JPS627405A - Osmotic evaporation separation method - Google Patents

Abstract

PURPOSE:To separate a liquid mixture at a high permeation speed while high separation factor is kept, by performing osmotic evaporation by using a dry membrane comprising a polymer having a glycoside type skeletal having an anionic group forming an alkali metal salt between pair cations in the main chain thereof. CONSTITUTION:For example, an aqueous sodium alginate solution is cast onto a glass plate and naturally dried to obtain an anionic polysaccharides type membrane having an alkali metal salt formed thereto. This membrane is mounted to an osmotic evaporation apparatus and the secondary side of the membrane is held to reduced pressure by a vacuum pump to dry the membrane until water content reaches 25wt% or less. This dry membrane is used to separate a water-org. liquid mixture such as a water/ethanol mixture or an org.-org. liquid mixture by osmotic evaporation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a pervaporative separation method for separating water-organic liquid mixtures or organic-organic liquid mixtures using membranes.

[Conventional technology]

Conventionally, a liquid mixture to be separated is supplied to the feed liquid side (-next side) of two chambers separated by a separation membrane.

The permeate side (secondary side) is maintained at a low vapor pressure by reducing the pressure or by flowing an inert gas, and is used as a permeation resource that allows components with high affinity with the membrane to preferentially permeate into the secondary side as vapor. A method of separating a water-organic liquid mixture by the permeation method has been carried out, and various experiments have been reported in which a water-organic liquid mixture was separated by the permeation method. For example, US Pat. No. 2.9s3. so, 1jJ- is an experimental example in which an azeotropic liquid mixture was separated using a cellulose acetate membrane or a polyvinyl alcohol membrane, J, Polyme
rS CI, Symposium 41,145-
153 (1973) used a cellophane membrane to
Experimental example of dividing methanol mixed liquid in the presence of sodium formate, Journal of Applied P
olymer 5science vol, 21i(]9
81) 3223 page shows an experimental example of separating water-methanol/l/mixed liquid using a grafted polyvinyl alcohol membrane, and Japanese Patent Publication No. 5.1-10548.54-10
No. 549 and Japanese Patent Publication No. 59-49041 report five examples in which a water-organic liquid mixture was separated using a synthetic polymer membrane into which ionic groups were introduced.

[Problem that the invention seeks to solve]

Unlike reverse osmosis, pervaporation is not limited in terms of concentration by osmotic pressure, so it is not limited to separating liquid mixtures with low concentrations, but can be used to separate liquids of all concentration ranges (for example, Ortho and Puff + Af!). It has characteristics such as being able to separate E-isomer, cyst-trans isomer).

However, the separation membranes used in conventional pervaporation methods have the following problems and are not practical. In other words, the ratio of separation due to K when the mixed liquid passes through the polymer membrane once [generally, 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 is expressed by the separation factor α. In other words, (in the formula, wA and wB indicate the weights of component A and component B, respectively)] are small, so in order to separate or concentrate to the desired concentration, it is necessary to pass through a very large number of membranes. In particular, the permeation rate through a polymer membrane [generally, the permeation rate per unit membrane surface area and unit time, that is, Q (kg
/gohr)] reaches a high value that is considered practical, the separation coefficient α becomes extremely low.

The above-mentioned membranes all have a separation coefficient of about several 1O, and the object of the present invention is to separate water-organic liquid mixtures or organic-containing liquid mixtures by pervaporation.

Means for Solving the Problem] In order to achieve the above object, the present inventors have made extensive studies and have unexpectedly discovered a method using a dry membrane composed of a polymer having an ionized glycoside skeleton in its entire main chain. We discovered that when pervaporative separation is carried out, mixed liquids can be processed at a high permeation rate while maintaining an extremely high separation coefficient.
This led to the present invention. That is, the present invention is composed of a polymer having an anionic group forming an alkali metal salt with a counter cation in the entire main chain of a glycosidic skeleton, and has a water content of 25% by weight or less. This is a pervaporative separation method characterized by pervaporatively separating a water-organic liquid mixture or an organic-organic liquid mixture using a membrane dried as described above. (referred to as saccharide-based dry film).

In the present invention, after forming the membrane into an alkali metal salt membrane and once drying the membrane before pervaporation, a water-organic liquid mixture or an organic-organic liquid mixture, preferably 1% or less by weight, 125% by weight or less, is used. Refers to 1 of 15 tray-shaped or smaller. There are no particular restrictions on the method of drying the membrane, but for example, the membrane may be left in dry air or vacuum dried. For convenience, attach a hypopolysaccharide-based membrane to the ion pervaporation device, and before starting heel pervaporation separation, dry the secondary side of the membrane by keeping it under reduced pressure, for example, 0.3 mmHg, for about 10 minutes using a vacuum pump. (4) It may be dehydrated by immersing it in an organic liquid having a water content of 0 to 20% by weight. Note that heating may be freely performed to the extent that the film does not denature. The moisture content of the membrane can be easily measured using a moisture meter.

In the anionic polysaccharide-based dry membrane used in the method of the present invention, the anionic group includes all anionic groups that can form salts, but among them, for practical purposes, sulfate ester) V residue, sulfone 8 acid groups, carboxyl acid residues, phosphoric acid esters/
V residues and honufonic acid residues are preferably used. 1. The anionic polysaccharide dry membrane used in the present invention is a membrane having one or more groups selected from the above ionic group. is a membrane dried, for example, by the method described above.

The ingredients of the anionic polysaccharide-based dry membrane used in the present invention (salts of natural polysaccharides such as leucine sulfate, hyalonic acid, xanthan gum, etc., and derivatives thereof, such as
F': W methyl esterified alginic acid, carbomethoxy,
(J-Semi-synthesis of 4.0M cellulose such as flower alginic acid, phosphorylated alginic acid, aminated 1!regic acid, cellulose sulfate, cellulose phosphate, sulfoethylcellulose, phosphoethylcellulose, phosphorylated guar gum, phosphorylated chitin, etc.) Examples include dry films made of polysaccharide salts, etc. Among them, in the present invention, dry films made of alginates, alginic acid conductor salts, and cellulose derivative salts are preferred in terms of film formability, mechanical strength, and film performance. This is the membrane used.

The anionic polysaccharide-based dry membrane used in the present invention is a dried film containing the above-mentioned anionic polysaccharide-based polymer as a main component, but is blended with a polymer that is compatible with the anionic polysaccharide. For example, membranes obtained by drying a blend membrane with PVA, pullulan, a neutral polysaccharide such as starch, etc., and a graft membrane grafted with a hydrophilic vinyl monomer such as acrylic acid are also included.

When the anionic polysaccharide-based dry membrane used in the present invention contains citric acid residues, etc., counter cations for the layer include ions of alkali metals such as lithium, sodium, potassium, chloride, vidium, and cesium. , %L12 is effective and preferred in the invention. In addition, in the present invention, when the same polymer has a cation and an anion and is ionized within and/or between molecules, or when the counter ion is a polyion (for example, alginic acid and polyethyleneimine, L7) It also includes ionic complexes such as vginic acid and chitosan).

In order to more specifically explain the anionic polysaccharide dry membrane used in the present invention, we will use an alginate polysaccharide membrane and a cellulose derivative membrane as examples of the anionic polysaccharide dry membranes. etc. will be described in detail, but the present invention is not limited in any way by this specific example.

First, an alginate polysaccharide membrane, which is an example of an anionic polysaccharide dry membrane, will be described. Alginic acid is a sticky polyester extracted from brown algae such as kelp, β-(
1→4) MM block in which only M-linked D-mannuronic acid j (M) is arranged, α-(1→4)-linked L-guluronic acid (GG Brotznig in which only Gl is arranged, and M and G are arranged alternately) It is a block copolymer consisting of three types of arranged MG blocks.

Such alginic acid forms a salt with an alkali such as sodium hydroxide or potassium hydroxide and dissolves in water at a constant volume. Therefore, a solution of this alginate can be cast onto a glass plate or the like and allowed to dry naturally. This creates a transparent homogeneous alginate film. Alternatively, the alginate solution may be mixed with a water-soluble organic solvent (e.g., ether, isopropanol/L/
% acetone, etc.) or a 1-thick salt solution, the salt has the property of coagulating and precipitating, so it can also be used to make a wet coagulated film. Alginic oxygen polysaccharide refers to alginic acid and its derivatives. Before pervaporation using such an alginate oxygen polysaccharide membrane, it is dried to a moisture content of 25% by weight or less, for example, according to the method described above. When ionizing the membrane, multiple types of counter cations may be used at the same time; the ion source may be a salt or hydroxide for metal ions, or a salt or amine for ammonium ions. used. Methods for preparing an anionic alginate polysaccharide membrane having these cations as cations include immersing the alginate polysaccharide membrane or alginate polysaccharide salt membrane in a solution containing the cations and performing ion exchange, or There is a method in which ions are exchanged sequentially by pervaporation treatment with a mixed liquid containing cations.

Since each car has a suitable content, it is selected appropriately depending on the yarn. For example, if the liquid mixture to be separated is a water-ethanol mixture:
It is desirable to use an ionized membrane with a cation content of 2 mol % or more (based on the carboxyl group of the al-5ty acid).

Anionic polysaccharide dry membranes, including the alginic acid polysaccharide dry membrane, are hydrophilic, so when the liquid mixture to be separated is a water-organic liquid mixture.

Membrane performance is greatly affected by water concentration. The concentration of the organic liquid at which the anionic polysaccharide-based dry membrane exhibits high performance depends on the type of membrane, the type of ion, the type of organic liquid, etc.
Since each has its own suitable concentration range, it is selected appropriately depending on each yarn. For example, when a water-ethanol mixture is separated using a dry membrane made of sodium alginate, the ethanol concentration is preferably 70% by weight or more, preferably 85% by weight or more.

In order to improve the water resistance and mechanical strength of the anion-injected polysaccharide film, it is desirable to further crosslink it. ), a method of forming an acetal bond with the molecule jltq11 using an aldehyde, etc., etc. The ionization method, crosslinking method, etc. described above can also be applied to other anionic polysaccharides.

] 'Whether or not metal ions are coordinated in the film can be determined quantitatively using atomic spectroscopy, but the
The formation of an alginic acid-metal salt film can be confirmed from the fact that it is colored in this color.

Further, carboxymethylcellulose, which is a cellulose derivative salt, can be easily obtained by reacting chloroacetic acid with cellulose under alkaline conditions, and cellulose sulfate can be easily obtained by reacting a chlorosulfonic acid-pyridine mixture To7-Rhone. can. The anionic cellulose derivative thus obtained can be ionized in the same manner as the ionization of the alginic acid polysaccharide described above. Further, similar crosslinking methods and drying methods can be used.

The thickness of the separation membrane used in the method of the present invention is 1μ to 300μ
μ, preferably 5 to 2”00 μ. If the film thickness is thinner than this, the strength of the film will be insufficient or the durability will be insufficient. Also, if the film thickness is thicker than this, the film will not pass through the film. Even if the permeation amount of the liquid mixture is reduced, it can be used sufficiently.In this case, the thickness of the ionized polysaccharide membrane is 0.
It can be thinned down to about one house. The above-mentioned shape of the 1 m membrane is used as a flat membrane (flat membrane), but it can also be used in other shapes such as a cylindrical shape or a hollow fiber shape to increase the membrane surface area.

Water/organic liquid mixtures that can be separated by the pervaporation separation method of the present invention include water/methanol-7y, water/
Ethanol, water/n-propano-/I/, water/isopropanol, water/n-butanol, water/isobutanol,
Water/n-amyl alcohol.

Water/n-hexanol, water/2-ethylhegisanol
, water/n-octatool, water/enalene glycol, water/1,3-globandiol, water/1,4-butanol, water/1,2-propylene glycol, water/glycerin, etc. - Alcohol mixture; water/tetrahydrofuran, water/dioxane, water/methyl ethyl ketone, water/acetone, water/N,N-dimethylacetamide,
Examples include water/N, N-dimethylformamide. Examples of organic-organic liquid mixtures include methyl acetate/I/methyl alcohol, ethyl acetate/ethyl alcohol, benzene/cyclohexane, methanol/acetone, benatone/chloroform, and methanol/acetone.

Examples include ethylbenzene/styrene, parachloroμ ethylberene/parachlorostyrene, toluene/methylcyclohexane, and the like.

Particularly, the pervaporative separation method of the present invention uses a water-organic liquid mixture;
In the case of organic-organic liquid mixtures, it is particularly effective in separating mixtures containing polar organic liquids (eg alcohols, ketones, etc.).

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, it is preferable to provide a pressure difference of 0.5 to 1 atmosphere. be. 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. The method of keeping the permeate side at reduced pressure is to draw a vacuum to reduce the pressure, or use configuration 4.
There are methods such as keeping the vapor pressure low by flowing a gas that does not react with the water. 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 an ionized polysaccharide membrane once, the desired concentration can be obtained by installing a similar device in series and passing it through multiple times, or by combining it with distillation. The concentration can be concentrated and separated by 4.

[Effects of the Invention] By using the method of the present invention, a mixed liquid can be efficiently treated at a high permeation rate while maintaining a higher separation coefficient than the conventional separation method using a membrane. This makes the separation system more compact.

The present invention increases processing capacity and reduces costs, and is effective in practical application of membrane separation methods for shortening separation and purification processes in the chemical industry and saving energy, and has extremely great industrial utility. It is.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Sodium alginate (manufactured by Hanbo Kagaku, 1000 cps
) was made into a single close-up aqueous solution, which was cast onto a glass plate and air-dried to obtain a homogeneous transparent sodium alginate film with a thickness of 10 μm.

Attach the extraction to a pervaporation device (effective membrane area 7-OcI), and first use a vacuum pump to pump the secondary side of the membrane to Q, 3 nmH.
g for 10 minutes to dry the membrane. The moisture content of the sample was measured using a Shimadzu electronic moisture meter (EBB-280MOC type), and it was found to be 12-layer tray-shaped. Then, the membrane was heated to 60°C and pervaporative separation was performed while maintaining the secondary side of the membrane at 0.3 mm Hg. The separation coefficient and permeation rate 6 hours after starting pervaporative separation are 29880 and -2, respectively.
It was 029/1-hr.

Example 2 The same sodium alginate membrane as in Example 1 was mixed with ethanol/l.
//After immersing in a water (5:150 weight ratio) mixture at 30°C for 13 hours, it was immersed in an ethanol-1v/water (QO/10 weight ratio) mixture for 1 minute to dehydrate. The moisture content of the extracted material was measured using the moisture meter used in Example 1, and found to be 14.5.
The actual performance was %.

The extractor was attached to the same pervaporation device as in Example 1, and a 60°C ethanol/water (90/lo weight ratio) mixed solution was applied for 5 minutes.
It was applied to one side of the membrane. When pervaporation separation was performed while maintaining the secondary side of the membrane at 0.3 mmHg, the separation coefficient and permeation rate 6 hours after starting pervaporation were 12900, respectively.
．． It was 250 G/J, hr.

Comparative Examples 1 to 2 The same sodium alginate membrane as in Example 1 was added to a mixed solution of ethanol/water (5°150 weight ratio) at 30°C. After soaking for 3 hours, it was placed in the same pervaporation device as in Example i without drying, and 60°C ethanol/water (9/IO
Weight ratio) After supplying the mixed solution to the slope of the seaweed for 5 minutes,
The pressure on the next side was reduced to 0.3 mm) to perform pervaporative separation. The separation coefficient and permeation rate 6 hours after starting pervaporation are ilO, 70, and 510 fJ/rr, respectively.
lh (Comparative Example 1).

'1 Also, the same sodium alginate membrane as in Example 1 was added to a mixed solution of ethanol/water (5V50 weight ratio) at 30°C for 13 minutes.
It was soaked for an hour and allowed to cool in the air. The water content of the extraction is 3
It was 0.5 Bonkei%. When pervaporation separation was performed in the same manner as in Comparative Example 1, the separation coefficient and permeation rate 6 hours after starting pervaporation were 432.3z9/J and h, respectively.
r (Comparative Example 2).

Claims (4)

[Claims] (1) It is composed of a polymer whose main chain is a glycosidic skeleton with an anionic group forming an alkali metal salt with a counter cation, and the water content is 25% by weight or less. A pervaporative separation method characterized in that a water-organic liquid mixture or an organic-organic liquid mixture is pervaporatively separated using a dried membrane. (2) A patent claim in which the anionic group is one or more groups selected from the group consisting of sulfuric acid ester residues, sulfonic acid residues, carboxylic acid residues, phosphoric acid ester residues, and phosphonic acid residues. The pervaporative separation method described in scope item (1). (3) The pervaporative separation method according to claim (1) or (2), wherein the polymer is an alginate or an alginic acid derivative salt. (4) The permeation separation method according to claim (1) or (2), wherein the polymer is a cellulose derivative salt.