On a car, the catalytic converter is attached to the exhaust pipe. A metal casing contains a ceramic honeycomb.
The honeycomb is coated with a mix of platinum (Pt), palladium (Pd) and rhodium (Rh). These noble metals are good at resisting oxidation, corrosion and acid.
That means they can stand up to bad weather and all the chemicals released by a car engine.
The noble metals in catalytic converter act as catalysts.
catalytic converter are compounds that can trigger a chemical reaction without being affected themselves. The honeycomb structure inside a catalytic converter maximizes the surface area where reactions can take place.
Catalytic converter use elements like Platinum (Pt), Palladium (Pd), and Rhodium (Rh) as catalysts (Let’s Talk Science using photographs by Periodictableru [CC BY], Hi-Res Images of Chemical Elements [CC BY and Alchemist-hp (talk) derivative work: Purpy Pupple [CC BY-SA 3.0] Wikimedia Commons (https://en.wikipedia.org/wiki/File:Platinum_crystals.jpg“>Pt, https://en.wikipedia.org/wiki/File:Palladium_(46_Pd).jpg“>Pd, https://en.wikipedia.org/wiki/File:Rhodium_powder_pressed_melted.jpg“>Rh)).
What chemical reactions happen in a catalytic converter?
Catalytic converters use reduction and oxidation ( reactions to reduce harmful emissions.
They use a reduction catalyst composed of platinum and rhodium. It helps reduce nitrogen oxides (NOx) by removing nitrogen atoms from nitrogen oxide molecules (NO and NO2). This lets the free oxygen form oxygen gas (O2). Then, the nitrogen atoms attached to the catalyst react with each other. This reaction creates nitrogen gas (N2).
Catalytic converter also use an oxidative catalyst composed of platinum or palladium. It helps reduce hydrocarbons (HC) and carbon monoxide (CO). To start with, carbon monoxide and oxygen combine to form carbon dioxide (CO2). Then, unburnt hydrocarbons and oxygen combine to form carbon dioxide and water.
Oxidation reactions for carbon monoxide and unburned hydrocarbons (© 2019 Let’s Talk Science).Modern catalytic converters also use oxygen sensors. They’re sometimes called . They control how much extra oxygen gets pumped into the exhaust stream.