The MnOx-TiO2/MWCNTs nanocomposites were used as De-NOx catalysts to study the deep-rooted reason for the deactivation. Based on a series of characterization on as-prepared catalyst and poisoned catalyst, the results showed that the chief culprit for the deactivation is the micropores in the De-NOx catalyst. The formed ammonium (bi)sulfate in the micropores during the SCR reaction process could not be took away by the gas flow soon and then deposited on the catalyst surface gradually, and further covered the active sites. And the poisoned catalysts could be recovered partly rather than fully by heat treatment at 500 °C because of the decomposition of the ammonium (bi)sulfate and the phase transition of the TiO2.
Financial support was provided by the National Key Research and Development Program of China (Project No. 2018YFB0105900).