Studies On Photocatalytic Activity Of Nano-TiO₂ Prepared By Adsorption Phase Reactor Technology

Nanometer technology develop in rapid speed, then provided good opportunity for the technical application of the nanometer photocatalysis, so the photocatalysis technique becomes the hostpot in science research nowadays. At present, nanometer TiO₂ photocatalyst with large specific sueface atea, high surface energy and many activity sites is studied mostly and has wide application in enviroment protection, energy materials and chemical industry and so on, because its catalytic activity and selectivity are higher than tradional catalyst greatly. But the catalytic activity of nanometer TiO₂ is easy to decline even lost by reason of its aggregation effect. Therefore, the research of TiO₂ with high photoactivity is the key for its industrialization.In this dissertation, photocatalytic property of TiO_/SiO₂ nanocomposite materials synthesized by new method-adsorption phase reaction technique was studied. TiO₂ with small grain size is dispersed on the suefaceof SiO₂.First, crystal struction,characteristic and application of nano-TiO₂ were reviewed.The author introduced maily advantages and disadvantages of the preparation methods of nanocomposite materials, research status of adsorption phase reaction technique, photoatalytic mechanics of TiO₂ and various photocatalytic factors. Photocatalytic reaction dynamics of gas-solid were also generalized.Nano-TiO₂/SiO₂ was characterized by means of TEM, EDAX, XRD and BET. The factors affecting photocatalytic activity were discussed in process of the degradation of gaseous toluene, which was agreement with first-order dynamics equation. The intermediate products were detected and infered by Fourier-trasform infrared spectroscopy (FT-IR)and gas chromatography-mass (GC-MS)on-line. The activity of catalysts with conditions of preparation and heat treatment is compared using first-order reaction rate constants and the influencing factors were analysed. The activity of self-synthesis was compared with traditional impregnation method and P25 commodity. The results showed:(1) Catalytic activity was affected by preparation temperature least; the photocatalytic activity improved with increasing the amount of water and tetrabutyl titanate.Tha rate of degradation was linear with Ti content and the amount of tetrabutyl titanate.(2) Calcined temperature and time could improve crystallnity and acceleratedphotocatalytic degradation. When Calcined temperature reached 900℃, the photocatalytic activity declined because the grain size became large and specific surface area declined. But the TiO₂ still keep anatase without crystal transformation.(3) The observed rate constants of TiO₂/SiO₂ prepared by adsorption phase reaction technique was half past one than impregnation method preparation and the photocatalytic activity is higher than P25, because the grain size was major facror influnced photocatalytic activity.