Integrated removal of NO and mercury from coal combustion flue gas using manganese oxides supported on TiO2

A catalyst composed of manganese oxides supported on titania (MnOx/TiO2) synthesized by a sol-gel method was selected to remove nitric oxide and mercury jointly at a relatively low temperature in simulated flue gas from coal-fired power plants. The physico-chemical characteristics of catalysts were investigated by X-ray fluorescence (XRF), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analyses, etc. The effects of Mn loading, reaction temperature and individual flue gas components on denitration and Hg-0 removal were examined. The results indicated that the optimal Mn/Ti molar ratio was 0.8 and the best working temperature was 240 degrees C for NO conversion. O-2 and a proper ratio of [NH3]/[NO] are essential for the denitration reaction. Both NO conversion and Hg-0 removal efficiency could reach more than 80% when NO and Hg-0 were removed simultaneously using Mn0.8Ti at 240 degrees C. Hg-0 removal efficiency slightly declined as the Mn content increased in the catalysts. The reaction temperature had no significant effect on Hg-0 removal efficiency. O-2 and HCl had a promotional effect on Hg-0 removal. SO2 and NH3 were observed to weaken Hg-0 removal because of competitive adsorption. NO first facilitated Hg-0 removal and then had an inhibiting effect as NO concentration increased without O-2, and it exhibited weak inhibition of Hg-0 removal efficiency in the presence of O-2. The oxidation of Hg-0 on MnOx/ TiO2 follows the Mars-Maessen and Langmuir-Hinshelwood mechanisms. (C) 2016 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B. V.