Vanadium Oxides (V2Ox) Catalysts for Dry-Type and Simultaneous Removal of Sulfur Oxides and Nitrogen Oxides with Ammonia at Low Temperature

In order to develop highly functional catalysts for a dry-type, simultaneous removal of sulfur oxides (SOx) and nitrogen oxides (NOx) the catalytic activities of V2Ox/TiO2, V2Ox/TiO2/AC(activated carbon) and V2Ox/AC (4<x<5) were studied using a fixed bed flow reactor. In this process SO2 is catalytically oxidized to SO3 and then fixed on the catalyst as ammonium sulfates by reactions with H2O and NH3; NOx are reduced to N2 with NH3 over the same catalyst at low temperature (ca. 130 °C). The sulfates deposited on the catalyst must be periodically removed for regeneration in order to realize repeated use of the catalyst. V2Ox/TiO2 was found to be a suitable catalyst for the simultaneous removal and to have an acceptable tolerance for reiterative regeneration. Also, water washing of the used catalyst after a NH3 pretreatment was found to be preferable for regeneration. The sulfates deposited on the catalyst could be recovered as (NH4)2SO4 by this type regeneration. The deposited sulfates were amorphous and could be regarded as being a mixture of NH4HSO4 and (NH4)2SO4. These sulfates reacted with NOx to produce N2.