized from the raw materials and in Example 1 is shown.

[0034] Figure 2 The adsorption isotherm (298 K) of the TZEO-1# molecular sieve material synthesized in Example 1 for pentachlorofluoroethane / octafluoropropane;

[0035] Figure 3 The adsorption isotherm (298 K) of the TZEO-2# molecular sieve material synthesized in Example 2 for pentachlorofluoroethane / octafluoropropane;

[0036] Figure 4 The image shows the dynamic adsorption curve of the TZEO-1# molecular sieve material synthesized in Example 1 on a 1:9999 mixture of chloropentafluoroethane and octafluoropropane. Detailed Implementation

[0037] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto. For process parameters not specifically noted, conventional techniques can be referred to.

[0038] The technical solutions are illustrated in the following description with specific figures to provide a full understanding of this application. However, this application can be implemented in many other ways different from those described herein, and similar extensions made by those skilled in the art without inventive effort are all within the scope of protection of this invention.

[0039] Example 1

[0040] A tetramethylammonium ion (CH3)4N + The modified ZSM-5 molecular sieve is synthesized as follows:

[0041] The ZSM-5 molecular sieve was heated to 550℃ at a rate of 10℃ / min, held at this temperature for 5 hours, and then cooled to 100℃ at a rate of 10℃ / min to obtain the activated ZSM-5 molecular sieve.

[0042] Take 1g of activated ZSM-5 molecular sieve and add it to 50mL of 10.25g / L tetramethylammonium chloride aqueous solution. React at 80℃ for 4 hours. Wash the product obtained after the reaction with deionized water and filter. The filtered material is heated to 100℃ in a muffle furnace at a rate of 5℃ / min, held at this temperature for 2 hours, then heated to 200℃ at a rate of 5℃ / min, held at this temperature for 4 hours, and then cooled to 30℃ at a rate of 5℃ / min. The obtained material is designated TZEO-1#, with pore sizes concentrated in the following areas: By mass ratio, ZSM-5 molecular sieve: quaternary ammonium salt cation = 100: 4.3.

[0043] Example 2

[0044] A tetramethylammonium ion (CH3)4N + The modified ZSM-5 molecular sieve is synthesized as follows:

[0045] 1 g of activated ZSM-5 molecular sieve was added to 50 mL of a 5.50 g / L tetramethylammonium chloride aqueous solution and reacted at 80 °C for 4 hours. The product obtained after the reaction was washed and filtered with deionized water. The filtered material was heated to 100 °C at a rate of 5 °C / min in a muffle furnace and held at this temperature for 2 hours. Then, it was heated to 200 °C at a rate of 5 °C / min and held at this temperature for 4 hours. Finally, it was cooled to 30 °C at a rate of 5 °C / min. The resulting material was designated TZEO-2#, with pore sizes concentrated in the following areas: By mass ratio, ZSM-5 molecular sieve: quaternary ammonium salt cation = 100: 1.9

[0046] The activation process for ZSM-5 molecular sieve is the same as in Example 1.

[0047] Example 3

[0048] A tetramethylammonium ion (CH3)4N + The modified ZSM-5 molecular sieve is synthesized as follows:

[0049] 1 g of activated ZSM-5 molecular sieve was added to 50 mL of a 21.56 g / L tetramethylammonium chloride aqueous solution and reacted at 80 °C for 4 hours. The product obtained after the reaction was washed and filtered with deionized water. The filtered material was heated to 100 °C at a rate of 5 °C / min in a muffle furnace and held at this temperature for 2 hours. Then, it was heated to 200 °C at a rate of 5 °C / min and held at this temperature for 4 hours. Finally, it was cooled to 30 °C at a rate of 5 °C / min. The resulting material was designated TZEO-3#, with pore sizes concentrated in the following areas: By mass ratio, ZSM-5 molecular sieve: quaternary ammonium cation = 100: 9.8

[0050] The activation process for ZSM-5 molecular sieve is the same as in Example 1.

[0051] Example 4

[0052] A choline chloride cation (CH3)3CH2CH2OHN + The modified ZSM-5 molecular sieve is synthesized as follows:

[0053] 1 g of activated ZSM-5 molecular sieve was added to 50 mL of 15.55 g / L choline chloride aqueous solution and reacted at 80 °C for 6 hours. The product obtained after the reaction was washed and filtered with deionized water. The filtered material was heated to 100 °C at a rate of 5 °C / min in a muffle furnace and held at this temperature for 2 hours, then heated to 200 °C at a rate of 5 °C / min and held at this temperature for 4 hours, and then cooled to 30 °C at a rate of 5 °C / min. The resulting material was designated TZEO-4#, with pore sizes concentrated in the following areas: By mass ratio, ZSM-5 molecular sieve: quaternary ammonium salt cation = 100: 5.2.

[0054] The activation process for ZSM-5 molecular sieve is the same as in Example 1.

[0055] Example 5

[0056] A tetraethylammonium ion (C2H5)4N + The modified ZSM-5 molecular sieve is synthesized as follows:

[0057] 1 g of activated ZSM-5 molecular sieve was added to 50 mL of a 24.38 g / L tetraethylammonium chloride aqueous solution and reacted at 80 °C for 7 hours. The product obtained after the reaction was washed and filtered with deionized water. The filtered material was heated to 100 °C at a rate of 5 °C / min in a muffle furnace and held at this temperature for 2 hours. Then, it was heated to 200 °C at a rate of 5 °C / min and held at this temperature for 4 hours. Finally, it was cooled to 30 °C at a rate of 5 °C / min. The resulting material was designated TZEO-5#, with pore sizes concentrated in the following areas: By mass ratio, ZSM-5 molecular sieve: quaternary ammonium salt cation = 100: 6.24.

[0058] The activation process for ZSM-5 molecular sieve is the same as in Example 1.

[0059] To illustrate the superiority of the present invention, the following comparative implementation examples were also provided. Variable analysis will be performed below based on Example 1.

[0060] Example 6

[0061] Compared with Example 1, in Example 6, the ZSM-5 molecular sieve was not activated before ion exchange, and other reaction conditions were the same as in Example 1.

[0062] Example 7

[0063] In Example 7, compared to Example 1, the ZSM-5 molecular sieve was heated to 300°C at a rate of 10°C / min, held at this temperature for 5 hours, and then cooled to 100°C at a rate of 10°C / min. Other reaction conditions were the same as in Example 1. In this Comparative Example 2, the activation temperature was insufficient.

[0064] Example 8

[0065] Compared with Example 1, in Example 8, after tetramethylammonium ion exchange, the residual exchange solution on the material surface was not cleaned with deionized water, and other reaction conditions were the same as in Example 1.

[0066] Example 9

[0067] Compared with Example 1, Example 9 did not involve drying the tetramethylammonium-modified ZSM-5 molecular sieve after filtration with deionized water, and the other reaction conditions were the same as in Example 1.

[0068] Example 10

[0069] Compared with Example 1, Example 10 increased the amount of ZSM-5 molecular sieve to 30 g / L, while other reaction conditions remained the same as in Example 1.

[0070] Example 11

[0071] Compared with Example 1, Example 11 reduced the amount of ZSM-5 molecular sieve to 5 g / L, while other reaction conditions remained the same as in Example 1.

[0072] Example 12

[0073] Compared with Example 1, Example 12 increased the concentration of tetramethylammonium chloride aqueous solution to 30 g / L, while other reaction conditions remained the same as in Example 1.

[0074] Example 13

[0075] Compared with Example 1, the tetramethylammonium chloride aqueous solution in Example 13 was reduced to 1.25 g / L, while other reaction conditions were the same as in Example 1.

[0076] Example 14

[0077] Compared with Example 1, Example 14 uses tetrabutylammonium chloride with a cation size larger than that of ZSM-5 to replace the aqueous solution of tetramethylammonium chloride. The reaction is carried out at 110°C for 10 hours, and other reaction conditions are the same as those in Example 1.

[0078] The synthesized material was subjected to relevant tests, and the results are shown below.

[0079] This application uses a Bruker D8-ADVANCE fully automated X-ray diffractometer (Germany) to perform X-ray powder diffraction analysis on the TZEO-1# molecular sieve prepared in the example of this invention, and compares it with the ZSM-5 molecular sieve raw material to determine the changes in the crystal structure of the material after ion exchange. Figure 1 The figures show the XRD patterns of the TZEO-1# molecular sieve material and the ZSM-5 molecular sieve raw material obtained in Example 1. As can be seen from the figures, the XRD patterns of the materials remained essentially unchanged after tetramethylammonium ion exchange, indicating that the ion exchange had no effect on the crystal structure of the molecular sieve.

[0080] This application uses a 3-Flex multi-functional adsorption analyzer manufactured by Micromeritics, USA, to characterize the adsorption performance of the materials obtained in the embodiments and comparative examples of this invention for monochloropentafluoroethane and octafluoropropane gases. The static adsorption isotherm of the materials at 298 K was tested using the volumetric method. Figure 2 The figure shows the adsorption isotherm of pentachlorofluoroethane / octafluoropropane for the TZEO-1# molecular sieve material obtained in Example 1 at 298 K. Analysis of the figure reveals that while the material exhibits a low adsorption capacity for octafluoropropane, the isotherm for pentachlorofluoroethane in the low-pressure region remains very steep, with a gas adsorption ratio of 3.257 at 101.325 kPa, demonstrating its ability to extract high-purity octafluoropropane from a pentachlorofluoroethane / octafluoropropane mixture. Figure 3 The figure shows the adsorption isotherm of TZEO-2# molecular sieve material obtained in Example 2 for chloropentafluoroethane / octafluoropropane at 298 K. Analysis of the figure reveals that although the adsorption capacity for chloropentafluoroethane is higher than in Example 1, its adsorption capacity for octafluoropropane is significantly higher. This indicates that reducing the amount of tetramethylammonium ions in Example 2 results in less pore shrinkage compared to Example 1, leading to less inhibition of octafluoropropane adsorption and lower separation performance for chloropentafluoroethane / octafluoropropane compared to Example 1. This also demonstrates that the TZEO-1# molecular sieve synthesized in Example 1 is the most ideal and efficient material for separating and purifying chloropentafluoroethane / octafluoropropane.

[0081] The adsorbent materials synthesized in Examples 1-14 were applied to the adsorption of pentachlorofluoroethane and octafluoropropane. The adsorption effects are shown in Table 1.

[0082] Table 1. Adsorption capacity and adsorption-separation ratio of chloropentafluoroethane and octafluoropropane for various materials under 298 K and 101.325 kPa conditions.

[0083]

[0084] As can be seen from Table 1 above, Example 1 is the preferred synthesis scheme.

[0085] A comparison of Examples 6 and 7 with Example 1 shows that failure to activate the ZSM-5 molecular sieve or using a low activation temperature results in insufficient removal of the template agent within the molecular sieve, thereby hindering the formation of tetramethylammonium ions (CH3)4N. + It enters the molecular sieve channels and undergoes a displacement reaction with hydrogen atoms, resulting in a decrease in the C2ClF5 / C3F adsorption and separation ratio.

[0086] As can be seen from the comparison between Example 8 and Example 1, when the residual exchange solution on the material surface was not cleaned with deionized water in Example 8, the pores on the material surface were blocked, resulting in a lower adsorption capacity of the target component C2ClF5 and a decrease in the C2ClF5 / C3F8 adsorption-separation ratio.

[0087] As can be seen from the comparison between Example 9 and Example 1, when the tetramethylammonium modified ZSM-5 molecular sieve filtered with deionized water in Example 9 was not dried, most of the molecular sieve pores were occupied by water, resulting in a lower adsorption capacity of the target component C2ClF5 and a decrease in the C2ClF5 / C3F8 adsorption-separation ratio.

[0088] A comparison of Examples 10 and 11 with Example 1 shows that when the amount of ZSM-5 molecular sieve in Example 10 was increased to 30 g / L, the pore size of the material did not decrease significantly, thus maintaining a high adsorption capacity for C3F8. However, when the amount of ZSM-5 molecular sieve in Example 11 was reduced to 5 g / L, the pore size of the material decreased significantly, but the adsorption capacity for the target component C2ClF5 decreased. This demonstrates that an appropriate amount of ZSM-5 molecular sieve can achieve a suitable content of tetramethylammonium ions, resulting in a material that maintains a low adsorption capacity for C3F8 while still exhibiting a high adsorption capacity for the target component C2ClF5.

[0089] A comparison of Examples 12 and 13 with Example 1 shows that when the tetramethylammonium chloride aqueous solution concentration was increased to 30 g / L in Example 12, the pore size of the material was significantly reduced. Even with more tetramethylammonium chloride ions present in the pores, the adsorption capacity of the material for the target component C2ClF5 was very low due to the reduced pore volume. In Example 13, when the tetramethylammonium chloride aqueous solution concentration was reduced to 1.25 g / L, the pore size of the material did not shrink significantly, and the number of tetramethylammonium chloride ions in the pores was low, making it impossible to enhance the adsorption of the target impurity C2ClF5 through FH interaction. Therefore, an appropriate quaternary ammonium salt solution can introduce appropriate tetramethylammonium chloride ions into the pores to interact with the target component without significantly reducing the pore volume of the material.

[0090] A comparison of Example 14 and Example 1 shows that when tetrabutylammonium chloride was used instead of tetramethylammonium chloride aqueous solution in Example 14, and the temperature and time of ion exchange were increased, the adsorption and separation performance of the material for C2ClF5 / C3F8 was not improved. This is because the size of tetrabutylammonium ions is significantly larger than the pore size of ZSM-5, and even with higher reaction temperatures and times, they cannot overcome steric hindrance to enter the ZSM-5 pores.

[0091] This application uses a GC6600 gas chromatograph from Shanghai Fanwei Chromatography Instrument Equipment Co., Ltd. to build a self-assembled experimental setup for fixed-bed adsorption and permeation experiments of materials in a chloropentafluoroethane / octafluoropropane (volume ratio 1:9999) mixture at room temperature and pressure. The dynamic adsorption curves of 1 g of the material TZEO-1# synthesized in Example 1 for a chloropentafluoroethane:octafluoropropane mixture at a volume ratio of 1:9999 (1 g / v) were recorded. Figure 4 The outlet gas concentration refers to the gas concentration at the outlet after the crude octafluoropropane mixture has passed through the TZEO-1# material for adsorption. Figure 4 It can be seen that TZEO-1# has a short retention time for octafluoropropane, indicating that the material has a low adsorption capacity for octafluoropropane. Meanwhile, the material exhibits a high adsorption capacity for pentachlorofluoroethane, as it takes 121 minutes for pentachlorofluoroethane to permeate. Overall, TZEO-1# material demonstrates superior adsorption selectivity for pentachlorofluoroethane / octafluoropropane.

[0092] It should be understood that the above detailed description of the technical solutions of the present invention with reference to optimized embodiments is illustrative and not restrictive. It should not be considered that the specific implementation of the present invention is limited to this. For those skilled in the art, any modifications to the technical solutions described in the embodiments or equivalent substitutions of some technical features without departing from the concept of the present invention should be considered as falling within the scope of patent protection defined by the claims submitted by the present invention.

[0093] The above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a quaternary ammonium salt modified molecular sieve for adsorbing and purifying the electron gas octafluoropropane, characterized in that, The process includes the following steps: (1) activating the ZSM-5 molecular sieve, wherein the activation process includes: heating the ZSM-5 molecular sieve to 550℃~650℃ at a rate of 10℃ / min and maintaining it at that temperature for 5 hours, and then cooling it to 100℃ at a rate of 10℃ / min; (2) adding the quaternary ammonium salt to the aqueous solution and stirring it at a first preset temperature of 25℃~55℃ for a first preset time of 20~50 minutes until the quaternary ammonium salt is completely dissolved, thereby obtaining a clear quaternary ammonium salt aqueous solution; (3) adding the activated ZSM-5 molecular sieve powder obtained in step (1) to the solution obtained in step (2). The quaternary ammonium salt aqueous solution is continuously stirred in a water bath at a second preset temperature of 50℃~110℃ for a second preset time of 3~9 hours, then filtered, and the filter cake is washed with sufficient water to remove residual quaternary ammonium salt on the surface, and finally dried to obtain quaternary ammonium salt modified molecular sieve; wherein, the quaternary ammonium salt modified molecular sieve includes ZSM-5 molecular sieve framework and quaternary ammonium salt cation, the quaternary ammonium salt cation is adsorbed in the pores of the ZSM-5 molecular sieve through a single ion exchange process, and distributed in the cross cavity of straight pores and sinusoidal pores; by mass ratio, ZSM-5 molecular sieve framework: quaternary ammonium salt cation = 100: 3.5~9.

5.

2. The preparation method according to claim 1, characterized in that, In step (2), the quaternary ammonium salt is any one of tetramethylammonium chloride, choline chloride, and tetraethylammonium chloride.

3. The preparation method according to claim 1, characterized in that, In step (2), the concentration of the quaternary ammonium salt aqueous solution is 5~55 g / L.

4. The preparation method according to claim 1, characterized in that, In step (3), the amount of ZSM-5 molecular sieve powder used is 0.016~0.024 g / mL of quaternary ammonium salt aqueous solution.

5. The preparation method according to claim 1, characterized in that, In step (3), the drying operation includes: heating the filtered and washed product to 100℃~110℃ at a rate of 5℃ / min, holding for 2 hours, then heating to 195℃~205℃ at a rate of 5℃ / min, holding for 4 hours, and finally cooling to 30℃~35℃ at a rate of 5℃ / min.

6. A quaternary ammonium salt modified molecular sieve prepared by the preparation method according to any one of claims 1-5.

7. The application of the quaternary ammonium salt modified molecular sieve according to claim 6 in the adsorption and purification of the electron gas octafluoropropane.

8. The application according to claim 7, characterized in that, Using the quaternary ammonium salt modified molecular sieve to treat crude octafluoropropane gas containing 100 ppm monochloropentafluoroethane can achieve a purity of 99.99999% (7N grade) for the octafluoropropane, and 61.83 liters of 7N grade octafluoropropane product can be obtained per kilogram of the quaternary ammonium salt modified molecular sieve.

Images