Petrol catalytic converters are predominantly designed for removing three primary pollutants: hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). They do so by converting these pollutants into less harmful substances such as water, carbon dioxide (CO2), and nitrogen (N2) gas through a series of chemical reactions. Inside a petrol catalytic converter, you will find a ceramic substrate with a honeycomb structure coated with platinum, rhodium, and sometimes palladium. These metals act as catalysts, facilitating the chemical reactions that convert pollutants into harmless substances.
Diesel catalytic converters, on the other hand, are designed to primarily address the pollutants specific to diesel engines. Diesel engines produce high amounts of particulate matter (PM or soot) along with HC, CO, and NOx. To remove these pollutants, diesel catalytic converters use a different approach. They incorporate additional components, such as a diesel oxidation catalyst (DOC) and/or a diesel particulate filter (DPF), in addition to a three-way catalyst (TWC) similar to petrol catalytic converters. The DOC promotes the oxidation of hydrocarbons and carbon monoxide into CO2 and water. The DPF captures and traps soot particles through filtration, while the TWC further reduces NOx emissions by converting them into nitrogen gas.
To summarize, while both diesel and petrol vehicles employ catalytic converters to reduce their emissions, they differ in their specific designs, materials, and approaches based on the different pollutants produced by their respective engine types.
