Ionic liquid modified molecular sieve preparation method, molecular sieve and application

Abstract

The invention discloses an ionic liquid modified molecular sieve preparation method, a molecular sieve and application, and the preparation method comprises the following steps: preparing a mixed system formed by mixing an activated molecular sieve, an ionic liquid and alcohol; and mixing a proper amount of molecular sieves with the mixed system, stirring, removing ethanol, and performing activation and regeneration. According to the technical scheme, the abundant hydrogen bond network structure of the proper amount of ionic liquid is combined with the molecular sieve, the usage amount of the ionic liquid with high value is reduced, and the adsorption effect of the molecular sieve on HF is greatly improved through combination of the ionic liquid and the molecular sieve.

Description

Technical Field

[0001] The present invention belongs to the technical field of fluorochemical industry, and particularly relates to a preparation method of an ionic liquid-modified molecular sieve, a molecular sieve and an application thereof. Background Art

[0002] Hydrogen fluoride (HF) is the basis of modern fluorochemical industry and is the most basic raw material for preparing elemental fluorine, various fluorine refrigerants, fluorine-containing new materials, inorganic fluorinated salts, various organic fluorides and other materials. When HF exists as an impurity component in the product synthesis process, the current main treatment methods include compression condensation, wet absorption and dry adsorption. The compression condensation method utilizes the property that HF has different saturated vapor pressures at different temperatures, and reduces the system temperature or increases the system pressure to condense the HF in the vapor state and separate it from the mixture. The wet absorption treatment of HF can be divided into physical absorption and chemical absorption. Using water as an absorbent is to remove HF by utilizing the property that HF is easily soluble in water, which belongs to physical absorption. Using the reaction between HF and an alkaline solution to treat HF belongs to chemical absorption. When treating HF by dry adsorption, it is achieved by the selective adsorption of different adsorbents to HF. However, in these methods, there is an applicable range for compression condensation, and the separation effect can only be achieved by considering the physical property differences of substances; while the HF absorbed by the wet absorption treatment generates salts and acidic wastewater, and the treatment of wastewater and salts generally requires special treatment, which incurs additional costs, increases the production cost, and also introduces a large amount of water for re-treatment for high-purity products; while dry adsorption treatment is currently the most widely used in separating products, and while the HF in the product can be separated, the HF can also be recovered and purified as a by-product, but this requires a certain requirement for the adsorption capacity of the molecular sieve used in dry adsorption, and sometimes more for the adsorption performance of trace HF, but the current levels are all relatively low.

[0003] Currently, in the adsorption field, ionic liquids are widely used in the gas field. Ionic liquids themselves have the advantages of low volatility, high chemical stability and good chelating ability. However, the high price, large viscosity and large dosage of ionic liquids limit their large-scale application. Therefore, by using the adsorption or grafting immobilization method, the ionic liquid is loaded onto an inorganic porous material or an organic polymer material, so that the characteristics of the ionic liquid can be transferred to the carrier material without changing the properties of the carrier material. Therefore, not only can the dosage of the ionic liquid be greatly reduced, the cost can be reduced, but also it is beneficial to expand the adsorption surface area and thus promote the reaction process. Most of the commercial imidazole ionic liquids in ionic liquids are in the liquid phase, and in the subsequent calcination process, the ionic liquid loses its original function.

[0004] Therefore, in view of the above technical problems, it is necessary to provide a preparation method of an ionic liquid-modified molecular sieve, a molecular sieve and an application thereof.

[0005] The information disclosed in this background art section is only intended to enhance the overall understanding of the background of the present invention and should not be regarded as an admission or any form of implication that this information constitutes prior art already known to those of ordinary skill in the art. Summary of the Invention

[0006] An object of the present invention is to provide a method for preparing an ionic liquid-modified molecular sieve, a molecular sieve, and an application thereof.

[0007] To achieve the above object, the technical solution provided by a specific embodiment of the present invention is as follows:

[0008] A method for preparing an ionic liquid-modified molecular sieve, comprising the following steps:

[0009] Prepare an activated molecular sieve and a mixed system formed by mixing an ionic liquid and an alcohol;

[0010] Mix an appropriate amount of the molecular sieve with the mixed system, stir, then remove ethanol, and then carry out activation regeneration.

[0011] In one or more embodiments of the present invention, the activation conditions of the molecular sieve are: air atmosphere, 300°C - 500°C, 3 - 4 h.

[0012] In one or more embodiments of the present invention, the molecular sieve is selected from: SBA-15 molecular sieve.

[0013] In one or more embodiments of the present invention, the ionic liquid is selected from: phosphonium-based ionic liquids. Preferably, the phosphonium-based ionic liquid is synthesized by a one-step method:

[0014] The cation includes: tributylpropylphosphine, abbreviated as [P 4443 +

[0015] The anion includes Cl - , Br - , BF4 - , PF6 - , TFSI - etc.

[0016] After being detected by a melting point instrument, the melting points of [P 4443 Br, [P 4443 BF4, [P 4443 PF6, [P 4443 TFSI are 102°C, 114°C, 128°C, and 138°C respectively.

[0017] In one or more embodiments of the present invention, the alcohol is selected from: monohydric alcohols with 4 or less carbon atoms. Preferably, the alcohol is selected from: ethanol, methanol, n-propanol, isopropanol, n-butanol. ​

[0018] In one or more embodiments of the present invention, the ratio of the ionic liquid to the alcohol in the mixed system is wt: (0.01 to 1): 1.

[0019] In one or more embodiments of the present invention, the mixing ratio of the molecular sieve to the mixed system is wt: (0.01 to 1): 1.

[0020] In one or more embodiments of the present invention, the stirring conditions are: stirring at normal pressure for 0 to 12 h at 10 rpm to 300 rpm and 30 °C to 50 °C.

[0021] In one or more embodiments of the present invention, the activation and regeneration conditions are: after alternating cycles of helium purging and vacuum pumping, pressurize to 0.5 bar - 0.9 bar, and keep the temperature and pressure at 70 °C to 90 °C for 5 h to 8 h. Preferably, the helium purging conditions are: helium to 0.7 - 0.8 bar, and the single purge time does not exceed 0.5 h.

[0022] Preferably, the helium purging conditions:

[0023] ① Flow rate: 100 mL / min to 500 mL / min, preferably 200 mL / min to 350 mL / min;

[0024] ② Temperature: 25 °C to 150 °C, preferably 70 to 90 °C;

[0025] ③ Pressure 0.5 - 1.2 bar, preferably 0.7 to 0.9 bar.

[0026] Preferably, for vacuum pumping: the vacuum degree is 85 - 95 kPa, preferably 90 - 95 kPa.

[0027] Preferably, the number of alternating cycles of helium purging and vacuum pumping is 2 - 8 times. Further preferably, the alternating cycles are 5 - 6 times, and pressure needs to be maintained for 0 - 2 h before vacuum pumping, preferably 0.5 - 1.5 h.

[0028] In one or more embodiments of the present invention, the molecular sieve is obtained by a preparation method of a molecular sieve modified by an ionic liquid.

[0029] In one or more embodiments of the present invention, the application of the molecular sieve in HF dry adsorption.

[0030] Compared with the prior art, the preparation method, the molecular sieve and the application of the molecular sieve modified by an ionic liquid of the present invention utilize the rich hydrogen bond network structure of an appropriate amount of ionic liquid to combine with the molecular sieve, not only reducing the usage amount of the relatively expensive ionic liquid itself, but also greatly improving the adsorption effect of the molecular sieve on HF by the combination of the two. Description of the Drawings

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 It is a comparison diagram of the energy adsorption of the embodiments of the present invention and the comparative example. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0034] A specific modified SBA-15 molecular sieve of the present invention is prepared by taking quaternary phosphine ionic liquid as an example:

[0035] 1) Select a certain amount of SBA-15 molecular sieve and activate it at 300℃-500℃;

[0036] 2) Mixing a quaternary phosphine ionic liquid with a certain amount of alcohol such as ethanol, the ratio of ionic liquid:alcohol is between 0.01 and 1; after the ionic liquid is fully dissolved in the alcohol, adding a certain amount of activated SBA-15 molecular sieve to the quaternary phosphine ionic liquid / alcohol mixed system, the ratio of ionic liquid / alcohol mixed system:molecular sieve is between 0.01 and 1;

[0037] 3) The stirring rate is between 10 rpm and 300 rpm;

[0038] 4) The stirring temperature is between 30°C and 50°C;

[0039] 5) The stirring time under normal pressure is 0 to 12 hours;

[0040] 6) After a certain stirring time, vacuum (vacuum degree 90-95kpa) is applied at a temperature of 50℃~70℃ under negative pressure for 3~5h to remove the alcohol in the molecular sieve and take out the obtained product. Under the alternating use of helium blowing / vacuum, the pressure is filled to 0.5bar-0.9bar, and the activation regeneration is carried out at about 70℃~90℃ for 5h~8h, and the obtained product is ready for use.

[0041] Including but not limited to the following embodiments, the preparation of ionic liquids can be correspondingly carried out by the following methods, and of course other feasible schemes can also be adopted:

[0042] Preparation of tributylpropylphosphonium bromide ([P4443]Br):

[0043] Under N2 protection, 20 mL of anhydrous toluene was added to a three-necked flask, and 5 g of 1-bromopropane was added. After stirring continuously for 20 min, tributylphosphine (0.053 mol) was injected into the reaction flask through a syringe. The temperature was raised to 80 °C and stirring was continued for 24 h. After the reaction was completed, the excess toluene and 1-bromopropane were removed by evaporation. The obtained sample was dried at 110 °C under a vacuum of kPa for 5 h, and the resulting oily liquid was tributylpropylphosphonium bromide ([P4443]Br).

[0044] Preparation of tributylpropylphosphonium tetrafluoroborate ([P4443][BF4]):

[0045] An excess of sodium tetrafluoroborate was weighed, and sodium tetrafluoroborate and tributylpropylphosphonium bromide (n(NaBF4):n([P4443]Br) = 1.5) were added to acetonitrile and mixed thoroughly. The reaction was carried out at room temperature for 24 h at a rotation speed of 500 r / min. The obtained sample was filtered to remove the excess sodium tetrafluoroborate, and the filtration was repeated with acetonitrile. The obtained filtrate was titrated with silver nitrate solution until no precipitate appeared. Then, the obtained filtrate was evaporated to remove acetonitrile. The obtained sample was dried under vacuum at 80 °C for 5 h, and the resulting white solid particles were tributylpropylphosphonium tetrafluoroborate ([P4443][BF4]).

[0046] Preparation of tributylpropylphosphonium hexafluorophosphate ([P4443][PF6]):

[0047] An excess of potassium hexafluorophosphate was weighed, and potassium hexafluorophosphate and tributylpropylphosphonium bromide (n(NaBF4):n([P4443]Br) = 1.5) were added to acetonitrile and mixed thoroughly. The subsequent steps were the same as those for the preparation of tributylpropylphosphonium tetrafluoroborate. The obtained white solid was washed and filtered repeatedly with acetonitrile. The obtained filtrate was titrated with silver nitrate solution until no precipitate appeared. Then, the obtained filtrate was filtered to remove acetonitrile, and the obtained product was tributylpropylphosphonium hexafluorophosphate ([P4443][PF6]).

[0048] Preparation of tributylpropylphosphonium bis(trifluoromethanesulfonyl)imide [P 4443 TFSI:

[0049] Weigh an excess of sodium bis(trifluoromethanesulfonyl)sulfonate, add sodium bis(trifluoromethanesulfonyl)sulfonate and tributylpropylphosphine bromide (n(NaTFSI):n([P4443]Br)=1.5) to acetonitrile and mix thoroughly. The subsequent steps are the same as those for preparing tributylpropylphosphine tetrafluoroborate. The obtained white solid is repeatedly washed with acetonitrile and filtered. The obtained filtrate is calibrated with a silver nitrate solution until no precipitate appears. The obtained filtrate is filtered to remove the acetonitrile. The obtained product is tributylpropylphosphine hexafluorophosphate ([P4443][PF6]).

[0050] Embodiment 1:

[0051] Weigh a certain amount of finished SBA-15 molecular sieve (purchased from manufacturer: Xianfeng Nano, the same below), regenerate it in a muffle furnace at 300°C for 3 hours and set it aside. Take 5g of the synthesized ionic liquid tributylpropylphosphine tetrafluoroborate, recorded as [P 4443 ][BF4]; dissolved in 100g ethanol, stirred at 40℃ with a speed of 100ppm for 1h to fully dissolve, then added 50g SBA-15 molecular sieve that had been activated, and continued to stir at 40℃ for 6h. After full impregnation, vacuumed at 60℃ under negative pressure (vacuum degree 90kpa) for 4h to remove most of the ethanol. Regenerated by alternately vacuuming / filling with helium at 60℃ for 6h, first vacuumed (vacuum degree 90kpa) for 1h, then filled with helium to 0.8bar and maintained at pressure for 0.5h, repeated 4 times, to obtain a modified product, recorded as BFPIL-SBA-15.

[0052] Embodiment 2:

[0053] Weigh a certain amount of finished SBA-15 molecular sieve and regenerate it in a muffle furnace at 300°C for 3.5 hours before use. Take 5 g of the synthesized ionic liquid tributyl propylphosphine hexafluorophosphate, denoted as [P 4443 ][PF6]; dissolved in 60g ethanol, stirred at 50℃ with a speed of 150ppm for 1h to fully dissolve, then added 50g SBA-15 molecular sieve that has been activated, and continued to stir at 40℃ for 6h. After full impregnation, vacuumed at 60℃ for 4h (vacuum degree 92kpa) to remove most of the ethanol. Regenerated by alternating vacuuming / filling with helium at 60℃ for 6h, first vacuuming (vacuum degree 92kpa) for 1h, then filling with helium to 0.7bar and maintaining the pressure for 0.5h, repeated 4 times, recorded as PFPIL-SBA-15.

[0054] Embodiment 3:

[0055] Weigh a certain amount of finished SBA-15 molecular sieve and regenerate it in a muffle furnace at 300°C for 3 hours before use. Take 5 g of the synthesized ionic liquid tributyl propyl phosphonium bromide, denoted as [P 4443Br; It was dissolved in 150 g of ethanol and stirred at a rotation speed of 150 ppm at 50 °C for 1 h for sufficient dissolution. Then, 50 g of activated SBA-15 type molecular sieve was added, and stirring was continued at 500 °C for 6 h. After sufficient impregnation, negative pressure evacuation (vacuum degree 90 kPa) was carried out at 70 °C for 6 h to remove most of the ethanol. Then, regeneration was carried out by alternately operating vacuum evacuation / helium filling at 60 °C for 6 h. First, vacuum evacuation (vacuum degree 90 kPa) was carried out for 1 h, and then helium was filled to 0.7 bar for pressure holding for 0.5 h. After repeating 4 times, it was denoted as BrPIL-SBA-15.

[0056] Comparative Example 1:

[0057] Directly use the commercially purchased SBA-15 molecular sieve for adsorption test: SBA-15, manufacturer: Xianfeng Nano Comparative Example 2:

[0058] Directly use the commercially purchased SBA-15 molecular sieve for adsorption test: SBA-15, manufacturer: Jicang Nano Comparative Example 3:

[0059] Weigh a certain amount of the finished SBA-15 type molecular sieve, and use it after regeneration at 300 °C in a muffle furnace for 3 h. Take 5 g of the synthesized ionic liquid tributylpropylphosphonium bis(trifluoromethanesulfonyl)imide, denoted as [P 4443 TFSI; It was dissolved in 1000 g of ethanol and stirred at a rotation speed of 150 ppm at 50 °C for 1 h for sufficient dissolution. Then, 50 g of activated SBA-15 type molecular sieve was added, and stirring was continued at 40 °C for 7 h. After sufficient impregnation, negative pressure evacuation (vacuum degree 90 kPa) was carried out at 70 °C for 4 h to remove most of the ethanol. Then, regeneration was carried out by alternately operating vacuum evacuation / helium filling at 90 °C for 6 h. First, vacuum evacuation (vacuum degree 90 kPa) was carried out for 1 h, and then helium was filled to 0.8 bar for pressure holding for 0.5 h. After repeating 4 times, it was denoted as TFSIPIL-SBA-15.

[0060] Comparative Example 4:

[0061] Only weigh 10 g of the prepared tributylpropylphosphonium hexafluorophosphate [P 4443 [PF6] for adsorption test.

[0062] Comparative Example 5

[0063] Weigh a certain amount of the finished product SBA-15 molecular sieve, regenerate it at 300 °C in a muffle furnace for 3 h and then set it aside for use. Take 5 g of commercially available 1-butyl-3-methylimidazolium bromide (purchased from Suzhou Haofan Biotech), denoted as [BMIM]Br; dissolve it in 800 g of ethanol, stir at a rotation speed of 100 ppm at 50 °C for 1 h until fully dissolved, add 50 g of the activated SBA-15 molecular sieve, and continue to stir at 50 °C for 6 h. After sufficient impregnation, carry out negative pressure vacuuming (vacuum degree 90 kPa) at 70 °C for 4 h to remove most of the ethanol. Then carry out regeneration by alternately operating vacuuming / helium filling at 60 °C for 12 h. First, vacuum (vacuum degree 90 kPa) for 1 h, then fill helium to 0.8 bar and keep the pressure for 0.5 h, repeat 8 times, and denote it as BrBIL-SBA-15.

[0064] Comparative Example 6

[0065] Weigh a certain amount of the finished product SBA-15 molecular sieve, regenerate it at 300 °C in a muffle furnace for 3 h and then set it aside for use. Take 5 g of commercially available 1-butyl-3-methylimidazolium hexafluorophosphate (purchased from Suzhou Haofan Biotech), denoted as [BMIM][PF6]; dissolve it in 300 g of ethanol, stir at a rotation speed of 100 ppm at 60 °C for 1 h until fully dissolved, add 50 g of the activated SBA-15 molecular sieve, and continue to stir at 70 °C for 6 h. After sufficient impregnation, carry out negative pressure vacuuming (vacuum degree 90 kPa) at 95 °C for 4 h to remove most of the ethanol. Then carry out regeneration by alternately operating vacuuming / helium filling at 95 °C for 6 h. First, vacuum (vacuum degree 90 kPa) for 1 h, then fill helium to 0.8 bar and keep the pressure for 0.5 h, repeat 4 times, and denote it as PFBIL-SBA-15.

[0066] Adsorption test process:

[0067] Apply the samples of the above examples and comparative examples to separate HF in CH3F. Take 10 g of the sample molecular sieve and fill it into an adsorption column with a diameter of 1 / 4 inch and a length of 20 cm. Use a mass flow meter to control the flow rate at 300 ml / min, with an empty space velocity of 50 h -1 Pass the CH3F standard gas containing 5 ppm HF into the adsorption column, control the adsorption pressure at 0.5 - 1 Mpa, and the adsorption temperature at -25 °C to -15 °C. Chromatographically detect the gas after passing through the adsorption column, and define the breakthrough of HF in the adsorption column when the HF content reaches 0.5 ppm.

[0068] Table 1 HF adsorption experiment results of each example and comparative example

[0069]

[0070] Test results: The adsorption experiment results of each example and comparative example are shown in Figure 1and Table 1. Comparing the modified SBA-15 molecular sieves in the examples with the comparative examples, the SBA-15 molecular sieve modified with tributylpropylphosphonium hexafluorophosphate showed a higher adsorption capacity and a longer adsorption breakthrough time.

[0071] Among them, the adsorption capacities of Example 2 were 2.65 times and 2.79 times those of Comparative Examples 1 and 2, respectively, and the performance was significantly better than that of the SBA-15 molecular sieves on the current market. Comparing Example 1, Example 2, Example 3, and Example 4, the SBA-15 molecular sieve modified with [P4443]PF6 was significantly better than the molecular sieves modified with other ionic liquids. The main reason was that according to the simulation, the molecular sizes of [P4443]Br, [P4443]BF4,

[0072] [P4443]PF6, and [P4443]TFSI were and [P4443]PF6 had a moderate size. At the same time, the hydrogen bond network formed by it in the pores of SBA-15 was denser. The reason why [P4443]TFSI had worse performance after modification was mainly because the molecular size of [P4443]TFSI was too large, which had a pore-blocking effect on the molecular sieve. For the pure ionic liquid tributylpropylphosphonium hexafluorophosphate [P 4443 [PF6], when it was filled into the adsorption column in the same amount for the adsorption experiment, due to the density problem, the adsorption column was not filled completely, and the adsorption effect on HF was not ideal. Compared with imidazole-based ionic liquids, the SBA-15 modified with [BMIM]Br did not improve in adsorption performance because it could not form hydrogen bond interactions and even played a pore-blocking role. The SBA-15 modified with [BMIM][PF6] had slightly better performance in improving SBA-15 due to the weak hydrogen bond interaction of the anion. However, limited by the structural problems of ionic liquids, the efficacy of imidazole-based ionic liquids was inferior to that of quaternary phosphonium-based ionic liquids.

[0073] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention.

[0074] In addition, it should be understood that although this specification is described in terms of embodiments, not every embodiment contains only an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A preparation method of an ionic liquid-modified molecular sieve, comprising the following steps: Prepare an activated molecular sieve and a mixed system formed by mixing an ionic liquid and an alcohol; Mix and stir an appropriate amount of the molecular sieve with the mixed system, then remove ethanol and perform activation regeneration.

2. The method for preparing an ionic liquid-modified molecular sieve according to claim 1, wherein The activation conditions of the molecular sieve are: in an air atmosphere, 300°C - 500°C, for 3 - 4 h.

3. The preparation method of the ionic liquid-modified molecular sieve according to claim 1, characterized in that, The molecular sieve is selected from: SBA-15 molecular sieve.

4. The preparation method of the ionic liquid-modified molecular sieve according to claim 1, wherein The ionic liquid is selected from: phosphonium-based ionic liquids.

5. The preparation method of the ionic liquid-modified molecular sieve according to claim 1, characterized in that, The alcohol is selected from: monohydric alcohols with 4 or fewer carbon atoms.

6. The preparation method of the ionic liquid-modified molecular sieve according to claim 1, characterized in that, The ratio of the ionic liquid to the alcohol in the mixed system is, wt: (0.01 - 1):

1.

7. The preparation method of the ionic liquid-modified molecular sieve according to claim 1, wherein, The mixing ratio of the molecular sieve to the mixed system is, wt: (0.01 - 1):

1.

8. The preparation method of the ionic liquid-modified molecular sieve according to claim 1, characterized in that, The stirring conditions are: stirring at 10 rpm - 300 rpm and 30°C - 50°C under normal pressure for 0 - 12 h.

9. A molecular sieve obtained by the preparation method of an ionic liquid-modified molecular sieve according to any one of claims 1 - 8.

10. Use of the molecular sieve according to claim 9 in HF dry adsorption.

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