Technologies -> Selective Catalytic Reduction -> Hydrocarbon-SCR

Hydrocarbon-SCR (lean NOx reduction) systems use hydrocarbons as the reductant. The hydrocarbon may be that occurring in the exhaust gas (“native") or it may be added to the exhaust gas. This has the advantage that no additional reductant source (e.g. urea) need be carried but these systems cannot offer the performance of ammonia-SCR systems.

The reaction pathways depend on the hydrocarbon used but the following describes the total reaction in the system:

[HC] + [NOx] -> N₂ + CO₂ + H₂O

Two alternative HC-SCR systems are available, with different operating temperature windows, as shown in the chart: