Two catalysts prepared on a titanium silicate (ETS-10) matrix by loading 6 and 11 wt.% of copper were studied by employing nitrogen monoxide as adsorbate to probe the surface properties of copper centres. Volumetric isotherms of NO adsorption were collected at different temperatures (19-70 degreesC). A thermodynamic model was applied to the isotherms in order to describe the behaviour of the NO-Cu system in ten-ns of surface energy distribution of Cu sites. The higher loading copper sample had more energetic interaction with NO (-171 < Delta H-a (kJ/moI) < -44), with higher heterogeneity, than the less loaded one (-111 < Delta H-a (kJ/mol) < -41). The properties of the Cu sites were related with the activity measured in the SCR of NO with ethylene.