The balance of acidity and redox capability over modified CeO2 catalyst for the selective catalytic reduction of NO with NH3

The effect of acidity and redox capability over sulfuric acid-modified CeO2 catalysts were studied for the selective catalytic reduction of NOx with NH3 (NH3-SCR). The deposition of sulfate significantly enhanced the catalytic performance over CeO2. NOx conversion over 4H(2)SO(4)/CeO2 at 230-440 degrees C was higher than 90%. The strong redox capability of CeO2 could result in unselective NH3 oxidation and decrease high temperatures catalytic activity and N(2 )selectivity. The deposition of sulfate increased the acidity and weakened the redox capability, and then increased the high temperature NOx conversion and N-2 selectivity. An appropriate level of acidity also promoted the activity at 190-250 degrees C over ceria-based catalysts, and with further increase in the acidity, the SCR activity decreased slightly. Weak redox capability lowered the low-temperature catalytic activity. Excellent SCR activity requires a balance of acidity and redox capability on the catalysts. (C) 2018 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.