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US 5,266,289 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 a high-purity silica which comprises:
- I) reacting a crude silica with ammonium fluoride or a mixture of ammonium fluoride and acid ammonium fluoride in an aqueous medium to produce ammonium silicofluoride;
- II) separating said ammonium silicofluoride from an unreacted silica and impurities by means of a solid/liquid separation;
- and
- III) reacting said separated ammonium silicofluoride in said aqueous medium with ammonium to produce a silica having an Al.sub.2 O.sub.3 content of <0.01 wt. %.
1 more element
Dependencies are inferred from the claim text.