JPS647052B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for efficiently separating water from a mixed solution of water and alcohol to concentrate alcohol.

BACKGROUND OF THE INVENTION In recent years, there has been increasing interest in the use of membranes in separation and purification processes. This is a technology that has the potential to respond to today's challenges of resource and energy conservation, and because membrane separation is a type of low-temperature process, it can be used to separate and purify substances that are easily denatured by heat, and which cannot be separated by distillation alone. This is because it is expected to have the potential to separate difficult structural isomers.

Currently, examples of membrane separation in practical use include desalination of seawater using reverse osmosis membranes, production of ultrapure water for semiconductor manufacturing, etc., artificial dialysis using ultrafiltration membranes, and separation into blood components. or concentrating oxygen from air using a gas separation membrane. However, liquid separation including water-alcohol separation has not yet reached the level of practical use. This is because a separation membrane that meets this purpose has not yet been developed.

Although it is difficult to develop separation membranes suitable for liquid separation, there are high expectations for membranes for liquid separation.
For example, if water-alcohol separation becomes possible, more efficient alcohol production can be expected instead of conventional distillation. That is, since alcohol can be concentrated at near room temperature, energy for high-temperature heating can be saved, and it is also possible to achieve continuous alcohol production and separation in the same process. However, in order to achieve this purpose,
Not only separability, but also mechanical strength, chemical stability,
It goes without saying that a separation membrane with excellent durability of performance is essential. No matter how good the separation performance is, if the membrane is insufficiently strong, chemically reactive and susceptible to oxidation or deterioration, or has poor robustness, it cannot be used for practical purposes. I can't stand it.

Generally, in order to preferentially permeate and separate water from a water-alcohol mixed solution through a membrane, it is sufficient to use a material with as high an affinity for water as possible for the membrane. Examples of membrane materials that have a high affinity for water include cross-linked polyvinyl alcohol, regenerated cellulose, acetyl cellulose, chitosan, and acrylic acid-acrylonitrile copolymers, which have been studied for water-alcohol separation. Although there are differences in size, both are known to selectively transmit water.

Permeation separation of water and alcohol is carried out reflecting the difference in the ability of water and alcohol to dissolve and diffuse inside the membrane. That is, if a hydrophilic group is present in the membrane, the affinity for water will be greater, and water will selectively permeate through the membrane. Ionization of the components within the membrane is a more effective means for increasing the affinity with water. As a membrane with an ionization structure, a naphion membrane (journal of
Membrane Science, Vol. 24, p. 101 (1985)), CMV membranes and AMV membranes (Ibid., No. 22)
vol., p. 333 (1983)), copoly(1-butyl-4-vinylpyridinium iodide-acrylonitrile) membranes (Polymer Proceedings,
(Vol. 34, No. 3, Page 401), or ionized graft polymerized membrane (Japanese Patent Application No. 269951/1982). In general, these ionized structure membranes have excellent water selective permeability.

However, from a practical standpoint of separation membranes, each of them has the following drawbacks and cannot be said to be necessarily satisfactory.

First, ion exchange membranes generally have a high crosslinking density;
Also, since the membrane is relatively thick, the rate of permeation is low.
Ion exchange membranes were originally created to be applicable to small inorganic ions and metal ions, and
It is not designed to be suitable for separating systems such as alcohols.

Copolymer membranes have the advantage of being able to utilize polymeric materials having various ionic groups. However, such ionic groups have a high affinity with water and are therefore used for the purpose of water-alcohol separation, but if the content of ionic groups in the polymer is too high, This may cause problems such as easy dissolution in water or damage to the membrane. That is, the content of ionic groups is only a few percent at most, and therefore there is a limit to the improvement in separation performance.

In the grafted ionization membrane, a mechanically and chemically robust polymer material is selected as the substrate membrane, and a separation active layer is formed on this. In other words, the feature is that the mechanical strength is shared by the substrate membrane, and the separation property is shared by the ionized graft layer, allowing them to perform their functions. However, graft polymerization generally depends on the type of monomer and substrate polymer.
Alternatively, it is strongly dependent on polymerization conditions, and for this reason it is not always easy to obtain an optimal membrane as a separation membrane. In other words, there are many problems in producing separation membranes.

Problems to be solved by the present invention The present invention overcomes the drawbacks of the conventional methods and efficiently separates water from a mixed solution of water and alcohol using a simple separation membrane and concentrates the alcohol. The purpose is to provide a method to do so.

Means for Solving the Problems As a result of various studies, the present inventor has developed a structure as shown in Figure 1, in which a certain type of polymer ion salt layer is provided between two ultrafiltration membranes. The inventors have discovered that the above objects can be achieved by using a composite membrane as a separation membrane, and have accomplished the present invention.

That is, the present invention provides a composite membrane in which a layer of a polymer ion salt selected from polymers of organic ammonium salts and organic sulfonates having ethylene bonds is provided between two ultrafiltration membranes. , provides a method for concentrating alcohol characterized by passing a mixture of water and alcohol.

Ultrafiltration membranes suitable for the composite membrane used in the alcohol concentration of the present invention include, for example, regenerated cellulose membranes such as Cyprofan membranes, which have already been put into practical use for dialysis, acetyl cellulose membranes, chitosan membranes,
Examples include a polyvinyl alcohol film and a polyacrylonitrile film. These membrane materials are water,
It is stable against alcohol and a mixed solution of both, and will not dissolve or be damaged even if it comes into contact with the solution during separation of a water-ethanol mixed solution. Therefore, it is suitable for creating a separation membrane for the purpose of alcohol concentration.

The polymer ionic salt used in the present invention is a polymer of an organic ammonium salt and an organic sulfonate having an ethylene bond, that is, a polymer in which at least one hydrocarbon group having an ethylene bond is bonded to a quaternary nitrogen atom. ammonium salts or polymers of hydrocarbon sulfonates with ethylene bonds, such as poly(allylammonium chloride), poly(vinyltrimethylammonium chloride), poly(allyltrimethylammonium chloride), poly(vinylbenzyltrimethylammonium chloride) ), sodium salt or potassium salt of polyethylene sulfonic acid, sodium salt or potassium salt of polystyrene sulfonic acid, etc. are used.

These polymeric ionic salts have high molecular weight,
It needs to be large enough to not slip through the pores of the ultrafiltration membrane that sandwich it. Low-molecular organic compound salts and inorganic salts cannot be used because they elute from the ultrafiltration membrane. The minimum molecular weight of the polymer ionic salt that can be incorporated into the composite separation membrane depends on the balance with the ultrafiltration membrane. For example, since the Cyprofan membrane retains molecules with a molecular weight of 10,000 or more, it is necessary to use a polymer with a molecular weight higher than this.

For the separation membrane, per area (1.0cm ² ) of the ultrafiltration membrane,
It can be produced by a simple operation of inserting 1.0 to 500 mg, more preferably 1.0 to 100 mg, of a polymer ion salt.

The ultrafiltration membranes used may be of the same type on the supply side and the permeation side of the liquid to be permeated, or may be of different types.

The water-alcohol separation operation using this composite membrane can be performed, for example, by pervaporation. The pervaporation method is a well-known method in which a solution to be separated is brought into contact with one side of a membrane, and the other side is vacuum-suctioned to effect separation. The components vaporized into the vacuum system through the membrane are stopped by cooling using liquid nitrogen or the like. This method is effective for separating azeotropic mixtures and isomer mixtures that are difficult to separate by distillation.

Separation performance is expressed using a separation coefficient (α). This separation coefficient is an index given by the following method.

Let us now consider the permeation separation of one component B from a mixed solution of two components A and B. Let the concentrations of each component A and B on the supply side through the membrane be X _A and X _B ,
In addition, the concentrations of each component of A and B on the transmission side are Y _A ,
Assuming Y _B , the separation coefficient α _B/A of B is given by the following equation.

_αB/A =( _YB / _YA )/( _XB / _XA ) The larger the value of α, the better the separation performance. Comparing the separation coefficient of the polymer ion salt-containing composite membrane of the present invention with the separation coefficient of a membrane that does not contain a polymer ion salt, which is simply a stack of two ultrafiltration membranes, the separation coefficient increases in both cases. The separability is improved. The extent of this depends on the type of polymer ion salt, ultrafiltration membrane, and concentration of alcohol supplied, but within the scope of the study, the value of α has been improved from several times to several tens of times, and this method shows that This shows that water can be more efficiently permeated and separated from a water-ethanol mixed solution, and that it is effective for concentrating alcohol.

As described above, the separation performance of a composite membrane containing a polymer ion salt is comparable to that of known separation membranes. The mechanism of permeation through this separation membrane is that, in the first stage of permeation, water preferentially permeates from the water-alcohol mixed solution to the layer where the polymer ion salt is present due to osmotic action, and in this way water becomes abundant. It is thought that permeation separation due to pervaporation is finally occurring from the layer. The result of excellent separability is closely related to this permeation mechanism.

Effect of the invention The effects of this invention are listed below.

1) The separation membrane can be constructed by a simple method of inserting a polymer ion salt between the ultrafiltration membranes, and 2) The selectivity of water permeation from a water-ethanol mixed solution can be increased.

3. The permeation rate can be increased in a water-ethanol mixed solution, especially in a region where the ethanol concentration is low.

Since the present invention has the above characteristics, it can be suitably used for purposes such as concentrating alcohol by separating and removing water from a fermentation solution in advance.

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

Example 1 A separation membrane was prepared by loading 0.1174 g of poly(allylammonium chloride) between two Cyprofuran membranes. The weight of the polymer ion salt per effective area of the separation membrane is 9.35 mg/cm ² . Using this membrane, we attempted to separate water and ethanol by pervaporation.

At 30℃, when the concentration of the supplied ethanol aqueous solution is 16.1, 45.1, 67.4, and 89.0%, the permeation rates are 1.86, 0.96, 0.53, and 0.05 Kg/m ² ·hr, and the separation coefficient α of water for ethanol is 8.4, 25.7,
It was 260.4 and 335.2.

Example 2 With the membrane used in Example 1, water was removed at 40°C.
An attempt was made to separate ethanol. When the concentration of the supplied ethanol aqueous solution is 16.1, 45.1, 67.4, and 89.0%, respectively, the permeation rate is 2.39, 1.35, 0.60, and 0.07 Kg/
m ² hr, and the separation coefficient α of water for ethanol
were 15.6, 38.4, 91.2, and 97.4.

Example 3 With the membrane used in Example 1, water was removed at 50°C.
An attempt was made to separate ethanol. When the concentration of the supplied ethanol aqueous solution is 16.1, 45.1, 67.4, and 89.0%, respectively, the permeation rate is 3.25, 1.66, 0.66, and 0.11 Kg/
m ² hr, and the separation coefficient α of water for ethanol
were 20.4, 38.7, 152.7, and 198.0.

Example 4 A separation membrane was prepared by loading 0.0550 g of poly(allylammonium chloride) between two Cyprofuran membranes. The weight of the polymer ion salt per effective area of the separation membrane is 4.38 mg/cm ² . Using this membrane, we attempted to separate water and ethanol by pervaporation.

At 40°C, the permeation rates are 1.85, 1.12, 0.46, and 0.09 Kg/m ² ·hr when the concentrations of the supplied ethanol aqueous solution are 16.1, 45.1, 62.9, and 89.0%, respectively.
Also, the separation coefficient α of water for ethanol is 8.4,
They were 18.1, 42.0, and 128.3.

Example 5 A sample was prepared by loading 0.0230 g of poly(allylammonium chloride) between two cyprofuran membranes.
The weight of the polymer ion salt per effective area of the separation membrane is
It becomes 1.83m/cm ² . Using this membrane, we attempted to separate water and ethanol by pervaporation.

At 40°C, the permeation rates were 1.66, 1.23, 0.66, and 0.19 Kg/m ² hr when the concentrations of the supplied ethanol aqueous solution were 16.1, 45.1, 67.4, and 89.0%, respectively.
Also, the separation coefficient α of water for ethanol is 10.0,
They were 15.3, 21.5, and 53.9.

Example 6 A separation membrane was prepared by loading 0.0550 g of poly(vinylbenzyltrimethylammonium chloride) between two Cyprofuran membranes. The weight of the polymer ion salt per effective area of this separation membrane was 4.38 mg/cm ² . Using this membrane, water-ethanol separation was performed by pervaporation.

At 40°C, the permeation rates are 2.46, 1.15, 0.59, and 0.32 Kg/m ² ·hr when the concentrations of the supplied ethanol aqueous solution are 16.1, 45.1, 62.9, and 89.0%, respectively.
The separation coefficient α of water for ethanol is 3.0,
They were 5.1, 8.0, and 11.0.

Example 7 A separation membrane was prepared by loading 0.0382 g of polystyrene sulfonic acid sodium salt between two Cyprofan membranes. The weight of the polymer ion salt per effective area of this separation membrane was 3.04 mg/cm ² . Using this membrane, water-ethanol separation was performed by pervaporation.

At 40°C, the permeation rates were 2.73, 1.56, 0.84, and 0.36 Kg/m ² hr when the concentrations of the supplied ethanol aqueous solution were 16.1, 45.1, 62.9, and 89.0%, respectively.
The separation coefficient α of water for ethanol is 2.6, 4.5,
It was 6.1 and 9.5.

Comparative Example 1 Water-alcohol separation by pervaporation was carried out by stacking two Cyprofan membranes and using a membrane containing no polymer ions between the two membrane layers.

At 40℃, the concentration of the supplied ethanol aqueous solution is
The permeation rate at 16.1, 45.1, 62.9, 89.1% is
1.36, 1.00, 0.86, 0.75 Kg/m ² ·hr, and the separation coefficient α was 3.6, 6.4, 5.4, 4.9.

Example 8 Between two crosslinkable polyvinyl alcohol films,
A separation membrane was prepared by loading 0.123 g of poly(allylammonium chloride). The weight of the polymer ion salt per membrane area is 9.8 mg/cm ² . Separation experiments were conducted using pervaporation at 40°C, and the results shown below were obtained.

The concentration of the supplied ethanol aqueous solution is 16.5,
When 44.2, 65.1, 86.8%, the permeation rate is 1.13,
0.693, 0.287, 0.02Kg/m ²・hr, and the separation coefficient α of water for ethanol at this time is 18.4,
They were 18.3, 57.4, and 175.6.

Example 9 Using a composite membrane in which 5.46 mg/cm ² of poly(allylammonium chloride) was loaded between the polyvinyl alcohol membranes, water-alcohol separation by pervaporation at 40°C was attempted, and the following results were obtained.

The concentration of the supplied ethanol aqueous solution is 15.3,
When 43.3, 65.8, 85.3%, the permeation rate is 1.10,
0.82, 0.30, 0.05Kg/ ^m2・hr, and the separation coefficient α of water for ethanol is 24.1, 29.2, 47.7,
It was 48.4.

Comparative Example 2 Two polyvinyl alcohol membranes were stacked on top of each other and water-ethanol separation was performed by pervaporation.

At 40℃, the concentration of the supplied ethanol aqueous solution is
At 16.2, 43.6, 65.1, 86.8%, the permeation rate is
0.81, 0.53, 0.26, 0.05Kg/ ^m2・hr, and the separation coefficient α of water for ethanol is 10.6,
They were 14.7, 21.7, and 29.6.

[Brief explanation of drawings]

The drawing is a schematic diagram of a separation membrane used in the present invention. 1 indicates an ultrafiltration membrane, and 2 indicates a layer of polymeric ionic salt.

Claims (1)

[Claims] 1 A mixture of water and alcohol is applied to a composite membrane in which a layer of a polymer ion salt selected from polymers of organic ammonium salts and organic sulfonates having ethylene bonds is provided between two ultrafiltration membranes. A method for concentrating alcohol, characterized by passing it through.