Preparation method and application of a hybrid silicone / mof-303 matrix membrane

Abstract

The application relates to a preparation method and application of a silicone / MOF-303 mixed matrix membrane. A silicon source precursor is uniformly dissolved in an ethanol solvent, a mixture of water and hydrochloric acid is added in a certain proportion, water bath heating is carried out for a period of time, and a silicone sol is obtained. MOF-303 powder prepared in advance is added into the silicone sol in a certain proportion, ultrasonic mixing is carried out to obtain a separation layer sol, the prepared separation layer sol is coated on a ceramic support through a hot coating method, and calcination is carried out in an air atmosphere for a period of time to obtain a MOF-303 / mixed matrix membrane. The application preferably uses an organic silicone substance BTESA with a rigid acetylene bridge structure as a precursor, and the MOF-303 material with a high specific surface area is doped into the precursor, the pore structure of the membrane is modified, and more adsorption sites are provided for water molecules. Through optimization of the composite proportion, a composite membrane material with the best separation performance is obtained.

Description

Technical Field

[0001] This invention belongs to the field of membrane material preparation technology, specifically relating to the application of a MOF-303 mixed matrix membrane and its preparation method. Background Technology

[0002] Ethanol, isopropanol, and n-butanol are common products in the petrochemical industry. Currently, in actual production and separation processes, they are often miscible with water in a certain proportion. Therefore, achieving efficient dehydration of these mixtures is of great significance. Because these three alcohols have similar boiling points to water, they easily form azeotropes, making them difficult to separate using traditional methods and consuming a lot of energy. Pervaporation technology has attracted widespread attention because it is not limited by gas-liquid equilibrium and has low energy consumption. Organosilicon materials, due to their high specific surface area, adjustable pore size, good hydrothermal stability, and excellent chemical resistance, have been extensively studied in the field of pervaporation dehydration. BTESA, due to its large pore size and good hydrophilicity, exhibits satisfactory permeation flux in alcohol / water separation, but its selectivity is relatively low. MOF-303 membrane materials, due to their high water absorption (up to 500 cm³ at 303 K),... 3 g -1 This has attracted people's attention.

[0003] MOF-303 possesses an xhh topology, constructed from infinitely rod-shaped Al(OH)(-COO)₂ clusters linked by HPDC ligands. Within these clusters, octahedral coordinated Al(III) ions are bound together by four bridging carboxyl groups and two hydroxyl groups. MOF-303 exhibits a three-dimensional framework with one-dimensional (1D) rhombic channels (approximately 0.6 nm of open space) along its axis. The clusters and ligands endow these 1D channels with hydrophilic sites, facilitating rapid water molecule transport. Furthermore, the high pore volume and hydrophilic framework of MOF-303 also provide favorable conditions for the preferential adsorption of water molecules.

[0004] Therefore, how to incorporate MOF-303 into the bridging silicone membrane sol and prepare a defect-free separation layer, and how to improve the selectivity of the bridging silicone membrane without reducing its high flux by utilizing the high water absorption of MOF-303, is an urgent problem to be solved. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing and applying an organosilicon / MOF-303 hybrid matrix membrane.

[0006] To address the aforementioned technical problems, this invention provides the following technical solution: a method for preparing an organosilicon / MOF-303 hybrid matrix membrane and its application. It includes the following steps:

[0007] The silicon source precursor was uniformly dissolved in ethanol solvent, and then a mixture of water and hydrochloric acid was added in a certain proportion. The mixture was heated in a water bath for a period of time to obtain an organosilicon sol with a mass fraction of 1 wt% to 2.5 wt%.

[0008] The prepared MOF-303 powder was added to the organosilicon sol in a certain proportion and then mixed evenly by ultrasound to obtain the separation layer sol.

[0009] The prepared separation layer sol was applied to the ceramic support by hot coating and then calcined in air for a period of time to obtain the MOF-303 / mixed matrix membrane.

[0010] As a preferred embodiment of the application and preparation method of the MOF-303 mixed matrix membrane described in this invention, the silicon source precursor is 1,2-bis(triethoxysilyl)acetylene.

[0011] As a preferred embodiment of the preparation method and application of the organosilicon / MOF-303 mixed matrix membrane described in this invention, the molar ratio of silicon source precursor: H2O: HCl is 1:60-240:0.2, the reaction temperature is 40℃, and the reaction time is 2-4h.

[0012] As a preferred embodiment of the preparation method and application of the organosilicon / MOF-303 hybrid matrix membrane described in this invention, the MOF-303 is synthesized by a hydrothermal synthesis method, specifically as follows:

[0013] AlCl3·6H2O, H3PDC·H2O, and H2O were dissolved in a molar ratio of 1:1:2300 to prepare solution 1.

[0014] A certain amount of urea is dissolved in water and stirred until homogeneous. A certain amount of the urea aqueous solution is added to solution 1 to obtain solution 2, such that the molar ratio of AlCl3·6H2O:H3PDC·H2O:urea:H2O is 1:1:2.4:2300.

[0015] Solution 2 was heated in a reactor at 110°C for 16 hours to obtain MOF-303. MOF-303-urea powder was collected by vacuum filtration and washing, and then dried at 100°C overnight to obtain MOF-303 powder.

[0016] As a preferred embodiment of the preparation method and application of the organosilicon / MOF-303 hybrid matrix film of the present invention, the MOF-303 powder needs to be activated at 150°C for 2-4 hours before doping.

[0017] As a preferred embodiment of the preparation method and application of the organosilicon / MOF-303 mixed matrix film of the present invention, wherein the mass ratio of MOF-303 to organosilicon sol in the MOF-303 / organosilicon sol mixed sol is 0 to 0.1.

[0018] As a preferred embodiment of the preparation method and application of the organosilicon / MOF-303 hybrid matrix membrane described in this invention, the calcination temperature of the separation layer is 100-400℃, the calcination time is 20-40min, the coating concentration of the separation layer is 0.25wt%, and the process is repeated 2-3 times.

[0019] As a preferred embodiment of the preparation method and application of the organosilicon / MOF-303 hybrid matrix membrane described in this invention, the support used is an α-Al2O3 ceramic support with an average pore size of 1-2 nm.

[0020] As a preferred embodiment of the preparation method and application of the organosilicon / MOF-303 mixed matrix membrane described in this invention, the separation system includes ethanol / water, isopropanol / water, and n-butanol / water, and the operating temperature is 50-80℃.

[0021] The beneficial effects of this invention are as follows:

[0022] This invention selects BTESA precursor with rigid acetylene bridges as the silicon source. Due to its rigid bridging groups, the BTESA organosilicon membrane has a large pore size, thus exhibiting good permeation flux for alcohol / water systems. However, its loose pore structure also results in low selectivity. To improve the selectivity of the BTESA membrane, this invention introduces MOF-303 material with high water absorption. MOF-303 material has abundant -COO- and -OH groups, providing numerous adsorption sites for water molecules. Furthermore, MOF-303 has a three-dimensional framework with one-dimensional (1D) rhombic channels (approximately 0.6 nm of open space) along its axis. Clusters and ligands endow the 1D channels with hydrophilic sites, providing conditions for rapid water molecule transport. By incorporating MOF-303 into the BTESA organosilicon sol, additional sites and channels for water molecule transport are provided without altering the original organosilicon network structure, thereby improving the membrane's separation selectivity. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 FT-IR and XRD patterns of MOF-303 powder prepared by hydrothermal synthesis;

[0025] Figure 2 The water vapor adsorption spectrum of MOF-303 powder. Detailed Implementation

[0026] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0027] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0028] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0029] The separation performance of the organosilicon / MOF-303 hybrid matrix membrane prepared in this invention is usually evaluated by permeation flux and separation factor. The permeation flux and separation factor of the membrane can be obtained through corresponding calculations.

[0030] The formula for calculating permeation flux is as follows:

[0031]

[0032] The formula for calculating the separation factor is as follows:

[0033]

[0034] Example 1

[0035] This embodiment provides a method for preparing an organosilicon / MOF-303 hybrid matrix membrane and its application:

[0036] (1) Preparation of MOF-303

[0037] 0.722 g of aluminum chloride hexahydrate (AlCl3·6H2O) and 0.521 g of 3,5-pyrazole dicarboxylic acid monohydrate (H3PDC·H2O) were dissolved in 100 mL of deionized water to obtain mixed solution 1. 3.9 g of urea was dissolved in 30 g of deionized water to obtain mixed solution 2. 2.65 mL of solution 2 was added to solution 1 and mixed thoroughly. The mixture was heated at 110 °C for 16 hours. MOF-303-urea powder was collected by vacuum filtration and then dried overnight at 100 °C.

[0038] (2) Preparation of BTESA sol

[0039] 0.5 g of BTESA precursor was uniformly dispersed in 17.95 g of ethanol solution. A mixed solution of 0.01 g hydrochloric acid and 1.54 g water was added at a molar ratio of BTESA:H₂O:HCl = 1:60:0.2. The solution was stirred in a water bath at 40 °C for 2 h to obtain 2.5 wt% BTESA organosilicon sol.

[0040] (3) Preparation of BTESA / MOF-303 mixed sol

[0041] Before formal preparation, MOF-303 was activated at 150℃ for 4 hours. 12.5 mg of MOF-303 was dissolved in the prepared BTESA organosilicon sol, stirred for 1 hour, and ultrasonically dispersed for 30 minutes to obtain a uniformly dispersed BTESA / MOF-303 mixed sol.

[0042] (4) Preparation of BTESA / MOF-303 hybrid membrane

[0043] The prepared BTESA / MOF-303 mixed sol was diluted with ethanol to 0.25 wt%, and then the diluted sol was applied to a prepared ceramic support with a silica-zirconia nano-transition layer using a hot-coating method. The coated membrane was calcined in a tube furnace at 250 °C for 30 min, and this process was repeated three times to prepare a BTESA / MOF-303-2.5% hybrid membrane. The prepared membrane was used for pervaporation dehydration testing in a n-butanol / water system.

[0044] Example 2

[0045] The difference between this embodiment and embodiment 1 is that the doping amount of MOF-303 in step 3) is adjusted to 7.5wt%. Specifically, in step 2), 37.5mg of MOF-303 is dissolved in the prepared BTESA organosilicon sol. The remaining steps are the same as in embodiment 1 to obtain the film of this embodiment, which is denoted as BTESA / MOF-303-7.5%.

[0046] Example 3

[0047] The difference between this embodiment and embodiment 1 is that the doping amount of MOF-303 in step 3) is adjusted to 10wt%. Specifically, in step 2), 50mg of MOF-303 is dissolved in the prepared BTESA organosilicon sol. The remaining steps are the same as in embodiment 1 to obtain the film of this embodiment, which is denoted as BTESA / MOF-303-10%.

[0048] Comparative Example 1

[0049] The difference between this comparative example and Example 1 is that the BTESA sol obtained in step 2) was directly diluted to 0.25 wt% and coated onto the support to obtain the film of this comparative example, which is referred to as the original BTESA film.

[0050] The membranes prepared in Examples 1-3 and Comparative Example 1 were used for pervaporation dehydration tests in a n-butanol / water system. The specific implementation steps were performed according to the corresponding steps in Separation and Purification Technology, 2024, 344:12710. The feed solution composition was 95% butanol and 5% water. The feed solution temperature was controlled at 70°C. The obtained data were recorded in... Figure 1 middle.

[0051] Table 1. Pervaporation and dehydration performance of BTESA / MOF-303 membranes with different MOF-303 doping concentrations

[0052]

[0053]

[0054] As shown in Table 1, the flux and separation factor of the BTESA / MOF-303 hybrid matrix membrane both increased to varying degrees with increasing MOF-303 doping concentration. This is because MOF-303 material has abundant -COO- and -OH groups, providing numerous adsorption sites for water molecules and preferentially allowing water molecules to pass through during permeation. Furthermore, MOF-303 possesses a three-dimensional framework with one-dimensional (1D) rhombic channels (approximately 0.6 nm of open space) along its axis. Clusters and ligands endow the 1D channels with hydrophilic sites, providing conditions for rapid water molecule transport. In summary, the experimental results indicate that the incorporation of MOF-303 material can improve the separation performance of the original BTESA membrane for the n-butanol / water (95 / 5wt%) system.

[0055] Comparative Example 2

[0056] The difference between this comparative example and Example 1 is that the molar ratio in step 2) is changed to BTESA:H2O:HCl = 1:240:0.01, while the other steps are the same, and the membrane of this comparative example is obtained. This membrane is denoted as BTESA / MOF-801-2.5%.

[0057] Comparative Example 3

[0058] The difference between this comparative example and Example 1 is that the BTESA precursor in step 2 was replaced with a 1,2-bis(triethoxysilyl)ethylene (BTESEthy) precursor to prepare an organosilicon sol, which was then diluted to 0.25 wt% and coated onto a support to obtain the film of this comparative example, denoted as BTESEthy / MOF-303-2.5%.

[0059] Comparative Example 4

[0060] The difference between this comparative example and Example 1 is that the doping material in steps 2)-4) is replaced with MOF-801, while the other steps are the same, and the film of this comparative example is obtained. This film is denoted as BTESA / MOF-801-2.5%.

[0061] Following the aforementioned application method, the permeation flux and selectivity of the membranes prepared in Comparative Examples 2–4 at 70°C were measured, and the results are shown in Table 2.

[0062] Table 2. Performance of different membranes for pervaporation dehydration in n-butanol / water (95 / 5wt%) system.

[0063] membrane <![CDATA[Total flux (kgm -2 h -1 )]]> Separation factor Example 1 2.28 248 Comparative Example 1 2.20 171 Comparative Example 2 2.07 1062 Comparative Example 3 1.84 1329 Comparative Example 4 3.22 178

[0064] Table 2 shows that the type of organosilicon precursor and the preparation parameters of the organosilicon sol both affect the pervaporation performance of the membrane. Compared to the BTESA / MOF-303 membrane in Example 1, the organosilicon network formed by the BTESA precursor in Comparative Example 3 has a denser structure. After doping with MOF-303, the separation factor is improved due to its good water absorption, but the permeation flux is lower. Furthermore, by changing the ratio of the organosilicon sol, a BTESA / MOF-303 mixed matrix membrane with higher separation performance can be obtained. The separation effects of different doped materials were also compared. Although MOF-801 is also a hydrophilic filler, research data shows that its water absorption is not as good as MOF-303, and the improvement in separation performance after doping is not significant.

[0065] In summary, this invention provides a method for preparing and applying an organosilicon / MOF-303 hybrid matrix membrane. This invention preferably uses BTESA, an organosilicon-based material with a rigid acetylene bridge structure, as a precursor. MOF-303, a material with a high specific surface area and specific adsorption capacity for water molecules, is incorporated into it. This modifies the membrane's pore structure and provides more adsorption sites for water molecules, promoting the selective dissolution-diffusion of water molecules within the membrane network. While maintaining the original membrane network structure, this invention simultaneously improves the membrane's permeate flux and separation factor. By optimizing the composite ratio, a composite membrane material with optimal separation performance is obtained.

[0066] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing an organosilicon / MOF-303 hybrid matrix membrane, characterized in that: A silicon source precursor was uniformly dispersed in an ethanol solvent, and a mixed solution of hydrochloric acid and water was added in a certain proportion. The mixture was heated in a water bath at a certain temperature for a period of time to obtain an organosilicon sol. The prepared MOF-303 powder was added to the organosilicon sol in a certain proportion, and a uniformly mixed MOF-303 / bridge organosilicon sol was obtained by ultrasonication. The prepared MOF-303 / bridge organosilicon sol was coated onto a ceramic support by a hot coating method and calcined in air for a period of time to obtain an organosilicon / MOF-303 mixed matrix film. The silicon source precursor used was 1,2-bis(triethoxysilyl)acetylene, and the mass fraction of the silicon source precursor relative to the organosilicon sol was 1wt%~2.5wt%. The molar ratio of organosilicon precursor:water:hydrochloric acid was 1:60~240:0.

2. The support used was an α-Al2O3 ceramic support with an average pore size of 1~2nm.

2. The method for preparing the organosilicon / MOF-303 hybrid matrix membrane as described in claim 1, characterized in that... The mass ratio of MOF-303 powder to organosilicon sol is 0~0.

1.

3. The method for preparing the organosilicon / MOF-303 hybrid matrix membrane as described in claim 1, characterized in that... MOF-303 powder needs to be activated at 150°C for 2-4 hours before it can be added to organosilicon sol.

4. The method for preparing the organosilicon / MOF-303 hybrid matrix membrane as described in claim 1, characterized in that... MOF-303 / bridged silicone sol needs to be sonicated for 30-60 minutes before coating to ensure uniform dispersion of MOF-303 silicone sol.

5. The method for preparing the organosilicon / MOF-303 hybrid matrix membrane as described in claim 1, characterized in that... The calcination temperature of the organosilicon / MOF-303 mixed matrix membrane is 100℃~400℃, the calcination time is 20~40min, and it is repeated 2-3 times.

6. The method for preparing the organosilicon / MOF-303 hybrid matrix membrane as described in claim 1, characterized in that... The organosilicon / MOF-303 mixed matrix membrane is used for the separation of ethanol / water, isopropanol / water, and n-butanol / water, with an operating temperature of 50–80°C.

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