We discuss recent findings of an experimental and theoretical collaboration to understand the active site structures and reaction mechanisms that mediate low temperature (&lt;523 K) selective catalytic reduction (SCR) of NOx (x = 1,2) with ammonia on Cu-chabazite zeolites (Cu-SSZ-13). During low temperature SCR catalysis, extraframework Cu ions are solvated by ammonia reactants and liberated from the zeolite lattice. The spatial distribution of isolated Cu sites, which depends on the density (Si/Al ratio) and distribution (isolated vs. paired Al) of framework Al atoms in the underlying zeolite support, is a critical parameter that regulates the dynamic formation of multinuclear Cu complexes during the SCR cycle. We show how quantitative descriptions of Cu ion mobility, and of the number of reactive Cu intermediates formed <i>in situ</i> as a function of catalyst composition and reaction conditions, can be used to develop kinetic models that unify seemingly disparate observations of catalytic function reported previously.

Consequences of Cu ion mobility in zeolites for low temperature NOx SCR with ammonia

254th National Meeting (2017)

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