Study On Supported Ruthenium Catalysts For The Catalytic Oxidation Of VOCs

Nowadays, air pollution is one of the most prominent environmental problems in China, and VOCs (volatile organic compounds) are important components of atmospheric pollutants. Catalytic oxidation process can completely decomposing VOCs into CO2, H2O and other small molecular substances, which makes it become an significant approach for the control of VOCs emission. However, the catalytic systems utilized at present usually show poor activities and tend to occur deactivation permanently, when the exhaust gas contains a considerable amount of chlorinated VOCs (Cl-VOCs). Therefore, developing a catalyst system that effectively applied for the catalytic oxidation of Cl-VOCs is an important research direction.In this thesis, ruthenium was used as active component, and the catalytic properties of supported ruthenium catalysts for the catalytic oxidation of benzene, chlorobenzene and trichloroethylene were studied. The active structures of ruthenium during its interaction with the different reactants were disclosed, and the stabilities of these structures were investigated. Furthermore, in consideration of polychlorinated benzenes were generated during the catalytic oxidation of chlorobenzene over the ruthenium catalysts, the catalytic processes of a variety of chlorobenzene species over V2O5/P25-TiO2 catalysts were investigated in depth, and through comparing the results of these catalytic systems, the formation mechanism of polychlorinated benzenes during the catalytic oxidation of chlorobenzene was proposed.Main results are as follows:1) The active species and the mechanism of interaction between the reactant and the active sites were studied for the ruthenium catalysts under the condition of benzene oxidation, the causes of size effect of RuO2 particles were investigated, and the cause of inert RuO2 and its influence on catalyst activity were analyzed;2) Through the study on the ruthenium catalysts for the catalytic oxidation of chlorobenzene, it was found that the catalytic activity of RuOxCly structure could maintain stable during the catalytic oxidation of chlorobenzene and trichloroethylene in the presence of additional H2O, thus blocking the path of inert RuO2 formation, and the activities of ruthenium catalysts for the catalytic oxidation of chlorobenzene and trichloroethylene were much higher than that of former reported systems;3) The thermal stabilities of RuO2 over different supports were compared, it was suggested that the Ru/rutile-TiO2 structure showed the best performance, which made P25-TiO2 and rutile-TiO2 more suitable as supports for RuO2 in the catalytic oxidation of VOCs;4) No polychlorinated benzenes was found during the catalytic oxidation of all studied chlorobenzene species over the V2O5/P25-TiO2 catalysts, it was attributed that the surface phenolate species formed throuh the reaction between the reactants and the V=O structure of VOx species could not desorb form the catalyst surface.