Detection of key transient Cu intermediates in SSZ-13 during NH3-SCR deNOx 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 (NOx) by ammonia (NH3). In this work, Cu-SSZ-13 has been studied at 250 degrees 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+/Cu2+ redox, Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) experiments provide spectroscopic evidence for previously postulated intermediates Cu-N(O)-NH2 and Cu-NO3 in the NH3-SCR deNO(x) mechanism and for the role of [Cu2+(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.