Selective catalytic reduction catalyst system with expanded temperature window

A durable catalyst system for the reduction of emissions from an engine exhaust stream, comprising:

• a light-off catalyst closely coupled to the engine;
• a first copper selective catalytic reduction catalyst positioned downstream of the light-off catalyst;
• a reductant injection system positioned between the light-off catalyst and the first copper selective catalytic reduction catalyst;
• a diverter valve positioned downstream of the location for reductant injection and upstream of the first copper selective catalytic reduction catalyst, the diverter valve being connected to a bypass arm that can be utilized to bypass the first copper selective reduction catalyst and improve NOx conversion under high temperature conditions;
• and
• a second catalytic reduction catalyst that includes a first Fe SCR catalyst and a second Cu SCR catalyst, wherein the second Cu SCR catalyst is positioned downstream of the Fe SCR catalyst.