高温气溶胶反应器中制备纳米TiO_2颗粒的形态和结构

Morphology and Structure of Nanosized TiO 2 Particles Synthesized in High Temperature Aerosol Reactor

在高温管式气溶胶反应器中，利用ＴｉＣｌ４气相氧化制备纳米ＴｉＯ２颗粒，研究了ＴｉＯ２颗粒的形态和结构特征。实验结果表明氧气预热温度升高，ＴｉＯ２粒子粒径减小、分布变窄；反应气氛中加入ＡｌＣｌ３后ＴｉＯ２粒子变得圆整，ＴｉＯ２粒径随ＡｌＣｌ３用量增加而减小，粒子中金红石含量随ＡｌＣｌ３用量增加而增大；反应温度升高时ＴｉＯ２粒子粒度增大，但金红石含量在反应温度为１２００°Ｃ时出现最大值。控制反应温度为１１００°Ｃ、进料中ＡｌＣｌ３与ＴｉＣｌ４摩尔比为０．２５、停留时间１．７ｓ时，得到纯相金红石型纳米ＴｉＯ２粒子，平均粒径２９．０ｎｍ、比表面积２３．４ｍ２／ｇ。

Nanosized titania particles were synthesized by the gas phase oxidation of titanium tetrachloride in a high temperature tubular aerosol flow reactor which consisted of three zones: a preheating zone for oxygen and vaporized titanium tetrachloride, a reaction zone, and a cooling zone for particles. The morphology and structure of titania particles were studied. As the preheating temperature of oxygen increased, average particle size of titania became smaller and size distribution more uniform. The addition of AlCl 3 can altered the particle morphology from polyhedral to spherical, enhance the rutile weight fraction, and reduce the particle size. The effect of aluminum on the phase transformation was explained by the formation of excess oxygen vacancies as Al 2O 3 and TiO 2 form a substitutional solid solution. The effect of reaction temperature on the characteristics of nanasized titania particles was also investigated. The results showed that the maximum rutile weight fraction was attained at 1 200°C and the particle size increase with increasing temperature. Pure rutile of titania particles was formed at T =1 100°C, FR =0.25 and τ =1.7s. The average grain size of the particles was 29.0nm, and the BET specific surface area was 23.4m 2/g.