Detection of key transient Cu intermediates in SSZ-13 during NH(3)-SCR deNO(x) by modulation excitation IR spectroscopy

The small pore zeolite Cu-SSZ-13 is an efficient material for the standard selective catalytic reduction of nitrogen oxides (NO(x)) by ammonia (NH(3)). In this work, Cu-SSZ-13 has been studied at 250 °C under high conversion using a modulation excitation approach and analysed with phase sensitive detection (PSD). While the complementary X-ray absorption near edge structure (XANES) spectroscopy measurements showed that the experiments were performed under cyclic Cu(+)/Cu(2+) redox, Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) experiments provide spectroscopic evidence for previously postulated intermediates Cu–N([double bond, length as m-dash]O)–NH(2) and Cu–NO(3) in the NH(3)-SCR deNO(x) mechanism and for the role of [Cu(2+)(OH(–))](+). These results therefore help in building towards a more comprehensive understanding of the reaction mechanism which to date has only been postulated in silico.