DE3937394A1 - Pptd. silica prodn. by hydrolysis of silicon tetra:chloride - by dropwise addn. of water or silicon tetra:chloride to other reactant which is mixed or dissolved in organic solvent - Google Patents

Abstract

Silicic acids (I) are produced by hydrolysis of SiCl4 (II) with water in the presence of an organic solvent system (III), the novelty is that either (II) or the water is added dropwise, in pure form, to the other reactant (water or (II)) which is in the form of a mixt. or in soln. with (III). (III) is e.g. hydrocarbon, ether (e.g. THF), EtOAc, CHCl3, acetone, silicone oil, AcOH etc. or a mixt. thereof, pref. (II) is added to the aq. phase (esp. at 0-10 deg.C for prodn. of spherical (I)). USE/ADVANTAGE - The process enables the prodn. of hydrophobic pptd. silica in one step (if the solvent contains a siloxane or a silicone oil), with BET surface and particle size distribution tailored to requirements (by adjusting the process conditions), the prod. is pref. obtd. as compact 20-100 micron spheres, useful e.g. as a catalyst support, foam suppressant, matting agent, silicone rubber filler, etc.

Description

The invention relates to a process for the preparation of silicic acids by hydrolysis of Silicon tetrachloride by means of water in the presence of a organic solvent system.

It is known to produce precipitated silicas, by adding liquid silicon tetrachloride in a stirred aqueous Flußsäurelösung (DE-A 35 43 172).

Furthermore, it is known that precipitated silicas are higher To produce purity by using silicon tetrachloride and an equivalent amount of water in one brings organic solvent to the reaction. there will always be the phase containing the silicon tetrachloride contains, submitted and the hydrous phase added. As organic solvents are benzene, Glacial acetic acid, acetone used (US-PS 22 69 059).

The invention relates to a method for Production of silicic acids for the production of Silicic acids by hydrolysis of silicon tetrachloride by means of water in the presence of an organic Solvent system, which is characterized is that you either the silicon tetrachloride or presenting the water and the other one Reactants are added dropwise, either the  Silicon tetrachloride or the water in pure form dropped while the other reactant in the mixture or in solution with the organic Solvent system is presented.

In a preferred form of the invention, the submitted aqueous phase and the silicon tetrachloride added.

The reaction temperature can be between 0 and 50 ° C, preferably maintained between 10 and 30 ° C.

Of particular interest may be the reaction temperature from 0 to 10 ° C, because here preferably spherical Products are created.

As organic solvents it is possible to use individually or in a mixture of at least two compounds:
Hydrocarbons, such as. As petroleum ether, gasoline, paraffins or octane.
Ether, such as. As tetrahydrofuran, diethyl ether or di-n-butyl ether.
Esters, such as. As ethyl acetate or waxes.
Chlorinated hydrocarbons, such as. As methylene chloride, trichloroethane.
Nitrated hydrocarbons, such as. B. nitromethane.
Ketones, such as Acetone.
Siloxanes, such as. For example, silicone oil.
Quaternary ammonium compounds, such as. For example, octadecyldimethylbenzylammonium chloride.
Carboxylic acid such as. As acetic acid, propionic acid.

The inventive method has the following Advantages on:

It can be defined hydrophobic silicas in one Step produced when the organic Solvent contains a siloxane or a silicone oil.

By adjusting the process conditions is the tailoring of BET surfaces and the Particle distribution possible.

It can be 20 to 100 μ large preferably producing compact spheres of silicon dioxide.

These spheres can advantageously be used as catalyst supports. The hydrophilic silicas can be used after calcination as a quartz substitute. The hydrophobic silicas can be used as defoamer silicas, matting agents or as fillers in silicone rubber.

Examples

In the following experiments will be a three-necked flask used. It is cooled with water. The Reaction mixture is by means of a KPG stirrer touched. In the reaction is usually a Temperature range of 10 to 30 ° C maintained.

The BET surface area of the products obtained is reduced DIN 66 131 using nitrogen gas determined.

The particle size distribution is calculated according to the CILAS method and scanning electron micrographs determined.

The reaction is usually carried out so that one submits a component and stirring the other component during a given Period dripped.  

Example 1

Template:
300 ml of silicone oil V 100 Rhone Poulenc
Rhodeosil 47 V 100
1 mol H₂O
= Emulsified for 1 h (1000 rpm)

addition: 1/2 mol of SiCl₄ Addition time: 50 min Temperature profile: 14 ± 2 ° C stirring time: 1 h (cools to -1 ° C during the stirring time) Yield: 100% Product: "Hydrophobic Silica" Surface (BET) according to DIN 66 131: 19 m² / g average particle size (cilas): 4.2 μ mean particle size (SEM): 2 μ C content: 7.9%

example 2

Template:
20 ml of silicone oil V 100 (Rhone Poulenc)
4.1 moles of ethyl acetate
1/2 mol of SiCl₄
= 600 rpm

addition: 1 mol of water Addition time: 10 min Temperature profile: 20-25 ° C stir for: 1 h = 600 rpm Product: "Hydrophobic Silica" Surface (BET): 221 m² / g average particle size (cilas): 32 μ (agglomerates) C content: 7.61%

example 3

Template:
2.05 mol of ethyl acetate
200 ml petroleum ether, boiling point 140 ° C
1 mol H₂O

addition: 0.5 mol of SiCl₄ Addition time: 60 min stirring speed: 600 rpm Temperature profile: 46-49 ° C stir for: 1 h at 45 ° C Yield: 90% Surface (BET): 47 m² / g average particle size (cilas): 13 μ

example 4

Template:
2.05 mol of ethyl acetate
200 ml petroleum ether, boiling point 140 ° C
1 mol H₂O

addition: 0.5 mol of SiCl₄ Addition time: 55 min stirring speed: 600 rpm Temperature profile: 16-24 ° C stir for: 1 h Yield: 91% Surface (BET): 110 m² / g average particle size (cilas): 13.6 μ

example 5

Template:
4.1 moles of ethyl acetate
1 mol H₂O

addition: 0.5 mol of SiCl₄ Addition time: 55 min stirring speed: 600 rpm Temperature profile: 16-20 ° C stir for: 1 h Yield: 95% Surface (BET): 780 m² / g average particle size (cilas): 30 μ

example 6

Template:
6.2 moles of acetone
400 ml of petroleum ether,
140 ° C 1 mol H₂O

addition: 0.5 mol of SiCl₄ Addition time: 55 min stirring speed: 800 rpm Temperature profile: 17-9 ° C stir for: 1 h Yield: 100% Surface (BET): 524 m² / g average particle size (cilas): 56.4 μm

example 7

Template: SiCl₄
addition:
1 mol H₂O
0.00024 mol quart. Ammonium compound (octadecyldimethylbenzylammonium chloride)
90 ml of petroleum ether, 140 ° C

Addition time: | 20 min stirring speed: 1000 rpm Temperature profile: 30-45 ° C stir for: 1 h at the same temperature Yield: 100% Surface (BET): 90 m² / g average particle size (cilas): 31 μm C content: 3.9% Cl content: 0.3%

example 8

400 ml of glacial acetic acid
200 ml of gasoline
18 ml H₂O
25 ml of silicone oil Rhodisil 47 V 10
600 rpm / 5 ° C
58 ml of SiCl₄ added dropwise in 1 h
T _Start : 7 ° C T _End : 4 ° C
1 h 15 min. stirred at 600 rpm

Surface (BET): 412 m² / g average particle size: 17 μm Methanol wettability: 57% C content: 4.8%

example 9

400 ml of glacial acetic acid
200 ml of gasoline
18 ml H₂O
10 ml of silicone oil Rhodisil 47 V 10
600 rpm / 35 ° C
58 ml of SiCl₄ added dropwise in 25 min
T _Start : 35 ° C T _End : 31 ° C
1 h 30 min stirred at 35 ° C 600 U / min.

Surface: 265 m² / g average particle size: 14 μm Methanol wettability: 61% C content: 4.4%

Claims (1)

Process for the preparation of silicic acids by hydrolysis of silicon tetrachloride by means of water in the presence of an organic solvent system, characterized in that either the silicon tetrachloride or the water is introduced and the other reactants are added dropwise, either dropwise adding the silicon tetrachloride or the water in pure form, while the other reactants in a mixture or in solution with the organic solvent system is presented.