Synergistic Mercury Removal over the CeMnO_3 Perovskite Structure Oxide as a Selective Catalytic Reduction Catalyst from Coal Combustion Flue Gas

摘要

The LaMnO3, CeMnO3, and PrMnO3 perovskite oxides were synthesized by the sol-gel method and employed as the catalyst of selective catalytic reduction (SCR) for NO removal and synergistic mercury removal from coal combustion flue gas. The experimental results indicated that CeMnO3 exhibited the best NO and Hg-0 removal activity among the three catalysts. NO conversion over CeMnO3 could reach a maximum value of 89.2% in the atmosphere of 4% 0(2) + 400 ppm NO + 400 ppm NH3, and the optimal reaction temperature for the NO removal was 200-250 C-circle, demonstrating good low temperature catalytic activity. Hg-0 removal efficiency of CeMnO3 decreased with the rise of the reaction temperature. The individual flue gas components of O-2, HCl, NO, and CO2, had promotions on the Hg-0 removal over CeMnO3, while SO2, NH3, and H2O displayed inhibitory actions on the efficiency. The performance of CeMnO3 on simultaneous NO and Hg-0 removal was the best at 200-250 degrees C in simulated coal-fired flue gas. Specifically, the NO conversion and Hg-0 removal efficiency were, respectively, 73.7% and 80.9% at 200 degrees C, and both the efficiencies remained excellent stability during a long experimental period. A series of characterization analyses were also carried out to identify the physicochemical properties of the catalysts. The results demonstrated that the superior catalytic performance of CeMnO3 mainly derived from the abundance of chemisorbed oxygen and the great activity of Mn3+ besides Mn4+ in the catalyst.