Catalyst Oxidation State and Ammonia Sensors Based on Catalyst-Tipped Optical Fibers

Raynella  Connatser, Oak Ridge National Laboratory

ORAL PRESENTATION: Of the myriad contributors to fuel efficiency and emissions reduction in internal combustion engines, the guided development and precise control of aftertreatment components plays a significant role. The research described here has the dual objectives of increasing fundamental knowledge of catalyst state and developing useful diagnostic hardware. The luminescence of active copper centers in zeolite frameworks is exploited to help address aspects of catalyst development including ammonia storage, reaction networks and spatiotemporal utilization, as well as control over the life of the catalyst. Probe construction involves SCR catalyst material adhered via porous sol gels to optical fiber tips and interrogated with sensitive, phase-locked, laser-induced fluorescence detection. These single entry, thermally robust and materially representative probes are useful for ammonia sensing as well as diagnosing the local oxidation state of an SCR catalyst on a wash-coated monolith. Measurements are made using both pure catalyst powder as well as wash coat harvested from the catalyst-under-test itself, in near-real time, at diesel-exhaust-relevant oxygen, temperature, and NOx levels. Fabrication approaches, bench reactor studies using commercial and developmental catalysts, and figures of merit of the diagnostic will be discussed.

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