微波辐射对TiO_2制备及其光催化氧化乙醛性能的影响

Effect of Microwave Field on Preparation of TiO_2 and Photocatalytic Oxidation of Acetaldehyde

采用微波辐射与常规加热法由TiO2溶胶制备出TiO2催化剂,采用高频低功率微波-光催化装置考察了微波对两种催化剂上CH3CHO光催化氧化转化率和产物分布的影响。结果表明,微波干燥制备的TiO2晶体比普通加热制备的TiO2晶体对乙醛有更高的光催化活性和更强的氧化能力,且它们对乙醛光催化氧化的途径不同,前者的初始中间体为甲醛和甲酸,后者的初始中间体却为乙酸。还发现,微波辐射对两种样品上乙醛的光催化转化率有不同的影响,对微波辐射法所制样品的影响比对常规加热法所制样品的影响显著。微波辐射通过场效应可加速光催化初始中间体的转化,但它不改变光催化反应的途径,反应途径取决于光催化剂的特性。

TiO2 catalysts were prepared from a TiO2 sol by microwave heating and conventional heating, respectively. A microwave-light reactor equipped with a high frequency microwave source and UV light source was used to investigate the effect of microwave on the photocatalytic degradation and product distribution of acetaldehyde over both samples obtained above. The results showed that the sample prepared by the microwave heating presented higher photocatalytic activity and stronger oxidative ability to acetaldehyde than that obtained by conventional heating. There were different oxidative pathways on the two catalysts: the initially reactive intermediates were formaldehyde and formic acid on the sample by microwave heating, and acetic acid on the sample by conventional heating. It was also found that microwave had different effect on the photocatalytic conversion of acetaldehyde for two samples. The effect was more remarkable for the sample prepared by the microwave heating than that prepared by the conventional heating. Enhanced photocatalytic capacity of TiO2 by microwave mainly was from a field effect, which can accelerate a transform of the initial intermediates but does not change the photocatalytic pathway (the pathway depends on the properties of catalyst).