Role of NO in Hg0 oxidation over a commercial selective catalytic reduction catalyst V2O5-WO3/TiO2

Experiments were conducted in a fixed-bed reactor that contained a commercial catalyst, V2O5-WO3/TiO2, to investigate mercury oxidation in the presence of NO and O-2. Mercury oxidation was improved by NO, and the efficiency was increased by simultaneously adding NO and O-2. With NO and O-2 pretreatment at 350 degrees C, the catalyst exhibited higher catalytic activity for Hg-0 oxidation, whereas NO pretreatment did not exert a noticeable effect. Decreasing the reaction temperature boosted the performance of the catalyst treated with NO and O-2. Although NO promoted Hg-0 oxidation at the very beginning, excessive NO counteracted this effect. The results show that NO plays different roles in Hg-0 oxidation; NO in the gaseous phase may directly react with the adsorbed Hg-0, but excessive NO hinders Hg-0 adsorption. The adsorbed NO was converted into active nitrogen species (e. g., NO2) with oxygen, which facilitated the adsorption and oxidation of Hg-0. Hg-0 was oxidized by NO mainly by the Eley-Rideal mechanism. The Hg-0 temperature-programmed desorption experiment showed that weakly adsorbed mercury species were converted to strongly bound ones in the presence of NO and O-2. (C) 2015 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.