Catalytic Conversion of Polychlorinated Aromatic Compounds Including Dioxins on Vanadium-based Catalysts

摘要

The interest in environmental pollutants, especially combustion flue gases, such as dioxin and polychlorinated benzene, is ever increasing. To prevent the emission of dioxins, most combustion systems are equipped with flue gas clean-up systems. In municipal waste incinerators, the efficient control of dioxin is affected using the de-NOx SCR process. In this work, the catalytic conversion of chlorinated benzenes as a dioxin surrogate compound was performed to investigate the catalytic conversion efficiency of a V_2O_5/TiO_2 catalyst because chlorinated benzenes, especially 1,2-dichlorobenzene (1,2-DCB), has been widely used as one of surrogate compounds of dioxin to find the noble methods to control dioxin. However, the relationship between the catalytic activity of dioxin and dioxin surrogate compounds for bench-scale experiments has not been understood quite well. We used a vanadium based catalyst (V_2O_5/TiO_2) to compare catalytic activity of chlorinated benzenes and dibenzo-p-dioxins with low-chlorine content using a lab-scale experimental apparatus. We investigated the catalytic conversions of low chlorinated dioxins, (2-monochloro dibenzo-p-dioxin (2-MCDD), 2,3-dichlorodibenzo-p-dioxin (2,3-DCDD)) which have appropriate vapor pressure values and polychlorinated benzenes (1,2-DCB, 1,2,3,4-tetrachlorobenzene (1,2,3,4-TeCB), penta-chlorobenzene (PeCB), hexa-chlorobenzene (HCB)) using a V_2O_5/TiO_2 catalyst to understand quantitative relationship between dioxin and benzene with the chlorination level. The was following order of catalytic decomposition of chlorinated aromatic compounds has been obtained: 1,2-DCB > 1,2,3,4-TeCB > 2-MCDD > PeCB > 2,3-DCDD > HCB. It seems more reasonable that PeCB or HCB should be used as the dioxin surrogate compound rather than 1,2-DCB.