A kind of preparation method of osmotic, evaporating and dewatering membrane
The present invention relates to the synthetic and application in infiltration evaporation separates of molecular screen membrane, particularly provide a kind of high-temperature stability that has that is applied to infiltration evaporation, the novel infiltrating and vaporizing membrane of chemical stability and high mechanical strength.
Infiltration evaporation is a kind of membrane separation technique that recent two decades develops rapidly, it utilizes the absorption on a film with separation performance of each component in binary or the multi-component liquid mixture (or dissolving, or screening) and the difference of diffusion to come the separating liquid mixture.Because the infiltration evaporation sepn process is not subjected to the restriction of vapor-liquid equilibrium, thereby in the reluctant azeotrope separation of traditional separation means, removing of minor amount of water, underwater micro-organic matter remove or concentrate and aspects such as organism/separating organic matters demonstrate unique advantages, be subjected to people's extensive concern.Yet existing infiltrating and vaporizing membrane mostly is organic membrane, is existing unsurmountable defective aspect thermostability, mechanical stability and the chemical stability.
Molecular sieve is a kind of inorganic crystalline microporous material, and it has good thermostability and chemical stability.Molecular sieve is owing to the ion characteristic of its crystal internal surface has the coulomb field effect.Along with the variation of molecular screen material silica alumina ratio, the coulomb field effect also changes thereupon, thereby causes the difference of the hydrophilic and hydrophobic matter of molecular screen material.The molecular sieve of high silica alumina ratio or total silicon molecular sieve, as high silicon MFI molecular sieve and Silicalite-1 molecular sieve, very little or do not have an electrostatic field because of the electrostatic field of its crystals, so have strong hydrophobicity, the film that is made of it can extract the organism of high density from the organism/aqueous solution of lower concentration by infiltration evaporation.And the molecular sieve of low silica-alumina ratio as A type molecular sieve, then has strong hydrophilicity, can from the organism of high density water be deviate from by infiltration evaporation by the film that it constitutes, thereby prepare anhydrous organism.The molecule that varies in size in addition also can obtain selecting shape by infiltration evaporation on molecular screen membrane separates.In view of above advantage, in recent years, people to molecular screen membrane the application in infiltration evaporation carried out widely exploring, obtained challenging result, the saturating amount and the selectivity that show as the A type molecular sieve film all are better than organic polymer films.This film has only been used time of 2-3 from the appearance of researching and developing commercially produced product, has shown extremely strong application background.
The object of the present invention is to provide a kind of synthetic method of novel osmotic, evaporating and dewatering membrane-NaA type molecular screen membrane, good with the separation performance of this method synthetic molecular screen membrane, and synthetic simple.
The invention provides a kind of preparation method of novel osmotic, evaporating and dewatering membrane-NaA type molecular screen membrane, it is characterized in that from uniform settled solution, utilize original position hydro-thermal synthetic method once to synthesize NaA type molecular screen membrane on the porous basement membrane of precoating crystal seed, the aperture of basement membrane is 0.05-100 μ m; The prescription of the settled solution of synthesizing molecular sieve film is: aNa
2O: bAl
2O
3: 5SiO
2: cH
2O, a=(20-100) wherein, b=(0.5-5), c=(500-4000); Hydro-thermal synthetic temperature is 50-100 ℃, and the time is 1-100 hour.
Among the preparation method provided by the invention, the settled solution prescription is with a=(20-50), b=(1-3), and c=(800-2000) is good.
The basement membrane of synthesizing molecular sieve film provided by the invention both can be porous oxide film, also can be porous metal film, and the aperture of basement membrane is 0.05-100 μ m, was good with 0.1-10 μ m wherein; The shape of basement membrane can be sheet or tubulose.
The crystal seed of synthesizing molecular sieve film provided by the invention adopts the method for microwave heating synthetic, and its homogeneous grain size is about 1 μ m.
The preparation method of molecular screen membrane provided by the invention is characterized in that having synthesized molecular screen membrane by original position hydro-thermal synthetic method on the porous basement membrane, rather than by indirect means dip-coatings such as sol-gels.The molecular screen membrane that provides utilizes X-ray diffraction characterization methods such as (XRD) to be indicated as NaA type molecular screen membrane, and gas permeation test shows that the integrity of NaA type molecular screen membrane is better.
Synthetic NaA type molecular screen membrane of the present invention is applied to infiltration evaporation to be separated, in temperature is 75 ℃, the vacuum tightness of per-meate side is under the condition of 200-400Pa, and the ideal separation factor of the alcohol/water of synthetic NaA type molecular screen membrane is 1000-10000, and saturating amount is 0.5-1.0kg/m
2.h.
The present invention has developed the novel infiltrating and vaporizing membrane a part sieve membrane of high score from performance, separates with the infiltration evaporation of organic membrane and compares, and molecular screen membrane not only stability is better, and separation performance also improves.Explain detailedly below by embodiment.
Accompanying drawing 1 is the synthetic synoptic diagram of molecular screen membrane.
Accompanying drawing 2 is the x-ray diffraction pattern of embodiment 1 synthesizing molecular sieve film.
Accompanying drawing 3 is the scanning electron microscope diagram of embodiment 1 synthesizing molecular sieve film.
Accompanying drawing 4 is the infiltration evaporation setting drawing.
The Pervaporation Separation of ethanol/water mixture on NaA type molecular screen membrane when accompanying drawing 5 is 60 ℃.
When accompanying drawing 6 is 60 ℃ in the ethanol/water mixture alcohol concn with the variation of dewatering time.
The infiltration evaporation performance of (n-propyl alcohol+propyl carbinol)/water mixture on NaA type molecular screen membrane when accompanying drawing 7 is 75 ℃.
When accompanying drawing 8 is 75C in (E propyl alcohol+propyl carbinol)/water mixture determining alcohol with the variation of dewatering time.
Embodiment 1: the preparation of tubulose NaA type molecular screen membrane
The synthetic used basement membrane of NaA type molecular screen membrane is α-Al
2O
3Basement membrane, its aperture 0.1-0.3 μ m, porosity is 50%.Basement membrane be shaped as tubulose, diameter is 30mm, thickness is 2mm.Basement membrane is before use with polishing flat ultrasonic washing in the distilled water, dry for standby then through fine sandpaper.Be used to synthesize behind the membrane surface precoating crystal seed after the oven dry.
The synthetic liquid of synthetic A type molecular sieve film is prepared as follows:
Solution (1): 74.1 gram NaOH are dissolved in 159 ml deionized water, add 1 gram metal aluminum foil then, and dissolving promptly gets solution (1);
Solution (2): with the water of 17.74 milliliters of silicon sol and 159 milliliters mix solution (2), wherein contain SiO in the silicon sol
2Be 27wt%.
Wait to join solution (1) and solution (2) afterwards, solution (1) is added in the solution (2) in stirring, mix until obtaining transparent colloidal sol.The prescription of the colloidal sol that finally obtains is 50Na
2O: Al
2O
3: 5SiO
2: 1000H
2O.
The effective support of the film that scribbles crystal seed is fixed, vertically be positioned over (as Fig. 1) in the stainless steel synthesis reactor.To synthesize liquid then changes among the synthesis reactor.Place the baking oven that is warming up to 90 ℃ in advance, take out behind the heating crystallization certain hour, be cooled to room temperature, distilled water wash is dried to neutral.Molecular screen membrane after the oven dry proves NaA type molecular screen membrane through X-ray diffraction (as Fig. 2); Scanning electronic microscope (as Fig. 3) shows that the thickness of film is about 10 μ m.
Molecular screen membrane after synthetic has been carried out the integrity sign with gas-permeable.Under the pressure reduction of 25 ℃ and 0.10MPa, the H that diaphragm shows
2/ n-C
4H
10Ideal separation factor be 15.8, greater than H
2/ n-C
4H
105.39 the ratio of exerting gloomy diffusion, show at α-Al
2O
3Membrane surface has formed the comparatively complete NaA type molecular screen membrane of one deck.Embodiment 2: the Pervaporation separation properties of ethanol of tubulose NaA type molecular screen membrane
The molecular screen membrane of embodiment 1 gained is carried out ethanol/water infiltration evaporation Separation Research, its flow process as shown in Figure 4,1. waters bath with thermostatic control, 2. raw material tanks, 3. magnetic force recycle pumps, 4. membrane separation apparatuss, 5. cold-traps, 6. T-valve, 7. buffer tubes, 8. vacuum pumps wherein.In the infiltration temperature is the vacuum tightnesss of 60 ℃ and per-meate side when being 200-400Pa, and the ethanol/water solution separating resulting as shown in Figure 5.As seen from the figure, NaA type molecular screen membrane has good infiltration evaporation performance to ethanol/water mixture, and as when 60 ℃ and stock liquid determining alcohol are 92wt%, the separation factor of ethanol/water mixture on NaA type molecular screen membrane is 1000.
In order further to investigate the dewatering of the molecular screen membrane of embodiment 1 gained to ethanol/water mixture, determining alcohol in the 800 gram 92wt% ethanol/water mixtures is studied with the variation of dewatering time, the result is as shown in Figure 6.As seen from the figure, the ethanol/water mixture of 800 gram 92wt% is 70cm at membrane area in the time of 60 ℃
2NaA type molecular screen membrane on through just break through the constant boiling point of ethanol/water less than 10 hours dehydration; After dehydration in 50 hours, the stock liquid alcohol concn can be concentrated into more than the 99wt%.Embodiment 3: the Pervaporation Separation of (n-propyl alcohol+propyl carbinol)/water of tubulose NaA type molecular screen membrane
The molecular screen membrane of embodiment 1 gained is carried out (n-propyl alcohol+propyl carbinol)/water infiltration evaporation Separation Research.In the infiltration temperature is the vacuum tightnesss of 75 ℃ and per-meate side when being 200-400Pa, and the separating resulting of (n-propyl alcohol+propyl carbinol)/water mixture as shown in Figure 7.Because n-propyl alcohol and propyl carbinol have littler polarity than ethanol, so in infiltration evaporation separates, shown more superior separation performance, as when 75 ℃ and stock liquid determining alcohol are 92wt%, the separation factor of (n-propyl alcohol+propyl carbinol)/water mixture on NaA type molecular screen membrane is 10000, greater than the separation factor of ethanol/water.
In order further to investigate the dewatering of the molecular screen membrane of embodiment 1 gained to (n-propyl alcohol+propyl carbinol)/water mixture, determining alcohol in 800 gram 92wt% (n-propyl alcohol+propyl carbinol)/water mixture is studied with the variation of dewatering time, and the result as shown in Figure 8.As seen from the figure, (n-propyl alcohol+propyl carbinol)/water mixture of 800 gram 92wt% is 70cm at membrane area in the time of 75 ℃
2NaA type molecular screen membrane on through reaching 96.8wt% less than the determining alcohol of stock liquid after 10 hours the dehydration; After 20 hours dehydration, the determining alcohol of stock liquid can be concentrated into more than the 99.0wt%.Temperature when dewatering owing to having raise, the dehydration of (n-propyl alcohol+propyl carbinol)/water mixture is faster than the dehydration of ethanol/water mixture.Comparative example one:
(1) world patent PCT/GB95/0221 adopts the prescription similar with us to synthesize the A type molecular sieve film scribbling on the porous metal basement membrane of crystal seed.The infiltration evaporation that their synthetic molecular screen membrane also is applied to organism/water separates.Before not doing synthetic aftertreatment, molecular screen membrane is 13.5 to the separation factor of water/aqueous isopropanol of 8.8wt%, and saturating amount is 3.2kg/m
2.hr.Compare with our synthetic molecular screen membrane, saturating amount is big 3 times than us, but separation factor is wanted little three orders of magnitude.They improve the separation performance of molecular screen membrane by the method that the molecular screen membrane after synthetic is modified.The separation performance of the molecular screen membrane after the modification is close with our synthetic molecular screen membrane.But from the synthetic process, the method for our synthesizing molecular sieve film is obviously than simply.Comparative example two: professor Budd of (2) Britain Manchester university adopts the prescription similar with us to synthesize the A type molecular sieve film on porous zirconia/Ni-Cr alloy network basement membrane.The synthesis condition that they adopt is 50 ℃, 48 hours.They are applied to alcohol/water infiltration evaporation with the synthetic molecular screen membrane and separate.The separation factor of isopropanol is 1000-10000, measures at 0.5kg/m thoroughly
2.hr (select from Microporous Materials, vol.12,1997, p305).The separation factor of (n-propyl alcohol+propyl carbinol)/water of our synthetic A type molecular sieve film is 10000, and saturating amount is 1.0kg/m
2.hr. separation performance is than improving.Comparative example three: professor Kita of (3) Japanese Yamaguchi university has synthesized the A type molecular sieve film from gelling system at the porous alumina basement membrane, and its prescription is: 2Na
2O: Al
2O
3: 2SiO
2: 160H
2O, synthesis temperature are 100 ℃, and generated time is 3 hours.They are applied to the synthetic molecular screen membrane among organism/water infiltration evaporation separation, and the 90wt% ethanol/water separates coefficient in the time of 75 ℃ be 10000, and saturating amount is 2.0kg/m
2.h. (select from a day disclosure laid-open patent JP 08,318,141).From separation performance, the separation factor of our synthetic film is suitable with them, and saturating amount is low than theirs.This may be different with the synthetic system relevant.But from the synthetic synthetic system that is adopted, the settled solution system that we adopt is even than the gelling system that they adopt, and also more has practical value.