JPS6031803A - Separation of liquid mixture - Google Patents

Abstract

PURPOSE:To separate a liquid mixture containing at least an org. liquid as the constitutional component thereof by pervaporization using a chitosan membrane. CONSTITUTION:As chitosan, one with a deacetylation degree of 50% or more is pref. When a chitosan membrane is used by adhering the same on a porous membrane (a microporous membrane), it sufficiently withstands use even if the thickness of said chitosan membrane is made thin. ''A liquid mixture'' being a liquid to be separated is selected from an azeotropic liquid mixture and an approximate b.p. liquid mixture. In performing pervaporization, the pressure difference between a liquid supply side and a liquid permeating side becomes effective as it grows larger but, in industrially performing pervaporization, pressure difference of 0.5-1atm. is pref. provided.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for separating at least one of its constituent torsion liquid mixtures by pervaporation.

The mixed liquid is placed on one side of the separation membrane, and the other side is evacuated to reduce the pressure, or an inert gas is flowed to keep the vapor pressure low, allowing the liquid to permeate and evaporate on the low pressure side. Therefore, the so-called pervaporation method to separate the mixed liquid is 1.
Research was conducted around the middle of 950. This separation method was devised for the purpose of separating and purifying chemical liquids (mainly organic solvents, hydrocarbons, etc.) that cannot be separated using normal distillation methods. It is said to be suitable for fractional separation of solvents, isomers (ortho and para, cis and trans), etc.

Other applications include RA condensation purification of mixed liquids and fruit juices containing thermally decomposable components, removal of trace impurities, and even removal of water produced during esterification reactions.

Many experimental examples have been reported in the past in which organic mixed liquids, especially water-alcohol mixed liquids, were separated by such pervaporation methods. For example, U.S. Patent No. 2,95
No. 3,502 uses a cellulose acetate membrane to
Experimental example of separating methanol mixed liquid (separation coefficient 5.1
, permeation rate 3-I K910Ill-hr), page 33 of the December issue of Functional Materials (1981) describes an experimental example in which a water-ethanol mixed liquid was separated using a cellulose acetate membrane (separation coefficient 8.5, permeation rate 1). .95KP/&-
hr) and an experimental example in which a mixed liquid of water and isopropanol was separated using a cellophane membrane (separation coefficient 15.6, permeation rate 0.7 Kp/nr-hr), Journal of
Applied Polymer Sci@noe v
ol 262- (1981), page 3,223, there is an experimental example in which a mixed liquid of water and methanol was separated using a g-shifted polyvinyl alcohol membrane (separation coefficient 22.6, permeation amount [0.2K
f/rl-hr) etc. have been reported. However, methods for separating water-alcohol mixed liquids using these membranes cannot be implemented on an actual soap cell scale, and have the following problems when implemented on an industrial scale, and are far from being practical. That is, (1) the separation rate when a water-alcohol mixed liquid passes once through a polymer membrane [generally, the weight ratio of the water component to the alcohol component after passing through the membrane is the weight ratio of the water component to the alcohol component before passing through the membrane] The value divided by the ratio is displayed as the separation coefficient α. That is, (in the formula W
and A indicate the weight of the water component and alcohol component, respectively. )] is small, so it must be passed through a large number of membranes in order to separate or concentrate it to the desired concentration.

(2) Amount of permeation through a polymer membrane [Generally, the amount of permeation per unit membrane 3-one area and unit time, that is, Q(KP/
rIf - hr)] is small, so it is necessary to increase the membrane surface area.

There are other problems.

The present inventors solved the problems of the conventional pervaporation method, and in order to provide a method for pervaporating organic mixed liquids with a high separation coefficient and high permeation rate, we developed a method using various membrane materials. During the experiment, we discovered that, surprisingly, a chitosan-based membrane, which had not been previously used as a separation membrane for pervaporation, actually had a higher separation coefficient and higher permeation rate than previously reported experimental values. The present invention has been developed based on the discovery that this can be achieved. That is, the present invention is a method for separating a liquid mixture, characterized in that a liquid mixture containing at least one quarter of its composition is an organic liquid is separated by pervaporation using a chitosan-based membrane.

The chitosan used in the present invention is produced by heating chitin, which is a component of the outer skin of crustaceans such as shrimp and crabs, to a temperature of 60°C or higher with an alkaline solution in the concentration range of 30 to 504-1, such as an aqueous sodium hydroxide solution. It is a substance obtained by deacetylating D-glucosamine, and its chemical structure is a β-(1→4) bond polysaccharide with D-glucosamine as the basic unit.
It forms a salt and easily dissolves in dilute aqueous solutions such as acetic acid, hydrochloric acid, phosphoric acid, etc., but when it comes into contact with an alkaline aqueous solution, it has the property of solidifying and precipitating again. Note that chitosan is a general term for deacetylated products obtained by treating chitin with a concentrated alkali, and the chitosan used in the present invention preferably has a degree of deacetylation of 50 or more. Also, chitosan is polyvinyl alcohol (PVA)! : It is also possible to use it as a blend film. P used for blending
VA has a saponification degree of 80% or more.

Preferably, 98 inches or more is used. A chitosan-based membrane is a membrane containing at least one of the above-mentioned chitosan components, such as a blend membrane or a filler-added membrane.

Includes graft membranes, cross-linked membranes, etc. The structures of these chitosan membranes include homogeneous membranes, composite membranes, and asymmetric membranes.

The thickness of the separation membrane used in the method of the present invention is 1μ5-300μ, preferably 5-200μ. If the film thickness becomes too thin, the strength of the film will be insufficient, but the durability will also be insufficient. Furthermore, if the membrane is thicker than this, the amount of liquid mixture that permeates through the membrane will be small, making it impractical.

Furthermore, when a chitosan membrane is used by being attached to a porous membrane (such as a microporous membrane), the chitosan membrane can be used sufficiently even if the thickness of the chitosan membrane is reduced. In this case, the thickness of the chitosan membrane can be reduced to about 0.1μ.The shape of the 0-spinning separation membrane is usually used as a flat membrane (flat membrane).
Other examples include using a cylindrical or hollow fiber shape to increase the membrane surface area.

In the present invention, the "mixed liquid" which is the liquid to be separated may be an azeotropic mixed liquid, a close boiling point mixed liquid, or the like.

The method of the present invention is particularly effective in separating organic mixed liquids.

Among organic liquid mixtures, azeotropic liquid mixtures include water/alcohol such as water/ethanol, water/isopropanol, and methyl acetate/methyl alcohol.

Examples include ethyl acetate/ethyl alcohol, benzene/cyclohexane, methanol/acetone, benzene/6-methanol, benzene/ethanol, acetone/chloroform, and methanol/acetone. In addition, as a close boiling point temperature mixture, ethylbenzene/styrene,
parachloroethylbenzene/halachlorstyrene, toluene/methylcyclohexane, butadiene/butenes,
Examples include butadiene/butanes. In addition to the above-mentioned mixed liquids, mixed liquids such as water/acetone, water/ethylene glycol, water/glycerin, water/methanol, etc., which can be separated by ordinary distillation, are also included.

The pervaporation device used in the present invention is not particularly limited; any conventionally known device can be used, and such a device can be operated under conventional conditions to separate the organic mixed liquid. When performing pervaporation, the larger the pressure difference between the feed liquid side and the permeate side, the more effective it is, but for industrial implementation, a pressure difference of 0.5 to 1 atmosphere is required. It is preferable that The pressure on the feed liquid side is preferably at or near atmospheric pressure, and the pressure on the permeate side is preferably maintained at a reduced pressure below the vapor pressure of the permeate component. As a method of keeping the permeate side at reduced pressure, there are methods such as drawing a vacuum to reduce the pressure, or keeping the vapor pressure low by flowing a gas that does not react with the liquid. The separation temperature is generally 40° C. or higher and lower than the azeotropic temperature of the organic liquid mixture to be separated, but is not particularly limited. When separating a liquid mixture, if the desired concentration cannot be obtained by passing it through a chitosan membrane once, the desired concentration can be achieved by installing a similar device in succession and passing it through multiple times, or by combining it with distillation. It is possible to separate up to a membrane.

The method of the present invention achieves higher separation coefficients and higher permeation rates than conventional membrane separation methods. Therefore, according to the method of the present invention, the separation system can be made more compact, the processing capacity can be increased, and the cost can be reduced. It is effective in many industries and has extremely great industrial utility.

Next, the method of the present invention will be explained in more detail based on the practical examples.8- I will clarify.

Examples 1 to 5 A chitosan membrane was set in a pervaporation device on the J side et23.5-, an ethanol-water mixture was supplied to the mixed liquid chamber, and the exhaust chamber was heated to a vacuum pump at a certain temperature. Then, the pressure was reduced to 3 x 2, and the number of oils was added. The permeation amount Q1 per unit area and unit time and the separation coefficient of water (I20) to ethanol (gton), The nonagonal medium-shaped chitin obtained from the above was deacetylated by heating at 110° C. for 1 hour in an approximately 50% aqueous sodium hydroxide solution while blowing nitrogen gas, and the reactant was taken out and thoroughly washed with water. The same operation was repeated three times for this reaction product, and the obtained chitosan was dissolved in an aqueous dithiacetic acid solution to prepare an approximately 2% chitosan solution. This solution was oxidized with a large amount of IN hydroxide)
Pour into IJum aqueous solution and solidify into a string. When this string-shaped chitosan is treated again under the same conditions as before, chitosan with a degree of deacetylation of 99- is obtained. Chitosan of Example 4 was obtained by processing under the same conditions as Example 1.2.8, except that the heating temperature was 60° C. and the heating time was 2 hours. The chitosan used in Example 5 was obtained by reacting twice in the initial stage of Example 4.

Chitosan film formation was performed as follows. Chitosan 0.5
After immersing the sample in 35~'IO*g of distilled water for about 30 minutes, 0.75114 g of glacial acetic acid was added and dissolved with stirring. Next, after suction-filtering this solution, a glass plate (mirror finish, 20 x 20 t
yn') and air-dried at room temperature.

The obtained membrane was immersed in an aqueous solution of IN sodium hydroxide,
After insolubilization, the sample was thoroughly washed with distilled water.

Example 6 First, a chitosan aqueous solution and a chitosan aqueous solution containing seed acetic acid are prepared. The weight ratio of chitosan and PVA is 60.
The mixture was mixed at a ratio of 40 to 40, and after being filmed on a glass plate, it was heat-treated at 120° C. for 1 hour in the same way as the chitosan film. The obtained heat-treated membrane was immersed in an IN aqueous solution of sodium hydroxide to insolubilize the chitosan component, and then thoroughly washed with distilled water to prepare a sample.

The obtained chitosan-PVA blend membrane was set in the same apparatus as in Examples 1 to 5, and the membrane performance was measured at a stock solution ethanol concentration of 75.4% by weight, a temperature of 17.0°C, and a pressure of 3 HP. Q= 0.145kq/m”hr.

H,0 α1EtOH” was 37.8.

Example 7 A chitosan membrane with a degree of deacetylation of 99% was set in the same apparatus as in Examples 1 to 5, and a stock solution of toluene/methanol (501
50wt/wt), temperature 70”C, pressure 0, 5w
When membrane performance was measured with Hf, Q=o, o95 Patent applicant Director of the Agency of Industrial Science and Technology (and one other person) Designated agent Director of the Osaka Institute of Industrial Science and Technology, Agency of Industrial Science and Technology 13- Continued from page 1 0 Inventor Akira Mochizuki Kurashiki Ichisakazu @ Inventor
1) Yoshiki Naka 625 Misu, Soja City 1433-25 1

Claims (1)

[Claims] 1. A method for separating a liquid mixture, which comprises separating a liquid mixture containing at least an organic liquid as one of its components by pervaporation using a chitosan membrane.