高温气相法可控制备纳米TiO2

通过火焰反应器结构设计，实现TiCl4高温气相氧化过程可控制备纳米TiO2粒子，新型火焰设计保证了TiCl4低温进入高温反应区，预热过程隔离保护喷嘴，避免了结疤堵塞;通过实验条件控制颗粒平均粒径和粒径分布，较低的TiCl4气相浓度、较高的载气流速有利于小粒径TiO2颗粒的生成。载气流速增加，中心TiCl4火焰形态由层流向湍流发展，焰长缩短，颗粒平均粒径减小。CH4燃气流量增加，高温反应区扩大，颗粒停留时间增加，颗粒尺寸增大。二次氧气的补充，提高了氧气与TiCl4的预混，有效地减小了产品TiO2颗粒的粒径。获得的TiO2产品平均粒径在20～80 nm之间。

Controlled synthesis of nano-sized TiO2 powders using high-temperature vapor phase process

Controlled synthesis of nano-sized titania (TiO2) powder was performed by an improved design of a flame reactor, where titanium tetrachloride (TiCl4) was oxidized in vapor phase at high temperature conditions.By isolating the methane (CH4) flames from the injection of TiCl4, the formation of TiO2 occurred at a certain distance from the TiCl4 inlet, which accordingly avoided the scaling phenomenon often encountered in such processes.The particle diameter and its distribution could be effectively influenced by the operating conditions.The results showed that a lower precursor concentration and a higher carrier-gas flow rate benefited the production of smaller particles of TiO2.The increase of the carrier-gas flow rate resulted in the transition from laminar flow to turbulent flow and the decrease of flame length,and consequently the formation of smalle particles.With increasing flow rate of CH4, the flame, i.e., the reaction zone, enlarged, causing larger particle size owing to the longer time for the formed TiO2 to stay in the flame.While, extra oxygen supply around the center nozzle of TiCl4 could effectively reduce the particle size of TiO2, which may be attributed to the better initial mixing of TiCl4 and oxygen.The nano-sized TiO2 particles ranging from 20 nm to 80 nm on average were obtained in most of the experiments.