Chemistry Reference
In-Depth Information
CHAPTER 2
Inorganic Chemicals
2.1 SULFURIC ACID
Sulfuric acid (H
2
SO
4
) is a large volume chemical made from sulfur dioxide,
which in turn can be made from elemental sulfur. Because sulfuric acid is
of prime importance to the world's fertilizer and manufacturing industries,
consumption of sulfuric acid has been regarded as one of the indexes of a
nation's industrial development [1]. Sulfuric acid is the largest volume chem-
ical produced in the world. Sulfur is oxidized to sulfur dioxide. Sulfur dioxide
is then further oxidized to sulfur trioxide. Temperatures of 400
∘
C to 450
∘
C
are typical and a vanadium catalyst such as vanadium pentoxide (V
2
O
5
)is
commonly used [2, 3]. At a lower temperature, sulfur trioxide combines with
water to form sulfuric acid. The following reactions give a synopsis of the
chemistry.
S + O
2
SO
2
2 SO
2
+ 2 V
2
O
5
2 SO
3
+ 2 V
2
O
4
O
2
+ 2 V
2
O
4
V
2
O
5
H
2
SO
4
SO
3
+ H
2
O
There are several sources of sulfur. Elemental sulfur is naturally occurring
and can be mined by a process invented in the late 19
th
century by Herman
Frasch. The Frasch process takes advantage of the relatively low melting point
of sulfur at 115
∘
C. Superheated water at 168
∘
C is pumped through pipes
inserted into a well and molten sulfur is pumped from the well [4].
Another source is pyrite. Pyrite is iron sulfide (FeS
2
). Pyrite is also known
as fool's gold because of its visual resemblance to the precious metal. With
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