Catalysts based on pillared interlayered clays for the selective catalytic reduction of NO

The reactivity of an Al-pillared interlayered clay (PILC)(AZA) and a mixed Fe/Al-PILC (FAZA), used as refs. by the Concerted European Action-Pillared Layered Structure (CEA-PLS), was investigated in the selective catalytic redn. (SCR) of NO by NH3 or propane, as either catalysts or as supports of Cu ions. Both AZA and FAZA, either with or without Cu were found to be inactive in the redn. of NO with propane and oxygen. This is different from the behavior with alumina with or without Cu, because of the different surface acidity properties. Good NO conversions were obsd. for both PILCs using NH3. The best catalytic performances were shown by FAZA, but the activity of AZA was also remarkable. The addn. of Cu ions to both AZA and FAZA leads to an improvement in the activity in NO conversion and a redn. in the side formation of N2O. The catalytic behavior was found to depend on the method of Cu addn., the Cu loading and the nature of the PILC. With AZA the best results were obtained for a Cu content up to 2 wt%, while further increases in the amt. of Cu resulted in a considerable decrease in the conversion of NO. With FAZA, on the other hand, a high activity was obsd. at up to 3% of Cu introduced by ion exchange. By comparison with other Cu contg. catalysts, Cu-FAZA allows operation in a wider range of reaction temps. due to the reduced rate of side ammonia combustion. The surface acidity properties of AZA and FAZA were also characterized to interpret the above effects. [on SciFinder(R)]