A series of V2O5 supported sulfated titanium-pillared clay catalysts with various amounts of vanadia were prepared and characterized by BET, DRX, XPS and NH3-TPD then studied for selective catalytic reduction (SCR) of NO by NH3 in the presence of oxygen. It was found that vanadia supported on sulfated Ti-pillared clay is more active at any temperature than sulfated Ti-pillared clay for the SCR of NO by NH3. The NO conversions over V2O5 supported sulfated Ti-pillared clay catalysts were found to increase with vanadia content, but the selectivity into nitrogen decreases upon sulfation, suggesting that there is an optimum of activity as a function of the number of acid sites. (c) 2005 Elsevier B.V. All rights reserved.