Selective Catalyst Reduction (SCR)

BM Catalysts has expanded its product offering by adding Selective Catalyst Reduction (SCR) references to its range, alongside it’s established range of catalytic converters, DPFs and front pipes.

What is SCR?

SCR technology was first introduced by the Japanese in the 1970s and is often found in power plants, marine vessels and heavy duty vehicles, as it is one of the most cost and fuel effective ways of reducing nitrogen oxide (NO) and nitrogen dioxide (NOx) emissions.

The technology has since become more commonplace to treat emissions from diesel engines over 1.5L, following the introduction of Euro 6 emissions standards in 2015, which cut permitted NOx emissions by more than 50%. SCR technology can reduce a vehicle’s NOx emissions by up to 90%, whilst also reducing hydrocarbons, carbon monoxide and particulate matter emissions.

How does SCR work?

SCR technology works by injecting a liquid-reductant agent through a special catalyst into the exhaust stream of the vehicle. This reductant is an automotive grade urea solution comprised of approximately 1/3 ammonia and 2/3 water. It is more commonly referred to as a diesel exhaust fluid (DEF) and it triggers a chemical reaction that converts NOx into nitrogen, carbon dioxide and water vapour.

Ammonia is highly reactive with NOx in the oxidising atmosphere of the vehicle exhaust. This is where the ‘selective’ part of the name comes from. The chemical reaction itself is known as ‘reduction’, hence the name Selective Catalyst Reduction.

What is it made from?

SCR catalyst substrates are typically made from the same ceramic honeycomb material as standard automotive catalysts. They are generally coated with either oxides of base metals, such as vanadium, or zeolites of copper or iron.

Early SCR systems tended to place the urea/DEF injector SCR catalyst downstream of other emissions control devices. It is now becoming increasingly common to see parts containing both SCR and DPF substrates, or even in some cases a single DPF substrate coated as an SCR catalyst. It is also quite common to see a final catalyst installed after the SCR catalyst in the exhaust system to remove any remaining ammonia.

Click here to purchase BM Catalyst SCR - Exhausts, Cats & DPF's