水热还原法制备超细氧化铬及粒径调控

Preparation of Ultrafine Chromia Particles by Hydrothermal Reduction and Size Control

研究了水热还原法制备超细氧化铬的工艺过程及其粒径调控.以CO2气体为酸化剂,小分子有机化合物甲醛为还原剂,通过表面活性剂处理,在水热条件下直接还原铬酸钾水溶液得到水合Cr2O3,继而800℃下煅烧得到球形Cr2O3超细粉体.考察了甲醛用量比Rm及CO2初始分压pCO2、恒温温度Tiso和恒温时间tiso对Cr(VI)还原过程的影响,确定了最佳还原工艺条件,使Cr(VI)还原转化率达到了99.9%.初次在还原体系中引入表面活性剂,具有良好的粒径和形貌调控效果,制备出了平均粒径100nm左右的球形Cr2O3.该方法工艺流程简单,成本低廉,体系成分简单,适合大规模工业生产.

Preparation of ultrafine chromia particles by hydrothermal reduction and size control was investigated. With CO2 as acidifying agent, potassium chromate was directly reduced to chromic oxide hydrate under hydrothermal conditions using formaldehyde as reducing agent. In addition some surfactants, such as TPP, PAM, PEG-600, PVP etc., were added to the system to control particle size for the first time. Then chromic oxide hydrate was converted into ultrafine spheral Cr203 particles by calcination at 800 ℃. The effects of the mole ratio of formaldehyde to chromate （Rm）, the initial partial pressure of CO2 （PCO2）, the isothermal temperature （Tiso） and time （tiso） on the conversion of Cr（Ⅵ） were also studied in detail and the optimum technological conditions were suggested. The conversion rate of Cr（Ⅵ） was 99.9% under the optimum conditions and the average particle size of spheral Cr2O3 was about 100 nm. The experimental results showed that surfactants were useful for controlling particle size and morphology. The new process showed a promising application prospect as the technique, economy and simpleness were concerned.