Patent ID: 8225595

Claim:
An apparatus for estimating an NO x conversion efficiency of at least one selective catalytic reduction (SCR) catalyst, the apparatus comprising: a catalyst degradation module configured to determine an SCR catalyst degradation factor associated with the at least one SCR catalyst; an NO x concentration module configured to determine an SCR catalyst inlet NO x concentration; an NH 3 concentration module configured to determine an SCR catalyst inlet NH 3 concentration; a space velocity (SV) module configured to determine an exhaust gas SV for the SCR catalyst based at least partially on a set of operating parameters; a temperature module configured to determine an SCR catalyst bed temperature; and a NO x conversion efficiency module configured to calculate a NO x conversion efficiency value for the at least one SCR catalyst based at least partially on the SCR catalyst degradation factor, the SCR catalyst inlet NO x concentration, the SCR catalyst inlet NH 3 concentration, the exhaust gas SV, and the SCR catalyst bed temperature.