JPH04200729A - Control of pore diameter of inorganic permeation film - Google Patents

Abstract

PURPOSE:To control the pore diameter of a synthetic zeolite film by controlling a gelled material solution used for the formation of a zeolite crystal in a film form in a fine through pore passage of porous glass and synthesis conditions. CONSTITUTION:An ortho silicate ester or its diluted solution is supplied to a fine through pore passage of a porous silicic acid product and the solute component is condensed in the fine pore passage. Next, barium as one of alkaline earth metals in which zeolite hardly forms the crystals or an organic basic compd. e.g. tetrathylammonium together with an aqueous solution of Al compd. as a gelling material solution are supplied to a porous glass in the fine through pore wherein said solute component is condensed. Subsequently, a silica alumina hydrate gel is produced in the fine pore passage. Further, the one end of the porous silicic product pore passage which carries the silica alumina hydrate gel is allowed to come into contact with an aqueous diluted alkali solution, while the other end of the porous silicic product pore passage is allowed to come into contact with air or a reaction-inert gas. Through this process, a hydro-thermal reaction is permitted to stabilize the silica alumina hydrate gel.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to forming a zeolite film in the microscopic pores of a porous glass, and also to forming a gelling raw material solution when forming zeolite crystals. This invention relates to a method for efficiently producing a molecular sieving selectively permeable membrane by controlling the pore size of a synthetic zeolite membrane by controlling the synthesis conditions.

[Conventional techniques and problems to be solved by the invention] The pore diameter of the zeolite membranes synthesized so far is constant;
The various molecular sieving functions that zeolite is supposed to have have not been discovered at a practical level.

[Means for Solving the Problems] Based on Japanese Patent Application No. 110343/1988 (Publication of Patent Application No. 281106/1999), the present inventors have obtained a zeolite membrane that discovers the inherent characteristics of zeolite. Hopefully,
As a result of extensive research, we have developed an orthosilicate ester in the form of a homogeneous solution that can easily and homogeneously enter the fine pores of porous glass as a raw material for a support and as a raw material for a through-hole path shielding material. Alternatively, a diluted solution of orthosilicate ester is supplied, the solute component is concentrated in the pores, and an aluminum compound and alkaline earth are added as a gelling raw material solution to the porous glass in which the solute component is concentrated in the pores. By supplying an aqueous solution of an organic basic compound such as vanium or tetraethylammonium, which is difficult to synthesize as zeolite crystals in metal (to control the pore diameter of the zeolite membrane formed by these substances), silica is added to the pore channels. Alumina hydrated gel is produced. The hydrated silica alumina gel is coated with sufficient density and homogeneity so that the substance that ultimately has a molecular sieving function shields the micropore channels to a practical level (hereinafter the shielded area is collectively referred to as the active layer). It becomes possible to form and fill micropore channels. Furthermore, one end of the porous glass pore channel carrying the silica alumina hydrated gel is in contact with water or a dilute alkaline aqueous solution, and the other end is in contact with air or a gas inert to the reaction, and a hydrothermal reaction is carried out. By treatment and stabilization, we were able to obtain a separation membrane that exhibits separation performance and permeation rate at a practical level. The present invention was completed based on this knowledge.

That is, the present invention provides the following steps: (A) Supplying an orthosilicate ester or a diluted solution of an orthosilicate into the microscopic pores of a porous silicic acid body; (B) Concentrating a solute component within the pores: (C) A porous glass in which the solute component is concentrated in the pores, and an organic base such as barium, which is difficult to synthesize as zeolite crystals, or tetraethylammonium, in an aluminum compound and an alkaline earth metal as a gelling raw material solution. By supplying an aqueous solution of the compound, a hydrated silica-alumina gel is generated within the pore channels.

(D) One end of the porous glass pore channel supporting silica alumina hydrated gel is exposed to dilute alkaline aqueous solution, while the other end is exposed to air or a gas inert to the reaction. The present invention provides a method for controlling the pore size of an inorganic permeable membrane by stabilizing a hydrated silica-alumina gel by carrying out a thermal reaction.

The porous glass used in the present invention must have through-pore channels. It can be freely selected from among those made using the glass phase separation phenomenon typified by porous glass, those made by the sol-gel method, and those made by sintering glass powder. Its shape may be any of plate-like, tubular and hollow fiber-like.

In addition, porous glass may be formed into these shapes by itself, or may be formed on the surface of a porous support such as porous ceramics or porous metal sintered body that has been previously formed into these shapes. , it may be in the form of a so-called porous composite. Further, these porous materials may be subjected to chemical treatment or heat treatment in advance, if desired.

In order to control the pore diameter of the inorganic permeable membrane according to the present invention, orthosilicate ester is first supplied as a silica source into the fine through pores of porous glass.

These silica sources are also free to be diluted in a suitable solvent. Solvent 1 in this case is a solution compound that sufficiently dissolves the orthosilicate ester to the required concentration, is inert in the subsequent gelation reaction and hydrothermal reaction, and has a vapor pressure sufficiently higher than that of the silica source. selected from.

Examples of lower alcohols include methanol, ethanol, propatool or tert-butanol.
Species or mixtures of two or more species are readily utilized.

The concentration of the silica source solution depends on the density of the hydrated gel to be formed, the desired film thickness, the vapor pressure of the silica source/solvent, the pore size of the porous glass used, or the embodiment used in the subsequent concentration step. It is necessary to select appropriately. 1.4jL
It can be widely used in the range of ppm-100.0% by weight, but regarding the upper limit, it is preferable to ultimately eliminate obstacles other than the active layer within the support pores of the inorganic permeable membrane. ). For this purpose, the concentration is preferably as low as possible, and even if the concentration is 10.0% by weight or less, the purpose can be sufficiently achieved.

It is generally supplied by coating, dipping, or suction, but the pore-entangled end of the porous glass, where the active layer is intended to be formed, is brought into contact with silicate ester vapor under vacuum or normal pressure. A vapor deposition method or a condensation method for adhesion, deposition or condensation can also be employed.

The supply temperature and time of the silica source in these methods take into consideration the pore diameter of the porous glass, the intended pore passage blocking rate, the concentration of the silica source when used as a diluted solution, the vapor pressure ratio of the silica source and the solvent, etc. and select. Although not particularly limited, the molecular objectives can usually be achieved at room temperature and for about 5 to 30 minutes, respectively.

The porous glass, which has been supplied with a silica source, then concentrates the solute components within its pore channels. Concentrating here means not only removing the solvent, but also concentrating the silica source, which is a solute component, at the intended location within the pore passages as densely as possible.

The optimal suction temperature, pressure, and time in the concentration step are controlled by the pore diameter and wall thickness of the porous glass used, the type of silica source and diluting solvent, and their vapor pressure ratio. 0-100℃, O-750 respectively
The range of mmHg and 1-60 minutes can be used as a rough guide, but the purpose is to form a high-density zone of silica source at the point where the active layer is intended to be formed in the pore channel, and the final product. It is preferable to set it after understanding the relationship with separation performance.

Next, barium, which is difficult to synthesize as zeolite crystals, or barium, which is difficult to synthesize as zeolite crystals, is added to the alkaline earth metal as a gelling raw material solution in order to control the pore size. An aqueous solution of an organic base compound such as tetraethylammonium and an aluminum compound is supplied to form a hydrated silica alumina gel within the pore channels. Here, the alkaline earth metal compound refers to one or a mixture of two or more water-soluble alkaline earth metal compounds such as alkaline earth metal chloride compounds, alkaline earth metal hydroxides, and their salts. To tell. "Organic basic compound" refers to an organic nitrogen-containing cation or an organic nitrogen-containing cation source. The aluminum compound means one type or a mixture of two or more types selected from water-soluble aluminum compounds such as sodium aluminate, aluminum hydroxide, and salts thereof.

By supplying these various gelling raw material solutions, various molecular sieving functions inherent in zeolite can be discovered on a practical level.

In addition, when supplying the gelling raw material solution onto the porous glass after the silica source has been concentrated in the pores, the surface where the pore entwined ends intended to form the active layer are exposed is used as the gelling raw material. This is achieved by immersion or contact, creating a vacuum at the end of the pore alley, and suctioning.

The suction pressure is selected in the range from 0 to 750 mmHg, but 20 mmHg is usually easy to operate, easily achievable with an aspirator or vacuum pump.

The supply temperature of the gelling raw material solution is preferably selected from a temperature range in which the crystallization reaction does not proceed. Usually around room temperature (
The purpose can be fully achieved at a temperature of 15 to 40°C.

The supply time of the gelling raw material solution is preferably the time required for the silicic acid ester concentrated and supported on the porous glass to completely disappear by completion of the gelling reaction and scattering. Specifically, the time period is selected from a range of about 5 minutes to about 50 hours.

The porous glass, in which the formation of the silica alumina hydrated gel has been completed and the unreacted orthosilicate ester has been completely removed by completion of the reaction or by scattering, is then subjected to a hydrothermal reaction.

The hydrothermal reaction is carried out while one end of the porous glass channel is in contact with water or a dilute alkaline aqueous solution, and the other end is in contact with air or a gas inert to the reaction. The purpose of this step is to stabilize a portion of the silica-alumina hydrated gel supported within the pore channels, while controlling the pore size of the zeolite crystals that grow into crystallization. For example, if the crystallization reaction solution is NaOH/NaA10. , BaQ2/Al(OH),,
It can be seen that in the case of (gradient, NI/ni(OH)), the pore diameter of the synthetic zeolite membrane is 4.2, 2, and 3.2 to 4.2.

When forming the active layer on one of the pore-entangled ends, it is preferable that the surface where the pore and the intertwined end where the active layer is intended to be formed is exposed is brought into contact with the gas phase.

The purpose of the gas phase is to maintain or concentrate the alkali concentration suitable for stabilizing the silica-alumina hydrated gel in the pores in contact with it or in the pores in its vicinity, and the gas phase is usually air. However, if it is desired to avoid the presence of a high concentration of oxygen for safety reasons, dilution or substitution with a gas inert to the reaction, such as nitrogen, helium, and argon, may be performed.

The reaction temperature is selected according to the reaction conditions for synthesizing various heptaolides. Usually 60-240℃, preferably 80-19℃
The temperature is selected from the range of 0°C depending on the composition of the silica alumina hydrated gel formed in the pores of the porous glass in the previous step.

The reaction time varies depending on the type of stabilized silica alumina intended to be formed, but is usually selected from the range of 0.1 to 1000 hours, preferably 1 to 100 hours.

The pressure of the gas phase may be slightly increased pressure, atmospheric pressure, or reduced pressure, but even in the case of reduced pressure, an absolute pressure of 20 to 760 mmHg, which can be achieved with an aspirator, is sufficient. This reduced pressure state may be maintained throughout the reaction time, or may be maintained only at the initial stage.

The porous glass element that has completed the reaction in this manner is put into practical use after being cooled down and washed with water.

The performance of the completed inorganic permeable membrane was evaluated by measuring the permeation rate and permeate fluid composition when a permeation test was conducted to check the water solubility of water-soluble alcohol using the pervaporation method, as a method to comprehensively understand the performance of the entire membrane surface. Confirmed by measurement.

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

Example 1 First, a porous glass element was produced by the following method.

Vycor J17930, a porous glass product (
Cut a 100 mm length from a tube (outer diameter 10 mm φ), and as shown in Figure 1, one end has a cross section of a 10 mm 915 US 304 tube, and the other end has a 10 mm length with one end sealed by heat melting.
The cross sections of the glass tubes were joined together, solidified with a commercially available epoxy resin so as not to form any voids, and these joints were further covered with a heat-shrinkable Teflon tube to produce a porous material element.

At the same time, 1000 CC of each of a silica source solution and a gelling raw material solution having the following compositions were prepared, and a portion of each was transferred into a test tube with an inner diameter of 25 mm and a length of 300 mm and kept at room temperature.

Silica source solution composition: 500 wt Ppm methanol solution of ethyl orthosilicate Gelation raw material solution composition: Sodium aluminate 1.72X10”M caustic soda
The silica source solution was supplied onto the mixed aqueous solution porous glass element of 6.25×10′ by the following operation. First, a porous glass element was set in a suction bottle. The large mouth of the suction bottle was closed with a rubber stopper passed through the center of the dense stainless steel tube section of the porous glass element. Thereafter, the porous glass outer wall portion of the porous glass element was immersed in the silica source solution and maintained for 3 minutes. At this time, the inner wall of the porous glass element sealed inside the suction bottle was heated to 20 mmHg.
The pressure was maintained at .

The step of supplying the gelling raw material solution was started by immersing the porous glass outer wall portion of the porous glass element in the gelling raw material solution and simultaneously reducing the pressure inside the element tube to 20 mmHg.

After 24 hours, the porous glass element was pulled out of the gelling raw material solution and assembled into a module of the type shown in FIG. 2, which was made using a SUS 304 tube with a nominal diameter of 1/2 inch as a shell. The space between the porous outer wall of the element and the inner wall of the module shell was filled with a crystallization reaction solution prepared by diluting a fresh gelling raw material solution ten times with ion-exchanged water. The inner wall of the porous glass element was left open to atmospheric pressure. A ribbon heater is wrapped around the outer wall of the module shell, and the temperature inside the module can be raised by applying voltage. Shell outer wall 3
The temperature was started to increase at a rate of 140°C/min, and after reaching 140°C, the temperature was stopped and maintained at 140±10°C.

After stopping the temperature increase, the temperature started to decrease 2 hours later. After the inside of the module reached room temperature, the element was taken out and kept immersed in a large amount of ion-exchanged water for 24 hours to obtain an inorganic permeable membrane.

The pore diameter of the inorganic permeable membrane thus obtained was 4.2
It is eight.

Example 2 A porous glass element was produced in the same manner as in Example 1.

At the same time, 1000 CC of each of a silica source solution and a gelling raw material solution having the following compositions were prepared, and a portion of each was transferred into a test tube with an inner diameter of 25 mm and a length of 300 mm and kept at room temperature.

Silica source solution composition: 500 wt ppm methanol solution of ethyl orthosilicate Gelation raw material solution composition: Mixed aqueous solution of aluminum hydroxide 4.95X1 (T to barium chloride 4.32X10°3M) Silica source solution onto a porous glass element The supply was carried out as follows: First, the porous glass element was set in a suction bottle.
The large mouth of the suction bottle was closed. Thereafter, the porous glass outer wall portion of the porous glass element was immersed in the silica source solution and maintained for 3 minutes. At this time, the inner wall of the porous glass element sealed inside the suction bottle was maintained at a reduced pressure of 20 mmHg.

The step of supplying the gelling raw material solution was started by immersing the porous glass outer wall portion of the porous glass element in the gelling raw material solution and simultaneously reducing the pressure inside the element tube to 20 mmHg.

After 24 hours, the porous glass element was pulled out of the gelling raw material solution and the nominal diameter was 1. /2 inch SUS 304
The tube was assembled into a module as shown in Figure 2, which was manufactured as a shell. The space between the outer wall of the porous glass element and the inner wall of the module shell was filled with a crystallization reaction solution prepared by diluting a fresh gelling raw material solution ten times with ion-exchanged water. The inner wall of the porous glass element was left open to atmospheric pressure. A ribbon heater is wrapped around the outer wall of the module shell, and the temperature inside the module can be raised by applying voltage. The outer wall of the shell was heated at a rate of 3°C/min, and after reaching 140'C, the temperature was stopped and maintained at 140±10°C.

After stopping the temperature increase, the temperature started to decrease 2 hours later. After the inside of the module reached room temperature, the element was taken out and kept immersed in a large amount of ion-exchanged water for 24 hours to obtain an inorganic permeable membrane.

The pore diameter of the inorganic permeable membrane thus obtained is > 4
．． It is 2A.

Example 3 A porous glass element was produced in the same manner as in Example 1.

At the same time, 1000 CC of each of a silica source solution and a gelling raw material solution having the following compositions were prepared, and a portion of each was transferred into a test tube with an inner diameter of 25 M and a length of 300 mm and kept at room temperature.

Silica source solution composition: 500 weight ppm methanol solution of ethyl orthosilicate Gelation raw material solution composition: Aluminum hydroxide 4.95X1σ3M
Tetramethylammonium iodide 4.32X10'3
The silica source solution was supplied onto the mixed aqueous solution porous glass element by the following operation. First, a porous glass element was placed in a suction bottle. A rubber plug penetrates the center of the porous glass element a@stainless steel tube part,
The large mouth of the suction bottle was closed. Thereafter, the porous glass outer wall portion of the porous glass element was immersed in the silica source solution and maintained for 3 minutes. At this time, the inner wall of the porous glass element sealed inside the suction bottle was maintained at a reduced pressure of 20 mmHg.

The step of supplying the gelling raw material solution was started by immersing the porous glass outer wall portion of the porous glass element in the gelling raw material solution and simultaneously reducing the pressure inside the element tube to 20 mmHg.

After 24 hours, the porous glass element was pulled out of the gelling raw material solution and assembled into a module of the type shown in FIG. 2, which was made using a SUS 304 tube with a nominal diameter of 1/2 inch as a shell. The space between the outer wall of the porous glass element and the inner wall of the module shell was filled with a crystallization reaction solution prepared by diluting a fresh gelling raw material solution ten times with ion-exchanged water. The inner wall of the porous glass element was left open to atmospheric pressure. A ribbon heater is wrapped around the outer wall of the module shell, and the temperature inside the module can be raised by applying voltage. Shell outer wall 3
The temperature was started to increase at a rate of 140°C/min, and after reaching 140'C, the temperature increase was stopped and maintained at 140±10°C.

Two hours after the temperature increase was stopped, the temperature was started to decrease. After the inside of the module reached room temperature, the element was taken out and kept immersed in a large amount of ion-exchanged water for 24 hours to obtain an inorganic permeable membrane.

Thus obtained 7': The pore diameter of the inorganic permeable membrane is 3
．． 2 to 4.28.

Example 4 The inorganic permeable membrane elements obtained in Examples 1 to 3 were installed in a module filled with a 90% by weight 2-propertool aqueous solution in the form shown in FIG.

Both the permeate flow side and the carrier gas cold trap are cooled with dry ice/ethanol.

As the carrier gas, only makeup gas (air) was used in all cases.

The temperature was started to increase using a ribbon heater. Sampling began when the alcohol aqueous solution reached 100'C. The operating conditions and operating results at the time of sample collection were as shown in Table 1.

For comparison, samples were collected under the same conditions as above using untreated porous glass as a permeable membrane element.

Table 1: Ingredients on the raw material side for pervaporation experiments: Water/2-proper tool is 90.0/10
．． 0, operating conditions are 100°C, carrier gas flow rate 300
cm3min'' and a pressure of 25.5 mmHg.

Example 5 The inorganic permeable membrane element obtained in Examples 1 and 3 was used in Example 4.
A pervaporation experiment of a 20% by weight methanol aqueous solution was carried out using the same apparatus. Alcohol aqueous solution is 100
Sampling started when 'C was reached. The operating conditions and operating results at the time of sample collection were as shown in Table 2.

For comparison, samples were collected under the same conditions as above using untreated porous glass as a permeable membrane element.

Table 2: Pervaporation experiment Raw material side components: water/methanol 80.0/20.0° Operating conditions: 100°C, carrier gas flow rate 300 cm'
m1n-', operated under reduced pressure at a pressure of 25.5 mmHg.

Example 6 The inorganic permeable membrane elements obtained in Examples 1 to 3 were used in Example 4.
A pervaporation experiment of a 95% by weight ethanol aqueous solution was carried out using the same apparatus. Alcohol aqueous solution is 100
Sampling began when °C was reached. The operating conditions and operating results at the time of sample collection were as shown in Table 3.

For comparison, samples were collected under the same conditions as above using untreated porous glass as a permeable membrane element.

Table 3: Pervaporation experiment Ingredients on the raw material side: water/ethanol 5.0/95.0, operating conditions 79°C, carrier gas flow rate 300 cm'm1
Operate under reduced pressure at a pressure of 25.5 mmHg.

[Effect of the Invention J] The selective permeation characteristics at the molecular level of the inorganic permeable membrane produced according to the present invention were confirmed through experiments.

This invention was based on the above-mentioned Japanese Patent Application No. 110343/1988 (Patent Application Publication No. 1-281106). It has also been confirmed that these membranes can maintain stable performance even at high temperatures of 100° C. or higher, and their thickness is uniform, making them useful as gas separation membranes. Furthermore, by appropriately selecting the hydrothermal reaction conditions, the thickness and density of the zeolite membrane can be adjusted freely, so the performance as a gas separation membrane can be set in various ways depending on the purpose. .

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a porous glass or inorganic permeable membrane element. FIG. 2 is a schematic diagram of a module incorporating porous glass or inorganic permeable membrane elements. FIG. 3 is a schematic diagram of a pervaporation test apparatus. FIG. 4 is an aluminum distribution map on the surface of porous glass examined using a scanning electron microscope. 1 - Porous glass 2 - Glass tube 3 - Stainless steel tube Main - Module cell 5 - Carrier gas vibe 6 - Ripon heater 7 - Discharge port
8-Sampling trap 9-Vacuum pump 1
0-Flowmeter 11-Carrier gas 12-Gas dryer 13-Valve 14-Shrink Teflon tube Figure 1 4% Dimensions x-) Iy +) Iy Figure 2 Dimensions
Ko101. Lm 1, Display of the case 1990 Patent Application No. 334498 2, Name of the invention Method for controlling the pore diameter of an inorganic permeable membrane 3, Person making the amendment Relationship to the case Patent applicant address Name Fujio Toda 4, Agent 5 , Date of amendment order: June 18, 1991 (shipment date) 6
, Subject of amendment 1≧ , Exhaustion 7 Contents of amendment (1) From the second line to the last line of page 24 of the specification, "Figure 4 is...a distribution diagram" was changed to "Figure 4 is an energy distribution diagram". "Aluminum distribution map on the surface of porous glass shown in a scanning electron micrograph with a dispersive X-ray analyzer attached." (2) Figure 4 of the drawings will be corrected as shown in the attached sheet.

Claims (1)

[Claims] 1) (A) Supplying an orthosilicate ester or a diluted solution of an orthosilicate into the microscopic pores of a porous silicate body; (B) Concentrating solute components within the pores; (C) Barium, which is difficult to synthesize as zeolite crystals, or tetraethylammonium, etc., is added to the porous glass in which the solute component is concentrated in the pores in an aluminum compound and an alkaline earth metal as a gelling raw material solution. By supplying an aqueous solution of an organic base compound, a hydrated silica-alumina gel is generated in the pore channel; Stabilize the silica-alumina hydrated gel by carrying out a hydrothermal reaction with one end in contact with water or a dilute alkaline aqueous solution and one end in contact with air or a gas inert to the reaction; (E) Optionally, cationic A method for controlling the pore size of an inorganic permeable membrane, comprising: treating with an aqueous solution.