JPS58183904A - Novel separative concentration method of organic solvent - Google Patents

Abstract

PURPOSE:To contrive to enhance coefficient of separation and a permeation speed, by a method wherein a porous membrane with specific average pore radius is used in the separative concn. of an org. solvent and one surface thereof is contacted with a solvent with specific properties. CONSTITUTION:Cellulose acetate porous membranes 1, 3 each of which has a membrane thickness of 3.1X10<-3>cm, an average pore diameter (2ra) is 1.2X10<-5> and a void ratio is 68% are mounted to a filter apparatus so as to interpose a packing 8 therebetween. A solution 4 comprising methylcyclohexane and ethanol is supplied to the side of the membrane 1 which is in turn pressurized to be loaded with pressure of DELTAPt. In addition, a solvent 2 comprising water is supplied to the gap between the membranes 1, 3 from a cylinder 7 to adjust pressure to DELTAPt/2 by a weight 9. When coefficient Pe of permeation and coefficient alpha of separation are calculated from the elution amount and the composition of a filtrate from a filtrate outlet port 6, alpha is 20 or more while Pe is 10<-7>-10<-8> (cm<2>/sec cm Hg) when formula DELTAPt<=2X10<-5>/ra is satisfied and 10<3>-10<4> times of values are shown as compared to a conventional pervaporization method.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for separating and condensing an organic solvent from a homogeneous solution (hereinafter abbreviated as "solution person") containing at least one type of organic solvent. Furthermore, in detail, the average pore diameter (hereinafter referred to as 2
〒Denoted as a, 7'' is the average hole radius, the unit is 5+) is 10
-6 Through the superior porous membrane (hereinafter abbreviated as porous membrane X),
One surface of the porous lXX (hereinafter abbreviated as Xa surface) is in contact with the Fi solution, and the other surface (hereinafter abbreviated as It is a good solvent for formation, but #! At least one component in the solution is a non-solvent and is in contact with a solvent (hereinafter referred to as solution #1B) that causes phase separation in the solution, and is a solvent BFi2.
71 is 1o-'a11 or more porous j [(hereinafter referred to as porous JA
The effective pressure difference ΔP (unit: t*cmHg) applied to the porous membranes X and Y is as follows 11)
The present invention relates to a membrane separation method in which a solution is ultrafiltered under conditions satisfying the following formula to separate and condense an organic solvent.

ΔP≦2×10-'/rll (11) In the present invention, a porous membrane means a membrane in which the presence of pores has been confirmed using an electron microscope, etc., and in which through-holes are present, and a conventional reverse permeation membrane or a dialysis-type membrane is used. It does not include membranes used in artificial kidneys.In addition, in this porous membrane, the maximum pore diameter in the porous membrane can be clearly determined by the bubble point method.Therefore, the porous membrane in the present invention A so-called screen filter has the function of collecting particles to be filtered in a flat plane.A homogeneous solution (solution) is a heat-generating solution that is composed of two or more low-molecular-weight compounds, and each component is mixed in molecular form. Dynamically, it means a one-phase liquid.In addition, in the present invention, a low-molecular compound is a compound with a molecular weight of 1000 or less, and a porous polymer membrane is a compound composed of a polymer with a molecular weight of 10, 0 or more. porous membrane, copolymer (block copolymerization,
Contains H4, which is composed of polymer mixtures (such as polymer/dumb copolymerization, graft copolymerization, etc.) or polymer mixtures.

Membrane separation technologies for separating and concentrating solvents in solutions, separating and concentrating solutes in solutions, or separating and concentrating insoluble matters in solutions include: ■Membrane separation technology using reverse osmosis membranes, ■Pembrane separation technology
Membrane separation technology using rvaporation method, ■ultrap
Membrane separation technology using permeable membranes is known.

Seawater desalination using reverse membranes has been partially put into practical use. The average pore size of the membranes employed in this method is usually 5oX (0
,00-54m) or less. In general, separation by reverse permeation J[K requires a high operating pressure of 20 to 50 atm, and a permeability coefficient Pe of 10'' (c11/relative).

Since it is very small (cmHg), the efficiency increases rapidly, and the drawback is that the Mahyu device must be made larger.

The average pore size of the membrane used in pervaporation is
o1 or less. In this method, one side of the membrane is evacuated to 1 iK to allow the solvent to pass through the membrane in a vapor state, and then cooled and condensed. Many studies have been conducted as a method for separating and concentrating solvents in solutions. Pressure difference #1 Normal 1
At atmospheric pressure, the current limit of the separation coefficient α is around α=25 at most. Transmission coefficient PeFi, 10-” (cII
/sa:0cmHg), which is very low, and requires a large amount of energy to maintain and cool the vacuum line, so we have to be blind to the technology, which is still far from practical use. Note that the separation coefficient α is defined by the following equation.

Ultra-needle penetration using a membrane with an average pore size of 10-1 or more cannot separate and concentrate the solvent in a homogeneous solution under normal pressurized operating conditions. It was never considered. Furthermore, academically, it has been considered that it is impossible to separate and concentrate the solvent in a solution with a membrane having an average pore diameter of 10 mm or more.

As described above, in the currently generally known membrane separation technologies, there is currently no membrane separation technology that has a large permeability coefficient pe and a large separation coefficient α when separating and concentrating the cap medium in the purification solution.

The inventors of the present invention have conducted intensive studies to overcome the limitations of current membrane separation technology, and have surprisingly found that the permeability coefficient pe is sufficiently large in separating and concentrating a solvent from a homogeneous liquid. To the coefficient α? α〉10 or −〉1
We have completed a temporary membrane separation method for solvent α of 0, leading to the present invention.

The present invention will be explained in detail below.

□It is generally said that in order to increase the permeation rate [J per unit area of the membrane, it is sufficient to increase the porosity Pr, the average pore diameter 27a, and the pressure difference ΔP, or to decrease the Fi thickness d. However, under normal pressurization f or depressurization operating conditions, there is a negative correlation between the permeation rate J and the separation coefficient α, where α>1.
There is a positive correlation in αS1, and when J is increased, α approaches IK without exception. It was thought that it was impossible to perform highly efficient separation while increasing both J and α using ultrafiltration.

However, the present inventors have discovered that the homogeneous liquid to be filtered (#!Liquid A) and another specific solvent (solvent B) can be mixed through a porous membrane (porous 1jX) with an average pore diameter of 10-'crn or more. When the solvent B is in contact with the porous membrane Y and the effective pressure difference ΔP loaded on the porous membranes X and Y satisfies the formula il1,
It was discovered that a specific component can be separated and concentrated from solution A, and the present invention has been completed.

That is, the first feature of the present invention is that the pore size is 1 kFi and the average pore diameter is 10
The point lies in the use of a porous membrane of -.alpha. or more. Since the average pore diameter is more than twice that of conventional membranes for reverse permeation, the permeation rate J per unit area of the porous membrane is ten times or more that of membranes for reverse permeation in the method of the present invention.

The larger the average pore diameter, the larger the permeability coefficient Pe of #1, but as will be described later, the effective pressure difference ΔP applied to the membrane must be reduced. Therefore, in this case,
As a result, J becomes small and becomes impractical. The maximum value of the pore diameter range adopted in the method of the present invention depends on the separation target and the material of the porous membrane, but is usually 10-"cIR or less, preferably 1G-'51 or less. The average pore diameter is to-@ Below z, J decreases steadily and, surprisingly, the separation coefficient α decreases inversely. Therefore, it is desirable that the hole shape be close to a circular shape.

The second feature of the present invention is that the Xa direction is in contact with the homogeneous solution to be separated (solution membrane) through the porous membrane mxt, and XbrkJ is a non-solvent of the porous membrane, but it is also The solvent (solvent B) which is a good solvent and a poor solvent for at least one component is in contact with the non-solvent (solvent B). A typical effect of solvent B is that if it continues to be added to solution A, the solution after addition will cause phase separation, such as separation into two phases. The components that pass through the porous membrane are
It is strongly influenced by the chemical structure of the porous membrane material used.

For example, when using a porous agricultural water polymer membrane such as regenerated cellulose, the components that pass through porous membrane X and mix into solvent B are the hydrophilic components in solution A; If the pores of a hydrophobic polymer such as polypropylene are used, the hydrophobic component will be removed. Solvent B is a good solvent, a poor solvent, or a non-solvent for the porous membrane Become. However, if the density of the solution IB is higher than the density of the solution to be separated, the solvent B should be
There are 4 cases in which it is desirable to use a 1X (D#lA agent). An example is the case of ultrafiltration using the filtration device shown in Figure 2. If so, separation and concentration by ultrafiltration is not possible except in special cases.An exceptional special case is a mixture of acetone and phenol as solution A, water as solvent B, and a temperature of 60°C. There may be cases where the above is the case.

On the other hand, if the solvent B is a non-solvent for all the components of the solution, separation and concentration by ultrafiltration is not possible. 1st
In the case of the filtration device shown in the figure, it is preferable that the chemical structure of the solvent B differs from that of the material of the porous aX. In the case of the filtration shown in Figure 2, the chemical structure of the solvent B may be similar to that of the material of the porous membrane X.

Figure 1 shows a horizontal ultrafiltration device used in the method of the present invention;
FIG. 2 shows an embodiment of the ultrafiltration device that was also dedicated. #ip
liquid, (6) is the door liquid outlet, (7) is the replenishment cylinder for solvent B, (B> is the backing, (9) is the pressure adjustment weight,
QI is a pressurizing device.

The third feature of the present invention is that the solvent B is in contact with a porous membrane (porous membrane Y) having an average pore diameter of 10-@3 or more. The maximum value of the average pore diameter depends on the chemical structure of solvent B and the material of the porous membrane, but is usually 1 G-'Ql or less, preferably i
o-'i: less than or equal to m. When 2'Fa becomes less than 10-.country, J becomes significantly smaller and the separation coefficient α also decreases. The porous NY makes it possible to significantly reduce the ratio of solvent B in the final p-liquid discharged from the furnace), thereby increasing the concentration of the specific component to be separated and concentrated in the F-liquid. The material of the porous NY does not necessarily have to match the material of the porous membrane X. However, the solvent B must not be a non-solvent with respect to the porous membrane Y, or an adsorbing agent. The spatial distance between the porous membrane Y and the porous membrane X is preferably as narrow as possible, and is usually 1 dew or less. K is necessary to keep the separation coefficient α high by replenishing the solvent Bt little by little on the outside of the yarn. Solvent B can be used even if it is impregnated into tff paper or the like or into the voids of the particulate matter.

The solubility parameter of the material polymer for porous @X and Y is 10
0m/d)h or less or 13(d/d)3'' or more is preferable because the selectable range of solvent B is widened.More preferably, the solubility parameter of the substance falls within the above range. Of course, it is possible to separate and concentrate organic solvents by ultrafiltration using this membrane.In the case of a porous membrane made of a material with a solubility parameter of 15 (m/cII) or higher, solvent B If a hydrophobic solvent with a solubility parameter of 9 (aJt/m) or less is used, the solution A that can be separated and concentrated will have a wide range of targets.

A fourth feature of the present invention is that ultrafiltration is performed at a pressure within a specific effective pressure difference ΔP.

That is, the effective pressure difference Δ applied to the porous membranes X and Y
Ultrafiltration is performed within a range where P (unit: titOWIHg) satisfies formula 111.

△P≦2X10-'/rJ1 ill where △P
is the "pressure of solution A's solvent B" for porous MX, and [pressure of solvent B - recovered F] for porous membrane YK.
It means "all pressure". Therefore, the flow of components to be separated and concentrated in solution A or components to be separated and removed from solution A is as follows: porous aX→solvent B→porous membrane Y. 1
For filtration outside the range of Equation 11, the separation coefficient α becomes close to 1,
It becomes virtually impossible to separate and concentrate specific substances. The value of △P that is effective for separation and concentration also depends on the shape of the pores, and 27a and Pr
For porous membranes in which each of the pores is the same, the closer the shape of the pores is to a circle, the larger the value of ΔP is. Equation (1) shows the range for circular pores.

In the present invention, since the number of components on the F liquid side is at least three components, the separation coefficient α is defined by the following equation.

α3 [weight concentration of target substance in solution F/(weight concentration of component i in JP liquid − weight concentration of target substance in liquid p)/[weight concentration of target substance in solution A 11[/(1− Weight of target substance in solution A)] Here, component i means all components in solution A. When ultrasonic waves are generated from a direction perpendicular to the porous membrane surface, the solvent Biyang near the membrane surface generates compressional waves in solution A.
Both the permeability and separation coefficients increase by 10-30.

This is probably due to the stirring effect of both liquids A and solvent B in the film.

As described above, according to the present invention, in separating and concentrating a solvent, it is possible to increase the separation coefficient α while also keeping the permeability coefficient Pe large, and to quickly extract from a homogeneous solution.
The target solvent can be separated at high concentration. In addition, in the present invention, the membrane has a large average pore diameter of 10-61 or more and does not struggle, and the membrane thickness d, pressure difference ΔP1 porosity P
If the following conditions are satisfied regarding r and average pore diameter 2ra,
Highly efficient separation is possible.

Next, the present invention will be described with reference to examples. Prior to the examples, a method for determining each physical property value will be described below.

<Average pore diameter 27a> Pure water gold at 25°C with a pore diameter of 0.2 μm.
The sample is filtered through a porous pore (manufactured by General Jelectric, product name: Nuclepore) to prepare pure water (f-) free of fine particles. If you measure the filtration rate fJ (country/1) per unit area of the membrane, it will be 27 (
cm) is where: ηW is the viscosity of pure water, which is usually 1 centivoise. d is the film thickness (Ct-), measured with a micrometer.

Porosity Pr> From the actual ml value of the apparent density ρ of the porous membrane, Prti.

It is calculated using the following formula.

pr=(1-pa/pp)
Calculated as B・d.

Separation coefficient α〉 Calculate the component concentrations in the solution and F solution using a gas chromatograph (
α is calculated by substituting these values into the formula for defining α in the text.

Permeability coefficient Pg > Using the apparatus shown in Fig. 1, -1p overspeed V (ol/see
), pressure difference △Pt (cmHg), effective filtration area S (d), membrane thickness dt (z), permeability coefficient Pe
t; given by a linear equation. .

However, the combination of dtFi porous membrane x, y, and solvent B -
The film thickness (c-) and ΔPt when considered as individual porous films are the pressure differences between solutions A and F.

Example 1 Cellulose acetate porous membrane (1112
) Thickness d! 3. I x 10-s, 2″ra
= 1.2

The liquid thickness of solvent B was adjusted by the thickness of the backing of porous membranes X and Y (usually 0.5 mm). Figure 1: A porous membrane X%Y is attached to an O filtration device, a solution composed of methylcyclohexane and ethanol (4:1 weight ratio) is used as the total solution A, and the solution A is pressurized to a pressure of △pt. Load. Load W is adjusted so that the pressure of solvent B becomes ΔPi/2. The amount of Toda from the F liquid outlet was determined, the composition of the F liquid was determined from a gas chromatograph, and the permeability coefficient Pe and separation coefficient α were determined. Table 1 summarizes Pe and α determined for Δpt of seeds.

However, the component to be separated and concentrated is ethanol.

As is clear from Table 1, Δp(-=ΔPt/2)
When the value of no longer satisfies the il1 formula, αHt, o becomes 0.
Under the conditions within the scope of the present invention, αFi is 20 or more and Pe is 1
0-f~10-・(a11/sa: , cmHg
), one of the conventional perVaporation methods
It shows a value of 08 to 104 times. Furthermore, the water l in the p-liquid
! 1 degree is 10-20-(weight ratio), and porous! IXY
It can be seen that the ratio of solvent B mixed into liquid V was significantly reduced.

Example 2 Polyethylene porous M (・4==4
jX 1 G-”e-rR, 2raz3j X 10-
" 51, Pr = 47%) are used as porous membranes X and porous membrane Y, and water is adopted as solvent B. Similarly to Example 1, a solution (
4:1 weight ratio) was ultrafiltered. When the pressure difference △pt applied to jl is 1.0 mHg, Pe is 8.
5×10−·, α is 0.12, and the concentration of methylcyclohexane in the furnace liquid is about 97°. ν Moisture in the liquid #fFi is less than 0.5, and the porous membrane Y allows the solvent B to
The mixing of F into the F liquid was almost completely achieved.

Example 3 Cellulose linter (average molecule t2jx 10') warehouse,
After dissolving various concentrations of 4 to 12% by weight in a cupric ammonia solution prepared using a known method, 12% by weight of acetone was added to the solution, and after stirring, the solution was heated to an acetone vapor atmosphere concentration of 30°C. Flow with a 250 μm thick applicator onto a glass plate placed in an atmosphere with a saturated vapor pressure of 80 −,
After being left in this atmosphere for 60 minutes, it was soaked in a 20℃ sulfuric acid aqueous solution for 15 minutes.
After soaking for a minute, wash with water, absorb moisture with t-F paper, and soak for 20 minutes.
Regenerated cellulose porous membranes with different average pore diameters of 27a were prepared by immersing them in acetone at ℃ for 15 minutes to replace the moisture in the membrane with acetone, sandwiching them between Pljl and air-drying them at 30℃. Film X was used.

A polypropylene porous membrane obtained by a known method was used as the porous membrane Y, and one whose average pore diameter was close to that of the porous membrane
The water impregnated into F paper as solvent B is used as solution A.
A mixture of benzene and chlorine (weight ratio 1:
1) was used. The pressure difference is 2. expressed in △pt. QaIIHg
And so. The pressure of the solvent BC) portion is Fi(M)Δpt. From the component composition and filtration rate of the obtained solution, α
, Pe'5r calculation friend. #! Table 2 summarizes the results obtained.

Within the scope of the present invention, Pe and α have relatively small dependence on pore size;
It can be seen that ethanol is significantly concentrated.

[Brief explanation of the drawing]

[Figure 1 is an explanatory diagram showing an aspect of a horizontal ultra-V filtration apparatus used in the method of the present invention. Agent Sei Shimizu. (

Claims (1)

[Claims] (11) In separating and concentrating an organic solvent from a homogeneous solution containing at least one organic solvent (abbreviated as solution membrane), a porous membrane with an average pore diameter of 10-'ffi or more (abbreviated as porous gx) is used. ), one side of the porous membrane
It is a non-solvent for porous N (abbreviated as porous membrane Y) of more than 100 ml, and is a fi-east solvent for at least one component in solution A, but is a non-solvent for at least one component and is compatible with the solution. The effective pressure difference ΔP in contact with the solution 1%' (abbreviated as solvent B) that causes separation, in contact with the solvent B#'i porous membrane YK, and under the negative load on the porous membranes X and YK is expressed by the formula (1: % formula % (1 ) A membrane separation method characterized by passing a solution through an ultraviolet V and troweling to separate an organic solvent under conditions satisfying the following. /cd)' f or less or 13 (at/li voice or more). (3) At least one surface of the liquid surface in contact with the porous membrane. The membrane separation method according to claim 1 or 213 of the patent, in which the membrane is vibrated by ultrasonic waves. (4) As a polymer material constituting the porous membrane X and Y tube,
A hydrophilic polymer porous membrane with a solubility parameter of 15 (m/m )3A or more is used as solvent B, and a hydrophobic solvent with a solubility parameter of 9 (m/a11)b or less is used in claims 1 to 3. The membrane separation method according to item 3.