DF10

Photochemical Smog

• Produced by actions of sun’s rays on primary pollutants

• Typically contains ozone

• Causes haziness and reduced visibility

• Leads to irritation and breathing problems

Particulates

• Small carbon particles

  • Below 2.5\(\times\)10^-12m

• From volcanoes and combustion

• Causes heart attacks and lung cancer

Volatile Organic Compounds (VOC’s)

• From unburnt fuel

• Causes photochemical smog

Carbon Monoxide

• From incomplete combustion

• Causes toxic gas and photochemical smog

Carbon Dioxide

• From combustion

• Contributes to the greenhouse effect

Nitrogen Oxides

• From combustion at high temperatures

• Causes acid rain and photochemical smog

Sulfur Oxides

• From volcanoes, and combustion of fuels containing sulfur

• Causes toxic gas and acid rain

Production of Acid Rain

Initially Sulfur Dioxide reacts with water, forming weakc Sulfuric (IV) acid: \[SO_2 + H_2O \Rightarrow H_2SO_3\] However, Sulfur Dioxide is oxidised to Sulfur Trioxide in the stratosphere, which reatcs with water to form strong Sulfuric (VI) acid \[SO_3 + H_2O \Rightarrow H_2SO_4\]
NO\(_x\) reacts with water and oxygen to form strong Nitric(V) Acid, \(HNO_3\)

Petrol Catalystic Converters

Conversion of:

• CO to CO₂

• C_\(x\)H_\(y\) to CO₂ and H₂O

• NO and CO to N₂ and CO₂
  

• Catalyst of Platinum/Rhodium on a porous support

• Sulfur impurities are removed beforehand

Diesel Catalytic Converters

Conversion of:

• CO to CO₂

• C_\(x\)H_\(y\) to CO₂ and H₂O

• NO and CO to N₂ and CO₂
  

• Particulates removed by a ceramic filter

• Sulfur impurities are removed beforehand

• NO_\(x\) removed by recycling the gases through a cylinder, thus lowering the temperature

  • Ammonia and a catalyst can be used \[4NO+4NH_3+O_2 \Rightarrow 4N_2+6H_2O\]