| abstract |
According to one embodiment, described herein is an exhaust gas after-treatment system that is coupleable in exhaust gas stream receiving communication with an internal combustion engine. The exhaust gas after-treatment system includes a low temperature SCR catalyst configured to reduce NO x in exhaust gas having a temperature below a temperature threshold. The system also includes a normal-to-high temperature SCR catalyst configured to reduce NO x in exhaust gas having a temperature above the temperature threshold. |