In Situ FTIR Study On Photo-catalytic Degradation Of Gaseous Trichloroethylene

The chemical behavior and degradation mechanism of the volatile organic compounds on the catalyst interface is a hot subject in the chemical field of contamination control. The infrared spectroscopy is one of the most effective means in the research on the environment catalysis reaction and mechanism. It has an obvious advantage in the research on the reaction system and the surface active groups of catalyst, especially under the in-situ condition. This paper uses the in-situ infrared spectra technology as the main approach to study the photocatalytic reaction of trichloroethylene, the typical volatile organic compounds, at the surface of P25 TiO₂ and inclusion structure materials, ZnS:Mn/β-CD to establish a scheme of the application of the in-situ infrared spectra technology in the environment catalysis.In this paper, the in-situ infrared spectra technology is used to investigate the photocatalystic reaction of gas-phase trichloroethylene over P25 TiO₂ and inclusion structure materials, ZnS:Mn/β-CD. The result shows:(1) Light intensity is a factor to affect the photocatalysis mechanism. Under special light intensity, the photocatalysis of trichloroethylene on the TiO₂ surface exists in the following degradation pathways: under the effect of hydroxy radicals and other radicals components, trichloroethylene generates the intermediate product, dichloroacetylchloride, which was converted into CO₂, CO, H₂O, HCl and phosgene etc. eventually by further degradation.(2) The inclusion structure materials ZnS/β-CD can be prepared by co-deposition method. The inclusion effect ofβ-cyclodextrin on ZnS can effectively help ZnS improve its photocatalytic degradation efficiency of trichloroethylene. And Mn ionic doped into the ZnS/Mn can also affect the photocatalytic degradation efficiency of trichloroethylene.(3) The way that ZnS:Mn/β-CD degrades trichloroethylene through photocatalysis differs from the way P25 TiO₂ does on trichloroethylene. In reaction and product transformation of such intermediate products, dichloroacetylchloride can not be observed as occurs during the process when P25 TiIO₂ degrades trichloroethylene through photocatalysis.The in-situ infrared spectra technology established in this research is an effective approach to find out the process of the multi-phase catalytic primitive process and the kinetics mechanism of the surface reaction, which will surely become an important method in the research and development of environmentally friendly catalyst.