Multipollutant removal of Hg0/SO2/NO from simulated coal-combustion flue gases using metal oxide/mesoporous SiO2 composites

Abstract

This study investigated the multipollutant control effectiveness for Hg0/SO2/NO using V, Mn, and Cu oxides/mesoporous SiO2 particulate composites. The presence of metal oxides decreased the specific surface area and pore volume and altered the surface morphology and sizes of the raw SiO2 particles. V4+/V5+, Mn4+, and Cu+/Cu2+ were the major valence states in the VOx, MnOx, and CuOx/SiO2 composites, respectively. Amorphous and highly dispersed metal oxides presenting in the SiO2 composites was confirmed by the X-ray diffraction characteristic peaks. Multipollutant control of Hg0 and NO using the metal oxide/SiO2 composites was achieved at both 150 and 350°C under the simulated coal-combustion flue gas condition. CuOx/SiO2 with >40% Hg0 removal at 350°C further implies that strong chemical bonds could form between Hg species and the surface groups of CuOx/SiO2. The metal oxide/SiO2 composites had up to 62% NO removal enhancement with injection of NH3 at 350°C, indicating the effectiveness of catalytic reduction of NO. The CuOx/SiO2 composite showed the greatest Hg0 and NO removal performance, which may stem from the presence of active CuOx in high content and its large surface area and mesoporosity.