Biomedical Engineering Reference
In-Depth Information
Brine
Brine
H
H 2
Cl
Cl 2
-ve
-ve
+ ve
+ ve
H
H 2
Cl 2
Cl 2
+ +
+ +
+ +
+ +
+ +
+ +
+ +
+ +
+ +
+ +
+ +
+ +
+ +
+ +
--
- --
--
- --
--
--
- --
--
- --
--
NaCl
NaCl
OH -
OH -
H +
H +
Cl -
Cl -
Cl -
Cl -
Na +
Na +
OH -
OH -
H +
H +
NaCl
NaCl
Na +
Na +
Na +
Na +
Na +
Na +
H 2 O
H 2 O
+ H +
+ H +
-
-
Brine +
NaOH
Brine +
NaOH
FIGURE 3.6 Electrolysis of sodium chloride in water to produce Cl 2 and sodium hydroxide.
change in the reaction mixture is expected to be negligible or minimal, otherwise the stoi-
chiometry is intact. One example is the aqueous reaction:
C 6 H 12 O 6 ð
glucose
Þ /
C 6 H 6 O 3 ð
hydroxymethylfufural
Þþ3
H 2 O
(3.106)
that occurs in many bioprocesses. This reaction can be represented by
C
H
O
6 ð
glucose
Þ /
C
H
O
3 ð
hydroxymethylfufural
Þ
(3.107)
6
12
6
6
Since H 2 O is the solvent and in excess in the reaction mixture, generation of water amounts to
negligible change in the total amount of water in the reaction mixture.
In this section, we shall discuss another type of simplifications often used by bioprocess
engineers, in analogy to the coupled reactions used in electrochemical reactions. In some
occasions, we need to show only part of the (complete) reaction for ease of understanding.
For example, if we want to show how glucose (a renewable substrate) can be converted
butene (intermediate for polymers, jet fuels, etc.):
C
H
O
6 þ
H
2 /
C
H
8 þ
HCOOH
þ
CO
2 þ 2
H
O
(3.108)
6
12
4
2
This overall reaction does not mean much except seeing that stoichiometrically it is possible.
This reaction is usually achieved in four steps:
C
H
O
6 /
C
H
O
3 þ 3
H
O
(3.109)
6
12
6
6
2
C
H
O
3 ð
hydroxymethylfufural
Þþ2
H
O
/
C
H
O
3 ð
levulinic acid
Þ
6
6
2
5
8
þ
HCOOH
ð
formic acid
Þ
(3.110)
O
C
H 2 C
O
+ H 2 O
C 5 H 8 O 3 + H 2
(3.111)
H 2 C
CH
CH 3
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