Tracking mobile active sites and intermediates in NH3-SCR over zeolite catalysts by impedance- based in situ spectroscopy

摘要

Integrated investigations combining experimental and theoretical methods have promoted significantly the fundamental understanding of zeolite-based ammonia selective catalytic reduction (NH3-SCR), a key tech- nology for the abatement of automotive nitrogen oxide emissions. One representative finding is that site- isolated Cu ions within zeolite catalysts are solvated and mobilized in the NH3-SCR reaction at low temper- atures. In this minireview, we highlight that impedance-based spectroscopy ( IS), by monitoring the dielectric properties of zeolite catalysts, can be used to track directly the dynamic Cu ion motion under NH3-SCR reaction conditions. Further combining IS with diffuse reflectance infrared Fourier trans- form spectroscopy (DRIFTS) allows us to monitor the dynamics of other mobile species involved in NH3- SCR catalysis, for example ammonium ion (NH4 +) intermediates resulting from the redox of metal active