JPH0357817B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for modifying porous materials.

[Prior art]

Porous materials have extremely large surface areas and adsorption activities, and have recently been widely used as column packing materials for liquid chromatography, gas chromatography, etc., in addition to catalysts for various catalytic reactions. Such porous materials include silica gel, alumina, silica alumina, zeolite, diatomaceous earth, etc., and silica gel and alumina, especially silica gel, are widely used as packing materials for liquid chromatography.

Porous materials can be used as adsorption system packings without modification due to their large surface area and strong adsorption activity. However, since the adsorption activity of inorganic porous fillers such as silica gel and alumina varies greatly depending on their water content, care must be taken when handling them. On the other hand, recently, so-called reverse-phase packing materials, in which the surface of silica gel is modified with _C18 or _C8 alkyl groups by treating the surface of silica gel with octadecyltrichlorosilane (ODS) or octyltrichlorosilane, have become widely used. Ta. ODS−
Reversed phase packings such as silica are water-methanol based,
Since it has extremely stable activity against eluents such as water-acetonitrile, it is easy to handle, and various buffer solutions can be used.

Apart from this, fillers in which the surface of silica gel is modified with aminopropyl groups, cyanopropyl groups, diol groups, etc. are also commercially available. Furthermore, columns with optically active functional groups bonded to the silica surface and columns with fillers bonded with crown ether or the like are also commercially available. however,
Even when these columns are used, there are still many substances that are difficult to separate, and there is a desire to develop packing materials with even better performance. Furthermore, these commercially available columns have essentially only one type of group on the surface of the packing material as a functional group effective for separation. It is expected that the ability to identify objects will increase. From this point of view, there are currently no columns on the market that have introduced functional groups that are substantially effective in separating two or more types.

〔the purpose〕

As a result of extensive research into selective separation methods using porous materials, the present inventors found that if two or more functional groups that are substantially involved in separation are regularly introduced onto the surface of a porous material, The present invention was developed by focusing on the improvement of selective separation performance for specific substances.

〔composition〕

According to the present invention, a compound having a functional group that has an eliminable group and is reactive with the first functional group present in the pores of a porous material is added to the first functional group that exists in the pores of the porous material. and a step of forming a second functional group in the pore by eliminating the removable group contained in the reacted compound, and forming a second functional group in the pore.
The compound having a releasable group to be reacted with the functional group of the first
Provided is a method for improving a porous material, characterized in that the first functional group has a size that provides steric hindrance upon reaction with the first functional group, and is reactively bonded to only a portion of the first functional group.

Porous materials include silica gel, alumina, silica-alumina, zeolite, diatomaceous earth, etc., and silica gel, alumina, especially silica gel, and alumina, especially silica gel are suitable as packing materials for liquid chromatography. The pore properties of silica gel depend largely on its preparation conditions;
In particular, their surface area and pore system influence their separation properties in chromatography. In the present invention, as an example, a material having a pore diameter of 40 to 100 Å is used for modification. When using a material with a pore diameter of 40 Å or less,
The steric hindrance during the reaction becomes even greater. OH groups exist on the surfaces of silica gel and alumina, and various modifications are performed via these OH groups. In the present invention, the starting material is preferably one in which an aminopropyl group is introduced by reacting the OH group with aminopropyltriethoxysilane. The amount introduced was determined by elemental analysis (C, H, N), and hereinafter the amount of the compound introduced into the porous material was determined by elemental analysis unless otherwise specified.
This silica gel modified with an aminopropyl group and a column filled with this silica gel are commercially available for use in liquid chromatography and are well known. The present invention relates to a reactive functional group that has a detachable group in its molecule, provides steric hindrance upon chemical bonding with a porous substance, and exists as a first functional group in the pores of the porous substance. A different functional group is converted into a second functional group by bonding a compound that binds to substantially only a portion of, but not all of, the releasable group, and then removing the releasable group under appropriate conditions. The material is novel. Further, if necessary, another compound which may contain a detachable group is further bonded to the first reactive functional group remaining unreacted in the pores of the porous material, and another third compound is bonded to the first reactive functional group remaining unreacted in the pores of the porous material. Functional groups can also be introduced and, if necessary, further different functional groups can be introduced by repeating this step in sequence.

In preferred embodiments of the invention, the porous materials include silica gel and alumina, with silica gel being particularly preferred. The reactive functional group is preferably an aminoalkyl group bonded via an OH group present on the surface of the porous material, particularly an amino group such as an aminopropyl group. Methods for introducing amino groups into silica gel are known, and are easily carried out, for example, by reacting silica gel and aminopropyltriethoxysilane in toluene under reflux.

In a preferred embodiment of the present invention, the removable group present in the molecule of the compound to be bonded to the porous substance is an ester group, and examples of compounds large enough to provide steric hindrance during chemical bonding include, for example, aliphatic Alcohols, such as _C1 - _C36 alcohols,
Preferably higher aliphatic alcohols, _e.g.
C ₃₆ alcohols, especially C ₈ -C ₁₈ alcohols, fatty acids, such as C ₁ -C ₃₆ fatty acids, preferably higher fatty acids, such as C ₁ -C ₃₆ fatty acids, preferably C ₈ -C ₁₈ fatty acids, etc. It is an ester containing

In a preferred embodiment of the present invention, the compound having a removable group and having a size large enough to provide steric hindrance upon chemical bonding is bonded to a first reactive functional group, preferably an amino group, in the porous material. It is preferably a compound having an acid chloride which can be chemically bonded via this group to an amino group preferably present in the porous material. In this case, hydrochloric acid is eliminated by the acylation reaction and the compound is introduced via an amide bond. This reaction is carried out in a water-free inert organic solvent between 0 and 200
℃, preferably at the reflux temperature of the solvent. This inert organic solvent includes, for example, aliphatic hydrocarbons,
Cycloaliphatic hydrocarbons, e.g. pentane, hexane, heptane, etc.; chlorinated hydrocarbons, e.g. dichloromethane, chloroform, carbon tetrachloride, trichloroethane, chlorobenzene, etc.; aromatic hydrocarbons, e.g. Includes benzene, toluene, xylene, etc., with benzene, toluene, etc. being preferred.
Particularly preferred is toluene. Furthermore, an acid binder may be used in the acylation reaction in this case.

In a preferred embodiment of the present invention, the material has a removable group, preferably an ester group, and a group that binds to a reactive group, preferably an amino group, of the porous substance, and provides steric hindrance during the bonding. compounds that give
Preferably, the acid chloride is obtained by, for example, reacting an acid anhydride of a dibasic acid with an alcohol to produce a carboxylic acid containing an ester group, and chlorinating the hydroxyl group of the carboxyl group. This esterification reaction is preferably carried out in a water-free inert organic solvent from 0 DEG to 200 DEG C., preferably at the reflux temperature of the solvent. The inert organic solvents include, for example, aliphatic hydrocarbons such as pentane, hexane, heptane, cycloaliphatic hydrocarbons such as cyclopentane, cyclohexane, chlorinated hydrocarbons such as dichloromethane, chloroform, tetrachloride, etc. Carbon, trichloroethane, chlorobenzene, and other aromatic hydrocarbons such as benzene, toluene, xylene, etc. are included, with benzene and toluene being preferred, and toluene being particularly preferred.

Chlorination of carboxylic acids containing ester groups is carried out, for example, by chlorination with thionyl chloride, thereby giving acid chlorides. Chlorination with thionyl chloride is preferably carried out in a water-free inert organic solvent at 0 DEG to 200 DEG C., preferably at the reflux temperature of the solvent. This inert organic solvent contains
For example aliphatic hydrocarbons such as pentane, hexane, heptane, cycloaliphatic hydrocarbons such as cyclopentane, cyclohexane, chlorinated hydrocarbons such as dichloromethane, chloroform, carbon tetrachloride, trichloroethane, chlorobenzene, etc. Aromatic hydrocarbons, such as benzene,
It includes toluene, xylene, etc., with benzene and toluene being preferred, and toluene being particularly preferred. Examples of dibasic acid anhydrides include succinic anhydride, maleic anhydride, phthalic anhydride, and the like.

The reactive compound used in the present invention that has a removable group and is capable of bonding to a reactive functional group present in the pores of a porous material is to the extent that it causes steric hindrance when bonding with the reactive functional group. is large in size, and is therefore bonded to only a portion of the reactive functional group at a substantial spacing, while the unbonded portion of the functional group is bonded to a substantially spacing in the porous material. leave it behind and remain. Such reactive compounds therefore contain large groups, for example when starting from dibasic acid anhydrides and alcohols, higher aliphatic alcohols, e.g.
By using _C6 - _C36 , especially _C8 - _C18 alcohols, the desired compounds are obtained. However, other alcohols can of course also be used. The acid anhydride and alcohol can be added in any quantitative ratio, but are preferably added in stoichiometric amounts. Thionine chloride is preferably used in excess. The product is easily obtained by removing the solvent, such as by evaporation, and does not require further purification. An example of a reaction process in which an acid anhydride and an aliphatic alcohol are used as starting materials and chlorination is carried out using thionichloride is shown below.

In the formula, A represents an alkyl, alkenyl, or aryl group, and R represents an alkyl, alkenyl, alkynyl, cycloalkyl, or aryl group.

The reactive compounds can be used in amounts of 0.01 to 10 mol, preferably 0.1 to 5 mol, particularly preferably 0.5 to 3 mol, per mol of reactive functional groups in the porous material.

After bonding the reactive compound to the first reactive functional group as described above, the removable group present in the reactive compound is eliminated by an appropriate method to form a second functional group. to form. In a preferred embodiment of the invention, the removable group is an ester group. In a preferred embodiment of the invention, the ester group is hydrolyzed with acid or alkali in a suitable solvent. Suitable solvents include water, polar organic solvents such as methanol, ethanol, propanol, isopropanol and butanol, acetone, acetonitrile,
N,N-dimethylformamide and the like, as well as mixtures thereof. Preferably, mixtures of water and these polar organic solvents, especially alcohols, are used. As acids or alkalis, customary inorganic or organic acids or bases may be used. In the present invention, it is preferable to hydrolyze with an acid, and hydrochloric acid is particularly preferable. Therefore, in a particularly preferred embodiment of the invention, 0.1
~6N, preferably 0.2~4N, particularly preferably 0.5~
Hydrolyze for 10-60 min under reflux using 3N hydrochloric acid solution. Through this hydrolysis, the alcohol group of the bonded compound is removed, and a carboxyl group is generated at the end of the surface of the porous material. It can be installed and installed.

Next, if necessary, a third functional group can be introduced by bonding a compound different from the one described above to the reactive functional group remaining in the pores of the porous material.
In this case, if the compound contains a removable group, this can be removed to introduce a third functional group. If appropriate, further different functional groups can be introduced into the porous material by repeating this step in sequence.

〔effect〕

The thus obtained porous material modified according to the present invention can be filled into a column by an appropriate known method and used as a column for chromatography, especially a column for high performance liquid chromatography.

〔Example〕

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

Reference example 1 Silica gel (SI-40 for column chromatography manufactured by Merck, particle size: 0.063 to 0.200 mm, pore size 40
(hereinafter abbreviated as SI-40) was placed in a 200 ml flat bottom flask equipped with a reflux condenser.
100 ml of toluene was added, followed by 3.0 g of aminopropyltriethoxysilane, and the mixture was reacted for 1 hour under reflux of the toluene solvent while stirring with a magnetic stirrer. The silica gel was then separated from the solvent by filtration, and 30 mL was added with 50 ml of benzene.
The mixture was washed twice with 50 ml of dichloromethane, and dried overnight at 100° C. in a vacuum dryer to obtain aminopropyl silica (hereinafter abbreviated as AP silica).
This product was subjected to elemental analysis to determine the introduced aminopropyl group.

Elemental analysis value: C: 6.58%; H: 2.47%; N:
1.65%.

From the nitrogen content, it was found that 1.18 mmol of aminopropyl groups were bound per gram of silica gel.

Different silica gels (Merck Co., Ltd. SI-60 for column chromatography, 0.063 to 0.200 mm, pore size 60
An aminopropyl group was bonded to silica gel in the same manner as above except that SI-60 (hereinafter abbreviated as SI-60) was used.

Elemental analysis value: C: 5.50%; H: 1.81%; N:
1.53%.

From the nitrogen content, it was found that 1.09 mmol of aminopropyl groups were bound per gram of silica gel.

Different silica gels (Merck Co., Ltd. SI-100 for column chromatography, particle size: 0.063 to 0.200 mm,
An aminopropyl group was bonded to silica gel in the same manner as above, except that the pore size was 100 Å (hereinafter abbreviated as SI-100).

Elemental analysis value: C: 4.07%; H: 1.27%; N:
1.12%.

From the nitrogen content, it was found that 0.80 mmol of aminopropyl groups were bound per gram of silica gel.

Reference Example 2 Preparation of ester group-containing acylating agent 5.0 g (0.05 mol) of succinic anhydride and 7.91 g (0.05 mol) of n-decanol were placed in an eggplant-shaped flask equipped with a reflux condenser, and 200 ml of toluene was added thereto. The reaction was carried out under reflux for 3 hours. Take a portion of this and use acetonitrile:water = 1:1 as an eluent.
Analysis of succinic anhydride by high performance liquid chromatography using an ODS-silica gel column revealed that almost no unreacted succinic anhydride was detected, indicating that the reaction was quantitative. In addition, the NMR spectrum revealed a carboxyl group peak at around 11.3 ppm based on TMS. After the reaction product was cooled in the flask, about 4 equivalents (about 14.5 ml) of thionyl chloride was added to the flask and heated under reflux for 2 hours. The solvent was removed on a rotary evaporator, redissolved twice with 100 ml of benzene, and the benzene was removed on a rotary evaporator each time, followed by drying at 80° C. in a vacuum dryer overnight. The product is
The NMR spectrum revealed that the peak around 11.3 ppm had disappeared, indicating that the carboxyl group was chlorinated. Therefore, this compound is a compound called n-decylic acid (chlorocarbonyl)-propionate (C ₁₀ H ₂₁ OCOC ₂ H ₄ COCl), hereinafter abbreviated as E ₁ .

The above method was repeated except that 10.72 g (0.05 mol) of n-tetradecanol was used instead of n-decanol, and n-tetradecylic acid (chlorocarbonyl)-propionate (C ₁₄ H ₂₉ OCOC ₂ H ₄ COCl ) was obtained. This compound is hereinafter abbreviated as _E2 .

Octadecanol instead of n-decanol
_The above method _was repeated except that 13.52 g (0.05 mol) was used to obtain octadecyl acid ( _{chlorocarbonyl} )-propionate ( _{C18H37OCOC2H4COCl} ). This compound is hereinafter abbreviated as _E3 .

Example 1 [Reaction step] Ester group-containing acid chloride from Reference Example 2
A toluene solution containing E ₁ at 0.25 mmol/ml was prepared. Dilute 25 ml of this solution with 25 ml of toluene and add 5.0 g of AP silica SI-40 from Example 1 to this solution.
In addition, the acylation reaction of AP silica was carried out for 1 hour under reflux while stirring with a magnetic stirrer.
After the reaction was completed, the silica gel was cooled to room temperature, separated by filtration, washed 3 times with 50 ml of benzene and 3 times with 50 ml of dichloromethane, and dried in a vacuum dryer for 100 mL.
Dry overnight at °C. Elemental analysis revealed that 0.47 mol of E ₁ was bound per mol of amino group.

The above method was repeated except that E ₂ was used instead of E ₁ . As a result of elemental analysis of the obtained silica gel, 0.42 mol of E ₂ per 1 mol of amino group was found.
were combined.

The above procedure was repeated except that E ₃ was used instead of E ₁ . As a result of elemental analysis of the obtained silica gel, 0.34 mol of E ₃ per 1 mol of amino group was found.
were combined.

Next, instead of AP silica SI-40, use AP silica SI−
An acylation reaction was carried out with E ₁ , E ₂ and E ₃ using E 60 in the same manner as above. As a result of elemental analysis, amino group 1
0.57, 0.49 and 0.49 moles of E ₁ per mole, respectively;
E ₂ and E ₃ were combined.

Next, instead of AP silica SI-40, use AP silica SI−
Acylation reactions were carried out with E ₁ , E ₂ and E ₃ in the same manner as above using E 100. As a result of elemental analysis, amino group 1
0.68, 0.60 and 0.60 moles of E ₁ per mole, respectively;
E ₂ and E ₃ were combined.

These results revealed that silica gel with a smaller pore diameter is more likely to experience steric hindrance, and acid chloride containing an alcohol with a larger number of carbon atoms via an ester group is more likely to experience steric hindrance.

Example 2 [Desorption step] AP silica SI treated with _E2 in Example 1
3.0 g of -40 was added to 30 ml of a 2N hydrochloric acid solution of water:ethanol = 1:1, and hydrolysis was carried out under reflux while stirring with a magnetic stirrer. After hydrolysis, it was cooled to room temperature, the silica gel was separated by filtration, and 3 times with 50 ml of a solution of water:ethanol = 1:1.
and 50 ml of methanol three times, and dried overnight at 100°C in a vacuum dryer. As a result of comparing the elemental analyzes before and after hydrolysis, per molecule of bound _E2 ,
Since 14.2 carbon atoms have been eliminated and the value of nitrogen atoms is almost unchanged, hydrolysis does not affect other functional groups, and all _C14 alcohols are selectively eliminated, and the silica gel surface A carboxyl group could be generated at the upper end. The presence of this carboxyl group was also confirmed by the absorption peak near 1700 cm ^-1 in the IR spectrum.

The same procedure as above was repeated using 3.0 g of AP silica SI-60 treated with E2 instead of AP silica SI- ₄₀ . As a result of elemental analysis, 13.7 carbon atoms were released per molecule of bonded E ₂ , and the value of nitrogen atoms remained almost unchanged, so hydrolysis did not affect other functional groups and C ₁₄ All of the alcohol was selectively eliminated, and carboxyl groups were generated at the terminals on the silica gel surface. The presence of carboxyl groups was also confirmed from the IR spectrum.

The same procedure as above was repeated using 3.0 g of AP silica SI-100 treated with E2 instead of AP silica SI- ₄₀ . As a result of elemental analysis, carbon atoms per bonded E ₂ molecule are
14.4 were eliminated, and the value of the nitrogen atom remains almost the same. Therefore, hydrolysis does not affect other functional groups, and all _C14 alcohols are selectively eliminated, and the terminals on the silica gel surface are eliminated. It was possible to generate a carboxyl group. Also
The presence of carboxyl groups was also confirmed from the IR spectrum.

Example 3 Two types of silica gel for high performance liquid chromatography (HPLC) (manufactured by Merck & Co., Ltd.) were used instead of the silica gel for column chromatography in Reference Example 1.
Amino groups and carboxyl groups were introduced in the same manner as in Reference Examples 1 and 2 and Examples 1 and 2 using LiChrosorbSI-60 (particle size 10 μm). These two types of HPCL
The silica gel used for column chromatography differs only in particle size from the corresponding silica gel used for column chromatography, but has the same characteristics, and the modification of the present invention could be carried out in the same manner.

This modified silica gel was processed into 4i.d.
Fill a 250mm stainless steel column with slurry,
It was used as a column for HPLC. FIG. 1 shows, as an example, a chromatogram obtained when protein-removed serum was analyzed using a column modified with SI-60 silica gel. The eluent is acetonitrile:water=
A 80:20 solution adjusted to pH 6.0 with a phosphate buffer was used. In the chromatogram, 1 is creatinine and 2 is creatine.

Example 4 3.0 g of produced silica gel SI-40 from Example 2
50 ml of toluene was added to the mixture, and to this mixture was added p-nitrobenzoyl chloride in an amount of 2.5 mmol per 1 g of silica gel, followed by reaction under reflux for 1 hour while stirring with a magnetic stirrer. After the reaction was completed, it was cooled to room temperature, and the silica gel was separated by filtration, washed three times with benzene and three times with dichloromethane, and dried overnight at 100° C. in a vacuum dryer.
Through this reaction, it was possible to further introduce 0.26 mmol of p-nitrobenzoyl groups per 1 g of silica gel.

2.0 g of the produced silica gel was added to 20 ml of 10% stannous chloride solution and 5 ml of concentrated hydrochloric acid, and the mixture was allowed to react at room temperature for 2 hours while stirring with a magnetic stirrer. This allowed 80% of the nitro groups to be reduced to amino groups.

The above method was repeated except that SI-60 was used instead of SI-40 as the silica gel produced from Example 2, and it was possible to introduce 0.23 mmol of p-nitrobenzoyl groups per 1 g of silica gel. Furthermore, approximately 80% of nitro groups could be reduced to amino groups.

The above method was repeated except that SI-100 was used instead of SI-40 as the silica gel produced from Example 2, and it was possible to introduce 0.21 mmol of p-nitrobenzoyl groups per 1 g of silica gel. Furthermore, approximately 80% of nitro groups could be reduced to amino groups.

The methods of Reference Examples 1 and 2 and Examples 1 and 2 were repeated except that alumina for column chromatography (manufactured by Merck, pore size: 90 Å, neutral, particle size: 0.063 to 0.200 mm) was used instead of silica gel. The alumina was modified. As a result of elemental analysis,
Aminopropyl groups were introduced in an amount of 0.43 mmol per gram of alumina, and for example, _E2 was bonded in an amount of 0.47 mol per mol of amino groups.

[Brief explanation of drawings]

FIG. 1 shows a chromatogram obtained when serum was analyzed by high performance liquid chromatography using a silica gel column modified according to the present invention.

Claims (1)

[Claims] 1. A step of reacting a first functional group present in the pores of the porous substance with a compound having a functional group that has a releasable group and is reactive with the first functional group; a step of forming a second functional group in the pore by eliminating the releasable group contained in the reacted compound; The compound has a size that provides steric hindrance when reacting with the first functional group in relation to the pore diameter of the porous substance, and reacts with only a portion of the first functional group. A method for modifying a porous material, characterized in that: