JP2003226517A - Surface modifying method for silica gel and adsorbent - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface modifying method for silica gel capable of modifying the surface of silica gel to ensure a property suitable for adsorbing an organic compound without breaking the porous structure of the silica gel and to provide an adsorbent having a property of adsorbing an organic compound improved by the surface modifying method. <P>SOLUTION: B type silica gel disposed in a measuring device is heated at 180°C for 2 hr while introducing dehumidified air having 0.05 g/kg absolute humidity into the measuring device to remove the adsorbed surface water from the silica gel. Evacuation is then carried out at 0.067 kPa in the measuring device and cyclohexane vapor is adsorbed until adsorption equilibrium is attained. Evacuation is further carried out at 0.067 kPa in the measuring device to obtain surface-modified silica gel with irreversibly adsorbed cyclohexane. This surface-modified silica gel is more excellent in a property of adsorbing cyclohexane than silica gel fired at a high temperature. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for modifying the surface of silica gel capable of modifying the surface of silica gel to a property suitable for adsorbing an organic compound, and the adsorption property for an organic compound improved by the surface modifying method. Regarding the adsorbent.

[0002]

2. Description of the Related Art Conventionally, as a silica gel suitable for adsorbing an organic compound gas, for example, Japanese Patent Publication No. 52-1956.
No. 0 publication describes silica gel obtained by firing at a temperature of 300 to 500 ° C. for 1 to 3 hours. According to the publication, when silica gel is calcined at a temperature of 300 to 500 ° C. for 1 to 3 hours, the silanol groups on the surface of the silica gel are changed into siloxane bonds, and as a result, silica gel suitable for adsorbing organic compound gas is obtained. Has been done.

[0003]

However, when the silica gel is calcined in the temperature range described in the above publication, the pore structure which the silica gel had before the calcining may not be maintained, and more specifically, However, there is a problem in that the pore volume, surface area, etc. of silica gel may decrease due to sintering, which causes a decrease in the adsorption performance of silica gel.

The present invention has been made to solve the above problems, and an object thereof is to modify the surface of silica gel to a property suitable for adsorbing an organic compound without destroying the pore structure of silica gel. It is intended to provide a method for modifying the surface of silica gel and an adsorbent having improved adsorption properties for organic compounds by the method for modifying the surface.

[0005]

Means for Solving the Problems and Effects of the Invention As a result of intensive studies in order to achieve the above-mentioned object, the inventors have found that the atmosphere is 0 ° C. or more and less than 300 ° C. and the relative humidity at each temperature is 1. % Remove the adsorbed water of silica gel in the controlled environment below, and then contact the silica gel with the organic compound, the organic compound will be irreversibly adsorbed on the surface of the silica gel and will not be desorbed even if vacuum is applied. Forming an adsorption layer (hereinafter, also referred to as a precoat layer), and
It has been found that the pore structure of silica gel is not broken even if the surface of silica gel is modified by such a method, and the present invention has been completed.

That is, the method for surface-modifying silica gel of the present invention removes adsorbed water of silica gel in an environment in which the atmosphere is controlled to be 0 ° C. or higher and lower than 300 ° C. and the relative humidity at each temperature is controlled to 1% or lower. By contacting the silica gel with an organic compound, the organic compound is adsorbed on the surface of the silica gel, and the surface of the silica gel is modified to have characteristics suitable for adsorbing the organic compound.

In this method for modifying the surface of silica gel, it is essential to control the relative humidity of the atmosphere to 1% or less. This humidity condition is a condition that the silica gel single molecule adsorption amount is 10% or less when the silica gel is in an equilibrium state with respect to the humidity, and it means that a small amount of relative humidity of 1% or less at each temperature is required. Not a thing. When this relative humidity exceeds 1%, the amount of monomolecular adsorption of silica gel becomes 1
It becomes difficult to achieve 0% or less, and residual adsorbed water may hinder the hydrophobization of the silica gel surface.

As a method for controlling the relative humidity of the atmosphere to 1% or less, for example, a dehumidifying body controlled to an absolute humidity or less corresponding to 1% of the saturated vapor pressure at the atmospheric temperature is continuously introduced into the container as a purge gas. It is possible to adopt a method in which the air in the container is continuously exhausted and the air in the container is continuously exhausted so that the inside of the container is always filled with the newly supplied purge gas. As a result, it is possible to prevent the humidity in the container from rising due to the heating of the silica gel and maintain the desired low humidity.

The temperature condition for heating the silica gel is 0.
The temperature is not less than 300 ° C and less than 300 ° C. If this temperature is below 0 ° C, it takes time to remove the adsorbed water adsorbed on the silica gel,
Adsorbed water may not be removed sufficiently. If the temperature is 0 ° C or higher and the relative humidity is 1% or higher, the removal of the adsorbed water can be sufficiently achieved, but it is preferably 100 ° C or higher and lower than 300 ° C.

The organic compound which is brought into contact with the silica gel is an organic compound itself to be adsorbed or an organic compound having a high affinity with the organic compound to be adsorbed. Specifically, for example, the organic compound is a hydrocarbon. Of halogenated hydrocarbons, alcohols, ethers and acetals, ketones and aldehydes, esters, polyhydric alcohols and their derivatives, carboxylic acids and their anhydrides, phenols, nitrogen-containing compounds, sulfur-containing compounds, fluorine compounds, and organosilicon compounds. It may be one kind or a mixture of two or more kinds selected from the inside.

Specific examples of hydrocarbons include amylbenzene, isopropylbenzene, ethylbenzene, octane, gasoline, xylenes, diethylbenzenes, cyclohexane, cyclohexylbenzene, cyclohexene, cyclopentane, dipentene, dimethylnaphthalene, cymene, and show brain oil. , Styrene, petroleum ether,
Petroleum benzine, solvent naphtha, decalin, decane,
Tetralin, turpentine oil, kerosene, dodecane, dodecylbenzene, toluene, naphthalene, nonane, pine oil, pinene, biphenyl, butane, propane, hexane, heptane, benzene, pentane, mesitylene, methylcyclohexane, methylcyclopentane, p-menthane, Examples thereof include ligroin and liquid paraffin.

Specific examples of the halogenated hydrocarbon include allyl chloride, 2-ethylhexyl chloride, amyl chloride, isopropyl chloride, ethyl chloride, naphthalene chloride, butyl chloride, hexyl chloride, methyl chloride, methylene chloride and o-chlorotoluene. , P-chlorotoluene, chlorobenzene, chloroform, carbon tetrachloride, 1,1-dichloroethane, 1,2-dichloroethane, 1,1-dichloroethylene, 1,2-dichloroethylene, 2,3-dichlorotoluene, 2,4-dichloro. Toluene, 2,5-dichlorotoluene, 2,6-dichlorotoluene, 3,4-
Dichlorotoluene, 3,5-dichlorotoluene, dichlorobutanes, dichloropropane, m-dichlorobenzene, o-dichlorobenzene, p-dichlorobenzene, dibromoethane, dibromobutane, dibromopropane, dibromobenzene, dibromopentane, allyl bromide , Isopropyl bromide, ethyl bromide, octyl bromide, butyl bromide, propyl bromide, methyl bromide, lauryl bromide, 1,
1,1,2-tetrachloroethane, 1,1,2,2-tetrachloroethane, tetrachloroethylene, tetrabromoethane, tetramethylenechlorobromide, 1,1,1
-Trichloroethane, 1,1,2-trichloroethane,
Trichloroethylene, 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, 1,3,5-trichlorobenzene, bromochloroethane, 1-bromo-
Mention may be made of 3-chloropropane, bromonaphthalene, bromobenzene, hexachloroethane and pentamethylenechlorobromide.

Specific examples of alcohols include n-amyl alcohol, s-amyl alcohol, t-amyl alcohol, allyl alcohol, isoamyl alcohol, isobutyl alcohol, isopropyl alcohol, undecanol, ethanol, 2-ethylbutanol and 2-ethylhexanol. , 2-octanol, n-octanol, glycidol, cyclohexanol, 3,5-dimethyl-1-hexyne-3-ol, n-decanol, tetrahydrofurfuryl alcohol, α-terpineol, neopentyl alcohol, nonanol, fusel oil, n-butanol, s-butanol, t-butanol, furfuryl alcohol, propargyl alcohol,
1-propanol, n-hexanol, 2-heptanol, 3-heptanol, n-heptanol, benzyl alcohol, 3-pentanol, methanol, methylcyclohexanol, 2-methyl-1-butanol, 3-methyl-2-butanol, 3-methyl-1-butyne-3-
All, 4-methyl-2-pentanol, 3-methyl-
1-Pentin-3-ol can be mentioned.

Specific examples of ether and acetal include:
Anisole, ethyl isoamyl ether, ethyl-t-
Butyl ether, ethyl benzyl ether, epichlorohydrin, epoxy butane, crown ethers, cresyl methyl ether, propylene oxide, diisoamyl ether, diisopropyl ether, diethyl acetal, diethyl ether, dioxane, diglycidyl ether, 1,8-cineole , Diphenyl ether, dibutyl ether, dipropyl ether, dibenzyl ether, dimethyl ether, tetrahydropyran, tetrahydrofuran, trioxane, bis (2-chloroethyl)
Ether, vinyl ethyl ether, vinyl methyl ether, phenetole, butyl phenyl ether, furan,
Furfural, methylal, methyl-t-butyl ether, methylfuran, monochlorodiethyl ether may be mentioned.

Specific examples of the ketone and aldehyde include acrolein, acetylacetone, acetaldehyde, acetophenone, acetone, isophorone, ethyl-n-butyl ketone, diacetone alcohol, diisobutyl ketone, diisopropyl ketone, diethyl ketone, cyclohexanone, di-n-propyl. Ketone, holone, mesityl oxide, methyl-n-amyl ketone, methyl isobutyl ketone, methyl ethyl ketone, methylcyclohexanone, methyl-n-butyl ketone, methyl-n-propyl ketone, methyl-n-hexyl ketone, methyl-n-heptyl ketone. Can be mentioned.

Specific examples of the ester include diethyl adipate, dioctyl adipate, triethyl acetyl citrate, tributyl acetyl citrate, allyl acetoacetate, ethyl acetoacetate, methyl acetoacetate, methyl abietate, isoamyl benzoate, and benzoic acid. Ethyl, butyl benzoate, propyl benzoate, benzyl benzoate, methyl benzoate, isoamyl isovalerate, ethyl isovalerate, isoamyl formate, isobutyl formate, ethyl formate, butyl formate, propyl formate, hexyl formate, benzyl formate, formate Methyl, tributyl citrate, silicate ester, ethyl cinnamate, methyl cinnamate, amyl acetate, allyl acetate, isoamyl acetate, isobutyl acetate, isopropyl acetate, ethyl acetate, 2-ethylhexyl acetate, cyclohexyl acetate, acetic acid -Butyl, s-butyl acetate, propyl acetate, benzyl acetate, methyl acetate, methyl cyclohexyl acetate, isoamyl salicylate, benzyl salicylate, methyl salicylate, diamyl oxalate, diethyl oxalate, dibutyl oxalate, diethyl tartrate, dibutyl tartrate, stearic acid Amyl, ethyl stearate,
Butyl stearate, dioctyl sebacate, dibutyl sebacate, diethyl carbonate, diphenyl carbonate, dimethyl carbonate, amyl lactate, ethyl lactate, butyl lactate, methyl lactate, diethyl phthalate, dioctyl phthalate, dibutyl phthalate, dimethyl phthalate, γ -Butyrolactone, isoamyl propionate, ethyl propionate, butyl propionate, benzyl propionate, methyl propionate, borate esters, dioctyl maleate, dibutyl maleate, diisopropyl malonate, diethyl malonate, dimethyl malonate, isoamyl butyrate. , Isopropyl butyrate, ethyl butyrate, butyl butyrate, methyl butyrate, and phosphoric acid esters.

Specific examples of the polyhydric alcohol and its derivative include ethylene carbonate, ethylene glycol, ethylene glycol diacetate, ethylene glycol diethyl ether, ethylene glycol diglycidyl ether, ethylene glycol dibutyl ether, ethylene glycol dimethyl ether, ethylene glycol. Monoacetate, ethylene glycol monoisopropyl ether, ethylene glycol monoethyl ether, ethylene glycol monoethyl ether acetate, ethylene glycol monophenyl ether, ethylene glycol monobutyl ether, ethylene glycol monobutyl ether acetate, ethylene glycol monohexyl ether, ethylene glycol Monomethyl ether, ethylene glycol Ether acetate, ethylene glycol monomethyl methoxymethyl ether, ethylene chlorohydrin, 1,3-octylene glycol, glycerin, glycerin triglycidyl ether, glycerol 1,
3-diacetate, glycerin dialkyl ether, glycerin fatty acid ester, glycerin triacetate,
Glycerin trilaurate, glycerin monoacetate, 2-chloro-1,3-propanediol, 3-chloro-1,2-propanediol, diethylene glycol, diethylene glycol ethyl methyl ether, diethylene glycol chlorohydrin, diethylene glycol diacetate, diethylene glycol Diethyl ether, diethylene glycol dibutyl ether, diethylene glycol dibenzoate, diethylene glycol dimethyl ether, diethylene glycol bisallyl carbonate, diethylene glycol monoethyl ether,
Diethylene glycol monoethyl ether acetate,
Diethylene glycol monobutyl ether, diethylene glycol monobutyl ether acetate, diethylene glycol monomethyl ether, cyclohexanediol, dipropylene glycol, dipropylene glycol monoethyl ether, dipropylene glycol monobutyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monomethyl ether, tetraethylene glycol , Triethylene glycol, triethylene glycol di-2-ethylbutyrate, triethylene glycol dimethyl ether, triethylene glycol monomethyl ether, triethylene glycol monomethyl ether, triglycol dichloride, tripropylene glycol, tripropylene glycol monomethyl ether, Limethylene glycol, trimethylolethane, trimethylolpropane, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,4-butenediol, propylene carbonate, propylene glycol, propylene glycol mono Ethyl ether, propylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene chlorohydrin, hexylene glycol, pentaerythritol, 1,5-pentanediol, polyethylene glycol, polyethylene glycol fatty acid ester, poly (oxyethylene-oxypropylene) derivative, Mention may be made of polypropylene glycol.

Specific examples of the carboxylic acid and its anhydride include isovaleric acid, isobutyric acid, itaconic acid, 2-ethylhexanoic acid, 2-ethylbutyric acid, oleic acid, caprylic acid,
Caproic acid, formic acid, valeric acid, acetic acid, dichloroacetic acid, lactic acid, pivalic acid, propionic acid, isobutyric anhydride, itaconic anhydride, acetic anhydride, citraconic acid, propionic anhydride, maleic anhydride, butyric anhydride, monochloroacetic acid, Butyric acid may be mentioned.

Specific examples of phenol include ethylphenol, octylphenol, catechol, xylenol, guaiacol, p-cumylphenol, cresol, m-cresol, o-cresol, p-cresol, dodecylphenol, naphthol, nonylphenol, phenol, Benzylphenol and p-methoxyethylphenol can be mentioned.

Specific examples of the nitrogen-containing compound include acetamide, acetonitrile, acetone cyanohydrin, aniline, amylamine, allylamine, isoquinoline, isobutylamine, isopropanolamines, isopropylamine, imidazole, N-ethylethanolamine, 2-ethylhexylamine, N-ethylmorpholine, ethylenediamine, caprolactam, quinoline, o
-Chloroaniline, ethyl cyanoacetate, diamylamine, diisobutylamine, diisopropylamine, diisopropylethylamine, diethanolamine, N, N
-Diethylaniline, diethylamine, diethylbenzylamine, diethylenetriamine, dioctylamine,
Cyclohexylamine, dicyclohexylamine, diphenylamine, N, N-dibutylaniline, di-n-butylamine, N, N-dibutylethanolamine, N,
N-dimethylaniline, dimethylamine, 1,3-dimethyl-2-imidazolidinone, N, N-dimethylformamide, tetraethylenepentamine, N, N, N ′,
N'-tetramethylethylenediamine, tetramethylurea, triamylamine, triethanolamine, triethylamine, trioctylamine, tri-n-butylamine, tripropylamine, trimethylamine, o-toluidine, o-nitroanisole, o-nitroaniline , Nitroethane, 1-nitropropane, 2-nitropropane, nitrobenzene, nitromethane, α-picoline, β-picoline, γ-picoline, hydrazine, pipecoline, piperazine, piperidine, pyrazine, pyridine,
Pyrrolidine, 2-pyrrolidone, N-phenylmorpholine, N-butylaniline, s-butylamine, t-butylamine, N-butylethanolamine, butyronitrile, propionitrile, propylenediamine, hexamethylphosphortriamide, heptylamine, benzonitrile , Formamide, N-methylaniline, N-methylpyrrolidone, N-methylformamide, monoethanolamine, monoethylamine, mono-n-butylamine,
Monomethylamine, morpholine, 2,4-lutidine,
2,6-lutidine can be mentioned.

Specific examples of the sulfur-containing compound include diethyl sulfate, diphenyl sulfone, dimethyl sulfoxide, dimethyl sulfate, sulfolane, thioanisole, thiophene, tetrahydrothiophene, carbon disulfide and propane sultone. Specific examples of the fluorine compound include dichlorodifluoromethane, 1,1-dichloro-1-fluoroethane, difluorobenzenes, 1,
1,2,2-tetrachlorodifluoroethane, 2,2
3,3-tetrafluoropropanol, dodecafluorocyclohexane, 1,1,2-trichlorotrifluoroethane, trichlorofluoromethane, trifluoroacetamide, ethyl 4,4,4-trifluoroacetoacetate, trifluoroethanol, trifluoroacetic acid , Trifluoroacetic acid ester, 1,1,1-trifluorodichloroethane, trifluoromethanesulfonic acid, trifluoromethylanilines, trifluoromethylpyridines, p-trifluoromethylbenzonitrile, perfluoroalkane, 2-perfluoroalkyl ethanol,
Perfluoroalkylethylene, perfluoroalkylcarboxylic acid, perfluorotetrahydrofuran, perfluorotrialkylamine, perfluorobutyltetrahydrofuran, perfluoropolyethers, fluoroanilines, fluoroisophthalonitriles, fluorophenols, fluorobenzene, hexa Fluoroacetone trihydrate, hexafluoroisopropanol, hexafluoropropylene, hexafluorobenzene, benzotrifluoride, pentafluorodichloropropane,
Mention may be made of pentafluorophenol and 2,2,3,3,3-pentafluoropropanol.

Specific examples of the organosilicon compound include silicone. These organic compounds are
One kind may be used alone, or a mixture of two or more kinds may be used as long as they are highly compatible with each other. The amount of the organic compound adsorbed may vary depending on the type of the organic compound and the physical properties of the silica gel, but is preferably 0.1 to 30% by weight based on the total weight of the silica gel after the surface modification. If this weight ratio is less than 0.1% by weight, the surface of the silica gel may not be sufficiently hydrophobized. Further, even if this weight ratio exceeds 30% by weight, the degree of the adsorption property of the organic compound does not improve so much, and if the amount of the adsorbed organic compound becomes too large, the adsorption capacity until reaching the adsorption saturation decreases. There is a risk that

The physical properties of silica gel are not particularly limited as long as they have adsorption ability. For example, the physical properties of silica gel before surface modification are 100 to 900 m ² / specific surface area.
g, pore volume 0.3 to 1.3 ml / g, average pore diameter 2
A thickness of 50 nm is desirable because it exhibits a suitable adsorption capacity for use as an adsorbent.

When removing the adsorbed water from the silica gel, it is advisable to remove the adsorbed water to a state where the adsorbed water is 10% or less of the amount of monomolecular adsorption of the silica gel. Whether or not the amount of adsorbed water is 10% or less of the amount of adsorbed single molecule of silica gel is
Calculated by the weight change before and after heating and drying under an anhydrous nitrogen purge at 180 ° C. for 2 hours or more, or measuring the weight loss by TGA (thermogravimetric analysis). T. It can be confirmed by measurement at ˜180 ° C. (under anhydrous nitrogen purge). If more than 10% of the amount of adsorbed single molecule of silica gel remains, the adsorbed water will hinder the adsorption of organic compounds.
Since the silica gel surface may not be able to be sufficiently hydrophobized, in this case, set the heating temperature higher within the range of less than 300 degrees or increase the heat treatment time to further increase the adsorption water. Should be removed. The heat treatment time is appropriately adjusted according to parameters such as the amount of adsorbed water of the raw material silica gel, the heating temperature, and the atmospheric humidity, but as a guide, it may be about 1 minute to 10 hours.

The atmosphere is not particularly limited as long as it has no adverse effect on the silica gel or organic compound used, and for example, air, oxygen gas, nitrogen gas, carbon dioxide gas, argon gas, etc. can be used.
The gases used as these atmospheres may be used alone or in a mixture of two or more.

According to the method for modifying the surface of silica gel having the above-described structure, the organic compound is irreversibly adsorbed on the surface of the silica gel to form a precoat layer having excellent adsorption characteristics for the organic compound. The surface of silica gel can be modified to have a high affinity for organic compounds. Moreover, since the adsorbed water of silica gel is removed under the environment where the atmosphere is controlled to be 0 ° C or higher and lower than 300 ° C and the relative humidity at each temperature is controlled to 1% or lower, the pore structure of silica gel is likely to be destroyed by sintering. In addition, the excellent physical properties of the silica gel before surface modification are not significantly deteriorated by the surface modification.

The inventors believe that the above-described surface modification method forms the precoat layer having the characteristics suitable for the adsorption of the organic compound as described above because of the following mechanism. A large number of silanol groups are present on the surface of silica gel, and water molecules are strongly adsorbed to the silanol groups by hydrogen bonds and the like. for that reason,
The silanol group in which water molecules have already been adsorbed has an extremely low adsorption activity to an organic compound, and it is difficult to adsorb the organic compound to the silanol group by simply contacting the organic compound with silica gel as it is.

However, in the present invention, the atmosphere is 0 ° C.
Since the adsorbed water of silica gel is removed under the environment of extremely low humidity condition in which the relative humidity at each temperature is less than 300 ° C. and the relative humidity at each temperature is controlled to be 1% or less, the water molecules adsorbed on the silanol groups are desorbed and the silanol groups are desorbed. Becomes an isolated state, and the silanol groups on the surface of silica gel have a high adsorption activity for organic compounds. Moreover, since the temperature condition for heating the silica gel is a relatively low temperature condition of 0 ° C. or more and less than 300 ° C., most of the silanol groups on the surface of the silica gel do not change to siloxane bonds, and as a result, many silanol groups are used. The group effectively functions as an adsorption point of the organic compound. Therefore, in this state,
When silica gel is contacted with an organic compound, the organic compound is strongly adsorbed by a large number of active silanol groups, and as a result, the surface of silica gel is surface-modified by the organic compound and modified to have properties suitable for adsorbing the organic compound. It will happen.

In this respect, the conventional technique of heating under a relatively high temperature condition of 300 ° C. to 500 ° C. changes most of the silanol groups on the surface of silica gel into siloxane bonds and loses the silanol groups themselves. This is a big difference from the fact that the hydrophilicity of the silica gel surface is reduced and the relative result is that the hydrophobicity is increased.
That is, if most of the silanol groups on the surface of silica gel are changed to siloxane bonds, the silanol groups cannot function as adsorption points for organic compounds, so it is difficult to improve the adsorption characteristics for organic compounds as much as the present invention. Become.

As described above, according to the method for modifying the surface of silica gel of the present invention, the surface of silica gel can be modified to a surface having a high affinity for organic compounds, and the silica gel before surface modification can be modified. The excellent physical properties possessed by (1) will not be significantly deteriorated by the surface modification. Therefore, if a part or all of the adsorbent is composed of this modified silica gel, an adsorbent suitable for adsorbing an organic compound gas or an organic solvent can be obtained.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described with reference to some specific examples. [Example 1] B-type silica gel (specific surface area 46
2 m ² / g, pore volume 0.78 ml / g, average pore diameter 6.8 nm) were prepared, and while introducing dehumidified air with an absolute humidity of 0.05 g / kg into the measuring device in which this sample was installed, Was heated at 180 ° C. for 2 hours to remove surface adsorbed water from the sample.

A part of this sample was taken out, heated and dried at 180 ° C. for 2 hours or more under an anhydrous nitrogen purge, and the amount of surface adsorbed water adsorbed on the sample was calculated from the weight change before and after that. The water content was 0.22% by weight, and the surface adsorbed water was removed up to about 2% of the amount of adsorbed monomolecule.

After that, in the measuring device, 0.067 k
The first vacuuming was performed at Pa, and the adsorption isotherm of cyclohexane was measured. The adsorption isotherm of cyclohexane is measured at a sample tube temperature of 30 ° C. using an apparatus conforming to a volumetric measurement device (adsorption science, Seiichi Kondo, Tatsuo Ishikawa, Ikuo Abe, Maruzen Co., Ltd., p. 148-153). did. Hereinafter, this measurement is referred to as measurement 1.

Then, for the sample in adsorption equilibrium with cyclohexane vapor in Measurement 1, 0.067 kPa
A second vacuum was drawn with and the adsorption isotherm of cyclohexane was measured. Hereinafter, this measurement is referred to as measurement 2. Then, for the sample in adsorption equilibrium with the cyclohexane vapor in Measurement 2, the third vacuum evacuation was performed at 0.067 kPa, and the adsorption isotherm of cyclohexane was measured. Hereinafter, this measurement is referred to as measurement 3.

Then, for the sample in adsorption equilibrium with cyclohexane vapor in Measurement 3, 0.067 kPa
Was vacuumed for the fourth time and the adsorption isotherm of cyclohexane was measured. Hereinafter, this measurement is referred to as measurement 4. that's all,
The adsorption isotherms obtained by measurement 1 to measurement 4 are shown in FIG. In FIG. 1, the horizontal axis represents the relative pressure P / P0 of cyclohexane vapor (P: cyclohexane vapor pressure, P0: cyclohexane saturated vapor pressure), and the vertical axis represents the amount of cyclohexane adsorbed per 1 g of the sample V [ml (liq.) / g].

[Comparative Example 1] As a sample, the same B as in Example 1 was used.
-Type silica gel (specific surface area: 462 m ² / g, pore volume: 0.
78 ml / g, average pore size 6.8 nm) was prepared, and this sample was baked at 800 ° C. to partially dehydrate and condense surface silanol groups, thereby converting into siloxane bonds.

Then, in the measuring device, 0.067 k
The first vacuuming was performed at Pa, and the adsorption isotherm of cyclohexane was measured. Hereinafter, this measurement is referred to as measurement 1. After that, the sample that was in adsorption equilibrium with cyclohexane vapor in Measurement 1 was subjected to a second vacuum evacuation at 0.067 kPa, and the adsorption isotherm of cyclohexane was measured.
Hereinafter, this measurement is referred to as measurement 2.

After that, for the sample in the adsorption equilibrium with the cyclohexane vapor in Measurement 2, 0.067 kPa
Vacuum suction was performed for the third time and the adsorption isotherm of cyclohexane was measured. Hereinafter, this measurement is referred to as measurement 3. After that, the sample that was in adsorption equilibrium with the cyclohexane vapor in Measurement 3 was subjected to a fourth vacuum evacuation at 0.067 kPa, and the adsorption isotherm of cyclohexane was measured. Hereinafter, this measurement is referred to as measurement 4.

Then, for the sample in adsorption equilibrium with cyclohexane vapor in Measurement 4, 0.067 kPa
The vacuum was evacuated for the fifth time and the adsorption isotherm of cyclohexane was measured. Hereinafter, this measurement is referred to as measurement 5. that's all,
The adsorption isotherms obtained by measurement 1 to measurement 5 are shown in FIG. In FIG. 2, the horizontal axis represents the relative pressure P / P0 of cyclohexane vapor (P: cyclohexane vapor pressure, P0: cyclohexane saturated vapor pressure), and the vertical axis represents the cyclohexane adsorption amount V [ml (liq.) / Per 1 g of the sample. g].

[Comparison between Example 1 and Comparative Example 1] Example 1
From the measurement results of Comparative Example 1, it can be seen that there is a clear difference between the cyclohexane adsorption isotherms. In particular, for Example 1 and Comparative Example 1, the adsorption isotherms (measurement 1) measured for the first time are compared. Since the surface of silica gel is covered with silanol, it normally exhibits hydrophilicity, and the adsorption amount of adsorption isotherm is unlikely to increase for cyclohexane, which is a hydrophobic substance. However, in Example 1, a large amount of adsorption was secured since the adsorption isotherm measurement started from the first time. On the other hand, in Comparative Example 1, the adsorption isotherm does not rise unless adsorption / desorption is repeated several times, and the saturated adsorption amount is low. Further, since the rising slope of the adsorption amount when P / P0 is 0.4 to 0.8 is low, Example 1 is superior when adsorption / desorption on this curve is repeated. From this, it is considered that Example 1 has higher activity to the organic compound than Comparative Example 1. The reason why such a result is obtained is that the degree of hydrophobization is higher in Example 1,
Also, it is considered that the reduction in surface area and pore volume due to sintering has not occurred, and it is considered that both of these factors are probably acting.

Further, from the results of measurement 1 to measurement 4 in Example 1, it can be seen that there is no great change in the adsorption property for cyclohexane even if the evacuation is repeated. [Comparative Example 2] As a sample, the same B-type silica gel as in Example 1 (specific surface area 462 m ² / g, pore volume 0.78 ml /
g, average pore size 6.8 nm), a part of this sample was taken out, heated and dried at 180 ° C. for 2 hours or more under anhydrous nitrogen purge, and adsorbed to the sample due to weight change before and after that. As a result of calculating the amount of surface-adsorbed water, the water content was 1.2% by weight, and the surface-adsorbed water was 1% of the amount of adsorbed monomolecule.
It was about 0.9%.

The sample was evacuated at 0.067 kPa in the measuring device, and the cyclohexane adsorption isotherm was measured. The adsorption isotherm of Comparative Example 2;
The adsorption isotherm obtained by Measurement 1 of Example 1 above was
Also shown in FIG.

[Comparison of Example 1 (Measurement 1) and Comparative Example 2] When Example 1 (Measurement 1) and Comparative Example 2 are compared, each relative of Comparative Example 2 is compared with Example 1 (Measurement 1). It can be seen that the amount of cyclohexane adsorbed at pressure is low. The weight ratio of water to the whole sample of the sample of Comparative Example 2 was 1.2% by weight, which corresponds to 10.9% of the amount of adsorbed single molecule of silica gel. Therefore, it is considered that the residual adsorbed water hindered the hydrophobicity of the silica gel surface, and the adsorption activity for cyclohexane became low.

Example 2 As a sample, A-type silica gel (specific surface area 612 m ² / g, pore volume 0.37 ml /
g, average pore diameter 2.1 nm), and while introducing dehumidified air with an absolute humidity of 0.05 g / kg into the measuring device in which this sample is installed, heat the sample at 180 ° C. for 2 hours to remove it from the sample. Surface adsorbed water was removed.

A part of this sample was taken out, heated and dried at 180 ° C. for 2 hours or more under anhydrous nitrogen purge, and the amount of surface-adsorbed water adsorbed on the sample was calculated from the weight change before and after the drying. The water content was 0.13% by weight, and the surface-adsorbed water was removed up to about 2% of the amount of adsorbed monomolecule.

Then, the adsorption isotherm of CFC gas (HFC-125) was measured. The measuring method is the same as in Example 1. Hereinafter, this measurement is referred to as measurement 1. Further, the adsorption isotherm of chlorofluorocarbon was measured for the second vacuumed sample. Hereinafter, this measurement is referred to as measurement 2.

FIG. 4 shows the adsorption isotherms obtained by the above measurement 1 and measurement 2. In FIG. 4, the abscissa represents the pressure of fluorocarbon [kPa], and the ordinate represents the adsorption amount of fluorocarbon V [ml (liq.) / G] per 1 g of the sample. From the result of measurement 1, the silica gel in which the surface silanol group was in an active state showed a good adsorption ability from a low vapor pressure,
At atmospheric pressure (101.32 kPa), it was confirmed that 0.15 ml of CFC gas could be adsorbed per 1 g of silica gel.

From the results of measurement 2, it can be seen that the amount of adsorption of CFC gas at each pressure was larger than that in measurement 1. This tendency was particularly remarkable on the low pressure side. This is because silica gel once having a chlorofluorocarbon saturation adsorption state has a chlorofluorocarbon adsorption layer (precoat layer) formed on its surface, and the fluorocarbon gas is adsorbed a second time in a state where the fluorocarbon surface has been surface-modified. It is thought that the affinity with

[Effects] As described above, according to the method for modifying the surface of silica gel as described in Examples 1 and 2, the organic compound is irreversibly adsorbed on the surface of the silica gel and the organic compound Since the precoat layer having characteristics suitable for adsorption is formed, the surface of silica gel can be modified to have a high affinity for organic compounds.
Moreover, since the temperature condition of the heat treatment performed to remove the adsorbed water is 100 ° C. or more and less than 300 ° C.,
The pore structure of silica gel is not destroyed by sintering, and the excellent physical properties of silica gel before surface modification are not significantly deteriorated by surface modification.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above specific embodiment.
Other than this, it can be implemented in various forms. For example, in the above embodiment, cyclohexane and freon were shown as examples of the organic compound, but even when an organic compound other than these is targeted for adsorption, by applying the present invention, the organic compound to be targeted for adsorption is used. It is possible to obtain silica gel having high affinity.

[Brief description of drawings]

1 is a graph showing adsorption isotherms for Example 1. FIG.

2 is a graph showing an adsorption isotherm for Comparative Example 1. FIG.

FIG. 3 is a graph showing an adsorption isotherm for Comparative Example 2.

FIG. 4 is a graph showing adsorption isotherms for Example 2.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masakazu Suzuki             2-1846 Kozoji-cho, Kasugai City, Aichi Prefecture             Within Fuji Silysia Chemical Ltd. F-term (reference) 4G066 AA22B BA23 BA25 BA26                       CA25 CA27 CA32 CA33 CA51                       CA52 CA56 FA21 FA37                 4G072 AA28 CC10 GG03 HH19 LL02                       LL04 LL05 MM35 QQ06 RR07                       UU11

Claims (7)

[Claims] 1. Adsorbed water of silica gel is removed under an environment in which the atmosphere is controlled to 0 ° C. or higher and lower than 300 ° C. and the relative humidity at each temperature is controlled to 1% or lower, and then the silica gel and the organic compound are brought into contact with each other. By adsorbing the organic compound on the surface of the silica gel to modify the surface of the silica gel to a property suitable for adsorbing the organic compound. 2. The organic compounds are hydrocarbons, halogenated hydrocarbons, alcohols, ethers and acetals, ketones and aldehydes, esters, polyhydric alcohols and their derivatives, carboxylic acids and their anhydrides, phenols, nitrogen-containing compounds, The method for modifying the surface of silica gel according to claim 1, which is one or a mixture of two or more kinds selected from a sulfur-containing compound, a fluorine compound, and an organic silicon compound. 3. The silica gel according to claim 1, wherein the adsorption amount of the organic compound is 0.1 to 30% by weight based on the total weight of the silica gel after surface modification. Surface modification method. 4. The physical properties of the silica gel before surface modification have a specific surface area of 100 to 900 m ² / g and a pore volume of 0.3 to 1.
The method for modifying the surface of silica gel according to any one of claims 1 to 3, wherein the method has a pore size of 3 ml / g and an average pore diameter of 2 to 50 nm. 5. When removing the adsorbed water from the silica gel, the adsorbed water is adsorbed in an amount of 10 per molecule of the silica gel.
The method for modifying the surface of silica gel according to any one of claims 1 to 4, characterized in that the surface is removed to a state of not more than%. 6. The atmosphere according to claim 1, wherein the atmosphere is one or a mixture of two or more selected from air, oxygen gas, nitrogen gas, carbon dioxide gas, and argon gas. The method for modifying the surface of silica gel according to any one of claims. 7. A part or all of silica gel whose surface has been modified to have a property suitable for adsorbing the organic compound by the method for modifying a surface of silica gel according to any one of claims 1 to 6. An adsorbent characterized in that