Characterization of Ruthenium-Exchanged Zeolites (Beta, Y, and ZSM-5) by EPR Spectroscopy

Ruthenium-exchanged zeolites, Ru–Beta, Ru–Y, and Ru–ZSM-5, are active catalysts for the decomposition of nitrous oxide, N2O. [Ru(NH3)6]3+ was exchanged into zeolites Y, Beta, and ZSM-5. The resulting ruthenium-exchanged zeolites were characterized by electron paramagnetic resonance (EPR) spectroscopy and were tested for N2O decomposition activity. The decomposition of the [Ru(NH3)6]3+ complex in the zeolites during pretreatment in helium at elevated temperatures was monitored using EPR spectroscopy. Ru–Beta and Ru–Y exhibited similar EPR spectra that were interpreted in terms of loss of amine ligands, formation of aquo and hydroxyl ruthenium complexes, and eventual loss of all ligands with binding to zeolitic oxygen. The EPR spectra of Ru–ZSM-5 exhibited some similar spectral features with the exception of the initial [Ru(NH3)6]3+ complex. The presence of a specific ruthenium species observed by EPR was correlated with the catalytic activity of Ru–Y.