Bulk and surface properties of dispersed CuO phases in relation with activity of NOx reduction

Synthesized silicas modified with alumina, titania, and zirconia (about 13% wt) were used as supports for dispersing nanosized CuO phase. All the prepared catalysts, containing about 1 mmolcu gcat -1, possessed high surface areas (230-430 m2 g cat-1) and homogeneous coverage of the relevant support, as revealed by SEM-EDS analysis. The nature of the support and its acidity directed the CuO deposition modifying the dimensions of the CuO aggregates and the ratio between highly and scarcely interacting copper species with support, as revealed by complementary analyses. The redox character of the CuO phase was studied realizing cycles of programmed temperature reduction/oxidation (TPR-TPO) which gave the extent of CuO reduction and Cu(O) reoxidation. Deconvolution of the reduction profiles permitted identifying different copper species which presence depended on the support nature. Attempts were made to individuate relations between the properties of the CuO species and catalytic activity in NOx reduction with ethene (HC-SCR process) in highly oxidant atmosphere. The CuO phase deposited on the most acidic supports showed the best activity and selectivity in the NOx reduction.