Fig. 6. a) Procedure of the operando diffuse reflectance Fourier transform spectroscopy (DRIFTS) experiment performed. The experiment was conducted after O2 calcination at 550 °C followed by NH3 + O2, NH3 + NO + O2 and NO + O2 reaction at 250 °C with 1000 ppm of NH3 and/or 1000 ppm NO balanced by 5% O2/He. The obtained operando DRIFTS spectra of surface nitrates in b) fresh and c) 850 °C steamed zeolite ZSM-5. The evolution of selective bands representing surface nitrates (upper panel) and adsorbed NH3 (middle panel) were followed and the recorded concentration of effluent gas composition (bottom panel) in the d) fresh and e) 850 °C steamed zeolite Cu-ZSM-5. Missing datapoints at the beginning of the experiment (Fig. 6d and e, bottom panel) are due to values below the limit of detection.
