JPS5840104A - Separation of mixed liquid - Google Patents

Abstract

PURPOSE:To provide a semi-permeable membrane for vapor separation having high separation efficiency and a large separation treatment amount, by introducing an ionic functional group into the surface of a high molecular membrane having a hydroxyl group. CONSTITUTION:An ionic functional group such as a carboxylic acid group, a sulfate group, an amino group or a heterocyclic group is introduced into the surface of a membrane comprising PVA or a sapoified vinyl monomer-vinyl acetate copolymer having a hydroxyl group by ester bond, acetal bond or ether bond with the hydroxyl group or by direct bond with carbon of a high molecular main chain. An azeotropic mixed liquid is introduced into a mixed liquid chamber 2 partitioned by the obtained membrane 1 from the inlet 5 thereof and taken out from the outlet 14 thereof. On the other hand, an exhaust chamber 3 is evacuated to take out vapor permeating the membrane from an outlet 7. Because the component having higher polarity in the mixed liquid is solvated with an ion present at the surface of the semi-permeable membrane, this semi-permeable membrane is enhanced in the separation capacity thereof and excellent in solvent resistance.

Description

[Detailed description of the invention] The present invention relates to a method for separating mixed liquids.

A so-called pervaporage method in which the mixed liquid is placed on one side of the separation membrane, the other side is evacuated to reduce the pressure, the pressure difference causes the liquid to permeate, and the mixed liquid is separated by evaporation using a low-pressure joint. Shoulder (p, @r va po
va 龜ioa) has been studied since the mid-1950s.

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.

Examples include fractional separation of azeotropic mixtures and solvent isomers with similar boiling points (ortho and para, cis and trans). Other applications include the concentration and purification of pyrolyzable liquid mixtures and fruit juices, and the removal of traces and impurities.

and U.S. Pat. No. 2,953. The SO2 specification uses a vinyl alcohol polymer membrane to separate an azeotropic mixture by pervaporation, and the US Patent No. 5,726,954 uses acrylonitrile as a separation membrane. Use a polymer membrane to remove styrene from a styrene-benzene mixture in 11 minutes! Furthermore, US Pat. No. 2,960,442 uses a composite membrane made of ethyl cellulose and polyethylene or cellulose butyl acetate as a separation membrane that can withstand pressure differences and is durable.

It has been reported that organic compounds can be separated. but,
Nire et al.'s method has poor separation efficiency and the separation throughput is not large enough, so if it is to be implemented industrially, the pervaporation equipment must be enlarged, and its low heat resistance makes it difficult for industrial processes. The drawback is that it requires a cooling process, which increases costs.

The present inventors have studied various methods for improving these drawbacks and separating mixed liquids such as industrially advantageous ζ azeotropic liquid mixtures and close boiling point liquid mixtures, and as a result, they have arrived at the present invention.

That is, the present invention is a method for separating mixed wave bodies using a membrane in which ionic functional groups are introduced onto the surface of a polymer membrane having hydroxyl groups in its molecules.

The polymer having a hydroxyl group in the present invention is a synthetic polymer such as polyvinyl alcohol or saponified vinyl monomer-acetate/vinyl copolymer. (ethylene, propylene, 1-butene, 1-pentene, etc.), vinyl halides, styrene, etc.

In the present invention, more preferred synthetic polymers are polyvinyl alcohol and saponified ethylene-vinyl acetate copolymers.

In this ξ, polyvinyl alcohol has an average degree of polymerization of SOO~
5500. It has a degree of saponification of 85 to 100 and a degree of saponification of 85 to 100 mol%.

In addition, saponified ethylene-vinyl acetate copolymer has an ethylene content of 1 to 60 mol% and a degree of saponification of the vinyl acetate component of AO4 or higher. More preferably, the ethylene content is 10-501iJi1% and the degree of saponification is 95-1.
00 mol%.

Polyvinyl alcohol and saponified ethylene-vinyl acetate copolymer are resistant to organic solvents. It has excellent acid and alkali resistance, making it suitable as a membrane material.Ionic functional groups to be introduced include acids II (carboxylic acid groups, sulfuric acid groups, etc.), salts and base types of these acids (amino groups, complex There is a ring group). Methods for introducing these include ester bonds, acetal bonds, ether bonds with hydroxyl groups of synthetic polymers, and direct bonds between carbons in the polymer main chain and ionic functional groups (-C-X bonds, -C- In the introduction number ζ of a carboxylic acid group in which there is an S-bond, etc., maleic anhydride. Dibasic acid anhydrides such as succinic anhydride or halogenated fatty acids such as monochloroacetic acid are preferably used, aminoacetaldehyde and the like are preferably used to introduce an amino group, sulfuric acid is used as a sulfate group, and imidazole is preferably used as a heterocyclic group. Separation performance is most improved when the ionic functional group introduced is a carboxylic acid group. The carboxylic acid group may be in either the free acid form or the salt form, but as is clear from the examples described later, the carboxylic acid group has a superior separation coefficient of 41 ilt;

The reason why the membrane separation performance improves like this is thought to be because the ions present on the membrane surface cause fluctuations in the microsolution structure of the mixed liquid. In other words, the ions on the membrane surface,
Since the more polar substances in the mixed liquid are solvated, the local concentration of polar solvent increases on the membrane surface, which is thought to improve the separation performance. Since ions are involved in improving membrane performance, it is preferable for the ionic functional group introduced to the membrane surface to be a salt rather than an acid type.

Since the surface ionized membrane thus obtained has excellent solvent resistance, it can be used for separating mixed solvents in many industries such as the chemical industry, food industry, and pharmaceutical industry. The membrane used in the method of the present invention is non-porous and has a thickness (0.1 to 100 microns, preferably 5 to 50 microns). If the film thickness becomes thinner than ξ, the strength of the film will be insufficient, or
Durability is insufficient. Furthermore, if the membrane thickness is thicker than this, the amount of liquid mixture that permeates through the membrane will be small, making it impractical. However, in the case of composite membranes, the thickness can be even smaller, preferably from 0.1 to 10 microns. The shape of the surface ionization treated membrane is usually used as a flat membrane (flat membrane), but it can also be used in other shapes such as a cylinder or a hollow fiber shape to increase the membrane surface area.

The method for separating a mixed liquid according to the present invention will be explained with reference to FIG. This device is divided by the surface ionization treatment membrane 1 into a mixed liquid chamber 2 and an exhaust tL5. A mixed liquid to be separated or concentrated is introduced into the mixed liquid chamber 2 through an inlet 5, and an outlet 4
Take it out. On the other hand, the exhaust chamber 3 may be reduced in pressure by a suitable method, or other liquid or gas may be circulated therein. In addition, 6 in the figure is a membrane support (for example, a stainless steel sintered plate), and 7
is the outlet for the vapor that has passed through the membrane.

In the present invention, it is essential that the pressure on the western side or the outside of the surface ionized membrane that comes into contact with the "mixed liquid" is lower than that on the opposite side, and the larger the pressure difference, the more effective it is. is preferably 0.01 to 50 atm, more preferably 0.5 to 1 atm. Further, the pressure on the side in contact with the "mixed liquid" is preferably 1 (atmospheric pressure) to 100 atm, preferably at or around atmospheric pressure. On the other hand, the pressure on the opposite side is less than 50 atm, preferably less than atmospheric pressure, more preferably less than 400 kg, and even more preferably less than 100 itg.
It is best to maintain the vacuum below. The substance that has passed through the membrane may be extracted in either a liquid or gaseous state under low pressure, but separation efficiency and permeability are better if the substance is evaporated on the low pressure side and extracted in gaseous form.

Therefore, it is preferable to maintain the low-pressure side at a pressure lower than the vapor pressure of the substance that permeates through the membrane. Methods of maintaining the low pressure are to reduce the pressure by drawing a vacuum or to maintain the low vapor pressure by flowing an inert gas. (Also, there is no need to flow liquid etc. on the low pressure side).

The applicable temperature range for the separation method of the present invention is not particularly limited as long as it does not cause solidification or thermal decomposition of the "mixed liquid", but is preferably 0 to 100°C.

In the present invention, the "mixed liquid" that is the substance to be separated is a mixed liquid consisting of two or more substances, and representative examples thereof include azeotropic liquid mixtures and liquid mixtures with close boiling points. .

Examples of azeotropic liquid mixtures include the following. First, as a two-component azeotropic mixture, water-organic matter (
Ethanol, allyl alcohol, propionic acid, propyl alcohol.

Isopropyl alcohol, methyl ethyl ketone.

Isobutyric acid, ethyl acetate, ethyl ether, butyl alcohol (n, see, terL), isobutyl alcohol, isoamyl alcohol, amyl alcohol.

Furfuryl alcohol, tetrahydrofuran.

dioxane, cyclopentanol, other alcohols)
azeotropic mixtures, and even organic mixtures, such as acetic acid-
Organic substances (chlorobenzene, benzene.

Toluene, xylene m1. Methanol-organic substance (acetone, methyl acetate, ethyl acetate, pentane (n), benzene, cyclohexane (n), hexane) one-system azeotropic mixture, organic substance-organic substance mixture such as benzene/cyclohexane, benzene/hexane).

Examples include azeotropic liquid mixtures such as acetone/chloroform. In addition, mixed liquids with boiling points close to each other include ethylbendare/styrene, parachloroethylbenzene/parachlorostyrene, toluene/methylcyclohexane,
Butadiene/butenes.

Examples include systems such as butadiene/butanes.

In addition, three-component azeotropic liquid mixtures include water-carponytrachloride-ethanol, water-trichlorethylene-ethanol, water-trichloroethylene-allyl alcohol, water-trichloroethylene-propyl alcohol,
Examples include water-ethanol-ethyl acetate, water-ethanol-benzene, water-allyl alcohol-benzene, and methyl formate-ethyl bromide-isopentane. In addition to the azeotropic mixture mentioned above, wAf!, which is difficult to separate, can also be used as a "mixed liquid". It also includes rjIIL forms, such as water-acetic acid, as well as liquid mixtures that can be separated by ordinary distillation (eg, water-methanol, water-acetone). Among these "mixed liquids", the method of the present invention can be applied to substances in the "mixed liquids" which are effective in separating the organic mixed liquids, and which encounter the surface ionization treatment membrane. Generally, the more polar substance in the "mixed liquid" passes through the membrane and is separated. If two or more substances in the "mixed liquid" have similar polarities, one operation is sufficient; if they cannot be separated, repeat the operation multiple times to achieve the desired separation. It can also be done with ξ.

Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited in any way by these Examples. EV Muto above) film (Kuraray Eval Film F-20. Ethylene content 35 mo1%, saponification degree 99.1 bacteria 1 g6
．． A film having a thickness of 20 μm) was treated with 10 11 E amount percent of maleic anhydride in a dioxane solution under reflux for 2 hours to obtain a film with 7 mV of maleic anhydride on one surface. The sample was immersed in a 3% by weight potassium hydroxide methanol solution for 5 minutes to obtain a surface maleated IT membrane with a 9% salt content. The surface ionized 111V membrane obtained in this manner was set in the apparatus shown in Fig. 1 (effective for both zs and aa/), and a mixture of equal amounts (by weight) of methyl acetate and methanol was added to the mixing chamber. 50℃
Separation of methyl acetate/methanol was carried out using a maleated 8V membrane membrane in which the potassium salt was not converted into a potassium salt by supplying a shield amount under atmospheric pressure and using a vacuum pump in the exhaust chamber. The separation coefficient am/MA of methanol for methyl acetate is maleic oxidation! &vm 5
It was 11.09 for the 0ro51 potassium salt type.

Note that the separation coefficient a M/ltA is defined by the following equation.

l [1 and Nicho: Weight concentration of M (methanol) and N (methyl acetate) components before membrane permeation M8 and M6: Weight concentration of M and N (methyl acetate) components after membrane permeation Example 2 of maleic anhydride A succinated Bv membrane and its potassium salt type membrane were obtained in exactly the same manner as in Example 1, except that succinic anhydride was used instead.

Then, methyl acetate/methanol was separated in the same manner as in Example 1. As a result, the separation coefficient of methanol for methyl acetate was 4.88 with the acid type membrane. It was 8.09 for potassium salt.

Example 5 Fuccinic anhydride in place of maleic anhydride, polyvinyl alcohol (PV) in place of IV (vinylon film manufactured by Kuraray, degree of saponification 99.8 mo1%, thickness 1125μ)
A succinated PV membrane and its potassium salt type membrane were obtained in exactly the same manner as in Example 1, except that succinic oxide PV film and its potassium salt type membrane were used. Then, methyl acetate/methanol and benzene/methanol were separated in the same manner as in Example-1. The separation coefficients are shown in Table-1.

Table-1

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of a separation device used in the present invention. 1------Surface ionization treatment film 2------Mixed liquid chamber 5-------1 Exhaust chamber 4------Mixed liquid outlet 5 ・------ −・・・Mixed liquid injection port 6−・・・・−
Membrane support 7 - Steam outlet Patent applicant: RiRa Co., Ltd. Agent: Ken Honda, patent attorney

Claims (1)

[Scope of Claims] (1) A method for separating mixed liquids, characterized by using a membrane in which ionic functional groups are introduced into the surface of a polymer membrane having hydroxyl groups. (Separation method according to claim 1, wherein the ionic functional group introduced onto the membrane surface is an acid type or an acid salt. 3) The polymer having a hydroxyl group is polyvinyl alcohol,
The separation method according to claim 1 or 2, which is a saponified ethylene-vinyl acetate copolymer. (4) Claim 1, in which the FI liquid is an organic mixed liquid. The separation method according to item 2 or 5.