Site energy distribution of copper catalytic surfaces from volumetric data collected at various temperatures

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°C). A thermodynamic model was applied to the isotherms in order to describe the behaviour of the NO–Cu system in terms of surface energy distribution of Cu sites. The higher loading copper sample had more energetic interaction with NO (−171<ΔaH (kJ/mol) <−44), with higher heterogeneity, than the less loaded one (−111<ΔaH (kJ/mol) <−41). The properties of the Cu sites were related with the activity measured in the SCR of NO with ethylene.