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Silicon for the Chemical and Solar Industry XIII
Kristiansand, Norway, June 13 – 16, 2016
Pyrogenic Silica - A High-Tech Material from Products of
Silicon Processing
Torsten Gottschalk-Gaudig
1)
and Erwin-Peter Mayer
1)
1) Wacker Chemie AG, Burghausen, Germany
Abstract
Side products of the silicon processing during chlorosilane and methyl chlorosilane
production can be used for pyrogenic silica production. Pyrogenic silica is a
nanostructured particulate material with aggregate sizes in the range of ca. 100 – 250
nm. The material reveals unique structural properties due to the fractal character of the
aggregates. The publication describes the production process and elucidates the
influence of the process and specific process conditions on the morphology of
pyrogenic silica. Selected physico-chemical characteristics of pyrogenic silica are
discussed and the interplay between pyrogenic silica morphology and its main industrial
applications is demonstrated.
Introduction
Pyrogenic silica is a typical example for synthetic amorphous silica (SAS). Other
examples for this class of materials are precipitated silica and silica gels. The latter are
produced in a so called wet process by controlled precipitation of silica, whereas
pyrogenic silica is obtained in a gas-borne high temperature hydrolysis/oxidation of
chlorosilanes..
Pyrogenic silica is characterized by large specific surface area of ca. 50 – 400 m
2
/g
and a highly structured aggregated morphology. Typical industrial applications of
pyrogenic silica like active fillers for plastics and elastomers, rheology control additive,
and thermal insulation are making use of these characteristics.
Production Process
Raw materials for production of pyrogenic silica are chlorosilanes obtained in the
production of photovoltaic or semiconductor silicon and methyl chlorosilanes from
Müller-Rochow process.
In case of chlorosilanes, tetrachlorosilane, SiCl
4
, is mainly used for pyrogenic silica
production [1]. However, also other chlorosilanes such as trichlorosilane, HSiCl
3
or
dichlorosilane. H
2
SiCl
2
, can be used. The use of chlorosilanes in the production of value
added pyrogenic silica is an attractive alternative to silane conversion, which is very
demanding in terms of energy.
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