Question

Catalytic converters, which are fitted into automobiles for reducing the emission of poisonous gases possess which of the following metals as a catalyst?
(A) Platinum-Palladium
(B) Rhodium
(C) Lead
(D) Both (A) and (B)

Answer 1

Hint: Catalytic converters are used in combustion engines to reduce the emission of harmful pollutants such as CO, NO, ${NO_2}$, hydrocarbons etc. They work by catalyzing a redox reaction with certain metals as a catalyst.

Complete answer:
Catalytic converters used to reduce the emission of poisonous gases possess metals like Platinum-Palladium and Rhodium that help to filter the exhaust gases that pass through the converters. These converters are exhaust emission control devices that reduce the release of pollutants in the exhaust gas from a combustion engine by catalyzation process of a redox reaction.
The construction of a catalytic converter is explained below-
-The automotive converter has a honeycomb-structured core that is usually a ceramic monolith. The substrate has a structure that can produce a large surface area. Where high heat resistance is required, the ceramic monolith is replaced by a metallic foil monolith made of Kanthal.
-The catalytic material is carried by the washcoat that disperse the material over a large surface area. For this washcoat, compounds like aluminium oxide, titanium dioxide, a mixture of silica and alumina etc are used.
-As oxygen storage promoters, ceria-zirconia oxides are added in the promoter.
-The catalyst metals are mainly from the platinum group like Palladium and Rhodium. Palladium is used as an oxidation catalyst and rhodium as a reduction catalyst whereas platinum is used for both reduction and oxidation.

So, the correct answer to the question is "Both (A) and (B)".

Note:
There are several types of catalytic converters used for the reduction of pollutants. These are- two-way converter, three-way converter, and diesel oxidation catalyst (DOC). The most commonly used converter for compression- ignition engines or diesel engines is the DOC. The two-way converter is used widely in diesel engines to reduce hydrocarbon and carbon monoxide emission whereas three-way converter reduces the emission of NO and ${NO_2}$.