1. Catalytic Converters and poisons

2. Rates of Reaction Catalytic Converters Exhaust fumes contain CO –
due to incomplete combustion of hydrocarbons
NO & NO2 –
N2 in air is oxidised at high temperatures
Unburned hydrocarbons

3. Learning Check Can I name the 4 impurities in exhaust fumes?
Can I say why each one is present?

4. Rates of Reaction Catalytic Converters. . .cont’d
Important to decrease emissions as
CO – poisonous
NO & NO2 – toxic and contribute to acid rain
Unburned hydrocarbons – contribute to photochemical smog

5. Rates of Reaction Check ….
Say the problem caused by each of the 4 impurities
CO …….
NO and NO2…….
Unburned hydrocarbons……

6. Rates of Reaction Catalytic converters convert …..
CO, NO and NO2 into harmless gases.
2CO + 2NO  2CO2 + N2
HC’s + NO + NO2  CO2 + N2 + H2O
This is example of heterogeneous catalysis – which phases present?.
They consist of a thin coating of Rh, Pd or Pt on a ceramic or metal honeycomb steel case which has a large surface area.
Rh / Pd / Pt
Rh / Pd / Pt

7. Rates of Reaction Check ….
Write the balanced chemical equation for the removal of CO and NO …….
Write a word equation for the removaal of
Unburned hydrocarbons, NO and NO2…….

8. Rates of Reaction Catalytic Poisons Impurities in a reaction mixture
adsorb onto the surface of a catalyst thus
blocking (removing) potential sites for gas molecules and decreasing efficiency
Expensive
the catalyst has to be replaced (Pt costly) or the process has to be shut down
Examples
sulphur (Haber process)
lead (Catalytic converters in cars)

9. Rates of Reaction Check …. What is a catalytic poison?
How does it stop the catalyst working
Why is it undesirable to poison the catalytic converter?
Example of poison for cat converter in car

10. Also Check ….
Do I know ….
Why catalytic converters are recycled?
Another reason for cat converters not working other than poisons?

11. The End