CN101007243A - Preparation method of polyvinyl chitosan mixed film - Google Patents
Preparation method of polyvinyl chitosan mixed film Download PDFInfo
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- CN101007243A CN101007243A CN 200610002664 CN200610002664A CN101007243A CN 101007243 A CN101007243 A CN 101007243A CN 200610002664 CN200610002664 CN 200610002664 CN 200610002664 A CN200610002664 A CN 200610002664A CN 101007243 A CN101007243 A CN 101007243A
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Abstract
The invention involves a preparation method used for separating the polyvinyl alcohol/chitosan mixing film of methanol/dimethyl carbonate, the preparation process is as follows: 1) dissolving the polyvinyl alcohol with the deionized water as solvent in 80 ~ 100 degree C and gaining uniform casting film solution which polyvinyl alcohol concentration is 5wt%; 2) dissolving the chitosan with the glacial acetic acid and deionized water as solvent in 20-40DEG C and gaining uniform casting film solution which chitosan concentration is 1wt%; 3) according certain radio mixing the ratio of PVA and chitosan solution uniformly and debubbling; 4) making film on the glass plate with casting method; 5) thermal treating the film 2~4 hours in 120 ~ 150 degree C. Compared with traditional separation methods, the method has some characteristics such as high one-time separation degree, simple precess, low energy consumption and pollution-free.
Description
Technical field
The present invention relates to the infiltration vaporization separation film technology, specifically a kind of method with polyvinyl alcohol/chitosan mixed film infiltration evaporation separation of methanol/dimethyl carbonate azeotropic system.
Background technology
Infiltration evaporation (pervaporation, be called for short PV) method is to utilize in the liquid difference of two kinds of components solubility and diffusion coefficient in film, by infiltration with vaporize a kind of method that two kinds of components are separated.The research of infiltration evaporation can be traced back to earlier 1900s, but is just paid attention to widely up to this emerging membrane separation technique of the eighties.Separating method with the distillation of routine, extraction, dialysis etc. compares, the infiltration evaporation method has disposable separation degree height, process is simple, energy consumption is low, characteristics such as pollution-free, it is mainly used in: dehydration of organic solvent, the removing and 3 aspects such as separation of organic/organic mixed system of underwater micro-organic matter.
Dimethyl carbonate (being called for short DMC) is a kind of novel green chemical products that domestic and international chemical circles is widely paid close attention to over past ten years, it not only replaces the dimethyl suflfate photoreactive gas of severe toxicity as methylating agent, in agricultural chemicals, medicine, Polymer Synthesizing, be used widely, and because the new purposes continually developed of DMC in recent years, especially be used for producing special chemical article, as the lubricating oil base of high performance thermoplastic resin, function admirable and octane number and the oxygen content that is used as gasoline additive raising gasoline, various countries scientific worker pay attention to day by day is to the research and development of DMC.
The industrial process of DMC mainly contains liquid phase methanol carbonyl oxidizing process, gas-phase methanol carbonyl oxidizing process, ester-interchange method etc., and wherein ester-interchange method is the simplest on flow process.Domestic production DMC mainly adopts ester-interchange method at present.But no matter adopt which kind of method, methyl alcohol all can not transform fully during industrial production DMC, and initial products obtained therefrom all is the mixture of methyl alcohol and DMC.Under atmospheric pressure, (methyl alcohol 70wt% DMC30wt%), adopts common distillation and separation method to be difficult to reach the requirement that the product level is separated because methyl alcohol and DMC form binary constant boiling mixture.Traditional separation of methanol/DMC binary azeotrope method has the crystallizing process under low temperature, azeotropic distillation, utilizes inert gas compression rectification method, extraction fractional distillation and membrane separation process etc. at present.Wherein that is that all right is ripe for membrane separation technique, does not see the industrialization report.Deutsche Bundespatent 2450856 utilizes freezing point (97.8 ℃) the high characteristics of the freezing point (4 ℃) of DMC than methyl alcohol, select suitable temperature to make the DMC solidification and crystallization, redistillation obtains DMC behind the fractional crystallization, the rate of recovery of DMC can reach 95%-96%, but azeotrope will be-35 ℃ of following crystallizations in the crystallizing process under low temperature, and then the intensification second distillation, and energy consumption is big, operating difficulties, the flow process complexity.Japan Patent 270249 adds entrainer such as C5-C8 alkane or cycloalkane in methyl alcohol/DMC azeotropic mixture, make methyl alcohol and alkane form the new azeotropic mixture lower than methyl alcohol/DMC azeotropic mixture azeotropic temperature, and look for novelty azeotropic mixture and former azeotropic mixture temperature differ more than 10 ℃, in this technology, azeotropic mixture (methyl alcohol-alkane azeotropic mixture) steams from cat head, after the condensation, overhead product methyl alcohol and alkane dissolve each other fully, the method that needs water to mix reclaims methyl alcohol, divide dried up and methyl alcohol through general rectifying again, azeotropic distillation Tata still goes out the DMC product.Deutsche Bundespatent 2607003 utilizes the characteristics of methyl alcohol/DMC azeotropic mixture to Raoult's law generation overgauge, with the compression rectification method DMC is separated with methyl alcohol.De Gushi company was with in the synthetic DMC product of ester-interchange method in 1992, reactant distills under 80 ℃ of conditions of normal pressure, distill under DMC that cat head distillates and methanol azeotrope are being higher than 140 ℃, the condition of 10MPa, obtain the DMC product at the bottom of the tower, the methyl alcohol that cat head obtains is recycled to reactor through recovery.Compare with extracting rectifying, compression rectification method pressurized operation, investment increases greatly, and operation easier is big, and security is relatively poor.United States Patent (USP) 5292917 disclose a kind of in the presence of dimethyl oxalate the extraction rectifying method of the mixture of distillating carbinol/DMC.Series connection uses two rectifying columns to separate DMC from the methyl alcohol kind, and on the top of first rectifying column, methyl alcohol is removed, and the mixture of DMC/ dimethyl oxalate is dosed into second rectifying column, and DMC separates from dimethyl oxalate in second rectifying column.Japan Patent 06016596 disclosed in the presence of a kind of organic solvent such as the phenol in 1994, by the method that backflow methyl alcohol/the DMC mixture is separated DMC from methyl alcohol.As overhead, and organic solvent and DMC mixture are as the bottomsstream methyl alcohol for this method.Japan Patent 06228026 also discloses the extraction rectifying method of a kind of methyl alcohol and DMC mixture, and this method is to carry out in a kind of comprising in the presence of the extractant of electing the compound of methyl phenyl ethers anisole from one group.
People such as membrane separation process Nicke Andreas report, in temperature is 40～130 ℃, and reinforced limit pressure is 50～1000kPa permeate side pressure≤10kPa, under the infiltration evaporation state, the film of available plasma polymerization preparation comes separation of methanol/DMC mixture, when temperature t=50 ℃, reinforced limit pressure p
1=300kPa, permeate side pressure p
2＜2kPa, seepage discharge 0.5kg/ (m
2H) under the situation, form DMC before the infiltration: methyl alcohol=90: 10 becomes DMC after the infiltration: methyl alcohol=8: 92.Rautenbach Robert uses less than the thick plasma membrane of 1 μ m and carries out separation of methanol/DMC azeotropic mixture, and its selectivity studied, find the dimethyl siloxane polymeric membrane, contain all separable methyl alcohol of the film/DMC azeotropic mixture of four ammonium equilibrium ions or alkali metal equilibrium ion.2002, Wooyoung Won etc. has reported the infiltration evaporation Separation Research than system of chitosan film to methyl alcohol/DMC system on Journal of Membrane Science, research is thought, chitosan film shows good permeability and separation performance to methyl alcohol/DMC, and its energy consumption and separation factor are far superior to traditional rectificating method.
Summary of the invention
The object of the present invention is to provide a kind of polyvinyl alcohol/shitosan (PVA/CS) blend film preparation method who is used for separation of methanol/dimethyl carbonate.
For achieving the above object, the technical solution used in the present invention is:
Method with blend has prepared the PVA/CS blend film, this film has reached the purpose of PVA and CS performance complement, PVA membrane crystallization degree height, permeation flux is low, feed liquid is moved under higher temperature, and CS membrane crystallization degree is low, the flux height, separation is lower, so this blend film infiltration evaporation separation of methanol/DMC mixture has bigger permeation flux and separation.
Specifically, its step of preparation method of the present invention is as follows:
A) preparation of casting solution: make dissolution with solvents PVA at 80～100 ℃ with deionized water, being prepared into concentration is the PVA casting solution of 5wt%; Make dissolution with solvents CS at 20～40 ℃ with glacial acetic acid and deionized water, being prepared into concentration is the CS casting solution of 1wt%, and wherein the concentration of glacial acetic acid in the CS casting solution is 2wt%;
B) press mass ratio 2: 1-1: 2 with PVA casting solution and CS casting solution mix, deaeration;
C) on glass plate, make film with casting method;
D) film is heat-treated under 120～150 ℃.
Described preparation method, wherein the alcoholysis degree of PVA is 99.8%-100% among the step a; CS low-molecular-weight, deacetylation are 75%-85%.
Described preparation method, wherein casting solution mixes and stirs 3～4h, vacuum defoamation 2h among the step b.
Described preparation method, wherein the temperature of the glass plate among the step c is 40 ℃, solvent evaporates 12～16h.
Described preparation method, wherein heat treatment is carried out in vacuum drying oven in the steps d, and heat treatment time is 2～4h.
The PVA/CS blend film of the present invention preparation, its mechanical strength height, chemical stability are good, and preparation method's process is simple, pollution-free.PVA/CS blend film of the present invention can be used for infiltration evaporation separation of methanol/dimethyl carbonate (DMC) azeotropic mixture, has separating property preferably.
Description of drawings
Accompanying drawing 1 is the device flow chart of embrane method infiltration evaporation separation of methanol of the present invention/DMC system.
The specific embodiment
PVA/CS blend film preparation process of the present invention is as follows:
A) preparation of casting solution: make dissolution with solvents PVA at 80～100 ℃ with deionized water, get the even casting solution of PVA concentration 5wt%; Make dissolution with solvents CS at 20～40 ℃ with glacial acetic acid and deionized water, get the even casting solution of CS concentration 1wt%;
B) by a certain percentage PVA and CS solution are mixed, deaeration;
C) on the glass plate of cleaning, make film with casting method;
D) film is heat-treated at a certain temperature.
In the process of step a) casting solution preparation, the alcoholysis degree of PVA is 99.8%-100%; The CS low-molecular-weight, deacetylation 75%-85%.The concentration of glacial acetic acid in CS solution is 2wt%, and the PVA solution and the CS solution that prepare preferably filter, to remove some insoluble impurity.
PVA and CS solution mix in step b) needs evenly to stir 3～4h, is preferably in deaeration 2h under the vacuum state.
Make film with casting method in step c), glass plate will keep level, cleaning, and the temperature of glass plate is 40 ℃, and casting solution is poured on the glass plate, makes solvent evaporates 12～16h.
(to vacuumize) heat treatment temperature in vacuum drying oven be 120～150 ℃ to film in step d), heat treatment time 2～4h.
The PVA/CS blend film is used for infiltration evaporation separation of methanol/DMC azeotropic mixture among the present invention, and its device flow chart uses the stainless steel osmotic cell as shown in Figure 1, and film is supported on the sintered stainless steel porous plate, and the effective film area is 13.85cm
2Certain density methyl alcohol/dimethyl carbonate feed liquid circulates between material fluid bath 2 and osmotic cell 5 by high-pressure circulation pump 4, and material fluid bath 2 is heated by heater 3.Under the control of radiator valve 1, after feed liquid reaches predetermined temperature, open vavuum pump, show vacuum by vacuum meter 6, reach stable state through permeating 1～4h, test.Owing to compare with feed liquid, infiltration capacity is less than 1%, and feed concentration changes little.Penetrant, is extracted out by vavuum pump 8 after the film rear side is vaporized by film, and penetrant is collected with liquid nitrogen condensation and by cold-trap 7, accurately the penetrating fluid weight of weighing collection.Adopt the beautiful GC7890II gas chromatograph in sky, Shanghai to analyze raw material and penetrating fluid composition.The infiltration evaporation performance evaluation of film is drawn by following formula:
15
Separation (α)=(Y
MeOH/ Y
DMC/ (X
MeOH/ X
DMC)
In the formula:
X
MeOHMass fraction for feed side methyl alcohol;
X
DMcMass fraction for the feed side dimethyl carbonate;
Y
MeOHMass fraction for per-meate side methyl alcohol;
Y
DMcMass fraction for the per-meate side dimethyl carbonate;
The infiltration evaporation segregation index PSI value of evaluated for film production capacity is calculated as follows:
PSI＝J×(α-1)
The present invention has following advantage:
1. the present invention selects PVA and the CS raw material as film for use, and is cheap, do not pollute, not nontoxic, and CS is a kind of natural macromolecular material, contains stronger hydroxyl of reactivity and free amine group, can be dissolved in dilute acetic acid solution, is easy to film forming, easily reaction modifying.
2. the present invention has prepared the PVA/CS blend film with the method for blend, and this film has reached the purpose of PVA and CS performance complement, and CS is the semi-rigid macromolecule that contains heterocycle, degree of crystallinity is lower, molecules align is loose, and free volume is big, and permeation flux is bigger, and separation is little, and the PVA molecules align is regular, the degree of crystallinity height, and permeation flux is little, separation is bigger, the infiltrating and vaporizing membrane that PVA and CS blend can obtain having better separating property.
3. PVA/CS blend film of the present invention has higher mechanical strength, and infiltration evaporation separation of methanol/DMC azeotropic mixture has bigger infiltration evaporation segregation index (PSI value).
4. the present invention obtains disposable separative efficiency height with embrane method infiltration evaporation separation of methanol/DMC azeotropic mixture, and permeation flux is big, compares with traditional distillation and separation method, and energy consumption is low, and process is simple, and is pollution-free.
Below in conjunction with embodiment in detail the present invention is described in detail.
Embodiment 1
Accurately take by weighing 5g PVA (alcoholysis degree: 99.8%-100%), under 90 ℃, be dissolved in the deionized water of 95g, evenly stir 4h, treat that PVA dissolves fully after, filtering solution to remove some undissolved impurity, is placed standby.The CS (low-molecular-weight, deacetylation 75%-85%) of 1.5g is dissolved under 25 ℃ in 2% the aqueous acetic acid, evenly stirs, be made into the CS solution of 1wt%, filter, to remove some undissolved impurity.Take by weighing the PVA solution of 3.2g5wt% and the CS solution of 8g1wt% respectively, mix at normal temperatures, evenly stir 3h, treat that solution evenly after the clarification, carries out vacuumizing and defoaming 2h, then this casting solution is poured on the clean glass plate (glass plate is wanted level), glass sheet temperatures remains on 40 ℃, carries out solvent evaporates 12h, and film is taken off from glass plate, put into 120 ℃ vacuum drying oven heat treatment 4h, obtain PVA: CS=2: 1 blend film.
This film carries out infiltration evaporation separation of methanol/DMC azeotropic mixture (methyl alcohol 70wt%, DMC30wt%), feed side keeps normal pressure, per-meate side vacuumizes, downstream pressure＜2kPa, the material liquid temperature is 25 ℃, seepage remaining liquid returns in the head tank, infiltration 2h reaches stable state to be tested, and the permeation flux that obtains this film is 87.6g/ (m
2H), separation 3.9, infiltration evaporation segregation index (PSI value) 254g/ (m
2H).
Embodiment 2
Take by weighing the PVA solution of 2.4g5wt% and the CS solution of 12g1wt% respectively, mix at normal temperatures, evenly stir 2h, treat that solution evenly after the clarification, carries out vacuumizing and defoaming 4h, then this casting solution is poured on the clean glass plate (glass plate is wanted level), glass sheet temperatures remains on 40 ℃, carries out solvent evaporates 14h, and film is taken off from glass plate, put into 140 ℃ vacuum drying oven heat treatment 2h, obtain PVA: CS=1: 1 blend film.
This film carries out infiltration evaporation separation of methanol/DMC azeotropic mixture (methyl alcohol 70wt%, DMC30wt%), feed side keeps normal pressure, per-meate side vacuumizes, downstream pressure＜2kPa, the material liquid temperature is 25 ℃, seepage remaining liquid returns in the head tank, infiltration 2h reaches stable state to be tested, and the permeation flux that obtains this film is 104.7g/ (m
2H), separation 4.1, infiltration evaporation segregation index (PSI value) 324.6g/ (m
2H).
Embodiment 3
Take by weighing the CS solution of 16g1wt% and the PVA solution of 1.6g5wt% respectively, mix at normal temperatures, evenly stir 2h, treat that solution evenly after the clarification, carries out vacuumizing and defoaming 2h, then this casting solution is poured on the clean glass plate (glass plate is wanted level), glass sheet temperatures remains on 40 ℃, carries out solvent evaporates 12h, and film is taken off from glass plate, put into 120 ℃ vacuum drying oven heat treatment 2h, obtain PVA: CS=1: 2 blend film.
This film carries out infiltration evaporation separation of methanol/DMC azeotropic mixture (methyl alcohol 70wt%, DMC30wt%), feed side keeps normal pressure, per-meate side vacuumizes, downstream pressure＜2kPa, the material liquid temperature is 25 ℃, seepage remaining liquid returns in the head tank, infiltration 2h reaches stable state to be tested, and the permeation flux that obtains this film is 165.2g/ (m
2H), separation 5.0, infiltration evaporation segregation index (PSI value) 660.8g/ (m
2H).
Comparative example
Table 1 be in the embodiment of the invention 3 in PVA/CS blend film and the bibliographical information (Joumal ofMembrane Science, 2002,209,493-508) film properties of CS homogeneous membrane infiltration evaporation separation of methanol/DMC azeotropic mixture compares.From list data as can be seen, PVA/CS blend film separation of the present invention is slightly less than the CS homogeneous membrane, but permeation flux is greater than the CS homogeneous membrane, and blend film infiltration evaporation segregation index PSI value is greater than the PSI value of CS homogeneous membrane, this shows that this blend film separation of methanol/DMC system is better than the CS homogeneous membrane, and has separating property preferably.
Table 1 PVA/CS blend film of the present invention and CS homogeneous membrane are relatively
*
| Film type | Permeation flux (gm -2·h -1) | Separation α | Infiltration evaporation segregation index PSI (gm -2·h -1) |
| The CS homogeneous membrane | 79.5 | 8.1 | 564.4 |
| Embodiment 3 | 165.2 | 5 | 660.8 |
*Material liquid is formed: methyl alcohol 70wt%, DMC30wt%; Operating temperature: 25 ℃
Claims (5)
1, a kind of polyvinyl alcohol/chitosan blend membrane preparation method that is used for separation of methanol/dimethyl carbonate, its step is as follows:
A) preparation of casting solution: make the dissolution with solvents polyvinyl alcohol at 80～100 ℃ with deionized water, being prepared into concentration is the polyvinyl alcohol casting solution of 5wt%; Make the dissolution with solvents shitosan at 20～40 ℃ with glacial acetic acid and deionized water, being prepared into concentration is the shitosan casting solution of 1wt%, and wherein the concentration of glacial acetic acid in the shitosan casting solution is 2wt%;
B) press mass ratio 2: 1-1: 2 with polyvinyl alcohol casting solution and shitosan casting solution mix, deaeration;
C) on glass plate, make film with casting method;
D) film is heat-treated under 120～150 ℃.
According to the described preparation method of claim 1, it is characterized in that 2, the alcoholysis degree of polyvinyl alcohol is 99.8%-100% in step a; Shitosan low-molecular-weight, deacetylation are 75%-85%.
According to the described preparation method of claim 1, it is characterized in that 3, casting solution mixes and stirs 3～4h, vacuum defoamation 2h among the step b.
According to the described preparation method of claim 1, it is characterized in that 4, the temperature of the glass plate among the step c is 40 ℃, solvent evaporates 12～16h.
According to the described preparation method of claim 1, it is characterized in that 5, heat treatment is carried out in vacuum drying oven in the steps d, heat treatment time is 2～4h.
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| CN101362694A (en) * | 2007-08-03 | 2009-02-11 | 中国科学院成都有机化学有限公司 | Method for separating methanol and dimethyl carbonate azeotropic mixture |
| CN101798403A (en) * | 2010-03-30 | 2010-08-11 | 东华大学 | Method for preparing chitosan/polyving alcohol/polylactic acid blended dense membrane |
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| JPH02135134A (en) * | 1988-11-16 | 1990-05-24 | Katokichi:Kk | Membrane for separating water-alcohol mixed liquid |
| US4960519A (en) * | 1989-10-16 | 1990-10-02 | Texaco Inc. | Membrane process for separation of organic liquids |
| CN1093944A (en) * | 1994-03-22 | 1994-10-26 | 浙江大学 | The preparation method of vapor permeable membrance and composition |
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| CN101824160A (en) * | 2010-03-30 | 2010-09-08 | 东华大学 | Preparation method of chitosan/polyvinyl alcohol/polylactic acid blended porous membrane |
| CN102125811A (en) * | 2011-01-10 | 2011-07-20 | 杭州水处理技术研究开发中心有限公司 | Method for preparing polyvinyl alcohol-chitosan nano filtration membrane |
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| CN105727761A (en) * | 2016-03-10 | 2016-07-06 | 上海工程技术大学 | Protein-fouling-resistant zwitter-ion ultrafiltration membrane and preparation method thereof |
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