Process for purifying tantalum oxide and other metal oxides

Abstract

There is disclosed a process for producing premium grades of metal oxide comprising (1) providing wet or dried hydrous metal oxide containing high levels (e.g., 2%-10% chloride) of halogen contamination, (2) treating the contaminated metal oxide with a base in gas phase, which base is volatile at .ltoreq.900.degree. C., at a final temperature of between 750.degree. C. to no greater than 900.degree. C. wherein the temperature is brought to the final temperature in increments of about 25.degree. C., until gas exiting shows no additional evolution of a halogen conjugated acid, and (3) exposing the treated metal oxide to air or oxygen at a temperature of 500.degree. to 600.degree. C. to convert any metal nitrides or oxynitrides present to metal oxide, wherein the metal oxide is selected from the group consisting of Ta.sub.2 O.sub.5, niobium oxide, hafnium oxide, zirconium oxide and titanium oxide. The inventive process yields a premium grade, high active surface area .beta.-Ta.sub.2 O.sub.5 product with a chloride content that is below detection limits (e.g., .ltoreq.1 ppm-0.2 ppm) and in which the contaminant metals levels are unchanged or diminished from the levels of the hydrous oxide starting material.

Dependencies are inferred from the claim text.