Comparative study on the direct decomposition of nitrous oxide over M (Fe, Co, Cu)–BEA zeolites

Catalytic activities of M (Fe, Cu, Co)–beta (BEA) zeolites for N2O direct decomposition were systematically investigated by employing both experimental and theoretical [density functional theory (DFT)] approaches. The activities of M–BEA determined by intrinsic kinetic evaluations are in good agreement with the DFT calculations and the microkinetic analyses, revealing that the distinguishing activities of M–BEA were mainly attributed to their distinct energy barriers for the O2 desorption (Part 3). During the DFT calculations, a unique intermediate (IM) was generated only over Co–BEA, which was verified by the activity evaluation and N2O-TPD experiments, showing that the formation of IM reduced N2O decomposition rate of Co–BEA. The negative effect of the IM was thereafter investigated by the microkinetic analyses through which it was known that the second forward reaction rate constant of Co–BEA was lower than its reverse reaction rate constant, resulting in a final decline of the N2O decomposition rate.

Graphical abstractCatalytic performances of M (Fe, Cu, Co) -BEA zeolites for N2O direct decomposition were comparatively investigated revealing that the distinguishing activities of M–BEA were mainly attributed to their distinct energy barriers for the O2 desorption resulting in an activity sequence Co–BEA > Fe–BEA > Cu–BEA. The transition metal ions serving as the active sites for N2O decomposition were confirmed to be the main species existing on the M–BEA. A unique intermediate (IM) was generated only over Co–BEA, which could slow down the N2O decomposition. This negative effect of the IM was thereafter investigated by the microkinetic analysis through which it was known that the second forward reaction rate constant of Co–BEA was lower than its reverse reaction rate constant, leading to a final decline of the N2O decomposition rate.Figure optionsDownload full-size imageDownload high-quality image (193 K)Download as PowerPoint slideHighlights► N2O direct decomposition mechanisms over M–BEA (M = Fe, Co, Cu) were comparatively investigated. ► Activity differences of M–BEA were due to the distinct energy barriers of O2 desorption. ► An intermediate was merely generated over Co–BEA reducing its N2O decomposition rate. ► Microkinetic analyses quantitatively explained the activity differences of M–BEA.