15 - Preparation of ultrafine powders by reaction-precipitation in impinging streams III: Nano titania

Abstract

This chapter investigates the factors that affect the preparation of nano Titania. Nano Titania is prepared by TiCl4-hydrolyzation-precipitation in a submerged circulative impinging stream reactor (SCISR). The factors examined in the chapter include the concentration of TiC14 solution and pH of the reaction mixture; the impinging velocity; the reaction or mixing time and temperature; the feeding time; the feeding position; and the aging time after reaction. The experiments for the preparation of nano Titania were carried out in three stages. In the first stage the major factors affecting the size of product were examined to determine the primary optimal operation conditions. In the second stage, on the basis of the determination of the primary optimal conditions, the influences of certain factors on both the particle size and the yield of titanium were examined for further optimization of the conditions. In the third stage the experiments were carried out for mass-preparation of nano Titania with commercial TiC14 as the raw material, instead of chemical reagents, and under the conditions optimized in the last stage. The preparation experiments were also carried out with the traditional stirred tank reactor (STR) as the hydrolyzation-precipitation equipment for comparison with SCISR. The results of the comparative experiments show that, under the same operating conditions and the same specific effective power input, the product prepared with the SCISR is finer with a narrower size distribution than that prepared with the STR.