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decreases the current efficiency for the
hydrocoupling. On the other hand, Fe, Ni or Pb
is used for the anode, and these have lower
oxygen overpotentials to prevent the anodic
oxidation of organic compounds. The
supporting electrolyte is a mixture of
quaternary ammonium salts and inorganic salt.
Quaternary ammonium salts such as
ethyltributylammonium salt are effective not
only for increasing the selectivity of adiponitrile
formation but also for protection of the cathode
from corrosion. Inorganic salts such as
potassium phosphate and alkali metal borate
increase the conductivity of the electrolyte and
prevent corrosion of the anode.
The detailed operation conditions and
performances of this coupling process have
been reported by several workers [1-4] and an
example of operation conditions is as follows:
Cathode: Pb
Anode: Fe (Ni 9%)
Supporting electrolyte: (EtBu
3
N)
2
HPO
4
+
K
2
HPO
4
+ K
2
B
4
O
7
Current density: 2 kA m
−2
Temperature: 55 °C
Current efficiency: 90.7%
At the present time more than 300,000 tonnes
per year of adiponitrile is manufactured by
cathodic
hydrocoupling
of
acrylonitrile
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