KR20210155311A - Perovskite oxide composite catalyst, method of preparing same and water gas shift method using same - Google Patents

Abstract

The present invention relates to a perovskite oxide composite catalyst, a method for preparing the same and a water gas shift method using the same catalyst. The composite catalyst includes: a core including a perovskite oxide represented by chemical formula 1 of L_xM^1_yM^2_1-yO_3; and nanoparticles disposed on the surface of the core and including a third transition metal. In chemical formula 1, L represents an element of lanthanides, M^1 and M^2 represent different transition metals, M^1 is a first transition metal, M^2 is a second transition metal, and x and y satisfy following inequalities: 0 < x <= 1, 0 < y < 1. In the composite catalyst according to the present invention, the metals are exsolved from the inside of the lattice of the oxide support to the surface by reduction treatment, and thus the metals are anchored strongly with the support to prevent migration of the metals at high temperature and agglomeration of the metals, thereby providing long-term stability. In addition, in the composite catalyst according to the present invention, the metals are anchored strongly to the support and are formed homogeneously on the surface of the support to provide high catalytic activity and high hydrogen production efficiency when the composite catalyst is applied to a water gas shift reaction.

Description

Perovskite oxide composite catalyst, manufacturing method thereof, and water gas conversion method using the same

The present invention relates to a complex catalyst, a method for producing the same, and a water gas conversion method using the same, and more particularly, a perovskite oxide complex catalyst that can be used for a water gas conversion reaction, a method for preparing the same, and a water gas conversion method using the same is about

Water Gas Shift Reaction (WGSR), which converts carbon monoxide into hydrogen, is widely used in front-line industrial sites such as hydrogen production and fuel reforming systems, as well as ammonia production and steel mill smelting processes. Water gas conversion reaction is a reaction in which carbon monoxide and water vapor react to produce hydrogen and carbon dioxide.

The catalyst used for the water gas conversion reaction in a commercial process is manufactured by impregnating or precipitating a metal on a support, and the formation of a strong bond between the metal and the support is limited in the catalyst prepared in this way. For this reason, depending on the reaction conditions (usually high temperature or high pressure), metal atoms are easily agglomerated to cause loss of active sites, and there is a problem in that activity is reduced. In addition, there is a problem in that poisoning cannot be avoided because the reactants and metals having strong adsorption strength also prefer adsorption of toxic gases such as carbon and sulfur. For regeneration, an additional process of burning and removing carbon or sulfur surrounding the active site in an oxidizing atmosphere accompanied by a high temperature is required. However, there is a problem in that the loss of metal sites occurs in this process, and the performance of the catalyst is deteriorated.

An object of the present invention is to prevent agglomeration by preventing metal movement at high temperatures by eluting metal from the inside of the lattice of the oxide support to the surface by reduction treatment, thereby strongly anchoring the support and the metal. It is to provide a long-term stable complex catalyst.

It is also an object of the present invention to provide a complex catalyst with high catalytic activity and high hydrogen production efficiency when applied to water gas conversion reaction because the metal is uniformly formed on the surface of the support as well as the support and the metal are strongly bonded. .

According to an aspect of the present invention, a core comprising a perovskite oxide represented by the following Chemical Formula 1; And it is located on the surface of the core, nanoparticles comprising a third transition metal; is provided a perovskite oxide composite catalyst comprising a.

[Formula 1]

L _x M ¹ _y M ² _1-y O ₃

In Formula 1,

L is a lanthanide element,

M ¹ and M ² are different transition metals,

M ¹ is a first transition metal,

M ² is a second transition metal,

x is 0<x≤1, and y is 0<y<1.

In addition, in the perovskite oxide, the second transition metal may be doped at a lattice position of the first transition metal.

In addition, the third transition metal of the nanoparticles may be the same type as the second transition metal of the perovskite oxide.

In addition, the transition metals M ² in the co-separation energy (co-segregation energy) is the transition metal M ¹ of a ball-greater than the separation energy, wherein the nanoparticle comprises a transition metal M ^2, the ball-separation energy is reduced When sintering under the conditions, M ¹ or M ² in the perovskite oxide may be energy required for co-segregation and eluting to the surface of the perovskite oxide.

In addition, the third transition metal of the nanoparticles may be formed by eluting the second transition metal of the perovskite oxide.

In addition, the lanthanum elements are lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), derbium ( It may include at least one selected from the group consisting of Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), yttermium (Yb), and luterium (Lu).

In addition, the first, second, or third transition metal is each independently scantium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co) ), nickel (Ni), copper (Cu), zinc (Zn), and may include any one selected from the group consisting of zirconium (Zr).

Also, in Formula 1, L may be lanthanum element (La), M ¹ may be iron (Fe), and M ² may be nickel (Ni).

In addition, the perovskite oxide catalyst may be used as a catalyst for a water gas shift reaction (WGS) represented by Reaction Formula 1 below.

[Scheme 1]

CO + H ₂ O → CO ₂ + H ₂

According to another aspect of the present invention, (a) preparing a mixed solution by mixing a lanthanum group element precursor, a first transition metal precursor, a second transition metal precursor, a complexing agent and a solvent; (b) evaporating the solvent of the mixed solution to prepare a gel; (c) drying the gel and calcining to prepare a perovskite powder; And (d) by heat-treating the perovskite powder under reducing conditions, and a core including a perovskite oxide represented by the following formula (1), and located on the surface of the core, the nano comprising a third transition metal There is provided a method for producing a perovskite oxide composite catalyst comprising; preparing a perovskite oxide composite catalyst comprising particles.

[Formula 1]

L _x M ¹ _y M ² _1-y O ₃

In Formula 1,

L is a lanthanide element,

M ¹ and M ² are different transition metals,

M ¹ is a first transition metal,

M ² is a second transition metal,

x is 0<x≤1, and y is 0<y<1.

In addition, in the perovskite oxide, the second transition metal may be doped at a lattice position of the first transition metal.

In addition, the lanthanum group element precursor includes a lanthanum precursor, and the lanthanum precursor is lanthanum nitrate hexahydrate (Lanthanum(III) nitrate hexahydrate, La(NO ₃ ) ₃ .6H ₂ O), lanthanum chloride heptahydrate ( Lanthanum(III) chloride heptahydrate, LaCl ₃ ㆍ7H ₂ O), lanthanum acetate hydrate (Lanthanum(III) acetate hydrate, La(CH ₃ COO) ₃ ㆍxH ₂ O), lanthanum nitrate hydrate (Lanthanum(III) nitrate) hydrate, La(NO ₃ ) ₃ •xH ₂ O) and lanthanum chloride hydrate (Lanthanum(III) chloride hydrate, LaCl ₃ •xH ₂ O) may include at least one selected from the group consisting of.

In addition, the first transition metal precursor may include an iron precursor, and the second transition metal precursor may include a nickel precursor.

In addition, the iron precursor is iron nitrate nonahydrate (Iron(III) nitrate nonahydrate, Fe(NO ₃ ) ₃ ·9H ₂ O), iron sulfate (Iron(II) sulfate, FeSO ₄ ) and iron (Iron(III) chloride) , FeCl ₃ ) may include one or more selected from the group consisting of, the nickel precursor is nickel nitrate hexahydrate (Nickel (II) nitrate hexahydrate, N ₂ NiO ₆ ·6H ₂ O), nickel sulfate (Nickel sulfate, NiSO ₄ ) and nickel chloride (Nickel chloride, NiCl ₂ ) It may include at least one selected from the group consisting of.

In addition, the complexing agent may include at least one selected from the group consisting of citric acid, glycine, ethylenediaminetetraacetic acid (EDTA) and polyacrylic acid (PAA).

In addition, the reducing condition is a hydrogen gas atmosphere, the heat treatment may be performed at a temperature of 300 to 1,000 ℃.

According to another aspect of the present invention, in the presence of the perovskite complex catalyst, carbon monoxide and water according to Reaction Formula 1 below to generate carbon dioxide and hydrogen by a water gas shift reaction; aqueous comprising; A gas conversion method is provided.

[Scheme 1]

CO + H ₂ O → CO ₂ + H ₂

In addition, the water gas conversion method comprises the steps of (a) pre-treating the perovskite oxide composite catalyst by contacting an inert gas with the perovskite oxide composite catalyst; And (b) generating carbon dioxide and hydrogen by performing a water gas shift reaction of carbon monoxide and water according to Scheme 1 in the presence of the pre-treated perovskite oxide complex catalyst.

In addition, the pretreatment of step (a) may be performed at 100 to 200 ℃.

In addition, the water gas conversion reaction of step (b) may be performed at 100 to 700 ℃.

In addition, the inert gas may include at least one selected from the group consisting of nitrogen gas, helium gas, neon gas, argon gas, and crito gas.

In the composite catalyst of the present invention, metal is eluted from the inside of the lattice of the oxide support to the surface by reduction treatment, and the support and the metal are strongly anchored, thereby preventing the movement of metal at high temperature and preventing aggregation. It has a long-term stable effect.

In addition, the composite catalyst of the present invention has the effect of not only strongly bonding the support and the metal, but also forming the metal uniformly on the surface of the support, so that the catalytic activity is high, and the hydrogen production efficiency is high when applied to the water gas conversion reaction.

1 is a schematic diagram showing a method for preparing a composite catalyst of the present invention.
2 is an X-ray diffraction pattern of L9FNO5 and L9FNO5-R of Example 1. FIG.
3 is a graph showing the unit cell volume and specific surface area of L9FNO5 and L9FNO5-R of Example 1.
4 (a) and (b) are SEM images of L9FNO5 and L9FNO5-R of Example 1, respectively.
5 (a) and (b) are HR-STEM images and EDS element mapping images of L9FNO5 and L9FNO5-R of Example 1, respectively.
6 is an enlarged HR-STEM image of L9FNO5-R of Example 1.
_{7 (a) and (b) are CO conversion and H 2} yield according to the reaction temperature of L9FNO5 and L9FNO5-R of Example 1, Fe-Cr of Comparative Example 1, and Ni/L9FO of Comparative Example 2, respectively. It is a graph.
_{8 (a) and (b) are CO conversion and H 2} yield according to the reaction time of L9FNO5 and L9FNO5-R of Example 1, Fe-Cr of Comparative Example 1, and Ni/L9FO of Comparative Example 2, respectively It is a graph.
9 (a) is an SEM image before (top) and after (bottom) etching L9FNO5-R of Example 1, (b) is L9FNO5, L9FNO5-R and after etching of Example 1, respectively ( It is a graph showing the CO conversion according to the reaction temperature of L9FNO5-RE).
10 is a result of studying the surface properties of L9FNO5 and L9FNO5-R of Example 1 for _{H 2 -Temperature Programmed Reduction (H 2} -TPR).
Figure 11 _{O 2 -Temperature Programmed Desorption (O 2} -TPD) the results of the study in Example 1 L9FNO5 and surface properties of the R-L9FNO5 for.
12 is a result of studying the surface properties of L9FNO5 and L9FNO5-R of Example 1 during CO-Temperature Programmed Desorption (CO-TPD).
13 is a graph showing _{CO 2} formation of L9FNO5 and L9FNO5-R of Example 1 during CO-Temperature Programmed Reduction (CO-TPR).
14 is an XRD result of the composite catalyst prepared according to Examples 2-1 and 2-2.
15 (a) and (b) are La _{0 of Example 2-1, respectively. 9} Fe _{0 . 85} Ni _{0 .} SEM images of ₁₅ O ₃ and La _0.9 Fe _0.85 Ni _0.15 O _{3 -R.}
16 (a) and (b) are La _{0 of Example 2-1, respectively. 9} Fe _{0 . 85} Ni _{0 .} HR-STEM images of ₁₅ O ₃ and La _0.9 Fe _0.85 Ni _0.15 O _{3 -R.}
17 (a) and (b) are La _{0 of Example 2-1, respectively. 9} Fe _{0 . 85} Ni _{0 . 15} O ₃ and La _0.9 Fe _0.85 Ni _0.15 O ₃ -R according to the reaction temperature of CO conversion and H _{2 A} graph showing the yield.
Figure 18 shows the result of studies on the surface characteristics of the _{H 2 -Temperature Programmed Reduction (H 2} -TPR) Example 2-1 La _0.9 Fe _0.85 Ni _0.15 O ₃ and _{La 0.9 Fe 0.85 Ni 0.15 O 3} -R while.

Since the present invention can apply various transformations and can have various embodiments, specific embodiments are illustrated and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. In describing the present invention, if it is determined that a detailed description of a related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

In addition, terms including ordinal numbers such as first, second, etc. to be used below may be used to describe various elements, but the elements are not limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component.

Also, when it is stated that a certain component is “on another component,” “formed on another component,” “located on another component,” or “stacked on another component,” the It may be formed, positioned, or laminated by being directly attached to the front surface or one surface on the surface of other components, but it will be understood that other components may be further present in the middle.

The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present application, terms such as “comprise” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof.

Hereinafter, the composite catalyst of the present invention will be described.

The present invention relates to a core comprising a perovskite oxide represented by the following formula (1); and nanoparticles located on the surface of the core and including a third transition metal; provides a perovskite oxide composite catalyst comprising.

[Formula 1]

L _x M ¹ _y M ² _1-y O ₃

In Formula 1,

L is a lanthanide element,

M ¹ and M ² are different transition metals,

M ¹ is a first transition metal,

M ² is a second transition metal,

x is 0<x≤1, and y is 0<y<1.

The perovskite oxide may be one in which the second transition metal is doped at a lattice position of the first transition metal.

The third transition metal of the nanoparticles may be the same type as the second transition metal of the perovskite oxide.

The transition metals M ² in the co-separation energy (co-segregation energy) is the transition metal M ¹ of a ball-greater than the separation energy, the nanoparticle comprises a transition metal M ^2, and the co-separation energy-reducing conditions During sintering, M ¹ or M ² in the perovskite oxide may be energy required for co-segregation and eluting to the surface of the perovskite oxide.

The third transition metal of the nanoparticles may be formed by eluting the second transition metal of the perovskite oxide.

The perovskite oxide has an ABO ₃ crystal structure. A cation with a large ionic radius coordinating with 12 oxygen atoms occupies the A-site, and a cation with a relatively small ionic radius having 6 coordination occupies the B-site. During the thermal reduction treatment, the transition metal in the B-site moves from the oxide lattice to the surface to form nanoparticles and is eluted from the perovskite. The eluted metal nanoparticles can reenter the bulk lattice under oxidation treatment to be restored, which can reversibly move metal atoms depending on the treatment conditions.

The lanthanum elements include lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), and derbium (Tb). ), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), may include at least one selected from the group consisting of yttermium (Yb) and luterium (Lu), and the It may be substituted at the A site at the ABO _{3 lattice position.}

The first, second, or third transition metal is each independently scantium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co) , nickel (Ni), copper (Cu), zinc (Zn), and may include any one selected from the group consisting of zirconium (Zr).

In Formula 1, L may be lanthanum element (La), M ¹ may be iron (Fe), M ² may be nickel (Ni), and may be substituted for B site at the lattice position of _{ABO 3 .}

The perovskite oxide catalyst may be for use as a catalyst for a water gas shift reaction (WGS) represented by the following Reaction Formula 1.

[Scheme 1]

CO + H ₂ O → CO ₂ + H ₂

1 is a schematic diagram showing a method for preparing a composite catalyst of the present invention. Hereinafter, a method for preparing the composite catalyst of the present invention will be described with reference to FIG. 1 .

first, lanthanum An elemental precursor, a first transition metal precursor, a second transition metal precursor, a complexing agent and a solvent are mixed to prepare a mixed solution (step a).

The lanthanum group element precursor may include a lanthanum precursor.

The lanthanum precursor is lanthanum nitrate hexahydrate (Lanthanum(III) nitrate hexahydrate, La(NO ₃ ) ₃ ㆍ6H ₂ O), lanthanum chloride heptahydrate (Lanthanum(III) chloride heptahydrate, LaCl ₃ ㆍ7H ₂ O) , Lanthanum(III) acetate hydrate, La(CH ₃ COO) ₃ .xH ₂ O), Lanthanum(III) nitrate hydrate, La(NO ₃ ) ₃ .xH ₂ O) and It may include one or more selected from the group consisting of lanthanum chloride hydrate (Lanthanum(III) chloride hydrate, LaCl ₃ ·xH _{2 O), and preferably may include lanthanum nitrate hexahydrate.}

The first transition metal precursor may include an iron precursor, and the second transition metal precursor may include a nickel precursor.

The iron precursor is iron nitrate nonahydrate (Iron(III) nitrate nonahydrate, Fe(NO ₃ ) ₃ ·9H ₂ O), iron sulfate (Iron(II) sulfate, FeSO ₄ ) and iron chloride (Iron(III) chloride, FeCl ₃ ) It may include at least one selected from the group consisting of, preferably, iron nitrate 9hydrate.

The nickel precursor is nickel nitrate hexahydrate (Nickel (II) nitrate hexahydrate, N ₂ NiO ₆ ·6H ₂ O), nickel sulfate (Nickel sulfate, NiSO ₄ ) and nickel chloride (Nickel chloride, NiCl ₂ ) selected from the group consisting of It may include one or more, preferably nickel nitrate hexahydrate.

The complexing agent may include at least one selected from the group consisting of citric acid, glycine, ethylenediaminetetraacetic acid (EDTA), and polyacrylic acid (PAA), and preferably includes citric acid can do.

Next, the solvent of the mixed solution is evaporated to prepare a gel (step b).

Next, the gel dry it , by calcination perovskite A powder is prepared (step c).

Finally, the above perovskite By heat-treating the powder under reducing conditions, perovskite A core comprising an oxide, and on the surface Located, comprising nanoparticles comprising a third transition metal perovskite An oxide composite catalyst is prepared (step d).

[Formula 1]

L _x M ¹ _y M ² _1-y O ₃

In Formula 1,

L is a lanthanide element,

M ¹ and M ² are different transition metals,

M ¹ is a first transition metal,

M ² is a second transition metal,

x is 0<x≤1, and y is 0<y<1.

The perovskite oxide may be one in which the second transition metal is doped at a lattice position of the first transition metal.

The reducing condition is a hydrogen gas atmosphere, and the heat treatment may be performed at a temperature of 300 to 1,000 °C. If the temperature is less than 300 ° C, it is not preferable because it does not elute, and when it exceeds 1,000 ° C, the perovskite structure is undesirable.

Hereinafter, the water gas conversion method of the present invention will be described.

The present invention provides a water gas conversion method comprising; generating carbon dioxide and hydrogen by performing a water gas shift reaction of carbon monoxide and water according to Reaction Formula 1 below in the presence of the perovskite complex catalyst. .

[Scheme 1]

CO + H ₂ O → CO ₂ + H ₂

The water gas conversion method comprises the steps of (a) pre-treating the perovskite oxide composite catalyst by contacting an inert gas with the perovskite oxide composite catalyst; And (b) generating carbon dioxide and hydrogen by performing a water gas shift reaction of carbon monoxide and water according to Scheme 1 in the presence of the pre-treated perovskite oxide complex catalyst.

The pretreatment of step (a) may be performed at 100 to 200 °C. If the temperature is less than 100°C, it is not preferable because unnecessary foreign substances cannot be removed, and when it exceeds 200°C, it is not preferable because catalyst sintering may occur.

The water gas conversion reaction of step (b) may be carried out at 100 to 700 ℃. If the temperature is less than 100 ℃, it is not preferable because the catalyst cannot be activated, and if it exceeds 700 ℃, it is not preferable because it exceeds the temperature conditions of the actual industrial water gas conversion reaction.

The inert gas may include at least one selected from the group consisting of nitrogen gas, helium gas, neon gas, argon gas, and crito gas.

[Example]

Hereinafter, the present invention will be described in more detail by way of examples. However, this is for illustrative purposes, and the scope of the present invention is not limited thereto.

Example 1: Composite catalyst (La _0.9 Fe _0.95 Ni _0.05 O ₃ ) manufacturing

A composite catalyst was prepared using the sol-gel method. First, a solution was prepared by dissolving citric acid as a complexing agent in distilled water. followed by stoichiometric amounts of metal nitrates La(NO ₃ ) ₃ .6H ₂ O (Alfa Aesar, 99.9 %), FeN ₃ O ₉ 9H ₂ O (Sigma-Aldrich, ≥98 %), N ₂ NiO ₆ .6H ₂ O (Sigma-Aldrich, 99.999%) was added to the solution along with an appropriate amount of ethylene glycol (Junsei Chem., 99.5%) and citric anhydride (Junsei Chem., 99.5%). The molar ratio of total metal cations to citric acid was 1:1, and the mass ratio of citric acid to ethylene glycol was 60:40. Fully thermal stirring at 80° C. and evaporation gave a viscous gel. The obtained sample was dried at 200° C. with a hot stirrer and calcined in a mantle at 1,000° C. for 4 hours. Then, the powder was reduced in a tube furnace at a flow rate of 100 mL/min in 100% H ₂ at 650 ° C. for 5 hours, so that nickel nanoparticles were eluted on the surface of La _{0 . 9} Fe _{0 . 95} Ni _{0 . 05} O _{3 A} perovskite oxide composite catalyst was prepared.

2 to 13 , the powder before reduction treatment was represented by L9FNO5, and the composite catalyst prepared by reduction treatment was represented by L9FNO5-R.

Example 2: Composite catalyst (La _0.9 Fe _0.85 Ni _0.15 O ₃ ) manufacturing

Example 2-1: reduction at 650 °C

A composite catalyst was prepared using the sol-gel method. First, a solution was prepared by dissolving citric acid as a complexing agent in distilled water. followed by stoichiometric amounts of metal nitrates La(NO ₃ ) ₃ .6H ₂ O (Alfa Aesar, 99.9 %), FeN ₃ O ₉ 9H ₂ O (Sigma-Aldrich, ≥98 %), N ₂ NiO ₆ .6H ₂ O (Sigma-Aldrich, 99.999%) was added to the solution along with an appropriate amount of ethylene glycol (Junsei Chem., 99.5%) and citric anhydride (Junsei Chem., 99.5%). The molar ratio of total metal cations to citric acid was 1:2, and the molar ratio of citric acid to ethylenediaminetetraacetic acid (EDTA) was 1:1. Fully thermal stirring at 80° C. and evaporation gave a viscous gel. The obtained sample was dried at 200° C. with a hot stirrer and calcined in a mantle at 1,000° C. for 4 hours. Then, the powder was reduced in a tube furnace at a flow rate of 100 mL/min in 10% H ₂ at 650 ° C. for 10 hours to obtain La _0.9 Fe _0.85 Ni _0.15 O ₃ perovskite oxide complex catalyst with nickel nanoparticles eluted on the surface. prepared.

Before the reduction treatment in FIGS. 15 to 18 , the powder is La _{0 . 9} Fe _{0 . 85} Ni _{0 . 15} O ₃ , and the composite catalyst prepared by reduction treatment was expressed as La _0.9 Fe _0.85 Ni _0.15 O ₃ -R.

Example 2-2: Reduction at 850 °C

_{La 0.9} Fe _0.85 Ni _0.15 O ₃ Perovsky in which nickel nanoparticles were eluted on the surface in the same manner as in Example 2-1 except for reducing at 850° C. instead of reducing at 650° C. in Example 2-1 A complex oxide catalyst was prepared.

Comparative Example 1: Preparation of a commercial catalyst (Fe-Cr)

An iron-chrome-based high-temperature gas shift catalyst HiFUEL® W210, which is a HT-WGS commercial catalyst, was purchased from Alfa Aesar and used as Comparative Example 1.

Comparative Example 2: Nickel (Ni) Loaded La _0.9 FeO ₃ Catalyst (Ni/L ₉ Preparation of FO)

_{La 0} loaded with nickel (Ni) by incipient wet impregnation (IWI) method _{. 9} FeO ₃ catalyst (Ni/L ₉ FO) was prepared. Ni (NO _{3) 2} aqueous solution (Sigma-Aldrich, 99.999%) to L _{0. 9} FeO ₃ was added dropwise (dropwise) to synthesize a Ni / L ₉ FO to the support and aged for 1 hour in air, and then, overnight, 80 ℃ dried in Then, it was calcined in air at 400° C. for 3 hours _{to prepare a La 0.9} FeO ₃ catalyst (Ni/L ₉ FO). At this time, the Ni loading amount was 1.3 wt%.

[Test Example]

Test Example 1: X-ray diffraction pattern and specific surface area analysis of the composite catalyst according to Example 1

The composite catalyst of the present invention was prepared through a modified sol-gel method, and the most common element lanthanum (La) as the A-site element, iron (Fe) as the main B-site element, and nickel (Ni) as the doped element were used. selected. The elution behavior of the doped B-site metal is mainly affected by the co-segregation energy, and the Ni metal easily elutes on the surface of the perovskite substrate because the co-segregation energy is higher than that of Fe, This composition is expected to maximize eluted particle formation.

2 is an X-ray diffraction pattern of L9FNO5 and L9FNO5-R of Example 1. FIG. Referring to FIG. 2 , it was confirmed that the structure of _{L9FNO5 followed the general perovskite LaFeO 3 structure.} This indicates the complete incorporation of Ni into the lattice structure. After the reduction treatment (L9FNO5-R), the LaFeO ₃ structure was well maintained and a metal peak between Ni and Fe was observed. The dominant Ni metal peak (44.520˚) and Fe metal peak (44.764˚) should be observed. However, since a very small amount of Fe metal can be formed during the reduction process, although the coexistence of Ni and Fe is possible, the sample peak is closer to the Ni peak, so the main part may be Ni particles. The alloy Ni ₃ Fe peak should appear at 44.216°, but the peak at 44.216° is smooth, so it is unlikely that the eluted particles are a nickel-iron alloy such as _{Ni 3 Fe.}

A rietveld refinement analysis combined with a database structure _{for LaFeO 3} was used to suggest the crystal structure. An orthorhombic lattice (lattice parameters: a = 5.5647 Å, b = 7.8551 Å, c = 5.556 Å) with space group Pnma (Nr. 62) was matched.

3 is a graph showing the unit cell volume and specific surface area of L9FNO5 and L9FNO5-R of Example 1. Referring to FIG. 3 , the ideal _{lattice volume of LaFeO 3} (LFO) is 242.51 Å ³ , and the volume is expanded to ^{242.97 Å 3 after Ni doping.} This is because the ion radius of Ni ^{2 +} (0.69 Å) longer than the Fe ^{3 +} (0.645 Å). Assuming that the nickel is extracted with Ni ^{+ 3,} since the ion radius of Ni ^{3 +} (0.60Å) slightly smaller than the ionic radius of Fe ^{3 +} Ni has been reported to be possible unit cell shrinkage when incorporated into the lattice. However, this is more common when the Ni content is greater than 10 mol %. After the reduction treatment, Ni ^{+ 2} is considered to be reduced to Ni ⁰ were found in the surface of a nanoparticle, Fe ^{+ 3} is reduced at the same time as Fe ^{2 +} (0.70Å) expanded by adding a cell volume.

Also, referring to FIG. 3 , as nickel was doped into the lattice, the specific surface area of the sample increased, and after reduction treatment, the surface area of Ni nanoparticles was further increased. In summary, nickel is _{well doped into the LaFeO 3} lattice without changing its structure, and eluted metallic Ni nanoparticles by XRD pattern and unit cell expansion can be expected after appropriate reduction treatment, and successfully without structural decomposition or phase transformation. indicates that it has been eluted.

Test Example 2: SEM and HR-TEM image analysis of the composite catalyst according to Example 1

4 (a) and (b) are SEM images of L9FNO5 and L9FNO5-R of Example 1, respectively. Referring to FIG. 4 , the surface of the synthesized sample looked smooth and dense, and after the reduction treatment, metal nanoparticles eluted from the surface could be easily observed, and the particle size was about 40-50 nm. The eluted metal nanoparticles were well fixed on the perovskite surface by one-third the diameter of the perovskite.

5 (a) and (b) are HR-STEM images and energy dispersive spectrometer (EDS) element mapping images of L9FNO5 and L9FNO5-R of Example 1, respectively. Referring to FIG. 5 , it was shown that all elements were uniformly dispersed in the particles before the reduction treatment, and after the reduction treatment, La and O were hardly present in the nanoparticle portion, and almost all of the Ni in the bulk contained some Fe migrated to coexisting surface nanoparticles.

6 is an enlarged HR-STEM image of L9FNO5-R of Example 1. Referring to FIG. 6 , the lattice space of the eluted nanoparticle plane is 2.1726 Å, which is consistent with the lattice content of the (002) plane of Ni metal. This indicated that the eluted particles were mainly composed of Ni metal. Although a small trace element of Fe is simultaneously eluted, there is no alloy present on the substrate perovskite because the Ni-Fe alloy has a completely different lattice space. This observation is consistent with previous XRD results.

Test Example 3: Water gas conversion activity analysis of the composite catalyst according to Example 1

Water gas shift reaction was performed in a continuous-flow stationary quartz reactor under atmospheric pressure. A 30 mg sample was loaded and pretreated with argon (Ar) at 150° C. for 30 minutes. A total of 73 sccm of feed gas was introduced with 1.0 vol% CO and 23 vol% H _{2 O in Ar balance for the reaction.} The Gas Hourly Space Velocity (GHSV) was 146,000 mL/g·h. The reactor was heated from 150° C. to 600° C. with a 1.7° C./min ramp. It was held for 30 minutes at every 50° C. temperature interval to reach a steady state. Mol sieve column (86163, SUPELCO, 3 ft Х 1/8 in. Х2.1 mm) and bed porapak column (88599, SUPELCO, 10 ft × 1/8 in. ×) packed in series with thermal conductivity detector (TCD) The product gas was monitored by on-line gas chromatography (GC, Agilent 7890 system) equipped with a 2.1 mm). To minimize human error, the catalytic activity test for each sample was repeated at least three times. CO conversion and H ₂ yield were calculated as follows.

where [CO] _in and [CO] _out represent the CO concentration (vol%) of the inlet and outlet gases, respectively, [H ₂ ] _{exp is the H 2} volume measured by GC, and ρ _H2 is the density at 150°C , n _H2 is the theoretical molecular mole derived from the reaction equation, and M _H2 is the molecular weight of _{H 2 .}

_{7 (a) and (b) are CO conversion and H 2} yield according to the reaction temperature of L9FNO5 and L9FNO5-R of Example 1, Fe-Cr of Comparative Example 1, and Ni/L9FO of Comparative Example 2, respectively. It is a graph.

Referring to (a) of Figure 7, after the reduction treatment, the CO conversion was significantly improved in the HT-WGS window temperature (350-600 ℃) conditions. _{The light-off T 50} , the temperature at which CO conversion reaches 50%, was 458 °C and 445 °C for commercial Fe-Cr and L9FNO5-R, respectively, and for pristine L9FNO5 and Ni/L9FNO5, the light-off T 50 , which reached 50% conversion even at 600 °C, was couldn't The CO conversion was significantly improved after the elution treatment, because as described above, there was no other structural change except for the Ni nanoparticles eluted, which played an important role in the _{eluted Ni nanoparticles converting CO into CO 2 .} indicates to do Meanwhile, to determine the difference between the eluted Ni metal and the conventional loaded Ni-based catalyst, the loaded Ni/L9FO catalyst was tested, and the activity was found to be similar to that of pristine L9FNO5.

For the catalytic activity of HT-WGS, the _{yield of H 2} production is as important as CO conversion due to an undesirable side reaction, ie, a side reaction to form methane from _{CO/CO 2 hydrogenation.} Referring to (b) of FIG. 7 , the H ₂ yield of L9FNO5-R was twice that of L9FNO5, and the same conclusion was drawn that the eluted nanoparticles improved the production yield of HT-WGS. L9FNO5-R performed significantly better than commercial HT-catalysts at temperatures higher than 450 °C, providing a potential option for industrial applications.

_{8 (a) and (b) are CO conversion and H 2} yield according to the reaction time of L9FNO5 and L9FNO5-R of Example 1, Fe-Cr of Comparative Example 1, and Ni/L9FO of Comparative Example 2, respectively It is a graph.

Referring to (a) and (b) of Figure 8, in addition to the catalytic performance, L9FNO5-R showed adequate catalytic stability. _{The CO conversion and H 2} yield of L9FNO5-R for 50 hours at 550° C. were decreased by 19% and 10%, respectively, whereas the CO conversion and H ₂ yield of pristine L9FNO5 were 41% and 19%, respectively, and the commercial catalyst (Fe- Cr) was decreased by 30% and 12%, respectively. During the initial 5 hours, the H ₂ yield of the commercial catalyst decreased from 32.9% to 28.4%, while L9FNO5-R lost only 0.8% during the same period. In addition, the H ₂ yield of the commercial catalyst was sharply turbulent during the stability test time, especially after 20 hours, whereas L9FNO5-R showed a more stable performance. The activity of Ni/L9FO lost 14% of the initial conversion within 10 hours and the CO conversion decreased from 68% to 40% after 50 hours. This proves that the eluted catalyst can solve the disadvantages of the conventional loaded catalyst by preventing the active site from sintering under high temperature and long operating time. _{In summary, the L9FNO5-R catalyst showed better catalytic properties for CO conversion, H 2} yield and long-term stability than commercial HT-WGS catalysts without consuming precious metals.

Test Example 4: Analysis of Active Species of the Complex Catalyst according to Example 1

It was hypothesized that the active species responsible for the activity enhancement was the eluted Ni nanoparticles. For thorough identification, HCl solution was used to remove surface Ni nanoparticles. Etching of L9FNO5-R was performed with 1.2M HCl solution for 60 seconds, and the sample after etching in FIG. 9 was denoted as L9FNO5-R-E.

9 (a) is an SEM image before (top) and after (bottom) etching L9FNO5-R of Example 1, (b) is L9FNO5, L9FNO5-R and after etching of Example 1, respectively ( It is a graph showing the CO conversion according to the reaction temperature of L9FNO5-RE).

Referring to Figure 9 (a), after the etching treatment, the eluted nanoparticles were removed, leaving only holes on the surface. Referring to Fig. 9(b), the CO conversion of the etched sample L9FNO5-R-E decreased back to the L9FNO5 level. This experiment confirmed the assumption of an active species.

Elution of Ni nano-particles from the L9FNO5 during temperature programmed reduction (H ₂ -TPR) was monitored by the H ₂ consumption (H ₂ consumption). 10 is a result of studying the surface properties of L9FNO5 and L9FNO5-R of Example 1 for _{H 2 -Temperature Programmed Reduction (H 2} -TPR). 10, there are two hydrogen consumption peak for L9FNO5, the peak at 312 ℃ denotes a surface oxygen, Fe in a reducing and Fe ^{3 +} to Ni ⁰ at Ni ^{2 +} in the peak at 456 ℃ the bulk It may be assigned to the partially reduced to the ^{2 +.} In the case of L9FNO5-R, the high-temperature peak disappeared because the doped B-site element available for reduction had already been consumed, and only a small peak at 334°C appeared, indicating a small hydrogen consumption at the defective site with low oxygen coordination. showed The results of H ₂ -TPR suggested successful elution of Ni metal.

Figure 11 _{O 2 -Temperature Programmed Desorption (O 2} -TPD) the results of the study in Example 1 L9FNO5 and surface properties of the R-L9FNO5 for. The _{oxygen species revolved in the O 2} -TPD spectrum can be classified into four types according to the bond strength. physically adsorbed oxygen that can be removed by purging an inert gas and thus cannot be included in the _{O 2 -TPD spectrum; O 2} ⁻ (ad) and O ⁻ (ad), located in surface vacancy and prone to desorption, these species are also referred to as oxygen vacancy; Finally species is a hard surface lattice oxygen O ^2- to extract. Referring to FIG. 11 , in the case of pristine L9FNO5, one weak peak was observed at 363° C., which _{can be assigned to surface oxygen desorption O 2} ⁻ (ad) and O ⁻ (ad) species, and the A defect is perov Oxygen vacancies may be present in L9FNO5, although in small amounts, as it slightly destabilizes the skyte structure. On the other hand, for the L9FNO5-R sample, a much sharper peak appeared at low temperature (325 °C), which could be assigned to oxygen adsorbed on the metal surface, and the other peak followed at about 400 °C, which was the surface oxygen desorption O ₂ ^- (ad) and O ^- (ad) species were similar. The sharp peak at low temperature suggested better reduction of L9FNO5-R and better catalytic activity for WGS.

CO-TPD and CO-TPR were performed to clarify the CO adsorbing species in the samples.

12 is a result of studying the surface properties of L9FNO5 and L9FNO5-R of Example 1 during CO-Temperature Programmed Desorption (CO-TPD). Referring to FIG. 12 , a clear difference was observed in the CO adsorption capacity between the two samples. The CO adsorption of pristine L9FNO5 was almost zero compared to that of L9FNO5-R, and this apparent difference explained why the CO conversion of L9FNO5-R was much higher. This strong CO adsorption capacity can come from the eluted Ni metal. As a result there is also confirmed by a chemical adsorption CO-, where each of 2.47cm ³ / g and 0.00cm ³ / g for the CO adsorption unit volume L9FNO5-R and L9FNO5.

13 is a graph showing _{CO 2} formation of L9FNO5 and L9FNO5-R of Example 1 during CO-Temperature Programmed Reduction (CO-TPR). _{Signals of CO 2} formation were collected during the CO-TPR process. Referring to FIG. 13 , in the case of pristine L9FNO5, it is relatively easy to form _{CO 2} by combining CO with surface oxygen species because there was sufficient oxygen on the sample surface. At 288 ℃ CO ₂ forming a peak may be considered from the combination of CO and surface oxygen, the peak at 470 ℃ may be assigned to the lattice oxygen in combination with Ni ^{3 +} / Ni ^{2 +,} the peak at 652 ℃ is It may be assigned to the lattice oxygen combined with Fe ^{+ 3.} In the case of L9FNO5-R, since there are more oxygen vacancies than in pristine L9FNO5, as mentioned in the previous CO-TPD analysis, even though this sample had stronger CO adsorption capacity, CO ₂ formation due to lack of oxygen resource There are more difficulties in The first peak appearing at 546 °C can be assigned to the defective site of oxygen with ^{low coordination O − (ad).} The peak at 700 °C can be assigned to the ^{lattice oxygen O 2 -.} Therefore, in the absence of an external oxygen source, the CO ₂ formation ability of L9FNO5 is superior to that of L9FNO5-R.

In the WGS reaction, since _{the dissociation of H 2} O is the only source of oxygen, _{the adsorption and dissociation capacity of H 2} O can seriously affect the activity. It can be easily concluded that the eluted metal and oxygen vacancies are the active sites of WGS, and the eluted metals _{dissociate H 2} O to play more important roles as active sites for CO adsorption and oxygen transmitters.

Test Example 5: XRD and SEM analysis of the composite catalyst according to Example 2

14 is an XRD result of the composite catalyst prepared according to Examples 2-1 and 2-2. Referring to FIG. 14 , it was confirmed that the perovskite structure was maintained when the reduction treatment was performed at 650° C. for 10 hours, but _{collapsed into La 2} O _{3 when the reduction treatment was performed at 850° C.}

15 (a) and (b) are La _{0 of Example 2-1, respectively. 9} Fe _{0 . 85} Ni _{0 .} SEM images of ₁₅ O ₃ and La _0.9 Fe _0.85 Ni _0.15 O _{3 -R.} Referring to FIG. 15 , it was confirmed that the metal nanoparticles appeared on the surface after the reduction treatment.

16 (a) and (b) are La _{0 of Example 2-1, respectively. 9} Fe _{0 . 85} Ni _{0 .} HR-STEM images of ₁₅ O ₃ and La _0.9 Fe _0.85 Ni _0.15 O _{3 -R.} Referring to FIG. 16 , Ni ⁰ particles were found on the surface after the reduction treatment. It was confirmed that the Ni particles were connected to the _{LaFeO 3 surface.}

Test Example 6: Water gas conversion activity analysis of the composite catalyst according to Example 2

17 (a) and (b) are La _{0 of Example 2-1, respectively. 9} Fe _{0 . 85} Ni _{0 . 15} O ₃ and La _0.9 Fe _0.85 Ni _0.15 O ₃ -R according to the reaction temperature of CO conversion and H _{2 A} graph showing the yield. Referring to FIG. 17, it can be confirmed that the water gas conversion activity is improved after the reduction treatment, and it can be confirmed that the product H ₂ yield is significantly increased.

Test Example 7: Analysis of Active Species of the Complex Catalyst according to Example 2

18 is a H ₂ -Temperature Programmed Reduction of Examples 2-1 for _{(H 2 -TPR) La 0.9 Fe} 0.85 Ni 0.15 O 3 and La _{0. 9} Fe _{0 . 85} Ni _{0 . This} is the result of studying the surface properties of 15 O _{3 -R.} 18, the peak at 347 ℃ may be assigned to the reduction in Ni ⁰ Ni ^{+ 2.} The peak after 600° C. is assigned to the bulk reduction of the perovskite. After the reduction treatment, the Ni reduction peak was clearly reduced, meaning that Ni mainly exists in a metallic state.

As mentioned above, although preferred embodiments of the present invention have been described, those of ordinary skill in the art can add, change, delete or The present invention may be variously modified and changed by addition, etc., and this will also be included within the scope of the present invention. For example, each component described as a single type may be implemented in a dispersed form, and likewise components described as distributed may be implemented in a combined form. The scope of the present invention is indicated by the following claims rather than the above detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention. do.

Claims (20)

A core comprising a perovskite oxide represented by the following formula (1); and
Nanoparticles located on the surface of the core and comprising a third transition metal;
Perovskite oxide composite catalyst comprising:
[Formula 1]
L _x M ¹ _y M ² _{1 - y} O ₃
In Formula 1,
L is a lanthanide element,
M ¹ and M ² are different transition metals,
M ¹ is a first transition metal,
M ² is a second transition metal,
x is 0<x≤1, and y is 0<y<1. According to claim 1,
The perovskite oxide composite catalyst, characterized in that the second transition metal is doped at the lattice position of the first transition metal in the perovskite oxide. 3. The method of claim 2,
The third transition metal of the nanoparticles is a perovskite oxide composite catalyst, characterized in that the same type as the second transition metal of the perovskite oxide. 4. The method of claim 3,
The third transition metal of the nanoparticles is a perovskite oxide composite catalyst, characterized in that formed by elution (exsolution) of the second transition metal of the perovskite oxide. According to claim 1,
The lanthanum elements are lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), and derbium (Tb). ), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), yttermium (Yb) and luterium (Lu) characterized in that it contains at least one selected from the group consisting of Perovskite oxide composite catalyst. According to claim 1,
The first, second, or third transition metal is each independently scantium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co) , Nickel (Ni), copper (Cu), zinc (Zn) and zirconium (Zr) perovskite oxide composite catalyst comprising any one selected from the group consisting of. According to claim 1,
In Formula 1, L is lanthanum element (La), M ¹ is iron (Fe), M ² is a perovskite oxide composite catalyst, characterized in that nickel (Ni). According to claim 1,
The perovskite oxide catalyst is a perovskite oxide composite catalyst, characterized in that for use as a catalyst of the water gas shift reaction (Water Gas Shift reaction, WGS) represented by the following Reaction Formula 1.
[Scheme 1]
CO + H ₂ O → CO ₂ + H ₂ (a) preparing a mixed solution by mixing a lanthanum group element precursor, a first transition metal precursor, a second transition metal precursor, a complexing agent, and a solvent;
(b) evaporating the solvent of the mixed solution to prepare a gel;
(c) drying the gel and calcining to prepare a perovskite powder; and
(d) heat-treating the perovskite powder under reducing conditions, and a core including a perovskite oxide represented by the following Chemical Formula 1, and nanoparticles located on the surface of the core and containing a third transition metal Preparing a perovskite oxide composite catalyst comprising a;
Method for producing a perovskite oxide composite catalyst comprising:
[Formula 1]
L _x M ¹ _y M ² _{1 - y} O ₃
In Formula 1,
L is a lanthanide element,
M ¹ and M ² are different transition metals,
M ¹ is a first transition metal,
M ² is a second transition metal,
x is 0<x≤1, and y is 0<y<1. 10. The method of claim 9,
The perovskite oxide composite catalyst, characterized in that the second transition metal is doped at the lattice position of the first transition metal in the perovskite oxide. 10. The method of claim 9,
The lanthanum group element precursor includes a lanthanum precursor,
The lanthanum precursor is lanthanum nitrate hexahydrate (Lanthanum(III) nitrate hexahydrate, La(NO ₃ ) ₃ ㆍ6H ₂ O), lanthanum chloride heptahydrate (Lanthanum(III) chloride heptahydrate, LaCl ₃ ㆍ7H ₂ O) , Lanthanum(III) acetate hydrate, La(CH ₃ COO) ₃ .xH ₂ O), Lanthanum(III) nitrate hydrate, La(NO ₃ ) ₃ .xH ₂ O) and Lanthanum chloride hydrate (Lanthanum (III) chloride hydrate, LaCl ₃ ·xH ₂ O) A method for producing a perovskite oxide composite catalyst comprising at least one selected from the group consisting of. 10. The method of claim 9,
The method for producing a perovskite oxide composite catalyst, wherein the first transition metal precursor includes an iron precursor, and the second transition metal precursor includes a nickel precursor. 13. The method of claim 12,
The iron precursor is iron nitrate nonahydrate (Iron(III) nitrate nonahydrate, Fe(NO ₃ ) ₃ ·9H ₂ O), iron sulfate (Iron(II) sulfate, FeSO ₄ ) and iron chloride (Iron(III) chloride, FeCl ₃ ) comprising at least one selected from the group consisting of,
The nickel precursor is nickel nitrate hexahydrate (Nickel (II) nitrate hexahydrate, N ₂ NiO ₆ ·6H ₂ O), nickel sulfate (Nickel sulfate, NiSO ₄ ) and nickel chloride (Nickel chloride, NiCl ₂ ) selected from the group consisting of A method for producing a perovskite oxide composite catalyst comprising at least one. 10. The method of claim 9,
Method for producing a perovskite oxide composite catalyst comprising at least one selected from the group consisting of citric acid, glycine, ethylenediaminetetraacetic acid (EDTA) and polyacrylic acid (PAA) . 10. The method of claim 9,
The reduction condition is a hydrogen gas atmosphere,
The heat treatment is a method for producing a perovskite oxide composite catalyst, characterized in that carried out at a temperature of 300 to 1,000 ℃. A water gas conversion method comprising a; by performing a water gas shift reaction of carbon monoxide and water according to Reaction Equation 1 below in the presence of the perovskite complex catalyst according to claim 1 to produce carbon dioxide and hydrogen.
[Scheme 1]
CO + H ₂ O → CO ₂ + H ₂ 17. The method of claim 16,
The water gas conversion method is
(a) pre-treating the perovskite oxide composite catalyst by contacting an inert gas with the perovskite oxide composite catalyst according to claim 1; and
(b) generating carbon dioxide and hydrogen by subjecting carbon monoxide and water to a water gas shift reaction according to Scheme 1 in the presence of the pretreated perovskite oxide complex catalyst; Water gas conversion method. 18. The method of claim 17,
Water gas conversion method, characterized in that the pretreatment of step (a) is carried out at 100 to 200 ℃. 18. The method of claim 17,
Water gas conversion method, characterized in that the water gas conversion reaction of step (b) is carried out at 100 to 700 ℃. 18. The method of claim 17,
Water gas conversion method, characterized in that the inert gas comprises at least one selected from the group consisting of nitrogen gas, helium gas, neon gas, argon gas, and crito gas.

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