Preparation method and application of organosilicon / MOF-303 mixed matrix membrane

Abstract

The invention relates to a preparation method and application of an organosilicon / MOF-303 mixed matrix membrane, a silicon source precursor is uniformly dissolved in an ethanol solvent, then a mixture of water and hydrochloric acid is added according to a certain proportion, a water bath heating reaction is carried out for a period of time to obtain an organosilicon sol, prepared MOF-303 powder is added into the organosilicon sol according to a certain proportion, and the organosilicon / MOF-303 mixed matrix membrane is obtained. The preparation method comprises the following steps: uniformly mixing the raw materials through ultrasound to obtain a separation layer sol, coating the prepared separation layer sol on a ceramic support body through a hot coating method, and calcining in an air atmosphere for a period of time to obtain the MOF-303 / mixed matrix membrane. An organic silicon substance BTESA with a rigid acetylene bridge structure is preferably selected as a precursor, an MOF-303 material with a high specific surface area is doped into the precursor, the pore channel structure of the membrane is modified, more adsorption sites are provided for water molecules, and the composite membrane material with the optimal separation performance is obtained by optimizing the composite proportion.

Description

Technical Field

[0001] The invention belongs to the technical field of membrane material preparation, and specifically relates to an application of a MOF-303 mixed matrix membrane and a preparation method thereof. Background Art

[0002] Ethanol, isopropanol and n-butanol are common products in the petrochemical industry. At present, they are often miscible with water in a certain proportion in the actual production and separation process. How to achieve efficient dehydration of their mixture is of great significance. Since the boiling points of the above three alcohols are close to those of water, they are easy to form azeotropes, which are difficult to separate by traditional separation methods and consume a lot of energy. Pervaporation technology has attracted widespread attention because it is not limited by gas-liquid equilibrium and has low energy consumption. Silicone materials have been widely studied in the field of pervaporation dehydration due to their advantages such as high specific surface area, adjustable pore size, good hydrothermal stability and excellent chemical resistance. BTESA exhibits satisfactory permeation flux in alcohol / water separation due to its large pore size and good hydrophilicity, but the selectivity is relatively low. The MOF-303 membrane material has high water absorption (up to 500cm at 303K). 3 g -1 ) has attracted people's attention.

[0003] MOF-303 has an xhh topology and is constructed by infinite rod-shaped Al(OH)(-COO)2 clusters connected by HPDC ligands. In the clusters, the octahedrally coordinated Al(III) ions are bound together by four bridging carboxyl groups and two hydroxyl groups. MOF-303 has a three-dimensional framework with one-dimensional (1D) rhombus channels (open space of about 0.6 nm) along the axis. The clusters and ligands give the 1D channels hydrophilic sites, which is conducive to the rapid transport of water molecules. In addition, the high pore volume and hydrophilic skeleton of MOF-303 also provide favorable conditions for the preferential adsorption of water molecules.

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

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

[0006] In order to solve the above technical problems, the present invention provides the following technical solution: a preparation method and application of an organosilicon / MOF-303 mixed matrix membrane. It comprises the following steps:

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

[0008] The prepared MOF-303 powder is added to the organic silica sol in a certain proportion, and the mixture is evenly mixed by ultrasound to obtain a separation layer sol.

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

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

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

[0012] As a preferred solution of the preparation method and application of an organosilicon / MOF-303 mixed matrix membrane described in the present invention, the synthesis method of MOF-303 is a hydrothermal synthesis method, and the specific preparation method is:

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

[0014] Dissolve a certain amount of urea in water and stir evenly. Take a certain amount of urea aqueous solution and add it to solution 1 to obtain solution 2, so 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 then dried at 100° C. overnight to obtain MOF-303 powder.

[0016] As a preferred solution of the preparation method and application of the organosilicon / MOF-303 mixed matrix membrane described in 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 an organosilicon / MOF-303 mixed matrix membrane described in the present invention, in the MOF-303 / organosilicon sol mixed sol, the mass ratio of MOF-303 to organosilicon sol is 0 to 0.1.

[0018] As a preferred scheme for the preparation method and application of a silicone / MOF-303 mixed matrix membrane described in the present invention, the calcination temperature of the separation layer is 100-400°C, the calcination time is 20-40min, the coating concentration of the separation layer is 0.25wt%, and it is repeated 2-3 times.

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

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

[0021] The beneficial effects of the present invention are:

[0022] The present invention selects a BTESA precursor with a rigid acetylene bridge as a silicon source. Due to its rigid bridging group, the BTESA organosilicon membrane has a larger pore size, thereby showing a good permeation flux for the alcohol / water system, but also due to its loose pore structure, the selectivity is low. In order to improve the selectivity of the BTESA membrane, the present invention introduces a MOF-303 material with a high water absorption rate. The MOF-303 material has abundant -COO- and -OH groups, providing numerous adsorption sites for water molecules. In addition, MOF-303 has a three-dimensional framework with a one-dimensional (1D) diamond channel (open space of about 0.6nm) along the axis. The clusters and ligands give the 1D channel hydrophilic sites, providing conditions for the rapid transmission of water molecules. By incorporating MOF-303 into the BTESA organosilicon sol, additional sites and channels are provided for the transmission of water molecules without changing the original organosilicon network structure, thereby improving the separation selectivity of the membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

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

[0025] Figure 2 This is the water vapor adsorption spectrum of MOF-303 powder. DETAILED DESCRIPTION

[0026] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0027] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present 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 term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0029] The separation performance of the organosilicon / MOF-303 mixed matrix membrane prepared in the present 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 calculation formula of permeation flux is as follows:

[0031]

[0032] The calculation formula of separation factor is as follows:

[0033]

[0034] Example 1

[0035] This embodiment provides a preparation method and application of an organosilicon / MOF-303 mixed matrix membrane:

[0036] (1) Preparation of MOF-303

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

[0038] (2) Preparation of BTESA sol

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

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

[0041] Before the formal preparation, MOF-303 was activated at 150°C 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 0.25wt%, and then the diluted sol was rubbed on the prepared ceramic support with a silica-zirconia nano-transition layer by hot coating, and the coated membrane was calcined in a tube furnace at 250°C for 30min, and this process was repeated 3 times to prepare a BTESA / MOF-303-2.5% hybrid membrane. The prepared membrane was used for the pervaporation dehydration test of the 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 and processes are all based on embodiment 1 to obtain the membrane of this embodiment, which is recorded 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%, and in specific step 2), 50mg of MOF-303 is dissolved in the prepared BTESA organosilicon sol, and the remaining steps and processes are all referred to embodiment 1 to obtain the membrane of this embodiment, which is recorded 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) is directly diluted to 0.25 wt % and coated on a support to obtain a film of this comparative example, which is recorded as BTESA original film.

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

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

[0052]

[0053]

[0054] As can be seen from Table 1, with the increase of the doping amount of MOF-303, the flux and separation factor of the BTESA / MOF-303 mixed matrix membrane increased to varying degrees. This is because the MOF-303 material has abundant -COO- and -OH groups, which provide numerous adsorption sites for water molecules and preferentially allow water molecules to pass through during the permeation process. In addition, MOF-303 has a three-dimensional framework with one-dimensional (1D) diamond channels (open space of about 0.6nm) along the axis. The clusters and ligands give the 1D channels hydrophilic sites, which provide conditions for the rapid transmission of water molecules. In summary, the experimental results show that the incorporation of MOF-303 material can improve the separation effect 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, and the remaining steps are the same to obtain the membrane of this comparative example, which is recorded 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 is replaced with a 1,2-bis(triethoxysilyl)ethylene (BTESEthy) precursor to prepare an organic silica sol, which is diluted to 0.25wt% and coated on a support to obtain a film of this comparative example, which is recorded 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, and the remaining steps are the same to obtain the membrane of this comparative example, which is recorded as BTESA / MOF-801-2.5%.

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

[0062] Table 2 Pervaporation dehydration performance of different membranes for 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] As can be seen from Table 2, the type of organosilicon precursor and the preparation parameters of the organosilicon sol will have an impact on the pervaporation performance of the membrane. Compared with the BTESA / MOF-303 membrane in Example 1, the organosilicon network formed by the BTESEthy precursor in Comparative Example 3 has a tighter structure. After doping with MOF-303, due to its good water absorption, the separation factor is improved, but the permeation flux is low. In addition, by changing the ratio of the organosilicon sol, a BTESA / MOF-303 mixed matrix membrane with higher separation performance can be obtained. At the same time, the separation effects of different doping materials are also compared. Although MOF-801 is also a hydrophilic filler, research data show that its water absorption is not as good as MOF-303, and the separation performance after doping is not significantly improved.

[0065] In summary, the present invention provides a method for preparing and applying an organosilicon / MOF-303 mixed matrix membrane. The present invention preferably uses an organosilicon substance BTESA having a rigid acetylene bridge structure as a precursor, and incorporates a MOF-303 material having a high specific surface area and a specific adsorption effect on water molecules into the precursor, thereby modifying the pore structure of the membrane and providing more adsorption sites for water molecules, thereby promoting the dissolution and diffusion selectivity of water molecules in the membrane network. The permeation flux and separation factor of the membrane are improved without changing the original membrane network structure, and a composite membrane material with the best separation performance is obtained by optimizing the composite ratio.

[0066] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A preparation method and application of an organosilicon / MOF-303 mixed matrix membrane, characterized in that: The silicon source precursor is evenly dispersed in an ethanol solvent, and a mixed solution of hydrochloric acid and water is added in a certain proportion, and the reaction is carried out in a water bath at a certain temperature for a period of time to obtain an organic silica sol; the prepared MOF-303 particles are added to the organic silica sol in a certain proportion, and a uniformly mixed MOF-303 / bridge organic silica sol is obtained by ultrasound; the prepared MOF-303 / bridge organic silica sol is rubbed on a ceramic support by hot coating, and calcined in an air atmosphere for a period of time to obtain a MOF-303 mixed matrix membrane.

2. The preparation method and application of the organosilicon / MOF-303 mixed matrix membrane according to claim 1, characterized in that The silicon source precursor used is 1,2-bis(triethoxysilyl)acetylene, and the mass fraction of the silicon source precursor used relative to the organic silica sol is 1wt% to 2.5wt%.

3. The preparation method and application of the organosilicon / MOF-303 mixed matrix membrane as claimed in claims 1 and 2, characterized in that The molar ratio of organosilicon precursor: water: hydrochloric acid is 1:60-240:0.2, the reaction temperature is 40°C, and the reaction time is 2-4h.

4. The preparation method and application of the organosilicon / MOF-303 mixed matrix membrane according to claim 1, characterized in that Its preparation method is hydrothermal synthesis: AlCl3·6H2O, H3PDC·H2O and H2O were dissolved in a molar ratio of 1:1:2300 to prepare solution 1; a certain amount of urea was dissolved in water in another beaker and stirred evenly; a certain amount of urea aqueous solution was then added to solution 1 to obtain solution 2, so that the molar ratio of AlCl3·6H2O:H3PDC·H2O:urea:H2O was 1:1:2.4:2300; solution 2 was heated at 110°C in a reactor for 16 hours to obtain MOF-303; MOF-303-urea powder was collected by vacuum filtration, and then dried at 100°C overnight to obtain MOF-303 powder.

5. The preparation method and application of the organosilicon / MOF-303 mixed matrix membrane according to claim 1, characterized in that The mass ratio of the MOF-303 powder to the organic silica sol is 0 to 0.

1.

6. The preparation method and application of the organosilicon / MOF-303 mixed matrix membrane according to claim 1, characterized in that MOF-303 powder needs to be activated at 150°C for 2-4h before being added to the organosilica sol.

7. The preparation method and application of the organosilicon / MOF-303 mixed matrix membrane according to claim 1, characterized in that MOF-303 / bridged organic silica sol needs to be ultrasonicated for 30-60 minutes before coating to ensure that MOF-303 silica sol is evenly dispersed.

8. The preparation method and application of the organosilicon / MOF-303 mixed matrix membrane according to claim 1, characterized in that The support used is an α-Al2O3 ceramic support with an average pore size of 1 to 2 nm.

9. The preparation method and application of the organosilicon / MOF-303 mixed matrix membrane according to claim 1, characterized in that The calcination temperature of MOF-303 / mixed matrix membrane is 100°C to 400°C, the calcination time is 20 to 40 minutes, and it is repeated 2 to 3 times.

10. The preparation method and application of the organosilicon / MOF-303 mixed matrix membrane according to claim 1, characterized in that The MOF-303 / mixed matrix membrane is used for alcohol / water separation, and the separation system includes ethanol / water, isopropanol / water, and n-butanol / water, and the operating temperature is 50-80°C.

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