DE2426306A1 - PROCESS FOR CHEMICAL MODIFICATION OF SOLID SURFACES - Google Patents

Description

Dr. Imrich Sebestian
6602 Duduieiler

Process for the chemical modification of solid surfaces

The invention relates to the chemical modification of the reactive solid body surfaces with organosilicon Reagents. Solids modified in this way are used, for example, as catalysts, sorbents, etc.

The catalysts accelerate chemical reactions; Among other things, the reaction conditions, such as temperature, Pressure, mitigated.

In the case of sorption processes, the sample substances interact with the sorbent. They can also be irreversibly sorbed and thus remain on the sorbent (selective sorption). In the case of reversible sorption, different sample substances, depending on their affinity, have different residence times on the sorbent. This fact is used e.g. in chromatographic separations. The separation takes place in a separation column which is filled with a suitable sorbent (so-called stationary phase) and from a carrier medium (gas or liquid, so-called mobile phase), which causes the transport of the sample components to flow through the column will.

The use of chemically modified solids offers the possibility of varying the selectivity of the sorbent for such processes. The manufacture is done by chemical Binding of functional groups to the solid surface.

Several methods of modifying solids have been devised. In DT-PS 1 902 226, the esterification is of silicon dioxide with substituted alcohols. The organic molecules are through to the surface of the solid * Si-0-C * bond bound, which is known to be insufficient is hydrolysis and temperature stable

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According to the German patent application P-2236862.3-41, the silanol groups are converted from silicon dioxide (eg silica gel) into the = Si-Cl groups by chlorination. In the second stage, these reactive groups are reacted with amines to form the '= Si-N = bond. Such products are only stable to hydrolysis in a pH range of 4-8, that is to say they can only be used to a limited extent in practical application. It is not possible to regenerate the SO "H groups which are essential for catalysis, ion exchange and chromatography (-SO Na + HCl -» - SO H + NaCl), because dilute acids are pH-linked for regeneration <■ 1 can be used. In liquid chromatographic separations, buffer solutions are often used whose pH is outside the stability limits of such stationary phases. Under these conditions the 5Si-N = bond is quickly cleaved.

Another method for modifying inorganic solids is described in German patent application P 2313073.6. Solids are reacted with alkylchlorosilanes After this l / out, then be introduced by halogenation in the groups attached to the surface of the solid alkyl chains halogen atoms "A and subsequently substituted by functional groups. It is known that the ESi-CS bond is particularly stable to hydrolysis and temperature. Since the organic molecules are bound to the surface by this bond, such modified solids are characterized by great stability. A disadvantage of this method is the large amount of time required for such conversions; the flodification reactions take more than ten days to complete. Another disadvantage is that the functional groups are bonded to the solid via alkyl chains through multistage reactions on the surface of the solid. In the case of multistage reactions, however, the yields are lower, so that the desired maximum surface concentration of functional groups cannot be achieved by this process.

The aim of this invention are chemically surface-modified solids, the advantage over known chemically modified solids have that they are hydrolysis and temperature stable and through large surface concentration of functional groups.

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Such chemically modified solids can be used, for example, as catalysts, Ion exchangers or sorbents can be used.

It has now been found that such chemical modification of the reactive Solid surface is achieved when looking at the surface existing hydroxyl groups with substituted alkyl, aryl, or aralkylalkoxysilanes under the action of which converts catalysts.

According to the invention, the dried solids with a reactive Surface suspended in a dried solvent (e.g. toluene, dimethylformamide, etc.) and treated with alkoxysilane and catalyst ('or sulfonic acid) added. The suspension will last for a few hours Maintained at elevated temperature (e.g. 110 C) with exclusion of air moisture. The solids with modified surfaces are filtered off, freed from excess alkoxysilane, catalyst and solvent by washing with suitable solvents and dried.

It was found that the chemical modification of the reactive Solid surfaces with the inert substituted alkoxysilanes are accelerated with the aid of catalysts and the reaction temperature is reduced. This makes it possible to also use such silanes to use for the modification reactions that contain functional groups.

Organic amines and have proven to be catalytically active reagents Sulfonic acids proved. For steric reasons, primary amines are preferred (e.g. n-butylamine, ethylenediamine, etc.). Of sulfonic acids become both aliphatic (e.g. dodecylsulfonic acid) and aromatic (e.g. benzenesulfonic acid) is used.

According to the invention, substituted for the modification reactions Alkyl, aryl, or aralkylalkoxysilanes are used. Among these organosilicon Compounds are understood as reagents in which the functional groups are attached to the silicon atom via alkyl, aryl and aralkyl radicals are bound. In addition, there is at least one on the silicon atom Alkoxy group (e.g. methoxy, ethoxy group) attached.

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From the large number of possible organosilicon The following reagents are mentioned:

3-cyanopropyltriethoxysilane, bis- (N, N, -dimethyl 3-aminopropyl) -dimethoxysilane, 4-aminobutylmethyl diethoxysilane, 3-wercaptopropylmethyldimethoxyailane, Octadecyldimethylpropoxysilane, (p-nitrophenyl-N -aminomethyl) dimethylethoxysilane, dimethoxymethylsilyl (4-butylsulfonic acid Na-Salz), (N, N, N, Trimethylemonium-S-propylhydrochlorideJ-methyldimethaxysilane, 3-phenylpropylraethyldiinethoxysilane, £ N-2 (aminoethyl) -3-afflinopropyl] trimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane etc. However, this list is by no means limiting.

As particularly suitable materials with a reactive surface have proven the following:

Silica gel, metal oxides (Al ₂ O ₃ , TiO «, ZrO-), porous glass, carrier materials (glass spheres, glass plates, ground bricks, etc.) that have a porous silicon dioxide or PTFE layer on the surface, etc.

The solids modified according to this invention contain at the Surface via the hydrolysis and temperature stable S-Si-CS bond bound organic molecules »By introducing different functional groups, the chemical composition of the surface and thereby the selectivity of the modified solids varies. This is particularly advantageous when using such products as sorbents, e.g. in chromatography, environmental protection, ion removal ; exchange or as catalysts. Since the functional groups according to the invention in a one-step reaction and under mild reaction conditions are bound to the solid surface, their surface concentration is very high.

In many cases it is still possible to use the functional groups j which are bound to the surface of the solid, in a subsequent To implement the reaction further and thereby introduce new functional groups. The selectivity and the sorption properties of the modified solid can thus additionally be changed in the desired manner.

The chemical modification of solid surfaces according to the invention is explained by the following examples.

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Example 1.

20 g of silica gel with a specific surface area of 310 m / g Dried for 12 hours at 150 C, with 100 ml of dried xylene, 5 ml 3-cyanopropylmethyl diethoxysilane and 1 ml ethylenediamine (catalyst) added and for 5 hours with exclusion of humidity 115 C held.

The modified silica gel is filtered off with methylene chloride, Rethanoi, methanol-water (lsi), methanol and diethyl ether several times

washed and dried in vacuo at 140.degree.

The solid surface is hydrophobic (poorly wettable with water)

and contains chemically bound -CN groups.

Example 2.

20 g of dried silica gel are mixed with 100 ml of toluene, 5 ml of bis- (N, N-dimethyl-3-aminopropyl) dimethoxysilane and 2 ml of butylamine (catalyst) added and with exclusion of humidity for 3 hours at 110 ° C held. The product is washed and dried analogously to Example 1.

The surface of the solid is basic due to the bound -N (CH “) ₂ groups and the product is an anion exchanger. '■

Example 3.

20 g of dried silica gel are reacted with 5 ml of 3-mercaptopropylmethyldimethoxysilane according to Example 1, washed and dried. By oxidation (e.g. with HNO-) the surface-related -SH groups converted into -S0_H groups. The product is a strong one acidic cation exchanger.

Example 4.

20 g of dried aluminum hydroxide are dried with 100 ml Dimethylformamide, 4 g (N, N, N trimethyl-3-ammoniumpropyl) -methyldimethoxy- ; silane chloride and 3 ml dipropylamine (catalyst) added and 5 hours Maintained at 110 ° C. for a long time with exclusion of air humidity, then analogously

{Example 1 washed and dried.

The product contains surface-R (CfO-Cl groups and is a strongly basic anion exchanger

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Example 5.

20 g of porous SiO-coated glass beads with a specific surface area of 15 m / g are mixed with 100 ml of dried dimethyl sulfoxide, 3 g of dimethoxymethylsilyl 4-fautylsulfonic acid, sodium salt and 0.5 g of benzenesulfanic acid (catalyst), then reacted, washed and dried Example 1.

The product is washed with 1 N hydrochloric acid and water and is a strongly acidic cation exchanger.

Example 6.

20 g of dried porous glass with a specific surface area of 60 m / g are mixed with 100 ml of dimethylformamide, 4 g of dimethoxymethylsilyl-3 propylisothiouronium chloride and 1 ml of ethylenediamine (catalyst) and reacted according to Example 1, washed and dried. The propylisothiouronium chloride groups bound to the surface are converted into propylsulfonic acid groups by oxidation (eg with HNO, H Q). The product is a strongly acidic cation exchanger.

Example 7.

A glass plate (7x5 cm) covered with titanium hydroxide is heated to 150.degree Dried for 12 hours, with 50 ml of xylene, 3 g of (p-nitrophenyl N-aminomethyl) -dimethylethoxysilane and 2 ml of benzylamine (catalyst) are added and the mixture is kept at 120 ° C. for 8 hours with exclusion of atmospheric moisture.

Washing out and drying is carried out according to Example 1.

Such surface-porous plates with chemically bound nitro groups are used in thin layer chromatography.

Example 8.

20 g of dried porous glass with a specific surface area of 150 m / g are reacted with 5 g of N-2 (aminoethyl) -3-aminopropyl trimethoxysilane analogously to Example 1, washed and dried. The product is treated with 100 ml of ethanol, 5 g of chloroacetic acid and 5 ml of tripropylamine (HCl-binder) and 10 hours boiled under reflux, then with methanol, pale, methanol several times and dried in vacuo at 60 ⁰ C dried.

The modified solid body contains ₇ chemically bound groups on the surface, which bind the heavy metal ions.

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Example 9.

20 g of dried zirconium hydroxide are mixed with 100 ml of cumene,
5 ml of 3-phenylpropyldimethylpropaxysilane and 1 ml of hexamethylenediamine (catalyst) were added and the mixture was kept at 130 ° C. for 10 hours with exclusion of atmospheric moisture. Wash out and dry afterwards
Example 1. The modified solid surface is hydrophobic and contains chemically bound phenylpropyl groups,

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Claims (12)

Claims. 1) Process for chemical modification of the reactive Solid surfaces, characterized in that alkyl, aryl or aralkyl radicals are chemically bonded to the solid surface ii / earths that carry functional groups. 2) l / experience according to claim 1, characterized in that daQ for Modification of alkyl, aryl, or aralkylalkoxysilanes are used, which by functional groups, preferably in (i> -position, are substituted. 3) Process according to claims 1 and 2, characterized in that catalysts are used in the modification reactions. 4) Method according to claims 1 to 3, characterized in that that amines, preferably primary amines, are used as catalysts. 5) Process according to claims 1 to 3, characterized in that organic sulfonic acids are used as catalysts. 6) Process according to claims 1 to 5, characterized in that that substituted alkyl, aryl, or aralkyl- methoxysilane can be used. 7) Process according to claims 1 to 5, characterized in that substituted alkyl, aryl, or aralkylethoxysilanes for the modification be used. 8) Method according to claims 1 to 7, characterized in that that one in the modified and functional group-containing solids in a manner known per se further functional groups introduces. 9) Process according to claims 1 to 8, characterized in that as functional groups, for example -SO ₃ H, -SH, -OH, -CN, -NO ₂ , -COOH, -SO-R, -CH-CH, - CH = CH, -NR, - ^ ₃ * -0-R, -SR groups introduced where R represents an alkyl chain. 509849/0843 10) l / experienced according to claims 1 to 9, characterized in that that silica gel, porous and non-porous glass are used as starting material with a reactive surface. 11) Method according to claims 1 to 9, characterized in that that a metal oxide is used as a starting material with a reactive surface udrd. 12) Method according to claims 1 to 9, characterized in that that a gas-impermeable solid with a reactive, porous surface is used as the starting material 509849/0843