Electrochemical reduction device and method for manufacturing hydride of aromatic hydrocarbon compound or nitrogen-containing heterocyclic aromatic compound

An electrochemical reduction device comprising:

• an electrode unit assembly in which a plurality of electrode units are electrically connected to one another in series, the electrode units each including an electrolyte membrane having ionic conductivity, a reduction electrode that is provided on one side of the electrolyte membrane and that contains a reduction catalyst for hydrogenating a benzene ring of an aromatic hydrocarbon compound or a nitrogen-containing heterocyclic aromatic compound, and an oxygen generating electrode that is provided on the other side of the electrolyte membrane;
• a power control unit that applies a voltage VA between a positive electrode terminal and a negative electrode terminal of the electrode unit assembly so that in each electrode unit, the reduction electrode has a basic potential and the oxygen generating electrode has a noble potential;
• a hydrogen gas generation rate measurement unit that measures a generation rate F1′ per unit time of a hydrogen gas generated by an electrolytic reaction of water which competes with a benzene ring hydrogenation reaction of the aromatic hydrocarbon compound or the nitrogen-containing heterocyclic aromatic compound in the whole of the plurality of electrode units;
• and
• a control unit that controls the power control unit so as to gradually increase the voltage VA within a range that satisfies a relationship of F1′≦N×F0 and VCA>VHER−(acceptable potential difference), where the potential at a reversible hydrogen electrode, the potential of the reduction electrode, the acceptable upper limit of the hydrogen gas generation rate per electrode unit and the number of electrode units are expressed as VHER, VCA, F0 and N, respectively, and the acceptable potential difference is defined as a potential difference that defines an upper limit of a potential difference between VCA and VHER.