JPH072207B2 - Alcohol concentration method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for concentrating alcohol by separating and removing water using a selectively permeable membrane.

[Conventional technology]

Conventionally, as a method for concentrating alcohol, the first is a distillation method, the second is an extraction method in which sodium hydroxide is added to tert-butyl alcohol, and the third is the recently developed selective permeation of water vapor or alcohol. There is a method of selectively permeating and removing only water vapor or alcohol through the membrane.

[Problems to be solved by the invention]

In the case of the first distillation method above, ethanol-water system, tert-
In the butyl alcohol-water system, there is an azeotropic point, and ethanol cannot be concentrated above 95.5% by weight and tert-butyl alcohol above 87.5% by weight. To concentrate to a concentration higher than that at the azeotropic point, add benzene as a third component and distill it. The benzene-water-ethanol ternary azeotrope distills from the top at 64.85 ° C. If the conditions are properly selected, nearly 100% of anhydrous alcohol can be obtained from the bottom of the column, but azeotropic distillation cannot be applied to a system such as food industry where benzene is contained and it is not preferable to contain benzene.

In the extraction method in which the second sodium hydroxide is added, foreign matter (sodium hydroxide) is mixed, which is not preferable.

In the third method using a selectively permeable membrane for water vapor or alcohol, the pervaporative membrane having selective permeability for ethanol has a separation coefficient α = 25 and a permeation flux of alcohol Q≈0.05 kg / m ²
・ Only a film of about h was obtained (Abstracts of Papers Presented at the 19th Autumn Meeting of the Chemical Engineering Society of Japan, P239, 1985). Moreover, since it is an organic film, it has heat resistance at 80 ° C or higher and under high pressure. Then there is a problem in terms of durability. It should be noted that there is no example of ethanol separation using an inorganic membrane.

Therefore, the present invention provides a method capable of concentrating to a higher concentration than that at the azeotropic point, without inclusion of foreign matter, and capable of efficiently separating and concentrating alcohol even under high temperature and high pressure. .

[Means for solving problems]

The inventors of the present invention have made extensive studies in order to solve the above-mentioned problems, and as a result, an inorganic porous film having a pore diameter of 10 Å or less (especially an alumina-based film) was compared with an alcohol-water mixture. Has a property of selectively permeating only water and hardly permeating alcohol, and by using this membrane, it is possible to concentrate at a higher concentration than at the azeotropic point, and there is no contamination of by-products or foreign substances. Moreover, they have found that they have heat resistance and pressure resistance unlike organic films, and have developed the present invention.

That is, the present invention, a gas or liquid containing alcohol and water is supplied to one side of the membrane surface of the alumina-based inorganic porous membrane having a pore diameter of 10 Å or less, and the other side is relatively lower in pressure than the gas or liquid supply side. The method for concentrating alcohol is characterized in that water is removed by permeating the membrane surface as described above.

An example of the method for producing an alumina-based inorganic porous membrane having a pore size of 10 Å or less used in the present invention is as follows. After coating alumina sol obtained by hydrolyzing aluminum isopropoxide, for example, on the surface of a porous substrate (pore diameter 1.5 μm), impregnating aluminum isopropoxide dissolved in an organic solvent (Daiflon), and in water vapor Manufactured by hydrolysis.

In order to remove water from a gas containing alcohol and water by the method of the present invention using this membrane, a normal pressure or high pressure gas containing alcohol and water is passed through the feed side of this porous membrane, Reduced pressure (vacuum) on permeate side of porous membrane
Alternatively, if the pressure is normal and a pressure difference is generated on both sides of the membrane (the pressure on the permeate side is relatively low on the field side), water can be permeated. Therefore, if a high-pressure gas is passed through the porous membrane feed side and the permeate side is depressurized, the pressure difference between both sides of the membrane becomes larger and the permeation efficiency can be improved. It is also possible to accelerate the permeation of water by heating the permeate side of the membrane.

In the present invention, when removing water from a liquid containing alcohol and water, by pervaporation, that is, by dipping the feed side of the porous membrane in a liquid containing alcohol and water to reduce the pressure on the permeate side, Can be permeated through the membrane.

[Action]

The operation of the present invention will be described with reference to FIG. The porous membrane in the present invention comprises a porous ceramic 1 on the surface of which a porous membrane 2 of alumina having a thickness of about 10 μm and a fine pore diameter is carried. The condensable gas in the raw material gas 4 condenses in the pores of the thin film 2 through the gas boundary film 3 to become a liquid 6, which closes the pores of the thin film 2, and the non-condensable gas 5 permeates the thin film 2. You cannot do it. Therefore, for example, the other side of the thin film 2 is evacuated and sucked to vaporize the condensate 6, and only the vaporized condensed gas 7 permeates the thin film 2.

〔Example〕

FIG. 2 is a diagram showing an apparatus for investigating the characteristics of the porous membranes used in Examples 1 to 4 described below. An alcohol aqueous solution having an arbitrary composition is put in the evaporator 8 and heated to generate a mixed gas of alcohol and water vapor, which is pressurized by the compressor 9, the mixed gas is heated to an arbitrary temperature by the heater 10, and then the membrane module 11 is used. Introduce to. One of the membranes is suctioned by the vacuum pump 12.

FIG. 3 shows an outline of the above-mentioned membrane module. In FIG. 3, the raw material gas 4 passes through the ceramic pipe and becomes an unpermeated gas 13 having a very small amount of condensable components and a gas 14 occupying most of the condensable components. Used for the purpose of suction. Diameter 1 cm x 1
A large number of ceramic pipes 15 for condensable separation membranes having a length of 00 cm are installed in the separator, and the ends are fixed to the end plate of the separator and an adhesive 16.

FIG. 4 is a sectional view of this separator, in which the ceramic pipe 15 is built.

Example 1 Using the apparatus shown in FIG. ² , a module 11 was assembled with a membrane area of 0.97 m ² and a concentration test in a methanol-water system was conducted. The inlet pressure of the module 11 is about 1 atm, the temperature is about 60 ° C, and the vacuum side is
It was set to 5 Torr 20 ° C.

The results are shown in FIGS. 5 (a) and 5 (b). Figure 5 (a) shows
The vertical axis represents the weight fraction of methanol in the gas phase, which represents the gas composition at the inlet of the membrane module, and the horizontal axis represents the weight fraction of methanol in the membrane permeation gas. In FIG. 5 (a), A-1 indicates the experimental result, and A-2 indicates the equilibrium curve. FIG. 5 (b) shows the permeation flux of methanol (A-3) and the permeation flux of water (A-4) with respect to the methanol weight fraction in the gas phase (membrane module inlet gas composition).

Example 2 Using the apparatus shown in FIG. ² , a module 11 was assembled with a membrane area of 1.2 m ² and a concentration test in a methanol-water system was conducted. The inlet pressure of the module 11 is about 5 atm (4 kg / cm ² G) and the temperature is about 60 ° C, the vacuum pump is not operated, and the permeated gas side is about 1 atm.
m, at 20 ℃.

The results are shown in FIGS. 6 (a) and 6 (b). FIG. 6 (a),
The symbols in (b) have the same meanings as in FIGS. 5 (a) and 5 (b), B-1 and B-2 show the experimental results and the equilibrium curve, and B-3 and B-4 show Represents the permeation flux of methanol and water, respectively.

Example 3 Using the apparatus shown in FIG. ² , a module 11 was assembled with a membrane area of 0.77 m ² and a concentration test was conducted in an ethanol-water system. Module 11 inlet pressure is about 3 atm (2 kg / cm ² G) and temperature is about 60 ° C.
The vacuum side was 20 Torr and 20 ° C.

The results are shown in FIGS. 7 (a) and 7 (b). FIG. 7 (a),
The meanings of the symbols in (b) are the same as in FIGS. 5 (a) and (b), C-1 and C-2 show the experimental results and the equilibrium curve, and C-3 and C-4 show Represents the permeation flux of ethanol and water, respectively.

Example 4 Using the apparatus shown in FIG. ² , a module 11 was assembled with a membrane area of 0.75 m ² and a concentration test was conducted in an isopropyl alcohol-water system. The inlet pressure of module 11 is about 3 atm (2 kg / cm
² G), the temperature was about 60 ° C, and the vacuum side was 10 Torr and 50 ° C.

The results are shown in FIGS. 8 (a) and 8 (b). FIG. 8 (a),
The meanings of the symbols in (b) are the same as those in FIGS. 5 (a) and (b), D-1 and D-2 show the experimental results and the equilibrium curve, and D-3 and D-4 show Represents the permeation flux of isopropyl alcohol and water, respectively.

Example 5 In Examples 1 to 4, the water-alcohol gas separation was examined, but in this Example, the pervaporation was performed by immersing the module in a liquid for separation. As shown in FIG. 9, the membrane module was added to the aqueous t-butanol solution 17.
11 was dipped and suctioned with a vacuum pump 12 via a drain port 18.

The liquid temperature of the t-butanol aqueous solution 17 was set to 80 ° C, and 0.97
A concentration test was carried out in a t-butanol-water system by immersing m ² of module 11. The vacuum side was 5 Torr and 20 ° C.

The results are shown in FIGS. 10 (a) and 10 (b). Figure 10 (a),
The meanings of the symbols in (b) are the same as those in FIGS. 5 (a) and (b), E-1 and E-2 show the experimental results and the equilibrium curve, and E-3 and E-4 are Represents the permeation fluxes of t-butanol and water, respectively.

〔The invention's effect〕

According to the present invention, the concentration can be increased to a higher concentration than that at the azeotropic point without adding a third component other than alcohol and water. Therefore, the present invention is also useful as an alcohol concentration method for the food industry.

Further, the porous membrane used in the present invention is excellent in strength because it is an inorganic substance, and has heat resistance up to about 300 ° C., 30 kg / cm ²
Since it has pressure resistance up to a certain degree and the pore diameter of the porous membrane is fine, the separation coefficient is high and the water can be removed with a high permeation flux to separate and concentrate the alcohol.

[Brief description of drawings]

FIG. 1 is a diagram showing the principle of membrane separation according to the present invention, FIG. 2 is a diagram showing a flow of an apparatus used for performing a gas separation test according to the present invention, FIG. 3 is a schematic view of a membrane module, and FIG. FIG. 4 is a sectional view of FIG. FIGS. 5, 6, 7, and 8 are charts showing the results of the examples using the test apparatus of FIG.
Fig. 6 shows methanol-water system, Fig. 7 shows ethanol-water system,
FIG. 8 shows the case of isopropyl alcohol-water system.
FIG. 9 is a diagram showing a flow of an apparatus used for conducting a test by the pervaporation in the present invention, and FIG. 10 is a chart showing a result of an example using the test apparatus of FIG. -Butanol-water system separation result.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display area C07C 31/10 9159-4H 31/12 9159-4H

Claims (1)

[Claims] 1. A gas or liquid containing alcohol and water is supplied to one side of a membrane surface of an alumina-based inorganic porous membrane having a pore diameter of 10 Å or less, and the other side is relatively lower in pressure than the gas or liquid supply side. A method for concentrating alcohol, characterized in that the water is removed by permeating the membrane surface as described above.