Hydrothermal stability of Cu/Chabazite catalysts has been extensively studied, yet atomic level understanding on changes to the zeolite support and the Cu active sites during hydrothermal aging are still lacking. In this work, via the utilization of spectroscopic methods including solid-state 27Al and 29Si NMR, EPR, DRIFTS and XPS, together with imaging and elemental mapping using STEM, detailed kinetic analysis, and theoretical calculations with DFT, various Cu species, including two types of isolated active sites and CuOx clusters, can be precisely quantified for samples hydrothermal aged under varying conditions. This quantification convincingly confirm the exceptional hydrothermal stability of isolated Cu2+-2Al sites, and the gradual conversion of [Cu(OH)]+-1Al to CuOx clusters with increasing aging severity. This stability difference was rationalized from the hydrolysis activation barrier difference of the two isolated sites via DFT. Some discussion was given on the nature of the CuOx clusters. Finally, a few rational design principles for Cu/SSZ-13 were derived rigorously from the atomic level understanding of this catalyst.

Towards atomic level understanding of the transformation of Cu active sites in Cu/SSZ-13 selective catalytic reduction catalysts during hydrothermal aging

254th National Meeting (2017)

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