Monitoring NH3 storage and conversion in Cu-SAPO-34 catalyst for NH3-SCR by simultaneous impedance and DRIFT spectroscopy

Titelangaben

Schönebaum, Simon ; Chen, Peirong ; Simböck, Johannes ; Rauch, Dieter ; Simons, Thomas ; Palkovits, Regina ; Moos, Ralf ; Simon, Ulrich:
Monitoring NH3 storage and conversion in Cu-SAPO-34 catalyst for NH3-SCR by simultaneous impedance and DRIFT spectroscopy.
2016
Veranstaltung: 28. Deutsche Zeolith-Tagung , 2.3.- 4.3.2016 , Gießen.
(Veranstaltungsbeitrag: Kongress/Konferenz/Symposium/Tagung , Poster )

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Abstract

Metal-promoted zeolites (e.g. Cu-ZSM-5, Fe-ZSM-5, Cu-CHA) are widely explored as catalyst material for the selective catalytic reduction of nitrogen oxides by NH3 (NH3-SCR), which is a key technology to control NOx emissions from lean-burn diesel engines for road transport. The development of more efficient zeolite catalysts for NH3-SCR requires insights into both reaction mechanism and real-time state of the catalyst (e.g., the storage level of NH3). Here, we show that impedance spectroscopy (IS) can be applied to sense electrically the uptake of NH3 into proton-conducting, copper-promoted zeolite catalyst, i.e., into Cu-SAPO-34. As compared to the traditional Cu-ZSM-5 catalyst, Cu-SAPO-34 shows a higher SCR efficiency and selectivity towards N2 due to the smaller pore size. Furthermore, Cu-SAPO-34 is more sensitive to the change of NH3 concentration, resulting in a superior performance for the purpose of monitoring directly the SCR conversion of stored NH3 at temperatures from 100 °C to 400 °C. A simultaneous IS and diffuse reflection infrared Fourier transform spectroscopy (IS-DRIFTS) study allows a molecular understanding of the NH3 sensing and NH3-SCR monitoring behaviors of Cu-SAPO-34. The correlation of integral electrical responses with molecular processes, achieved by our simultaneous IS-DRIFTS studies, not only clarifies the origin of the sensing mechanism of Cu-SAPO-34 catalysts at a molecular level, but also provides a new perspective to understand the NH3-SCR mechanism over metal-promoted zeolites at low reaction temperatures.