In emissions catalyst applications, axial distributions in surface and gas-phase species concentrations and temperature exist, thus reaction rate gradients exist as well. To develop and validate physically relevant models of such systems, characterizing these distributions is required. This is especially critical for passive selective catalytic reduction (SCR), where NH3 generated on an upstream catalyst adsorbs on the downstream SCR catalyst for subsequent reaction with NOX. Therefore, there is no continuous input of reductant, and in most cases the NH3 comes to the SCR catalyst as a pulse. In this talk, the effect of NH3 pulse parameters on NH3 adsorption profiles along the catalyst during exposure to NH3 and how these change after exposure, via NH3 migration, will be discussed, as well as the fast and standard SCR reactions over the NH3-covered surfaces.

Measuring reaction parameter gradients in selective catalytic reduction catalysts

244th National Meeting (2012)

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