Optimal Conditions for Preparing Ultra-Fine CeO_2 Powders in A Submerged Circulative Impinging Stream Reactor

摘要

Cerium carbonate powders were produced in a submerged circulation impinging stream reactor (SCISR) from Ce(NO_3)_3 • 6H_2O. NH_4HCO_3 was used as a precipitant in the reaction. Cerium carbonate powders were roasted to produce ultra-fine cerium dioxide (CeO_2) powders. The optimal conditions of such production process were obtained by orthogonal and one-factor experiments. The results showed that ultra-fine and narrowly distributed cerium carbonate powders were produced under the optimal flowing conditions. The concentrations of Ce(NO_3)_3 and NH_4HCO_3 solutions were 025 and 0.3 mol • L~(-1), respectively. The concentration of PEG4000 added in these two solutions was 4 g • L~(-1). The stirring ratio, reaction temperature, feeding time, solution pH, reaction time and digestion time were 900 r • min~(-1), 80℃, 20 min, 5 ～ 6, 5 min and 1 h, respectively. The final product, CeO_2 powders, was obtained by roasting the produced cerium carbonate in air for 3 h at 500℃. The finally produced CeO_2 powders were torispherical particles with a narrow size distribution of 0.8 ～ 2.5 μm. The crystal structure of CeO_2 powders belonged to cubic crystal system and its space point group was O_H~5-F_(M3M). Under optimal conditions, powders produced by SCISR were finer and more narrowly distributed than that by Stirred Tank Reactor (STR).