JPH0367731B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field] The present invention relates to a method for separating liquid mixtures.
More specifically, in a method for separating a liquid mixture consisting of at least two components, a membrane composed of a polymer having a glycosidic skeleton as a main chain having a cationic group forming a salt with a counter anion is used. This invention relates to a method for separating liquid mixtures by vapor permeation. [Prior Art] Liquid separation methods using membranes have been in the spotlight in recent years, and many research examples have been reported. For example, regarding the pervaporation method, there is an experimental example in which an azeotropic liquid mixture was separated using a cellulose acetate membrane or a polyvinyl alcohol membrane in U.S. Patent No. 2953502, J. Polymer SCI,
Symposium No. 41, 145-153 (1973) Experimental example of separating water-methanol mixed liquid in the presence of sodium formate using a cellophane membrane, Journal of
Applied Polymer Science vol, 26 (1981)
On page 3223, there is an experimental example in which a water-methanol mixed liquid was separated using a grafted polyvinyl alcohol membrane, and synthetic polymers with ionic groups introduced in Japanese Patent Publications No. 54-10548, No. 54-10549, and No. 59-49041. Experimental examples have been reported in which water-organic liquid mixtures were separated using molecular membranes. In addition, as a vapor permeation method, for example, U.S. Patent No.
No. 4405409 describes a method of selectively permeating water vapor using a cellulose acetate membrane. [Problems to be solved by the invention] The pervaporation method is used to separate azeotropic mixtures and isomers with close boiling points (ortho and para isomers, cis and trans isomers, etc.) that are difficult to separate using conventional simple methods. However, in the conventional pervaporation method, the separation membrane has the following problems and has not been put into practical use. That is,
Separation rate when a mixed liquid passes through a polymer membrane once [Generally, the separation coefficient is the value obtained by dividing the weight ratio of component A to component B after passing through the membrane by the weight ratio of component A to component B before passing through the membrane. Display as α. That is, α ^A _B = (W _A /W _B ) in permeate/( in permeate liquid)
W _A /W _B ) (in the formula, W _A and W _B indicate the weight of component A and component B, respectively)] is small, so it takes a very large number of membranes to separate or concentrate to the desired concentration. The advantages of membrane separation methods cannot be fully exploited because the membrane separation method has to be allowed to pass through the polymer membrane. ² hr) reaches a practically high value, the separation coefficient α becomes extremely low. On the other hand, the vapor permeation separation method has the same advantages as the above-mentioned pervaporation separation method, but a membrane with sufficient separation performance has not yet been found and it has not yet been put into practical use. Therefore, an object of the present invention is to provide an industrially advantageous method for separating liquid mixtures. [Means for Solving the Problem] In order to achieve the above object, the present inventors have made extensive studies and have constructed a main chain consisting of a glycosidic skeleton having a cationic group that forms a salt with a counter anion. The inventors have discovered that separation of liquid mixtures by vapor permeation using a membrane made of a polymer having 200% is very industrially advantageous, and have arrived at the present invention. That is, the present invention provides a method for separating a liquid mixture consisting of at least two components, in which a polymer composed of a polymer having a glycosidic skeleton as a main chain and having a cationic group forming a salt with a counter anion is used. This is a method for separating a liquid mixture, which uses a membrane and performs separation by vapor permeation. In the membrane composed of a polymer having a glycosidic skeleton having a cationic group as its main chain, which is used in the method of the present invention, the cationic group includes all cationic groups that can form salts. is preferably an ammonium group or a metal complex group having a nitrogen atom coordinated to a polyvalent metal ion. As an ammonium group, the general formula −N ⁺ HnR ₄
-n (wherein R is a hydrocarbon group having 1 to 6 carbon atoms,
ion represented by (n is an integer from 1 to 4), -
NHCH ₂ CH ₂ NH ₂ , −
_{Polyamines such as NHCH2CH2NHCH2CH2NH2 ,}

【formula】

Examples include ammonium groups made from amines having a heterocyclic structure such as [Formula]. In addition, a group having a nitrogen atom coordinated to a polyvalent metal ion is a metal complex group formed when a nitrogen atom on a polysaccharide molecule coordinates to a polyvalent metal ion, and has the general formula

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples. Examples 1 to 6 Chitosan membrane with a degree of deacetylation of 98 mol% (thickness
22 μm) to the amino group of chitosan, 0.1 to 1.8
An ionized chitosan salt film was obtained by immersing it in a mixed solution of ethanol/water (50/50 weight ratio) containing twice the equivalent amount of acid at room temperature for 13 hours. The effective membrane area of the membrane is
It is attached to a 7.0 cm ² vapor permeation device, and the vapor of the liquid mixture shown in Table 1 is supplied to the membrane surface at normal pressure.
Vapor permeation separation was performed with the next side set to 0.3 mmHg.
Separation coefficient α ^H2O and permeation rate Q (g/m ² h) are shown in Table 1.

[Table] Example 7 Chitosan with a degree of deacetylation of 98 mol% was dissolved in a 1 wt% acetic acid solution so that the polymer concentration was 1 wt%, and the polymer solution was cast onto a glass plate and air-dried. Chitosan-acetate film (thickness
22 μm) was obtained. Using this membrane, ethanol/water mixed vapor (90/10 weight ratio) was separated in the same manner as in Example 1. The separation coefficient α ^H2O and permeation rate were 89.2 and 100.5 g/m ² h, respectively. Examples 8 and 9 Chitosan membrane with a degree of deacetylation of 98 mol% (thickness
22μm) in an ethanol/water mixture containing four times the amount of metal ions relative to the amino groups of chitosan.
A metal complex film was obtained by immersion at 60°C for 13 hours. Using this membrane, ethanol/water mixed vapor (90/10 weight ratio)
separation was carried out. Separation coefficient α ^H2O , permeation rate Q
(g/m ² h) is shown in Table 2.

〔Effect of the invention〕

According to the method of the present invention, it is possible to industrially advantageously separate a liquid mixture at a high permeation rate while maintaining a high separation coefficient. Therefore, the separation system can be made more compact, the processing capacity can be increased, and the cost can be reduced.The present invention is effective in shortening the separation and purification process in the chemical industry, etc., and in practical application of membrane separation methods to save energy. The above-mentioned usefulness is extremely large.

Claims (1)

[Claims] 1. In a method for separating a liquid mixture consisting of at least two components, a polymer comprising a polymer having a glycosidic skeleton as a main chain and having a cationic group forming a salt with a counter anion. A method for separating a liquid mixture, which uses a membrane and is characterized by separation by vapor permeation. 2. The method for separating a liquid mixture according to claim 1, wherein the cationic group is an ammonium group or/and a group having a nitrogen atom coordinated to a polyvalent metal ion. 3. The method for separating a liquid mixture according to claim 1 or 2, wherein the polymer is a chitosan salt or a chitosan derivative salt. 4. The method for separating a liquid mixture according to claim 1 or 2, wherein the polymer is a cationic cellulose derivative salt.