Catalytic Converters and poisons

1. Catalytic Convertersand 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 CheckCan 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