Heterogeneous catalyst

1. A catalyst is a substance which affects the rate of a chemical reaction without being chemically changed itself.

2. Heterogeneous catalyst The catalyst is in a different phase to the reactants (eg solid catalyst with liquid reactants) For example Fe in the Haber process Ni in margarine production Pt and Rh in a catalytic converter

3. Heterogeneous catalysts The Haber process

4. Hardening of fats

5. Incomplete combustion of fuels leads to products such as CO and NO. These react in the presence of UV rays (from sunlight) to produce low level ozone, aldehydes and PAN (peroxyacetylnitrate CH3CO-OO-NO2) collectively known as photochemical smog. Ozone causes breathing difficulties, headaches, fatigue and can aggravate respiratory problems. PAN can irritate the eyes, causing them to water and sting. In a catalytic converter, a rhodium catalyst is used to break NO into N2 and O2

6. Homogeneous catalyst The catalyst is in the same phase as the reactants For example Cl radicals in the destruction of ozone H+ in Esterification

7. Homogeneous catalysts • Ozone O3 forms a layer around the atmosphere which acts as a shield preventing too much UV radiation from reaching earths surface. • CFCs decompose in the upper atmosphere producing chlorine free radicals. • These radicals act as a catalyst for the reaction O3 + O 2O2

8. Homogeneous catalysts Esterification