JP2023028577A - silica membrane - Google Patents

Abstract

To provide a silica membrane that can efficiently separate specific components from a mixed solution containing components with different molecular sizes and physical properties, and whose performance (separation ability) is difficult to decrease even when repeatedly used.SOLUTION: The silica membrane of the present disclosure has a central pore size of 0.5 to 5.0 nm and has amino and/or ammonium groups. The silica membrane preferably contains a structure derived from a silane coupling agent having the amino group and/or the ammonium group. The silane coupling agent contains alkoxy groups and monovalent organic groups respectively attached to silicon atoms, and at least one of the monovalent organic groups preferably has an amino group and/or an ammonium group in and/or at the end of the chain.SELECTED DRAWING: None

Description

The present disclosure relates to silica membranes.

In recent years, nanoporous separation membranes such as silica membranes are expected to be applied to separation membranes, membrane reactors, chemical sensors, etc., because they are capable of separation at the molecular level. Among these, to separate a specific component from a mixture containing two or more components by utilizing the molecular sieving function of the nanoporous separation membrane and the physical properties of the membrane surface (for example, hydrophilicity or hydrophobicity). are known.

For example, a methanol carbonylation process is known as an industrial method for producing acetic acid, but in this process, acetaldehyde is produced as a by-product during the reaction, and this acetaldehyde causes deterioration in the quality of the product acetic acid. In this process, methyl iodide is used as a co-catalyst for the metal catalyst, but since methyl iodide is expensive, it is separated from the mixed liquid with acetaldehyde and reused. However, since acetaldehyde and methyl iodide have similar boiling points, it has been difficult to completely separate acetaldehyde and methyl iodide. Methods disclosed in Patent Documents 1 to 4 are known as methods for separating acetaldehyde and methyl iodide from this.

WO2017/057142 JP 2006-94764 A JP-A-9-40590 JP-A-9-77697

However, even with the methods disclosed in Patent Documents 1 to 4, acetaldehyde and methyl iodide could not be completely separated. In addition, although the use of silica membranes (nanoporous separation membranes) for the separation of acetaldehyde and methyl iodide has been considered, even with the use of conventional silica membranes, acetaldehyde and methyl iodide cannot be completely separated. In addition, there was a problem that its performance (separation ability) deteriorated when it was used repeatedly.

Therefore, the object of the present disclosure is to efficiently separate a specific component from a mixed solution containing components with different molecular sizes and physical properties, and silica whose performance (separation ability) is unlikely to decrease even after repeated use It is to provide a membrane.

The inventors of the present disclosure, as a result of intensive studies to achieve the above object, found that acetaldehyde, which is a mixed solution containing components with different molecular sizes and physical properties, can be separated by using a silica membrane having a specific structure. and methyl iodide. The present disclosure relates to what was completed through further studies based on these findings.

That is, the present disclosure provides a silica membrane having a central pore size of 0.5-5.0 nm and having amino groups and/or ammonium groups.

The silica film preferably has a structure derived from the silane coupling agent having the amino group and/or the ammonium group.

In the silica film, the silane coupling agent contains an alkoxy group and a monovalent organic group each bonded to a silicon atom, and at least one of the monovalent organic groups has an amino group in the chain and/or at the end. groups and/or ammonium groups.

In the silica film, the number of atoms in the main chain present between the silicon atom and the nitrogen atom in the amino group and/or the ammonium group is preferably 2 to 4.

The silica membrane preferably has a central pore diameter of 0.8 to 4.0 nm.

The silica membrane preferably has a central pore diameter of 1.0 to 3.0 nm.

The silica film preferably has a surface water contact angle of 0 to 70°.

The silica film is preferably provided on at least one surface of the porous substrate.

The present disclosure also provides a composite membrane comprising a porous substrate and the silica membrane provided on at least one surface of the porous substrate.

According to the silica membrane, a mixed solution containing components with different molecular sizes and physical properties (for example, a mixed solution of acetaldehyde and methyl iodide) can be efficiently separated, and its performance (separation performance) is less likely to decrease.

It is transition of the transmittance|permeability ratio in an Example and a comparative example. It is a transition of the permeability of acetaldehyde in Examples and Comparative Examples.

The silica membrane of the present disclosure is a porous membrane formed mainly from an inorganic compound containing silica, has a central pore diameter of 0.5 to 5.0 nm, and contains amino groups and/or ammonium groups (hereinafter referred to as " (sometimes referred to as "amino group, etc."). In a mixed solution containing hydrophilic and hydrophobic low-molecules, the silica membrane allows hydrophilic low-molecules to permeate and hydrophobic low-molecules to concentrate without permeating them. A case of using a mixed solution of acetaldehyde as a hydrophilic low-molecular molecule and methyl iodide as a hydrophobic low-molecular molecule will be described below as an example. Since the silica membrane has a central pore diameter within the above range, it allows acetaldehyde to permeate through its molecular sieve function. On the other hand, the molecular sieve function alone allows methyl iodide to permeate, but the silica membrane has amino groups and the like, so the surface of the membrane is moderately hydrophilic, making it difficult for methyl iodide to permeate. It is assumed that Acetaldehyde and methyl iodide can be separated efficiently due to the performance of such a silica membrane.

In addition, conventional silica membranes, for example, silica membranes having no amino group or the like on the surface and having hydroxyl groups, have the same molecular sieving function as the silica membrane of the present disclosure, and the property that the surface is hydrophilic. However, repeated use tends to reduce the permeability of acetaldehyde. On the other hand, the silica membrane of the present disclosure has high performance stability, and is characterized in that the acetaldehyde permeability is less likely to decrease even after repeated use. Although the reason for this is not clear, it is possible that the mixed solution containing acetaldehyde and methyl iodide to be separated contains components that are highly reactive with hydroxyl groups, and conventional silica membranes do not react with these components. It is presumed that the permeability of acetaldehyde is reduced as a result of the decrease in hydrophilicity of the membrane surface due to the reaction of hydroxyl groups. On the other hand, probably because the amino group or the like in the silica film of the present disclosure has low reactivity with the component, the performance stability is high, and even after repeated use, the acetaldehyde permeability is unlikely to decrease.

The silica membrane of the present disclosure preferably has monovalent organic groups having an amino group or an ammonium group in the chain and/or at the end. In the monovalent organic group having an amino group or an ammonium group, the monovalent organic group is not particularly limited. or a group in which two or more alkyl groups are bonded via a heteroatom such as a sulfur atom. Among them, an alkyl group is preferable, a straight-chain or branched-chain alkyl group is more preferable, and a straight-chain alkyl group is further preferable. Although the number of carbon atoms in the above monovalent organic group is not particularly limited, it is preferably 1-20, more preferably 1-10, still more preferably 1-7. In addition, the above-mentioned having an amino group or an ammonium group "in the chain and/or at the end" more specifically means, for example, a secondary amino group or an ammonium group in the chain of a monovalent organic group, a tertiary interposed by a primary amino group or ammonium group, or a quaternary ammonium group; and an amino group or ammonium group is bound to a secondary or tertiary carbon atom in the chain of the monovalent organic group. , means that an amino group (--NH ₂ ; primary amino group) or an ammonium group (--NH ₃ ⁺ ; primary ammonium group) is bound to the terminal carbon atom of a monovalent organic group.

The amino group may be a primary amino group, a secondary amino group, or a tertiary amino group. The ammonium group may be any of a primary ammonium group, a secondary ammonium group, a tertiary ammonium group and a quaternary ammonium group. The amino group or the like may be a substituted amino group or the like substituted with an organic group. In addition, it may be an unsubstituted amino group or the like, and a substituted amino group or the like can be obtained by subjecting a silica film having an unsubstituted amino group or the like to an organic matter treatment or using it for separation of an organic matter. The amino group may be of only one type, or may be of two or more types.

The substituent of the substituted amino group or the like is a monovalent organic group, such as an alkyl group (preferably an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms), an aryl group (preferably an aryl group having 6 to 14 carbon atoms, more preferably an aryl group having 6 to 10 carbon atoms), or a group in which these are bonded. When the substituted amino group or the like has a plurality of substituents, the plurality of substituents may be the same or different.

The silica film may contain a monovalent organic group that does not have an amino group or the like. Examples of the monovalent organic group having no amino group include, for example, an alkyl group; a group having a carboxy group, a hydroxyl group, or a mercapto group at the end of the alkyl group; an ether bond or a thioether bond in the chain of the alkyl group. include those that have Although the alkyl group is not particularly limited, it is, for example, a cyclic alkyl group, a linear alkyl group, or a branched alkyl group. Although the number of carbon atoms in the alkyl group is not particularly limited, it is preferably 1-20, more preferably 1-10, still more preferably 1-7. Hereinafter, the amino group or the like contained in the silica film and the monovalent organic group having no amino group or the like may be collectively referred to as a monovalent organic group.

The silica film may contain a metal oxide as a film-forming inorganic compound. Examples of the metal oxides include alumina, zirconia, titania, and magnesia. The above silica film can be made finer by adjusting the type and ratio of metal oxides used in combination with silica, plasma treatment of the silica film, introduction of monovalent organic groups to the surface, and type and amount of monovalent organic groups. It is possible to adjust the pore size, surface hydrophilicity, hydrophobicity, water contact angle, and other surface properties of the silica membrane.

The central pore diameter of the silica membrane is not particularly limited as long as it is 0.5 to 5.0 nm, preferably 0.8 to 4.0 nm, more preferably 1.0 to 3.0 nm. The central pore diameter is the median diameter (D50) and can be measured by a single component gas permeation test ( _H2 , _CO2 , _N2 , _CH4 , _CF4 , _SF6 ) or a nanoperm porometry method. . The central pore size is preferably in a range suitable for separation of mixed liquids, not for separation of mixed gases. Moreover, it is preferable that the central pore diameter of the silica film before introducing the silane coupling agent is within the above range.

The water contact angle of the silica film surface is not particularly limited, but is preferably 0 to 70°, more preferably 15 to 70°, and more preferably 30 to 70°. When the water contact angle is within the above range, the surface exhibits moderate hydrophilicity, making it difficult for hydrophobic low-molecular-weight molecules to permeate, effectively separating mixed solutions containing components with different molecular sizes and physical properties (hydrophilicity). can do.

The silica film preferably has a structure derived from a silane coupling agent having an amino group and/or an ammonium group. That is, it is preferable that the silica film has an amino group or the like introduced by the silane coupling agent. In other words, the silica film preferably has an amino group or the like derived from the silane coupling agent. The sila coupling agent may be of one type or two or more types.

When the silica film has a structure derived from the silane coupling agent, when the silane coupling agent is introduced into the silica film, the hydroxyl groups present on the surface of the silica film are dehydrated with the alkoxy groups of the silane coupling agent. It condenses by reaction. Therefore, the amount of hydroxyl groups on the surface of the silica film can be reduced, and the reaction between a component highly reactive with hydroxyl groups and hydroxyl groups in the mixed solution containing acetaldehyde and methyl iodide is reduced. On the other hand, since the amino groups and the like derived from the silane coupling agent increase, the surface of the silica film can maintain moderate hydrophilicity, and acetaldehyde and methyl iodide can be efficiently separated. . In addition, the stability of performance is high, and the permeability of acetaldehyde does not easily decrease even after repeated use.

The silane coupling agent comprises an alkoxy group and a monovalent organic group respectively bonded to a silicon atom, at least one of the monovalent organic groups having an amino group and/or an ammonium have a group. That is, the silane coupling agent contains an alkoxy group and a monovalent organic group having an amino group or the like bonded to a silicon atom, and may further contain a monovalent organic group having no amino group or the like. good.

In the monovalent organic group having an amino group or the like, the monovalent organic group is not particularly limited. and groups in which two or more alkyl groups are bonded via a heteroatom such as . Among them, an alkyl group is preferable, a straight-chain or branched-chain alkyl group is more preferable, and a straight-chain alkyl group is further preferable. Although the number of carbon atoms in the above monovalent organic group is not particularly limited, it is preferably 1-20, more preferably 1-10, still more preferably 1-7.

In the silane coupling agent, the number of atoms in the main chain present between the silicon atom in the silane coupling agent and the nitrogen atom in the amino group and/or the ammonium group is 1 to 8. is preferred, more preferably 2-4. When the number of atoms in the main chain is 8 or less (particularly 4 or less), the pores are prevented from becoming small, the hydrophilicity of the silica membrane surface is moderated, and the permeability is improved. For example, when the main chain is a divalent linear hydrocarbon group, the number of atoms in the main chain is the same as the number of carbon atoms.

In the monovalent organic group having an amino group or the like, the amino group may be a primary amino group, a secondary amino group, or a tertiary amino group. Moreover, the ammonium group may be any of a primary ammonium group, a secondary ammonium group, a tertiary ammonium group and a quaternary ammonium group. The amino group or the like may be a substituted amino group or the like substituted with an organic group. In addition, it may be an unsubstituted amino group or the like, and a substituted amino group or the like can be obtained by subjecting a silica film having an unsubstituted amino group or the like to an organic matter treatment or using it for separation of an organic matter. For example, when a methyl iodide (MeI) solution is passed through a monovalent organic group having a primary amino group, a secondary amino group or primary ammonium group can be generated from the primary amino group. , and other amino and ammonium groups may also occur. The amino group may be of only one type, or may be of two or more types.

The silane coupling agent may contain a monovalent organic group having no amino group or the like. Examples of the monovalent organic group having no amino group include, for example, an alkyl group; a group having a carboxy group, a hydroxyl group, or a mercapto group at the end of the alkyl group; an ether bond or a thioether bond in the chain of the alkyl group. include those that have Although the alkyl group is not particularly limited, it is, for example, a cyclic alkyl group, a linear alkyl group, or a branched alkyl group. Although the number of carbon atoms in the alkyl group is not particularly limited, it is preferably 1-20, more preferably 1-10, still more preferably 1-7.

The alkoxy group possessed by the silane coupling agent is represented by the general formula RO-- (R represents an alkyl group). The alkyl group for R is preferably a straight-chain or branched-chain alkyl group, more preferably a straight-chain alkyl group. The number of carbon atoms in the alkyl group as R (that is, the number of carbon atoms in the alkoxy group) is not particularly limited, but is preferably 1 to 10, more preferably 1 to 5, still more preferably 1 to 4, especially Preferably it is 1 or 2. The alkoxy group possessed by the silane coupling agent specifically includes a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, a sec-butoxy group, a t-butoxy group and the like.

The silane coupling agent is preferably represented by the following formula.
Rx ^- Si- ^R1m ( ^OR2 ) 3 _{- m}
(R ¹ represents an optionally substituted alkyl group having 1 to 3 carbon atoms; R ² represents an optionally substituted alkyl group having 1 to 3 carbon atoms; R ^X represents an alkyl group having an amino group and/or the above-mentioned ammonium group in the chain and/or at the end.m represents an integer of 1 to 3.)

The substituent that the alkyl group may have in R ¹ and R ² is not particularly limited as long as it does not interfere with the hydrolysis and dehydration condensation of the silane coupling agent. , an alkenyloxy group having 2 to 6 carbon atoms, an aliphatic acyl group having 2 to 6 carbon atoms, a benzoyl group, a nitro group, a nitroso group, a hydroxy group, a cyano group, a sulfonic acid group, a primary amino group, etc. An amino group, a carboxy group, a hydroxyl group, a mercapto group, a halogen atom, and the like are included.

In the alkyl group having an amino group or the like of R ^X , the alkyl group is not particularly limited, but for example, a cyclic alkyl group, a straight-chain alkyl group, or a branched-chain alkyl group is preferable, and a straight-chain or branched-chain alkyl group is more preferable. and more preferably a straight-chain alkyl group. Although the number of carbon atoms in the alkyl group is not particularly limited, it is preferably 1-20, more preferably 1-10, still more preferably 1-7.

In the above R ^X alkyl group having an amino group or the like, the number of atoms in the main chain between the nitrogen atom and Si in the amino group or the like is preferably 1-8, more preferably 2-4. When the number of atoms in the main chain is 8 or less (particularly 4 or less), the pores are prevented from becoming small, the hydrophilicity of the silica membrane surface is moderated, and the permeability is improved.

Specifically, the silane coupling agent includes 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-( aminoethyl)-3-aminopropyltriethoxysilane, trimethoxy[3-(methylamino)propyl]silane, [3-(N,N-dimethylamino)propyl]trimethoxysilane, trimethoxy[3-(phenylamino)propyl ] silane, N-[2-(N-vinylbenzylamino)ethyl]-3-aminopropyltrimethoxysilane, N-[8-(trimethoxysilyl)octyl]ethane-1,2-diamine, N-[3 -(trimethoxysilyl)propyl]-1-butanamine, [3-(diethylamino)propyl]trimethoxysilane, 3-[(1,3-dimethylbutylidene)amino]propyltriethoxysilane, (3-mercaptopropyl) Trimethoxysilane, (3-mercaptopropyl)triethoxysilane, and N,N-bis[(diphenylphosphino)methyl]-3-(triethoxysilyl)propylamine. One or more of these silane coupling agents may be used.

In the silica film, the amino groups and/or the ammonium groups are bonded to silicon atoms constituting the silica film via groups represented by the following formula (1), for example.
-X-Si(-O-) ₃ (1)
[In the formula (1), X represents a divalent organic group, the bond extending to the left of X is bonded to the nitrogen atom in the amino group or the ammonium group, and the bond extending to the right of O is, respectively, It is bonded to the silicon atoms constituting the silica film and/or the silicon atoms in other groups represented by formula (1). ]

The number of atoms in the main chain of X is preferably 1-8, more preferably 2-4. When the number of atoms in the main chain is 8 or less (particularly 4 or less), the pores are prevented from becoming small, the hydrophilicity of the silica membrane surface is moderated, and the permeability is improved.

The silica film can be produced by subjecting a silane coupling agent having an amino group and/or an ammonium group to a dehydration condensation reaction with a silica film having a silanol group. The dehydration-condensation reaction can be carried out, for example, by impregnating a cloth with a liquid containing a silane coupling agent, applying it to a silica film having silanol groups, and reacting it at 110° C. for 0.5 to 1 hour. The silica film containing silanol groups may be subjected to a treatment to increase hydroxyl groups by introducing water vapor or irradiating the silica film with plasma before the reaction with the silane coupling agent.

The thickness of the silica film is, for example, 0.1 to 10 μm, preferably 0.1 to 1 μm.

The silica film is preferably provided on at least one surface of the porous substrate. The porous substrate acts as a substrate for supporting the silica membrane. The porous substrate has pores through which acetaldehyde can pass. A composite membrane can be obtained by providing the silica membrane on at least one surface of the porous substrate.

As the porous substrate, known or commonly used substrates can be used. Examples of materials constituting the porous substrate include inorganic substances such as silica, alumina, mullite, zirconia, cordierite, titania, silicon nitride, silicon carbide, stainless steel, copper, aluminum, titanium, and ceramics. .

The thickness of the porous substrate is, for example, 50-3000 μm, preferably 500-2000 μm.

Each aspect disclosed in this specification may be combined with any other feature disclosed in this specification. Each configuration and combination thereof in each embodiment is an example, and addition, omission, replacement, and other changes of configuration are possible as appropriate without departing from the gist of the present disclosure. In addition, each invention according to the present disclosure is not limited by the embodiments or the following examples, but only by the claims.

An embodiment of the present disclosure will be described in more detail below based on examples.

(Example 1)
A commercially available nano-ceramic porous substrate (model number: eSep-nano-Si-1.5-2, manufactured by E-Sep Co., Ltd.) is used as a porous layer mainly composed of silica having through holes of 1.5 to 2.0 nm. Using. The silica porous layer has a thickness of about 500 nm, and the lower layer has a structure supported by an α-alumina porous substrate formed of macropores. The outer shape was cylindrical with a diameter of 12 mm, an inner diameter of 9 mm and a length of 40 cm. Air having a humidity of 50% or more at 25° C. was introduced to the outside of the cylindrical membrane for 1 minute or more. At that time, the inside of the cylindrical membrane was decompressed to forcibly introduce water vapor into the membrane pores. A state in which water vapor remained in the pores of the membrane was maintained for 6 hours or longer to accelerate the formation of OH groups in the silica layer. 3-Aminopropyltrimethoxysilane (APTMS), which is a silane coupling agent, is diluted 100 times with water and allowed to stand at room temperature for 3 hours or longer to allow the hydrolysis reaction to proceed sufficiently before the liquid is applied to a cloth. The cloth was applied to the cylindrical composite membrane prepared above, and then dried at 110° C. for 0.5 hours for immobilization to obtain a silica membrane.

(Example 2)
For the silica film obtained in Example 1, 99.5 wt% MeI (manufactured by Wako Pure Chemical Industries) was passed through and circulated for 7 hours at room temperature, and then immersed in a stationary state for 16 hours to form a silica film. Obtained.

(Comparative example 1)
Prepare a commercially available nano-ceramic porous substrate (model number: eSep-nano-Si-0.5-1, manufactured by E-Sep Co., Ltd.) mainly composed of silica having through holes of 0.5 to 1.0 nm, and silica used as a membrane. Unlike Examples 1 and 2, the silica film did not have an amino group because no silane coupling agent was introduced. The thickness of the silica porous layer in the substrate is about 500 nm, and the lower layer has a structure supported by the α-alumina porous substrate formed of macropores. The outer shape was cylindrical with a diameter of 12 mm, an inner diameter of 9 mm and a length of 40 cm.

(Comparative example 2)
Prepare a commercially available nano-ceramic porous substrate (model number: eSep-nano-Si-1-1.5, manufactured by E-Sep Co., Ltd.) mainly composed of silica having through holes of 1.0 to 1.5 nm, and silica used as a membrane. Unlike Examples 1 and 2, the silica film did not have an amino group because no silane coupling agent was introduced. The thickness of the silica porous layer in the substrate is about 500 nm, and the lower layer has a structure supported by the α-alumina porous substrate formed of macropores. The outer shape was cylindrical with a diameter of 12 mm, an inner diameter of 9 mm and a length of 40 cm.

For the various silica membranes shown in Table 1, the separation performance of acetaldehyde and methyl iodide was evaluated by a pervaporation method (pervaporation method) under heating and pressurized conditions. Specifically, first, a separation membrane having a membrane area of 120.6 cm ² was attached to a pervaporation apparatus. About 600 g of a liquid mixture of 79.77% by mass of acetaldehyde, 7.78% by mass of methyl iodide, and 12.45% by mass of water was introduced into the apparatus as the feed liquid component. The solution was heated to 50° C. in a water bath, and supplied to the separation membrane at a rate of 75 ml/min with a liquid feed pump while maintaining the pressure on the feed liquid side at 190 kPaG. The pressure on the permeate side was normal pressure, and the permeate was allowed to permeate for 4 to 5 hours, followed by collection with a cold trap to collect the permeate. Acetaldehyde permeability [mol/m ² ·s·Pa] and permeability ratio were calculated by gas chromatography analysis and moisture analysis. The permeability ratio was determined as [permeability of acetaldehyde/permeability of methyl iodide]. Table 1 shows the results. "AD" shown in Table 1 indicates acetaldehyde. The same experiment was repeated 6 times for the silica film of Example 1, 3 times for the silica film of Example 2, 4 times for the silica film of Comparative Example 1, and 5 times for the silica film of Comparative Example 2, and evaluated. gone. FIG. 1 shows the transition of the transmittance ratio in Examples and Comparative Examples. FIG. 2 shows changes in acetaldehyde permeability in Examples and Comparative Examples.

Further, the water contact angle of the silica films of Examples 1 and 2 was measured by dropping one drop of water on the film surface using a contact angle meter "Drop Master 700" (manufactured by Kyowa Interface Science Co., Ltd.), and measuring the angle at that time. It was measured. For the silica film of Example 1, the water contact angle of the silica film before the experiment and the water contact angle after six experiments, and the water contact angle of the silica film of Example 2 after three experiments were measured. Table 2 shows the results.

As can be seen from Table 1, when a silica membrane having a central pore diameter of 0.5 to 5.0 nm and having an amino group was used as a separation membrane (Examples 1 and 2), the permeability of acetaldehyde was high, and The result was that the transmittance ratio did not change significantly over the number of experiments (Figs. 1 and 2). On the other hand, when a silica membrane having no amino group was used as the separation membrane (Comparative Examples 1 and 2), the permeability of acetaldehyde was low, and the permeability ratio decreased significantly with the number of experiments. became (Figs. 1 and 2). From this, it can be concluded that a silica film having a central pore diameter of 0.5 to 5.0 nm and having amino groups can be used to prepare a mixed solution containing components with different molecular sizes and/or physical properties, that is, acetaldehyde and methyl iodide. It was clarified that the separation can be performed efficiently and that the performance (separation ability) does not deteriorate even after repeated use.

Claims (9)

A silica membrane having a central pore diameter of 0.5 to 5.0 nm and having an amino group and/or an ammonium group. 2. The silica film according to claim 1, having a structure derived from a silane coupling agent having said amino group and/or said ammonium group. The silane coupling agent comprises an alkoxy group and a monovalent organic group each bonded to a silicon atom, and at least one of the monovalent organic groups has an amino group and/or an ammonium group in the chain and/or at the end. 3. The silica membrane of claim 2, comprising groups. 4. The silica film according to claim 3, wherein the number of atoms of the main chain present between the silicon atom and the nitrogen atom in the amino group and/or the ammonium group is 2 to 4. The silica membrane according to any one of claims 1 to 4, which has a central pore size of 0.8 to 4.0 nm. The silica membrane according to any one of claims 1 to 5, which has a central pore diameter of 1.0 to 3.0 nm. The silica membrane according to any one of claims 1 to 6, wherein the surface has a water contact angle of 0 to 70°. The silica membrane according to any one of claims 1 to 7, which is provided on at least one surface of a porous substrate. A composite membrane comprising a porous substrate and the silica membrane according to any one of claims 1 to 8 provided on at least one surface of the porous substrate.

Images