(24g) Nitrate Formation/Decomposition On Ba-, and K-Based Model LNT Catalysts: Similarities and Differences

Kim, D. H., Pacific Northwest National Laboratory
Kwak, J. H., Pacific Northwest National Laboratory

Diesel engines are a promising near-term solution for obtaining high energy efficiency because of their unparalleled power density and low CO2 emissions.  However, there are challenges for the catalytic aftertreatment systems, especially due to the necessity to selectively reduce nitrogen oxides (NOx) in the net oxidizing environment.  NOx storage-reduction (NSR) catalysts are generally considered as one of the potential options for removing NOx in the diesel engine exhaust.  In the NSR technology, alkali or alkaline earth elements (K or Ba) take up NOx under lean operation and store them as nitrates, which are subsequently reduced during rich operation.  In this presentation, we compare the characteristics of Ba and K storage elements during NOx adsorption and desorption processes using multiple techniques, including TR-XRD, FTIR and NO2 TPD.  We find that, although both elements store NOx as nitrates, there are significant differences between the morphology changes of the Ba and K nitrates.