WO2025071312A1 - Passive catalytic hydrogen removal apparatus and hydrogen removal method using same - Google Patents

Abstract

The present invention relates to a passive catalytic hydrogen removal apparatus and a hydrogen removal method using same and, more specifically, to a passive catalytic hydrogen removal apparatus and a hydrogen removal method, wherein the hydrogen removal apparatus includes a composite catalyst including: a porous support including mesopores; and gold nanoparticles embedded in the pores of the porous support, and thus can effectively remove hydrogen being generated in a nuclear power generation facility by recombining the hydrogen with water at room temperature.

Description

Passive catalytic hydrogen removal device and hydrogen removal method using the same

The present invention relates to a passive catalytic hydrogen removal device and a hydrogen removal method using the same.

Nuclear power generation is gaining attention as an alternative energy source to fossil fuels. However, as large-scale nuclear power plant accidents occur, safety issues regarding nuclear power generation are emerging. The fundamental cause of these nuclear power plant accidents is an explosion caused by hydrogen enrichment during the fuel rod melting process. In order to prevent spontaneous combustion and explosion due to hydrogen enrichment, the hydrogen generated during the nuclear power generation process is combined with oxygen in the air to convert it into safe water, preventing hydrogen from being enriched.

However, conventional devices for preventing hydrogen enrichment, such as hydrogen igniters and thermal recombiners, require electricity, and thus have limitations in that they cannot operate when electricity is unavailable.

To solve these problems, a passive auto-catalytic recombiner (PAR) has been developed. A passive auto-catalytic recombiner is a device that passively recombines hydrogen existing in the gas phase with water without a separate power supply such as heat or electricity. PAR promotes the recombination of hydrogen and oxygen through a catalyst located at the bottom of the device, and at the same time, an upward current is formed due to the density difference caused by the exothermic reaction of the recombination, and the surrounding atmosphere moves due to the low pressure caused by the upward current, resulting in natural convection.

In such PAR, the most important factor that determines the hydrogen recombination performance and the PAR operating environment is the catalyst that recombines hydrogen with water. Conventionally, platinum or palladium was used as a PAR passive catalyst. However, since the oxidation initiation temperature of the PAR passive catalyst is relatively high, the PAR including such a conventional PAR passive catalyst does not sufficiently obtain the convection effect due to the reaction heat generated when hydrogen and oxygen are recombined at the beginning of operation, resulting in an initial operation delay problem. In addition, there is a disadvantage in that the durability and catalytic performance of the catalyst are reduced by the reaction heat, making it difficult to operate the PAR for a long time.

Accordingly, as disclosed in Korean Patent Publication No. 10-2020-0092046, a separate heating means (heating plate) was provided to solve the initial operation delay problem. However, there is a risk that a large amount of hydrogen and oxygen recombine simultaneously in the early stage of the reaction, causing a rapid temperature rise, which may act as a hydrogen explosion trigger.

According to one embodiment of the present invention, a passive catalytic hydrogen removal device capable of recombining hydrogen and oxygen even at room temperature is provided.

In addition, according to one embodiment of the present invention, a passive catalytic hydrogen removal device capable of preventing catalyst poisoning and maintaining the activity of the catalyst for a long period of time is provided.

In addition, according to one embodiment of the present invention, a hydrogen removal method capable of stably removing hydrogen generated in a nuclear reactor for a long period of time is provided.

A passive catalytic hydrogen removal device according to one embodiment of the present invention comprises: a main body forming an internal space connecting a gas inlet and a gas outlet; and a catalytic reaction unit positioned within the internal space and containing a composite catalyst for oxidizing and removing hydrogen in gas transferred to the internal space; wherein the composite catalyst comprises a porous support including mesopores and gold nanoparticles entrapped within the pores of the porous support.

In a passive catalytic hydrogen removal device according to one embodiment, the catalytic reaction section may include a honeycomb-structured support that defines the internal space and has a plurality of channels formed through which gas passes along a flow direction of the gas within the internal space, and a catalyst coating layer in which the composite catalyst is coated on the surface of the support.

In a passive catalytic hydrogen removal device according to one embodiment, the internal space is partitioned into an upper internal space and a lower internal space by the catalytic reaction unit, and the gas can flow into the catalytic reaction unit through the lower internal space and flow out through the upper internal space.

In a passive catalytic hydrogen removal device according to one embodiment, the material of the support may be one or a combination of two or more selected from the group consisting of metal oxides, metalloid oxides, metal carbides, and metalloid carbides.

In a passive catalytic hydrogen removal device according to one embodiment, a radial distribution function obtained by Fourier transforming an EXAFS (Extended X-ray absorption fine structure) spectrum of the composite catalyst can satisfy the following Equation 1.

[Formula 1]

(DH2/DH1) < 0.3

In the above equation 1, DH1 is the height of the peak at the interatomic distance D1, DH2 is the height of the peak at the interatomic distance D2, and D1 and D2 satisfy equations 2 and 3 below, respectively.

[Formula 2]

0.8≤(D1/D3)≤0.95

[Formula 3]

0.6≤(D2/D3)≤0.7

In the above equations 2 and 3, D3 represents the interatomic distance of the bulk Au-Au bond existing at 2.8 to 3.0 Å.

In a passive catalytic hydrogen removal device according to one embodiment, the composite catalyst can satisfy the following equation 4.

[Formula 4]

(DA2/DA1) < 0.25

In the above equation 4, DA1 is the area of the peak at the interatomic distance D1, DA2 is the area of the peak at the interatomic distance D2, and D1 and D2 satisfy the above equations 2 and 3, respectively.

In a passive catalytic hydrogen removal device according to one embodiment, (DH2/DH1) in the above formula 1 may be 0.25 or less.

In a passive catalytic hydrogen removal device according to one embodiment, (DA2/DA1) in the above formula 4 may be 0.18 or less.

In a passive catalytic hydrogen removal device according to one embodiment, the EXAFS (Extended X-ray absorption fine structure) spectrum may have a bimodal peak in the interatomic distance range of 2.2 to 3.0 Å of a radial distribution function obtained by Fourier transforming the spectrum.

In a passive catalytic hydrogen removal device according to one embodiment, the porous support may be a metal oxide or metalloid oxide porous support.

In a passive catalytic hydrogen removal device according to one embodiment, the diameter of the nanoparticles may be 1 to 20 nm.

In a passive catalytic hydrogen removal device according to one embodiment, the nanoparticles may be incorporated into some of the mesopores of the porous support, and the mesopores in which the nanoparticles are not incorporated may be interconnected as open pores.

In a passive catalytic hydrogen removal device according to one embodiment, the hydrogen is generated in a nuclear reactor, and the device further includes a fixing member positioned on one surface of an outer side of the main body and fixing the main body to an inner wall of a containment vessel of the nuclear reactor; the gas inlet is positioned at a lower end of the main body, the gas outlet is positioned on an upper portion of an outer surface of the main body opposite to the outer surface of the main body where the fixing member is positioned, and the upper surface of the main body may be inclined downward from the gas outlet toward the fixing member.

A method for removing hydrogen in a nuclear reactor according to one embodiment of the present invention may include a step of supplying gas containing hydrogen generated in a nuclear reactor to a passive catalytic hydrogen removal device according to any one of claims 1 to 16 installed in a nuclear reactor containment vessel.

In a method for removing hydrogen from a reactor according to one embodiment, the supply can be performed by natural convection of the gas.

A passive catalytic hydrogen removal device according to one embodiment of the present invention can prevent the problem of initial operation delay by recombining hydrogen and oxygen even at room temperature.

In addition, a passive catalytic hydrogen removal device according to one embodiment of the present invention can prevent catalyst poisoning and maintain the activity of the catalyst for a long period of time.

In addition, a hydrogen removal method according to one embodiment of the present invention can stably remove hydrogen generated in a nuclear reactor for a long period of time.

Figure 1 is an exploded perspective view of a passive catalytic hydrogen removal device according to one embodiment of the present invention.

Figure 2 is a perspective view showing a passive catalytic hydrogen removal device according to one embodiment of the present invention installed in a nuclear reactor.

FIG. 3 illustrates a radial distribution function obtained by Fourier transforming an EXAFS (Extended X-ray absorption fine structure) spectrum of a composite catalyst according to one embodiment of the present invention.

Unless otherwise defined, technical and scientific terms used in this specification have the meaning commonly understood by a person of ordinary skill in the art to which this invention belongs, and descriptions of well-known functions and configurations that may unnecessarily obscure the gist of the present invention are omitted in the following description and accompanying drawings.

Additionally, the singular forms used herein are intended to include the plural forms as well, unless the context specifically indicates otherwise.

In addition, units used in this specification without special mention are based on weight, and for example, units of % or ratio mean mass% or mass ratio, and mass% means the mass% that one component of the entire composition occupies in the composition unless otherwise defined.

In addition, the numerical range used in this specification includes the lower limit and the upper limit and all values within that range, the increments logically derived from the shape and width of the defined range, all double-defined values, and all possible combinations of the upper and lower limits of the numerical range defined in different shapes. Unless otherwise specifically defined in the specification of the present invention, values outside the numerical range that may occur due to experimental error or rounding of values are also included in the defined numerical range.

The term "comprises," as used herein, is an open-ended description equivalent to the expressions "comprises," "contains," "has," or "characterized by," and does not exclude additional elements, materials, or processes not listed herein.

The term average particle size (diameter) in this specification may mean a volume-based median diameter ( _D50 ) calculated by a laser diffraction method. The volume-based _D50 means the particle diameter at a point where the cumulative volume % is 50 volume % in a distribution curve (cumulative distribution curve) accumulated in order of particle diameters. Experimentally, a cumulative distribution curve including _D50 can be obtained by a conventional particle size analyzer using a laser diffraction method or a dynamic light scattering method.

Conventionally, a passive auto-catalytic recombiner (PAR) includes a platinum or palladium catalyst having a relatively high oxidation initiation temperature as a passive catalyst. Therefore, the convection effect due to the reaction heat generated when hydrogen and oxygen are recombined is not sufficiently obtained in the early stage of operation, which causes an initial operation delay problem. In addition, the durability and catalytic performance of the catalyst are reduced by the reaction heat, making it difficult to maintain the hydrogen removal performance for a long time. Furthermore, catalyst poisoning, in which the surface of the catalyst is contaminated by various contaminants (organic vapors, dust) in the reactor, may occur, which may significantly reduce the operating efficiency of the passive catalytic hydrogen recombiner.

The passive catalytic hydrogen removal device according to the present invention is intended to solve the above-described problems, and can prevent the problem of initial operation delay by smoothly recombining hydrogen and oxygen even at the early stage of reaction due to the relatively low oxidation initiation temperature. In addition, since the catalytic activity of the catalyst in the passive catalytic hydrogen removal device is maintained even at high reaction heat, hydrogen can be removed with high efficiency even during long-term operation. In addition, since catalyst poisoning by various contaminants in the reactor is prevented, the operating efficiency and operating life can be increased.

A passive catalytic hydrogen removal device according to one embodiment of the present invention comprises: a main body forming an internal space connecting a gas inlet and a gas outlet; and a catalytic reaction unit positioned within the internal space and containing a composite catalyst for oxidizing and removing hydrogen in gas transferred to the internal space; wherein the composite catalyst comprises a porous support including mesopores and gold nanoparticles entrapped within the pores of the porous support.

The above gas may refer to a gaseous substance generated inside a nuclear reactor. Specifically, the gas may be any one gas selected from steam, oxygen (O ₂ ), nitrogen (N ₂ ), iodine (I ₂ ), hydrogen (H ₂ ), carbon dioxide (CO ₂ ), carbon monoxide (CO), and methane (CH ₄ ), or a mixture of two or more gases. In addition, the gas may further include an inert gas generated in a nuclear fission process, such as xenon and krypton, or may further include a radioactive substance, such as cesium and strontium, when the radioactive substance exists in a gaseous state.

FIGS. 1 and 2 illustrate drawings of a passive catalytic hydrogen removal device according to one embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to the drawings, but is not limited thereto. In order to facilitate the description of the invention, as shown in FIGS. 1 and 2, one surface of the main body in contact with the inner wall of the reactor is referred to as the rear surface of the main body, and one surface of the main body opposite thereto is referred to as the front surface, and the height relative to the ground is referred to as the upper direction and the lower direction.

Referring to FIG. 1, a passive catalytic hydrogen removal device according to one embodiment of the present invention includes a main body and a catalytic reaction unit.

A passive catalytic hydrogen removal device of this type can be installed in a closed system, particularly, a reactor containment vessel, to remove hydrogen in the gas. The passive catalytic hydrogen removal device converts hydrogen in the gas into water (or water vapor) by combining it with oxygen through a composite catalyst, thereby smoothly initiating an oxidation reaction of hydrogen even in a generally operating reactor environment, that is, a water environment of room temperature (25±5°C) and a relative humidity of 95% or higher, thereby preventing an initial operation delay.

In one embodiment, the passive catalytic hydrogen removal device may have a size that allows natural convection to be smoothly formed and maintained within the reactor. The size of the passive catalytic hydrogen removal device may vary depending on the size of the installed reactor, but considering the generally used reactor size, the size of the passive catalytic hydrogen removal device (100) in the present invention may be 0.5 to 2 m based on the length (L) in the gas flow direction (up and down direction).

The above body is not particularly limited as long as it has a structure in which a gas inlet port through which the gas flows in, an internal space capable of receiving the gas flowing in through the gas inlet port, and a gas outlet port through which the gas passing through the internal space flows out.

The above body may have a macroscopically rectangular shape as illustrated in FIGS. 1 and 2, but is not limited thereto, and is not particularly limited as long as it has a shape that can be installed inside a reactor, particularly on the inner wall of a reactor containment vessel.

The above gas inlet is formed at the lower part of the main body so that gas can be naturally introduced through the stack effect of the gas, and the gas outlet can be located at the upper side of the main body. The gas outlet and the gas outlet are provided with separate mesh members to prevent foreign substances from being introduced into the internal space of the main body. The mesh member can use a metal mesh net to prevent the introduction of foreign substances and reinforce the strength of the overall device, and the mesh size can be appropriately selected considering the size of foreign substances generated within the reactor.

In one embodiment, as described above, the passive catalytic hydrogen removal device is installed in the reactor containment vessel, and the gas is generated in the reactor. At this time, the passive catalytic hydrogen removal device may further include a fixing member located on one surface of the outer side of the main body and fixing the main body to the inner wall of the containment vessel of the reactor. The fixing member is not particularly limited as long as it is known as a connecting member such as a conventional anchor bolt. As a non-limiting example, the fixing member may include a connecting plate located on one surface of the outer side of the main body and having a plurality of screw holes formed therein, and an embedded anchor bolt that is screw-connected with the screw holes and is embedded and fixed in the inner wall of the reactor containment vessel.

At this time, the gas inlet may be located at the lower end of the main body, and the gas outlet may be located at the upper portion of the outer surface of the main body opposing the outer surface of the main body (the rear surface of the main body) where the fixing portion is located, that is, the front surface of the main body, and the upper surface of the main body may be closed in a curved shape but may be inclined downward from the gas outlet toward the fixing portion. Such a passive catalytic hydrogen removal device can prevent impurities such as dust and organic vapor generated inside the reactor from flowing down to the rear surface of the main body along the upper surface, thereby flowing into the inside of the main body through the gas outlet located at the front surface of the main body. Accordingly, the reduction in the lifespan of the hydrogen removal device due to catalyst poisoning can be further prevented.

The above catalytic reaction section includes a composite catalyst, and is located in the internal space of the main body to oxidize and remove hydrogen in a gas flowing into the internal space. Specifically, the catalytic reaction section includes a honeycomb-structured support body that divides the internal space of the main body into upper and lower portions and has a plurality of channels formed through which the gas passes along the flow direction of the gas in the internal space, and a catalyst coating layer in which the composite catalyst is coated on the surface of the support body.

At this time, the internal space is partitioned into an upper internal space and a lower internal space by the catalytic reaction unit, and the gas flows into the catalytic reaction unit through the lower internal space, and the gas from which hydrogen has been removed passes through a channel in the catalytic reaction unit and flows out into the upper internal space, and can flow out to the outside of the hydrogen removal device, that is, into the reactor, through the gas outlet. Specifically, as illustrated in Fig. 2, gas flows in through a gas inlet located on the lower bottom surface of the main body, and the introduced gas passes through the catalytic reaction unit and hydrogen is removed. The gas from which hydrogen has been removed is discharged through a gas outlet formed on the upper front side of the main body.

A plurality of such catalytic reaction units may be provided spaced apart and arranged along the height direction of the main body.

The support of the above honeycomb structure is a structure having a plurality of channels, and the channels are extended in the upper and lower directions of the main body so that gas can flow smoothly, but are shaped so that both ends are open. The cross-section of the channel perpendicular to the direction of extension may be square as shown in the drawing, or, alternatively, circular, or polygonal such as a triangle, pentagon, or hexagon, and the shape is not limited.

The support of the above honeycomb structure may be one or more selected from the group consisting of metal oxides, metalloid oxides, metal carbides, and metalloid carbides. Specific examples thereof include, but are not limited to, alumina, silica, and silicon carbide.

The size of the cells formed by the support of the above honeycomb structure is not particularly limited as long as the gas can flow smoothly. As a non-limiting example, the number of cells per unit size of the support of the above honeycomb structure may be 20 to 900cspi, 50 to 600cspi, or 100 to 400cspi. In the above range, the flow of gas is smooth, while the contact area between the composite catalyst and the gas is maximized, thereby increasing the catalytic efficiency.

As shown in the drawing, the catalytic reaction unit can be detachably installed on the main body. Specifically, the catalytic reaction unit can be detachably installed by slidingly connecting to the lower part of the main body. Alternatively, it can be detachably fixed by a separate connecting member, such as a separate connecting screw.

The above complex catalyst can remove hydrogen by oxidizing hydrogen as described above, that is, by recombining hydrogen and oxygen. As described above, the conventional hydrogen removal catalyst has a relatively high hydrogen oxidation initiation temperature, so that the operation of the hydrogen removal device is delayed in the early stage of the reaction. However, the complex catalyst according to the present invention can prevent the initial operation delay phenomenon by smoothly oxidizing hydrogen even at room temperature and high relative humidity. In addition, it has excellent thermal stability, so that the durability can be prevented from being lowered due to the accumulation of reaction heat generated by the hydrogen oxidation reaction, thereby preventing the catalytic performance from being lowered. Specifically, the catalytic reaction section can remove substantially all hydrogen under the conditions of a space velocity of 100,000/hr, a feed of 1 vol% hydrogen, 21 vol% oxygen, and a residual inert gas, room temperature (25±5°C), and a relative humidity of 100%.

Specifically, the composite catalyst comprises a porous support and gold nanoparticles encapsulated within the porous support.

The above complex catalyst may have an average particle size of 0.01 ㎛ to 10 ㎛, specifically 0.05 ㎛ to 5 ㎛, and more specifically 0.1 ㎛ to 5 ㎛, but is not limited thereto.

In one embodiment of the present invention, the composite catalyst may have a specific surface area of 300 m2/g or more, 400 m2/g or more, 500 m2/g or more and 600 m2/g or more, 2,000 m2/g or less, or 1,500 m2/g or less, for example, but not limited to, 300 m2/g to 2,000 m2/g, 400 m2/g to 2,000 m2/g, or 600 m2/g to 1,500 m2/g. In addition, the composite catalyst may have a total pore volume of 0.08 cm3/g to 2.0 cm3/g, 0.08 cm3/g to 1.5 cm3/g, or 0.1 cm3/g to 1.0 cm3/g, but not limited thereto.

The above porous support may be a metal oxide or a metalloid oxide porous support. The metal or metalloid of the metal oxide or metalloid oxide may be a metal or metalloid of Group 2 to Group 5, Group 7 to Group 9, and Group 11 to Group 14, and specifically may be a metal or metalloid selected from Group 2 to Group 4, Group 13, and Group 14, and more specifically, may be Al, Ti, Zr, or Si.

The above porous support includes mesopores and may optionally further include micropores. The micropores and mesopores may mean those defined by the classification standardized by the IUPAC (International Union of Pure and Applied Chemistry). Specifically, micropores mean that the average diameter of the internal pores is less than 2 nm, and mesopores mean that the average diameter of the internal pores is 2 nm to 50 nm. The volume of the mesopores of the porous support may be 50% by volume or more, 60% by volume or more, or 70% by volume or more, and the upper limit is not limited, but may be, for example, 100% by volume or less, 95% by volume or less, or 90% by volume or less, or may be 50 to 100% by volume, specifically 60 to 90% by volume, but is not limited thereto. The above pore volume may mean that measured through BET surface area analysis equipment (Brunauer-Emmett-Teller Analysis).

According to a non-limiting embodiment, the porous support may have a hierarchical porous structure, and may include a structure in which micropores are regularly present and interconnected between mesopores. However, since the micropores are only an optional element, the porous support is not limited to a hierarchical porous structure.

According to a non-limiting embodiment, the porous support may further include macropores, and it may be preferable to include macropores at a certain volume fraction or more, thereby significantly reducing the diffusion resistance of the gas.

The above gold nanoparticles can be manufactured by a method known in the art or can use commercially available materials. Specifically, the gold nanoparticles can be manufactured by reducing a gold precursor present in a solution to gold according to a known method (Natan et al., Anal. Chem. 67, 735 (1995)). Examples of the gold precursor include, but are not limited to, halides, nitrates, acetates, acetylacetonates, or ammonium salts containing gold. Specifically, the gold precursor can be, but is not limited to, HAuCl ₄ or HAuBr ₄ .

The average diameter of the above gold nanoparticles may be 1 to 20 nm, specifically 1 to 15 nm, more specifically 1 to 12 nm. A preferable average diameter of the gold nanoparticles may be 1 to 10 nm, more preferably 1 to 8 nm.

According to one embodiment, the average diameter of the nanoparticles may be larger than the average diameter of the mesopores of the porous support. Accordingly, a deformation of the crystal lattice of the gold nanoparticles incorporated within the mesopores of the porous support may be generated, thereby inducing an improvement in catalytic activity in the room temperature range.

According to one embodiment, the gold nanoparticles may be incorporated into all or part of the mesopores of the porous support, and according to a preferred embodiment, the gold nanoparticles may be incorporated into part of the mesopores of the porous support. More specifically, the nanoparticles may be irregularly incorporated into part of the mesopores of the porous support.

At this time, the structure incorporated into all of the mesopores of the porous support means a superlattice structure, and specifically, means a highly ordered superlattice structure having face-centered cubic (FCC) symmetry. The form in which gold nanoparticles are irregularly incorporated into some of the mesopores means that the gold nanoparticles are incorporated into some of the mesopores of the porous support in a random form, and has the advantage of allowing gas diffusion to occur more effectively than the superlattice structure.

According to one embodiment, the nanoparticles may be incorporated into a portion of the mesopores of the porous support, and the mesopores in which the nanoparticles are not incorporated may be interconnected as open pores. Since the catalyst structure has the nanoparticles incorporated only into a portion of the pores of the porous support, gas diffusion may be more effectively achieved through the pores in which the nanoparticles are not incorporated and which are interconnected as open pores. Accordingly, even if the gas is supplied at a high flow rate at room temperature, substantially all of the hydrogen contained in the gas can be rapidly removed.

According to one embodiment, a radial distribution function obtained by Fourier transforming an EXAFS (Extended X-ray absorption fine structure) spectrum of the composite catalyst may satisfy the following Equation 1.

[Formula 1]

(DH2/DH1) < 0.3

In the above Equation 1, DH1 is the height of the peak at the interatomic distance D1, DH2 is the height of the peak at the interatomic distance D2, and D1 and D2 satisfy Equations 2 and 3 below, respectively. Specifically, D1 and D2 are the interatomic distances of the maximum peak found in the range satisfying Equations 2 and 3 below, respectively.

[Formula 2]

0.8≤(D1/D3)≤0.95

[Formula 3]

0.6≤(D2/D3)≤0.7

In the above equations 2 and 3, D3 refers to the interatomic distance of the bulk Au-Au bond existing at 2.8 to 3.0 Å, specifically, it may exist at 2.88 to 2.98 Å, and more specifically, it may refer to the standard interatomic distance of 2.90 Å. Specifically, D3 may refer to the interatomic distance of the bulk Au-Au bond existing at 2.8 to 3.0 Å, obtained through peak deconvolution when the peak appears as one peak with asymmetry or has a bimodal peak. The asymmetry means that although the peak has the shape of one peak (unimodal peak), the left and right sides have asymmetry with respect to the center of the peak as two peaks overlap.

Specifically, (D1/D3) of the above formula 2 may be 0.85 to 0.92, and (D2/D3) of the above formula 3 may be 0.63 to 0.66.

According to a specific implementation example, in the above formula 1, DH1 may refer to the height of a peak having an interatomic distance of 2.57±0.2Å, and DH2 may refer to the height of a peak having an interatomic distance of 1.85±0.2Å. Specifically, DH1 may refer to the height of a peak having an interatomic distance of 2.57±0.1Å, and DH2 may refer to the height of a peak having an interatomic distance of 1.85±0.1Å.

Since the above complex catalyst satisfies the condition that the height ratio of the peak at the interatomic distance D1 and the peak at the interatomic distance D2 is less than 0.3, the catalytic activity can be significantly improved.

EXAFS stands for extended X-ray absorption fine structure, and it can analyze the radial distribution or coordination number of gold nanoparticles. For example, when high-energy X-rays are irradiated on gold atoms, the gold atoms contained in the gold nanoparticles emit electrons. Accordingly, a radial scattered wave is generated centered on the gold atoms that absorbed the X-rays, and when the electrons emitted from the gold atoms that absorbed the X-rays reach other adjacent atoms (gold or oxygen atoms), electrons are emitted from the other adjacent atoms. At this time, a radial scattered wave is generated centered on the other adjacent atoms.

The scattered waves generated around the gold atom absorbing the X-ray and the scattered waves generated around the adjacent other atoms (gold or oxygen atoms) interfere. At this time, a standing wave is obtained according to the distance between the gold atom absorbing the X-ray and the other atom (gold or oxygen atom) adjacent to the gold atom. When the standing wave is Fourier transformed, a radius distribution having a peak according to the distance between the gold atom and the other atom (gold or oxygen atom) adjacent to the gold atom is obtained. That is, in addition to the peak according to the distance between gold (Au) atoms, a radius distribution having a peak according to the distance between gold (Au) atoms and oxygen atoms having an Au-O bond when the gold (Au) atom has a bond with an oxygen atom can be obtained.

According to one embodiment, (DH2/DH1) of the above formula 1 may be 0.25 or less, more specifically 0.24 or less, 0.2 or less, 0.15 or less, 0.1 or less, or 0.05 or less, and may be, but is not limited to, 0 or more. By having the above numerical range, the catalytic activity of the composite catalyst is significantly improved, which is preferable in that substantially all of the hydrogen contained in the gas can be removed even in a gas stream having a high flow rate.

According to one embodiment, the composite catalyst may have a radial distribution function obtained by Fourier transforming an EXAFS (Extended X-ray absorption fine structure) spectrum satisfying the following Equation 4.

[Formula 4]

(DA2/DA1) < 0.25

In the above equation 4, DA1 is the area of the peak at the interatomic distance D1, DA2 is the area of the peak at the interatomic distance D2, and D1 and D2 satisfy the above equations 2 and 3, respectively.

According to a specific implementation example, in the above formula 4, DA1 may refer to the area of a peak having an interatomic distance of 2.57±0.2Å, and DA2 may refer to the area of a peak having an interatomic distance of 1.85±0.2Å. Specifically, DA1 may refer to the area of a peak having an interatomic distance of 2.57±0.1Å, and DA2 may refer to the area of a peak having an interatomic distance of 1.85±0.1Å.

Since the above complex catalyst satisfies the area ratio of the peak at the interatomic distance D1 and the area ratio at the interatomic distance D2 being less than 0.25, the catalytic activity can be significantly improved.

According to one embodiment, (DA2/DA1) of the above formula 4 may be 0.2 or less, specifically 0.18 or less or 0.15 or less, more specifically 0.1 or less or 0.05 or less, and may be non-limitingly 0 or more. In the above numerical range, the catalytic activity is significantly improved, so that the catalytic performance can be exhibited more stably at room temperature.

According to one embodiment, the EXAFS (Extended X-ray absorption fine structure) spectrum may have a bimodal peak in the interatomic distance range of 2.2 to 3.0 Å of a radial distribution function obtained by Fourier transforming, and the bimodal peak appears due to a gold (Au)-gold (Au) atomic bond. Specifically, the interatomic distance range of 2.2 to 3.0 Å may be a range in which a distance between gold (Au) atoms is located, and means a distribution of interatomic distances of Au-Au in a crystal lattice.

In the above interatomic distance range of 2.2 to 3.0 Å, typical gold nanoparticles can exhibit a single peak, and having a single peak means that the distance between gold (Au)-gold (Au) atoms is constant within the crystal lattice of the nanoparticles. However, having a bimodal peak may mean that different gold (Au)-gold (Au) interatomic distances exist within the crystal lattice, and although it has not been clearly identified, it is inferred that two different gold (Au)-gold (Au) interatomic distances are generated by deformation of the crystal lattice due to compressive stress. By having a bimodal peak in the above interatomic distance range of 2.2 to 3.0 Å, it can exhibit excellent catalytic activity even in a low-temperature region.

A method for removing hydrogen from a nuclear reactor according to one embodiment of the present invention comprises the step of supplying gas containing hydrogen generated in a nuclear reactor to the above-described passive catalytic hydrogen removal device installed in a nuclear reactor containment vessel. At this time, the supply is performed by natural convection of the gas and does not require a separate driving unit.

The above-described passive catalytic hydrogen removal device is identical to the above-described passive catalytic hydrogen removal device, and a detailed description thereof is omitted.

Specifically, the above hydrogen removal method may include a step in which gas is introduced into the gas inlet of the above-described passive catalytic hydrogen removal device by natural convection, and the introduced gas passes through the catalytic reaction unit and is discharged through the gas outlet unit. At this time, hydrogen contained in the gas may be converted into water in the catalytic reaction unit and removed. Since the above-described composite catalyst is the same as each embodiment described above, a detailed description thereof will be omitted.

Hereinafter, the present disclosure will be described in more detail using examples. However, the following examples are provided only to help understanding of the present disclosure, and the technical idea of the present disclosure is not limited to the following examples.

(Manufacturing Example 1)

[Step 1]: Preparation of polymer-functionalized gold nanoparticles

[Step 1-1]: Gold nanoparticles stabilized with oleylamine are synthesized according to the following procedure.

First, olein amine was selected as a stabilizer, and a solution composed of 60 ml of toluene, 60 ml of oleylamine, and 0.6 g of HAuCl·3H ₂ O was prepared by stirring at room temperature for 10 minutes. 6 mmol of Tetrabutylamine borane complex, 6 ml of toluene, and 6 ml of oleylamine were mixed by ultrasonic grinding and quickly added to the solution. Then, the solution was stirred at room temperature for 1 more hour, ethanol was added, and centrifugation was performed to precipitate gold nanoparticles. The gold nanoparticle precipitate was redispersed with toluene, and ethanol was added and centrifuged. The manufactured gold nanoparticles exhibited an average particle diameter of 4 nm, and the manufactured gold nanoparticles were dispersed in 100 ml of toluene as formed.

[Step 1-2]: The surface of gold nanoparticles is functionalized with thiolated PEG by the following method.

In the above step 1-1, the gold nanoparticles dispersed in toluene were diluted by additionally adding 100 ml of tetrahydrofuran, and a thiolated polymer was selected to functionalize the surface of the gold nanoparticles by binding the polymer to it, and 1 g of monofunctional polyethylene glycol (aSH-PEG, weight average molecular weight: 1 kDa) whose terminal was substituted with a thiol group was added. After stirring, hexane was added, and centrifugation was performed to precipitate gold nanoparticles (Au-PEG) functionalized with PEG. The Au-PEG obtained by precipitation was dried and dispersed in water.

[Step 2]: Preparation of porous silica encapsulated with PEG-functionalized gold nanoparticles

0.088 g of Au-PEG prepared in the above step 1-2 was mixed with 0.396 g of Pluronic F127 as an activator and uniformly dispersed in 10 ml of 1.6 M HCl aqueous solution, and 1.49 g of tetraethylorthosilicate (TEOS) was added to the dispersion. Then, the dispersion of the mixture was stirred for 15 minutes and maintained at room temperature for 40 hours without stirring to prepare a red precipitate. The red precipitate corresponds to the porous silica entrapping PEG-functionalized gold nanoparticles.

[Step 3]: Preparation of composite catalyst

The red precipitate produced in the previous step was washed with water and dried, and then calcined stepwise at 250°C for 3 hours, 400°C for 2 hours, and 500°C for 2 hours to remove PEG and Pluronic F127 polymers, thereby producing a composite catalyst 1, which is a porous silica with gold nanoparticles captured thereon.

(Manufacturing example 2)

A composite catalyst 2 was manufactured by performing the same steps as in [Step 1-1] of the above Manufacturing Example 1, except that the molar ratio of oleylamine and HAuCl·3H ₂ O was adjusted to manufacture gold nanoparticles having an average particle size of 10 nm.

(Manufacturing Example 3)

Composite catalyst 3 was manufactured by performing the same procedure as in [Step 2] of Manufacturing Example 1 above, except that it was performed as follows.

Specifically, for the production of porous alumina encapsulated with PEG-functionalized gold nanoparticles in Step 2, first, 0.15 g of PEG-functionalized gold nanoparticles (Au-PEG) and 0.675 g of Pluronic F127 were prepared, uniformly dispersed in a mixed solution of 0.8 mL of nitric acid (68%) and 40 mL of ethanol, and then 0.81 g of aluminum ethoxide was added to the dispersion. Then, the dispersion of the mixture was stirred for 3 hours, maintained at room temperature for 24 hours without stirring, and then dried at 60°C for 3 hours to produce a red solid. Thereafter, Step 3 of Example 1 was performed in the same manner to produce composite catalyst 3, which is porous alumina encapsulated with gold nanoparticles.

(Manufacturing Example 4)

A composite catalyst 4 was manufactured by performing the same procedure as in [Step 2] of Example 1 above, except that it was performed as follows.

Specifically, for the preparation of porous titania encapsulated with PEG-functionalized gold nanoparticles in Step 2, first, 0.10 g of PEG-functionalized gold nanoparticles (4-Au-PEG) and 0.44 g of Pluronic F127 were prepared, uniformly dispersed in a mixed solution of 0.68 ml of 37% hydrochloric acid and 17.05 ml of ethanol, and then 2.28 g of titanium tetraisopropoxide was added to the dispersion. Then, the dispersion of the mixture was stirred for 3 hours, maintained at room temperature for 24 hours without stirring, and then dried at 60°C for 3 hours to prepare a red solid. Thereafter, Step 3 of Example 1 was performed in the same manner to prepare a composite catalyst 4, which is porous titania encapsulated with gold nanoparticles.

(Manufacturing Example 5)

Composite catalyst 5 was manufactured by performing the same steps as in [Step 1-1] of the above Manufacturing Example 1, except that the molar ratio of oleylamine and HAuCl·3H ₂ O was adjusted to manufacture gold nanoparticles having an average particle size of 12 nm.

(Manufacturing Example 6)

10 g of tetraethyl orthosilicate (TEOS) was dissolved in 12.0 g of ethanol, 5.4 g of 0.01 M hydrochloric acid was added, and the mixture was stirred at room temperature for 20 minutes to prepare a TEOS solution. Then, 2.8 g of Pluronic F127 was dissolved in 6 g of ethanol, and the solution was added to the TEOS solution, stirred at room temperature for 3 hours, and maintained at room temperature without stirring for 40 hours to prepare a precipitate. The precipitate was washed with water, dried, and then calcined at 500°C for 7 hours to prepare mesoporous silica.

The above mesoporous silica powder was immersed in an HAuCl· _3H2O aqueous solution, and the excess aqueous solution was removed by air blowing. Then, after drying at 300°C for 3 hours, the resultant was calcined at 250°C for 1 hour in a reducing treatment gas of 10% hydrogen gas and 90% nitrogen gas, thereby producing a mesoporous silica catalyst having gold nanoparticles captured therein.

(Experimental Example 1) EXAFS (Extended X-ray absorption fine structure) analysis

Extended X-ray absorption fine structure (EXAFS) measurements were performed using the 4C and 10C beamlines of the Pohang Accelerator (PLS-II). The EXAFS spectra were Fourier transformed to obtain the radial distribution function.

Referring to FIG. 3, FIG. 3 illustrates a radial distribution function of a composite catalyst according to Manufacturing Example 1. In the radial distribution function, a peak due to bulk Au-Au bonding was observed in the range of 2.8 to 3.0 Å, and when the interatomic distance of this peak is referred to as D3, the peak of the radial distribution function was defined based on D3. Specifically, D1 and D2 are the interatomic distances of the maximum peak found in the range satisfying Equations 2 and 3 below, respectively, and the positions of D1, D2, and D3 are shown in Table 1. In addition, the ratios of the height (DH1) and area (DA1) of the peak of the interatomic distance D1 and the height (DH2) and area (DA2) of the peak of the interatomic distance D2 were calculated and shown in Table 1.

[Formula 2]

0.8≤(D1/D3)≤0.95

[Formula 3]

0.6≤(D2/D3)≤0.7

Meanwhile, Manufacturing Examples 1, 3, and 4 showed bimodal peaks as shown in Fig. 3, and Manufacturing Example 2 showed a single peak, but showed a tendency of a peak shifted to the right. Meanwhile, Manufacturing Examples 5 and 6 showed a single peak that was not shifted.

Manufacturing example 1 Manufacturing example 2 Manufacturing example 3 Manufacturing example 4 Manufacturing example 5 Manufacturing example 6 DH2/DH1 0 0.227 0 0 0.298 - DA2/DA1 0 0.129 0 0 0.249 - D1 2.5532Å 2.5893Å 2.5607Å 2.5939Å 2.6093Å - D2 - 1.8471Å - - 1.8488Å - D3 2.911Å 2.8967Å 2.9601Å 2.9526Å 2.9207Å 2.934Å D1/D3 0.8771 0.894 0.8651 0.8785 0.8934 - D2/D3 - 0.638 - - 0.6330 -

(Examples 1 to 5)

Each of the composite catalysts manufactured in Manufacturing Examples 1 to 5 was mixed in an aqueous solution at 10 wt% and milled to prepare each dispersion. The average particle size of the milled composite catalyst powder was 0.8 μm. An inorganic binder silica sol having an average particle size of 32 nm, whose pH was adjusted to 4 by adding acetic acid to each dispersion, was mixed in at 1 wt% of the dispersion. Then, an organic binder, poly(N-vinyl pyrrolidone), was mixed in at 2 wt% of the dispersion to prepare each coating slurry.

Each of the above-mentioned 10 cm x 10 cm x 10 cm Cordierite monolithic honeycombs was immersed in each of the coating slurries for 1 minute, then taken out, and the excessively adhered slurry was removed by blowing air, and then sufficiently dried. The immersion and drying processes were repeated 10 times, and each honeycomb whose coating was completed was placed in a high-temperature furnace and calcined at 450°C for 4 hours to finally manufacture a catalyst reaction unit.

(Comparative Example 1)

In the above Example 1, a catalyst reaction unit was manufactured in the same manner as in Manufacturing Example 6, except that the catalyst of Manufacturing Example 6 was used instead of Manufacturing Example 1.

(Experimental Example 2) Analysis of removal of passive hydrogen gas

A mixed gas containing 100% relative humidity, 1% by volume of hydrogen, 21% by volume of oxygen, and the remainder of an inert gas was supplied at 100,000 gas space velocity (GHSV, hr ^-1 ) to the above catalyst reaction section (room temperature 25℃), and the hydrogen contained in the gas discharged through the catalyst layer was analyzed to calculate the hydrogen recombination rate [(injected hydrogen concentration - discharged hydrogen concentration) / injected hydrogen concentration x 100)], which is summarized in Table 2.

catalyst complex Feeding gas and feeding conditions Hydrogen recombination rate Example 1 Manufacturing example 1 A mixed gas containing 100% relative humidity, 1% by volume of hydrogen and 21% by volume of oxygen,
100,000 space velocity (GHSV, hr ^-1 )
100% Example 2 Manufacturing example 2 100% Example 3 Manufacturing example 3 100% Example 4 Manufacturing example 4 100% Example 5 Manufacturing example 5 94% Comparative Example 1 Manufacturing example 6 12%

Referring to Table 2 above, it was confirmed that the hydrogen removal device including the composite catalyst according to the present invention has a hydrogen recombination rate (removal rate) of 90% or more at high space velocity, which is very high compared to the comparative examples. In particular, in the case of Examples 1 to 4, it was confirmed that the hydrogen removal rate was 100%. Although the present invention has been described by specific matters and limited examples and drawings as described above, these have been provided only to help a more general understanding of the present invention, and the present invention is not limited to the above examples, and those skilled in the art to which the present invention pertains can make various modifications and variations from these descriptions.

Therefore, the idea of the present invention should not be limited to the described embodiments, and all things that are equivalent or equivalent to the claims described below as well as the claims are included in the scope of the idea of the present invention.

Claims (15)

It comprises a main body forming an internal space connecting a gas inlet and a gas outlet; and a catalytic reaction unit located within the internal space and containing a complex catalyst that oxidizes and removes hydrogen of gas transferred to the internal space; A passive catalytic hydrogen removal device, characterized in that the composite catalyst comprises a porous support including mesopores and gold nanoparticles incorporated within the pores of the porous support. In the first paragraph, The above catalyst reaction section is, A passive catalytic hydrogen removal device comprising a honeycomb-structured support body that divides the internal space and has a plurality of channels formed through which gas passes along the flow direction of the gas within the internal space, and a catalyst coating layer coated with the composite catalyst on the surface of the support body. In the second paragraph, The internal space is divided into an upper internal space and a lower internal space by the above catalyst reaction section. A passive catalytic hydrogen removal device in which the gas flows into the catalytic reaction section through the lower internal space and flows out through the upper internal space. In the second paragraph, A passive catalytic hydrogen removal device, wherein the material of the support is one or a combination of two or more selected from the group consisting of metal oxides, metalloid oxides, metal carbides, and metalloid carbides. In the first paragraph, A passive catalytic hydrogen removal device, wherein a radial distribution function obtained by Fourier transforming an EXAFS (Extended X-ray absorption fine structure) spectrum of the above composite catalyst satisfies the following equation 1. [Formula 1] (DH2/DH1) < 0.3 In the above equation 1, DH1 is the height of the peak at the interatomic distance D1, DH2 is the height of the peak at the interatomic distance D2, and D1 and D2 satisfy equations 2 and 3 below, respectively. [Formula 2] 0.8≤(D1/D3)≤0.95 [Formula 3] 0.6≤(D2/D3)≤0.7 In the above equations 2 and 3, D3 represents the interatomic distance of the bulk Au-Au bond existing at 2.8 to 3.0 Å. In paragraph 5, The above complex catalyst is a passive catalytic hydrogen removal device satisfying the following equation 4. [Formula 4] (DA2/DA1) < 0.25 In the above equation 4, DA1 is the area of the peak at the interatomic distance D1, DA2 is the area of the peak at the interatomic distance D2, and D1 and D2 satisfy the above equations 2 and 3, respectively. In paragraph 5, A passive catalytic hydrogen removal device, wherein (DH2/DH1) in the above formula 1 is 0.25 or less. In Article 6, A passive catalytic hydrogen removal device, wherein (DA2/DA1) in the above formula 4 is 0.18 or less. In paragraph 5, A passive catalytic hydrogen removal device having a bimodal peak in the interatomic distance range of 2.2 to 3.0 Å of a radial distribution function obtained by Fourier transforming the above EXAFS (Extended X-ray absorption fine structure) spectrum. In the first paragraph, A passive catalytic hydrogen removal device, wherein the porous support is a metal oxide or metalloid oxide porous support. In the first paragraph, A passive catalytic hydrogen removal device, wherein the diameter of the nanoparticles is 1 to 20 nm. In the first paragraph, A passive catalytic hydrogen removal device, wherein the nanoparticles are incorporated into some of the mesopores of the porous support, and the mesopores not incorporated with the nanoparticles are interconnected as open pores. In the first paragraph, The above gas is generated in the reactor, Further comprising a fixing member positioned on one side of the outer surface of the main body and fixing the main body to the inner wall of the containment vessel of the reactor; The gas inlet is located at the bottom of the main body, and the gas outlet is located at the upper part of the outer surface of the main body opposite to the outer surface of the main body where the fixing part is located. A passive catalytic hydrogen removal device, wherein the upper surface of the main body is inclined downward from the gas outlet toward the fixed portion. A method for removing hydrogen in a nuclear reactor, comprising the step of supplying gas containing hydrogen generated in a nuclear reactor to a passive catalytic hydrogen removal device according to any one of claims 1 to 16 installed in a nuclear reactor containment vessel. In Article 14, A method for removing hydrogen within a reactor, wherein the above supply is performed by natural convection of the above gas.

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