Wenbo Jia,Yueyuan Wang,Shaohua Ling,Liren He,Binghe Chen,Songtao Liu,Chuanmin Chen,Yue Cao
Fast selective catalytic reduction (SCR) atmosphere can significantly improve the NOx removal activity of VWTi catalysts, while the catalytic performance and reaction pathway of Hg0 oxidation in a fast SCR atmosphere are still unclear. In this paper, the catalytic activity of simultaneous NOx removal and Hg0 oxidation over VWTi catalysts in a simulated fast SCR atmosphere was investigated for the first time. The results showed that VWTi catalysts possessed a wide NOx removal active temperature window and a high Hg0 oxidation activity in a fast SCR atmosphere. The X-ray photoelectron spectroscopy (XPS) and Hg temperature-programmed desorption (Hg-TPD) methods were used to investigate the Hg0 oxidation process over VWTi catalysts in a fast SCR atmosphere. Combined with the homogeneous Hg0 oxidation experiment results, two domination reaction routes of Hg0 oxidation over VWTi catalysts in a fast SCR atmosphere were proposed. One was that the adsorbed Hg0 could react with the surface active species to form HgO. The other reaction route was a gaseous homogeneous route that the gaseous Hg0 could be oxidized directly to Hg(NO3)2 by gaseous NO2. Particularly, the gaseous homogeneous Hg0 oxidation process could notably weaken the inhibition effect of NH3 on Hg0 oxidation, thus improving the Hg0 oxidation activity of VWTi catalysts in a fast SCR atmosphere.
Mercury has a significant impact on environment and is mainly derived from coal-fired power plant. Herein, we report a potential route for efficient removal of Hg 0 via oxidation reactions using Ce-doped LaCoO 3 supported on CeO 2 catalyst. Catalyst characterization results proved that Ce can successfully substitute a desired part of Co into the LaCoO 3 crystal lattice via a sol–gel method. The Hg 0 removal experiments suggest that Hg 0 removal efficiency decreased in the order of La 0.875 Ce 0.125 CoO 3 /CeO 2 > La 0.875 Ce 0.125 CoO 3 > LaCoO 3 . The presence of O 2 provided more active oxygen and resulted in approaching 100% Hg 0 removal efficiency. Introducing H 2 O and sole SO 2 would significantly reduce the Hg 0 removal efficiency as a result of competitive adsorption on the actives sites of the catalyst. On the other hand, SO 2 could reacted with Hg 0 in the presence of O 2 and thereby recover the high Hg 0 removal efficiency and the La 0.875 Ce 0.125 CoO 3 /CeO 2 catalyst presented a good performance towards sulfur resistance. Furthermore, the catalyst still exhibited a high Hg 0 removal efficiency performance after five times consecutive recycles.
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