In the present work, a series of Cu/SAPO-34 catalysts with varying number of Bronsted acid sites has been prepared by ion exchanging with potassium to investigate the role of Bronsted acidity in the NH3-SCR reaction. The impact of potassium on the structural and acidic properties of Cu/SAPO-34 catalysts has been studied. No significant changes in both the SAPO-34 structure and the copper species were observed in the presence of potassium. With increasing potassium loading, the NH3-SCR activity of the Cu-K/SAPO-34 catalysts decreased in accordance with the decreasing Bronsted acidity. The quantification method of Bronsted acid sites in the Cu-(K)/SAPO-34 was developed by using IR spectroscopy, which was confirmed by acid site generation mechanism and NH3-TPD results. A linear relationship was found between the amounts of Bronsted OH groups determined by DRIFTS and the NH3 desorbed at high temperatures from NH3-TPD. (C) 2015 Elsevier Inc. All rights reserved.