CN101121101A - Method for preparing polyurethane-imide permeable vaporizing aromatic/alkane separating membrane - Google Patents
Method for preparing polyurethane-imide permeable vaporizing aromatic/alkane separating membrane Download PDFInfo
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- CN101121101A CN101121101A CNA2007101184801A CN200710118480A CN101121101A CN 101121101 A CN101121101 A CN 101121101A CN A2007101184801 A CNA2007101184801 A CN A2007101184801A CN 200710118480 A CN200710118480 A CN 200710118480A CN 101121101 A CN101121101 A CN 101121101A
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Abstract
A preparation method of a polyurethane-imide infiltrated and vaporized aromatic hydrocarbon and alkane separation membrane belongs to the infiltrated and vaporized membrane separation technical field. The factors of the prior polyurethanes membrane separation is low, and a plurality of the prior polyurethanes membrane separations need a test of an infiltrated and vaporized separation performance at high temperature. The present invention includes firstly a prepolymer synthesis of polyurethane and imide is that under the conditions of a nitrogen protection, a mechanical mixing and a condensation circumfluence, a terminated prepolymer is obtained by a reaction of poly (ethylene adipate) glycol diol and diisocyanate, and pyromellitic dianhydride is added for a chain extension to obtain the polyurethane-imide prepolymer solution; secondly the preparation of a polyurethane-imide membrane is that the solution casts to form the membrane and an impregnant is volatilized under an infrared light, and the preparation of membrane can be finished after a heat treatment of 150 DEG C for 1.5 to 2 hours. The material synthesis and the membrane-preparation process of the present invention are simple, and the prepared membrane has a good thermal and chemical stability, and the prepared membrane can separate an aromatic hydrocarbon and alkane mixture under a proper temperature condition with a good separation effect as well as with a considerable practical value.
Description
The technical field is as follows:
the invention relates to a preparation method of a polyurethane-imide membrane for pervaporation aromatic hydrocarbon/alkane separation, belonging to the technical field of pervaporation membrane separation.
The background art comprises the following steps:
the separation of aromatic hydrocarbon/alkane mixture has important significance in the field of petrochemical industry. Particularly in recent years, along with the enhancement of environmental protection consciousness of people, various countries in the world develop standards to limit the content of aromatic hydrocarbon in fuel gasoline so as to avoid environmental pollution and public health damage, the world fuel oil specification III requires that the content of aromatic hydrocarbon in gasoline is less than or equal to 35 percent, china also develops new fuel oil standards to require that the content of aromatic hydrocarbon in gasoline is less than or equal to 40 percent, and the standards and requirements become stricter along with the technical progress; in addition, from the perspective of chemical production, in the process of preparing ethylene by cracking, the aromatic hydrocarbon components in naphtha can not be converted into olefin, and coking can influence heat transfer, so that higher production efficiency can be ensured only by reducing the aromatic hydrocarbon content in naphtha. In addition, many important crude chemical products are aromatic hydrocarbon/alkane mixtures, and the product index can also be achieved by separation and purification, such as benzene and cyclohexane mixture systems, the boiling points of which are only different by 0.6 ℃, and an azeotropic mixture is formed when the mass content of benzene is 50%, so that the separation of benzene/cyclohexane is always a problem in the chemical industry.
At present, three processes of azeotropic distillation, extractive distillation and liquid-liquid extraction are commonly adopted for industrial aromatic hydrocarbon/alkane separation, and the traditional processes have the defects of large energy consumption, high investment cost, complex flow, addition of auxiliary reagents, limited feed concentration range and the like.
Pervaporation is a new membrane technology for the separation of liquid (gas) mixtures. The method is a process for realizing separation by utilizing different dissolution and diffusion speeds of components through a compact membrane, and has the outstanding advantage of realizing separation tasks which are difficult to realize by traditional methods such as distillation, extraction, absorption and the like with low energy consumption. Compared with the traditional method, the pervaporation membrane separation technology has the remarkable advantages of low investment, low operation cost, high separation efficiency, easiness in scale production, good expandability, convenience in control, easiness in replacement and the like.
The main action element of the pervaporation process is a membrane, and two indexes of evaluating the performance of the pervaporation membrane are mainly two indexes, namely the permeation flux and the selectivity of the membrane.
1) Permeate flux, defined as the formula:
wherein M is the mass of permeate permeating through the membrane; a is the membrane area, m 2 (ii) a t is the operation time, h; j is the permeation flux, kg/(m) 2 H) or g/(m) 2 ·h)。
2) An isolation factor α, defined by the formula:
wherein A represents a preferential permeation component; y is A And Y B The mole fractions of the A and B components in the permeate are respectively;
X A and X B Respectively the mole fractions of the A component and the B component in the feed liquid.
Since pervaporation membranes can be prepared either as homogeneous, dense membranes or as composite membranes, the thickness of which is difficult to measure accurately, it is common to compare the permeation performance of different membranes, i.e., J = permeation rate (kg/m) of the membrane 2 H) film thickness (. Mu.m).
Exxon, USA, developed a series of polyester polymers for pervaporation separation of toluene/octane mixed systems. Wherein, for example, when a toluene/octane mixture having a toluene content of 20% is used as the feed liquid, as the crosslinked saturated polyester (U.S. Pat. No. 5,5128439), the permeation flux at 190 ℃ is 75.8 kg. Mu. M.m -2 ·h -1 The separation factor is 6.1;
polypolyarylate (US patent 5012036) a toluene/isooctane mixture having a toluene content of 20% at 150 ℃ and a permeation flux of 28.1 kg. Mu. M -2 ·h -1 The separation factor is 7.4;
U.S. Pat. No. 5,5670052 synthesizes a polyester-based polyimide when used for the separation of trimethylbenzene/decaneAt 140 ℃, the separation factor of the feed liquid with 50 percent of aromatic hydrocarbon content is 4.2, and the permeation flux is 45.8 kg.mu m.m -2 ·h -1 。
In addition, polyurethane/urea materials (e.g., muszynski J, et al, J.Appl.Polym.Sci.1999, 71 (10): 1615-1625) have also been investigated with a permeation flux of 25.5 kg. Mu. M.m. -2 ·h -1 The separation factor was 5.8.
The invention content is as follows:
the invention aims to synthesize a polyurethane-imide membrane capable of realizing pervaporation separation of an aromatic hydrocarbon/alkane mixture, and test the pervaporation separation performance of membranes with different hard segment structures on aromatic hydrocarbon/alkane. The polyurethane-imide film prepared by the invention has excellent mechanical strength, heat resistance and chemical stability. And the membrane material has the structural characteristic of microphase separation, on one hand, the soft segment is not only favorable for permeation of small molecules, but also has affinity to aromatic hydrocarbon, and can ensure that the membrane has better selective permeability, and on the other hand, the hard segment can inhibit swelling of the membrane and ensure the tolerance of the membrane. Therefore, the polyurethane-imide membrane achieves good separation performance in the permeation vaporization separation of the aromatic hydrocarbon/alkane. In addition, the raw materials for synthesizing the material have low cost and potential for industrial application.
The preparation method of the polyurethane-imide film of the invention is as follows:
1) Synthesis of polyurethane-imide prepolymer
Adding polyethylene glycol adipate glycol and a diisocyanate monomer into a three-necked bottle provided with a nitrogen protection, mechanical stirring and a condensation reflux pipe, wherein the mole number of the diisocyanate monomer is 2 times that of the polyethylene glycol adipate glycol, reacting the two monomers for 1.5-2 hours under the conditions of vigorous stirring and water bath heating at 65-80 ℃ to obtain a diisocyanate-terminated prepolymer, and adding N, N-dimethylformamide into the terminated prepolymer to form a prepolymer solution with the solid content of 50%. Then preparing pyromellitic dianhydride with the same molar equivalent as poly (ethylene glycol adipate) glycol into a solution of N, N-dimethylformamide, adding the solution into the solution of the end-capping prepolymer, and raising the reaction temperature to 85-95 ℃ for chain extension reaction for 2-3 hours to finally obtain viscous polyurethane-imide prepolymer solution.
2) Preparation of polyurethane-imide films
Diluting the polyurethane-imide prepolymer solution obtained in the step 1) to a mass concentration fraction of 15%, filtering, defoaming, casting the solution on a polytetrafluoroethylene plate to form a film, volatilizing the solvent for 1-1.5 hours under an infrared lamp, transferring the film to a 150 ℃ oven, and carrying out heat treatment for 1.5-2 hours to complete generation of imide bonds, thereby finally obtaining the transparent polyurethane-imide film.
The prepared polyurethane imide membrane can achieve a good separation effect under mild operation conditions. At an operating temperature of 40-60 deg.C, the separation factor of benzene/cyclohexane mixture with 50% benzene mass is 8.3-6.5, and the permeation flux is 12.1-41.9 kg. Mu. M -2 ·h -1 。
According to the invention, polyethylene glycol adipate glycol is selected as a soft segment, ester groups in the chemical structure of the polyethylene glycol adipate glycol have good affinity to aromatic hydrocarbons, and the four methylene groups can not cause excessive swelling of the soft segment, so that the mechanical strength of the membrane in a pervaporation test is ensured, and the affinity of the membrane to the aromatic hydrocarbons is also ensured; diisocyanate and pyromellitic dianhydride are selected as the hard segment, on one hand, in order to generate a polyimide group with polarity and rigid structure, on the other hand, the length of the hard segment is increased, so that a hard segment gathering area is easier to form, and the membrane material is ensured to have a microphase separation structure. The prepared membrane material is characterized by using a differential scanning calorimeter, and the membrane material has two glass transition temperatures, wherein the glass transition temperature of a soft section is about-45 ℃, and the glass transition temperature of a hard section is about 150 ℃, so that the existence of a microphase separation structure is fully proved.
The polyurethane imide membrane prepared by the invention shows good separation performance when a benzene/cyclohexane mixture is separated. To mass percent of benzeneThe separation factor can reach 6.5 and the permeation flux can reach 41.9 kg.mu m.m. -2 ·h -1 . Compared with other membrane materials, the polyurethane imide membrane can effectively separate benzene/cyclohexane azeotropic mixture with the mass percent of 50% from benzene under a mild condition without high-temperature pressurization operation, so that the energy consumption is greatly reduced, and the cost of raw materials for synthesizing the polyurethane imide is low, and the polyurethane imide membrane has the potential of industrialization.
Detailed Description
Example 1
1) Synthesis of polyurethane-imide prepolymer
10g of polyethylene glycol adipate (PEA) (subjected to a reduced pressure dehydration treatment at 110 ℃ C. Before use) and a diphenylmethane diisocyanate (MDI) monomer (MDI having a molar number 2 times that of the PEA) were charged into a 150ml three-necked flask equipped with a nitrogen blanket, a mechanical stirring and a reflux condenser tube, reacted for 1.5 hours under vigorous stirring and heating in a water bath at 80 ℃ to obtain an MDI-terminated prepolymer, and then 7ml of N, N-Dimethylformamide (DMF) (purified by reduced pressure distillation before use) was added to the terminated prepolymer to dilute it. Then 1.1g of pyromellitic dianhydride (purified by sublimation under reduced pressure before use) equivalent to the polyethylene glycol adipate glycol and another 7ml of DMF (dimethyl formamide) are added into the solution of the end-capping prepolymer, and the reaction temperature is raised to 85 ℃ to carry out chain extension reaction for 2 hours, thus finally obtaining viscous polyurethane-imide prepolymer solution.
2) Preparation of polyurethane-imide films
Diluting the polyurethane-imide prepolymer solution obtained in the step 1) to a mass concentration fraction of 15%, filtering, defoaming, casting the solution on a polytetrafluoroethylene plate to form a film, volatilizing the solvent under an infrared lamp for 1 hour, transferring the film to a 150 ℃ oven, carrying out heat treatment for 1.5 hours to complete generation of imide bonds, finally obtaining a transparent polyurethane-imide film, peeling the film from the polytetrafluoroethylene plate, and measuring the film thickness to be 110 microns.
The aromatic hydrocarbon/alkane pervaporation separation performance of the polyurethane-imide membrane prepared by the method is tested, the benzene/cyclohexane mixture with the benzene mass content of 50% is used as the feed, and the separation results at different temperatures are shown in the table 1:
| operating temperature (. Degree.C.) | Permeate flux J (kg·μm·m -2 ·h -1 ) | Separation factor alpha |
| 40 | 12.1 | 8.3 |
| 50 | 27.7 | 6.9 |
| 60 | 41.9 | 6.5 |
TABLE 1 separation Performance of polyurethane-imide membranes for benzene/cyclohexane systems
Example 2
1) Synthesis of polyurethane-imide prepolymer
A150 ml three-necked flask equipped with a nitrogen blanket, mechanical stirring and a reflux condenser was charged with 10g of polyethylene glycol adipate diol (PEA, molecular weight 1000 g/mol) (dehydrated under reduced pressure at 110 ℃ C. Before use) and 2, 4-toluene diisocyanate (TDI, isomerization ratio 80/20) monomer (TDI having a molar number 2 times that of PEA), allowed to react for 2 hours under vigorous stirring and heating in a water bath at 65 ℃ C. To obtain a TDI terminated prepolymer, and then 7ml of N, N-Dimethylformamide (DMF) (purified by reduced pressure distillation before use) was added to the terminated prepolymer to dilute it. Then 1.1g of pyromellitic dianhydride (purified by sublimation under reduced pressure before use) having a molar equivalent to polyethylene glycol adipate glycol and another 7ml of DMF (dimethyl formamide) are added into the solution of the end-capping prepolymer, and the reaction temperature is raised to 95 ℃ to carry out chain extension reaction for 3 hours, thereby finally obtaining a viscous polyurethane-imide prepolymer solution.
2) Preparation of polyurethane-imide films
Diluting the polyurethane-imide prepolymer solution obtained in the step 1) to a mass concentration fraction of 15%, filtering, defoaming, casting the solution on a polytetrafluoroethylene plate to form a film, volatilizing the solvent under an infrared lamp for 1.5 hours, transferring the film to a 150 ℃ oven, carrying out heat treatment for 2 hours to complete generation of imide bonds, finally obtaining a transparent polyurethane-imide film, peeling the film from the polytetrafluoroethylene plate, and measuring the thickness of the film to be 100 microns.
The aromatic hydrocarbon/alkane pervaporation separation performance of the polyurethane-imide membrane prepared by the method is tested, the benzene/cyclohexane mixture with the benzene mass content of 50% is used as the feed, and the separation results at different temperatures are shown in the table 2:
TABLE 2 separation Performance of polyurethane-imide membranes for benzene/cyclohexane systems
| Operating temperature (. Degree.C.) | Permeation flux J (kg·μm·m -2 ·h -1 ) | Separation factor alpha |
| 40 | 4.6 | 5.8 |
| 50 | 5.6 | 5.4 |
| 60 | 11.3 | 5.2 |
Claims (2)
1. The preparation method of the polyurethane imide pervaporation aromatic hydrocarbon/alkane separation membrane is characterized by comprising the following steps:
1) Synthesis of polyurethane-imide prepolymer
Adding polyethylene glycol adipate glycol and a diisocyanate monomer into a three-necked bottle provided with a nitrogen protection, mechanical stirring and condensation reflux pipe, wherein the mole number of the diisocyanate monomer is 2 times that of the polyethylene glycol adipate glycol, reacting the two monomers for 1.5-2 hours under the conditions of severe stirring and water bath heating at 65-80 ℃ to obtain a diisocyanate-terminated prepolymer, and adding N, N-dimethylformamide into the terminated prepolymer to form a prepolymer solution with the solid content of 50%; then preparing pyromellitic dianhydride with the same molar equivalent as poly (ethylene glycol adipate) glycol into a solution of N, N-dimethylformamide, adding the solution into the solution of the end-capping prepolymer, and raising the reaction temperature to 85-95 ℃ for chain extension reaction for 2-3 hours to finally obtain a viscous polyurethane-imide prepolymer solution;
2) Preparation of polyurethane-imide films
Diluting the polyurethane-imide prepolymer solution obtained in the step 1) to a mass concentration fraction of 15%, carrying out filtration and defoaming, carrying out tape casting on the solution on a polytetrafluoroethylene plate to form a film, volatilizing the solvent under an infrared lamp for 1-1.5 hours, moving the film to a 150 ℃ oven, and carrying out heat treatment for 1.5-2 hours to complete generation of imide bonds, thus finally obtaining the transparent polyurethane-imide film.
2. The production method according to claim 1, characterized in that: in the step 1) of synthesizing the polyurethane-imide prepolymer, the weight average molecular weight of the adopted polyethylene glycol adipate diol is 1000-2000g/mol, and the diisocyanate monomer is any one of toluene diisocyanate and diphenylmethane diisocyanate.
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| CN2007101184801A CN101121101B (en) | 2007-07-06 | 2007-07-06 | Method for preparing polyurethane-imide permeable vaporizing aromatic/alkane separating membrane |
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| CN2007101184801A CN101121101B (en) | 2007-07-06 | 2007-07-06 | Method for preparing polyurethane-imide permeable vaporizing aromatic/alkane separating membrane |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105367733A (en) * | 2015-12-16 | 2016-03-02 | 合肥工业大学 | Preparation method and application of waterborne polyurethane film based on phthalic anhydride polyester polyalcohol |
| US10478778B2 (en) | 2015-07-01 | 2019-11-19 | 3M Innovative Properties Company | Composite membranes with improved performance and/or durability and methods of use |
| US10618008B2 (en) | 2015-07-01 | 2020-04-14 | 3M Innovative Properties Company | Polymeric ionomer separation membranes and methods of use |
| US10737220B2 (en) | 2015-07-01 | 2020-08-11 | 3M Innovative Properties Company | PVP- and/or PVL-containing composite membranes and methods of use |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100792056B1 (en) * | 2004-01-08 | 2008-01-04 | 히다치 가세고교 가부시끼가이샤 | Polyurethane imido resin, adhesive composition and adhesive composition for connecting circuits |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10478778B2 (en) | 2015-07-01 | 2019-11-19 | 3M Innovative Properties Company | Composite membranes with improved performance and/or durability and methods of use |
| US10618008B2 (en) | 2015-07-01 | 2020-04-14 | 3M Innovative Properties Company | Polymeric ionomer separation membranes and methods of use |
| US10737220B2 (en) | 2015-07-01 | 2020-08-11 | 3M Innovative Properties Company | PVP- and/or PVL-containing composite membranes and methods of use |
| CN105367733A (en) * | 2015-12-16 | 2016-03-02 | 合肥工业大学 | Preparation method and application of waterborne polyurethane film based on phthalic anhydride polyester polyalcohol |
| CN105367733B (en) * | 2015-12-16 | 2018-02-06 | 合肥工业大学 | A kind of preparation method and purposes based on benzoic anhydride polyester polyol aqueous polyurethane film |
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