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Alkali Metal Deactivation on the Low Temperature Selective Catalytic Reduction of NOx with NH3 over MnOx‑CeO2: A Mechanism Study
journal contribution
posted on 2016-07-01, 00:00 authored by Shangchao Xiong, Jingxia Weng, Yong Liao, Bo Li, Sijie Zou, Yang Geng, Xin Xiao, Nan Huang, Shijian YangThe
application of MnOx-CeO2 as
the low temperature selective catalytic reduction (SCR) catalyst
to control NOx emission from coal-fired
power plants is extremely restricted due to the unrecoverable deactivation
by SO2. There is little SO2 in the flue gas
from biomass-fired power plants, and the concentration of alkali metals
in the flue gas after the electrostatic precipitator is very low,
so the application of MnOx-CeO2 may be possible to control NOx emission
from biomass-fired power plants. However, a very small amount of alkali
metals showed a seriously negative effect on NO reduction over MnOx-CeO2 such that both NOx conversion and N2 selectivity obviously
decreased. In this work, the mechanism of NO reduction over MnOx-CeO2 and K-MnOx-CeO2 was investigated by the transient reaction
study and the kinetic parameters of NO reduction were obtained from
the steady-state kinetic study. After comparison of the kinetic parameters,
the mechanism of potassium deactivation on NO reduction over MnOx-CeO2 was discovered. The decrease
of the SCR activity of MnOx-CeO2 after potassium deactivation was mainly attributed to the decrease
of acid site and Mn4+ concentration on the surface, and
the increase of N2O selectivity was mainly related to the
occurrence of N2O formation over K-MnOx-CeO2 through the Langmuir–Hinshelwood mechanism.