IB DP Chemistry: SL复习笔记8.3.3 Reducing Sulfur Oxide Emissions

Reducing Sulfur Oxide Emissions

  • The removal of sulfur from fossil fuels can either take place pre-combustion or post-combustion
  • The oxides of sulfur, SOand SO3, are both acidic and toxic gases 
  • Sulfur dioxide is produced naturally during volcanic eruptions, but large quantities have been and continue to be emitted by burning coal, oil and natural gas


  • Pre-combustion of sulfur takes place for coal and petroleum, although it is expensive to remove all the sulfur, so a small percentage often remains
    • For example, the average sulfur content of gasoline is 347ppm (this is the same as 347 mg per litre)
  • It is essential to remove most of the sulfur as it damages the workings of internal combustion engines
  • The sulfur is removed by reacting it with hydrogen in a process called hydrodesulfurization
  • The sulfur is recovered and used in the manufacture of sulfuric acid


  •  Post-combustion is carried out on in coal-fired power stations
  • The waste gases from burning the coal contain sulfur dioxide
  • The waste gases are passed through a wet slurry of calcium oxide and calcium carbonate which react with the SOand produce calcium sulfate

CaO (s) + SO(g) + ½O2 (g) →  CaSO(s)

CaCO(s) + SO(g) + ½O2 (g) →  CaSO(s)  + CO(g)

  • The calcium sulfate is also known as gypsum and is used to make plasterboard and other useful building materials

What does the future hold?

  • Global policies working towards combating global warming will have the additional benefit in reducing acid deposition
  • As we switch away from burning fossil fuels for energy there will be a fall in the emission of oxides of sulfur and nitrogen, which can only be a good thing for the environment
  • Ultimately reducing the emission of primary pollutants is achieved by greater use of renewable energy sources, greater use of public transport and more efficient energy transfer systems