Electrochemical reduction of carbon dioxide

文档序号：1211577 发布日期：2020-09-04 浏览：6次中文

阅读说明：本技术 二氧化碳的电化学还原 (Electrochemical reduction of carbon dioxide ) 是由石谷治于 2016-02-05 设计创作，主要内容包括：本发明提供利用电能由CO2选择性地还原为一氧化碳或甲酸的方法、其中使用的催化剂和电化学还原系统。一种从二氧化碳到一氧化碳或甲酸的基于电化学还原的制造方法,其特征在于,具有以下的工序(a)和(b)。工序(a)：使二氧化碳与通式(1)(式中,M表示铼、锰、钌或铁,X表示OR1、SR1、NR2R3R4或PX1X2X3,Y表示CO、OR1、SR1、NR2R3R4或PX1X2X3,A环和B环相同或不同,表示具有或不具有取代基的含氮原子杂环,R1表示具有或不具有取代基的烃基,R2、R3和R4中的1～3个相同或不同,表示具有或不具有取代基的烃基,剩余部分表示氢原子,X1、X2和X3中的1～3个相同或不同,表示具有或不具有取代基的烃基或具有或不具有取代基的烃氧基,剩余部分表示氢原子或羟基)表示的金属配合物反应,工序(b)：对二氧化碳和通式(1)表示的金属配合物的反应物外加电压。<Image he="428" wi="560" file="DDA0002487809520000011.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>(The invention provides a method for utilizing electric energy to generate CO 2 A method for selective reduction to carbon monoxide or formic acid, a catalyst for use therein and an electrochemical reduction system. A method for producing carbon dioxide, carbon monoxide or formic acid by electrochemical reduction, comprising the following steps (a) and (b). A step (a): reacting carbon dioxide with a compound of the general formula (1) (wherein M represents rhenium, manganese, ruthenium OR iron, and X represents OR 1 、SR 1 、NR 2 R 3 R 4 Or PX 1 X 2 X 3 Y represents CO OR OR 1 、SR 1 、NR 2 R 3 R 4 Or PX 1 X 2 X 3 The ring A and the ring B, which may be the same or different, represent a nitrogen atom-containing heterocycle with or without a substituent, and R 1 Represents a hydrocarbon group with or without a substituent, R 2 、R 3 And R 4 1 to 3 of them are the same or different and represent a hydrocarbon group with or without a substituent, the remainder represents a hydrogen atom, X 1 、X 2 And X 3 1 to 3 of which are the same or different and each represent a substituted or unsubstituted hydrocarbon group or a substituted or unsubstituted hydrocarbonoxy group, and the remainder represents a hydrogen atom or a hydroxyl group), and a step (b): a voltage is applied to a reactant of carbon dioxide and a metal complex represented by the general formula (1).)

1. A method for producing formic acid from carbon dioxide by electrochemical reduction, comprising the following steps (a) and (b):

a step (a): reacting carbon dioxide with a metal complex represented by the general formula (2),

in the formula, M₁Represents manganese, ruthenium or iron,

x represents OR¹、SR¹、NR²R³R⁴Or PX¹X²X³，

Y represents CO OR OR¹、SR¹、NR²R³R⁴Or PX¹X²X³，

The ring A and the ring B, which may be the same or different, represent a nitrogen atom-containing heterocycle having a substituent or not,

R¹represents a hydrocarbon group with or without a substituent,

R²、R³and R⁴1 to 3 of them are the same or different and each represents a hydrocarbon group having or not having a substituent, and the remainder represents a hydrogen atom,

X¹、X²and X³1 to 3 of them are the same or different and represent a substituted or unsubstituted hydrocarbon group or a substituted or unsubstituted hydrocarbon oxy group, the remainder representing a hydrogen atom or a hydroxyl group;

a step (b): a voltage is applied to a reactant of carbon dioxide and a metal complex represented by the general formula (2).

2. The manufacturing method according to claim 1, wherein the manufacturing method is a method of performing the steps (a) and (b) in an electrochemical cell having a working electrode and a counter electrode, and comprises the steps (a1) and (b 1):

step (a 1): introducing carbon dioxide into a solution containing the metal complex in an electrochemical cell,

step (b 1): a negative voltage and a positive voltage are applied to the working electrode and the counter electrode of the electrochemical cell, respectively.

3. The production method according to claim 2, wherein the introduction of carbon dioxide is introducing a gas containing carbon dioxide into the solution containing the metal complex.

4. The production process according to any one of claims 1 to 3, wherein the carbon dioxide used in the reaction is a gas containing 0.03 to 100% of carbon dioxide.

5. The production method according to any one of claims 1 to 3, wherein the nitrogen atom-containing heterocyclic ring containing the ring A and the ring B is a heterocyclic ring having a 2, 2' -bipyridine structure with or without a substituent.

6. The production method according to any one of claims 1 to 3, wherein R is represented by¹、R²、R³、R⁴、X¹、X²And X³The substituted or unsubstituted hydrocarbon group is an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group or an aromatic hydrocarbon group, wherein the group may have 1 to 3 substituents selected from the group consisting of a primary amino group, a secondary or tertiary amino group, a hydroxyl 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.

7. A catalyst for electrochemical reduction of carbon dioxide to formic acid represented by the general formula (2),

in the formula, M₁Represents manganese, ruthenium or iron,

x represents OR¹、SR¹、NR²R³R⁴Or PX¹X²X³，

Y represents CO OR OR¹、SR¹、NR²R³R⁴Or PX¹X²X³，

The ring A and the ring B, which may be the same or different, represent a nitrogen atom-containing heterocycle having a substituent or not,

R¹represents a hydrocarbon group with or without a substituent,

R²、R³and R⁴1 to 3 of them are the same or different and each represents a hydrocarbon group having or not having a substituent, and the remainder represents a hydrogen atom,

X¹、X²and X³1 to 3 of the above-mentioned groups are the same or different and each represents a substituted or unsubstituted hydrocarbon group or a substituted or unsubstituted hydrocarbon oxy group, and the remainder isRepresents a hydrogen atom or a hydroxyl group.

8. The catalyst according to claim 7, wherein the nitrogen atom-containing heterocyclic ring containing ring A and ring B is a heterocyclic ring having a 2, 2' -bipyridine structure with or without a substituent.

9. The catalyst of claim 7 or 8, wherein R is represented by¹、R²、R³、R⁴、X¹、X²And X³The substituted or unsubstituted hydrocarbon group is an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group or an aromatic hydrocarbon group, wherein the group may have 1 to 3 substituents selected from the group consisting of a primary amino group, a secondary or tertiary amino group, a hydroxyl 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.

10. A metal complex represented by the general formula (2a),

in the formula, M₁Represents manganese, ruthenium or iron,

x represents O (CH)₂)_nNR⁵R⁶、NR⁵R⁶Or PX¹X²X³，

Y represents CO or C (CH)₂)_nNR⁵R⁶、NR⁵R⁶Or PX¹X²X³，

The ring A and the ring B, which may be the same or different, represent a nitrogen atom-containing heterocycle having a substituent or not,

X¹、X²and X³1 to 3 of them are the same or different and each represents a substituted or unsubstituted hydrocarbon group or a substituted or unsubstituted hydrocarbon oxy group, and the remainder represents a hydrogen atom or a hydroxyl group,

R⁵and R⁶The same or different, represent alkyl, hydroxyalkylOr a hydrogen atom,

n represents a number of 2 to 8.

11. The metal complex according to claim 10, wherein the nitrogen atom-containing heterocyclic ring containing ring a and ring B is a heterocyclic ring having a 2, 2' -bipyridine structure with or without a substituent.

12. The metal complex according to claim 10 or 11, wherein X is selected from the group consisting of¹、X²And X³The substituted or unsubstituted hydrocarbon group is an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group or an aromatic hydrocarbon group, wherein the group may have 1 to 3 substituents selected from the group consisting of a primary amino group, a secondary or tertiary amino group, a hydroxyl 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.

Technical Field

The present invention relates to a process for the electrochemical reduction of carbon dioxide to carbon monoxide or formic acid and to a catalyst for use therein.

Background

At present, human beings have such serious problems as global warming and exhaustion of carbon resources. As a solution to this, attention is being paid to a catalyst for converting light energy into chemical energy. If endless solar energy could be used to convert carbon dioxide (CO)₂) Conversion into useful compounds is expected to solve these problems at once. However, CO₂Is the final oxidation state of the carbon compound and is therefore very stable both physically and chemically, with very low reactivity.

In recent years, some reports have made this CO₂Techniques for reductive conversion to useful compounds. For examplePatent document 1 describes that CO is caused to exist in the presence of a catalyst₂Patent document 2 describes a method for obtaining formic acid by reaction with hydrogen, and describes CO-pairing in which excited electrons generated by irradiation of a semiconductor electrode with light are transferred to a catalyst₂A method for obtaining formic acid by reduction. Patent document 3 and non-patent document 1 report that CO is used₂Contacting rhenium complex and irradiating the same with light to convert CO₂Reduction to carbon monoxide. In addition, CO is also introduced₂An attempt has been made to perform electrochemical reduction in the presence of a metal complex catalyst (patent document 4).

Disclosure of Invention

However, the methods of patent documents 1 and 2 require hydrogen, a semiconductor, and light irradiation for reduction, and the methods of patent document 1 require hydrogen for reduction, which is not considered to be advantageous in terms of energy. In addition, in patent document 3 or non-patent document 1, another catalyst such as a ruthenium complex is required for the photocatalytic reaction in addition to the catalyst for reduction. In addition, in patent document 4, CO is treated₂Electrochemical treatment is performed, and as a result, it is not clear what is generated.

On the other hand, if CO can be reduced₂And carbon monoxide (CO) or formic acid is selectively obtained, the carbon monoxide obtained therein becomes an extremely wide variety of hydrocarbon feedstocks. Hydrocarbons are the same chemical energy feedstocks as petroleum. Further, since hydrogen can be easily generated by reacting formic acid with a catalyst, it is expected as a liquid fuel for storing hydrogen.

Accordingly, an object of the present invention is to provide a method for generating CO from electric energy₂A method for selective reduction to carbon monoxide or formic acid, a catalyst for use therein and an electrochemical reduction system.

Therefore, the inventors have sought to electrochemically convert CO₂Various studies have been conducted on reduction of carbon monoxide or formic acid, and as a result, it has been found that if CO is allowed to react₂By reacting with a metal complex represented by the general formula (1) or the general formula (2) and applying a voltage to the reactant, CO can be converted₂Selectively and easily reduced to carbon monoxide or formic acid, and it was also found that even the introduced CO was present₂The concentration is low, and the reduction reaction proceeds, thereby completing the present invention.

That is, the present invention provides the following [ 1] to [ 30 ].

[ 1] A method for producing carbon dioxide to carbon monoxide by electrochemical reduction, comprising the following steps (a) and (b):

a step (a): reacting carbon dioxide with a metal complex represented by the general formula (1),

(wherein X represents OR¹、SR¹、NR²R³R⁴Or PX¹X²X³，

Y represents CO OR OR¹、SR¹、NR²R³R⁴Or PX¹X²X³，

The ring A and the ring B, which may be the same or different, represent a nitrogen atom-containing heterocycle having a substituent or not,

R¹represents a hydrocarbon group with or without a substituent,

R²、R³and R ⁴1 to 3 of them are the same or different and each represents a hydrocarbon group having or not having a substituent, and the remainder represents a hydrogen atom,

X¹、X²and X ³1 to 3 of the above-mentioned (C)The same or different, represents a hydrocarbon group with or without a substituent or a hydrocarbyloxy group with or without a substituent, and the remainder represents a hydrogen atom or a hydroxyl group. )

A step (b): a voltage is applied to a reactant of carbon dioxide and a metal complex represented by the general formula (1).

The production method according to [ 1], which is a method for performing the steps (a) and (b) in an electrochemical cell having a working electrode and a counter electrode, comprising the steps (a1) and (b 1):

step (a 1): introducing carbon dioxide into a solution containing the metal complex in an electrochemical cell,

step (b 1): a negative voltage and a positive voltage are applied to the working electrode and the counter electrode of the electrochemical cell, respectively.

The production method according to [ 3 ] above, wherein the introduction of carbon dioxide introduces a carbon dioxide-containing gas into the solution containing the metal complex.

The production method according to any one of [ 1] to [ 3 ], wherein the carbon dioxide used in the reaction is a gas containing 0.03 to 100% of carbon dioxide.

The production method according to any one of [ 1] to [4 ], wherein the nitrogen-atom-containing heterocyclic ring containing the A ring and the B ring is a heterocyclic ring having a 2, 2' -bipyridine structure with or without a substituent.

[ 6 ] the production method according to any one of [ 1] to [ 5 ], wherein R is¹、R²、R³、R⁴、X¹、X²And X³The substituted or unsubstituted hydrocarbon group is an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group or an aromatic hydrocarbon group (these groups may have 1 to 3 substituents selected from the group consisting of a primary amino group, a secondary or tertiary amino group, a hydroxyl 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).

A process for producing carbon monoxide from carbon dioxide, characterized by using carbon monoxide obtained by the process according to any one of [ 1] to [ 6 ] as a reducing agent.

A process for producing a hydrocarbon compound, which comprises using, as a raw material, carbon monoxide obtained by the process according to any one of [ 1] to [ 6 ].

[ 9 ] A catalyst for electrochemical reduction of carbon dioxide to carbon monoxide represented by the general formula (1),

(wherein X represents OR¹、SR¹、NR²R³R⁴Or PX¹X²X³，

Y represents CO OR OR¹、SR¹、NR²R³R⁴Or PX¹X²X³，

The ring A and the ring B, which may be the same or different, represent a nitrogen atom-containing heterocycle having a substituent or not,

R¹represents a hydrocarbon group with or without a substituent,

R²、R³and R ⁴1 to 3 of them are the same or different and each represents a hydrocarbon group having or not having a substituent, and the remainder represents a hydrogen atom,

X¹、X²and X ³1 to 3 of them are the same or different and represent a substituted or unsubstituted hydrocarbon group or a substituted or unsubstituted hydrocarbon oxy group, and the remainder represents a hydrogen atom or a hydroxyl group. )

[ 10 ] the catalyst according to [ 9 ], wherein the nitrogen atom-containing heterocyclic ring containing the A ring and the B ring is a heterocyclic ring having a 2, 2' -bipyridyl structure with or without a substituent.

[ 11 ] the catalyst according to [ 9 ] or [ 10 ], wherein R is substituted with a group represented by formula¹、R²、R³、R⁴、X¹、X²And X³The optionally substituted hydrocarbon group is an alkyl, alkenyl, cycloalkyl, cycloalkenyl or aromatic hydrocarbon group (these groups may or may not have a primary amino group)1 to 3 substituents selected from the group consisting of a secondary or tertiary amino group, a hydroxyl 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).

[ 12 ] A method for producing formic acid from carbon dioxide by electrochemical reduction, which comprises the following steps (a) and (b),

a step (a): reacting carbon dioxide with a metal complex represented by the general formula (2),

(in the formula, M₁Represents manganese, ruthenium or iron,

x represents OR¹、SR¹、NR²R³R⁴Or PX¹X²X³，

Y represents CO OR OR¹、SR¹、NR²R³R⁴Or PX¹X²X³，

The ring A and the ring B, which may be the same or different, represent a nitrogen atom-containing heterocycle having a substituent or not,

R¹represents a hydrocarbon group with or without a substituent,

R²、R³and R ⁴1 to 3 of them are the same or different and each represents a hydrocarbon group having or not having a substituent, and the remainder represents a hydrogen atom,

A step (b): a voltage is applied to a reactant of carbon dioxide and a metal complex represented by the general formula (2).

The production method according to [ 12 ], which is a method for performing the steps (a) and (b) in an electrochemical cell having a working electrode and a counter electrode, comprising the steps (a1) and (b 1):

step (a 1): introducing carbon dioxide into a solution containing the metal complex in an electrochemical cell,

step (b 1): a negative voltage and a positive voltage are applied to the working electrode and the counter electrode of the electrochemical cell, respectively.

The production method according to [ 13 ] above, wherein the introduction of carbon dioxide introduces a carbon dioxide-containing gas into the solution containing the metal complex.

The production method according to any one of [ 12 ] to [ 15 ], wherein the carbon dioxide used in the reaction is a gas containing 0.03 to 100% of carbon dioxide.

The production method according to any one of [ 12 ] to [ 15 ], wherein the nitrogen-atom-containing heterocyclic ring containing the A ring and the B ring is a heterocyclic ring having a 2, 2' -bipyridine structure with or without a substituent.

The production method according to any one of [ 12 ] to [ 16 ], wherein R is¹、R²、R³、R⁴、X¹、X²And X³The substituted or unsubstituted hydrocarbon group is an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group or an aromatic hydrocarbon group (these groups may have 1 to 3 substituents selected from the group consisting of a primary amino group, a secondary or tertiary amino group, a hydroxyl 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 electrochemical reduction of carbon dioxide to formic acid represented by the general formula (2),

(in the formula, M₁Represents manganese, ruthenium or iron,

x represents OR¹、SR¹、NR²R³R⁴Or PX¹X²X³，

Y represents CO OR OR¹、SR¹、NR²R³R⁴Or PX¹X²X³，

The ring A and the ring B, which may be the same or different, represent a nitrogen atom-containing heterocycle having a substituent or not,

R¹represents a hydrocarbon group with or without a substituent,

R²、R³and R ⁴1 to 3 of them are the same or different and each represents a hydrocarbon group having or not having a substituent, and the remainder represents a hydrogen atom,

[ 19 ] the catalyst according to [ 18 ], wherein the nitrogen atom-containing heterocyclic ring having the A ring and the B ring is a heterocyclic ring having a 2, 2' -bipyridyl structure which may have a substituent.

[ 20 ] the catalyst according to [ 18 ] or [ 19 ], wherein R is substituted with a group represented by formula¹、R²、R³、R⁴、X¹、X²And X³The substituted or unsubstituted hydrocarbon group is an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group or an aromatic hydrocarbon group (these groups may have 1 to 3 substituents selected from the group consisting of a primary amino group, a secondary or tertiary amino group, a hydroxyl 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 the general formula (2a),

(in the formula, M₁Represents manganese, ruthenium or iron,

x represents O (CH)₂)_nNR⁵R⁶、NR⁵R⁶Or PX¹X²X³，

Y represents CO or C (CH)₂)_nNR⁵R⁶、NR⁵R⁶Or PX¹X²X³，

The ring A and the ring B, which may be the same or different, represent a nitrogen atom-containing heterocycle having a substituent or not,

X¹、X²and X ³1 to 3 of them are the same or different and each represents a substituted or unsubstituted hydrocarbon group or a substituted or unsubstituted hydrocarbon oxy group, and the remainder represents a hydrogen atom or a hydroxyl group,

R⁵and R⁶Identical or different, represents an alkyl group, a hydroxyalkyl group or a hydrogen atom,

n represents a number of 2 to 8).

[ 22 ] the metal complex according to [ 21 ], wherein the nitrogen atom-containing heterocycle having the A ring and the B ring is a heterocycle having a 2, 2' -bipyridine structure with or without a substituent.

[ 23 ] the metal complex according to [ 21 ] or [ 22 ], wherein X is substituted¹、X²And X³The substituted or unsubstituted hydrocarbon group is an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group or an aromatic hydrocarbon group (these groups may have 1 to 3 substituents selected from the group consisting of a primary amino group, a secondary or tertiary amino group, a hydroxyl 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 from carbon dioxide by electrochemical reduction, comprising:

an electrochemical cell unit comprising a solution containing a metal complex, a working electrode and a counter electrode,

an injection part for injecting carbon dioxide into the solution containing the metal complex in the electrochemical cell part,

a voltage source capable of applying a positive or negative voltage between the working electrode and the counter electrode in the electrochemical cell unit, and

a discharge unit for discharging carbon monoxide generated in the solution containing the metal complex,

carbon monoxide is produced by applying a positive or negative voltage to the above-mentioned metal complex reactant produced from a solution containing the above-mentioned metal complex and carbon dioxide.

[ 25 ] the carbon monoxide production system according to [ 24 ], wherein the metal complex is a metal complex represented by the general formula (1),

(wherein X represents OR¹、SR¹、NR²R³R⁴Or PX¹X²X³，

Y represents CO OR OR¹、SR¹、NR²R³R⁴Or PX¹X²X³，

The ring A and the ring B, which may be the same or different, represent a nitrogen atom-containing heterocycle having a substituent or not,

R¹represents a hydrocarbon group with or without a substituent,

R²、R³and R ⁴1 to 3 of them are the same or different and each represents a hydrocarbon group having or not having a substituent, and the remainder represents a hydrogen atom,

[ 26 ] the carbon monoxide production system according to [ 24 ] or [ 25 ], wherein the carbon dioxide is sent without being concentrated at a sending part that sends the carbon dioxide.

The carbon monoxide production system according to any one of [ 24 ] to [ 26 ], further comprising a carbon monoxide detection unit that detects a concentration of carbon monoxide discharged from the solution containing the metal complex.

The carbon monoxide production system according to [ 27 ], wherein the carbon monoxide detecting unit is a gas chromatograph.

The carbon monoxide production system according to any one of [ 24 ] to [ 28 ], wherein the nitrogen atom-containing heterocyclic ring containing the ring A and the ring B is a heterocyclic ring having a 2, 2' -bipyridine structure with or without a substituent.

[ 30 ] the carbon monoxide production system according to any one of [ 24 ] to [ 29 ], wherein R is¹、R²、R³、R⁴、X¹、X²And X³The substituted or unsubstituted hydrocarbon group is an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group or an aromatic hydrocarbon group (these groups may have 1 to 3 substituents selected from the group consisting of a primary amino group, a secondary or tertiary amino group, a hydroxyl 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).

Even a low concentration of CO if the catalyst and electrochemical treatment of the present invention are used₂Or can be prepared from CO by a simple method₂Carbon monoxide (CO) or formic acid is efficiently produced. Therefore, for example, CO-containing gas can be generated from facilities such as a thermal power plant and an iron works, which generate combustion exhaust gas containing organic matter including petroleum₂The exhaust gas efficiently produces carbon monoxide or formic acid which can be changed into various chemical raw materials. Therefore, carbon monoxide or formic acid, which is a raw material of a chemical substance that is useful as hydrocarbons, hydrogen, or the like and that accumulates energy, can be produced from a combustion exhaust gas of fossil fuel such as petroleum, coal, natural gas, or the like, and can contribute to energy reuse and CO₂Both are reduced.

Drawings

Fig. 1 is a conceptual diagram of a carbon monoxide production system according to the present invention.

Fig. 2 is a conceptual diagram of an example of a reaction-side cell chamber of the carbon monoxide production system according to the present invention. The symbols in the figure are the same as in fig. 1.

FIG. 3 shows the CO passage for 30 minutes for a solution 4 hours after the TEOA addition₂IR spectrum change in gas (solvent: DMF-TEOA (5: 1 v/v)). Before ventilation: gray line, after aeration: black lines.

FIG. 4 shows the pair of CO₂After the aeration (0 to 120 minutes), the IR spectrum of the solution was changed by Ar gas (solvent: DMF-TEOA (5: 1 v/v)).

FIG. 5 shows a sample containing Re-CO₂ESI-MS spectroscopy (solvent: MeCN) of a DMF-TEOA mixed solution of TEOA (5: 1 v/v).

Fig. 6 shows the IR spectrum (solid black line) after aeration and a curve fit. (the dotted line to the right indicates a peak starting from the DMF coordinated complex, -O-CO-OCH₂CH₂NR₂(R＝CH₂CH₂OH) coordinated complexes, TEOA coordinated complexes. The solid gray line is the sum of these 3 peaks). Substituents at the 4, 4' positions: (a) hydrogen, (b) methyl, (c) methoxy, (d) bromo.

FIG. 7 shows the reaction of Re-CO₂Electrochemical CO with TEOA as catalyst₂Change in CO production and current in the reduction experiment.

Fig. 8 shows changes in CO production and current when TEOA is added.

Fig. 9 shows the results of Cyclic Voltammetry (CV) measurements of the Re complex performed to set the applied voltage. The baseline (baseline) in the figure indicates CO without complex₂Results of measurement under an atmosphere, and results of measurement under an Ar atmosphere when no complex and a complex are present under Ar (under Ar), in CO₂Lower (under CO)₂) Denotes CO without and with complexes₂And (4) measurement results under an atmosphere.

Fig. 10 shows the results of Cyclic Voltammetry (CV) measurements of the Mn complexes performed to set the applied voltage. The dotted line represents an Ar atmosphere. Solid line indicates CO₂Under an atmosphere.

FIG. 11 shows the reaction of Mn-CO₂Electrochemical CO with TEOA as catalyst₂Change in current value in the reduction experiment.

FIG. 12 shows the reaction of Mn-CO₂Electrochemical CO with TEOA as catalyst₂The amount of CO produced in the reduction experiment.

FIG. 13 shows CO of various manganese triethanolamine adduct complexes₂IR spectrum at 10%.

FIG. 14 shows various concentrations of CO in DMF-DEOA of Mn complexes₂The IR spectrum under the atmosphere changes.

FIG. 15 shows the setting of the applied voltageCO in DMF-DEOA of Mn complex₂The results were measured by Cyclic Voltammetry (CV) under an atmosphere.

FIG. 16 shows the reaction of Mn-CO₂Electrochemical CO with DEOA as catalyst₂The amount of formic acid produced and the change in the current value in the reduction experiment.

Detailed Description

In the invention, the CO is₂The catalyst used in the electrochemical reduction to CO is a metal complex represented by the general formula (1).

(wherein X represents OR¹、SR¹、NR²R³R⁴Or PX¹X²X³，

Y represents CO OR OR¹、SR¹、NR²R³R⁴Or PX¹X²X³，

The ring A and the ring B, which may be the same or different, represent a nitrogen atom-containing heterocycle having a substituent or not,

R¹represents a hydrocarbon group with or without a substituent,

R²、R³and R ⁴1 to 3 of them are the same or different and each represents a hydrocarbon group having or not having a substituent, and the remainder represents a hydrogen atom,

In another aspect of the invention, the catalyst is in the form of a CO₂The catalyst used in the electrochemical reduction to formic acid is a metal complex represented by the general formula (2).

(in the formula, M₁Represents manganese, ruthenium or iron,

x represents OR¹、SR¹、NR²R³R⁴Or PX¹X²X³，

Y represents CO OR OR¹、SR¹、NR²R³R⁴Or PX¹X²X³，

The ring A and the ring B, which may be the same or different, represent a nitrogen atom-containing heterocycle having a substituent or not,

R¹represents a hydrocarbon group with or without a substituent,

R²、R³and R ⁴1 to 3 of them are the same or different and each represents a hydrocarbon group having or not having a substituent, and the remainder represents a hydrogen atom,

In the general formula (2), as M₁More preferred is manganese or ruthenium, and further preferred is manganese.

In the general formulae (1) and (2), X represents OR¹、SR¹、NR²R³R⁴Or PX¹X²X³Y represents CO OR OR¹、SR¹、NR²R³R⁴Or PX¹X²X³. X and Y may be the same or different. Here, R¹Represents a hydrocarbon group with or without a substituent. R²、R³And R ⁴1 to 3 of them are the same or different and represent a hydrocarbon group with or without a substituent, and the remainder represents a hydrogen atom.

X¹、X²And X ³1 to 3 of (a) are the same or different and each represents a substituted or unsubstituted hydrocarbon group or a substituted or unsubstituted hydrocarbon oxy group, and the remainder represents a hydrogen atom or a hydroxyl group.

From R¹、R²、R³、R⁴、X¹、X²And X³To representThe hydrocarbon group(s) of (b) is the same or different, and preferably an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group or an aromatic hydrocarbon group (these groups may have 1 to 3 substituents selected from the group consisting of a primary amino group, a secondary amino group or a tertiary amino group, a hydroxyl 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).

Examples of the alkyl group include a linear or branched alkyl group having 1 to 20 carbon atoms, preferably a linear or branched alkyl group having 1 to 12 carbon atoms, and more preferably a linear or branched alkyl group having 1 to 6 carbon atoms. Specific examples thereof include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl and n-hexyl.

The alkenyl group includes a linear or branched alkenyl group having 2 to 20 carbon atoms, preferably a linear or branched alkenyl group having 2 to 12 carbon atoms, and more preferably a linear or branched alkenyl group having 2 to 6 carbon atoms. Specific examples thereof include a vinyl group, a 2-propenyl group, a 1-propenyl group, and a 1-butenyl group.

Examples of the cycloalkyl group include C₃-C₈Specific examples of the cycloalkyl group include cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl. Examples of the cycloalkenyl group include C₃-C₈Specific examples of the cycloalkenyl group include cyclobutenyl, cyclopentenyl, and cyclohexenyl.

The aromatic hydrocarbon group may include C₆-C₁₄Specific examples of the aromatic hydrocarbon group include a phenyl group, a naphthyl group, and a phenanthryl group.

As a result of X¹、X²And X³The hydrocarbyloxy group having or not having a substituent(s) represented by (a) may be the same or different and includes an alkoxy group, an alkenyloxy group, a cycloalkoxy group, a cycloalkenyloxy group or an aromatic hydrocarbyloxy group (these groups may have 1 to 3 substituents selected from a primary amino group, a secondary amino group or a tertiary amino group, a hydroxyl 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).

Examples of the alkoxy group include a linear or branched alkoxy group having 1 to 20 carbon atoms, preferably a linear or branched alkoxy group having 1 to 12 carbon atoms, and more preferably a linear or branched alkoxy group having 1 to 6 carbon atoms. Specific examples thereof include methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, n-pentoxy group, and n-hexoxy group.

Examples of the alkenyloxy group include a linear or branched alkenyloxy group having 2 to 20 carbon atoms, preferably a linear or branched alkenyloxy group having 2 to 12 carbon atoms, and more preferably a linear or branched alkenyloxy group having 2 to 6 carbon atoms. Specific examples thereof include an ethyleneoxy group, a 2-propyleneoxy group, a 1-propyleneoxy group, and a 1-butyleneoxy group.

Examples of the cycloalkoxy group include C₃-C₈Specific examples of the cycloalkoxy group include a cyclopropyloxy group, a cyclobutyloxy group, a cyclopentyloxy group, and a cyclohexyloxy group. As the cycloalkenyloxy group, there may be mentioned C₃-C₈Specific examples of the cycloalkenyloxy group include a cyclobutenyloxy group, a cyclopentenyloxy group, a cyclohexenyloxy group and the like.

The aryloxy group may include C₆-C₁₄Specific examples of the aryloxy group include a phenoxy group, a naphthoxy group, and a phenanthroxy group.

As the group which may be substituted in these hydrocarbon or hydrocarbonoxy groups, more preferred is one selected from the group consisting of amino group and C_1-6Alkylamino radical, di (C)_1-6Alkyl) amino, di (hydroxy C)_1-6Alkyl) amino, hydroxy C_1-6Alkylamino, hydroxy, C_1-6Alkoxy radical, C_1-14Aryloxy group, halogen atom, nitro group, cyano group, formyl group, C_1-6Alkanoyl and C_6-141-3 of the arylcarbonyl groups. Further, more preferably selected from amino group and C_1-6Alkylamino radical, di (C)_1-6Alkyl) amino, hydroxy C_1-6Alkylamino, di (hydroxy C)_1-6Alkyl) amino, hydroxy, C_1-6Alkoxy radical, C _1-141 to 3 of aryloxy groups and halogen atoms.

R²、R³And R ⁴1 to 3 of the above hydrocarbon groups, and the balance being hydrogen atoms. In addition, X¹、X²And X ³1 to 3 ofThe above-mentioned hydrocarbon group or hydrocarbon oxy group, and the remainder is a hydrogen atom or a hydroxyl group.

More preferably X is OR¹Or NR¹R²R³。

Further preferred X is-OC_2-8Alkyl NHC_2-8Alkyl OH, -OC_2-8Alkyl radical N (C)_2-8Alkyl OH)₂、-NH(C_2-8Alkyl OH) or-N (C)_2-8Alkyl OH)₂. Further preferred X is-OC_2-6Alkyl NHC_2-6Alkyl OH, -OC_2-6Alkyl radical N (C)_2-6Alkyl OH)₂、-NH(C_2-6Alkyl OH) or-N (C)_2-6Alkyl OH)₂. Further preferred X is-OC₂H₄NHC₂H₄OH、-C₂H₄N(C₂H₄OH)₂、-NH(C₂H₄OH) or-N (C)₂H₄OH)₂. More preferably, Y is CO OR OR¹Or NR¹R²R³Further preferably, Y is CO.

As the nitrogen atom-containing heterocyclic ring containing rings a and B, a heterocyclic ring having a 2, 2' -bipyridine structure with or without a substituent is preferable. The group which may be substituted in the hetero ring is preferably 1 to 4 groups selected from an alkyl group, an alkoxy group, an aryloxy group, a halogen atom and an alkanoyl group, and more preferably C_1-6Alkyl radical, C_1-6Alkoxy radical, C_6-14Aryloxy group, halogen atom and C _1-61 to 4 alkanoyl groups.

As the heterocycle having a 2, 2' -bipyridyl structure, for example, a heterocycle represented by the following formula (3) or (4) is preferable.

(in the formula, R⁷、R⁸、R⁹、R¹⁰And R¹¹The same or different, represents a hydrogen atom, an alkyl group, an alkoxy group, an aryloxy group, a halogen atom or an alkanoyl group)

Among them, the heterocyclic ring of the formula (3) is more preferable. More specifically, 2 ' -pyridine, 4 ' -dimethyl-2, 2 ' -bipyridine, 4 ' -dibromo-2, 2 ' -bipyridine, and 4,4 ' -dimethoxy-2, 2 ' -bipyridine are preferable.

Among the metal complexes represented by the above general formula (2), the metal complex represented by the following general formula (2a) is novel and more preferred.

(in the formula, M₁Represents manganese, ruthenium or iron,

x represents O (CH)₂)_nNR⁵R⁶、NR⁵R⁶Or PX¹X²X³，

Y represents CO, O (CH)₂)_nNR⁵R⁶、NR⁵R⁶Or PX¹X²X³，

The ring A and the ring B, which may be the same or different, represent a nitrogen atom-containing heterocycle having a substituent or not,

X¹、X²and X ³1 to 3 of them are the same or different and each represents a substituted or unsubstituted hydrocarbon group or a substituted or unsubstituted hydrocarbon oxy group, and the remainder represents a hydrogen atom or a hydroxyl group,

R⁵and R⁶Identical or different, represents an alkyl group, a hydroxyalkyl group or a hydrogen atom,

n represents a number of 2 to 8. )

As M₁More preferred are manganese and ruthenium, and still more preferred is manganese.

The nitrogen atom-containing heterocyclic ring containing the ring a and the ring B is preferably a heterocyclic ring having a 2,2 '-bipyridine structure with or without a substituent, more preferably a heterocyclic ring of the formula (3) or the formula (4), further preferably a heterocyclic ring of the formula (3), and particularly preferably 2, 2' -bipyridine, 4 '-dimethyl-2, 2' -bipyridine, 4 '-dibromo-2, 2' -bipyridine.

O(CH₂)_nNR⁵R⁶And NR⁵R⁶R in (1)⁵And R⁶Identical or different, represent alkyl,Hydroxyalkyl groups or hydrogen atoms. More specifically, as R⁵And R⁶Examples thereof include C_1-6Alkyl, hydroxy C_1-6Alkyl or hydrogen atoms, preferably C_1-4Alkyl, hydroxy C_1-6Alkyl groups or hydrogen atoms.

As a result of X¹、X²And X³The hydrocarbon group having or not having a substituent(s) represented by (a) is preferably an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group or an aromatic hydrocarbon group (these groups may have 1 to 3 substituents selected from the group consisting of a primary amino group, a secondary amino group or a tertiary amino group, a hydroxyl 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).

From X¹、X²And X³The hydrocarbyloxy groups which may be substituted or unsubstituted are the same or different and include an alkoxy group, an alkenyloxy group, a cycloalkoxy group, a cycloalkenyloxy group, or an aryloxy group (these groups may have 1 to 3 substituents selected from a primary amino group, a secondary or tertiary amino group, a hydroxyl 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).

More preferably X is O (CH)₂)_nNR⁵R⁶Or NR⁵R⁶。

Further preferred X is-OC_2-8Alkyl NHC_2-8Alkyl OH, -OC_2-8Alkyl radical N (C)_2-8Alkyl OH)₂、-NH(C_2-8Alkyl OH) or-N (C)_2-8Alkyl OH)₂. Further preferred X is-OC_2-6Alkyl NHC_1-6Alkyl OH, -OC_2-6Alkyl radical N (C)_2-6Alkyl OH)₂、-NH(C_2-6Alkyl OH) or-N (C)_2-6Alkyl OH)₂. Further preferred X is-OC₂H₄NHC₂H₄OH、-OC₂H₄N(C₂H₄OH)₂、-NH(C₂H₄OH) or-N (C)₂H₄OH)₂. More preferably, Y is CO or O (CH)₂)_nNR⁵R⁶Or NR⁵R⁶Further preferably, Y is CO.

The metal complex represented by the general formula (1) or (2) can be produced, for example, according to the following reaction formula.

(wherein M represents rhenium, manganese, ruthenium or iron, A, B, X and Y are the same as defined above)

That is, the metal complex of formula (1) or (2) can be produced by reacting the acetonitrile (MeCN) complex metal complex of formula (5) with a solvent having a relatively low coordination energy, for example, dimethylformamide to convert it into a solvent complex (6), and reacting it with X-H and/or Y-H (7) under alkaline conditions. The conversion from the acetonitrile complex (5) to the solvent complex may be carried out by dissolving the complex of formula (5) in the above solvent and leaving it in the dark under an Ar atmosphere for one night. Then, in order to produce a complex of formula (1) or (2), the complex of formula (6) is added to X-H (7), and left to stand in the dark under an Ar atmosphere for several hours.

The secondary CO of the invention₂The method for producing CO by electrochemical reduction is characterized by comprising the following steps (a) and (b).

A step (a): reacting carbon dioxide with a metal complex represented by the above general formula (1),

a step (b): a voltage is applied to a reactant of carbon dioxide and a metal complex represented by the general formula (1).

The reaction in the step (a) and the step (b) is considered to proceed as in the following reaction formula.

(wherein A, B, X and Y are the same as described above)

Namely, by using a metal complex of the formula (1) with CO₂To produce CO as shown in the formula (8)₂The adduct is subjected to an external voltage, whereby CO is released. CO of formula (8)₂The formation of the adduct can be confirmed by means of IR spectrum, MS spectrum and NMR spectrum.

The reaction may be carried out in an electrolyte solution, i.e., a polar solvent, from CO of the formula (8)₂The protic polar solvent is preferred from the viewpoint that the oxygen atom generated as a by-product is protonated to change to water while the adduct releases CO. Examples of the protic polar solvent include water, an alcohol solvent, an amine solvent, a thiol solvent, and an aminoalcohol solvent. Among them, solvents corresponding to X and/or Y in formula (1) are particularly preferred.

The amount of the metal complex of formula (1) used is preferably 0.01 mM-100 mM, more preferably 0.05 mM-10 mM, in the electrolyte solution.

Introduced CO₂It is not necessary for 100% CO₂Even if the CO content is 0.03-100%₂The CO generation reaction proceeds as well. 0.03% CO₂The gas being CO in air₂And (4) concentration. In addition, approximately 10% of CO may not be included₂CO of exhaust gas from thermal power plant or the like₂Concentrated for direct use.

In addition, CO₂So long as it contains CO₂Introducing gases into the electrolyte solution, e.g. to contain CO₂The gas may be bubbled into the electrolyte solution, and is easy.

Next, in setting the applied voltage, it is important to previously perform Cyclic Voltammetry (CV) measurement to grasp the applied voltage level. Cyclic Voltammetry (CV) measurements are methods that linearly scan the electrode potential and measure the response current. In the present invention, (b) Ar gas and (c) CO-containing gas are introduced in a state (a) where the metal complex of the present invention is not added to the electrolyte (blank) and a state where the metal complex is added₂And (5) carrying out cyclic voltammetry measurement on the gas. By obtaining the current-potential curve obtained under the condition (c) described above, the applied voltage (reduction potential) can be obtained from the rise potential of the response current. The voltage may be applied by reacting in an electrochemical cell having a working electrode and a counter electrode. The voltage is preferably 1.0V-2.5 Vvs₃。

Specifically, the steps (a) and (b) are preferably performed in an electrochemical cell having a working electrode and a counter electrode, and the following steps (a1) and (b1) are preferably performed.

Step (a 1): introducing carbon dioxide into a solution containing the metal complex in an electrochemical cell,

step (b 1): a negative voltage and a positive voltage are applied to the working electrode and the counter electrode of the electrochemical cell, respectively.

More specifically, a system for producing carbon monoxide from carbon dioxide by electrochemical reduction, as shown in fig. 1, for example, is preferably used, and is characterized by comprising:

an electrochemical cell unit comprising a solution (1) containing a metal complex, a working electrode (4), and a counter electrode (6),

an injection part (gas injection port) (2) for injecting carbon dioxide into the solution (1) containing the metal complex in the electrochemical cell part,

a potentiostat (8) having a voltage source capable of applying a positive or negative voltage between the working electrode (4) and the counter electrode (6) in the electrochemical cell portion, and

a discharge part (gas discharge port) (3) for discharging carbon monoxide generated in the solution (1) containing the metal complex,

the system generates carbon monoxide by applying a positive or negative voltage to a reactant of the above metal complex formed from a solution containing the above metal complex and carbon dioxide.

The more specific apparatus of figure 1 is shown in figure 2. The following description is made with reference to fig. 1 and 2.

In FIG. 1 and FIG. 2, (2) is CO₂Injection part (gas injection port), CO contained in white circle in FIG. 2₂Is introduced into a solution containing the metal complex. In fig. 1 and 2, (1) is a solution containing the metal complex in an electrochemical cell part having a solution containing a working electrode (4), a reference electrode (5), and a counter electrode (6) in the cell part. CO 2₂The addition and reduction reaction to CO proceed via the metal complex of the working electrode. As the working electrode, glassy carbon or the like is used. As the counter electrode, platinum or the like is used.

In fig. 1, (8) is a potentiostat for applying a positive or negative voltage to the working electrode and the counter electrode in the electrochemical cell part.

In fig. 2, (3) is a gas discharge unit for discharging CO (gray point) generated in the metal complex-containing solution. The CO discharge unit may be provided with a detection unit (detector) for detecting the generation of carbon monoxide by various CO sensors (semiconductor type, gas heat transfer type, etc.) or a gas chromatograph (Micro-GC).

The system of the present invention can be operated from about 10% CO concentration as shown in FIGS. 1 and 2₂Since CO is continuously produced from a gas, it can be installed in a thermal power plant, a cement plant, a glass production plant, or the like, where CO is produced by burning organic matter₂In the apparatus of (1). In addition, reduction of Fe with CO may be performed in a blast furnace of an iron works₂O₃In the apparatus of (1). In this case, the CO obtained by the method or system of the present invention may be used as a reducing agent, and the CO produced may be further processed₂Used as a feedstock to regenerate CO. Further, if CO obtained by the method or system of the present invention is used as a raw material, a wide range of hydrocarbon compounds can be produced.

The secondary CO of the invention₂A process for producing formic acid by electrochemical reduction, which comprises the following steps (a) and (b).

A step (a): reacting carbon dioxide with a metal complex represented by the above general formula (2),

a step (b): a voltage is applied to a reactant of carbon dioxide and a metal complex represented by the general formula (2).

The reaction in the step (a) and the step (b) is considered to proceed as in the following reaction formula.

(in the formula, A, B, M₁X and Y are the same as above)

Namely, by using a metal complex of the formula (2) with CO₂To produce CO of formula (9)₂The adduct is subjected to an external voltage, whereby formic acid is liberated. CO of formula (9)₂The adduct formation can be carried out by IR spectroscopy and MS spectroscopyAnd (6) line confirmation.

The reaction may be carried out in an electrolyte solution, i.e., a polar solvent, but is derived from CO of the formula (9)₂The protic polar solvent is preferred from the viewpoint that the adduct releases formic acid. Examples of the protic polar solvent include water, an alcohol solvent, an amine solvent, a thiol solvent, and an aminoalcohol solvent. Among them, it is particularly preferable to use a solvent corresponding to X and/or Y in the formula (2).

The amount of the metal complex of formula (2) to be used is preferably 0.01 mM-100 mM, more preferably 0.05 mM-10 mM, in the electrolyte solution.

Introduced CO₂It is not necessary for 100% CO₂Even if the CO content is 0.03-100%₂The CO generation reaction proceeds as well. 0.03% CO₂The gas being CO in air₂And (4) concentration. In addition, approximately 10% of CO may not be included₂The exhaust gas from the thermal power plant is used as it is in a concentrated state.

In addition, CO₂So long as it contains CO₂Introducing gases into the electrolyte solution, e.g. to contain CO₂The gas may be bubbled into the electrolyte solution, and is easy.

According to the method of the invention, the content of CO can be controlled to be about 0.03 percent₂The gas continuously produces formic acid, so that it is possible toInstalled in thermal power stations, cement manufacturing facilities, glass manufacturing facilities, etc. where organic matter is burned to generate CO₂In the apparatus of (1).

40页详细技术资料下载

上一篇：一种医用注射器针头装配设备

下一篇：一种便携式的一氧化氮发生装置及其使用方法

Electrochemical reduction of carbon dioxide

相关技术

网友询问留言