阅读说明：本技术 一种高选择性聚酰亚胺气体分离膜的制备方法 (Preparation method of high-selectivity polyimide gas separation membrane ) 是由 栗晓东 于 2021-09-28 设计创作，主要内容包括：本发明提供了一种高选择性聚酰亚胺气体分离膜的制备方法,首先通过两步有机合成,合成了一种同时含有三氟甲基和羟基的二胺单体6FDAP,然后与不同二酐通过化学亚胺化法合成三种聚酰亚胺。将制得的聚酰亚胺溶液涂抹在模板上,干燥后制得6FDAP基聚酰亚胺薄膜。本发明所述的制备方法通过化学合成合成出含有三氟甲基和羟基的二胺单体6FDAP,然后利用化学亚胺化法合成了6FDAP基聚酰亚胺,所合成的聚酰亚胺由于具有大量的三氟甲基和羟基,不仅使其具有优异的热稳定性,而且赋予其聚酰亚胺对CO-(2)/CH-(4)具有较高的选择性,可用于CO-(2)的捕集等方面,该方法的工艺简单,成本低,环境友好,易于工业化。(The invention provides a preparation method of a high-selectivity polyimide gas separation membrane, which comprises the steps of synthesizing a diamine monomer 6FDAP containing trifluoromethyl and hydroxyl at the same time through two-step organic synthesis, and then synthesizing three types of polyimide with different dianhydride through a chemical imidization method. And (3) coating the prepared polyimide solution on a template, and drying to obtain the 6 FDAP-based polyimide film. The preparation method synthesizes a diamine monomer 6FDAP containing trifluoromethyl and hydroxyl through chemical synthesis, and then synthesizes the polyimide 6FDAP group by using a chemical imidization method, and the synthesized polyimide has a large amount of trifluoromethyl and hydroxyl, so that the polyimide not only has excellent thermal stability, but also has the polyimide with CO resistance 2 /CH 4 Has high selectivity and can be used for CO 2 To be caughtThe method is simple in process, low in cost, environment-friendly and easy to industrialize.)

1. A preparation method of a high-selectivity polyimide gas separation membrane is characterized by comprising the following steps:

(1) mixing 6FAP and NMP to obtain a solution A, mixing nitrobenzoyl chloride and toluene to obtain a solution B, slowly dropwise adding the solution B into the solution A at 50-70 ℃, reacting at 50-80 ℃ for 1-5h, mixing the reaction solution with methanol, separating out solids, washing and drying to obtain 6FDNP, mixing the 6FDNP with DMF, adding palladium-carbon, reacting for 8-12h under a hydrogen atmosphere, mixing the reaction solution with deionized water, separating out solids, washing and drying to obtain 6 FDAP;

(2) mixing dianhydride monomer, DMAC (dimethylacetamide) and 6FDAP (fully drawn ammonium chloride) at 0-25 ℃, reacting for 8-24h under heat preservation, adding a dehydrating agent and a catalyst, continuing to react for 8-12h, mixing the reaction solution with ethanol, separating out solid, washing and drying to obtain 6 FDAP-based polyimide;

(3) mixing the 6 FDAP-based polyimide and DMAC to obtain a membrane casting solution, coating the membrane casting solution on a template, volatilizing a solvent to obtain a prefabricated membrane, and carrying out high-temperature heat treatment on the prefabricated membrane to obtain the required separation membrane.

2. The method of claim 1, wherein: the dianhydride monomer includes at least one of 6FDA, TA-TFMB and TMEG.

3. The method of claim 1, wherein: the dehydrating agent in the step (2) is acetic anhydride.

4. The method of claim 1, wherein: the catalyst in the step (2) is triethylamine.

5. The method of claim 1, wherein: and (2) mixing the reaction solution with ethanol, separating out solid, washing with ethanol for 10-18h, and drying at 120-200 ℃ for 20-30h to obtain the 6 FDAP-based polyimide.

6. The method of claim 1, wherein: the solid content of the casting solution is 5-8 wt%; preferably 7% by weight.

7. The method of claim 1, wherein: the template is a polytetrafluoroethylene template.

8. The method of claim 1, wherein: the high-temperature heat treatment method in the step (3) is to carry out vacuum drying on the prefabricated membrane for 24 hours at the temperature of 100 ℃ and 150 ℃.

Technical Field

The invention belongs to the field of high polymer materials, and particularly relates to a preparation method of a high-selectivity polyimide gas separation membrane.

Background

In recent years, CO is used₂The problems of global warming, glacier melting and the like caused by the greenhouse effect generated by excessive emission seriously damage the ecological environment of the earth on which people live. Thus, CO₂Of (2) is excessiveEmissions have become a problem that mankind must face and await resolution.

The membrane separation method is currently used for industrially separating and enriching CO in natural gas and flue gas₂Is a new and emerging method. The commonly used membrane separation materials mainly include high molecular materials such as Cellulose Acetate (CA), Polyethyleneimine (PEI) and Polyimide (PI). Polyimide is a high molecular material formed by connecting imide rings, and has been paid attention by many researchers due to its advantages such as excellent thermal stability, strong hydrophobicity, and stable chemical properties. Fluorine is a very miraculous element, and the fluorine is introduced into the polyimide, so that the thermal stability, the light transmittance and the hydrophobic property of the polyimide can be enhanced, and the polyimide can be mixed with polar gas CO₂Generating quadrupole-dipole interaction and improving CO₂/CH₄Selectivity of (2). However, polyimide membranes have not achieved very desirable results in the separation of carbon dioxide due to the "Trade-off" effect to date. Thus, a class of para-CO was developed₂The fluorine-containing polyimide film with high selectivity has good application prospect.

Disclosure of Invention

In view of the above, the present invention is directed to a method for preparing a highly selective polyimide gas separation membrane, which can react with CO using trifluoromethyl and hydroxyl in 6 FDAP-based polyimide₂The nature of the interaction effectively improves CO₂/CH₄And meanwhile, the 6 FDAP-based polyimide contains a large amount of fluorine elements, so that the polyimide has excellent thermal stability, hydrophobicity and light transmittance.

In order to achieve the purpose, the technical scheme of the invention is realized as follows:

a preparation method of a high-selectivity polyimide gas separation membrane comprises the following steps:

(1) mixing 2, 2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane (6 FAP for short) with NMP, heating to 40-70 ℃ to obtain a light yellow solution A, mixing nitrobenzoyl chloride with toluene to obtain a solution B, slowly dripping the solution B into the solution A at 50-70 ℃, reacting at 50-80 ℃ for 1-5h, preferably at 60 ℃ for 3h, mixing the reaction solution with methanol, reducing the temperature to room temperature, separating out a large amount of white solids, separating out the solids, washing with methanol for three times, vacuum drying at 90 ℃ for 12h to obtain a white solid 2, 2-bis (3-nitro-4-hydroxyphenyl) hexafluoropropane (6 FDNP for short), mixing the 6FDNP with DMF, adding palladium carbon, reacting under hydrogen atmosphere for 8-12h, mixing the reaction solution with deionized water, separating out solids, washing and drying to obtain the expected diamine monomer 6 FDAP;

(2) mixing and dissolving dianhydride monomer and DMAC, adding 6FDAP at 0-25 ℃, carrying out heat preservation reaction for 8-24h, adding a dehydrating agent and a catalyst, continuing to react for 8-12h, mixing the reaction solution with ethanol, separating out solids, washing for 10-18h by using ethanol, and drying for 20-30h at 120-200 ℃ to obtain 6 FDAP-based polyimide;

(3) mixing the 6 FDAP-based polyimide and DMAC to obtain a membrane casting solution, coating the membrane casting solution on a template, volatilizing a solvent to obtain a prefabricated membrane, and carrying out high-temperature heat treatment on the prefabricated membrane to obtain the required separation membrane.

Further, the dianhydride monomer includes at least one of 6FDA, TA-TFMB and TMEG.

Further, the dehydrating agent in the step (2) is acetic anhydride.

Further, the catalyst in the step (2) is triethylamine.

Further, the solid content of the casting solution is 5-8 wt%; preferably 7% by weight.

Further, the template is a polytetrafluoroethylene template.

Further, the high temperature heat treatment method in the step (3) is to dry the prefabricated membrane in vacuum at 100-150 ℃ for 24 h.

Compared with the prior art, the preparation method of the high-selectivity polyimide gas separation membrane has the following advantages:

the preparation method synthesizes diamine monomer 6FDAP containing trifluoromethyl and hydroxyl through chemical synthesis, and then synthesizes polyimide 6FDAP base through chemical imidization, and the synthesized polyimide has a large amount of trifluoromethyl and hydroxyl, so that the synthesized polyimide not only has good chemical imidization performance, but also has good chemical imidization performance, and can be used for preparing a polyimide with good chemical imidization performanceHas excellent thermal stability, and imparts a polyimide thereof with CO resistance₂/CH₄Has high selectivity and can be used for CO₂The method has the advantages of simple process, low cost, environmental protection and easy industrialization.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

FIG. 1 is an XRD pattern of a 6 FDAP-based polyimide prepared according to examples 1-3 of the present invention;

FIG. 2 shows a 6FDAP implementation of the present invention¹A HNMR map;

FIG. 3 is a schematic diagram of a connection structure of a high molecular polymer gas separation performance test apparatus according to an embodiment of the present invention;

FIG. 4 shows CO of separation membranes prepared in examples 1 to 3 of the present invention₂/CH₄Gas separation diagram.

Detailed Description

Unless defined otherwise, technical terms used in the following examples have the same meanings as commonly understood by one of ordinary skill in the art to which the present invention belongs. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods are conventional methods unless otherwise specified.

The present invention will be described in detail with reference to the following examples and accompanying drawings.

Example 1

Synthesis of (mono) 6FDNP

6g of 6FAP was weighed into 24mL of NMP and heated to 60 ℃ to form a pale yellow solution, denoted as solution A. 6.62g of paranitrobenzoyl chloride was weighed out and dissolved in 7mL of toluene and identified as solution B. Solution A was maintained at 60 deg.C and solution B was slowly added dropwise to solution A. After keeping the temperature and reacting for 3 hours, 50mL of methanol solution was added to the reaction solution and the temperature was lowered to room temperature, and a large amount of white solid was precipitated. The white solid was washed three times with methanol and dried under vacuum at 90 ℃ for 12h to collect 6FDNP as a white solid, 10 g.

Synthesis of (di) 6FDAP

Dissolving the synthesized 6FDNP in 30mL of DMF, adding 0.1g of Pd/C, introducing hydrogen, reacting at 30 ℃ for 12h, dropwise adding 50mL of deionized water into the reaction solution to separate out a large amount of white solid, filtering, washing with methanol for three times, drying at 90 ℃ for 12h to obtain 9g of white solid 6FDAP, and utilizing¹HNMR confirmed the correct structure, as shown in FIG. 2.

Synthesis of (tri) 6 FDAP-based polyimide

Dissolving 2g of 6FDA in 10mL of DMAC (dimethylacetamide), reducing the reaction temperature to 0 ℃, then weighing 2.72g of prepared 6FDAP, adding the weighed 6FDAP into the reaction solution, reacting for 2h, starting to increase the temperature to 25 ℃, and continuing to react for 10 h. To the reaction mixture were added 0.8mL of triethylamine and 2.7mL of acetic anhydride, and the solution quickly became viscous and the reaction was continued at room temperature for 12 h. The reaction solution was poured into 300mL of ethanol, and a large amount of white filaments were precipitated, and the solution was filtered and washed with ethanol for 12 hours. And (3) drying the washed polyimide in vacuum at 150 ℃ for 24h to obtain white 6 FDAP-based polyimide, wherein 4g of the white 6 FDAP-based polyimide is marked as FPI-1.

(IV) Synthesis of separation Membrane

Dissolving 0.5g of FPI-1 in 7mL of DMAC (dimethylacetamide), performing ultrasonic defoaming, uniformly coating on a polytetrafluoroethylene plate, drying at 60 ℃ for 8h in an oven, shaping, then dropping, and performing vacuum drying at 150 ℃ for 24h to obtain 6FDAP (fully drawn ammonium phosphate) -based high-CO₂/CH₄A selective polyimide gas separation membrane.

Example 2

The difference from example 1 is that the 6FDA substitution in step (III) was TA-TFMB to give a white 6 FDAP-based polyimide, designated FPI-2, and the other steps were the same as in example 1.

Example 3

The difference from example 1 is that the 6FDA was replaced with TMEG in step (III) to give a white 6 FDAP-based polyimide, designated FPI-3, and the other steps were the same as in example 1.

CO was applied to the separation membranes obtained in examples 1 to 3 and three commercially available polyimide membranes₂/CH₄Gas separation Performance test, gasThe connection structure of the separation performance testing equipment is shown in fig. 4, wherein F1-10 are valves, and the specific experimental steps are as follows:

(1) the separation membranes prepared in examples 1 to 3 and three commercially available polyimide membranes (each of which is a polyimide membrane)5218. 6FDA-ODA and P84), respectively loading into membrane tanks, starting vacuum pump, F3, F6 and F7, starting F4 and F5, and slowly starting F8 to simultaneously pump air from the upper membrane tank and the lower membrane tank, wherein F1 and F2 are in a closed state; when the vacuum degree reaches 3.0 multiplied by 10^-2Testing can be carried out when the temperature is below Torr;

(2) firstly, sequentially closing F4 and F8, then opening F1 to fill test gas with certain pressure, repeatedly opening F2 to replace gas for three times, adjusting the sample injection pressure, closing F3 (according to the test gas requirement), F6, F7 and a vacuum pump, opening F4 to click "start" to start data acquisition, wherein F1 and F2 are still in a closed state;

(3) and after the test is finished, opening the vacuum pump, F3, F6 and F7, closing the pressure reducing valve, opening F1 and F2 to exhaust gas in the sample injection pipeline, closing F1 and F2, and slowly opening F8 to simultaneously exhaust gas.

The permeability coefficient P of the gas can be calculated by testing the curve of the gas pressure of the upper membrane pool along with the change of time. Three separation membranes prepared in examples 1 to 3 and a commercially available common polyimide membrane were used for CO₂/CH₄The separation performance is shown in table 1 and fig. 4. As can be seen from the analysis in Table 1, the 6 FDAP-based polyimide obtained according to the technical scheme provided by the invention has higher CO than common polyimide₂/CH₄And (4) selectivity.

Table 1 results of performance tests

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.