Selective catalytic reduction of nitrogen monoxide by decane on copper-exchanged beta zeolites

The selective catalytic reduction (SCR) of NO by decane has been investigated on a series of copper exchanged beta zeolite (BEA), and the catalytic behaviour has been compared to Cu-MFI. The different solids were characterised by temperature programmed reduction by it, and temperature programmed desorption of NO in order to determine the nature, reducibility and accessibility of copper species. Only CuO aggregates are formed on Cu/H-BEA whatever the Cu content. By contrast, isolated CU2+ are the main species occurring on Cu/Na-BEA when Cu exchange level is lower than 120% and the accessibility to Cu sites is high (NO/Cu greater than or equal to 0.45). At higher content, CuO aggregates exists too, and the accessibility decreases to NO/Cu approximate to 0.29. The activity in SCR of NO by decane of Cu/Na-BEA goes through a maximum for 113% Cu exchange, This sample is less active than Cu/MFI at high temperature, but much more active at low temperature. The intrinsic activity at 673 K per accessible Cu site remains very similar for the different Cu/Na-BEA samples. This is attributed to temperatures of the reduction step CU2+--> Cu+ very close whatever the copper content.