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

Abstract

An electrochemical reduction device is provided with an electrode unit, a power control unit, an organic material storage tank, a water storage tank, a gas-liquid separator, and a control unit. The electrode unit has an electrolyte membrane, a reduction electrode, and an oxygen evolving electrode. The electrolyte membrane is formed of an ionomer. A reduction catalyst used for the reduction electrode contains at least one of Pt and Pd. The oxygen evolving electrode contains catalysts of noble metal oxides such as RuO 2 , IrO 2 , and the like. The control unit controls the power control unit such that a relationship, V HER −20 mV≦V CA ≦V TRR , can be satisfied when the potential at a reversible hydrogen electrode, the standard redox potential of an aromatic hydrocarbon compound or an N-containing heterocyclic aromatic compound, and the potential of the reduction electrode are expressed as V HER , V TRR , and V CA , respectively.

1 . An electrochemical reduction device comprising:
 an electrode unit 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 at least one benzene ring of an aromatic hydrocarbon compound or an N-containing heterocyclic aromatic compound, and an oxygen evolving electrode that is provided on the other side of the electrolyte membrane;   a power control unit that applies a voltage Va between the reduction electrode and the oxygen evolving electrode; and   a control unit that controls the power control unit such that a relationship, V HER −arbitrarily-defined acceptable potential≦V CA ≦V TRR , can be satisfied when the potential at a reversible hydrogen electrode, the standard redox potential of the aromatic hydrocarbon compound or an N-containing heterocyclic aromatic compound, and the potential of the reduction electrode are expressed as V HER , V TRR , and V CA , respectively.   
     
     
         2 . The electrochemical reduction device according to  claim 1 , wherein the arbitrarily-defined acceptable potential is 20 mV. 
     
     
         3 . The electrochemical reduction device according to  claim 1 , further comprising:
 a reference electrode that is arranged to be in contact with the electrolyte membrane and to be electrically isolated from the reduction electrode and the oxygen evolving electrode and that is held at a reference electrode potential V Ref ; and   a voltage detection unit that detects a potential difference ΔV CA  between the reference electrode and the reduction electrode,   wherein the control unit acquires the potential V CA  of the reduction electrode based on the potential difference ΔV CA  and the reference electrode potential V Ref .   
     
     
         4 . The electrochemical reduction device according to  claim 3 , wherein the control unit controls the potential V CA  of the reduction electrode to be in a predetermined range by changing the voltage Va. 
     
     
         5 . The electrochemical reduction device according to  claim 4 , wherein, when an oxygen evolution equilibrium potential in the electrolysis of water is expressed as V OER , the control unit controls the power control unit such that an expression, Va≧(V OER −V CA ), is satisfied. 
     
     
         6 . The electrochemical reduction device according to  claim 3 , wherein the reference electrode is arranged on the side of the electrolyte membrane on which the reduction electrode is provided. 
     
     
         7 . 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 at least one benzene ring of an aromatic hydrocarbon compound or an N-containing heterocyclic aromatic compound, and an oxygen evolving 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; and   a control unit that controls the power control unit such that a relationship, V HER −arbitrarily-defined acceptable potential≦V CA ≦V TRR , can be satisfied when the potential at a reversible hydrogen electrode, the standard redox potential of the aromatic hydrocarbon compound or the N-containing heterocyclic aromatic compound, and the potential of the reduction electrode of each electrode unit are expressed as V HER , V TRR , and V CA , respectively.   
     
     
         8 . The electrochemical reduction device according to  claim 7 , wherein the arbitrarily-defined acceptable potential is 20 mV. 
     
     
         9 . The electrochemical reduction device according to  claim 7 , further comprising:
 a reference electrode that is arranged to be in contact with an electrolyte membrane of any one of electrolytic layers contained in the electrode unit assembly and to be electrically isolated from the reduction electrode and the oxygen evolving electrode; and   a voltage detection unit that detects a potential difference ΔV CA  between the reference electrode and the reduction electrode,   wherein the control unit acquires the potential V CA  of the reduction electrode based on the potential difference ΔV CA  and the reference electrode potential V Ref .   
     
     
         10 . The electrochemical reduction device according to  claim 9 , wherein the control unit controls the potential V CA  of the reduction electrode of each electrode unit to be in a predetermined range by changing the voltage VA. 
     
     
         11 . The electrochemical reduction device according to  claim 10 , wherein, when an oxygen evolution equilibrium potential in the electrolysis of water is expressed as V OER , the control unit controls the power control unit such that an expression, VA≧(V OER −V CA )×N, is satisfied where N (two or greater) is the number of serially-concatenated electrode units. 
     
     
         12 . The electrochemical reduction device according to  claim 9 , wherein the reference electrode is arranged on the side of the electrolyte membrane on which the reduction electrode is provided. 
     
     
         13 . A method for manufacturing a hydride of an aromatic hydrocarbon compound or an N-containing heterocyclic aromatic compound, comprising introducing an aromatic hydrocarbon compound or an N-containing heterocyclic aromatic compound to the reduction electrode side of the electrode unit, circulating water or a humidified gas to the oxygen evolving electrode side, and hydrogenating at least one benzene ring of the aromatic hydrocarbon compound or the N-containing heterocyclic aromatic compound introduced to the reduction electrode side, by using the electrochemical reduction device according to  claim 1 . 
     
     
         14 . The method for manufacturing a hydride of an aromatic hydrocarbon compound or an N-containing heterocyclic aromatic compound according to  claim 13 , wherein the aromatic hydrocarbon compound or the N-containing heterocyclic aromatic compound to be introduced to the reduction electrode side is introduced to the reduction electrode side in a liquid state at a reaction temperature.