KR20240174291A - Synthesis of methanol for power generation and fuel cell integrated system - Google Patents

Abstract

The integrated methanol production and fuel cell system for power generation of the present invention includes a methanol production unit that converts carbon dioxide into methanol, and a direct methanol fuel cell unit that produces electricity through an oxidation reaction of methanol extracted from the methanol production unit. Methanol produced in the methanol production unit is used in the direct methanol fuel cell unit, and carbon dioxide provided to the methanol production unit uses carbon dioxide formed in the electricity production reaction of the direct methanol fuel cell unit, so that the carbon dioxide emitted can be reduced to zero, resulting in a carbon-neutral power generation system.

Description

{SYNTHESIS OF METHANOL FOR POWER GENERATION AND FUEL CELL INTEGRATED SYSTEM}

The present invention relates to a methanol production and fuel cell integration system for power generation, which produces methanol, extracts the produced methanol, and supplies it directly to a methanol fuel cell system to generate power.

In accordance with the government's declaration of carbon neutrality, the goal is to phase out coal-fired power generation by 2050 and gradually reduce carbon dioxide emissions to achieve a reduction of more than 40% by 2030 compared to 2018. In line with this trend, the power generation industry is establishing and implementing plans for fuel cell power generation to reduce greenhouse gases emitted. Accordingly, various types of fuel cell power generation are currently receiving attention and undergoing research and development. Currently, fuel cells can be classified into polymer electrolyte membrane fuel cells (PEMFC), solid oxide fuel cells (SOFC), alkaline fuel cells (AFC), molten carbonate fuel cells (MCFC), phosphoric acid fuel cells (PAFC), and direct methanol fuel cells (DMFC) depending on the type of electrolyte. In particular, methanol fuel cells have the advantage of being able to produce electricity with high output at low temperatures. The reaction formula of a direct methanol fuel cell (DMFC) is as shown in Table 1 below.

division Chemical reaction formula electric potential Reaction number Anode CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ^- E° = 0.046 V (1) Cathode 1.5O ₂ + 6H+ + 6e- → 3H ₂ O E° = 1.23 V (2) Overall reaction
(Overall reaction) CH ₃ OH + H ₂ O +1.5O ₂ → CO ₂ + 3H ₂ O E° = 1.18 V (3)

In the case of direct methanol fuel cells (DMFC), as shown in the above reaction formula (1), there is a disadvantage in that carbon dioxide is generated. Of course, the amount of carbon dioxide generated is smaller than that of coal-fired power generation, but carbon dioxide emissions must be suppressed in order to achieve carbon neutrality. In addition, in the case of direct methanol fuel cells, carbon dioxide is generated through the Fischer-Tropsch reaction as shown in Table 2 below. Table 2 shows the reaction formula for methanol generation through Fischer-Tropsch.

division Chemical reaction formula heat of reaction Reaction number Overall reaction
(Overall reaction) CO + 2H ₂ → CH ₃ OH △H° ₂₉₈ = -94.5kJ (4)

In the case of the methanol production reaction through Fischer-Tropsch in reaction formula (4), the process is carried out at a high temperature of 800 degrees or higher, and a lot of energy is consumed accordingly. In addition, there is a disadvantage in that hydrogen (H ₂ ), which is a clean raw material, must be used.

That is, in the case of direct methanol fuel cells, clean energy source hydrogen and high energy required for the reaction are required to produce the raw material methanol, and there is a problem that carbon dioxide is generated through the fuel cell reaction.

There is another technology for producing methanol today. There is a process for producing methanol at a relatively low temperature of about 300℃ using methane and oxygen. This process has the advantage of lower energy consumption than the Fischer-Tropsch process and does not use hydrogen, which is a clean energy source. However, the efficiency of this reaction is very low, and there is also the problem of carbon dioxide being generated and emitted.

Korean Patent No. 10-1571850

In order to solve the above problems, the purpose of the present invention is to provide a system in which a methanol production function and a fuel cell are integrated to increase reaction efficiency and minimize carbon dioxide emissions, and which integrates a system for producing methanol by converting carbon dioxide into methanol and a direct methanol fuel cell that directly uses the produced methanol to produce electricity, thereby providing an integrated methanol production and fuel cell system for power generation.

The integrated methanol production and fuel cell system for power generation of the present invention may include a methanol production unit that converts carbon dioxide into methanol, and a direct methanol fuel cell unit that produces electricity through an oxidation reaction of methanol extracted from the methanol production unit.

In the integrated system for methanol production and fuel cell for power generation of the present invention, carbon dioxide provided to the methanol production unit can use carbon dioxide formed in the electricity production reaction of the direct methanol fuel cell unit.

In the integrated system for producing methanol for power generation and fuel cell of the present invention, the methanol production unit may include a reduction electrode having a first catalyst layer capable of receiving carbon dioxide and converting it into methanol to produce methanol, an oxidation electrode having a second catalyst layer that receives hydroxide ions (OH ^- ) generated at the reduction electrode and generates oxygen, and an electrolyte in which an electrolyte composition and an electrolyte membrane are formed so as to be electrically connected between the reduction electrode and the oxidation electrode.

Methanol produced at the reduction electrode of the above methanol production unit can be extracted and supplied to the direct methanol fuel cell unit.

The catalyst component constituting the first catalyst layer in the above methanol production unit may be any one selected from copper, zinc oxide, and aluminum oxide, or a mixture of two or more thereof.

The catalyst component constituting the second catalyst in the above methanol production unit may be any one selected from iridium (Ir), cobalt, copper, iron, platinum, nickel, rhodium, and ruthenium, or a mixture of two or more thereof.

In the integrated system for methanol production and fuel cell for power generation of the invention, the direct methanol fuel cell unit may include an oxidation electrode having a fourth catalyst layer that generates electricity by oxidizing methanol supplied from the methanol production unit, a reduction electrode having a third catalyst layer that receives hydrogen ions (H ⁺ ) generated at the oxidation electrode and reacts with oxygen to generate water, and an electrolyte positioned between the reduction electrode and the oxidation electrode and having an electrolyte membrane formed therein.

Carbon dioxide generated through methanol oxidation reaction at the oxidation electrode of the above direct methanol fuel cell unit can be supplied to the methanol production unit.

Water generated at the reduction electrode of the above direct methanol fuel cell unit can be discharged through a path formed on one side of the above direct methanol fuel cell unit.

The catalyst component constituting the fourth catalyst layer in the above direct methanol fuel cell unit may be any one selected from platinum (Pt), palladium (Pd), and ruthenium (Ru), or a mixture of two or more thereof.

The catalyst component constituting the third catalyst layer in the above direct methanol fuel cell unit may be any one selected from carbon, cobalt, copper, iridium, iron, nickel, palladium, platinum, rhodium, and ruthenium, or a mixture of two or more thereof.

The integrated methanol production and fuel cell system for power generation of the present invention is a carbon-neutral power generation system in which carbon dioxide generated during the power generation process in the methanol fuel cell section is directly used in the methanol production section, thereby realizing complete carbon neutrality with almost no carbon dioxide emissions. In addition, a large amount of energy used in methanol production is renewable energy, thereby achieving an eco-friendly power generation effect.

Figure 1 is a schematic diagram showing a general reaction of a methanol production and fuel cell integrated system for power generation according to the present invention.
Figure 2 is a schematic diagram showing the reaction occurring in the methanol production section of the integrated methanol production and fuel cell system for power generation of the present invention.
Figure 3 is a schematic diagram showing the reaction occurring directly in the methanol fuel cell unit in the integrated methanol production and fuel cell system for power generation of the present invention.

Hereinafter, a methanol production and fuel cell integrated system for power generation according to the present invention will be specifically described with reference to exemplary drawings.

Figure 1 is a schematic diagram showing a general reaction of a methanol production and fuel cell integrated system for power generation according to the present invention.

As illustrated in FIG. 1, the integrated methanol production and fuel cell system (300) for power generation is composed of a methanol production unit (100) and a direct methanol fuel cell unit (200). Methanol produced in the methanol production unit (100) moves to the methanol fuel cell unit (200) as indicated by the sky blue arrow, and carbon dioxide formed through the electricity production reaction of methanol in the methanol fuel cell unit (200) moves to the methanol production unit (100) and is recycled.

Both the above methanol production unit (100) and the direct methanol fuel cell unit (200) have a membrane-electrode assembly (MEA) structure.

The above methanol production unit (100) converts carbon dioxide into methanol to produce methanol, and the specific configuration and reaction of the methanol production unit (100) are shown in Figure 2.

As shown in Fig. 2, the methanol production unit (100) includes a reduction electrode (10), an oxidation electrode (20), and an electrolyte (30) between the reduction electrode (10) and the oxidation electrode (20).

In the above methanol production unit (100), methanol synthesis through carbon dioxide conversion is carried out through the reaction shown in Table 3 below.

division Chemical reaction formula electric potential Reaction number Anode 6OH ^- → 1.5O ₂ + 3H ₂ O + 6e ^- E° = -0.40 V (5) Cathode CO ₂ + 5H ₂ O + 6e ^- → CH ₃ OH + 6OH ^- E° = -0.81 V (6) Overall reaction
(Overall reaction) CO ₂ + 2H ₂ O → CH ₃ OH + 1.5O ₂ E° = -0.41 V (7)

The above reduction electrode (10) is equipped with a first catalyst layer (11) including a catalyst that can receive carbon dioxide (CO ₂ ) and convert it into methanol (CH ₃ OH).

The catalyst component constituting the first catalyst layer (11) may be any one selected from copper (Cu), zinc oxide (ZnO), and aluminum oxide (Al ₂ O ₃ ), or a mixture of two or more of these.

Carbon dioxide (CO ₂ ) supplied from the above reduction electrode (10) uses high-concentration carbon dioxide, but can also use carbon dioxide formed in the electricity production reaction of the direct methanol fuel cell unit (200).

The energy required to convert carbon dioxide into methanol is consumed at the above reduction electrode (10). At this time, the system is configured in an environmentally friendly manner by using the energy required to convert carbon dioxide by utilizing renewable energy rather than using external electric energy.

The above oxidation electrode (20) has a second catalyst layer (21) including a catalyst that receives hydroxide ions (OH ^- ) generated at the reduction electrode (10) through an electrolyte (30) and generates oxygen.

The catalyst component constituting the second catalyst layer (21) may use a metal catalyst such as iridium (Ir) so that an oxygen evolution reaction (OER) can be generated, and specifically, one selected from among iridium, cobalt, copper, iron, platinum, nickel, rhodium, and ruthenium, or a mixture of two or more of these may be used.

The first catalyst layer (11) and the second catalyst layer (21) formed on the reduction electrode (10) and oxidation electrode (20) respectively are manufactured using a catalyst coated diffusion layer (CCD) method to allow diffusion of gaseous reactants within the electrode structure.

The above CCD method mixes a catalyst, a solvent, and an ionomer as a binder to sufficiently disperse the catalyst. The dispersed solution is sprayed onto carbon paper, which is a gas diffusion medium, through a spray injection method to produce a gas diffusion electrode (CCD) on which each catalyst layer (11, 21) is formed.

Instead of the carbon paper, a conductive web may be metallic or carbon-based, made of a metal mesh, foam or cloth, made of a woven or non-woven carbon fabric, or other preferably porous or perforated ones.

The electrolyte (30) is formed by an electrolyte composition and an electrolyte membrane (31) that electrically connects the reduction electrode (10) and the oxidation electrode (20) and is positioned between the reduction electrode (10) and the oxidation electrode (20).

In the integrated system for producing methanol for power generation and fuel cell of the present invention, the electrolyte membrane is a membrane capable of exchanging ions, and may be a membrane, an ion exchange membrane, an ion transfer membrane, an ion conductive membrane, a separation membrane, an ion exchange separation membrane, an ion transfer separation membrane, an ion conductive separation membrane, an ion exchange electrolyte membrane, an ion transfer electrolyte membrane or an ion conductive electrolyte membrane.

For example, the electrolyte (30) may be configured with KHCO ₃ (aq) as an electrolyte composition and an anion exchange membrane as an electrolyte membrane, and the electrolyte (30) configured in this manner is performed by setting the process conditions for producing methanol well in the methanol production unit (100).

Methanol produced at the reduction electrode (10) of the above methanol production unit (100) moves to the electrolyte (30), and the methanol moved onto the electrolyte (30) is extracted and directly supplied to the methanol fuel cell unit (200).

The direct methanol fuel cell unit (200) is a fuel cell that produces electricity through an oxidation reaction of methanol extracted from the methanol production unit (100) using a direct methanol fuel cell (DMFC). The specific configuration and reaction of the methanol fuel cell unit (200) are shown in Fig. 3.

As illustrated in FIG. 3, the direct methanol fuel cell unit (200) also includes a reduction electrode (110), an oxidation electrode (120), and an electrolyte (130) between the reduction electrode (110) and the oxidation electrode (120).

The above oxidation electrode (120) is equipped with a fourth catalyst layer (121) that generates electricity by oxidizing methanol supplied from a methanol production unit (100).

Carbon dioxide is generated along with electricity generation through methanol oxidation reaction at the above oxidation electrode (120), and the generated carbon dioxide can be supplied to the methanol production unit (100).

The catalyst component constituting the fourth catalyst layer (121) may be one selected from platinum (Pt), palladium (Pd), and ruthenium (Ru), or a mixture of two or more thereof, as a catalyst capable of oxidizing methanol. Platinum (Pt) or ruthenium (Ru) is preferably used.

The above reduction electrode (110) is composed of a catalyst that allows a reduction reaction of hydrogen ions (proton ions), and has a third catalyst layer (111) that receives hydrogen ions (H ⁺ ) generated from the oxidation electrode (120) and reacts them with oxygen to produce water.

Water generated by the reduction reaction of hydrogen ions at the above reduction electrode (110) forms a path (not shown) on one side of the direct methanol fuel cell unit (200) and can be discharged through this path.

The catalyst component constituting the third catalyst layer (111) may be one selected from carbon, cobalt, copper, iridium, iron, nickel, palladium, platinum, rhodium, and ruthenium, or a mixture of two or more thereof. Platinum (Pt) is preferably used.

The third catalyst layer (111) and the fourth catalyst layer (121) are manufactured using the catalyst coated diffusion layer (CCD) method described above.

The electrolyte membrane (131) of the direct methanol fuel cell unit (200) is positioned between the reduction electrode (110) and the oxidation electrode (120), and is formed by an electrolyte composition and an electrolyte membrane (131) that electrically connect the reduction electrode (110) and the oxidation electrode (120).

For example, the electrolyte (130) can be configured with KHCO ₃ (aq) as an electrolyte composition and a proton exchange membrane as an electrolyte membrane, and the electrolyte (130) configured in this way is set to a condition that exhibits a high current density in a direct methanol fuel cell unit (200).

The overall chemical reaction formula according to the integrated system for producing methanol for power generation and fuel cell of the present invention is as shown in Table 4 below.

division Chemical reaction formula Reaction number Methanol production department CO ₂ + 2H ₂ O → CH ₃ OH + 1.5O ₂ (8) Direct methanol fuel cell unit CH ₃ OH + H ₂ O +1.5O ₂ → CO ₂ + 3H ₂ O (9) Carbon dioxide emissions (Net) 1 mole of _CO2 consumed (equation 8) - 1 mole of _CO2 produced (equation 9) = 0

As shown in Table 4 above, it can be seen that the amount of carbon dioxide emissions generated through the entire process of the integrated system for methanol production and fuel cell for power generation is 0 (zero).

As previously discussed, the integrated system for producing methanol for power generation and fuel cells realizes carbon neutrality by directly injecting liquid methanol produced in a methanol production unit (100) into a methanol fuel cell unit (200) and using the injected methanol to produce electricity using a direct methanol fuel cell (DMFC).

10: Reduction electrode
11: First catalyst layer
20: Oxidation electrode
21: Second catalyst layer
30 : Electrolyte
31: Electrolyte membrane
100 : Methanol production department
110 : Reduction electrode
111: Third catalyst layer
120 : Oxidation electrode
121: 4th catalyst layer
130 : Electrolyte
131 : Electrolyte membrane
200 : Direct methanol fuel cell unit
300: Integrated system for methanol production and fuel cell for power generation

Claims (10)

A methanol production unit that converts carbon dioxide into methanol; and
Includes a direct methanol fuel cell unit that produces electricity through an oxidation reaction of methanol extracted from the above methanol production unit;
An integrated system for producing methanol for power generation and fuel cell, characterized in that the carbon dioxide provided to the methanol production unit uses carbon dioxide formed in the electricity production reaction of the direct methanol fuel cell unit. In the first paragraph,
The above methanol production department,
A reduction electrode for producing methanol, comprising a first catalyst layer capable of converting carbon dioxide supplied into methanol;
An oxidation electrode having a second catalyst layer that receives hydroxide ions (OH ^- ) generated at the reduction electrode and generates oxygen; and
An integrated system for producing methanol for power generation and a fuel cell, characterized by including an electrolyte composition positioned between the reduction electrode and the oxidation electrode and electrically connected thereto, and an electrolyte in which an electrolyte membrane is formed. In the second paragraph,
An integrated system for producing methanol for power generation and a fuel cell, characterized in that methanol produced at the above reduction electrode is extracted and supplied to the direct methanol fuel cell unit. In the first paragraph,
An integrated system for producing methanol for power generation and a fuel cell, characterized in that the catalyst component constituting the first catalyst layer is one selected from copper (Cu), zinc oxide (ZnO), and aluminum oxide (Al ₂ O ₃ ) or a mixture of two or more thereof. In the second paragraph,
An integrated system for producing methanol for power generation and a fuel cell, characterized in that the catalyst component constituting the second catalyst layer is one selected from iridium (Ir), cobalt, copper, iron, platinum, nickel, rhodium, and ruthenium, or a mixture of two or more thereof. In the first paragraph,
The above direct methanol fuel cell unit,
An oxidation electrode having a fourth catalyst layer that generates electricity by oxidizing methanol supplied from the above methanol production unit;
A reduction electrode having a third catalyst layer that receives hydrogen ions (H ⁺ ) generated at the oxidation electrode and reacts them with oxygen to produce water; and
An integrated system for producing methanol for power generation and a fuel cell, characterized by including an electrolyte positioned between the reduction electrode and the oxidation electrode and having an electrolyte membrane formed therein. In Article 6,
An integrated system for producing methanol for power generation and a fuel cell, characterized in that carbon dioxide generated through a methanol oxidation reaction at the above-mentioned oxidation electrode is supplied to a methanol production unit. In Article 6,
An integrated system for producing methanol for power generation and a fuel cell, characterized in that the water produced at the above reduction electrode is discharged through a path formed on one side of the direct methanol fuel cell unit. In Article 6,
An integrated system for producing methanol for power generation and a fuel cell, characterized in that the catalyst component constituting the fourth catalyst layer is one selected from platinum (Pt), palladium (Pd), and ruthenium (Ru) or a mixture of two or more thereof. In Article 6,
An integrated system for producing methanol for power generation and a fuel cell, characterized in that the catalyst component constituting the third catalyst layer is one selected from carbon, cobalt, copper, iridium, iron, nickel, palladium, platinum, rhodium, and ruthenium, or a mixture of two or more thereof.