Effects of oxygen and hydrogen chloride on NO removal efficiency by Rh/Al2O3 and Rh-Na/Al2O3 catalysts

The influences of oxygen, hydrogen chloride, and sodium modification on the activity of the Rh/Al2O3 catalyst for NO removal were investigated in simulated waste incineration conditions. The characterizations of the catalysts were analyzed by SEM/EDS, XRD, and ESCA. Experimental results indicated that the Rh/Al2O3 catalyst has high stability and activity for NO removal over a range of 0-20% O-2. The addition of Na promoted the activity and N-2 selectivity of the Rh/Al2O3 catalyst, but an increase in NO2 selectivity was observed when oxygen concentration and reaction time increased. The Rh/Al2O3 catalyst gradually deactivated on both NO and CO conversions when HCl concentration increased to 500 ppm because of the formation of RhCl3. The Rh-Na/Al2O3 catalyst has a low activity for NO conversion, but 100% CO conversion still remained even though 500 ppm HCl was contained in the feed gas. The Na added to the Rh/Al2O3 catalyst can react with HCl to form NaCl, resulting in a suppressed deactivation for Rh active sites. Low HCl concentrations do not affect NO2 selectivity of the Rh/Al2O3 catalyst but do decrease that of the Rh-Na/Al2O3 Catalyst. (C) 2009 Elsevier B.V. All rights reserved.