1. 6.2.4 Catalytic Converters

2. Exhaust fumes major source of pollution
CO [poisonous]
NO [forms acid rain / poisonous]
NO2 [forms acid rain / poisonous]
[Oxides of nitrogen often referred to as NOx]
Unburned hydrocarbons e.g. C2H [poisonous / carcinogenic / form smog]
Need to reduce pollution as much as possible
Catalytic converter changes these into harmless gasses [ CO2, H2O and N2]
Compulsory since 1993

3. Looks just like any other silencer box

4. Removal of Pollutants
CO reacts with oxides of nitrogen to form CO2 and N2
CO + NOx = CO2 + N2
Umburned hydrocarbons react with oxides of nitrogen to form CO2, N2 and H2O
C2H4 + NOx = CO2 + H2O + N2

5. CO + NOx = CO2 + N2 C2H4 + NOx = CO2 + H2O + N2 CO2 N2 H2O Pt, Pd, Rh
Catalysts
Pollutants NO
NO2 CO
Cross-section
C2H4

6. Calalysts are Pt, Pd, Rh
Coated on a ceramic honeycomb to give large surface area [2-3 soccer pitches]
Good example of heterogeneous catalysis [ i.e. reactants and catalyst in different states]
Work best at high temperatures [300oC]

7. Destruction of Converter
Last about miles
Ceramic breaks down due to high temperature and vibration
Catalysts Poisoned by Pb and other heavy metals
Using leaded petrol destroys catalysts at once
Most of the catalysts can be recovered

8. Catalytic Converters
Reduce
Pollution
Acid rain
Photochemical smog