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16 Sulfur 

Sulfur sources and uses

  • Sulfur is found in its elemental state underground in the USA, Mexico and Poland

  • It is also a by-product from the removal of sulfur from petroleum and natural gas

  • Sulfur can also be obtained from sulfide ores

  • The main use of sulfur is in making sulphuric acid which is a very important chemical used in many industries

  • It is also used extensively in making rubber tyres more flexible (vulcanising), where the rubber is heated with sulfur

Sulfur dioxide

  • Sulfur dioxide can be made by burning sulphur in air

  • This is the method used in the first stage of the manufacture of sulfuric acid

  • Sulfur dioxide is used as a bleach in the manufacture of wood pulp for paper, and as a preservative for foods and drinks by killing bacteria

  • Sulfites are often added to foods and these release sulfur dioxide in acidic conditions

Sulfuric Acid : Properties, Manufacture and uses

  • Sulfuric acid is synthesised by the Contact process which use sulfur and oxygen from air and is done in three distinct stages

    The Contact Process

    Stage 1

  • The first stage is the oxidation of sulfur:

    • S + O2 → SO2

Stage 2

  • The main stage is the oxidation of sulfur dioxide to sulfur trioxide using a V2O5 catalyst:

  • The conditions for the main stage of production of sulfur trioxide need to be considered

Conditions during Stage 2

Temperature 450°

  • The reaction is exothermic, so increasing the temperature shifts the position of equilibrium to the left in the direction of the reactants

  • Therefore the higher the temperature, the lower the yield of sulfur trioxide

  • The optimum temperature is a compromise between a higher rate of reaction at a higher temperature and a lower equilibrium yield at a higher temperature

Pressure: 2 atm

  • An increase in pressure shifts the position of equilibrium to the right in the direction of a smaller number of gaseous molecules

  • However the position of equilibrium lies far to the right (the equilibrium mixture contains about 96% sulfur trioxide)

  • So the reaction is carried out at just above atmospheric pressure because:

    • it is not worth spending the extra energy or money required to produce high pressures

    • a higher pressure causes the sulfur dioxide to liquefy

Stage 3

  • Once stage 2 is completed, the sulfur trioxide is absorbed into a solution of 98% sulphuric acid to produce a thick liquid called oleum:

    • SO3 + H2SO4 → H2SO7

  • It is not absorbed into water because a fine mist of sulfuric acid would be produced and this would be difficult to condense and is also highly dangerous

  • Oleum is added to water to form concentrated sulfuric acid:

Properties of sulfuric acid

  • Sulfuric acid is a strong dibasic acid as two of its hydrogen atoms can be replaced by a metal

    • Mg + H2SO4  → MgSO4 + H2

  • It reacts in a similar way to other acids with metal carbonates, oxides, hydroxides (and ammonia) and metals, e.g:

    • Na2CO3 + H2SO4  → Na2SO4 + CO2+ H2O

    • ZnO + H2SO4  → ZnSO4 + H2O

  • Concentrated sulphuric acid is corrosive and a powerful oxidising agent

  • Concentrated sulphuric acid is also a very powerful dehydrating agent and is very good at removing water from other substances

  • For example, if mixed with sugar (C6H12O6), concentrated H2SO4 will remove water molecules and leave behind carbon in a spectacular looking black tower

Uses of Sulfuric Acid

In dilute solution it is used as a catalyst in many organic reactions and to clean the surface of metals

  • Concentrated sulfuric acid is used in car batteries, making fertiliserssoaps and detergents

  • It is also used to make acid drain cleaners and in the production of paints and dyes





DM

16 Sulfur 

Sulfur sources and uses

  • Sulfur is found in its elemental state underground in the USA, Mexico and Poland

  • It is also a by-product from the removal of sulfur from petroleum and natural gas

  • Sulfur can also be obtained from sulfide ores

  • The main use of sulfur is in making sulphuric acid which is a very important chemical used in many industries

  • It is also used extensively in making rubber tyres more flexible (vulcanising), where the rubber is heated with sulfur

Sulfur dioxide

  • Sulfur dioxide can be made by burning sulphur in air

  • This is the method used in the first stage of the manufacture of sulfuric acid

  • Sulfur dioxide is used as a bleach in the manufacture of wood pulp for paper, and as a preservative for foods and drinks by killing bacteria

  • Sulfites are often added to foods and these release sulfur dioxide in acidic conditions

Sulfuric Acid : Properties, Manufacture and uses

  • Sulfuric acid is synthesised by the Contact process which use sulfur and oxygen from air and is done in three distinct stages

    The Contact Process

    Stage 1

  • The first stage is the oxidation of sulfur:

    • S + O2 → SO2

Stage 2

  • The main stage is the oxidation of sulfur dioxide to sulfur trioxide using a V2O5 catalyst:

  • The conditions for the main stage of production of sulfur trioxide need to be considered

Conditions during Stage 2

Temperature 450°

  • The reaction is exothermic, so increasing the temperature shifts the position of equilibrium to the left in the direction of the reactants

  • Therefore the higher the temperature, the lower the yield of sulfur trioxide

  • The optimum temperature is a compromise between a higher rate of reaction at a higher temperature and a lower equilibrium yield at a higher temperature

Pressure: 2 atm

  • An increase in pressure shifts the position of equilibrium to the right in the direction of a smaller number of gaseous molecules

  • However the position of equilibrium lies far to the right (the equilibrium mixture contains about 96% sulfur trioxide)

  • So the reaction is carried out at just above atmospheric pressure because:

    • it is not worth spending the extra energy or money required to produce high pressures

    • a higher pressure causes the sulfur dioxide to liquefy

Stage 3

  • Once stage 2 is completed, the sulfur trioxide is absorbed into a solution of 98% sulphuric acid to produce a thick liquid called oleum:

    • SO3 + H2SO4 → H2SO7

  • It is not absorbed into water because a fine mist of sulfuric acid would be produced and this would be difficult to condense and is also highly dangerous

  • Oleum is added to water to form concentrated sulfuric acid:

Properties of sulfuric acid

  • Sulfuric acid is a strong dibasic acid as two of its hydrogen atoms can be replaced by a metal

    • Mg + H2SO4  → MgSO4 + H2

  • It reacts in a similar way to other acids with metal carbonates, oxides, hydroxides (and ammonia) and metals, e.g:

    • Na2CO3 + H2SO4  → Na2SO4 + CO2+ H2O

    • ZnO + H2SO4  → ZnSO4 + H2O

  • Concentrated sulphuric acid is corrosive and a powerful oxidising agent

  • Concentrated sulphuric acid is also a very powerful dehydrating agent and is very good at removing water from other substances

  • For example, if mixed with sugar (C6H12O6), concentrated H2SO4 will remove water molecules and leave behind carbon in a spectacular looking black tower

Uses of Sulfuric Acid

In dilute solution it is used as a catalyst in many organic reactions and to clean the surface of metals

  • Concentrated sulfuric acid is used in car batteries, making fertiliserssoaps and detergents

  • It is also used to make acid drain cleaners and in the production of paints and dyes