Motor vehicles equipped with catalytic converter should run on unleaded petrol .give reason?

1 Answer
Dec 3, 2017

See below.


The catalytic converters contain Palladium, Platinum, or Rhodium catalysts. Leaded petrol contains Tetraethyl lead {TEL}, hence the name leaded petrol. It is added to decrease the knocking of the engine (the metallic sound produced due to the irregular burning of the fuel in the engine is termed as knocking).

We all prefer a fuel with minimum knocking property and it increases the efficiency and life of the engine. Antiknock compounds are thus used; they are a mixture of TEL(66%), Ethylene bromide(26%), Ethylene chloride(9%), and a dye (2%).

It is believed that the TEL dissociates to give ethyl free radicals and converts straight chain to branched#rarr# the reason for its use is that branched chain organic compounds have less knocking property.

Pd is deposited as the byproduct of reaction and combines with ethylene halides that are added to remove the deposited Pd in the engine.

Lead halides are volatile. These volatile lead halides poison the catalyst and the catalyst loses its property.

#"Pb" + "Br"-"CH"_2-"CH"_2-"Br" rarr "PbBr"_2 ("volatile") + "ethylene"#

Unleaded petrol does not contain TEL; instead, other methods are used,