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US 5,458,864 AGranted
Process for producing high-purity silica by reacting crude silica with ammonium fluoride
AssigneeNissan Chemical Industries, Ltd.
InventorsMakoto Tsugeno, Kenji Tanimoto, Masao Kubo
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Abstract
A process for producing a high-purity silica, which comprises the steps of reacting a crude silica with ammonium fluoride, acid ammonium fluoride or a mixture thereof in an aqueous medium to produce ammonium silicofluoride, separating the ammonium silicofluoride from an unreacted silica and impurities by the means of a solid/liquid separation, and reacting the thus-obtained ammonium silicofluoride with ammonia in an aqueous medium. This process is a low cost process, and enables to control properties of silica.
Claims9
A process for producing high-purity silica comprising the steps of:
- i) reacting crude silica in an aqueous medium with ammonium fluoride, acid ammonium fluoride or a mixture thereof, in the presence of hydrofluoric acid or a cation exchange resin, to produce ammonium silicofluoride;
- ii) separating said ammonium silicofluoride from unreacted silica and impurities by means of a solid/liquid separation;
- and
- iii) reacting said separated ammonium silicofluoride in said aqueous medium with ammonia to produce silica having an Al.sub.2 O.sub.3 content of <0.01 wt. %.
1 more element
Dependencies are inferred from the claim text.