JP2020168588A - Manufacturing method of supported bimetal alloy - Google Patents

Abstract

The present invention provides a new and simpler synthesis method for producing a bimetallic alloy supported on a high surface area support. [Solution] A method for producing a bimetallic alloy supported on a carrier, wherein the bimetallic alloy is composed of at least one base metal (MA) and at least one noble metal (MB) [MA] x [MB ] 1-x, and the following steps: a) Adding a base metal to a solution in which a carrier is dispersed in a solvent; b) Adding a reducing agent to reduce the base metal. and c) adding a noble metal to a solution to form a bimetallic alloy on a support. [Selection diagram] None

Description

The present invention relates to a method for producing a bimetal alloy supported on a carrier having a high surface area. The bimetal alloy can be applied to various applications such as a catalyst in a heterogeneous reaction and an electrode in a fuel cell, and is particularly useful as a catalyst in low-temperature combustion of methane.

Bimetal alloys are alloys formed from two (or, in some cases, two or more) different metals, and are known to exhibit properties different from the properties of each metal component alone. In particular, bimetal alloys have unique catalytic properties, which are believed to be related to changes in electronic and geometrical structures caused by the presence of two different metal atoms in close proximity. There is.

So far, regarding the synthesis of bimetal alloys, various methods such as impregnation method, precipitation precipitation method, colloidal precipitation method, ion exchange method, electroless precipitation method, galvanic substitution reduction method, etc. can be formed to form a close interaction between metals. Methods have been studied (eg, Non-Patent Documents 1 and 2). However, as described below, these conventional methods have various drawbacks.

The impregnation method is a method in which a solution containing a dissolved metal precursor is brought into contact with a carrier, and then the solvent is removed by evaporation. This method is the most commonly used method in the preparation of supported bimetal alloys because it is a relatively simple step of adding metals simultaneously or sequentially. The impregnation method also includes performing heat treatment in hydrogen to reduce the metals after the metals are sufficiently mixed. However, it is difficult to obtain a single-phase alloy because the compositional uniformity and the interaction between the two metals cannot be controlled.

On the other hand, the precipitation-precipitation method is a method of supporting a metal compound on a carrier by using a precipitation agent in order to convert a soluble metal precursor into an insoluble form. However, this method requires strict control of the pH of the solution and the concentration of precursors to ensure co-precipitation of two different metal species on the carrier (not in solution). In addition, additional steps are required to remove the precipitant.

The colloidal precipitation method produces colloids containing bimetal particles of uniform composition and size in an aqueous or organic solvent by reducing the soluble metal precursor sequentially or simultaneously in the presence of a protective polymer to prevent adhesion. Including the step of forming. Then, the colloid is precipitated on the carrier to obtain a supported catalyst. However, one drawback of the colloidal precipitation method is that it requires high temperature treatment in O ₂ and / or H ₂ to decompose the protective polymer used, which can lead to sintering.

The ion exchange method requires the use of metal precursors that interact strongly with the carrier, which limits the functional groups (number and properties) on the carrier and the properties of the impregnated solution (pH, concentration and type of metal compound). To. In recent years, a method for synthesizing highly dispersed and fully alloyed silica-supported bimetal nanoparticles over a wide composition range has been reported (Non-Patent Document 3). The method is characterized in that the pH of the metal amine complex precursor solution is adjusted relative to the zero charge point (PZC) of silica to enhance electrostatic interaction. However, this method is limited to the use of complexes that do not hydrolyze and precipitate in solution over a wide range of pH ranges, and the total metal support that can be applied to a single synthesis cycle is limited to a few percent by weight. There are drawbacks. In particular, the amount of metal supported is lower than that of the impregnation method and the precipitation-precipitation method.

The electroless deposition (ED) method is a method for selectively precipitating a second metal salt on the surface of an activated supporting first metal by electrochemical reduction. For this technique, an electroless bath can be used to synthesize a catalyst with a bimetal surface by using a reducing agent and controlling the bath temperature and pH, and a bimetal core with a strong surface interaction between the two metals. -It has been reported that a shell structure is formed (Non-Patent Document 4 etc.). However, in the ED method, undesired nucleation of monometal particles can occur at the same time as metal precipitation unless a stable precursor complex is used in an electroless bath.

The galvanic displacement-reduction (GDR) method is a method based on a colloidal method and an electrochemical principle, and is a method for overcoming the problems inherent in the ED method. It has been reported that a bimetal compound such as PdAu can be synthesized by achieving a bimetal mixture by utilizing the difference in standard reduction potentials of two types of metal components (Non-Patent Document 5 and the like). In the GDR method, the more noble metal of the two metals is reduced in the presence of a suitable liquid phase reducing agent and protective polymer. However, in the GDR method, it is essential to use a protective polymer, and it is necessary to carry out a treatment for decomposing the protective polymer after the reaction is completed. Further, the reducing agent that can be used is limited to ethanol or ethylene glycol.

M.B. Gawande et al., Chem. Rev. 116 (2016) 3722-3811 J.A. Schwarz et al., Chem. Rev. 95 (1995) 477-510 A. Wong et al., Science 358 (2017) 1427-1430. W. Diao et al., ACS Catal. 5 (2015) 5123-5134 S. Kunz et al., J. Phys. Chem. C 118 (2014) 7468-7479

A bimetal alloy formed of a base metal and a noble metal is suitable for applications such as non-uniform catalysts and electrode catalysts, but due to the combination of such metals, the bimetal alloy can produce pure metal particles in which a part of the metal is not bonded. Since it is formed, it is difficult to synthesize it by the conventional method as described above. Therefore, the present invention provides a simpler novel synthesis method for producing a bimetal alloy suitable as a catalyst in an oxidation reaction of hydrocarbons or the like, particularly a bimetal alloy supported on a support having a high surface area. Is the subject.

As a result of diligent studies to solve the above problems, the present inventors have focused on the difference between the electrochemical potentials of the metals constituting the alloy, and by using the electrochemical interaction, phase purity (phase). A redox deposition synthesis method (RD method: redox peptide method) has been found as a novel method capable of synthesizing a −pur) bimetal alloy easily and efficiently, and the present invention has been completed. That is, in the present invention, the base metal is first reduced on the carrier, and then the noble metal is added to the reduced base metal to cause an electrochemical interaction, whereby the base metal is caused by the difference in electrochemical potential. It is characterized in that a bimetal alloy is obtained by reducing. It was also found that the bimetal alloy obtained by the production method is useful as a catalyst in the oxidation reaction (low temperature combustion) of hydrocarbons.

The present invention, in one aspect,
<1> A method for producing a bimetal alloy supported on a carrier.
The bimetallic alloy is at least one base metal _{(M A)} and at least one noble metal _{(M B)} from the configured _{[M A] x [M B} ] alloy represented by the formula _1-x, The following steps: a) adding a base metal to a solution in which the carrier is dispersed in a solvent; b) adding a reducing agent to reduce the base metal; and c) adding a noble metal to the solution and placing it on the carrier. It provides a manufacturing method including a step of forming a bimetal alloy.

In a preferred embodiment, the present invention
<2> The production method according to claim 1, further comprising the following steps d): d) the step of separating the supported bimetal alloy obtained in the step c) from the solution.
<3> The production method according to <1> or <2> above, which comprises adding a reducing agent in the step c).
<4> The production method according to any one of <1> to <3>, wherein the steps a) to c) are performed in a single pot, container, container or reactor;
<5> the base metal _{(M A)} is, Sc, Ti, V, Cr , Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Hf, Ta, W, Re, and The production method according to any one of <1> to <4>, which is selected from the group consisting of any combination thereof;
<6> The noble metal _{(M B)} is, Tc, Ru, Rh, Pd , Ag, Os, Ir, Pt, are selected from Au and the group consisting of any combination thereof, the <1> to <5> The manufacturing method according to any one of
<7> is the base metal _{(M A)} is Ni or Cu, the precious metal _{(M B)} is Pt, the production method according to any one of the above <1> to <6>;
<8> The _{[M A] x [M B} ] 1 - In _x, x is in the range of 0.01 to 0.99, The method according to any one of the above <1> to <7>;
<9> The _{[M A] x [M B} ] 1 - In _x, x is in the range of 0.10 to 0.90, The method according to the <8>;
<10> The method according to any one of the base metal total reduction potential (ΔE ^o _Total) is greater than 0V of _{(M A)} and the noble metal _{(M B),} the <1> to <9>;
<11> The production method according to any one of <1> to <10> above, wherein the amount of the bimetal alloy supported on the carrier is 0.1 to 80% by weight;
<12> The production method according to <11> above, wherein the amount of the bimetal alloy supported on the carrier is 1 to 20% by weight;
<13> A group in which the carrier consists of silica, alumina, titania, zinc oxide, tria, itria, ceria, zirconia, carbon, carbon nanotubes, magnesia, kaolin, bentonite, diatomaceous earth, silicalite, zeolite, and any combination thereof. The production method according to any one of <1> to <12> above, which is a material selected from the above;
<14> The above-mentioned <1> to <13>, wherein the carrier is a silica-containing material selected from the group consisting of silica-alumina, silica-titania, silica-magnesia, and silica-zirconia. Manufacturing method;
<15> The production method according to <13> or <14> above, wherein the silica or silica-containing material is prepared by flame hydrolysis, sol-gel method, precipitation, or condensation;
<16> The solvent is selected from the group consisting of water, alcohol, ether, ester, furano, lactone, amide, toluene, xylene, sulfolane, oxalan, N, N-dimethylformamide, and any combination thereof. The production method according to any one of <1> to <15>above;
<17> The production method according to any one of <1> to <16> above, wherein the reducing agent is hydrogen, carbon monoxide, hydrazine, lithium aluminum hydride, or sodium borohydride;
<18> The production method according to <17> above, wherein the reducing agent is sodium borohydride; and <19> Separation in step d) is performed using filtration or centrifugation. > To <18> according to any one of the above.

Moreover, in another aspect, the present invention
<20> A method of oxidizing a hydrocarbon, which comprises contacting the hydrocarbon with a bimetal alloy catalyst supported on a carrier in an oxygen-containing atmosphere; the bimetal alloy comprises at least one base metal. _{(M a)} and composed of at least one noble metal _{(M B) [M a]} x [M B] 1 - Yes an alloy represented by the formula of _x; the base metal _{(M a)} is, Sc, Selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Hf, Ta, W, Re, and any combination thereof; noble metal _{(M B)} is, Tc, Ru, Rh, Pd , Ag, Os, Ir, Pt, selected from Au and the group consisting of any combination thereof; and wherein said carrier, silica, alumina, titania, zinc oxide , Tria, Itria, Celia, Zirconia, Carbon, Carbon Nanotubes, Magnesia, Kaolin, Bentnite, Silica Soil, Silicalite, Zeolite, Materials selected from the group consisting of any combination thereof. And <21> also according to the method according to <20> above, wherein the hydrocarbon is methane.

According to the production method of the present invention, a phase-pure bimetal alloy composed of a base metal and a noble metal can be easily and efficiently synthesized by one-pot synthesis. In addition, the bimetal alloy obtained by this method can be used in applications such as heterogeneous catalysts and electrode catalysts, and can be particularly preferably used as a catalyst in the oxidation reaction (low temperature combustion) of hydrocarbons such as methane.

FIG. 1 is a schematic view of the manufacturing method of the present invention. FIG. 2 is a diagram showing a procedure for one-pot synthesis in the production method of the present invention. FIG. 3 is a graph showing powder XRD patterns of silica-supported bimetal catalysts (Examples 1-1 and 1-2) synthesized by the production method of the present invention. Ni-containing material at the time of (a) preparation and (c) reduction; (b) Cu-containing sample at the time of preparation and (d) reduction (2θ: 37.5-50 °, step size: 0.02, Scanning speed: 0.1 step / sec). FIG. 4 is a graph showing a powder XRD pattern of silica-supported bimetal catalysts (Examples 1-3 and 1-4) synthesized by the production method of the present invention. FIG. 5 is a graph showing a powder XRD pattern of silica-supported bimetal catalysts (Examples 1-5 and 1-6) synthesized by the production method of the present invention (2θ: 37.5-50 °, step. Size: 0.02, scanning speed: 0.1 steps / sec)). FIG. 6 is a graph showing a powder XRD pattern of silica-supported bimetal catalysts (Examples 1-7 and 1-8) synthesized by the production method of the present invention (2θ: 10-80 °, step size: 0.05, scanning speed: 2.0 steps / sec). FIG. 7 is a graph showing a powder XRD pattern at the time of (a) preparation and (b) reduction of a silica-supported NiPt sample (Example 4) synthesized by the production method of the present invention. FIG. 8 is a graph showing a comparison of powder XRD patterns for bimetal alloys synthesized by the production method of the present invention and the initial wet (IW) impregnation method (Comparative Example 7).

Hereinafter, embodiments of the present invention will be described. The scope of the present invention is not limited to these explanations, and other than the following examples, the scope of the present invention can be appropriately modified and implemented without impairing the gist of the present invention.

1. 1. Method for producing bimetal alloy The production method of the present invention focuses on the difference between the electrochemical potentials of the metals constituting the alloy, and uses an electrochemical interaction to obtain a base metal and a noble metal supported on the carrier. This is a novel method for synthesizing a bimetal alloy composed of a simple and efficient method (in the present specification, this may be referred to as a redox deposition synthesis method (RD method: redox peptide method)).

The production method of the present invention is characterized by including the following steps a) to c).
a) A step of adding a base metal to a solution in which a carrier is dispersed in a solvent;
b) A step of adding a reducing agent to reduce the base metal;
c) Step of adding noble metal to solution to form bimetal alloy on carrier

Here, when the supported bimetal alloy obtained in the step c) is separated and recovered and used after the step c), a step of separating the supported bimetal alloy from the reaction solution may be further performed. That is, a preferred embodiment of the present invention is the following step d) :.
d) The step of separating the supported bimetal alloy obtained in the step c) from the solution can be further included. However, when the supported bimetal alloy is formed in step c) and then used as it is as a catalyst in a specific reaction, it is not essential to carry out step d).

FIG. 1 is a schematic view of the manufacturing method of the present invention. As shown in FIG. 1, the base metal is first reduced on the carrier (FIG. 1 (a)), and then the noble metal is added to the reduced base metal to cause an electrochemical interaction (FIG. 1 (b)). A bimetal alloy is obtained by reducing the noble metal by the base metal due to the difference in electrochemical potential (in other words, the base metal is oxidized to a metal ion) (FIG. 1 (c)). Then, the supported bimetal alloy can be obtained by separating the carrier supporting the obtained bimetal alloy from the solution and recovering it.

Bimetallic alloy obtained in the present invention, at least one base metal _{(M A)} and composed of at least one noble metal _{(M B) [M A]} x [M B] 1 - Formula of _x ..

Here, in this specification, base metal _{(M A)} has a noble metal _{(M B)} lower standard reduction potential than ^(E _{o M).} Base metal _{(M A)} is typically less than + 0.4V, preferably having a negative standard reduction potential, the noble metal _{(M B)} is typically positive standard reduction potentials, preferably +0. It has a standard reduction potential of 4v or higher. From another perspective, a base metal _{(M A)} and the total reduction potential of the noble metal ^{_{(M B) (ΔE o Total}} ) is preferably larger than 0V.

Table 1 shows the electrochemical properties of transition metals as standard reduction potentials (E ^o _M ). The standard reduction potential in the table is a value with respect to the standard hydrogen electrode. The more negative the reduction potential is, the stronger the reducing power is. For example, it can be seen that yttrium (Y), which has an E ^o _M of -2.37 V, can reduce other elements. It is shown that the noble metals (Tc, Ru, Rh, Pd, Ag, Os, Ir, Pt, Au) shown in shading all have a positive reduction potential and can be reduced by base metal elements. There is.

In the present invention, a base metal _{(M A)} is preferably, Sc, Ti, V, Cr , Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Hf, Ta, W, A transition metal selected from the group consisting of Re and any combination thereof. More preferably, it is selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, and any combination thereof. More preferably, it is selected from the group consisting of Fe, Co, Ni, Cu, and any combination thereof. Most preferably, it is selected from the group consisting of Ni, Cu, and any combination thereof.

In the present invention, the noble metal _{(M B)} is preferably a transition metal selected Tc, Ru, Rh, Pd, Ag, Os, Ir, Pt, Au, and the group consisting of any combination thereof. More preferably, it is selected from the group consisting of Rh, Pd, Ir, Pt, and any combination thereof. More preferably, it is selected from the group consisting of Pd, Pt, and any combination thereof. Most preferably, the noble metal _{(M B)} is Pt.

As described above, the bimetal alloy obtained by the present _{invention, [M A] x [M} B] 1 - is represented by the formula _x, preferably, in the formula x is 0.01 to 0.99 The range. More preferably, x is in the range of 0.05 to 0.95. More preferably, x is in the range of 0.10 to 0.90. Within such a range, the catalytic activity of the bimetal alloy can be controlled.

The supported bimetal alloy obtained in the present invention preferably has a supported amount of the bimetal alloy on the carrier of 0.1 to 80% by weight. More preferably, the amount of the bimetal alloy supported on the carrier is 0.5 to 40% by weight. More preferably, the amount of the bimetal alloy supported on the carrier is 1 to 20% by weight. Within this range, the balance between catalytic activity and dispersibility in the solution can be adjusted.

The bimetal alloy supported on the carrier can be in the form of particles or surface phases. For example, when the bimetal alloy is a particle, it can have a particle size of 0.5 nm to 5 μm. By supporting the alloy on the carrier in this way, the alloy can be efficiently dispersed on the surface of the carrier, the surface property can be increased as compared with the alloy in bulk form, and better catalytic performance can be provided. It will be possible.

In step a) of the present invention, a base metal is added to a solution containing a carrier to deposit the base metal on the carrier. The carrier used is preferably a material having a high surface area, where "high surface area" typically means a surface area of 10 m ² / g, preferably 20 m ² / g or more. Specific examples of such carriers include silica, alumina, titania, zinc oxide, tria, itria, ceria, zirconia, carbon, carbon nanotubes, magnesia, kaolin, bentonite, diatomaceous earth, silicalite, zeolite, and any combination thereof. It can, but is not limited to these.

Preferably, the carrier can be a silica-containing material, and examples of such silica-containing materials include silica-alumina, silica-titania, silica-magnesia, or silica-zirconia. Further, the silica or silica-containing material can be a material prepared by flame hydrolysis, sol-gel method, precipitation, or condensation.

The solvent used in step a) is selected from the group consisting of water, alcohol, ether, ester, furano, lactone, amide, toluene, xylene, sulfolane, oxalan, N, N-dimethylformamide, and any combination thereof. The solvent can be, but is not limited to.

The step b) of the present invention is a step of adding a reducing agent to the solution containing the base metal supported on the carrier in the step a) to reduce the base metal. The reducing agent used in step b) is a vapor phase reducing agent such as hydrogen, carbon monoxide or any combination thereof: or a liquid phase such as hydrazine, lithium aluminum hydride, or sodium borohydride (NaBH ₄ ). A reducing agent can be used, but other reducing agents known in the art can also be used. The reducing agent is preferably hydrazine, lithium aluminum hydride, or sodium borohydride, and more preferably sodium borohydride.

Step c) of the present invention is a step of adding a noble metal to the solution containing the supported base metal reduced in step b). As described above, due to the difference in electrochemical potential, a reaction in which a base metal reduces a noble metal occurs, and a bimetal alloy is formed. In one aspect, a reducing agent may be further added in step c). The reducing agent is the same as that mentioned in step b) above.

The step d) of the present invention is a step of separating and recovering the obtained supported bimetal alloy, and is an arbitrary step that can be performed when desired as described above. The separation operation can be performed using filtration or centrifugation. In order to remove the residual solvent, the recovered supported bimetal alloy may be dried.

The metal added in steps a) and c) can be in the form of ammonium salts, chlorides, nitrates, hydroxides, carbonyls, acetylacetonates, heteropoly compounds and the like. The metal can be added in the form of a solution in which these metal salts are dissolved, and the concentration at that time is not particularly limited and can be appropriately selected.

It will be apparent to those skilled in the art that there are numerous variations of this method. A plurality of impregnation steps can be performed, in which case a solution containing one or more component precursors can be impregnated. It is also possible to use impregnation, dipping, or spraying methods instead of immersing the support in the solution. Similarly, there may be various variations on the method of separating, drying and redistributing the catalyst.

Further, as will be apparent to those skilled in the art, the bimetal alloy obtained by the method of the present invention may be an alloy composed of three or more metal components, or may contain one or more additives. It can also be. For example, an accelerator for improving the activity, selectivity, stability, etc. of the catalyst is known in the art, and such an accelerator can be added. Examples include alkali metals, alkaline earth metals, halides, and compounds containing elements such as boron, carbon, nitrogen, aluminum, sulfur, gallium, germanium, arsenic, tin, antimony, bismuth, selenium, and tellurium. it can.

2. Reaction mechanism and specific procedure example of the production method of the present invention The production method of the present invention also has an advantage that it can be synthesized in a so-called one-pot in a single container.

FIG. 2 shows an example of a non-limiting procedure in one-pot synthesis by the production method of the present invention. First, silica (SiO ₂ ) is suspended as a carrier in a reaction vessel containing distilled water or deionized water (FIG. 2 (1)). Subsequently, the precursor of the base metal (e.g., NiCl ₂ · 6H ₂ O and CuCl ₂ · _2H 2 O) was added an aqueous solution of, providing a source of dissociated base metal ion ^{(Ni 2+} or ^{Cu 2+)} (FIG. 2 (2)). A stoichiometric reducing agent (eg, NaBH ₄ ) is then added into the solution under an Ar atmosphere. As a result, clusters of base metal particles (Ni or Cu particles), some of which are adhered to silica, are formed (FIG. 2 (3)).

The next step, the noble metal precursor to the solution containing the base metals metal clusters _{(e.g., H 2 PtCl 6 · 6H 2} O) is added to (FIG. 2 (4)). The noble metal precursor dissociates into noble metal ions (platinum chloride ion: [PtCl ₆ ] ^2- ) and is then reduced by the base metal.

The mechanism of the redox reaction in these series of steps is shown below by taking Ni (base metal) and Pt (precious metal) as examples. The following formula represents the reduction of [PtCl ₆ ] ^2- ion to metal Pt by metal Ni, and the standard electrode potential with respect to the standard hydrogen electrode (SHE) is shown in parentheses.

The total reduction potential (ΔE ^o _Total ) of the NiPt system in the reaction is larger than zero (ΔE ^o _Total = +1.68V), which is preferable for the reaction to proceed. Therefore, as described above, a base metal _{(M A)} and the total reduction potential of the noble metal _{^{(M B) (ΔE o Total}} ) is preferably larger than 0V.

As described above, the combination of the base metal and the noble metal causes the bimetal alloy to form pure metal particles in which a part of the metal is not bonded, so that it is difficult to synthesize by the conventional method. According to the method of the present invention, such a base metal-noble metal bimetal alloy can be easily and efficiently synthesized in a mode of being supported on a carrier. Although a base metal component can be used in the conventional GDR method, the use of a protective polymer is indispensable, whereas in the method of the present invention, it is not necessary to use such a protective polymer, and a treatment for decomposing the polymer after the reaction, etc. Is unnecessary. Further, in the GDR method, the use of ethanol or ethylene glycol as a reducing agent was indispensable, but there is no such limitation in the present invention.

3. 3. Application to Hydrocarbon Oxidation Reaction As described above, the supported bimetal alloy obtained by the production method of the present invention can be used in applications such as heterogeneous catalysts and electrode catalysts, and in particular, oxidation of hydrocarbons such as methane. It has been found that it is suitable as a catalyst in the reaction (low temperature combustion).

Therefore, in another embodiment, the present invention comprises a method of oxidizing a hydrocarbon, which comprises contacting the hydrocarbon with a bimetal alloy catalyst supported on a carrier in an oxygen-containing atmosphere. Also related. Here, the bimetal alloy catalyst used is a base metal-noble metal bimetal alloy supported on a carrier having a high surface area, and the details are as described above.

Examples of the hydrocarbon to be oxidized include compounds such as methane, ethane, ethylene, propane, propylene, butane, butane, cyclohexane, and benzene, and methane is preferable.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

Example 1. Synthesis of various bimetal alloys
[Example 1-1] Synthesis of bimetal alloy (NiPt / SiO ₂ )
Ni while maintaining silica supported _{M A M B (M A =} Ni, M B = Pt) with different molar ratios bimetallic alloy catalyst and a constant amount of supported Pt 2 wt% (0.10 mmol / g carrier) Prepared by varying the amount of. The samples are NiPt (4: 1), NiPt (2: 1), and NiPt (1: 1), and the numbers in parentheses are molar ratios. The catalyst was prepared using the one-pot synthesis (redox deposition method) shown in FIG. First, 2.5 g of silica (41.6 mmol) was dispersed in 100 mL of deionized water and stirred at 400 rpm for 10 minutes. Then, based on a predetermined molar ratio of NiPt shown in Table 2, was dissolved suitable amount of NiCl ₂ · _6H 2 O and (0.25~1.0mmol) of deionized water 15 mL, stirred continuously While added to the silica / water mixture. The inside of the reaction vessel was continuously purged with argon. A stoichiometric amount of NaBH ₄ (0.51 to 2.0 mmol) dissolved in 15 mL of deionized water was added to reduce the Ni precursor. When the solution was added dropwise to the mixture under Ar, the color changed from green to black. After stirring for 1.5 _hours, added slowly H ₂ PtCl ₆ · 6H 2 O aqueous solution (0.25 mmol) to the suspension and stirred for 1.5 hours under Ar atmosphere. Solid samples were collected by filtration and washed several times to remove sodium, chlorine, and boron ions. The solid sample was then dried at 110 ° C. overnight, then pelletized and sieved to a size of 650-1180 μm. Finally, the catalyst was reduced under hydrogen at 400 ° C. for 2 hours (1000 cm ³ min- ¹ g- ¹ _catalyst ) and then passivated under 0.2% O ₂ / He flow for 3 hours (100 cm ³ min). ^-1 · g ^-1 _catalyst ). In addition, IW in the table is a comparative example using the initial wet impregnation method.

[Example 1-2] Synthesis of bimetal alloy (CuPt / SiO ₂ )
Using the same method as in Example 1-1, while maintaining the amount of supported Pt constant at 2 wt% (0.10 mmol / g carrier), silica supported with different molar ratios _M A _M B _(M A = _Cu, was prepared M B = Pt) bimetallic catalyst. The samples are CuPt (4: 1), CuPt (2: 1), and CuPt (1: 1), and the numbers in parentheses are molar ratios. The one-pot synthesis (redox deposition method) shown in FIG. 2 was used in the same manner as in Example 1-1. First, 2.5 g of silica (41.6 mmol) was dispersed in 100 mL of deionized water and stirred at 400 rpm for 10 minutes. Then, based on a predetermined molar ratio of CuPt shown in Table 3, was dissolved an appropriate amount of _{CuCl 2 · 2H 2 O (0.25~1.0mmol} ) of deionized water 15 mL, silica under continuous agitation / Added to water mixture. The inside of the reaction vessel was continuously purged with argon. To reduce the Cu precursor, stoichiometric amounts of NaBH ₄ (0.51 to 2.0 mmol) dissolved in 15 mL of deionized water were used. When the solution was added dropwise to the mixture under Ar, the color changed from pale blue to wine red. After stirring for 1.5 _hours, added slowly H ₂ PtCl ₆ · 6H 2 O aqueous solution (0.25 mmol) to the suspension and stirred 1.5 h under Ar atmosphere. Solid samples were collected by filtration and washed several times to remove sodium, chlorine, and boron ions. The solid sample was then dried at 110 ° C. overnight, then pelletized and sieved to a size of 650-1180 μm. Finally, the catalyst was reduced under hydrogen at 400 ° C. for 2 hours (1000 cm ³ min- ¹ g- ¹ _catalyst ) and then passivated under 0.2% O ₂ / He flow for 3 hours (100 cm ³ min). ^-1 · g ^-1 _catalyst ).

[Example 1-3] Synthesis of bimetal alloy (NiIr / SiO ₂ ) Using the same method as in Example 1-1, the amount of Ir carried was kept constant at 2% by weight (0.10 mmol / g carrier). while, silica-supported _{M a M B (M a =} Ni, M B = Ir) with different molar ratios were prepared bimetallic catalyst. The samples are NiIr (8: 1), NiIr (6: 1), NiIr (4: 1), NiIr (2: 1), and NiIr (1: 1), and the numbers in parentheses are molar ratios. .. The one-pot synthesis (redox deposition method) shown in FIG. 2 was used in the same manner as in Example 1-1. First, 2.5 g of silica (41.6 mmol) was dispersed in 100 mL of deionized water and stirred at 400 rpm for 10 minutes. Then, based on a predetermined molar ratio of NiIr shown in Table 4, it was dissolved an appropriate amount of _{NiCl 2 · 6H 2 O (0.26~2.1mmol} ) in deionized water, the silica / water under continuous stirring Added to the mixture. The inside of the reaction vessel was continuously purged with argon. To reduce the Ni precursor, stoichiometric amounts of NaBH ₄ (0.52-4.2 mmol) dissolved in deionized water were used. When the solution was added dropwise to the mixture under Ar, the color changed from pale blue to wine red. After stirring for 1.5 _hours, added slowly H 2 IrCl ₆ solution of (0.26 mmol) to the suspension and stirred 1.5 h under Ar atmosphere. Solid samples were collected by filtration and washed several times to remove sodium, chlorine, and boron ions. The solid sample was then dried at 110 ° C. overnight, then pelletized and sieved to a size of 650-1180 μm. Finally, the catalyst was reduced under hydrogen at 400 ° C. for 2 hours (1000 cm ³ min- ¹ g- ¹ _catalyst ) and then passivated under 0.2% O ₂ / He flow for 3 hours (100 cm ³ min). ^-1 · g ^-1 _catalyst ).

Using the same procedure as Synthesis Example 1-1 Example 1-4] bimetallic alloy (NiRh / SiO _2), while maintaining the loading amount of Rh constant, silica-supported with different molar ratios _M A M _{B (M a = Ni, M} B = Rh) was prepared bimetallic catalyst. The samples are NiRh (8: 1), NiRh (6: 1), NiRh (4: 1), NiRh (2: 1), and NiRh (1: 1), and the numbers in parentheses are molar ratios. .. The one-pot synthesis (redox deposition method) shown in FIG. 2 was used in the same manner as in Example 1-1.

[Example 1-5] Synthesis of bimetal alloy (CoPt / SiO ₂ ) Using the same method as in Example 1-1, the amount of Pt supported is kept constant at 2 wt% (0.10 mmol / g carrier). while, silica supported _{M a M B (M a =} Co, M B = Pt) molar ratios are different bimetallic catalyst was prepared. Samples are shown as CoPt (4: 1), CoPt (2: 1), and CoPt (1: 1), and the numbers in parentheses are molar ratios. The preparation was prepared using the same order as the one-pot redox deposition method shown in FIG. First, 2.5 g of silica (41.6 mmol) was dispersed in 100 mL of deionized water and stirred at 400 rpm for 10 minutes. Then, based on the desired molar ratio of CoPt shown in Table 6, it was dissolved an appropriate amount of CoCl ₂ · _{6H 2} O and (0.25-1.0 mmol) of deionized water 15 mL, and continuously It was added to the silica / water mixture with stirring. The system was continuously purged with argon. To reduce the Co precursor, stoichiometric amounts of NaBH ₄ (0.51 to 2.0 mmol) dissolved in 15 mL of deionized water were used. When the solution was added dropwise to the mixture under Ar, the color changed from light brown to black. After stirring for 1.5 _hours, slowly adding an aqueous solution of _{H 2 PtCl 6 · 6H 2 O} (0.25mmol) to the suspension and stirred for 1.5 hours under Ar atmosphere. Solid samples were collected by filtration and washed several times to remove sodium, chlorine, and boron ions. The solid sample was then dried at 110 ° C. overnight, then pelletized and sieved to a size of 650-1180 μm. Finally, the catalyst was reduced under hydrogen at 400 ° C. for 2 hours (1000 cm ³ min- ¹ g- ¹ _catalyst ) and then passivated under 0.2% O ₂ / He flow for 3 hours (100 cm ³ min). ^-1 · g ^-1 _catalyst ).

[Example 1-6] Synthesis of bimetal alloy (FePt / SiO ₂ ) Using the same method as in Example 1-1, the amount of Pt supported was kept constant at 2% by weight (0.10 mmol / g carrier). while, silica-supported _{M a M B (M a =} Fe, M B = Pt) with different molar ratios were prepared bimetallic catalyst. The samples are FePt (4: 1), FePt (2: 1), and FePt (1: 1), and the numbers in parentheses are molar ratios. The one-pot synthesis (redox deposition method) shown in FIG. 2 was used in the same manner as in Example 1-1. First, 2.5 g of silica (41.6 mmol) was dispersed in 100 mL of deionized water and stirred at 400 rpm for 10 minutes. Then, based on a predetermined molar ratio of FePt shown in Table 7, was dissolved an appropriate amount of _{FeCl 2 · 4H 2 O (0.25~1.0mmol} ) of deionized water 15 mL, silica under continuous agitation / Added to water mixture. The inside of the reaction vessel was continuously purged with argon. To reduce the Fe precursor, stoichiometric amounts of NaBH ₄ (0.51 to 2.0 mmol) dissolved in 15 mL of deionized water were used. When the solution was added dropwise to the mixture under Ar, the color changed from light brown to black. After stirring for 1.5 _hours, added slowly H ₂ PtCl ₆ · 6H 2 O aqueous solution (0.25 mmol) to the suspension and stirred 1.5 h under Ar atmosphere. Solid samples were collected by filtration and washed several times to remove sodium, chlorine, and boron ions. The solid sample was then dried at 110 ° C. overnight, then pelletized and sieved to a size of 650-1180 μm. Finally, the catalyst was reduced under hydrogen at 400 ° C. for 2 hours (1000 cm ³ min- ¹ g- ¹ _catalyst ) and then passivated under 0.2% O ₂ / He flow for 3 hours (100 cm ³ min). ^-1 · g ^-1 _catalyst ).

[Example 1-7] Synthesis of bimetal alloy (NiPd / SiO ₂ ) Using the same method as in Example 1-1, the amount of Pd supported was kept constant at 2% by weight (0.10 mmol / g carrier). while, silica-supported _{M a M B (M a =} Ni, M B = Pd) with different molar ratios were prepared bimetallic catalyst. The samples are NiPd (4: 1), NiPd (2: 1), and NiPd (1: 1), and the numbers in parentheses are molar ratios. The one-pot synthesis (redox deposition method) shown in FIG. 2 was used in the same manner as in Example 1-1. First, 2.5 g of silica (41.6 mmol) was dispersed in 100 mL of deionized water and stirred at 400 rpm for 10 minutes. Then, based on a predetermined molar ratio of NiPd shown in Table 8, was dissolved an appropriate amount of _{NiCl 2 · 6H 2 O (0.47~1.88mmol} ) of deionized water 20 mL, silica under continuous agitation / Added to water mixture. The inside of the reaction vessel was continuously purged with argon. To reduce the Ni precursor, stoichiometric amounts of NaBH ₄ (0.94 to 3.76 mmol) dissolved in 20 mL of deionized water were used. When the solution was added dropwise to the mixture under Ar, the color changed from green to black. After stirring for 1.5 hours, added slowly _Pd a _{(NH 3) 2 Cl 2 H} 2 O solution (0.47 mmol) to the suspension and stirred 1.5 h under Ar atmosphere. Solid samples were collected by filtration and washed several times to remove sodium, chlorine, and boron ions. The solid sample was then dried at 110 ° C. overnight, then pelletized and sieved to a size of 650-1180 μm. Finally, the catalyst was reduced under hydrogen at 400 ° C. for 2 hours (1000 cm ³ min- ¹ g- ¹ _catalyst ) and then passivated under 0.2% O ₂ / He flow for 3 hours (100 cm ³ min). ^-1 · g ^-1 _catalyst ).

[Example 1-8] Synthesis of bimetal alloy (CuPd / SiO ₂ ) Using the same method as in Example 1-1, the amount of Pd supported was kept constant at 2% by weight (0.10 mmol / g carrier). while, silica-supported _{M a M B (M a =} Cu, M B = Pd) with different molar ratios were prepared bimetallic catalyst. The sample is CuPd (4: 1), and the numbers in parentheses are molar ratios. The one-pot synthesis (redox deposition method) shown in FIG. 2 was used in the same manner as in Example 1-1. First, 2.5 g of silica (41.6 mmol) was dispersed in 100 mL of deionized water and stirred at 400 rpm for 10 minutes. Then, based on a predetermined molar ratio of CuPd shown in Table 9, was dissolved an appropriate amount of _{CuCl 2 · 2H 2 O (1.88mmol} ) in deionized water 20 mL, silica / water mixture under continuous stirring Was added. The inside of the reaction vessel was continuously purged with argon. To reduce the Cu precursor, stoichiometric amounts of NaBH ₄ (3.76 mmol) dissolved in 20 mL of deionized water were used. When the solution was added dropwise to the mixture under Ar, the color changed from pale blue to wine red. After stirring for 1.5 hours, added slowly _Pd a _{(NH 3) 2 Cl 2 H} 2 O solution (0.47 mmol) to the suspension and stirred 1.5 h under Ar atmosphere. Solid samples were collected by filtration and washed several times to remove sodium, chlorine, and boron ions. The solid sample was then dried at 110 ° C. overnight, then pelletized and sieved to a size of 650-1180 μm. Finally, the catalyst was reduced under hydrogen at 400 ° C. for 2 hours (1000 cm ³ min- ¹ g- ¹ _catalyst ) and then passivated under 0.2% O ₂ / He flow for 3 hours (100 cm ³ min). ^-1 · g ^-1 _catalyst ).

Example 2. Evaluation of bimetal alloys by X-ray analysis

[Example 2-1] Evaluation of (NiPt / SiO ₂ ) and (CuPt / SiO ₂ ) Bimetal Alloys Bimetal alloys (NiPt / SiO ₂ and CuPt / SiO ₂ ) synthesized in Examples 1-1 and 1-2. The phase purity was confirmed by X-ray diffraction analysis. The measurements were carried out using a CuKα monochromatic X-ray source and a diffractometer (Rigaku RINT 2400) operating at 40 kV and 100 mA. The crystallite size (D _c ) of the reduction catalyst is the Scherrer equation:
D _c = Kλ / βcos (θ)
Was calculated from the line width of the strongest peak at 2θ = 9.9 to 41.8 ° (111). Here, K is a constant of 0.9, λ is the wavelength of X-ray radiation (0.1541 nm), and β is the width of the (111) peak at the full width at half maximum corrected for the spread of the device (0.1 °). (Full width at half maximum), and θ is the Bragg angle of the (111) peak.

FIG. 3 shows an XRD pattern for the bimetal alloys (NiPt / SiO ₂ and CuPt / SiO ₂ ) synthesized in Examples 1 and 2, respectively. H ₂ diffraction pattern of a single metal Ni before reduction did not show any peak, suggesting the formation of small crystallites or amorphous particles are not detected by XRD (Figure 3 (a)). In contrast, the pattern of single metal Cu before reduction (FIG. 3 (b)) shows the (111) plane reflection (PDF # 04-0836) in the face-centered cubic (fcc) of Cu and the (200) plane of Cu2O (200). Peaks were shown at 2θ = 43.3 ° and 42.3 ° corresponding to PDF # 78-2076). The presence of metallic Cu and partially reduced Cu ₂ O indicates that Cu was reduced more easily than Ni. The diffraction patterns of the single metal Pt before reduction (FIGS. 3 (a) and 3 (b)) correspond to the (111) and (200) planes (PDF # 04-0802) of fcc Pt at 2θ = 39.7 ° and 46.2 °. Showed a peak in. Diffraction patterns for NiPt and CuPt catalysts before reduction (FIGS. 3 (a) and 3 (b)) showed a clear shift to higher 2θ values compared to those for monometal Pt. The shift to higher angles provides evidence of alloy formation even before the reduction process. The shift to a higher angle coincides with the smaller metal radius of Ni (125 μm) or Cu (128 μm) compared to the metal Pt (139 μm), causing contraction of the Pt lattice structure and thus an increase in diffraction angle. cause. The formation of NiPt and CuPt alloys at room temperature is due to reduction due to the selective redox of Pt by Ni and Cu. From FIGS. 3 (a) and 3 (b), it can be seen that as the Pt lattice constant decreases, the shift increases as the Ni or Cu content increases (Table 4).

3 (c) and 3 (d) show the diffraction pattern of the sample after hydrogen reduction at 400 ° C. The single metal Ni pattern (FIG. 3 (c)) shows a peak at 2θ = 45.5 ° C. corresponding to the (111) plane reflection of the fcc Ni metal, and the single metal Cu after H ₂ reduction at 400 ° C. The pattern (FIG. 3 (d)) showed a peak at 2θ = 43.3 °, which corresponds to the (200) plane reflection in the fcc Cu metal. Similarly, the diffraction pattern of a single metal Pt after _{H 2} reduction at 400 ° C. (FIG. 3 (c), (d)) is, 2 [Theta] = 39.7 ° corresponding to (111) and (200) plane in the fcc And peaked at 46.2 °. For NiPt samples, the diffraction peaks became sharper and shifted towards higher diffraction angles. The sharpening of the diffraction peak indicates the growth of metal particles by heat treatment, which also favors alloy formation. This behavior was also observed for the Cupt system (Fig. 3 (d)). The heat treatment of the sample increases the contribution of the mixture to the entropy and favors alloy formation.

Table 10 shows the lattice constants of the catalyst after reduction using the XRD peak positions of the (111) plane and the (200) plane of the catalyst synthesized by the method (RD method) and the IW method (initial wet impregnation method) of the present invention. It is shown. Using the lattice constant, the lattice shrinkage in the bimetal alloy was calculated in comparison with the single metal Pt.

The lattice shrinkage of the NiPt sample decreased in the order of NiPt (4: 1)> NiPt (2: 1)> NiPt (1: 1). The lattice shrinkage of NiPt (4: 1) and NiPt (IW) was similar, but their shrinkage values were higher than those of NiPt (2: 1) and NiPt (1: 1). The lattice shrinkage of the CuPt catalyst tended to be the same as that of NiPt: CuPt (4: 1)> CuPt (2: 1)> CuPt (1: 1). There is a large difference in lattice shrinkage between NiPt and CuPt samples. It is considered that this is because the radius of Ni (125 μm) is farther from Pt (139 μm) than Cu (128 μm), which limits the movement of Ni atoms due to diffusion in Pt.

[Example 2-2] Evaluation of (NiIr / SiO ₂ ) and (NiRh / SiO ₂ ) Bimetal Alloys Bimetal alloys synthesized in Examples 1-3 and 1-4 using the same method as in Example 2-1. The phase purity of (NiIr / SiO ₂ and NiRh / SiO ₂ ) was confirmed by X-ray diffraction analysis. The synthesized alloy catalyst was reduced at 400 ° C. for 2 hours and then subjected to passivation treatment. Then, the X-ray diffraction (XRD) pattern was measured using an X-ray diffractometer (Rigaku RINT 2400).

4 (a) and 4 (b) show XRD patterns for (NiIr / SiO ₂ ) and (NiRh / SiO ₂ ), respectively.

FIG. 4A showing the X-ray diffraction pattern of the NiIr / SiO ₂ sample is indexed into the face-centered cubic lattice of Ir. In the XRD profile, the Ir (1 11) peak shifted to the right as the Ni content increased. This indicates that the unit cell size is reduced and is consistent with the metal radii of Ir (127 pm) and Ni (115 pm). The peak shift is consistent with alloy formation.

Similarly, FIG. 4B showing the X-ray diffraction pattern of the NiRh / SiO ₂ sample is indexed into the face-centered cubic lattice of Rh. In the XRD profile, the Rh (1 11) peak shifted to the right as the Ni content increased. This indicates that the unit cell size has decreased, which is consistent with the metal radii of Rh (183 pm) and Ni (115 pm). The shift distance was small as compared with NiIr / SiO ₂ . This is evidence of the formation of the Ni—Rh alloy.

The crystallite size (nm) of NiIr / SiO ₂ and NiRh / SiO ₂ was calculated using Scheller's formula. The crystallite size of each sample is shown in Table 11. There was a general tendency for the crystallite size to decrease as the amount of nickel increased.

[Example 2-3] Evaluation of (CoPt / SiO ₂ ) and (FePt / SiO ₂ ) Bimetal Alloys Bimetal alloys synthesized in Examples 1-5 and 1-6 using the same method as in Example 2-1. The phase purity of (CoPt / SiO ₂ and FePt / SiO ₂ ) was confirmed by X-ray diffraction analysis. 5 (a) to 5 (d) show XRD patterns for (CoPt / SiO ₂ ) and (FePt / SiO ₂ ), respectively.

The diffraction patterns of the single metal Pt before reduction (FIGS. 5A and 5B) correspond to the (111) and (200) planes of the face-centered cubic lattice structure Pt at 2θ = 39.7 ° and 46.2. It showed a peak at ° (PDF # 04-0802). Diffraction patterns for CoPt and FePt catalysts before reduction (FIGS. 5 (a) and 5 (b)) showed a clear shift to higher 2θ values compared to those for single metal Pt. The shift to higher angles provides evidence of alloy formation even before the reduction process. The shift to a higher angle coincides with the smaller metal radius of Co (125 pm) or Fe (126 pm) compared to the metal Pt (139 pm), causing contraction of the Pt lattice structure and thus the diffraction angle. Was found to cause an increase in. The formation of CoPt and FePt alloys at room temperature is due to the reduction of Pt by selective redox driving with Co and Fe. In both FIGS. 5A and 5B, it is shown that the shift increases as the Co or Fe content increases.

On the other hand, FIGS. 5 (c) and 5 (d) show the diffraction pattern of the sample after hydrogen reduction at 400 ° C. 400 ° C. in the _{H 2} diffraction pattern of a single metal Pt after reduction (FIG. 5 (c) and (d)) is a face-centered cubic lattice structure Pt (111) and (200) corresponding to the surface 2 [Theta] = 39. It peaked at 7 ° and 46.2 °. For CoPt and FePt samples, the diffraction peaks became sharper and shifted towards higher diffraction angles. The sharpening of the diffraction peak indicates the growth of metal particles by heat treatment, which also favors alloy formation. This behavior is also observed with NiPt and CuPt (FIGS. 3 (c) and 3 (d)). The heat treatment of the sample is believed to increase the contribution of the mixture to entropy and favor alloy formation.

[Example 2-4] Evaluation of (NiPd / SiO ₂ ) and (CuPd / SiO ₂ ) Bimetal Alloys Further, the bimetal alloys (NiPd / SiO ₂ and CuPd / SiO ₂ ) synthesized in Examples 1-7 and 1-8 ), The phase purity thereof was confirmed by X-ray diffraction analysis using the same method as in Example 2-1. 6 (a) and 6 (b) show XRD patterns for (NiPd / SiO ₂ ) and (CuPd / SiO ₂ ), respectively.

According to FIGS. 6 (a) and 6 (b), the diffraction pattern of the single metal Pd corresponds to the (111), (200) and (220) planes in the face-centered cubic lattice structure Pd at 2θ = 40.1 °, It peaked at 46.7 ° and 68.1 ° (PDF # 05-0681). The diffraction patterns of NiPd and CuPd showed a clear shift to higher 2θ values compared to those of single metal Pd. The shift to higher angles provides evidence of alloy formation. The shift to a higher angle coincides with the smaller metal radius of Ni (125 pm) or Cu (128 pm) compared to the metal Pd (137 pm), causing contraction of the Pd lattice structure and thus an increase in diffraction angle. It turned out.

Example 3. Evaluation of bimetal alloys by X-ray fluorescence
The metal content of the prepared NiPt / SiO ₂ and CuPt / SiO ₂ catalysts was determined by X-ray fluorescence (XRF) spectroscopy using Shimadzu Rayny EDX-800HS. The results are shown in Table 12. It can be seen that the contents of Ni, Cu, and Pt are slightly lower than expected compared to the theoretical value of the supported amount (nominal) (here, the theoretical supported amount is the supported amount calculated from the molar amount of the catalyst metal). Is). This result indicates that almost all single metals were supported on the carrier. The samples labeled NiPt (IW) and CuPt (IW) are comparative example samples prepared by the initial wet (IW) impregnation method described in Example 7.

Example 4. Silica-supported NiPt bimetal using the same method as in Example 1-1 except that additional NaBH ₄ was added in the step of synthetic redox precipitation of NiPt ^* / SiO ₂ using an additional reducing agent (NaBH ₄ ). An alloy was prepared. The step was performed to reduce all Ni and Pt ions dissolved in the solution. These samples are labeled NiPt (4: 1) ^* , NiPt (2: 1) ^* , and NiPt (1: 1) ^* . For example, to prepare NiPt (4: 1) ^* , catalyst NaBH ₄ (1.0 mmol) sufficient to reduce all dissolved Ni metal ions in solution after synthesis of NiPt (4: 1). It was added to the solution (Table 6). The synthesis of NiPt (4: 1) was started with 1.0 mmol Ni to reduce 0.25 mmol Pt ions, so in the process 0.50 mmol Ni metal was oxidized to Ni 2+ ions and 0. .25 mmol of Pt ⁴⁺ ions were reduced (2 mol of Ni to reduce 1 mol of Pt ions). To reduce the ^{Ni 2+} ions of these 0.50 mmol, 1.0 mmol amount of NaBH 4 was added to the catalyst solution ^{_{(Ni 2+ + 2BH 4 - +}} 6H 2 O

Ni + 2H ₃ BO ₃ + 7H ₂ ). Similarly, NiPt (2: 1) ^* and NiPt (1: 1) ^* samples were prepared (Table 13).

Example 5. Evaluation of NiPt ^* / SiO ₂ by X-ray Analysis The NiPt ^* / SiO ₂ bimetal alloy obtained in Example 4 was evaluated in the same manner as in Example 3. FIG. 7 shows a comparison between the XRD pattern of the NiPt ^* / SiO ₂ bimetal alloy obtained in Example 4 and the NiPt bimetal alloy of Example 1-1. The shift from the position of the Pt metal to higher angles on the as-prepared and reduced NiPt ^* samples was greater than with NiPt. Since the driving force for alloy formation is the increase in entropy due to atomic mixing, the increase in the shift to higher angles is thought to be due to the readsorbed Ni in the formation of the NiPt ^* alloy.

Example 6. Evaluation of NiPt ^* / SiO ₂ by XRF Measurement The NiPt ^* / SiO ₂ bimetal alloy obtained in Example 4 was evaluated in the same manner as in Example 3. It was found that the Ni and Pt contents were higher than the content of the NiPt sample of Example 1-1 prepared without excess NaBH ₄ and close to the expected theoretical values, compared to the theoretical loading. (Table 14).

Comparative example 7. Preparation and evaluation of comparative examples by the initial wet impregnation method The impregnation method mixes the precursor solution while mixing with a prior careful measurement of the amount of solution required to ensure that the support is just sufficiently wetted by the solution. It is a method of slowly adding to a solid support. Therefore, it is also called an initial wet (IW) impregnation method. Comparative example samples represented by silica-supported bimetal NiPt (IW) and CuPt (IW) were prepared by conventional co-impregnation using the initial wetting (IW) method. The metal loading was selected to be consistent with the XRF measurements for the NiPt (4: 1) and CuPt (4: 1) catalysts synthesized by the methods of the invention (Table 5).

The IW method, 2.5 g of silica ^{_{(41.6mmol), Ni (NO 3}} ) of 0.080g 2 · 6H 2 O (0.28mmol ) and 0.13g of _{H 2 PtCl 6 · 6H 2 O} (0. aqueous solution of 098mmol), or using an aqueous solution of 0.11g of _{Cu (NO 3) 3 · 3H} 2 O (0.45mmol) and 0.13g of _{H 2 PtCl 6 · 6H 2 O} (0.097mmol). Subsequently, it was dried at 110 ° C. overnight and calcined at 400 ° C. for 4 hours. The measured contents of NiPt (IW) and CuPt (IW) were in agreement with the theoretically supported amounts. The samples were then pelleted and sieved to a size of 650 to 1180 μm. Finally, the samples were reduced and passivated under the same conditions used for the samples prepared by the redox deposition method.

FIG. 8 shows the diffraction pattern of the reduced sample compared with the NiPt and CuPt samples. The peaks of the sample prepared by the impregnation method are wider and weaker than the bimetal alloys prepared by the method of the present invention, indicating that the particles are smaller and less crystallized. The NiPt (IW) sample also showed a peak corresponding to the (111) reflection of metallic Ni, indicating the formation of individual Ni clusters in addition to the NiPt alloy. In the CuPt (IW) catalyst, the asymmetric diffraction pea was deconvolved in two at 2θ = 41.3 ° corresponding to CuPt and 2θ = 42.1 ° corresponding to Cu 3 Pt (FIG. 8). The crystallite sizes calculated from Scheller's equation were 5 nm (CuPt) and 11 nm (Cu 3 Pt). The diffraction peak of CuPt (4: 1) indicated the presence of a single CuPt phase. Therefore, it was found that according to the method of the present invention, a phase-pure bimetal alloy can be formed as compared with the conventional impregnation method.

Example 8. Application to methane combustion
[Example 8-1] Evaluation of Pt-based bimetal alloy A methane combustion test was conducted using the bimetal alloys (NiPt / SiO ₂ and CuPt / SiO ₂ ) synthesized in Examples 1-1 and 1-2 as catalysts. The methane combustion test was carried out in a quartz tubular fixed bed reactor having an inner diameter of 1.0 cm / an inner diameter of 0.75 cm and a length of 27.5 cm under atmospheric pressure in a temperature range of 300 to 400 ° C. A 0.3 g amount of catalyst was loaded into the central 2 cm portion of the reactor. Prior to the reaction, the catalyst was pretreated in hydrogen at 400 ° C. for 2 hours. The reaction gas at a total flow rate of 100 cm ³ (NTP) min- ¹ consisted of 20 mol% methane, 3 mol% oxygen, 11.6 mol% helium (internal standard) and argon (equilibrium gas). The reaction temperature was changed in the following order: 400, 350, 300, 325 and 375 ° C. The smooth conversion curve obtained according to this order is evidence of catalyst stability and lack of deactivation. The catalyst was first stabilized at 400 ° C. and atmospheric pressure for 4 hours under reaction distribution. The products were analyzed online using two gas chromatographs: Shimadzu GC-2010 with a barrier discharge ionization detector (BID) and a Restek capillary column (30 m x 0.32 mm inner diameter x 10 μm film diameter) and thermal conductivity detection. A Shimadzu GC-8A equipped with a vessel (TCD) and a molecular sieve 5A (inner diameter 3m x 3mm) column was used. Methane conversion was calculated by dividing the number of moles of carbon in all observed products by the number of moles of initial methane. The oxygen balance was close to 100 ± 5%.

Table 15 shows the turnover frequency (TOF) based on CO absorption for various catalysts. Due to the kinetic mode, the conversion rate was less than 10% in all cases. The turnover frequency is a measure of the intrinsic activity of the catalyst and is obtained by the following equation.

In the formula, F _{CH 4} (μmols ^-1 ) is the inlet molar flow rate of methane, X is the fractional conversion of methane, W (g) is the weight of the catalyst, and S (μmol g ^-1 ) is the amount of CO absorbed. Comparisons were made with standard single metal catalysts Pt / SiO ₂ , Ni / SiO ₂ and Cu / SiO ₂ prepared in the same manner as bimetal catalysts, except that only one metal was used. The results are shown in Table 15.

The activity was in the order of NiPt (4: 1) to NiPt (IW)> Ni> Pt, but the difference was not large. All bimetal NiPt catalysts showed higher TOF values than separate pure metal catalysts at a maximum temperature of 400 ° C. The Ea value was similar for the Ni-containing sample and was higher than that of the Pt catalyst. Since the Ea value was about the same for all nickel-based catalysts, it is considered that the active species could be a nickel metal for methane combustion.

The results for the Cu-Pt system are also shown in Table 15. The activity was in the order of CuPt (4: 1)>Cu> CuPt (IW)> Pt. The bimetal CuPt (4: 1) catalyst prepared by the method of the present invention showed a higher TOF than the pure Cu catalyst, but the CuPt (IW) catalyst consisting of a mixed phase of CuPt and Cu ₃ Pt was lower and Pt. It was close to the TOF of (Fig. 8). These results suggested that CuPt phase is more active than the Cu 3 _Pt-phase with respect to the methane combustion. For Ea values, the order was given as CuPt (4: 1)> CuPt (IW)>Cu> Pt. Apart from the two-metal NiPt catalyst, the Ea values differ from each other among the copper-based catalysts, suggesting the possibility of a ligand effect.

[Example 8-2] Evaluation of Pd-based bimetal alloy A methane combustion test was conducted using the bimetal alloys (NiPd / SiO ₂ and CuPd / SiO ₂ ) synthesized in Examples 1-7 and 1-8 as catalysts.

Catalytic tests of NiPd (4: 1) / SiO ₂ and CuPd (4: 1) / SiO ₂ were performed with 10 mol% methane, 10 mol% oxygen, 11.6 mol% helium (internal standard) and argon (balanced gas). The same method as in Example 8-1 was used except for the reaction gas composed of. Table 16 shows the turnover frequency (TOF) for NiPd (4: 1) / SiO ₂ , CuPd (4: 1) / SiO ₂ and Pd / SiO ₂ catalysts. The turnover frequency was calculated from the dispersion from the particle size and the amount added. Table 16 also shows the results of the activity test in comparison with the standard single metal catalyst Pd / SiO ₂ prepared by the same method as the bimetal catalyst. The NiPd (4: 1) / SiO ₂ and CuPd (4: 1) / SiO ₂ catalysts showed higher TOF values than pure Pd metal catalysts.

Claims (21)

A method for producing a bimetal alloy supported on a carrier.
The bimetallic alloy, at least one base metal _{(M A)} and at least one noble metal _{(M B)} from the configured _{[M A] x [M B} ] 1 - an alloy of the formula of _x,
The following steps a) to c):
a) A step of adding a base metal to a solution in which a carrier is dispersed in a solvent;
b) A step of adding a reducing agent to reduce the base metal; and c) A step of adding a noble metal to the solution to form a bimetal alloy on the carrier;
Manufacturing method, including. The following steps d):
d) The production method according to claim 1, further comprising a step of separating the supported bimetal alloy obtained in the step c) from the solution. The production method according to claim 1 or 2, which comprises adding a reducing agent in the step c). The production method according to any one of claims 1 to 3, wherein the steps a) to c) are carried out in a single pot, container, container or reactor. It said base metal _{(M A)} is, Sc, Ti, V, Cr , Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Hf, Ta, W, Re, and combinations of any The production method according to any one of claims 1 to 4, which is selected from the group consisting of a combination of. Said noble metal _{(M B)} is, Tc, Ru, Rh, Pd , Ag, Os, Ir, Pt, are selected from Au and the group consisting of any combination thereof, according to any one of claims 1 to 5 Manufacturing method. It said base metal _{(M A)} is Ni or Cu, the precious metal _{(M B)} is Pt, the production method according to any one of claims 1 to 6. The formula _{[M A] x [M B} ] 1 - In _x, x is in the range of 0.01 to 0.99, The method according to any one of claims 1 to 7. The formula _{[M A] x [M B} ] 1 - In _x, the range of x is from 0.10 to 0.90, The method according to claim 8. Total reduction potential (ΔE ^o _Total) is greater than 0V, the manufacturing method according to any one of claims 1 to 9 wherein the base metal _{(M A)} and the noble metal _{(M B).} The production method according to any one of claims 1 to 10, wherein the amount of the bimetal alloy supported on the carrier is 0.1 to 80% by weight. The production method according to claim 11, wherein the amount of the bimetal alloy supported on the carrier is 1 to 20% by weight. The carrier is selected from the group consisting of silica, alumina, titania, zinc oxide, tria, ittoria, ceria, zirconia, carbon, carbon nanotubes, magnesia, kaolin, bentonite, diatomaceous earth, silicalite, zeolite, and any combination thereof. The production method according to any one of claims 1 to 12, which is a material for use. The production method according to any one of claims 1 to 13, wherein the carrier is a silica-containing material selected from the group consisting of silica-alumina, silica-titania, silica-magnesia, and silica-zirconia. The production method according to claim 13 or 14, wherein the silica or silica-containing material is prepared by flame hydrolysis, sol-gel method, precipitation, or condensation. 1. The solvent is selected from the group consisting of water, alcohols, ethers, esters, furanolactones, amides, toluenes, xylenes, sulfolanes, oxalanes, N, N-dimethylformamides, and any combination thereof. The production method according to any one of ~ 15. The production method according to any one of claims 1 to 16, wherein the reducing agent is hydrogen, carbon monoxide, hydrazine, lithium aluminum hydride, or sodium borohydride. The production method according to claim 17, wherein the reducing agent is sodium borohydride. The production method according to any one of claims 1 to 18, wherein the separation in the step d) is performed using filtration or centrifugation. A method of oxidizing hydrocarbons
Including a step of bringing the hydrocarbon into contact with a bimetal alloy catalyst supported on a carrier in an oxygenated atmosphere;
Said bimetallic alloy, at least one base metal _{(M A)} and composed of at least one noble metal _{(M B) [M A]} x [M B] 1 - Yes an alloy represented by the formula _x;
It said base metal _{(M A)} is, Sc, Ti, V, Cr , Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Hf, Ta, W, Re, and combinations of any Selected from the group consisting of combinations of;
Said noble metal _{(M B)} is, Tc, Ru, Rh, Pd , Ag, Os, Ir, Pt, selected from Au and the group consisting of any combination thereof; and wherein said carrier, silica, alumina, titania oxide A material selected from the group consisting of zinc, tria, ittoria, ceria, zirconia, carbon, carbon nanotubes, magnesia, kaolin, bentonite, diatomaceous earth, silicalite, zeolites, and any combination thereof.
A method characterized by that. The method of claim 20, wherein the hydrocarbon is methane.