CN103506017A - Polyether-b-polyamide and glycerol triacetate blend membrane as well as preparation method and application thereof - Google Patents

Abstract

The invention relates to a gas separation membrane, in particular to a polyether-b-polyamide/triacetin blended gas separation membrane for acid gas separation. The invention selects polyether-b-polyamide PEBA containing ether oxygen groups and glycerol triacetate containing acetate groups as membrane materials, and prepares gas separation membranes through a solution blending method. _The blend _membrane preferentially permeates acid gases _{such as CO 2 , H 2 S} and _{SO 2 2} and other systems maintain a high separation performance.

Description

Polyether-b-polyamide and triacetin blend film and its preparation and application

technical field

The present invention relates to gas separation membrane technology, specifically a polyether-b-polyamide PEBA/triacetin GTA blend membrane, which can preferentially permeate CO ₂ , H ₂ S and SO ₂ and other acid gases.

Background technique

Acid gases, such as CO ₂ , SO ₂ , H ₂ S, HC1, C1 ₂ , NO _x, etc., are the main air pollutants and also the main pollutants in petroleum-based petrochemical industry. Such components not only affect The quality of the product, the formation of acid, serious corrosion of equipment and pipelines, and pollute the air, aggravate the greenhouse effect, causing serious harm to the ecological environment on the earth. Therefore, the enrichment and recovery of these acid gases is an important issue for saving resources and protecting the environment. Among them, the separation of CO ₂ is the focus of research, and CO ₂ emissions mainly come from industrial fields, such as thermal power generation, petrochemical industry, metallurgical enterprises, pharmaceutical industry, food fermentation fields, etc., so separating and capturing CO from different resources ₂ is very important, including for the production of pipeline-level natural gas, carbon dioxide recovery and reuse in the petrochemical industry, methane recovery in landfills and biogas digesters, carbon dioxide separation in flue gases, etc. The development of technology to separate acid gas CO ₂ has been become a priority.

At present, the traditional methods for acid gas separation mainly include physical absorption method, chemical absorption method, pressure swing adsorption method and low-temperature condensation method, etc., because the physical adsorption method requires a high partial pressure of _CO2 , but the removal degree is not high, and the change The adsorption capacity of pressure adsorption is limited, and the pretreatment requirements are high. The two methods are mainly used in _ammonia conversion gas and refinery gas; It is widely used, but the equipment for chemical absorption is huge, the energy consumption is high, the process is complex, the pipeline of the equipment is corroded, the absorbent is highly toxic, easy to degrade and has a large loss; It is convenient, flexible in operation, high in operation reliability, and will not experience high temperature or other extreme conditions during processing. It is one of the key points of research and development in the high-tech field that countries around the world pay special attention to.

In general, the effect of the chemical structure of a liquid solvent on gas absorption can serve as a guideline for designing polymers with high solubility coefficients. Based on this guideline, the researchers concluded by comparing the solubility coefficients of gases in different liquid solvents (different functional groups) and the solubility coefficients of gases in polymers containing these functional groups, acetate groups, carbonyl groups, and ether linkages are all CO ₂ functional group. Polyether-b-polyamide (PEBA) is a commercialized block copolymer containing ether oxygen groups, which is composed of polyether (PE) segment and polyamide (PA) segment. According to the content and types of PA and PE, PEBA can be divided into various types, all of which can be used as high-performance membrane separation materials. Liu Li, Bondar, Kim, etc. studied the permeability and separation performance of different types of PEBA materials, showing that PEBA has high selective permeability in polar/non-polar gas separation, but the permeation flux still needs to be further improved . GTA, an oligomer containing acetate groups, is considered to be a promising _CO2 absorbent in the physical absorption process, and is widely used as a plasticizer and additive in various industries. In the field of membrane separation of CO ₂ , Mary Katharine Barillas studied the performance of GTA as a supporting liquid membrane for separation of CO ₂ /H ₂ , but there is no research on solid membrane separation of CO ₂ so far.

Contents of the invention

The object of the present invention is to provide a polyether-b-polyamide/triacetin blend membrane for acid gas separation. The mass fraction of triacetin in this polymer blend membrane is 0.01% to 99%, and the _rest is polyether- _b -polyamide _. Separation membrane that is preferentially permeable than inert gases (H ₂ , N ₂ and CH ₄ ), and is effective for CO ₂ /N ₂ , SO ₂ /N ₂ , H ₂ S/CH ₄ , CO ₂ /CH ₄ , CO ₂ /H ₂ and other systems maintain high separation performance.

In order to achieve the above object, the technical scheme adopted in the present invention is:

Polyether-b-polyamide (PEBA) containing ether oxygen groups and glyceryl triacetate (GTA) containing acetate groups were selected as membrane materials, and the casting solution was prepared by solution blending, and then flowed on a glass plate. Extended into a film or coated on a flat filter membrane to form a film.

Specifically, its steps of the preparation process of the present invention are as follows:

a) Preparation of casting solution: first dissolve polyether-b-polyamide PEBA in n-butanol solvent to prepare a PEBA solution with a mass concentration of 0.1-20%; then add polyethylene glycol with the required mass to the solution PEG (polyethylene oxide PEO) is used to prepare a homogeneous casting solution with a melting temperature of 70-110°C;

b) Degassing of casting solution (standstill, negative pressure or ultrasonic degassing);

c) Forming a film on a glass plate (tetrafluoro plate) by casting a film-forming method or coating a flat filter membrane by a coating method to prepare a composite film;

d) Vacuum removal of residual solvent in the membrane.

The structural formula of polyether-b-polyamide (PEBA) material of the present invention is:

Among them, the polyamide segment PA can be nylon-6 (PA6), nylon-12 (PA12), nylon-6,6, etc.; the polyether segment PE can be polyethylene oxide (PEO), polybutylene oxide (PTMO), etc. The molecular weight of the copolymer depends on the content of PA and PE in the copolymer molecule. The molecular weight of the PA segment in the copolymer molecule ranges from 300 to 15,000, and the molecular weight of the PE segment in the copolymer molecule ranges from 200 to 6,000.

The structural formula of glyceryl triacetate (GTA) of the present invention is:

Its molecular weight is 218.2.

The mass fraction of glyceryl triacetate in the present invention is 0.01-99%, and the most suitable range is 5-60%.

The polyether-b-polyamide/triacetin blend membrane prepared by the present invention can realize the separation process of the gas mixture of different gas components, mainly including CO ₂ and N ₂ , CO ₂ and CH ₄ , CO ₂ and Separation of _H2 , _H2S and _CH4 , _SO2 and _N2 .

Concrete advantages of the present invention are as follows:

1. The two selected organic compounds, polyether _{-b-polyamide PEBA and glyceryl triacetate GTA, respectively contain ether bonds and acetate groups, which can improve the CO 2 dissolution} selectivity. This makes the blend membrane While maintaining the separation coefficient to meet the application requirements, the permeability coefficient of the gas is improved, and a _CO2 separation membrane with high separation performance is obtained.

2. The blended membrane prepared by the present invention is a polymer blended membrane that is preferentially permeable to acid gases such as CO ₂ , H ₂ S and SO ₂ relative to inert gases (H ₂ , N ₂ and CH ₄ ).

3. The PEBA/GTA blended film is prepared by blending, which solves the problem that GTA cannot be formed into a film.

4. The dissolution of PEBA and the blending of PEBA and GTA in the present invention are all physical processes, the operating conditions are mild, easy to repeat, and conducive to industrialization.

Description of drawings

Figure 1 is a test device diagram of the gas separation blend membrane, in the figure: (1) the first valve; (2) the second valve; (3) the third valve; (4) the fourth valve; (5) the fifth valve (6) Sixth valve; (7) Seventh valve; (8) Eighth valve; (9) Ninth valve; (10) 1L gas tank; (11) 50ml gas tank; (12) 100ml gas tank; (13) pressure gauge; (14) pressure sensor; (15) permeation tank;

Detailed ways

PEBA/GTA blend film preparation steps of the present invention are as follows:

a) Preparation of casting solution: first dissolve polyether-b-polyamide PEBA in n-butanol solvent to prepare a PEBA solution with a mass concentration of 0.1-20%; then add the required mass of triacetin to the solution , preparing a homogeneous casting solution, the dissolution temperature is 70-110°C;

b) Degassing of casting solution (standstill, negative pressure or ultrasonic degassing);

c) Form a film on a glass plate by casting a film-forming method or coat a flat filter membrane with a coating method to prepare a composite film;

d) Vacuum removal of residual solvent in the membrane.

In the present invention, the PEBA/GTA blend membrane is used for gas separation, and its permeability is obtained by the equal volume-swing pressure method, and the flow chart is shown in FIG. 1 . The steps for testing are as follows:

a) After putting the membrane into the osmosis tank (the osmosis tank is composed of two closed chambers separated by the membrane, each chamber is provided with a pipe interface communicating with the outside world), close the sixth valve and the ninth valve. Valves, all other valves are opened, and the whole system is evacuated to keep it in a vacuum state for 12 hours.

b) Select the appropriate permeate side volume through the first valve and the second valve, close all other valves, open the ninth valve, fill the 1L gas tank with gas to adjust the pressure, and adjust the temperature through the temperature control system.

c) During the test, open the seventh valve and the eighth valve, record the pressure change on the permeate side through the pressure sensor, and then calculate the permeability coefficient and separation coefficient of the gas in the membrane.

$\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 760</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{\mathrm{<span\; class="notranslate">\; V</span>}}{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{\mathrm{<span\; class="notranslate">\; 273.15</span>}}{\mathrm{<span\; class="notranslate">\; 273.15</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{\mathrm{<span\; class="notranslate">\; L</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;p</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; dm</span>}}$

${\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}}{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}}$

In the formula:

P——Barrer [1Barrer=10 ^-10 cm ³ (STP) cm/(cm ² s cmHg)] gas permeability coefficient in the membrane

V——The volume of gas permeation side cm ³

A——effective membrane area, cm ²

Δp—the pressure difference on both sides of the membrane, cmHg

l—thickness of the film, cm

T——The temperature of the permeation tank, ℃

dm—the time required for the pressure on the permeate side to increase by 1mmHg, s

P _A ——The permeability coefficient of gas A in the membrane Barrer[1Barrer=10 ^-10 cm ³ (STP) cm/(cm ² s cmHg)]

P _B ——The permeability coefficient Barrer of gas B in the membrane [1Barrer=10 ^-10 cm ³ (STP) cm/(cm ² s cmHg)]

α _A/B ——separation coefficient

The present invention will be described in further detail below in conjunction with specific examples, but the present invention is not limited to the specific examples.

Example 1:

Add 4 grams of vacuum-dried Pebax1074 (m(PEO):m(PA12)=45:55, mass ratio) to 96 grams of n-butanol solvent, and stir at 85°C for 6 hours to form a uniform and transparent polymer After the solution, add 1 gram of GTA to the polymer solution, continue to stir for 2 hours, and after forming a uniform and transparent solution again, carry out standing defoaming; The film liquid is evenly spread on the PTFE plate, the temperature of the glass plate is kept at 50°C, the solvent is volatilized, and the primary film is finally formed. Carefully remove the nascent film from the glass plate, put it in a vacuum oven, dry for 48 hours, remove the residual solvent, obtain a PEBA/GTA (20%) blended homogeneous film with a GTA content of 20wt.%, and test its permeability (35°C).

The experimental result of table 1 embodiment 1

Example 2:

Add 6 grams of vacuum-dried Pebax1074 to 95 grams of n-butanol solvent, stir at 80°C for 6 hours to form a uniform and transparent polymer solution, add 4 grams of GTA to the polymer solution, and continue stirring for 2 hours. After forming a uniform and transparent solution again, let it stand for defoaming, and pour the defoamed casting solution into a smooth iron ring on a clean horizontal glass plate to spread the casting solution evenly on the glass plate. The temperature is kept at 50° C., and the solvent is volatilized to finally form a primary film. Carefully remove the nascent film from the glass plate, put it in a vacuum oven, dry for 48 hours, remove the residual solvent, obtain a PEBA/GTA (40%) blended homogeneous film with a GTA content of 20wt.%, and test its permeability (35°C).

The experimental result of table 2 embodiment 2

Example 3:

Add 4 grams of vacuum-dried Pebax1074 to 95 grams of n-butanol solvent, stir at 80°C for 6 hours to form a uniform and transparent polymer solution, add 6 grams of GTA to the polymer solution, and continue stirring for 2 hours. After forming a uniform and transparent solution again, let it stand for defoaming, and pour the defoamed casting solution into a smooth iron ring on a clean horizontal glass plate to spread the casting solution evenly on the glass plate. The temperature is kept at 50° C., and the solvent is volatilized to finally form a primary film. Carefully remove the nascent membrane from the glass plate, put it in a vacuum oven, dry for 48 hours, remove the residual solvent, obtain a PEBA/GTA (60%) blended homogeneous membrane with a GTA content of 60wt.%, and test its permeability (35°C).

The experimental result of table 3 embodiment 3

Comparative example 1:

Table 4 is a comparison of the gas separation performance (35° C.) of the PEBA/GTA blend membrane and the pure PEBA membrane in Examples 1, 2, and 3 of the present invention.

Table 4 PEBA/PEG blend film of the present invention compares with PEBA homogeneous film

From the comparison of Examples 1, 2, 3 and the literature values, it can be seen that the permeability coefficient of the PEBA/GTA blend membrane is greater than that of the pure PEBA membrane, indicating that the blend membrane has improved the gas efficiency when separating _CO mixed gas system. Penetration properties.

Comparing Examples 1, 2, and 3, it can be seen that different contents of GTA also have a certain influence on the performance of the blended membrane. It can be seen that as the content of GTA increases, the gas permeability coefficient increases obviously, but the change of selectivity is similar to that of It is related to the physical properties of the separated gas itself.

Claims (9)

1. a blend film of PEBA and GTA, is characterized in that: the film material of blend film is polyether-b-polyamide PEBA and glyceryl triacetate GTA, wherein the quality of glyceryl triacetate in blend film The fraction is 0.01% to 99%, and the rest is polyether-b-polyamide. 2. The blended membrane according to claim 1, characterized in that: the membrane material polyether-b-polyamide PEBA is a block copolymer, and its structural formula is:

Among them, PA is an amide segment, PE is a polyether segment; the molecular weight of the copolymer depends on the content of PA and PE in the copolymer molecule, the molecular weight of the PA segment in the copolymer molecule ranges from 300 to 15000, and the PE chain in the copolymer molecule The molecular weight of the segment ranges from 200 to 6000. 3. The blend film according to claim 2, characterized in that: the PA segment is nylon-6 (PA6), nylon-11 (PA11) or nylon-12 (PA12); the PE segment is polyethylene oxide Alkanes (PEO), Polypropylene Oxide (PPO) or Polybutylene Oxide (PTMO). 4. The blend film according to claim 1, characterized in that: the structural formula of the film material glyceryl triacetate GTA is:

Its molecular weight is 218.2. 5. The blend film according to claim 1, characterized in that the mass fraction of glyceryl triacetate is 5-60%. 6. a preparation method of the described blend film of claim 1, is characterized in that: a) Preparation of casting solution: first dissolve polyether-b-polyamide PEBA in n-butanol solvent to prepare a PEBA solution with a mass concentration of 0.1-20%; then add the required mass of triacetin to the solution GTA, for the preparation of homogeneous casting solution, the melting temperature is 70-110°C; b) Degassing of the casting solution; c) Film-making on a glass plate or a PTFE plate by casting a film-forming method or coating a flat filter membrane with a coating method to prepare a composite film; d) Removing residual solvent in the membrane. 7. The preparation method according to claim 6, characterized in that: the mass fraction of the PEBA solution is 0.1% to 8%; one or both of static, negative pressure or ultrasonic degassing are used for degassing the casting solution combination of the above. 8. An application of the blend membrane according to any one of claims 1 to 5, characterized in that the blend membrane can be used as a gas separation membrane to realize the separation process of gas mixtures of different gas components. 9. According to the application of the blended membrane according to claim 8, it is characterized in that: the blended membrane is applied to the separation of the gas mixture comprising preferentially permeable gas and non-preferentially permeable gas, thereby realizing the separation and removal of preferentially permeable gas ; Preferentially permeable gases include one or more of CO ₂ , H ₂ S or SO ₂ ; The non-preferentially permeable gas includes one or two or more of N ₂ , O ₂ , C1-C4 hydrocarbon gas, and H ₂ .

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