Addition of 0.5% H-2 in the selective catalytic reduction of NO by urea (urea-SCR) caused a drastic improvement of NO reduction activity of Ag/Al2O3. Among various silver-based catalysts Ag/Al2O3 showed highest activity for H-2 assisted urea-SCR, and high NO conversion (above 84%) and no formation of N2O were achieved over wide temperature range (200-500 degrees C) at GHSV of 75,000 h(-1). After H-2 assisted urea-SCR at 250 degrees C with 10% H2O and 50 ppm SO2 under GHSV of 380,000 h(-1) for 24 h, NO conversion over Ag/Al2O3 decreased from 48 to 30%, though original activity was recovered when the deactivated catalyst was heated at 500 degrees C in the urea-SCR condition for 1 h. The catalyst also showed high SO2-tolerance in H-2 assisted NH3-SCR at 200 degrees C. (C) 2007 Elsevier B.V. All rights reserved.