April 2020

pass over a specially coated ceramic ‘brick’ at the heart of the unit, which triggers a chemical reaction to start breaking down the undesirable NOx, amongst other pollutants. The reaction acts to break apart the nitrogen and oxygen atoms that have come together under the heat and pressure conditions created in the engine’s cylinders, allowing the oxygen to reattach to the CO and HC to produce less toxic and naturally occurring carbon dioxide (CO2) and water (H2O). Although rising CO2 levels are of great concern for climate T he internal combustion engine uses fossil fuels and subsequently produces harmful emissions. That’s an inescapable fact. The hydrocarbons used, usually diesel or petrol, are combined with oxygen to provide a source of energy for the explosions that power the piston’s movement and propel the vehicle. Chemical reactions during combustion mean atoms are realigned under extreme pressure, creating exhaust gases that include 52 AFTERMARKET APRIL 2020 TECHNICAL www.aftermarketonline.net COUNTING THE COST OF CONVERSION BM Catalysts MD Toby Massey weighs-in on why cleaner air comes at a high price nitrogen combined with any number of oxygen atoms (NOx), unburnt hydrocarbons (HC), carbon monoxide (CO) and various other impurities that were there before ignition. It is this NOx that is considered extremely harmful to humans and is the current target for reduction and removal by post-combustion devices like catalytic converters and selective catalytic reduction (SCR) systems. It is important to understand that a catalytic converter is not a filter. The exhaust gases exiting an internal combustion engine are channeled to BY By Toby Massey, Managing Director, BM Catalysts