Electrochemical reduction of carbon dioxide

Abstract

Disclosed herein is a method for selectively reducing, using electrical energy, CO 2 to carbon monoxide or formic acid, a catalyst for use in the method, and an electrochemical reduction system. The method for producing carbon monoxide or formic acid by electrochemically reducing carbon dioxide of the present invention includes (a) reacting carbon dioxide with a metal complex represented by formula (1), and (b) applying a voltage to a reaction product of the carbon dioxide and the metal complex represented by formula (1):

1 : A method for producing carbon monoxide by electrochemically reducing carbon dioxide, the method comprising:
 (a) reacting carbon dioxide with a metal complex represented by formula (1):   
       
         
           
           
               
               
           
         
         wherein 
         X represents OR 1 , SR 1 , NR 2 R 3 R 4  or PX 1 X 2 X 3 , 
         Y represents CO, OR 1 , SR 1 , NR 2 R 3 R 4  or PX 1 X 2 X 3 , 
         ring A and ring B are identical or different and represent a nitrogen atom-containing heterocycle optionally having a substituent, 
         R 1  represents a hydrocarbon group optionally having a substituent, 
         one, two or three of R 2 , R 3  and R 4  are identical or different and represent a hydrocarbon group optionally having a substituent, the rest representing a hydrogen atom, and 
         one, two or three of X 1 , X 2  and X 3  are identical or different and represent a hydrocarbon group optionally having a substituent or a hydrocarbon oxy group optionally having a substituent, the rest representing a hydrogen atom or a hydroxy group; and 
         (b) applying a voltage to a reaction product of the carbon dioxide and the metal complex represented by formula (1). 
       
     
     
         2 : The production method according to  claim 1 , wherein the steps (a) and (b) are performed within an electrochemical cell including a working electrode and a counter electrode, and the method comprises:
 (a1) introducing carbon dioxide into a solution comprising the metal complex held in the electrochemical cell; and   (b1) applying a negative voltage and a positive voltage respectively to the working electrode and the counter electrode of the electrochemical cell.   
     
     
         3 : The production method according to  claim 2 , wherein the carbon dioxide is introduced by introducing a carbon dioxide-containing gas into the solution containing the metal complex. 
     
     
         4 : The production method according to  claim 1 , wherein the carbon dioxide to be reacted is a gas containing 0.03 to 100% of carbon dioxide. 
     
     
         5 : The production method according to  claim 1 , wherein the nitrogen atom-containing heterocycle is a heterocycle having a 2,2′-bipyridine structure optionally having a substituent. 
     
     
         6 : The production method according to  claim 1 , wherein each hydrocarbon group optionally having a substituent represented by R 1 , R 2 , R 3 , R 4 , X 1 , X 2  and X 3  is one selected from the group consisting of an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group and an aromatic hydrocarbon group, each of which optionally has one to three substituents selected from the group consisting of a primary, secondary or tertiary amino group, a hydroxy group, as alkoxy group, as aryloxy group, a halogen atom, a nitro group, a cyano group, a formyl group, an alkanoyl group and an arylcarbonyl group. 
     
     
         7 : A method for producing carbon monoxide from carbon dioxide, wherein the carbon monoxide obtained by the production method according to  claim 1  is used as a reducing agent. 
     
     
         8 : A method for producing a hydrocarbon-based compound, wherein the carbon monoxide obtained by the production method according to  claim 1  is used as a raw material. 
     
     
         9 : A catalyst for electrochemically reducing carbon dioxide to carbon monoxide, the catalyst represented by formula (1): 
       
         
           
           
               
               
           
         
         wherein 
         X represents OR 1 , SR 1 , NR 2 R 3 R 4  or PX 1 X 2 X 3 , 
         Y represents CO, OR 1 , SR 1 , NR 2 R 3 R 4  or PX 1 X 2 X 3 , 
         ring A and ring B are identical or different and represent a nitrogen atom-containing heterocycle optionally having a substituent, 
         R 1  represents a hydrocarbon group optionally having a substituent, 
         one, two or three of R 2 , R 3  and R 4  are identical or different and represent a hydrocarbon group optionally having a substituent, the rest representing a hydrogen atom, and 
         one, two or three of X 1 , X 2  and X 3  are identical or different and represent a hydrocarbon group optionally having a substituent or a hydrocarbon oxy group optionally having a substituent, the rest representing a hydrogen atom or a hydroxy group. 
       
     
     
         10 : The catalyst according to  claim 9 , wherein the nitrogen atom-containing heterocycle is a heterocycle having a 2,2′-bipyridine structure optionally having a substituent. 
     
     
         11 : The catalyst according to  claim 9 , wherein each hydrocarbon group optionally having a substituent represented by R 1 , R 2 , R 3 , R 4 , X 1 , X 2  and X 3  is one selected from the group consisting of an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group and an aromatic hydrocarbon group, each of which optionally has one to three substituents selected from the group consisting of a primary, secondary or tertiary amino group, a hydroxy group, as alkoxy group, as aryloxy group, a halogen atom, a nitro group, a cyano group, a formyl group, an alkanoyl group and an arylcarbonyl group. 
     
     
         12 : A method for producing formic acid by electrochemically reducing carbon dioxide, the method comprising:
 (a) reacting carbon dioxide with a metal complex represented by formula (2):   
       
         
           
           
               
               
           
         
         wherein 
         M 1  represents manganese, ruthenium or iron, 
         X represents OR 1 , SR 1 , NR 2 R 3 R 4  or PX 1 X 2 X 3 , 
         Y represents CO, OR 1 , SR 1 , NR 2 R 3 R 4  or PX 1 X 2 X 3 , 
         ring A and ring B are identical or different and represent a nitrogen-containing heterocycle optionally having a substituent, 
         R 1  represents a hydrocarbon group optionally having a substituent, 
         one, two or three of R 2 , R 3  and R 4  are identical or different and represent a hydrocarbon group optionally having a substituent, the rest representing a hydrogen atom, and 
         one, two or three of X 1 , X 2  and X 3  are identical or different and represent a hydrocarbon group optionally having a substituent or a hydrocarbon oxy group optionally having a substituent, the rest representing a hydrogen atom or a hydroxy group; and 
         (b) applying a voltage to a reaction product of the carbon dioxide and the metal complex represented by formula (2). 
       
     
     
         13 : The production method according to  claim 12 , wherein the steps (a) and (b) are performed within an electrochemical cell including a working electrode and a counter electrode, and the method comprises:
 (a1) introducing carbon dioxide into a solution containing the metal complex held in the electrochemical cell; and   (b1) applying a negative voltage and a positive voltage respectively to the working electrode and the counter electrode of the electrochemical cell.   
     
     
         14 : The production method according to  claim 13 , wherein the carbon dioxide is introduced by introducing a carbon dioxide-containing gas into the solution containing the metal complex. 
     
     
         15 : The production method according to  claim 12 , wherein the carbon dioxide to be reacted is a gas containing 0.03 to 100% of carbon dioxide. 
     
     
         16 : The production method according to  claim 12 , wherein the nitrogen atom-containing heterocycle is a heterocycle having a 2,2′-bipyridine structure optionally having a substituent. 
     
     
         17 : The production method according to  claim 12 , wherein each hydrocarbon group optionally having a substituent represented by R 1 , R 2 , R 3 , R 4 , X 1 , X 2  and X 3  is one selected from the group consisting of an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group and an aromatic hydrocarbon group, each of which optionally has one to three substituents selected from the group consisting of a primary, secondary or tertiary amino group, a hydroxy group, an alkoxy group, an aryloxy group, a halogen atom, a nitro group, a cyano group, a formyl group, an alkanoyl group and an arylcarbonyl group. 
     
     
         18  : A catalyst for electrochemically reducing carbon dioxide to formic acid, the catalyst represented by formula (2): 
       
         
           
           
               
               
           
         
         wherein 
         M 1  represents manganese, ruthenium or iron, 
         X represents OR 1 , SR 1 , NR 2 R 3 R 4  or PX 1 X 2 X 3 , 
         Y represents CO, OR 1 , SR 1 , NR 2 R 3 R 4  or PX 1 X 2 X 3 , 
         ring A and ring B are identical or different and represent a nitrogen atom-containing heterocycle optionally having a substituent, 
         R 1  represents a hydrocarbon group optionally having a substituent; 
         one, two or three of R 2 , R 3  and R 4  are identical or different and represent a hydrocarbon group optionally having a substituent, the rest representing a hydrogen atom, and 
         one, two or three of X 1 , X 2  and X 3  are identical or different and represent a hydrocarbon group optionally having a substituent or a hydrocarbon oxy group optionally having a substituent, the rest representing a hydrogen atom or a hydroxy group. 
       
     
     
         19 : The catalyst according to  claim 18 , wherein the nitrogen atom-containing heterocycle is a heterocycle having a 2,2′-bipyridine structure optionally having a substituent. 
     
     
         20 : The catalyst according to  claim 18 , wherein each hydrocarbon group optionally having a substituent represented by R 1 , R 2 , R 3 , R 4 , X 1 , X 2  and X 3  is one selected from the group consisting of an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group and an aromatic hydrocarbon group, each of which optionally has one to three substituents selected from the group consisting of a primary, secondary or tertiary amino group, a hydroxy group, an alkoxy group, an aryloxy group, a halogen atom, a nitro group, a cyano group, a formyl group, an alkanoyl group and an arylcarbonyl group. 
     
     
         21 : A metal complex represented by formula (2a): 
       
         
           
           
               
               
           
         
         wherein 
         M 1  represents manganese, ruthenium or iron, 
         X represents O(CH 2 ) n NR 5 R 6 , NR 5 R 6  or PX 1 X 2 X 3 , 
         Y represents CO, C(CH 2 ) n NR 5 R 6 , NR 5 R 6  or PX 1 X 2 X 3 , 
         ring A and ring B are identical or different and represent a nitrogen atom-containing heterocycle optionally having a substituent, 
         one, two or three of X 1 , X 2  and X 3  are identical or different and represent a hydrocarbon group optionally having a substituent or a hydrocarbon oxy group optionally having a substituent, the rest representing a hydrogen atom or a hydroxy group, 
         R 5  and R 6  are identical or different and represent an alkyl group, a hydroxyalkyl group or a hydrogen atom, and 
         n represents a number of 2 to 8. 
       
     
     
         22 : The metal complex according to  claim 21 , wherein the nitrogen atom-containing heterocycle is a heterocycle having a 2,2′-bipyridine structure optionally having a substituent. 
     
     
         23 : The metal complex according to  claim 21 , wherein each hydrocarbon group optionally having a substituent represented by X 1 , X 2  and X 3  is one selected from the group consisting of an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group and an aromatic hydrocarbon group, each of which optionally has one to three substituents selected from the group consisting of a primary, secondary or tertiary amino group, a hydroxy group, an alkoxy group, an aryloxy group, a halogen atom, a nitro group, a cyano group, a formyl group, an alkanoyl group and an arylcarbonyl group. 
     
     
         24 : A carbon monoxide production system for producing carbon monoxide by electrochemically reducing carbon dioxide, the system comprising:
 an electrochemical cell part equipped with a solution containing a metal complex, a working electrode and a counter electrode;   an injection part through which carbon dioxide is injected into the solution containing the metal complex held in the electrochemical cell part;   a voltage source capable of applying a positive or negative voltage between the working electrode and the counter electrode of the electrochemical cell part; and   a discharge part discharging carbon monoxide generated within the solution containing the metal complex,   wherein the carbon monoxide is generated by applying a positive or negative voltage to a reaction product of the metal complex generated by the solution containing the metal complex and the carbon dioxide.   
     
     
         25 : The carbon monoxide production system according to  claim 24 , wherein:
 the metal complex is represented by formula (1):   
       
         
           
           
               
               
           
         
         X represents OR 1 , SR 1 , NR 2 R 3 R 4  or PX 1 X 2 X 3 , 
         Y represents CO, OR 1 , SR 1 , NR 2 R 3 R 4  or PX 1 X 2 X 3 , 
         ring A and ring B are identical or different and represent a nitrogen atom-containing heterocycle optionally having a substituent, 
         R 1  represents a hydrocarbon group optionally having a substituent, 
         one, two or three of R 2 , R 3  and R 4  are identical or different and represent a hydrocarbon group optionally having a substituent, the rest representing a hydrogen atom, and 
         one, two or three of X 1 , X 2  and X 3  are identical or different and represent a hydrocarbon group optionally having a substituent or a hydrocarbon oxy group optionally having a substituent, the rest representing a hydrogen atom or a hydroxy group. 
       
     
     
         26 : The carbon monoxide production system according to  claim 24 , wherein the carbon dioxide is fed without concentration in a feed part feeding the carbon dioxide. 
     
     
         27 : The carbon monoxide production system according to  claim 24 , further comprising:
 a carbon monoxide detection part detecting a concentration of the carbon monoxide discharged from the solution containing the metal complex.   
     
     
         28 : The carbon monoxide production system according to  claim 27 , wherein the carbon monoxide detection part is a gas chromatography. 
     
     
         29 : The carbon monoxide production system according to  claim 24 , wherein the nitrogen atom-containing heterocycle is a heterocycle having a 2,2′-bipyridine structure optionally having a substituent. 
     
     
         30 : The carbon monoxide production system according to  claim 24 , wherein each hydrocarbon group optionally having a substituent represented by R 1 , R 2 , R 3 , R 4 , X 1 , X 2  and X 3  is one selected from the group consisting of an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group and an aromatic hydrocarbon group, each of which optionally has one to three substituents selected from the group consisting of a primary, secondary or tertiary amino group, a hydroxy group, an alkoxy group, an aryloxy group, a halogen atom, a nitro group, a cyano group, a formyl group, an alkanoyl group and an arylcarbonyl group.