KR20200090668A - Electrochemical system for producing ammonia from nitrogen oxides and preparation method thereof - Google Patents

Abstract

The present invention is to provide an electrochemical system capable of producing ammonia from nitrogen oxides, which can produce ammonia with a high selectivity while conducting reactions under the conditions of room temperature and atmospheric pressure; and a method of producing the same. In particular, the present invention provides an electrochemical system for producing ammonia from nitrogen oxides, characterized by comprising: a cathode electrode at which reduction reactions of complexes of nitrogen oxides and metal complexes take place; an anode electrode; a reference electrode; an electrolyte comprising metal complexes; and a nitrogen oxide supply unit. In addition, the present invention provides a method of producing ammonia from nitrogen oxides, comprising the steps of: introducing nitrogen oxides into an electrochemical system; having the introduced nitrogen oxides and metal complexes in an electrolyte to form complexes; and conducting an electrical reduction reaction of the formed complexes. Accordingly, by electrochemically reducing nitrogen oxides under the conditions of room temperature and atmospheric pressure, the present invention can produce ammonia with a high selectivity.

Description

Electrochemical system for manufacturing ammonia from nitrogen oxides and manufacturing method{ELECTROCHEMICAL SYSTEM FOR PRODUCING AMMONIA FROM NITROGEN OXIDES AND PREPARATION METHOD THEREOF}

The present invention relates to an electrochemical system for producing ammonia from nitrogen oxides and a method for producing ammonia from nitrogen oxides.

The present invention relates to a technique for selectively converting nitrogen oxide adsorbed on a metal complex, particularly nitrogen monoxide, into ammonia using an electrochemical method, and more specifically, a metal in which nitrogen oxide such as nitrogen monoxide is selectively adsorbed It relates to a reaction for generating ammonia ions by adding 5 electrons and 4 hydrogen ions to nitrogen monoxide, for example, through the supply of electrical energy to a complex, and an electrochemical system for this.

Nitric oxide (NO) is a kind of nitrogen oxide (NOX) that is generally generated by oxidation of nitrogen in the combustion process, and in itself causes respiratory-related diseases, and is secondarily exposed to the atmosphere to cause fine dust It is a representative air pollutant that causes various environmental problems such as (particulate matter), photochemical smog, acid rain and ozone layer destruction. Particularly, in countries with economically rapid growth, such as China and India, a large amount of nitrogen oxides are emitted due to excessive industrial activities, causing fine dust and directly affecting neighboring countries. Secondary fine dust can be generated through various causative substances, but nitrogen oxides and sulfur oxides have been reported to be the highest, accounting for more than 65% of exhaust gas emitted from industrial activities. Due to its high water solubility and chemical reactivity, the treatment of sulfur oxides can be easily accomplished by precipitating them as solids at a relatively low cost, such as the Limestone process, whereas in the case of nitrogen oxides, nitrogen monoxide has little water solubility and cannot be treated in water systems. And high temperature reaction and the use of expensive noble metal catalysts and reducing agents are essential.

Commercially available nitrogen oxide removal technology includes selective catalytic reduction (SCR), non-selective catalytic reduction (NSCR), occluded catalytic device (Lean NOX trap, LNT), exhaust gas Exhaust gas recirculation (EGR) and currently under development include electron beam, corona discharge, biological treatment (BioDeNOX) and solid oxide electrolysis devices. Among them, the most widely used technology in terms of DeNOX efficiency commercially is a large-scale emission point pollutant such as the energy industry including power plants, manufacturing industries such as petrochemical, and steel industries, in terms of securing a selective reduction catalyst or space. Mainly used, there is a high cost of operating conditions, the cost of the catalyst and reducing agent used. Recently, through improvement, the price of the catalyst and the size of the reactor have been further improved, and thus some of them have been applied to mobile pollution sources such as vehicles and ships using diesel, but there are difficulties in application due to the lack of physical space.

On the other hand, nitrogen monoxide (NO, Nitric Oxide), which accounts for about 95% of nitrogen oxides, is capable of oxidation or reduction by exchanging electrons, that is, it has electrochemical activity, which converts into a nitrogen compound that is harmless to the environment by supplying external electrical energy. This suggests that this is possible. If the nitrogen oxide oxidization take the former case, the nitrite ion (NO ₂ ^-), nitrate ion (NO ₃ ^-) in a conversion and for reducing, in a switchable product is nitrous oxide (N ₂ O), nitrogen (N ₂ ), amine hydroxide (NH ₂ OH), hydrazine (N ₂ H ₄ ), and ammonia (NH ₃ ). Nitrogen monoxide is a specific nitrogen compound through optimization according to variables such as electrochemical reaction catalyst, electrolyte and electric energy input. (Eg nitrate ion, ammonia) can be selectively converted, and it can be said that it has an economic advantage compared to the existing denitrification technology that is simply treated with nitrogen in terms of the production of high value-added materials. In particular, in the case of ammonia, safety and storage are easy, and since it can be used as a carrier of hydrogen ions, which are spotlighted as the next generation transportation fuel, various studies on production methods and utilization methods have been conducted with a lot of investment. In the case of the Haber process, which is a commercially available ammonia production process, it is operated at a high temperature of 500 degrees or higher and a high pressure of 15 to 25 MPa to break the triple bond of nitrogen, and hydrogen must be supplied as a precursor. There is a big disadvantage of energy and cost consumption. To replace this, a study on the electrochemical process to produce ammonia by adding hydrogen ions by electrochemically reducing nitrogen (reduction), similarly, research to produce ammonia using solar energy, and directly using ammonia as a fuel Research on fuel cells to be utilized is being actively conducted worldwide.

The production of ammonia through electrochemical nitrogen reduction has an advantage in that it is easy to operate at normal temperature and pressure, compared to the harbor process, and uses nitrogen and pure water in the atmosphere as precursors, but most of the supplied electric energy is ammonia. Since it is consumed as a side reaction, not a production, that is, a hydrogen generation reaction, the conversion efficiency is very low at only 3% based on the water-based reaction, making it difficult to commercialize.

For example, Republic of Korea Patent No. 10-1767894 is a nitrogen circulation type nitrogen oxide treatment system using an ammonia synthesis cell, specifically, the invention of a nitrogen circulation type nitrogen oxide treatment system and method. The system includes an exhaust gas supply line for supplying exhaust gas containing NOx and SOx to a desulfurizer; A treatment gas supply line for supplying the treatment gas from which SOx has been removed through the desulfurizer to a NOx scrubber; A treatment gas discharge line that absorbs NOx of the treatment gas and discharges the remaining gas using an absorbent in the NOx scrubber; A NOx absorbing solution supply line for supplying the absorbing solution absorbing NOx from the NOx scrubber to a NOx and absorbent separator; And a NOx supply line supplying the NOx separated from the NOx and the absorbent separator to an ammonia synthesis cell, but supplying it through a concentrator, wherein the ammonia synthesis cell comprises an oxygen ion conductive membrane; And two electrodes coated on both sides of the oxygen ion conductive film, wherein the electrodes are electrically connected to a nitrogen-circulating nitrogen oxide treatment system. However, the above technology uses pure nitrogen oxide as a raw material in a reduction process for ammonia production, and thus has a problem of maintaining a high temperature environment for high selectivity.

In addition, Republic of Korea Patent Publication No. 10-2017-0021713 is an invention related to an electrolysis device for collecting nitrogen compounds using iron-ethylenediamine tetraacetic acid, specifically, an electrolysis device for collecting nitrogen compounds comprising the following components: ( a) a reactor body containing a compound of a divalent metal ion and a chelating agent therein; (b) anode and cathode; (c) a collection tube for collecting nitrogen compounds, including the anode therein; (d) a gas inlet for supplying a source gas containing a nitrogen compound to the reactor body; And (e) a discharge port for discharging the gas from which nitrogen compounds have been removed after being trapped inside the reactor. However, the above technology only uses a chelating agent to adsorb the nitrogen compound, and after adsorption, only the nitrogen compound is recovered through the oxidation reaction of the anode electrode, and the process of manufacturing ammonia using it is specifically disclosed. It is not.

Accordingly, there is a need for a system and a manufacturing method capable of producing ammonia with high selectivity while performing a reaction at room temperature and pressure.

Republic of Korea Registered Patent No. 10-1767894 Republic of Korea Patent Publication No. 10-2017-0021713

An object of the present invention is to provide an electrochemical system for producing ammonia from a nitrogen oxide capable of producing ammonia with high selectivity while performing a reaction at room temperature and pressure conditions, and a method for manufacturing the same.

To this end, the present invention manufactures ammonia from nitrogen oxides comprising a cathode electrode, an anode electrode, a reference electrode, an electrolyte including a metal complex compound, and a nitrogen oxide supply unit in which a reduction reaction of a complex between a nitrogen oxide and a metal complex compound occurs. Provides an electrochemical system.

In addition, the present invention is the step of introducing a nitrogen oxide into the electrochemical system; Forming a complex between the introduced nitrogen oxide and the metal complex compound in the electrolyte; And performing an electrical reduction reaction on the formed complex.

According to the present invention, ammonia is produced by electrochemically reducing nitrogen oxides at normal temperature and pressure, but ammonia can be produced with high selectivity. That is, there is an effect capable of overcoming the low temperature selectivity and high cost of commercially available denitrification technologies while simultaneously producing a high value-added material. In addition, the phenomenon in which the metal complex compound used in the process is oxidized by oxygen and loses the adsorption property can be overcome by maintaining an electrochemical reduction atmosphere.

1 is a conceptual diagram of an electrochemical system for selectively converting nitrogen monoxide;
2 is a schematic diagram of an electrochemical system according to the present invention;
3A and 3B are graphs of linear sweep voltammetry for carbon, platinum, copper, and silver working electrodes under conditions of aqueous solution of a metal complex with nitrogen monoxide adsorbed in an experiment using an electrochemical system;
4A to 4D show a current for a product after performing a time-current current method (Chronoamperometry, CA) on carbon, platinum, copper, and silver working electrodes in an aqueous solution condition of a metal complex with nitrogen monoxide adsorbed in an experiment using an electrochemical system. It is a graph showing the efficiency (Faraday efficiency);
5 is a graph showing partial current density for ammonia for carbon, platinum, copper, and silver working electrodes under conditions of aqueous solution of a metal complex adsorbed with nitrogen monoxide in an experiment using an electrochemical system; And
6 is a graph showing the ammonia-current density when the complex is formed and when not.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by a person skilled in the art to which the present invention pertains. In general, the nomenclature used herein is well known and commonly used in the art. An object of the present invention is to provide an electrochemical system capable of selectively adsorbing nitrogen oxides, in particular nitrogen monoxide, and simultaneously converting them to ammonia.

To this end, the present inventors manufacture ammonia from nitrogen oxide, which comprises a cathode electrode, an anode electrode, a reference electrode, an electrolyte including a metal complex compound, and a nitrogen oxide supply unit, in which a reduction reaction of the complex between the nitrogen oxide and the metal complex compound occurs. Developed an electrochemical system (see Fig. 2).

In this case, the nitrogen oxide used as a raw material in the present invention may be nitrogen monoxide in that nitrogen monoxide accounts for about 95% of the nitrogen oxide.

Next, the metal constituting the metal complex may use a divalent metal such as iron, magnesium, potassium, zinc or chromium, wherein the ions of the metal combine with the complex to form a compound, and this compound is, for example, monoxide It serves to selectively adsorb nitrogen in the liquid phase. The use of iron or magnesium can be considered in view of the excellent affinity with nitrogen monoxide, and particularly the use of iron ions can be considered.

The complex compound constituting the metal complex of the present invention comprises one salt selected from the group consisting of ethylenediamine tetraacetic acid (EDTA), 1,2 cyclohexanediamine tetraacetic acid (CyDTA), and sodium nitro triacetic acid (NTA). Can be used. The complex compound refers to a compound that combines with a metal to form a metal complex compound, and can be used without limitation as a compound that performs such functions. However, the use of EDTA in that it is fast in kinetic and capable of reacting with various metals Can be considered.

In the present invention, as the anode electrode, metals and non-metals of a wide variety of materials may be used, and in particular, one or more conductive metals selected from graphite, platinum, titanium, nickel and gold, and platinum, ruthenium, osmium, palladium, and iridium, It may be characterized by consisting of one or more mixtures or oxides selected from carbon and transition metals. The electrode material of the anode electrode can be used without particular limitation, but it is preferable to use iron, aluminum, copper, silver, nickel, etc., in the form of oxide, which can voluntarily undergo an oxidation reaction when electric energy is introduced into the anode electrode material. Do. Most preferably, a platinum electrode or an insoluble electrode (DSA) may be used.

In addition, in the present invention, in the cathode electrode, a reduction reaction of the complex between the nitrogen oxide and the metal complex in the electrolyte occurs as in the following reaction formula, iron, free carbon (Glassy Carbon, GC), aluminum, copper, silver, nickel, It is possible to use one or more selected from the group consisting of platinum, their oxides, and their alloys, and according to the experimental results, it is possible to consider using silver in that the ammonia production rate is very fast.

On the other hand, when the material of the cathode electrode used in the present invention is silver or copper, the potential difference applied to the system is in the range of 0.2Volt to -0.4Volt compared to the hydrogen reference electrode, and the potential difference applied in the case of free carbon is -0.3Volt to In the range of -0.4 Volt, in the case of platinum, the potential difference applied may be in the range of 0.4 Volt to -0.4 Volt. The system can be operated even at a potential difference greater than -0.4 Volt compared to the hydrogen reference electrode, but it is possible to consider applying the potential difference in the above range in terms of the selectivity of ammonia. In the electrochemical system according to the present invention, it is necessary to sufficiently reduce nitrogen oxides at the cathode, and at the same time, it is necessary to increase the selectivity for ammonia by suppressing the occurrence of side reactions. The potential difference applied together can be adjusted.

The pH of the electrolyte contained in the electrochemical system of the present invention may be maintained in a neutral range of 6 to 8. In terms of ammonia production, it is preferable in terms of selectivity and stability of the complex to maintain the pH of the electrolyte in the neutral range as described above.

The electrochemical system of the present invention includes a reference electrode, and for example, an Ag/AgCl electrode can be used.

The electrochemical system of the present invention includes an electrolyte, and the electrolyte includes a metal complex compound for complex formation.

The electrochemical system of the present invention includes a nitrogen oxide supply unit for supplying nitrogen oxide as a raw material into the system, through which the nitrogen oxide as a raw material is supplied into the system, and a metal complex in an electrolyte containing a metal complex compound To form a complex and reduction proceeds on the cathode electrode.

For example, when using Cheil-ethylenediamine tetraacetic acid (Fe(II)EDTA) as a liquid adsorbent for selective adsorption of nitrogen monoxide, the reaction formula is as follows.

Fe(II)EDTA (aq) + NO(g) -> Fe(II)EDTA-NO (aq) [Scheme 1]

The chemical reaction is performed in the cathode cell 100 of FIG. 2 of the electrochemical device provided in the present invention. When a potential difference is applied by an external power source, water is oxidized in the anode cell to generate oxygen molecules, hydrogen ions, and electrons at the same time. In the cathode cell, Fe(II)EDTA-NO adsorbed with nitrogen monoxide receives electrons and a reduction reaction occurs and can be converted into various products.

Fe (Ⅲ) EDTA (aq) + e - -> Fe (Ⅱ) EDTA (aq) [ Scheme 2]

2Fe (Ⅱ) EDTA-NO ( aq) + 2e - + 2H + -> N 2 O (g) + H 2 O [ Reaction Scheme 3]

2Fe (Ⅱ) EDTA-NO ( aq) + 4e - + 4H + -> N 2 (g) + 2H 2 O [ Reaction Scheme 4]

Fe (Ⅱ) EDTA-NO ( aq) + 3e - + 3H 2 O -> NH 2 OH (g) + 3OH - [ Scheme 5]

Fe (Ⅱ) EDTA-NO ( aq) + 5e - + 5H 2 O -> NH 4 + (aq) + 6OH - [ Scheme 6]

*First, Fe(III)EDTA, which is oxidized by exposure to oxygen, can be reduced to Fe(II)EDTA, which is a form that can selectively absorb nitrogen monoxide by receiving electrons at the cathode (Scheme 2), each with 1 electron , 2 electron, 3 electron and 5 electron reactions can be converted to nitrous oxide (reaction scheme 3), nitrogen (reaction scheme 4), hydroxylamine (reaction scheme 5) and ammonia (reaction scheme 6).

On the other hand, under the overvoltage condition above a certain potential difference, a hydrogen generation reaction (reaction scheme 7) occurs in competition with the reduction reaction of nitrogen monoxide provided in the present invention, which is the current efficiency (Faraday) for the reduction reaction of nitrogen monoxide (reaction schemes 3 to 6). efficiency).

2H ⁺ + 2e ^-- > H ₂ (g) [Scheme 7]

In the present invention, the gaseous nitrogen monoxide supplied through the gas inlet 60 of FIG. 2 is adsorbed to an aqueous solution of ferrous-ethylenediaminetetraacetic acid (Fe(II)EDTA) of the electrolyte contained in the cathode cell 100 and is liquid Of Fe(II)EDTA-NO, and when a potential difference is applied by an external power source, water decomposition occurs at the anode electrode 70 to be converted into oxygen molecules, hydrogen ions and electrons, and the cathode electrode inside the cathode cell ( In the working electrode) 10, Fe(II)EDTA-NO is reduced and converted into various nitrogen compounds. At this time, the gaseous nitrogen compound is discharged through the gas outlet 50 to be analyzed by gas chromatography, and the nitrogen compound in the solution remaining inside the cathode cell is analyzed by ion chromatography through sampling after reaction and gaseous and liquid products It is possible to obtain the current efficiency for. The reaction can be carried out continuously rather than batchwise, and the hydrogen gas produced by the side reaction is discharged together with the gaseous nitrogen compound and can be separated/captured if necessary.

The electrolysis system according to the present invention may be characterized in that it comprises a means for selectively converting ammonia (NH ₃ ) in nitrogen oxides, particularly nitrogen monoxide, using a specific electrode and a specific potential condition. The term “selectivity” means that the current efficiency for conversion to ammonia is 95% or more experimentally.

In the present invention, the concentration of the metal complex in the electrolyte is not particularly limited, but it may be considered to use 0.01 to 0.5 M. If the concentration of the metal complex is more than 0.01 M, the adsorption amount of the raw material is sufficient and suitable for industrial use. If the concentration is less than 0.5 M, it is precipitated in the form of iron oxide without forming a metal complex and contaminates the electrode and electrolyte. It can be prevented from being attached to the reactor wall.

* In addition, the present invention

Introducing nitrogen oxide into the electrochemical system;

Forming a complex between the introduced nitrogen oxide and the metal complex compound in the electrolyte; And

Performing an electrical reduction reaction on the formed complex;

It provides a method for producing ammonia from nitrogen oxide, characterized in that it comprises a.

Hereinafter, the manufacturing method of the present invention will be described in detail for each step.

The first step of the manufacturing method of the present invention is a step of introducing the nitrogen oxide as a raw material into the electrochemical system, wherein the nitrogen oxide may be nitrogen monoxide, for example, introduced into the electrochemical system through the supply of nitrogen oxide, It reacts with the metal complex in the electrolyte.

As described above, the nitrogen oxide introduced into the electrochemical system reacts with the metal complex compound in the electrolyte to form a complex. At this time, the concentration of the metal complex compound in the electrolyte may be adjusted in the range of 10 mM to 500 mM. If the concentration of the metal complex is more than 10mM, the amount of adsorption of the raw material is sufficient and suitable for industrial use. If the concentration is 500 mM or less, it is precipitated in the form of iron oxide without forming a metal complex and contaminates the electrode and electrolyte or the reactor It can be prevented from being attached to the wall surface.

The pH of the electrolyte used in the production method of the present invention may use a neutral range of 6 to 8. Adjusting the pH of the electrolyte may be necessary for the selectivity of ammonia, and considering the high selectivity of ammonia in neutral conditions, the pH range can be adjusted to the above range.

The manufacturing method of the present invention includes the step of performing an electrical reduction reaction on the formed complex after the complex is formed, through which nitrogen oxide is electrochemically reduced in the complex state to form ammonia.

On the other hand, when the material of the cathode electrode used in the present invention is silver or copper, the potential difference applied to the system is in the range of 0.2Volt to -0.4Volt compared to the hydrogen reference electrode, and the potential difference applied in the case of free carbon is -0.3Volt to In the range of -0.4 Volt, in the case of platinum, the potential difference applied may be in the range of 0.4 Volt to -0.4 Volt.

Although the system can be operated even at a potential difference greater than -0.4 Volt compared to the hydrogen reference electrode, it is possible to consider applying the potential difference in the above range in terms of selectivity of ammonia. In the electrochemical system according to the present invention, it is necessary to sufficiently reduce nitrogen oxides at the cathode, and at the same time, it is necessary to increase the selectivity for ammonia by suppressing the occurrence of side reactions. The potential difference applied together can be adjusted.

The manufacturing method of the present invention is a manufacturing method performed under normal temperature and normal pressure conditions. In the conventional ammonia production process, the reaction was performed under high temperature and high pressure conditions in order to increase the selectivity of ammonia, but the production method of the present invention has an advantage of obtaining excellent ammonia selectivity even at room temperature and normal pressure conditions.

In the production method of the present invention, as described above, the reduction reaction proceeds in a state where the raw material and the metal complex compound form a complex. As the raw material forms a complex with the metal complex compound, the amount of the raw material involved in the reduction reaction increases, thereby increasing productivity.

The system and manufacturing method according to the present invention have the advantage of being able to produce high value-added ammonia using nitrogen oxide, an air pollutant, in particular nitrogen monoxide, which accounts for about 95% of it, as a raw material. In particular, many of the air pollutants are nitrogen oxides and sulfur oxides. Sulfur oxides can be easily separated and removed, while nitrogen oxides are difficult to separate and remove easily. The present invention is characterized in that nitrogen oxides, which are difficult to remove, are used as raw materials. In addition, despite the process at room temperature and normal pressure, the invention is characterized in that it suppresses side reactions such as a hydrogen production reaction and has high selectivity for ammonia.

Hereinafter, the present invention will be described in more detail through experimental examples. These experimental examples are only for illustrating the present invention, it will be apparent to those skilled in the art that the scope of the present invention is not interpreted to be limited by these experimental examples.

<Experimental Example 1>

Determination of the applied voltage range for each cathode electrode (working electrode)

In the electrochemical system having the structure shown in FIG. 2, a phosphate buffer was used as an electrolyte, and Fe(II)EDTA having a concentration of 50 mM was included, and 99% of argon and 1% of nitrogen monoxide were included as a nitrogen oxide supply. The mixed gas included was injected at a flow rate of 20 mL/min. A platinum foil was used as the anode electrode (counter electrode), and a silver/silver chloride reference electrode was used as the reference electrode. As the cathode electrode (working electrode), platinum (Pt), free carbon (Glassy Carbon, GC), silver (Ag), and copper (Cu) were used, respectively. Linear Sweep Voltammetry was used in this environment. Was performed, and the results are shown in FIGS. 3A and 3B. After correcting the correct potential difference through IR compensation, it was converted to a general reference hydrogen electrode (RHE) and displayed on the X-axis.

According to FIGS. 3A and 3B, it can be seen that the platinum electrode has the lowest overvoltage at which current starts flowing, that is, the reduction reaction starts, and the glassy carbon electrode has the highest compared to other cathode electrodes. In addition, in the case of the silver and copper electrodes, it can be seen that the reaction starts under the overvoltage condition at the midpoint between the platinum and the free carbon electrode. In addition, in the case of the silver and copper cathode electrodes, it can be seen that an inflection point is drawn under an overvoltage condition of about-0.25 V compared to the hydrogen reference electrode. Through this, reactants around the cathode electrode (working electrode), that is, Fe(II)EDTA- It can be seen that the concentration of NO rapidly decreases, mass transfer limiting occurs, and the reduction current value decreases.

<Experimental Example 2>

Check the current efficiency of the product for each cathode electrode (working electrode)

After performing the time-to-current method (Chronoamperometry, CA) for the same electrochemical system as in Experimental Example 1, the current efficiency of the converted products was confirmed, and the results are shown in FIGS. 4A to 4D. Like the linear scanning potential method, the correct potential difference is corrected through IR compensation and then converted to a general reference hydrogen electrode (RHE) and displayed on the X axis. The overvoltage condition for each cathode electrode is based on the results obtained in the linear scanning potential method (FIG. 2) performed in Experimental Example 1, compared to a hydrogen reference electrode for a glassy carbon working electrode (cathode electrode) at 0.35 V- 0.55 V, -0.05 V to -0.35 V for platinum electrodes, and 0.15 V to -0.35 V for silver and copper working electrodes (cathode electrodes), respectively.

According to FIGS. 4A to 4D, it can be seen that most currents are used to convert nitrogen monoxide to ammonia at -0.35V and -0.40V in the case of the free carbon working electrode. It was confirmed that hydrogen production, a competitive reaction, was produced from -0.45V compared to the hydrogen reference electrode, and the higher the overvoltage, the higher the hydrogen production ratio compared to the entire product.

Second, in the case of the platinum working electrode, hydrogen generation reaction predominantly occurred under all overvoltage conditions performed by the time zone current method, which is a result of the high activity of the platinum electrode for hydrogen generation reaction.

In the case of silver and copper working electrodes, it can be seen that ammonia is predominantly produced under the overvoltage condition of -0.15V to -0.25V. On the other hand, it can be seen that the metal iron ion generation reaction due to the reduction of divalent iron ions in the copper working electrode occurred under the overvoltage conditions of -0.30V and -0.35V, but the corresponding reaction did not occur in the silver electrode.

<Experimental Example 3>

Check the conversion rate of nitrogen monoxide to ammonia

Using the same electrochemical system as in Experimental Example 1, the ammonia-partial current density was converted from the data of the time-zone current method, and the results are shown in FIG. 5. In other words, the results in FIG. 5 indicate the rate of conversion of nitrogen monoxide to ammonia. According to FIG. 5, it can be seen that when silver is used as the cathode electrode (working electrode), the conversion rate to ammonia is very fast. In addition, it can be confirmed that a certain amount of overvoltage condition for each electrode inhibits ammonia production by a side reaction of hydrogen production.

<Experimental Example 4>

Productivity comparison of ammonia from nitrogen oxides

In order to more accurately compare the conversion rate of FeEDTA-NO in the form of a complex to ammonia, pure nitrogen monoxide (99.9%) was supplied to the cell at a flow rate of 5 mL/min to conduct an experiment, and the results are shown in FIG. 6. Shown. In the case of reducing pure nitrogen monoxide, the ammonia-current density is about 1.9 mA/cm ² at -0.50 V based on the hydrogen electrode, whereas in the case of reduction of nitrogen monoxide fixed to the complex compound, the hydrogen electrode at a concentration of 50 mM and 100 mM Compared to the reference, it can be seen that even at a lower overvoltage condition of -0.35V, the current densities of 2mA/cm ² and 6mA/cm ² , respectively, show a clear advantage in terms of energy consumption and ammonia productivity. In the experiment of reduction of pure nitrogen monoxide, the current density of about 2mA/cm ² is an ideal condition without field applicability when considering the concentration of nitrogen monoxide supplied, 99.9%, and considering the actual emission concentration of 100~2000ppm, If nitrogen monoxide is reduced without a complex compound, it can be expected that the current density will be very low to 0.1 mA/cm ² or lower, resulting in denitrification efficiency and ammonia production rate.

10: cathode electrode (working electrode)
20: cathode current collector
30: outermost version
40: reference electrode
50: cathode gas outlet
60: nitrogen oxide supply
70: anode electrode (counter electrode)
80: anode gas outlet
90: separator
100: cathode chamber
110: anode chamber

Claims (12)

An electrochemical system for producing ammonia from nitrogen oxide, comprising a cathode electrode, an anode electrode, a reference electrode, an electrolyte including a metal complex, and a nitrogen oxide supply, in which a reduction reaction of the complex between the nitrogen oxide and the metal complex occurs.
The electrochemical system according to claim 1, wherein the nitrogen oxide is nitrogen monoxide.
The electrochemical system according to claim 1, wherein the metal of the metal complex is iron or magnesium.
The complex of claim 1, wherein the complex compound is one salt selected from the group consisting of ethylenediamine tetraacetic acid (EDTA), 1,2 cyclohexanediamine tetraacetic acid (CyDTA), and sodium nitro triacetic acid (NTA). Electrochemical system characterized by.
According to claim 1, The material of the cathode electrode or anode electrode is selected from the group consisting of iron, glassy carbon (Glassy Carbon, GC), aluminum, copper, silver, nickel, platinum, oxides thereof, and alloys thereof Electrochemical system, characterized in that at least one.
The potential difference applied when the material of the cathode electrode is silver or copper is in the range of 0.2Volt to -0.4Volt compared to the hydrogen reference electrode, and the potential difference applied in the case of free carbon is -0.3Volt to -0.4. The range of Volt, and in the case of platinum, the potential difference applied is in the range of 0.4Volt to -0.4Volt. The electrochemical system according to claim 1, wherein the pH of the electrolyte is maintained in a range of 6 to 8.
Introducing nitrogen oxide into the electrochemical system;
Forming a complex between the introduced nitrogen oxide and the metal complex compound in the electrolyte; And
Performing an electrical reduction reaction on the formed complex;
Method for producing ammonia from nitrogen oxide, characterized in that it comprises a.
10. The method of claim 8, wherein the nitrogen oxide is nitrogen monoxide.
The method of claim 8, wherein the concentration of the metal complex is 10 mM to 500 mM.
The potential difference applied when the material of the cathode electrode is silver or copper, is in the range of 0.2Volt to -0.4Volt compared to the hydrogen reference electrode, and the potential difference applied in the case of free carbon is -0.3Volt to -0.4. The range of Volt, and in the case of platinum, the potential difference applied is in the range of 0.4Volt to -0.4Volt.
9. The method of claim 8, wherein the pH of the electrolyte contained in the electrochemical system is maintained in the range of 6 to 8 during the electroreduction reaction.

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