PREPARATION OF HIGHLY ACIDIC HYDRATED NIOBIUM OXIDE

In order to obtain a highly acidic hydrated niobium oxide, the prepara tion methods and conditions such as niobium precursors, precipitating reagents, treatment of precipitates, washing of precipitates, final pH in precipitation, and calcination temperature were systematically exa mined. Strong acidic sites of H-0 less-than-or-equal-to -8.2 were foun d to appear on hydrated niobium oxide when the oxide was prepared by b oiling the precipitates, which were obtained by hydrolysis of niobium oxalate with KOH, in a diluted mild acid solution(preferably 0.1N HNO3 ) followed by washing with hot water several times and heating in air at 300-degrees-C. Final pH in the precipitation must be below 11.