JPH052363B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention supplies a liquid mixture to be separated to the feed liquid side (primary side) of two chambers separated by a separation membrane, and reduces the pressure on the permeate side (secondary side). Alternatively, a pervaporation method (pervaporation method) is used in which the vapor pressure is kept low by flowing an inert gas, and components with high affinity with the membrane are preferentially permeated as vapor to the secondary side. The present invention relates to a method for separating water-organic liquid mixtures. (Prior Art) Various experimental examples have been reported in which water was separated from a water-organic liquid mixture by such a pervaporation method. For example US Patent No. 2953502
Experimental example of separating azeotropic liquids using cellulose acetate membranes and polyvinyl alcohol membranes, J. Polymer SCI, Symposium No. 41, 145-
153 (1973), an 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), page 3223, includes an experimental example in which a water-methanol mixed liquid was separated using a grafted polyvinyl alcohol membrane. (Problems to be Solved by the Invention) The pervaporation method is not limited to the concentration by osmotic pressure, unlike the conventional reverse osmosis method, so it is not limited to the separation of low-concentration liquid mixtures; The ability to separate liquid mixtures with a range of concentrations, as well as azeotropes and solvent isomers with close boiling points (e.g. ortho and para isomers, cis and trans isomers) that are difficult to separate using conventional distillation methods. It has the following characteristics: However, the conventional pervaporation method has the following problems and has not been put into practical use. In other words, the separation rate when a mixed liquid passes through a polymer membrane once [generally, the value obtained by subtracting 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] It is expressed as a separation factor α. In other words, α = (W _A /W _B ) in the permeate / (W _A in the permeate)
/W _B ) (in the formula, W _A and W _B indicate the weights of component A and component B, respectively)] are small, so in order to separate or concentrate to the desired concentration, it must pass through a large number of membranes. However, 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/ ^m2hr )
] becomes a high value that is practical, the separation coefficient α becomes extremely low. Therefore, an object of the present invention is to separate a water-organic liquid mixture by a pervaporation method, with a high permeation rate and a high separation coefficient of water to organic liquid. The purpose is to provide a method. (Means for Solving the Problems) In order to achieve the above object, the present inventors have focused on polyvinyl alcohol membranes, regenerated cellulose membranes, cellulose acetate membranes, polyacrylonitrile membranes, etc. that have a high affinity for water. When conducting experiments using separation membranes, we found that, unexpectedly, recycled cellulose membranes can maintain a high permeation rate at a practical level when a specific metal salt is present in a dissolved state in the water-organic liquid mixture to be separated. It was discovered that a method of separating water with an extremely high separation coefficient for organic liquids can be obtained, and the present invention was achieved. That is, in the present invention, when water is separated from a water-organic liquid mixture by pervaporation using a regenerated cellulose membrane, the water-organic liquid mixture is separated from Mn ²⁺ , Fe ²⁺ , Co ²⁺ , Ni ²⁺ , Cu ²⁺ , Zn ²⁺ ,
At least one cation selected from the group consisting of Be ²⁺ and Mg ²⁺ and So ₄ ^2- , H ₂ PO ₄ ,
A water-organic liquid characterized in that at least one type of anion selected from the group consisting of CH ₃ COO ^- and NO ₃ ^- is present in a concentration within a range that does not cause two-phase separation of the water-organic liquid mixture. This is a method for separating mixtures. The regenerated cellulose membrane used in the present invention (viscose method regenerated cellulose membrane, copper ammonium method regenerated cellulose membrane, etc.) is generally referred to as a membrane with a non-porous, homogeneous skinless structure. Film thickness 5-25μ commercially available for use on organs.
(dry) membrane is used. Such commercially available regenerated cellulose membranes are conveniently used in the method of the present invention. Among the above-mentioned regenerated cellulose membranes, ammonium ammonium method regenerated cellulose membranes are preferably used because they provide an extremely high separation coefficient. These films can be manufactured according to known manufacturing methods. For example, in the case of a copper ammonium regenerated cellulose membrane, it can be obtained by dissolving cellulose in a cupric ammonium solution and wet-coagulating it in a sulfuric acid bath. The regenerated cellulose membrane is usually used in the form of a flat plate (flat membrane shape), but it may also be used in the form of a cylinder or hollow fibers to increase the membrane area per unit volume. In the present invention, at least one selected from the group consisting of Mn ²⁺ , Fe ²⁺ , Co ²⁺ , Ni ²⁺ , Cu ²⁺ , Be ²⁺ and Mg ²⁺ is present in the water-organic liquid mixture to be separated. It is necessary that one type of cation be present. Among these cations, Mn ²⁺ or Co ²⁺ is preferred. Further, in the present invention, at least one type of anion selected from the group consisting of So ₄ ^2- , H ₂ PO ₄ ^- , CH ₃ COO ^- , and NO ₃ ^- is present in the water-organic liquid mixture to be separated. It is necessary to do so. Among these anions, So ₄ ^2- or H ₂ PO ₄ ^-
is preferred. In order to have these cations and anions present in the water-organic liquid mixture, a metal salt consisting of these cations and anions may be added and dissolved in the mixture. Such metal salts include:
_MnSO4 , _FeSO4 , _CoSO4 , _NiSO4 , _CuSO4 ,
_BeSO4 , _MgSO4 , Mg _{( H2PO4} ) ₂ , Mg
(CH ₃ COO) ₂ , Mg(NO ₃ ) ₂ , etc. are used, but
Among them, MnSO ₄ , Mn(H ₂ PO ₄ ) ₂ , CoSO ₄ , Co
(H ₂ PO ₄ ) ₂ is preferred. One kind of such metal salt may be added to the water-organic liquid mixture, or a plurality of kinds thereof may be added. Also, the water to be separated -
If the organic liquid mixture already contains the metal salt mentioned above at an appropriate concentration, for example, if it is a liquid mixture mixed with tap water, there is no need to add the metal salt again. In addition, in the present invention, it is sufficient that the above-mentioned cations and anions are present in the water-organic liquid mixture, and the inclusion of ions other than the above-mentioned ions is not ruled out. In the present invention, there are suitable concentrations of cations and anions depending on the type of organic liquid in the water-organic liquid mixture to be separated and the types of cations and anions. It is appropriately selected depending on each system within a range that does not cause two-phase separation of the liquid mixture. For example, in a water-ethanol (1:1 weight ratio) solution, 7
It is preferable that the ions be present in the range of ×10 ⁻⁵ to 5×10 ⁻² mol/Kg. In the present invention, the metal salt present in the water-organic liquid mixture to be separated does not pass through the membrane, so it is concentrated in the non-permeate side. If the presence of metal salts in the organic liquid product is undesirable, it is necessary to remove the metal salts. In this case, if the metal salt is in a precipitated state, the metal salt can be removed by filtration. Further, if the metal salt is in a dissolved state, the metal salt can be easily removed by passing the organic liquid used as the product through a column packed with an ion exchange resin. Water-organic liquid mixtures that can be separated by the method of the invention include water/tanol, water-ethanol, water/n-propanol, water/isopropanol, water/n-butanol, water/isobutanol, water/ n-amyl alcohol, water/n-hexanol, water/2-ethylhexanol, water/n
-Octanol, water/ethylene glycol, water/
1,3-propanediol, water/1,4-butanediol, water/1,2-propylene glycol,
Water-alcohol mixtures such as water/glycerin;
water/tetrahydrofuran, water/dioxane,
Examples include water-organic solvent systems such as water/methyl ethyl ketone and water/acetone. Among these, carbon atoms with a carbon number of 1 or more can be dissolved uniformly in water at any ratio.
4. Separation of liquid mixtures of alcohol (especially ethanol) and water is effective. The pervaporation device used in the present invention is not particularly limited, and any conventionally known device can be used, and such a device can be operated under conventional conditions to separate a liquid mixture. 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. It is. 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. Methods for maintaining the permeate side at reduced pressure include drawing a vacuum to reduce the pressure, or flowing a gas that does not react with the constituent components to maintain a low vapor pressure. The appropriate separation temperature is 40°C or higher and lower than the azeotropic temperature of the organic liquid mixture to be separated. When separating a liquid mixture, if the desired concentration cannot be obtained by passing it through the membrane once, similar pervaporation equipment can be installed in series and passed multiple times, or it can be combined with distillation. can be concentrated and separated to the desired concentration. (Function) According to the present invention, specific cations and anions are made to exist in the water-organic liquid mixture to be separated as described above, and the liquid mixture is separated by pervaporation using a regenerated cellulose membrane. As shown in the examples, the effect of significantly improving the separation coefficient while maintaining a high permeation rate can be obtained, but such an effect is completely unpredictable from conventional knowledge. The reason for this effect is not clear, but by performing pervaporation in the presence of specific ions, the above-mentioned cations are bound in some form to the regenerated cellulose, and the above-mentioned anions exist as counterdentate ions. Therefore, it is presumed that the regenerated cellulose adopts a conformation suitable for separation. In order to obtain such an effect, it is necessary to appropriately select the ion concentration depending on each system as described above. If the ion concentration is too high, ions may permeate through the separation membrane during pervaporation and metal salts may be precipitated on the secondary side of the membrane, resulting in a decrease in the separation coefficient. (Effects of the Invention) According to the present invention, a significantly higher separation coefficient can be achieved while maintaining a higher permeation rate than in conventional membrane separation methods. As a result, the separation system has become more compact, its processing capacity has increased, and its costs have been reduced.
The present invention is effective for practical use as a membrane separation method for shortening separation and purification processes in the chemical industry and saving energy, and has extremely great industrial utility. (Example) Example 1 A pervaporation device (effective membrane area 23.5 cm ² ) equipped with a 12 μm thick Kyuprofan membrane (manufactured by Enka AG, West Germany, product name 150PM) was prepared using ion-exchanged water and reagent-grade ethanol. water-ethanol mixed liquid (ethanol concentration 50% by weight)
The concentration of sulfates of various metals shown in 1 is 7×
10 ^-4 mol/Kg was supplied at a temperature of 60°C, and the ethanol concentration was always 50°C.
The permeate side was suctioned to 1 mmHgg using a vacuum pump while maintaining the weight percentage. The ethanol concentration of the permeated component water that permeated through the membrane was analyzed using a gas chromatograph, and the amount of permeated component was determined by condensing the permeated component. Table 1 shows the separation coefficient and permeation rate of water relative to ethanol 6 hours after starting pervaporation for water-ethanol mixed liquids containing various cations.

[Table] Comparative Example 1 The same Cyprofan membrane used in Example 1 was attached to the same pervaporation device, and sulfates of various metals shown in Table 2, which are not used in the present invention, were The same operation as in Example 1 was carried out by supplying a water-ethanol mixed liquid (ethanol concentration 50% by weight) dissolved at a concentration of 7×10 ^-7 mol/Kg at a temperature of 60°C. Table 2 shows the separation coefficient and permeation rate of water for ethanol 6 hours after starting pervaporation.

[Table] Comparative Example 2 In the same pervaporation device equipped with the same Cuprofane membrane used in Example 1,
Example 1 was carried out by supplying a water-ethanol mixed liquid (ethanol concentration 50% by weight) prepared in the same manner as in Example 1 at a temperature of 60°C without adding metal salts.
I performed a similar operation. Six hours after starting pervaporation, the separation coefficient of water to ethanol was 2.64, and the permeation rate was 12.38 Kg/m ² hγ. Example 2 Magnesium salts that produce the various anions shown in Table 1 were added in the same manner as in Example 1 to the same pervaporation device equipped with the same Cyprofane membrane used in Example 1, at different concentrations. is 7×
The same operation as in Example 1 was carried out by supplying various water-ethanol mixed liquids (ethanol concentration 50% by weight) dissolved at a concentration of 10 ^-4 mol/Kg at a temperature of 60°C. 6 after starting pervaporation
Table 3 shows the separation coefficient and permeation rate of water for ethanol after a certain period of time.

[Table] Comparative Example 3 The same Cyprofane membrane used in Example 1 was attached to the same pervaporation device, and anionic magnesium salts shown in Table 4, which are not used in the present invention, were added. Its concentration is 7x
The same operation as in Example 1 was carried out by supplying a water-ethanol mixed liquid (ethanol concentration: 50% by weight) which had been dissolved at a concentration of 10 ^-4 mol/Kg and heated to 60°C. Table 4 shows the separation coefficient and permeation rate of water to ethanol 6 hours after starting pervaporation.

[Table] Example 3 In the same pervaporation device equipped with the same Cuprofane membrane used in Example 1,
The concentration of sulfates of various metals is 1.5×10 ^-3 mol/
The same operation as in Example 1 was carried out by supplying a water-ethanol mixed liquid (ethanol concentration: 65% by weight) prepared in the same manner as in Example 1 at 60° C., which was dissolved to give a total weight of 1,000 kg. Table 5 shows the separation coefficient and permeation rate of water to ethanol 6 hours and 24 hours after starting pervaporation.

[Table] Example 4 In the same pervaporation device equipped with the same Cuprofane membrane used in Example 1,
Water-isopropanol mixed liquid prepared from ion-exchanged water heated to 60°C in which cobalt ions were present at a concentration of 1.5 x 10 ^-3 mol/Kg and reagent-grade isopropanol (isopropanol concentration: 50% by weight) Example 1
I performed a similar operation. Six hours after starting pervaporation, the separation coefficient of water to isopropanol was 134.3, and the permeation rate was 5.80 Kg/m ² hr. Example 5 The same Cuprofane membrane used in Example 1 was attached to the same pervaporation device, and 60
Cobalt ions form cobalt sulfate heated to ℃
A water-t-butanol mixed liquid (t-butanol concentration: 50% by weight) prepared from ion-exchanged water and reagent-grade t-butanol (t-butanol concentration: 50% by weight) was supplied at a concentration of ^1.5 ×10 -3 mol/Kg. The same operation as in Example 1 was performed. Six hours after starting pervaporation, the separation coefficient of water to T-butanol was 208.3, and the permeation rate was 5.72 Kg/m ² hr. Example 6 Cobalt sulfate was added to the same pervaporation device equipped with the same Cuprofane membrane used in Example 1 at a concentration of 1.5×10 ^-3 mol/Kg of cobalt ions.
Water-acetone mixed liquid (acetone concentration: 50% by weight) prepared from ion-exchanged water heated to 25℃ and reagent-grade acetone.
The same operation as in Example 1 was carried out by supplying . Six hours after starting pervaporation, the separation coefficient of water to acetone is 92.43, and the permeation rate is 3.751.
Kg/m ² hr. Example 7 Cobalt sulfate was added to the same pervaporation device equipped with the same Cuprofane membrane used in Example 1 at a concentration of 0.36×10 ^-4 mol/cobalt ion.
The same operation as in Example 1 was carried out by supplying a water-ethanol mixed liquid (ethanol concentration: 95% by weight), which had been dissolved and prepared in the same manner as in Example 1, at a temperature of 60°C. After 6 hours, the separation coefficient of water to ethanol is 9.07, and the permeation rate is 2.05Kg/m ²
It was hot at hr. Comparative Example 4 A water-ethanol mixed liquid ( Example 1 by supplying ethanol concentration: 95% by weight) at a temperature of 60°C
I performed a similar operation. The separation coefficient of water for ethanol after 6 hours is 3.32, and the permeation rate is 5.110.
Kg/m ² hr. Example 8 Cobalt sulfate was added to the same pervaporation device as in Example 1 equipped with a cellophane membrane (dialysis tube manufactured by UCC) with a thickness of 21μ.
Dissolve at 1.5×10 ^-3 mol/Kg at 60℃
Water-ethanol mixed liquid prepared in the same manner as in Example 1 (ethanol concentration: 50% by weight) heated to
The same operation as in Example 1 was carried out by supplying . Six hours after starting pervaporation, the separation coefficient of water for ethanol was 47.36, and the permeation rate was
It was 4.08Kg/m ² hr. Comparative Example 5 Water-ethanol prepared in the same manner as in Example 1 without adding metal salts in the same pervaporation apparatus as in Example 1 equipped with the same cellophane membrane used in Example 8. The same operation as in Example 1 was carried out by supplying a mixed liquid (ethanol concentration: 50% by weight) at 60°C. Six hours after starting pervaporation, the separation coefficient of water to ethanol was 2.65, and the permeation rate was 5.96 Kg/m ² hr.

Claims (1)

[Claims] 1. When a water-organic liquid mixture is separated by pervaporation using a regenerated cellulose membrane to allow water to pass through the membrane, Mn ²⁺ , Fe ²⁺ , Co ²⁺ are present in the water-organic liquid mixture. , Ni ²⁺ , Cu ²⁺ , Zn ²⁺ ,
At least one cation selected from the group consisting of Be ²⁺ and Mg ²⁺ and SO ₄ ^2- , H ₂ PO ₄ ^- ,
A water-organic liquid mixture characterized in that at least one anion selected from the group consisting of CH ₃ COO ^- and NO ₃ ^- is present in a concentration within a range that does not separate the water-organic liquid mixture into two phases. separation method.