DD283701A7 - METHOD AND DEVICE FOR PRODUCING ORGANICALLY MODIFIED SILICA TAGS - Google Patents

Abstract

The invention relates to the modification of silica gels by reaction with alkyl or arylalkoxysilanes. The products are suitable as adsorbents, enzyme carriers and as compact phases for chromatography. According to the invention, the silica gels are heated to temperatures of 200 to 360 ° C. with an excess of the liquid silanes covering the entire gel, then percolated with washing liquids and dried. The reaction is carried out in a heatable pressure reactor having a diameter / height ratio of 1: 2.5 to 1: 6, provided on the lid and bottom with lockable Produktintrags- Produktaustragsoeffnungen and conically narrowed towards the lower OEffnung and laterally on the cone a bottom valve protected by a stainless steel frit with column sieve {organically modified silica gels; Alkylalkoxysilanes arylalkoxysilanes; adsorbents; Enzymtraeger; Compact phases; chromatography; Silanueberschusz; Pressure reactor; Diameter / Hoehenverhaeltnis}

Description

For this 1 page drawing

Field of application of the invention

The invention relates to a method and a device for modifying silica gels with liquid alkoxysilanes, which carriers or compact phases can be produced, which can be generally used in chromatography and are characterized in particular by high purity and high degrees of coverage of directly bonded hydrocarbon radicals.

Characteristic of the known technical solutions

Silica gels can be derivatized with halosilanes, alkoxysilanes or otherwise by organic radicals (DE-OS 2313073).

Mostly used solutions of chlorosilanes in organic solvents, but also operations with gaseous silanes are known (DE-OS 1951620). Chlorine silanes are very reactive, highly moisture-sensitive products. They require removal of the hydrogen chloride during the reaction, ζ. B. by the addition of bases. The resulting salts make longer washing procedures necessary without the guarantee of complete cleaning is given.

Alkyl or arylalkoxysilanes are inert and require the addition of catalysts for the reaction in the previous use of solvents (H. Engelhardt, P. Orth, J. Liquid Chromatography 10 (1987) 1999-2022).

Often, however, the degrees of conversion achieved are markedly worse than with halosilanes, and the residual removal of the catalyst additives can also cause difficulties. Without addition of catalyst, only very low degrees of conversion have hitherto been achieved with alkoxysilanes on silica gels.

Object of the invention

The aim of the invention is the derivatization of silica gels to form stable Si-C bonds by reaction with alkyl or arylalkoxysilanes without the use of solvents and catalysts, wherein all process steps in an apparatus are carried out in succession without intermediate isolation of the products.

Explanation of the essence of the invention

The object is to develop a method and an apparatus for producing organically modified silica gels with the aid of alkyl or arylalkoxysilanes.

The object is achieved by a process for preparing organically modified silica gels by reacting them with alkyl

or Arylkoxysilanen according to the invention achieved in that the silica gel with a bndeckenden the entire gel excess of the liquid silanes heated to temperatures of 200 to 36O ⁰ C, then lollies under pressure with Waschf lüscigkeiten and finally dried under passage of inert gas. Depending on the reactivity of the silane, it is advantageous to choose temperatures between 200 ⁰ C and 360 ⁰ C, wherein both mono- and di- and trifunctional Aikoxysilane with unbranched or branched, short or long Aikylketten, including C-20, and can use with aryl radicals. All silanes serve as a reaction component and for receiving the reaction products, so that the addition of solvents unterhlb.bt.

Furthermore, it is advantageous to use as washing liquids methanol and ethanol or optionally toluene i.

Reaction procedure and washing procedure according to the invention in a pressure reactor (see scheme) realized with up to 400 ⁰ C ausgelegter heating, the diameter-height behaves never about 1: 2, B to 1: 6 amounts, so that reaction and washing procedure can be performed without stirrer in a row, the latter under quasi-chromatographic conditions. After unscrewing the lid, the reactor is charged with silica gel and silica and, after screwing on the lid, flushed with inert gas. With valves closed, heat to the prescribed temperature while under pressure. Then it is expanded through the outlet valve, wherein the excess silane flows out. In front of the outlet valve there is a stainless steel frit with support plate underneath. After opening the inlet valve, the gel is purified by pumping through the appropriate solvent, which can be heated by switching on the heater. Thereafter, inert gas is passed through the reactor. The gel dried by inert gas on this catfish can be removed ready for use from the reactor through the emptying device. The inventive method in conjunction with the device according to the invention allows a very simple production of hydrocarbon radicals modified silica gels, depending on the choice of conditions low and high Monoschlchtbedeckungsgrade up to the theoretically possible maximum coverage as well as polymer crosslinked surface coatings produce high chromatographic effectiveness.

Auiführungsbelsplelo

The execution of the method according to the invention takes place in the device represented by the principle drawing. The pressure reactor 1 is charged after unscrewing the reactor cover 2 with the reaction mixture 3. After the Wiaderanschrauben the lid 2 and open the valves 4 and 5 is purged with inert gas from the container β. If the valves are closed, then heating 7 will be heated to the intended temperature. Then it is relaxed via the outlet valve 8 and the ausf Ik ßende silane collected. The modified silica gel is retained by the stainless steel frit with support sieve plate 9. After opening the valve 10 is pumped through the silica gel with the pressure pump 11 to wash out the silane solvent, wherein the solvent can be heated by switching on the heater 7. Thereafter, valve 10 is closed and valve 5 is opened and the gel is dried in an inert gas stream.

The dried gel is then removed from the reactor 1 through the emptying device 12. With the control gauge 13, the pressure prevailing in the reactor can be controlled in each case.

example 1

0.5 kg of silica gel of grain size 10 μπι and a specific surface area of 200 mVg were filled in the pressure reactor and treated with 1.2 liters of octyltriethoxysilane. It was then purged with oxygen-free inert gas and heated to 240 ° C for 6 hours. After cooling, the excess silane was vented through the bottom valve, after which methanol was pumped through the fill for 5 hours until all the leachable silane was removed. It was flushed with inert gas when the bottom valve was open and heated to 80 to 100 ° C overnight. By removing the bottom screw of the reactor, the dry, ready-to-use gel was obtained. It had a carbon content of 8.4% (mass) and a coverage of 2.4 residues per nm ^! and showed excellent chromatographic properties. The found reduced ground level was 3.2 on average.

Example 2

0.5 kg of silica gel of particle size 10 (im and a specific surface area of 340 mVg were charged into the pressure reactor and admixed with 1.2 liters of octadecyltriethoxysilane, followed by purging with oxygen-free inert gas and heating to 260 ^° C. for 8 hours Drain the excess silane through the bottom valve, then sequentially pump toluene, ethar oil, and methanol at boiling heat for a total of 5 hours, rinse with inert gas while the bottom valve is open, and heat overnight at 80-100 ° C. By removing the bottom screw of the reactor It had a carbon content of 16% (mass) and a coverage of 1.5 Re ^ cn per nm ² and showed excellent chromatographic properties.

Example 3

0.5 kg silica gel of particle size 10 in the \ and a specific surface area of 380 MVG were charged in the tubular reactor andwith 1.2 liters Octvl-dimethyl-monomethoxysilan added. Thereafter, it was purged with oxygen-free inert gas and heated to 200 ⁰ C for 24 hours. After cooling, the draining of the excess silane through the bottom valve followed

Methanol was pumped through the charge for 3 hours until all the leachable silane was removed. It was opened Flushed bottom valve with inert gas and heated to 80 to 100 ⁰ C overnight. By removing the ground screw of the Reactor received the dry, ready-to-use gel. It had a carbon content of 12.3% and a degree of coverage

of 2.0 residues per nm ² and showed excellent chromatographic properties. The found reduced Bodenhöhebetrug mean 3.2.

The experiment was repeated in the same way, with the heating temperature was set to 36O ⁰ C. The product gave

the same carbon content, i. the surface coverage of the carrier remained constant.

Example 4

0.5 kg of silica gel with a particle size of 7 μm and a specific surface area of 45 μgVg were introduced into the pressure tube reactor and admixed with 1.2 liters of octyltriethoxysilane. It was then purged with oxygen-free inert gas and heated for 8 hours at 335 ° C. After cooling, the excess silane was vented through the bottom valve, after which methanol was pumped through the packing for 5 hours until all the leachable silane was removed Flushed bottom valve with inert gas and heated overnight at 80 to 100 ⁰ C. Removing the bottom screw of the reactor to obtain the dry, ready-to-use gel It had a carbon content of 25.4% on the gel showed excellent chromatographic properties with one over Example 1 to 3 markedly altered selectivity

Trial, the heating temperature was set to 360 ⁰ C. The carbon content could be increased up to 31.3% (mass).

Example 5

2.5 kg of silica gel of particle size 9 pm and a specific surface area of 38 μmVg were introduced into the pressure tube reactor and mixed with 6 liters of phenyltrimethoxysilane. The mixture was flushed with oxygen-free inert gas and heated at 210 ° C. for β hours. After cooling, the excess silane was vented through the bottom valve, after which methanol was pumped through the fill for 4 hours until all the leachable silane was removed. It was flushed with an open bottom valve with inert gas and heated to 80 to 100 ⁰ C overnight. Removal of the bottom vent of the reactor gave the dry, ready-to-use gel. It had a carbon content of 11.1%, a coverage of 2.5 residues per nm ² and excellent chromatographic properties.

Claims (4)

1. A process for the preparation of organically modified silica gels by reacting the same with alkyl or arylalkoxysilanes, characterized in that the silica gel with an entire gel covering excess of liquid silanes heated to temperatures of 200 to 36O ⁰ C, then percolated under pressure with washing liquids and Finally, dried under passage of inert gas. 2. The method according Anpruch 1, characterized in that one uses both mono-, di- and trifunctional alkoxysilane with different, mixed, hydrocarbon substituents. 3. The method according to claim 1, characterized in that preferably used as percolation liquids methanol, ethanol and toluene. 4. Apparatus for producing organically modified silica gels, consisting of a; η heated to 400 ⁰ C pressure reactor, characterized in that this has a diameter / height ratio of 1: 2.5 to 1: 6, is provided on the lid and bottom with closable Produktintrags- and Produktaustragsöffnungen, conically narrows towards the lower opening and on the side of the cone carries a bottom valve, which is protected by a stainless steel frit with supporting sieve.