JPS6328409A - Concentration of alcohol aqueous solution by pervaporation - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for concentrating an aqueous alcohol solution using a semipermeable membrane. The invention also relates to the use of cellulose derivative membranes for concentrating aqueous alcohol solutions.

The use of synthetic membranes for separation and purification purposes is a rapidly evolving field of technology. The technology using this synthetic membrane is
It can be applied, for example, to waste water treatment, chemical industry, food industry and pharmaceutical industry for various separation and purification purposes. Traditional separation methods such as distillation and crystallization
Although this requires a large amount of energy, membrane-based technology can accomplish this with significantly lower energy consumption.

(Prior Art) Membrane-based separation methods currently used industrially include dialysis, reverse osmosis, and electrodialysis, which are used in the production of sweet wood, desalination from seawater, and separation of proteins and other biological substances. Used for purification.

'ゞ-Baboration (pervaporation)
) is a method in which the liquid mixture to be treated is brought into contact with a semipermeable membrane. The permeate dissolves in the membrane, diffuses through the membrane, and evaporates on the other side of the membrane in vacuum or inert gas. The semipermeable membrane acts like a thin solvent extraction layer that is continuously regenerated as permeable molecules evaporate from the underside of the membrane.

Pervaporation is more desirable than other methods for certain applications. Pervaporation is used, for example, as a separation and C-condensation method for treating azeotropic solutions, i.e. mixtures of substances whose components have very close boiling points, mixtures of isomers, and mixtures of heat-sensitive substances. be.

OBJECTS OF THE INVENTION The present invention relates to concentrating aqueous alcohol solutions by pervaporation techniques. Two important factors to consider when determining the suitability of a method and a semipermeable membrane for use in this method are the selectivity, i.e., the degree of final concentration desired and the membrane's throughput, which will dictate the throughput. It is the amount of permeate that passes through. Cellulose derivatives such as cellulose acetate, cellulose triacetate and regenerated cellulose were tested according to conventional membrane separation methods to concentrate aqueous alcohol solutions by pervaporation techniques. However, according to such tests, although considerable selectivity was obtained in some cases, the permeability of each membrane was low and it was therefore not possible to find a usable alcohol concentration method. .

As taught by the present invention, unexpectedly, certain novel cellulose-based membranes have superior selectivity and membrane permeability compared to conventional cellulose-based membranes, and in particular can be used in aqueous alcohol solutions by pervaporation techniques. It has been found that this is desirable for iQ reduction.

(Structure of the Invention) Accordingly, the present invention provides for directing an alcohol solution to one side of a semipermeable cellulose derivative membrane provided in an enclosed area,
Next, in the method for concentrating an aqueous alcohol solution by diffusing through the membrane and taking out the evaporated permeate with a changed alcohol concentration from the other side, the alcohol is characterized in that a cellulose carbamate membrane is used instead of the cellulose derivative membrane. This relates to a method of concentrating an aqueous solution. The present invention also relates to the use of cellulose carbamate in concentrating aqueous alcohol solutions using pervaporation techniques.

(Functions and Effects) Cellulose carbamate is a compound produced by reacting cellulose with isocyanic acid. Furthermore, isocyanic acid is produced, for example, when urea is decomposed at high temperatures, and therefore cellulose carbamate can be produced by mixing cellulose and urea together and heating this mixture. Examples of the production of cellulose carbamates are disclosed, for example, in Finnish patents 61033, 62318 and 64062.

Desirable pervaporation membranes used in concentrating alcohol can be made by dissolving cellulose carbamates.

That is, pervaporation membranes are manufactured by dissolving carbamates in an aqueous sodium hydroxide solution, then shaping this solution into a membrane and contacting it with a precipitating liquid, thereby precipitating cellulose carbamates as a membrane. be able to.

The cellulose carbamate is one that is soluble in an aqueous sodium hydroxide solution containing at least 5% coulomer. appropriate N
The aOH content is, for example, 8 to 10%. The cellulose carbamate melon to be dissolved needs to be chosen such that the viscosity of the solution is appropriate for the technology used in producing the membrane. A suitable amount of cellulose carbamate in practice is usually in the range of 1 to 10% by weight;
Preferably it is within the range of 5-9% by weight. As the carbamate content increases, the viscosity of the solution increases rapidly, thus making membrane production difficult.

An aqueous solution of acid is required to precipitate the cellulose carbamate from the NaOH solution. Suitable acids are strong acids such as sulfuric acid. Suitable sulfuric acid content is usually about 10% by weight
It is. Furthermore, the precipitation solution can contain auxiliary substances conventionally used during precipitation, such as sodium sulfate and aluminum sulfate. Examples of precipitation techniques for cellulose carbamates and examples of formulations of the above-mentioned precipitation solutions used during precipitation can be found, for example, in Finnish Patent No. 6
No. 4603.

The method for producing membranes by precipitation techniques is to first spread a sodium hydroxide solution of cellulose carbamate in the form of a layer of desired thickness, then pass the substrate with this carbamate solution coating through the precipitation solution, thereby The process involves precipitating the carbamate in the form of a film. The membrane is removed from the substrate and cleaned. The membrane thus obtained can be used at any time as a pervaporation membrane.

In order to produce pervaporation membranes, the nitrogen content must be 0. It is advantageous to use 2-2.1% cellulose carbamate.

In pervaporation technology, the thickness of the membrane is not per se important due to the nature of its application. However, in practice, of course, there are certain limitations due to various factors. The practical lower limit for the membrane thickness is determined inter alia by the mechanical resistance.

Furthermore, a certain vacuum is required at the side where the permeate evaporates, thus making it difficult to achieve sufficient vacuum if the membrane thickness is inadequate.

In practice, suitable membrane thicknesses have been found to be between 10 and 50 microns, preferably between 15 and 40 microns.

The present invention can be applied to the case of concentrating various alcohols from an aqueous alcohol solution. The invention particularly relates to the separation or concentration of methanol, ethanol, butanol and phenol.

(Examples) Next, the present invention will be described in detail according to examples and drawings. The drawings below schematically show an apparatus for concentrating alcohol by the pervaporation technique taught by the present invention.

In the illustrated apparatus 10, a container 12 contains the alcohol/water mixture to be treated and is placed within the hot melt 11. The pump 13 is an enclosed membrane cell 14
The cell is divided into two chambers 1 by a cellulose carbamate membrane 20.
It is divided into 4a and 14b. The membrane 20 is supported by a mesh (not shown), for example a wire mesh. The alcohol solution returns to the container 12 from the small chamber 14a. The lower the alcohol content of the permeate is than the alcohol content of the feed solution, the higher the alcohol content in the solution returning from chamber 14a.

The permeate passes through the membrane 2 from the alcohol solution in the small chamber 14H.
0 and diffuses through this membrane into chamber 14b.

A vacuum state is maintained in the small chamber 14a. The permeate diffused through the membrane 20 evaporates from the surface of the membrane 20 and this vapor is extracted by the vacuum pump 16 and transferred to the cold trap 1.
Sent to 5.

The permeate that diffuses through membrane 20 and evaporates from the surface of the membrane can also be collected by introducing a suitable inert gas, such as nitrogen, into chamber 14b and then separating the permeate from this gas. Reference numeral 17 in the drawings indicates a mercury pressure gauge, reference numeral 18 represents a valve for removing the feed sample, and reference numeral 19 switches the flow of the sample so that it flows into and out of the cold trap 15. It is a three-way valve.

Cellulose carbamate used in these tests was prepared as follows.

Spruce sulfite cellulose with DP800 [
Lau? (Rauma) RF was irradiated in a sheet form with a total irradiation of 1.0 Mrad (electrical acceleration method).

After irradiation, the cellulose contained [)P446.

The mate was then impregnated in a solution containing 15% by weight urea and 85% by weight aqueous ammonia (70% NH3 and 30% H20). This impregnation was carried out at -20°C and the impregnation time was 5 minutes. After that, apply the impregnating solution 2. 15
It was released from the sheet at a pressure of kg/cj. At this time, the cellulose contained 27.2% urea.

The impregnated sheet was heated between hot plates in a press for 1.5 minutes at 220°C. The nitrogen content of the cellulose carbamate thus obtained was 2010% and the cellulose carbamate had a DP of 420.

The separation coefficient of the membrane was calculated using the following formula.

aB, A-YB/YA XB/XA In the formula, YB, YA - components A and B'd in the permeate: 1
Degrees XA, XB - Concentration of components A and B in the feed solution For example, when αB,A>1, the concentration of component B in the permeate is higher than the respective component concentration of the feed solution. Therefore, the membrane has a high degree of separation of substance B.

Example 1 Cellulose carbamate films A, B, and C were IV prepared by dissolving 7% by weight, 8% by weight, and 9% by weight of the above cellulose carbamate in an 8% NaOH aqueous solution. The solutions thus obtained were 3.9.6.2 and 13.1p
Each had a viscosity of as. A membrane was created by spreading cellulose carbamate on a glass plate using a glass rod to form a uniform tank. The thickness of the membrane in each case was made equal with a layer of adhesive tape wrapped around a glass rod.

The membrane was precipitated by immersing the glass plate in a precipitation solution containing 10% by weight H2SO4, 18% by weight Na2SO4 and 7% by weight Al2(SO4)3. In this case, the temperature of the precipitation solution was 23°C. Precipitation time was 3 minutes.

After precipitation, the membrane was removed from the glass plate and soaked in warm running water (30 min.
~40'C) and left in water overnight.

Thereafter, the membrane was treated with 20% ethanol for 30 minutes to enhance its shelf life. The membrane thicknesses were 26.1 microns, 19.9 microns and 20.7 microns dry.

Using the above membrane, a 94% ethanol solution was concentrated and produced in an apparatus as shown in FIG.

The temperature of the feed solution was kept at 25°C, and the flow rate of the feed solution was 1800 ml/min. The pressure on the permeate side was 12 mbar. The system in this apparatus was stabilized for 2 hours before the Al11 injection. In the experiment, Sample I was collected for 15 minutes, after which the weight of the permeate obtained from the cold trap was determined to determine the flow value.
s) was calculated. The permeate was also analyzed to determine the separation factor.

The flow values representing the water separation coefficient and permeability of each membrane are as follows.

Feed ethanol Permeated ethanol Separation coefficient Flow value U) (wt%) (wt 96)
(Q IIzO) (mg/m'/sec) Membrane A 90.2 go, 8
2.2 523 membrane 8 92.2
87.3 1.7 554 membrane C92,
279,53,0376 Example 2 The method of Example 1 was repeated using membranes A and B, except that the feed solution was a dilute ethanol solution. As a result, the following results were obtained.

Feed ethanol Permeated ethanol Separation factor Flow value (J) (wt%) (wt%)
(α1110) (mg/m/sec) Seki A
19.1' 15.1
1.3 368 MoB 19.5
1B, 5 1.2 3
88 These results indicate that the selectivity and flow values for water are lower than when processing concentrated alcohol solutions.

Example 3 As in Example 1, membranes were used to concentrate methanol, ethanol, butanol and phenol solutions.

The results are as follows.

Methanol 113 12.8
1.5 288 ethanol 20.0
9.2 2.5 2
77 Butanol 48.8 7.
4 11.9 319 Phenol 1.0 0.8 1.2
459

[Brief explanation of drawings]

The drawing schematically shows an installation for concentrating alcohol by pervaporation technology according to the invention. １０・・・・・・・Device １２・・・・・・・・・
...Container 14...Cell 20...
・・・・・・Membrane and 1 other person・Preface to drawings (no change in content) Procedural formalism (method) 1゜Indication of incident 1985 Special S'F * No. 118065
No. 2, Name of the invention 'tA of alcohol aqueous solution by pervaporation
Reduction method 3, relationship with the case of the person making the amendment Patent applicant name: Neste O.Y. 4, agent address: 1-1 Minami-Aoyama-chome, Minato-ku, Tokyo (shipment date)
7, July 28, 1988, Contents of the Amendment") Mingai! The drawing written in the seventh line from the bottom of page 15 is amended to read "Figure 1 is". (2) Figure 1 will be corrected as shown in the attached sheet. that's all

Claims (4)

[Claims] (1) directing an alcohol solution to one side of a semipermeable cellulose derivative membrane disposed within an enclosed area, and then directing the evaporated permeate, which has diffused through the membrane and has a varying alcohol concentration, from the other side of the membrane; 1. A method for concentrating an aqueous alcohol solution by removing it, the method comprising using a cellulose carbamate membrane instead of a cellulose derivative membrane. 2. A method according to claim 1, characterized in that the cellulose carbamate film is produced from cellulose carbamate having a nitrogen content of 0.2 to 201%. (3) A method according to claim 1 or 2, characterized in that the cellulose carbamate film has a thickness of 10 to 50 microns, preferably 15 to 40 microns. (4) Use of cellulose carbamate membranes to concentrate alcohol aqueous solutions using pervaporation technology.