Patent ID: 6217840
Filing Date: 2001-04-17
Classification: C01B,C01C,C01D,C01F,C03C,C04B,C22B,Y02P,Y02W

Abstract:
A method of producing fumed silica and a fluorine-containing product from a source of silica and a solid fluoride-containing material selected from the group consisting of sodium aluminum tetrafluoride, cryolite, aluminum fluosilicate, ammonium bifluoride, sodium aluminum silicofluoride, and sodium fluosilicate, the method comprising the steps of:(a) digesting said silica and said solid fluoride-containing material selected from the group consisting of sodium aluminum tetrafluoride, cryolite, aluminum flurosilicate, ammonium bifluoride, sodium aluminum silicofluoride, and sodium fluosilicate in a sulfuric acid digester to produce a gas component comprised of silicon tetrafluoride, hydrogen fluoride and water vapor;(b) removing said first gas component from said digester;(c) heating said gas component recovered from said digester in the presence of an oxygen source to a temperature sufficiently high to convert said silicon tetrafluoride to fumed silica in the presence of said hydrogen fluoride; and(d) separating said filmed silica from said hydrogen fluoride.