SAPO-34 zeolites with three different Si contents were prepared by hydrothermal synthesis and then around 0.6 wt% Cu was introduced by impregnation. The structure and morphology of the samples were characterised via XRD and SEM techniques, respectively. The acid properties of the different samples were investigated by NH3-TPD. Cu-SAPO-34, with the lowest Si content, exhibits the best efficiency, between 200 and 550 degrees C, in NH3-SCR of NO after ageing treatment under H2O vapour at 850 degrees C for 5 h. For the fast reaction, (NO/NO2), a better efficiency is only observed with respect to the catalyst having low Si content. (C) 2014 Elsevier B.V. All rights reserved.