The Industrial Process of Sulphuric Acid
Anissa Davis 32130161
The Industrial Process of Sulphuric Acid6
The contact process:
At the heart of this process is a reversible reaction in which sulphur dioxide is converted to sulphur trioxide, but first you have to produce sulphur dioxide.
Stage 1: Making sulphur dioxide
Either burn sulphur in air:
S (s) + O₂ →SO₂(g)
Or heat sulphide ores strongly in air:
4F eS₂(s) + 11O2(g)→2F e₂O₃(s) + 8SO₂(g)
Stage 2: Making sulphur trioxide
Now the sulphur dioxide is converted into sulphur trioxide using an excess of air from the previous process.
2SO₂ + O₂⇌2SO₃(g) △H =− 196kJ mol
¹
Anissa Davis 32130161
Further reactions In this reaction an excess of oxygen is used, because it is important to make sure that as much sulphur dioxide as possible converted into sulphur trioxide. Having sulphur dioxide left over at the end of reaction is wasteful, and could cause possibly dangerous pollution. Because the forward reaction is exothermic, there would be a higher percentage conversion of sulphur dioxide into sulphur trioxide at a low temperature.
However, at a low temperature the rate of reaction would be very slow. 450◦C is a compromise. Even so, there is about 99.5% conversion
There are three gas molecules on the left hand side of the equation, but only two on the right. Reactions in which the numbers of gas molecules decrease are favoured by high pressures. In this case, though, the conversion is so good at low pressures that it isn’t economically worthwhile to use higher ones.
The catalyst, vanadium (V) oxide, has no effect on the percentage conversion, but helps to speed up reaction. Without the catalyst the reaction would be extremely slow. Stage 3: Making Sulphuric Acid
In principle, you can react sulphur trioxide with water to make sulphuric acid. In practice, this produces an uncontrollable fog of concentrated sulphuric acid.
Instead, the sulphur trioxide is absorbed in concentrated sulphuric acid to give
The Industrial Process of Sulphuric Acid6
The contact process:
At the heart of this process is a reversible reaction in which sulphur dioxide is converted to sulphur trioxide, but first you have to produce sulphur dioxide.
Stage 1: Making sulphur dioxide
Either burn sulphur in air:
S (s) + O₂ →SO₂(g)
Or heat sulphide ores strongly in air:
4F eS₂(s) + 11O2(g)→2F e₂O₃(s) + 8SO₂(g)
Stage 2: Making sulphur trioxide
Now the sulphur dioxide is converted into sulphur trioxide using an excess of air from the previous process.
2SO₂ + O₂⇌2SO₃(g) △H =− 196kJ mol
¹
Anissa Davis 32130161
Further reactions In this reaction an excess of oxygen is used, because it is important to make sure that as much sulphur dioxide as possible converted into sulphur trioxide. Having sulphur dioxide left over at the end of reaction is wasteful, and could cause possibly dangerous pollution. Because the forward reaction is exothermic, there would be a higher percentage conversion of sulphur dioxide into sulphur trioxide at a low temperature.
However, at a low temperature the rate of reaction would be very slow. 450◦C is a compromise. Even so, there is about 99.5% conversion
There are three gas molecules on the left hand side of the equation, but only two on the right. Reactions in which the numbers of gas molecules decrease are favoured by high pressures. In this case, though, the conversion is so good at low pressures that it isn’t economically worthwhile to use higher ones.
The catalyst, vanadium (V) oxide, has no effect on the percentage conversion, but helps to speed up reaction. Without the catalyst the reaction would be extremely slow. Stage 3: Making Sulphuric Acid
In principle, you can react sulphur trioxide with water to make sulphuric acid. In practice, this produces an uncontrollable fog of concentrated sulphuric acid.
Instead, the sulphur trioxide is absorbed in concentrated sulphuric acid to give