CS200997B1 - Method of preparing spherical particles of silica - Google Patents

Description

The present invention relates to a novel process for the preparation of spherical silica particles of controlled size and controlled pore size, particularly useful for high pressure and gel permeation chromatography.

Subject of MS. No. 179184 is a process for preparing precision spherical silica particles of controlled size and controlled pore size by polymerizing free silicic acid obtained by acidifying solutions of alkali metal silicates in an organic solvent such as hexane or a mixture of hexane and carbon tetrachloride to acidify the organic a water-miscible acid, preferably acetic or formic acid, and a higher amine such as octadecylamine is used as an emulsifier, whereupon the resulting spherical hydrogel is isolated, preferably by suction or centrifugation. For many purposes, the hydrogel thus prepared is partially cured in a further process by heating above 100 ° C in a neutral organic solvent, preferably amyl acetate or dibutyl sebacate, thereby partially distilling water from the hydrogel. In addition, the product of the first and second process steps is purified by known methods, for example by rinsing with aqueous solutions of hydrogen chloride or sodium phosphate, water, acetone, ethanol or other volatile solvents. Then the silica gel is boiled with water and dried at temperatures up to about 450 ° C. The procedure gives excellent results, but it is quite slo200997

200 997, in particular the need for double cleaning and the use of two different types of organic liquids, which must be separately recovered.

According to the invention, the present two-step process is carried out in a single-stage process in a uniform medium of mono-, di- or tri-alkyl-benzenes or mixtures thereof, thereby substantially simplifying and cheaper. No earlier purification of silica gel between the two process steps, as well as the use of a second organic liquid and its recovery, is eliminated. In addition, considerable time savings are achieved. The preparation of the spherical silica gel particles and the polymerization itself is the same as above.

Accordingly, the present invention provides a process for preparing spherical silica particles of controlled size and controlled pore size by polymerizing a suspension of free liquid silicic acid obtained by acidifying alkali metal silicate solutions with a water-miscible organic acid such as acetic or formic acid in an organic solvent using a higher aliphatic amine such as of an emulsifier followed by heat curing with partial unacceptable removal of water, characterized in that the silicic acid suspension is polymerized in mono-, di- or trialkylbenzenes or mixtures thereof at temperatures above their freezing point and in the same environment without separating and purifying the silica gel by heating by distilling off the water as an azeotropic mixture, followed by isolation and conventional purification.

Examples of suitable suspending media are toluene, xylenes, trimethylbenzenes, ethylbenzene, diethylbenzenes, isopropylbenzene, n-propylbenzene, butylbenzenes or amylbenzenes. All these aromatic hydrocarbons have a boiling point above 100 ° C, and their azeotropic mixtures with water have a binder temperature reasonably lower.

Example 1

100 ml water glass was mixed with 300 ml water. The mixture was poured into 40 mL of glacial acetic acid. 1.3 g of octadecylamine was dissolved in a 400 ml xylene in a 1 liter round glass flask and silic acid was poured into the solution with stirring (stirrer speed 700 rpm). The mixture was heated at 80 ° C for 30 minutes. The stirrer was replaced with a condenser and the temperature was raised. The water-xylene azeotrope distilled at a temperature of 92 ° C. During the distillation, 750 ml of xylene was gradually added to the flask. A total of 900 ml of xylene and 350 ml of water were distilled off.

After cooling, the remaining xylene was removed from the silica gel, the silica gel was suspended in 300 ml of acetone, and after 60 minutes the suspension was aspirated on a vacuum aspirator. The gel was suspended in dilute HCl (20: 1 water - 36% HCl) and heated to boiling for two hours. After isolation by suction and washing with acetone, it was suspended in water and heated to boiling for 1 hour. Suction, washing with acetone and boiling in water were repeated three times. The gel was then dried for 12 hours at room temperature, 1 hour in an oven at 120 ° C and annealed in an oven at 450 ° C for 24 hours. The product was spherical silica particles (5 [mu] m to 40 [mu] m) with a specific surface area of 542 m < ² > / g.

200 997

Example 2

300 ml of water glass (density 36-38 Be) was diluted with 900 ml of distilled water. A 3 L reactor equipped with a stirrer was charged with 1200 mL of toluene in which 3.5 g of octadecylamine was dissolved. The diluted water glass was added to 120 mL of glacial acetic acid with stirring. The silicic acid solution thus prepared was poured into the toluene reactor under stirring (1000 rpm). The reactor was heated to 75 ° C for 30 minutes.

A distillation head was then placed on the reactor and the temperature was further increased with stirring (100 rpm). The toluene-water azeotrope distilled from the reaction mixture (boiling point 85 ° C). A total of 930 ml of water were distilled off. Toluene was added to the reactor during distillation. Distillation was complete when pure toluene began to distill. The dried gel was isolated by aspiration and purified by a conventional procedure (washing with acetone, HCl, distilled water) and dried at 120 ° C. After drying, it was heated in an oven at 450 ° C for 24 hours. The final product was spherical silica particles of 2 to 20 Pa in size with a specific surface area of 960 m / g.

SUBJECT OF THE INVENTION

Claims (1)

SUBJECT OF THE INVENTION Process for preparing spherical silica particles of controlled size and controlled pore size by polymerizing a slurry of free liquid silicic acid obtained by acidifying alkali metal silicate solutions with a water-miscible organic acid such as acetic or formic acid in an organic solvent using a higher aliphatic amine emulsifier followed by curing by heat with partial or total removal of water, characterized in that the silicic acid suspension is polymerized in mono-, di- or trialkylbenzenes or mixtures thereof at temperatures above their freezing point and in the same environment without separation and purification of silica gel by hardening by distillation water in the form of an azeotropic mixture, followed by isolation and usual purification.