Describe the physico-chemical principles involved in the manufacture of H2SO4 by contact process.
Answers
Explanation:
Most of the sulfuric acid manufactured is produced using the Contact Process.
1. Solid sulfur, S(s), is burned in air to form sulfur dioxide gas, SO2
S(s)+O
2
(g)→SO
2
(g)
The gases are mixed with more air then cleaned by electrostatic precipitation to remove any particulate matter
3. The mixture of sulfur dioxide and air is heated to 450
0
and subjected to a pressure of 101.3 - 202.6 kPa (1 -2 atmospheres) in the presence of a vanadium catalyst (V
2
O
5
) to produce sulfur trioxide, SO
3
(g), with a yield of 98%.
2SO
2
+O
2
→2SO
3
Any unreacted gases from the above reaction are recycled back into the above reaction
4. Sulfur trioxide, SO
3
(g) is dissolved in 98% (18M) sulfuric acid, H
2
SO
4
, to produce disulfuric acid or pyrosulfuric acid, also known as fuming sulfuric acid or oleum, H
2
S
2
O
7
.
SO
3
(g)+H
2
SO
4
→H
2
S
2
O
7
This is done because when water is added directly to sulfur trioxide to produce sulfuric acid
SO
3
(g)+H
2
O(l)→H
2
SO
4
(l)
the reaction is slow and tends to form a mist in which the particles refuse to coalesce.
5. Water is added to the disulfuric acid, H
2
S
2
O
7
, to produce sulfuric acid, H
2
SO
4
H
2
S
2
O
7
(l)+H
2
O(l)→H
2
SO
4
(l)