CN111841338A - Fixed carrier composite membrane for separating carbon dioxide and preparation method thereof - Google Patents
Fixed carrier composite membrane for separating carbon dioxide and preparation method thereof Download PDFInfo
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- CN111841338A CN111841338A CN201910338331.9A CN201910338331A CN111841338A CN 111841338 A CN111841338 A CN 111841338A CN 201910338331 A CN201910338331 A CN 201910338331A CN 111841338 A CN111841338 A CN 111841338A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/12—Composite membranes; Ultra-thin membranes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/22—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion
- B01D53/228—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion characterised by specific membranes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
- B01D71/66—Polymers having sulfur in the main chain, with or without nitrogen, oxygen or carbon only
- B01D71/68—Polysulfones; Polyethersulfones
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- Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
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Abstract
The invention relates to a method for CO2A separated fixed carrier composite membrane and a preparation method thereof. The method is to prepare the fixed carrier composite membrane by blending two polymer materials of polyvinyl alcohol and polyvinyl imidazole and optionally adding metal ions (preferably magnesium ions) capable of reacting with the two polymers. The membrane is used for separating carbon dioxide to obtain high CO2Permeation rate and high separation factor. The method has the advantages of simple operation process, low cost, environmental protection and the like.
Description
Technical Field
The invention belongs to the technical field of membrane separation, and relates to a fixed carrier composite membrane for separating carbon dioxide and a preparation method thereof.
Background
World fossil fuel combustion to produce CO2The global climate deterioration is aggravated by an increase in the amount of gas discharged, but CO has been accelerated in recent years2Also receiving more and more attention.To date, CO is used in industry2The separation method mainly comprises an absorption method, an adsorption method, a low-temperature distillation method, a membrane separation method and the like. Relative to other CO2Membrane separation techniques have many advantages for separation methods. Such as lower production cost, small floor space, convenient operation, large operation flexibility, high energy efficiency, less environmental impact and the like.
In CO2In the membrane separation process, high CO must be simultaneously obtained2Permeation rate and high CO2The separation factor can meet the separation requirement. The membrane is in CO due to the restriction of "Robeson Upper Limit2Research in separations still faces significant challenges. At present, CO is produced2There are several problems in the process of separating membranes that limit the separation efficiency of the membranes, including their resistance to plasticization, their resistance to heat, and their reasonable cost effectiveness.
The fixed carrier composite membrane belongs to one of the transfer-promoting membranes, and the internal groups of the membrane can be reacted with CO2Acts to greatly increase CO2Transfer efficiency in the membrane. The gas transport resistance of the composite membrane as a whole includes the transport resistance of the support and the selective separation layer. Wherein properties of the support material such as pore size and pore size distribution have a large influence on the magnitude of the gas transport resistance. The support layer can provide good thermal stability and mechanical stability, the preparation process is simple, and meanwhile, the high permeability of the composite membrane can be ensured. The surface coating is generally composed of one or more polymers containing a polymer capable of reacting with CO2The specific group on which the action takes place.
Chinese patent CN105727775A discloses a membrane for separating methane or carbon dioxide, which is a composite membrane prepared by coating a metal alkoxide solution consisting of tetraalkoxysilane and trialkoxysilane containing hydrocarbon group on an inorganic porous support. The prepared composite membrane has excellent heat resistance, durability and chemical resistance, but CO 2The separation factor is low and needs to be improved.
Therefore, research and development of a composite membrane having excellent chemical stability and mechanical stability and high permselectivity has great significance for development of separation membrane technology.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a fixed carrier composite membrane for separating carbon dioxide and a preparation method thereof aiming at the defects of the prior art, wherein a separation layer of the membrane is prepared by blending two polymer materials of polyvinyl alcohol and polyvinyl imidazole, and preferably adding metal ions which can react with the two polymers. The membrane has excellent chemical stability and mechanical stability, and has high selective permeability.
To this end, the invention provides, in a first aspect, a method for CO2The separated fixed carrier composite membrane comprises a supporting layer and a separating layer, wherein the separating layer is a blend of polyvinyl alcohol and polyvinyl imidazole.
According to some preferred embodiments of the present invention, the polyvinyl alcohol and the polyvinyl imidazole in the polyvinyl alcohol and polyvinyl imidazole blend are both loaded with metal ions.
In some embodiments of the invention, the metal comprises one or more of magnesium, copper and calcium; preferably, the metal is magnesium.
In the invention, the thickness of the separation layer is 3-10 μm.
In some embodiments of the invention, the weight ratio of the polyvinyl alcohol to the polyvinyl imidazole in the polyvinyl alcohol and polyvinyl imidazole blend polymer is 4:3 to 8: 3.
In some preferred embodiments of the present invention, the mass fraction of metal ions is 0 to 1.5% based on the total mass of the separation layer.
In the present invention, the support layer is preferably a polysulfone ultrafiltration membrane.
In some embodiments of the invention, the polysulfone ultrafiltration membrane has an average cut-off molecular weight of 6000, 20000, 30000, or 50000.
In a second aspect of the invention, said method is provided for CO2A method of preparing a separated fixed support composite membrane comprising:
step M, mixing a polyvinyl alcohol aqueous solution, a polyvinyl imidazole aqueous solution and an optional metal salt aqueous solution, stirring, standing to remove bubbles, and obtaining a coating solution;
and step N, uniformly coating the coating liquid on the surface of the support layer, and drying at constant temperature and constant humidity to prepare the fixed carrier composite membrane.
In the invention, the polyvinyl alcohol aqueous solution is prepared by dissolving polyvinyl alcohol in water.
In some embodiments of the present invention, the mass fraction of the aqueous polyvinyl alcohol solution is 3% to 6%.
In the invention, the polyvinyl imidazole aqueous solution is prepared by dissolving polyvinyl imidazole in water.
In some embodiments of the present invention, the mass fraction of the aqueous polyvinylimidazole solution is between 3% and 6%.
In some specific embodiments of the present invention, the total solid content of the polyvinyl alcohol and the polyvinyl imidazole in the coating solution is 3% to 6% by mass of the total mass of the coating solution.
In some specific embodiments of the present invention, in the coating solution, the mass ratio of the polyvinyl alcohol to the polyvinyl imidazole is 4:3 to 8: 3.
In some particularly preferred embodiments of the present invention, the mass fraction of magnesium ions is 0 to 0.06% based on the total mass of the coating solution.
In the present invention, the aqueous metal salt solution is prepared by dissolving a metal salt in water.
In some embodiments of the invention, the metal ion mass fraction in the aqueous metal salt solution is between 0.01% and 1%.
In the invention, the metal salt comprises one or more of metal chloride, metal sulfate and metal acetate, and the metal comprises one or more of magnesium, copper and calcium.
In some preferred embodiments of the present invention, the metal salt comprises one or more of magnesium chloride, magnesium sulfate, or magnesium acetate.
In some embodiments of the present invention, in the step M, the stirring temperature is 20 to 40 ℃.
In some embodiments of the present invention, in the step M, the stirring time is 30-60 min.
In some embodiments of the present invention, in step M, the standing time is not less than 24h, preferably the standing time is 24-36 h.
In some embodiments of the present invention, in the step N, the constant temperature is 30 to 40 ℃.
In some embodiments of the invention, in step N, the humidity of the constant humidity is 40% to 50%.
In some embodiments of the present invention, in step N, the drying time is not less than 36 h.
According to some embodiments of the present invention, the polyvinylimidazole is prepared by a precipitation polymerization method, which comprises mixing N-vinylimidazole with toluene solution under the protection of inert gas, stirring and reacting with azobisisobutyronitrile as an initiator, and further purifying the obtained product to obtain polyvinylimidazole.
In some embodiments of the present invention, the stirring reaction temperature is 70 to 80 ℃ during the preparation of the polyvinylimidazole.
In some embodiments of the present invention, the stirring reaction time is 4 to 7 hours in the preparation of the polyvinylimidazole.
In some embodiments of the present invention, in step N, the coating manner includes a doctor blade method and a casting method.
The invention discloses a method for preparing a fixed carrier composite membrane by blending two polymer materials of polyvinyl alcohol and polyvinyl imidazole and optionally adding metal ions (preferably magnesium ions) capable of reacting with the two polymers. The invention has the beneficial effects that:
(1) the invention belongs to CO2The separation membrane technology has the advantages of simple operation process, small occupied area, environmental protection, low energy consumption and the like.
(2) The composite membrane is prepared by blending two polymers, namely polyvinyl alcohol and polyvinyl imidazole, and the composite membrane with high permeability is prepared by fully utilizing the advantages of the two polymers.
(3) When a metal salt, preferably magnesium metal salt, is used as an additive, it is added to the separation layer of the composite membrane. The interaction of metal ions (preferably magnesium ions) and two polymers of polyvinyl alcohol and polyvinyl imidazole is fully utilized, and the gas permeability of the composite membrane is greatly enhanced.
(4) The solid-phase carrier composite membrane prepared by the invention has the advantages that the pressure of raw material gas is 0.1Mpa, and CO is contained2The permeation rate can reach 12GPU and CO2/N2The separation factor of (A) can reach 183.
Drawings
The invention is described in further detail below with reference to the attached drawing figures:
FIG. 1 is a flow chart of a gas permeability testing apparatus used in the present invention.
The reference numerals in fig. 1 illustrate: 1-carbon dioxide gas cylinder; 2-nitrogen gas cylinder; 3, 4, 6, 7, 11, 12, 15-valves; 5-a pressure gauge; 9-a heater; 8, a humidifier; 13-a dehumidifier; 14-a membrane device; 16-bubble flow meter.
FIG. 2 is an electron microscope scanning image of the membrane surface (surface of the separation layer) of the fixed carrier composite membrane prepared by the present invention.
FIG. 3 is an electron microscope scanning image of the membrane section (including the separation layer and a part of the polysulfone film layer) of the fixed carrier composite membrane prepared by the present invention.
FIG. 4 is an X-ray photoelectron spectrum of the composite membrane of the present invention.
Detailed Description
In order that the invention may be readily understood, a more particular description thereof will be rendered by reference to the appended drawings. However, before the invention is described in detail, it is to be understood that this invention is not limited to particular embodiments described. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.
Unless otherwise defined, all terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention, the preferred methods and materials are now described.
Term (I)
The term "Robeson upper limit" used in the present invention means that it is difficult to achieve both high permeability and high selectivity in conventional membrane gas separation, and there is an upper limit because permeability and selectivity cannot be considered at the same time.
The term "polyvinyl alcohol and polyvinyl imidazole blend" as used herein refers to a mixture of two polymers alone, without interaction between the polymers.
The term "polysulfone ultrafiltration membrane" refers to an ultrafiltration membrane which is formed by taking a polysulfone membrane material as a membrane layer and taking non-woven fabric as a base material, wherein the polysulfone membrane material is a membrane prepared by condensing bisphenol and 4, 4' -dichlorodiphenyl sulfone; the polysulfone ultrafiltration membrane has the characteristics of controllable membrane thickness, high porosity of an inner layer, good mechanical stability and the like, and is widely applied to a supporting layer of a composite membrane.
The term "water" as used herein means deionized water, distilled water or ultrapure water unless otherwise specified or limited.
The term "optional" or "optionally" as used herein means that an optional ingredient may or may not be added.
Embodiments II
As mentioned before, is currently used for CO2Poor mechanical stability, CO, present in the membrane technology of separation 2Small gas permeation rate, low separation factor and the like. In view of this, the present inventors have aimed at CO2The membrane technology of separation has been studied extensively. The inventor researches and discovers that the composite membrane is prepared by blending two polymers, namely polyvinyl alcohol and polyvinyl imidazole, and the composite membrane with high permeability can be prepared by fully utilizing the advantages of the two polymers. It is particularly unexpected that metal salts, preferably magnesium metal salts, are added as additives to the separating layer of the composite membrane. The interaction of metal ions (preferably magnesium ions) and two polymers of polyvinyl alcohol and polyvinyl imidazole is fully utilized, and the gas permeability of the composite membrane can be greatly enhanced. The present invention has been made based on the above findings.
Thus, according to the first inventionAspects of some embodiments, the invention relates to methods for CO2The separated fixed carrier composite membrane comprises a supporting layer and a separating layer; the separation layer is a blend of polyvinyl alcohol and polyvinyl imidazole, and in the blend polymer of polyvinyl alcohol and polyvinyl imidazole, the mass ratio of polyvinyl alcohol to polyvinyl imidazole is 4: 3-8: 3; the support layer is a polysulfone ultrafiltration membrane, and the average cut-off molecular weight of the polysulfone ultrafiltration membrane comprises 6000, 20000, 30000 or 50000; the thickness of the separation layer is 3-10 mu m.
According to some preferred embodiments of the first aspect of the invention, the invention relates to a method for CO2The separated fixed carrier composite membrane comprises a supporting layer and a separating layer; the separation layer is a blend of polyvinyl alcohol and polyvinyl imidazole, and metal ions are loaded on both the polyvinyl alcohol and the polyvinyl imidazole in the blend of polyvinyl alcohol and polyvinyl imidazole.
Analyzing the interaction between groups on the polymer chain and metal ions, the present inventors believe that a polymer-metal complex can be formed by coordination between polymer ligands and metal ions, wherein the ligands in the polymer include N, O, S, P or other coordinating atoms that can provide lone electron pairs that are not bonded or a structure having a strongly delocalized pi-electron system. The molecular structure of the polyvinyl imidazole (PVI) is shown as a formula (I), and it can be seen that a PVI polymer macromolecular chain has a plurality of imidazole rings, and the macromolecular chain has a very strong coordination function with metal ions. Therefore, the metal ions supported on the polyvinylimidazole in the blend of polyvinyl alcohol and polyvinylimidazole are supported on the polyvinylimidazole in the blend of polyvinyl alcohol and polyvinylimidazole in a complexed manner.
Similarly, the molecular structure of the polyvinyl alcohol (PVA) is shown in the formula (II), and it can be seen that the macromolecular chain of the PVA polymer has a plurality of OH groups-Wherein the oxygen atom has a lone pair of electrons; secondly, the metal ions have a valence electron orbitalFor lone pair electrons to occupy, so that metal ions can be combined with OH in PVA-Are coordinately bound. Therefore, the metal ions supported on the polyvinyl alcohol in the polyvinyl alcohol and polyvinyl imidazole blend are supported on the polyvinyl alcohol in the polyvinyl alcohol and polyvinyl imidazole blend in a complexing manner.
It can be seen that, in the present invention, the metal ions supported in the blend of polyvinyl alcohol and polyvinyl imidazole are supported on polyvinyl alcohol and polyvinyl imidazole, respectively, in a complexing manner. Moreover, different kinds of metal ions have different effects on PVI and PVA. In the invention, the metal comprises one or more of magnesium, copper and calcium, and preferably, the metal is magnesium.
In the polyvinyl alcohol and polyvinyl imidazole blended polymer, the mass ratio of polyvinyl alcohol to polyvinyl imidazole is 4: 3-8: 3; the mass fraction of the metal ions is 0-1.5% of the total mass of the separation layer; the support layer is a Polysulfone (PS) ultrafiltration membrane, the average cut-off molecular weight of the polysulfone ultrafiltration membrane comprises 6000, 20000, 30000 or 50000, and preferably the average cut-off molecular weight of the polysulfone ultrafiltration membrane is 20000; the thickness of the separation layer is 3-10 mu m.
According to some embodiments of the second aspect of the invention, the invention relates to a method for CO according to the first aspect of the invention2The preparation method of the separated fixed carrier composite membrane comprises the following steps:
(1) respectively dissolving polyvinyl alcohol and polyvinyl imidazole in deionized water to prepare aqueous solution of polyvinyl alcohol and polyvinyl imidazole with the mass fraction of 3% -6%, preferably 4% -6%, and further preferably 4%;
(2) mixing aqueous solutions of polyvinyl alcohol and polyvinyl imidazole according to a certain mass ratio, stirring for 30-60 min at 20-40 ℃, standing for 24h, preferably for more than 24-36h, and removing bubbles to obtain a coating solution; in the coating liquid, the total solid content of polyvinyl alcohol and polyvinyl imidazole is 3-6%, and the mass ratio of polyvinyl alcohol to polyvinyl imidazole is 4: 3-8: 3;
(3) and (2) taking the polysulfone ultrafiltration membrane as a supporting layer, uniformly coating a certain amount of coating liquid on the surface of the supporting layer, and drying for more than 36 hours in a constant temperature and humidity box with the temperature of 30-40 ℃ and the humidity of 40-50% to prepare the fixed carrier composite membrane, wherein the thickness of the separation layer is controlled to be 3-10 microns.
The polysulfone ultrafiltration membrane may have an average cut-off molecular weight of 6000, 20000, 30000, 50000, preferably the polysulfone ultrafiltration membrane has an average cut-off molecular weight of 20000.
The method of applying the coating solution in the present invention is not particularly limited, and the coating solution can be applied to the surface of the support layer by, for example, a doctor blade method or a casting method.
According to some preferred embodiments of the second aspect of the invention, the invention relates to a method for CO according to the first aspect of the invention2The preparation method of the separated fixed carrier composite membrane comprises the following steps:
(1) respectively dissolving polyvinyl alcohol and polyvinyl imidazole in deionized water to prepare aqueous solution of polyvinyl alcohol and polyvinyl imidazole with the mass fraction of 3% -6%, preferably 4% -6%, and further preferably 4%;
(2) mixing a polyvinyl alcohol aqueous solution, a polyvinyl imidazole aqueous solution and a metal salt aqueous solution, stirring at 20-40 ℃ for 30-60 min, standing for more than 24h to remove bubbles, thereby obtaining a coating solution; in the metal salt water solution, the mass fraction of metal ions is 0.01-1%, preferably 0.05-1%; in the coating liquid, the total solid content of polyvinyl alcohol and polyvinyl imidazole is 3-6%, the mass ratio of polyvinyl alcohol to polyvinyl imidazole is 4: 3-8: 3, and the mass fraction of metal magnesium ions is 0-0.06%, preferably 0.003-0.06%;
(3) and (2) taking the polysulfone ultrafiltration membrane as a supporting layer, uniformly coating a certain amount of coating liquid on the surface of the supporting layer, and drying for more than 36 hours in a constant temperature and humidity box with the temperature of 30-40 ℃ and the humidity of 40-50% to prepare the fixed carrier composite membrane, wherein the thickness of the separation layer is controlled to be 3-10 microns.
The metal salt comprises one or more of metal chloride, metal sulfate and metal acetate, and the metal comprises one or more of magnesium, copper and calcium. The inventor researches and discovers that the separation performance of the prepared composite membranes is different by adopting salts of different metals. Preferably, the metal is magnesium, and further preferably, the metal salt includes one or more of magnesium chloride, magnesium sulfate or magnesium acetate.
The polysulfone ultrafiltration membrane may have an average cut-off molecular weight of 6000, 20000, 30000, 50000, preferably the polysulfone ultrafiltration membrane has an average cut-off molecular weight of 20000.
The coating method of the coating solution in the present invention is not particularly limited, and for example, the coating solution may be applied to the surface of the support layer by a doctor blade method or a casting method.
In the present invention, in the step (2), the mixing manner and the order of the polyvinyl alcohol aqueous solution, the polyvinyl imidazole aqueous solution and the metal salt aqueous solution are not particularly limited, and a mixing manner and an order that are conventional in the art may be adopted for mixing, as long as the mixing manner and the order are capable of uniformly mixing, and the coating solution has a total solid content of 3 to 6% of polyvinyl alcohol and polyvinyl imidazole, a mass ratio of 4:3 to 8:3 of polyvinyl alcohol and polyvinyl imidazole, and a mass fraction of metal magnesium ions of 0 to 0.06%.
For example, an aqueous polyvinyl alcohol solution may be simultaneously mixed with an aqueous polyvinyl imidazole solution and an aqueous metal salt solution; for example, the aqueous solution of polyvinyl alcohol and polyvinyl imidazole may be mixed at a predetermined mass ratio, and the mixed solution may be mixed after adding a predetermined mass of the aqueous solution of metal salt.
According to some embodiments of the present invention, the polyvinylimidazole is synthesized by a precipitation polymerization method, which comprises: under the protection of inert gas, mixing N-vinyl imidazole and a toluene solution, taking azobisisobutyronitrile as an initiator, heating and stirring at 70-80 ℃ for 4-7 h, and further purifying a product to obtain the polyvinyl imidazole.
The method for purifying the polymerization product in the present invention is not particularly limited, and the polymerization product may be purified by a conventional purification method in the art, for example, by washing or filtration. The method specifically comprises the following steps: and finally, washing the precipitate with 50mL of acetone for multiple times until all impurities in the precipitate are removed, putting the washed precipitate into a vacuum drying box, setting the drying temperature to be 60 ℃, taking out the precipitate after 48 hours, and obtaining a pure polymerization product which is stored for later use.
In the present invention, the surface and cross-section of the fixed carrier composite membrane were examined by scanning electron microscopy using an S-4700SEM type scanning electron microscope (Hitachi, Japan).
In the present invention, X-ray photoelectron spectroscopy (KRATOS AXIS SUPRA, Shimadzu corporation) was used to analyze the film obtained in the present invention.
The single-component gas permeability testing device shown in FIG. 1 is adopted to perform permeability test on the prepared fixed carrier composite membrane, the feed gas feeding pressure range is 0.1-0.6 Mpa (relative pressure), and the testing temperature is 25 ℃.
The specific test method is as follows: before testing, valves (3, 4, 10, 16) were closed, valves (6, 7, 11, 12) were opened, and the heater was set to a temperature of 50 ℃. One component gas test procedure: opening a valve 3 or 4 of the gas steel cylinder, and enabling the gas to enter a humidifier for humidification; the gas enters a dehumidifier after coming out of the humidifier so as to remove entrained steam in the process of humidifying the gas and liquid water condensed when the gas is cooled in the process of transporting the gas; the gas enters the stainless steel membrane device after passing through the dehumidifier, permeates the composite membrane and permeates to the other side of the membrane; the gas rate was measured by a bubble flow meter.
III example
The present invention will be specifically described below with reference to specific examples. The experimental methods described below are, unless otherwise specified, all routine laboratory procedures. The experimental materials described below, unless otherwise specified, are commercially available.
Example 1: preparation for CO2Separated fixed carrier composite membrane
(1) 10g N-vinylimidazole and 0.2g of azobisisobutyronitrile were weighed in succession and mixed well in a three-necked flask containing 50mL of toluene solvent. The three-necked flask containing the reaction mixture was placed in a condenser under N2Heating at 70 deg.C for 4h in the presence of inert gas while stirring, filtering to obtainCoarse polyvinylimidazole. And washing the polymer with 50mL of acetone for 3 times, and finally putting the washed polymer into a vacuum drying oven, drying for 48 hours at 60 ℃, taking out and storing for later use.
(2) 0.4g of polyvinyl imidazole is dissolved in 9.6g of deionized water, and 0.4g of polyvinyl alcohol is also dissolved in 9.6g of deionized water, and the mixture is stirred for 30min at room temperature to respectively prepare 4% polyvinyl imidazole aqueous solution and polyvinyl alcohol aqueous solution.
(3) Mixing 7g of polyvinyl alcohol aqueous solution and 3g of polyvinyl imidazole aqueous solution, stirring at room temperature for 60min to prepare the coating solution with the total solid content of polyvinyl imidazole and polyvinyl alcohol being 4% and the mass ratio of polyvinyl alcohol to polyvinyl imidazole being 7: 3.
(4) And (3) uniformly coating the coating liquid on the surface of a support layer of the polysulfone ultrafiltration membrane with the average molecular weight cutoff of 20000, and placing the support layer in a constant-temperature and constant-humidity box with the temperature of 30 ℃ and the humidity of 40% for forming a membrane for more than 36 hours to obtain the fixed carrier composite membrane.
Example 2: preparation for CO2Separated fixed carrier composite membrane
(1) 10g N-vinylimidazole and 0.2g of azobisisobutyronitrile were weighed in succession and mixed well in a three-necked flask containing 50mL of toluene solvent. The three-necked flask containing the reaction mixture was placed in a condenser under N2Heating at 70 deg.C for 4h in the presence of inert gas, with stirring, and filtering to obtain crude polyvinylimidazole. And washing the polymer with 50mL of acetone for 3 times, and finally putting the washed polymer into a vacuum drying oven, drying for 48 hours at 60 ℃, taking out and storing for later use.
(2) 0.5g of polyvinyl imidazole is dissolved in 9.5g of deionized water, and 0.4g of polyvinyl alcohol is also dissolved in 9.6g of deionized water, and the mixture is stirred for 30min at room temperature to respectively prepare a polyvinyl imidazole aqueous solution with the mass fraction of 5% and a polyvinyl alcohol aqueous solution with the mass fraction of 4%. Dissolving a certain mass of magnesium salt in deionized water to prepare Mg 2+0.05% of water solution.
(3) Respectively taking 7g of polyvinyl alcohol aqueous solution and 2.4g of polyvinyl imidazoleMixing oxazole aqueous solution and 0.6g of 0.05% magnesium ion aqueous solution, stirring at room temperature for 60min to prepare polyvinyl imidazole and polyvinyl alcohol with the total solid content of 4%, the mass ratio of polyvinyl alcohol to polyvinyl imidazole of 7:3 and Mg2+Coating liquid with the mass fraction of 0.003 percent.
(4) Uniformly coating the coating liquid on the surface of a support layer by using a polysulfone ultrafiltration membrane support layer with the average molecular weight cutoff of 20000, and placing the support layer in a constant-temperature and constant-humidity box with the temperature of 30 ℃ and the humidity of 40% for forming a film for more than 36 hours to obtain the Mg-containing film2+The thickness of the separation layer of the fixed carrier composite membrane is controlled to be about 6 mu m.
The surface and cross section of the prepared fixed carrier composite membrane were subjected to electron microscope scanning detection, and the results are shown in fig. 2 and 3.
As shown in FIG. 2, Mg2+The surface of the-PVI-PVA/PS membrane is smooth and compact and has no defects, and the surface of the composite membrane has no crystallization phenomenon. As can be seen from fig. 3, the PS support layer (the upper channel structure layer in fig. 3) has very good affinity with the separation layer (the lower dense layer in fig. 3), and the bonding is tight, and no separation occurs.
The prepared fixed carrier composite membrane was subjected to characterization by X-ray photoelectron spectroscopy (XPS), and the result is shown in fig. 4.
FIG. 4 shows the addition of Mg2+The results of comparison of the elemental compositions in films prepared from the coating solutions prepared from the mixtures obtained before and after the film formation showed C, N, O, Mg full spectra of four elements. Adding Mg to the film2+Thereafter, the sample can observe a peak of a trace amount of Mg element between 1298-1308 binding energy (eV), but the peak area is extremely small because the mass fraction of Mg element in the film is small.
Example 3: preparation for CO2Separated fixed carrier composite membrane
A fixed support composite membrane was prepared in the same manner as in example 2, except that Mg was used2+Using 0.10% aqueous solution in percentage by mass for coating liquid to obtain Mg2+Coating liquid with the mass fraction of 0.006 percent is used for preparing a fixed carrier composite membrane.
Example 4: preparation for CO2Separated fixed carrier composite membrane
A fixed support composite membrane was prepared in the same manner as in example 2, except that Mg was used2+Using 0.15% aqueous solution in the mass fraction for coating liquid to obtain Mg2+The coating liquid with the mass fraction of 0.009 percent is used for preparing a fixed carrier composite membrane.
Example 5: preparation for CO2Separated fixed carrier composite membrane
A fixed support composite membrane was prepared in the same manner as in example 2, except that Mg was used 2+Using 0.20% aqueous solution in mass fraction for coating liquid to obtain Mg2+The coating liquid with the mass fraction of 0.012 percent is used for preparing a fixed carrier composite membrane.
Example 6: for use in CO2Performance testing of the separated fixed support composite membranes
The fixed carrier composite membranes prepared in examples 1 to 5 were subjected to permeation testing using the single-component gas permeation performance testing apparatus shown in fig. 1: the feeding pressure range of the raw material gas is 0.1-0.6 Mpa (relative pressure), and the testing temperature is 25 ℃. The results are shown in tables 1 to 5.
Table 1 shows CO of the fixed support composite membrane prepared in example 12Permeation rate and separation factor of
| 0.1Mpa | 0.2Mpa | 0.3Mpa | 0.4Mpa | 0.5Mpa | 0.6Mpa | |
| CO2Permeability rate/GPU | 11.4 | 16.8 | 20.6 | 31.1 | 32.8 | 33.9 |
| Separation factor | 73 | 61 | 54 | 54 | 45 | 41 |
Table 2 shows CO of the fixed support composite membrane prepared in example 22Permeation rate and separation factor of
| 0.1Mpa | 0.2Mpa | 0.3Mpa | 0.4Mpa | 0.5Mpa | 0.6Mpa | |
| CO2Permeability rate/ |
10 | 16.7 | 18.8 | 19.9 | 20.1 | 20.4 |
| Separation factor | 82 | 60 | 57 | 51 | 48 | 43 |
Table 3 shows CO of the fixed support composite membrane prepared in example 32Permeation rate and separation factor of
| 0.1Mpa | 0.2Mpa | 0.3Mpa | 0.4Mpa | 0.5Mpa | 0.6Mpa | |
| CO2Permeability rate/GPU | 11.6 | 16.3 | 17 | 17.8 | 20 | 26 |
| Separation factor | 183 | 134 | 114 | 92 | 86 | 74 |
Table 4 shows CO of the fixed support composite membrane prepared in example 42Permeation rate and separation factor of
| 0.1Mpa | 0.2Mpa | 0.3Mpa | 0.4Mpa | 0.5Mpa | 0.6Mpa | |
| CO2Permeability rate/GPU | 12.2 | 14.7 | 18 | 19.2 | 20 | 20.1 |
| Separation factor | 136 | 82 | 78 | 76 | 61 | 59 |
Table 5 shows CO of the fixed support composite membrane prepared in example 52Permeation rate and separation factor of
| 0.1Mpa | 0.2Mpa | 0.3Mpa | 0.4Mpa | 0.5Mpa | 0.6Mpa | |
| CO2Permeability rate/GPU | 8.7 | 8.6 | 9 | 15 | 16.6 | 17.4 |
| Separation factor | 86 | 48 | 35 | 35 | 34 | 34 |
From the detection results of the above examples, the gas permeation rate is increased with the increase of the pressure, and the gas separation factor is decreased with the increase of the pressure of the raw material gas. In general, example 1 (without Mg addition)2+) CO of2The permeation rate is greater, mainly due to the addition of Mg2+Rear, Mg2+After the complex of the PVI and the PVA in the blend, the crosslinking degree of the polymer in the coating liquid is increased, the compactness of the polymer in the separation layer is greatly increased, and the channel which can allow gas to permeate becomes thin, so that the permeation rates of the two gases are reduced to different degrees. In summary, the composite membrane of example 3 has the best gas selective permeability, and CO is present under a pressure of 0.1MPa2Permeation rate of 12GPU, CO2/N2The separation factor of (3) is 183.
The results of the measurement of the film thickness in the above examples show that the thickness of the separation layer of the fixed carrier composite film is within the range of 3 to 10 μm.
It should be noted that the above-mentioned embodiments are only for explaining the present invention, and do not constitute any limitation to the present invention. The present invention has been described with reference to exemplary embodiments, but the words which have been used herein are words of description and illustration, rather than words of limitation. The invention can be modified, as prescribed, within the scope of the claims and without departing from the scope and spirit of the invention. Although the invention has been described herein with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed herein, but rather extends to all other methods and applications having the same functionality.
Claims (10)
1. For CO2The separated fixed carrier composite membrane comprises a supporting layer and a separating layer, wherein the separating layer is a blend of polyvinyl alcohol and polyvinyl imidazole.
2. The fixed support composite membrane according to claim 1, wherein both polyvinyl alcohol and polyvinyl imidazole in the polyvinyl alcohol and polyvinyl imidazole blend are loaded with metal ions; preferably, the metal comprises one or more of magnesium, copper and calcium, and further preferably, the metal is magnesium.
3. The composite membrane according to claim 1 or 2, wherein in the blended polymer of polyvinyl alcohol and polyvinyl imidazole, the mass ratio of polyvinyl alcohol to polyvinyl imidazole is 4: 3 to 8: 3; preferably, the mass fraction of the metal ions is 0-1.5% of the total mass of the separation layer; and/or the support layer is a polysulfone ultrafiltration membrane, and the average cut-off molecular weight of the polysulfone ultrafiltration membrane comprises 6000, 20000, 30000 or 50000; and/or the thickness of the separation layer is 3-10 mu m.
4. Use according to any of claims 1-3 for CO2A method of preparing a separated fixed support composite membrane comprising:
step M, mixing a polyvinyl alcohol aqueous solution, a polyvinyl imidazole aqueous solution and an optional metal salt aqueous solution, stirring, standing to remove bubbles, and obtaining a coating solution;
And step N, uniformly coating the coating liquid on the surface of the support layer, and drying at constant temperature and constant humidity to prepare the fixed carrier composite membrane.
5. The preparation method according to claim 4, wherein the aqueous solution of polyvinyl alcohol is prepared by dissolving polyvinyl alcohol in water, and preferably, the mass fraction of the aqueous solution of polyvinyl alcohol is 3-6%; and/or the polyvinyl imidazole aqueous solution is prepared by dissolving polyvinyl imidazole in water, preferably, the mass fraction of the polyvinyl imidazole aqueous solution is 3-6%; and/or in the coating solution, the total solid content of polyvinyl alcohol and polyvinyl imidazole in the total mass of the coating solution is 3-6%; and/or in the coating liquid, the mass ratio of polyvinyl alcohol to polyvinyl imidazole is 4: 3-8: 3; preferably, the mass fraction of magnesium ions based on the total mass of the coating solution is 0-0.06%.
6. The production method according to claim 4 or 5, wherein the aqueous metal salt solution is made by dissolving a metal salt in water; preferably, the mass fraction of metal ions in the metal salt solution is 0.01% -1%; and/or the metal salt comprises one or more of metal chloride, metal sulfate and metal acetate, and the metal comprises one or more of magnesium, copper and calcium; preferably, the metal salt comprises one or more of magnesium chloride, magnesium sulfate or magnesium acetate.
7. The preparation method according to one or more of claims 4 to 6, wherein in the step M, the stirring temperature is 20 to 40 ℃; and/or the stirring time is 30-60 min; and/or the standing time is not less than 24 hours, and preferably the standing time is 24-36 hours.
8. The preparation method according to one or more of claims 4 to 7, wherein in the step N, the constant temperature is 30 to 40 ℃; and/or the constant humidity is 40-50%; and/or the drying time is more than or equal to 36 h.
9. The process according to one or more of claims 4 to 8, wherein the polyvinylimidazole is prepared by precipitation polymerization, which comprises mixing N-vinylimidazole with toluene solution under the protection of inert gas, stirring and reacting with azobisisobutyronitrile as initiator, and further purifying the obtained product to obtain polyvinylimidazole; preferably, the temperature of the stirring reaction is 70-80 ℃; and/or the stirring reaction time is 4-7 h.
10. A method according to one or more of claims 4-8, wherein in step N, said coating is applied by a doctor blade method or a casting method.
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