Johnson Matthey can offer coated and extruded catalysts.
Ammonia-SCR systems react ammonia (NH3) with the NOx to form nitrogen (N2) and water (H2O). There are three reaction pathways:
Any source of ammonia can be used but most commonly the source is an aqueous solution of urea. This decomposes in the exhaust stream in two stages to form ammonia and carbon dioxide (CO2):
NH2C(O)NH2 → HNCO + NH3
HNCO + H2O → CO2 + NH3