EP3965927A1

EP3965927A1 - Method for preparing catalyst support loaded with a first metal and a second metal

Info

Publication number: EP3965927A1
Application number: EP20801860.6A
Authority: EP
Inventors: Guang-hui WANG; Zheng-bin TIAN
Original assignee: Qingdao Institute of Bioenergy and Bioprocess Technology of CAS
Current assignee: Qingdao Institute of Bioenergy and Bioprocess Technology of CAS
Priority date: 2019-05-05
Filing date: 2020-04-28
Publication date: 2022-03-16
Also published as: CN111889136B; EP3965927A4; WO2020224483A1; CN111889136A

Abstract

A method for preparing a highly dispersed ultrafine bimetallic shaped catalyst is provided. Said catalyst is obtainable by a method of solid-state seeded-growth strategy. Said method comprises: mixing an aromatic compound containing at least one N-group, a surfactant, an aldehyde compound and a first metal salt, wherein the first metal is one of Pd, Au, Pt and the like, and preparing a uniform solution; heating the solution to form a support and metal nanocluster seeds loaded on the support; uniformly introducing a second element into the support; during the hydrogenation reduction, the second element grows by taking the first metal nanocluster as a seed to obtain the bimetal-loaded catalyst support. The method can obtain the highly dispersed supported bimetallic catalyst with uniform ultrafine particles. The catalyst is easily shaped, easily separated and regenerated. The preparation process is green and energy-efficient, suitable for promotion, and therefore has a broad scope in the field of catalytic hydrogenation, oxidation and the like.

Description

Method for preparing catalyst support loaded with a first metal and a second metal

Technical Field

The present invention relates to a method for preparing highly dispersed ultrafine bimetallic shaped catalyst support by solid state seeded-growth strategy using metallic nanoclusters loaded on the solid support as the first metal, i.e. crystal seeds, which guide in situ the growth of the second metal element to obtain the supported bimetallic catalyst.
Background Art
Bimetallic catalysts are an important class of heterogeneous catalysts and are widely used in chemical industry such as dehydrogenation reforming, selective hydrogenation, acetoxylation etc. In recent years, the application of bimetallic catalysts in the field of biomass conversion and electrocatalysis has been further developed. Compared to monometallic catalysts, bimetallic catalysts often exhibit better performance and stability thanks to their unique geometry, electronic structure, and synergetic effect between the two metal elements.
However, the synthesis of bimetallic catalysts of uniform ultrafine sizes supported on inert non-reductive supports (such as carbon materials or silicon materials) has been challenging in the field of catalyst syntheses. The traditional methods for preparing bimetallic catalysts are mainly impregnation method and sol-immobilization method. The former preparation method is simple and convenient; however, the particle size is not uniform and the particle dispersion is bad. The latter method can provide small-sized catalyst having uniform particle size, however, it is not easy to remove the protective agents on the metal surface and the interaction between the metal and the support is weak, which make the metal fall off the support easily. The above drawbacks influence the activity and stability of the catalysts considerably.
In catalytic reactions, the powder catalysts are often required to be processed by extra shaping procedures, such as for example by extrusion molding etc., to endow the catalyst with the required strength. However, such shaping processes inevitably involve binders, resulting in a decrease in the catalyst activity.
Thus, the synthesis of the traditional bimetallic catalyst preparation and the post-shaping techniques thereof are still problematic in industrial application, which makes it appealing to search for a new type of bimetallic catalyst, the synthesis and the post-shaping of which overcomes the drawbacks in the prior art and thus suitable for industrial applications.
Brief Description of the Invention
To overcome the above-mentioned problems of oversizing of the catalyst particles, the metal particles falling easily off the catalyst support, and the drastic decreasing of the catalytic activity as a result of the post-shaping procedure for the traditional bimetallic catalysts, the inventors provide a highly dispersed ultrafine bimetallic shaped catalyst and the preparation thereof by a method of solid state seeded-growth strategy. Said method mainly comprises two procedures: i.e. directly loading metallic nanoclusters seeds on the solid support and uniformly introducing the second metal.
It is to note that in the context of the present invention, the metal particles, metal clusters may be used interchangeable and both refer to the metal nanoparticles and metal clusters loaded on the inventive catalyst support.
The present invention provides a method for preparing highly dispersed ultrafine bimetallic shaped catalyst, comprising a) providing an aqueous solution comprising an aromatic compound having at least one N-containing group or a mixture of several said aromatic compounds, at least one surfactant, an aldehyde compound and a salt of a first metal selected from Pd, Au, and Pt; b) heating the aqueous solution obtained in step a) , whereby the polymer support is formed and nanoparticles of the first metal are formed on the polymer support, c) treating the polymer support obtained in step b) with an aqueous solution of a salt of the second metal, wherein the second metal is selected from the group consisting of Pd, Pt, Au, Ag, Ni, Cu, Fe, Zn, Co, Ru, Rh, Ir, Os, Sb, Bi, W with the proviso that the second metal is different from the first metal, and d) separating the polymer support obtained in step c) from the aqueous solution, optionally washing the separated solid catalyst support and subjecting it, after optionally drying, to a reduction treatment whereby the catalyst support loaded with the first metal and loaded with the second metal, namely the supported bimetallic catalyst is obtained. The optional shaping treatment comprises extrusion moulding or tablet pressing or the like. Analyses indicate a strong electronic interaction between the first metal component and the second metal component in the bimetallic catalyst, which is a proof of the bimetallic character of the inventive catalyst support loaded with the first metals component and the second metal component, i.e. the supported catalyst prepared according to the inventive method is a bimetallic catalyst.
Herein, the molar ratio of the aromatic compound having at least one N-containing group to the first metal is in the range of 1: 1 to 1000: 1.
The salt of the first metal may be selected from one of the salts of palladium nitrate, potassium tetrachloropalladate, palladium (II) acetylacetonate, palladium (II) chloride, chloroplatinic (IV) acid, potassium tetrachloroplatinate, chloroauric (III) acid, potassium tetrachloroaurate (III) .
The at least one surfactant may be selected from one or more of Pluronic F127, P123, Tween-80, Polyvinylpyrrolidone (PVP) , Brij-58, PEO-b-PS, Hexadecyl trimethyl ammonium Bromide, sodium dodecyl benzene sulfonate, sodium oleate, amino acids.
According to the present invention, the aromatic compound having at least one N-containing group may be selected from 2-aminophenol, 3-aminophenol, 4-aminophenol, 3-amino-1, 2-benzendiol, 4-aminocatechol, 2-amino-1, 3-benzenediol, 4-amino-1, 3-benzenediol, 5-amino-1, 3-benzenediol, 2-amino-1, 4-benzenediol, 2, 3-diaminophenol, 3, 4-diaminophenol, 2, 4-diamino-phenol, 3, 5-diaminophenol, 2, 5-diaminophenol, pyrrole, aniline, diaminopyridine, dopamine or a mixture thereof.
Furthermore, the present invention provides directly loading the first metal, i.e. the metal nanoclusters seeds on the solid-state support, which function as anchoring positions, and the second metal ions is introduced uniformly and then forms bimetallic alloy at the anchoring positions; the second metal is added in a molar ratio in the range of 1: 100 to 10: 1 to the first metal.
The second metal ion may be selected from the group consisting of Pd, Pt, Au, Ag, Ni, Cu, Fe, Zn, Co, Ru, Rh, Ir, Os, Sb, Bi, W with the proviso that the second metal is different from the first metal. The second metal may be selected from the metal salts such as, for example, palladium nitrate, potassium chloropalladium (II) , palladium acetylacetonate, palladium dichloride, chloroplatinic acid, potassium tetrachloroplatinate (II) , chloroauric acid, potassium tetrachloroaurate, silver nitrate, nickel nitrate, copper nitrate, iron nitrate, zinc nitrate, cobalt nitrate, potassium ferricyanide (III) , potassium hexacyanocobaltate, antimony trichloride, ferric chloride, zinc chloride.
The shaping treatment may preferably be accomplished by means of tableting pressing using a tablet machine, the pressure may be in the range of 1 to 100 bar.
The reduction treatment is usually carried out under a normal pressure of a gaseous mixture of hydrogen and argon, hydrogen and nitrogen or hydrogen and a mixture of argon and nitrogen at a temperature in a range of 150 ℃ –800 ℃, wherein the volume ratio of hydrogen to argon, to nitrogen, or to the mixture of argon and nitrogen is in the range of 0.1%to 20%.
The bimetallic catalyst may be prepared by the above-mentioned method.
Thus, the present invention is directed to a method for preparing a catalyst support loaded with a first metal and loaded with a second metal, comprising the steps of: a) providing an aqueous solution comprising an aromatic compound having at least one N-containing group or a mixture of several said aromatic compounds, at least one surfactant, an aldehyde compound and a salt of the first metal being selected from Pd, Au and Pt,
b) heating the aqueous solution obtained in step a) to a temperature in the range of 40 ℃ –200 ℃, preferably in the range of 60 ℃ –150 ℃, whereby the catalyst support is formed and particles of the first metal are formed on the solid catalyst support, c) treating the catalyst support obtained in step b) with an aqueous solution of a salt of the second metal, wherein the second metal is selected from the group consisting of Pd, Pt, Au, Ag, Ni, Cu, Fe, Zn, Co, Ru, Rh, Ir, Os, Sb, Bi, W with the proviso that the second metal is different from the first metal,
d) separating the polymer support obtained in step c) from the aqueous solution, optionally washing the separated solid catalyst support and subjecting it, after optionally drying, to a reduction treatment whereby the catalyst support loaded with the first metal and loaded with the second metal is obtained.
In an embodiment of the inventive method for preparing a catalyst support, in step a) the molar ratio of the aromatic compound having at least one N-containing group to the first metal is in the range of 1: 1 to 1: 1000.
In a further embodiment of the inventive method for preparing a catalyst support, in step a) the molar ratio of the aldehyde compound to the aromatic compound having at least one N-containing group is in the range of 0.1: 1 to 10: 1, preferably in the range of 0.5: 1 to 5: 1.
In a further embodiment of the inventive method for preparing a catalyst support, in step a) the molar ratio of the at least one surfactant to the aromatic compound having at least one N-containing group is in the range of 0.01: 1 to 100: 1, preferably in the range of 0.1: 1 to 10: 1.
In an even further embodiment of the inventive method for preparing a catalyst support, the aromatic compound in step a) is selected from 2-aminophenol, 3-aminophenol, 4-aminophenol, 3-amino-1, 2-benzendiol, 4-aminocatechol, 2-amino-1, 3-benzenediol, 4-amino-1, 3-benzenediol, 5-amino-1, 3-benzenediol, 2-amino-1, 4-benzenediol, 2, 3-diaminophenol, 3, 4-diaminophenol, 2, 4-diamino-phenol, 3, 5-diaminophenol, 2, 5-diaminophenol, pyrrole, aniline, diaminopyridine, dopamine or a mixture thereof.
According to the inventive method for preparing a catalyst support, in step a) of the method, the aldehyde compound can be an aliphatic aldehyde having 1 to 12 carbon atoms, such as formaldehyde, acetaldehyde, crotonaldehyde, or an aromatic aldehyde such as furfural, or a compound which can be decomposed to release formaldehyde, such as hexamethylenetetramine or paraformaldehyde.
Preferably, the at least one surfactant used in step a) of the method for preparing a catalyst support is selected from the group consisting of Pluronic F127, P123, Tween-80, Polyvinylpyrrolidone (PVP) , Brij-58, PEO-b-PS, hexadecyl trimethyl ammonium Bromide, sodium dodecyl benzene sulfonate, sodium oleate, amino acids or a mixture thereof, preferably the surfactant is selected from Pluronic F127, P123, Tween-80, PEO-b-PS and amino acids, more preferably the surfactant is Pluronic F127, PEO-b-PS.
In a further embodiment of the inventive method for preparing a catalyst support the salt of the first metal used in step a) is selected from the group consisting of palladium nitrate, potassium tetrachloropalladate (II) , palladium acetylacetonate, palladium (II) chloride, chloroplatinic acid, potassium tetrachloroplatinate, chloroauric acid, postaasium tetrachloroaurate.
In an embodiment of the inventive method for preparing a catalyst support, the aqueous solution in step b) is heated at a temperature in the range of 40 ℃ –200 ℃, preferably in the range of 60℃ –150 ℃.
According to a further embodiment of the method for preparing a catalyst support, in step c) the second metal is loaded in an amount that the molar ratio of the second metal to the first metal is in the range of 1: 100 to 10: 1.
According to an even further embodiment of the inventive method for preparing a catalyst support, in step c) the second metal is selected from palladium nitrate, potassium chloropalladium, palladium acetylacetonate, palladium dichloride, chloroplatinic acid, potassium tetrachloroplatinate, chloroauric acid, potassium tetrachloroaurate, silver nitrate, nickel nitrate , copper nitrate, iron nitrate, zinc nitrate, cobalt nitrate, potassium ferricyanide, potassium hexacyanocobaltate, antimony trichloride, ferric chloride, zinc chloride, with the proviso that the second metal is different from the first metal.
In a further embodiment of the inventive method for preparing a catalyst support, in step c) the second metal is loaded at a pH in the range of 2 –12.
According to the inventive method for preparing a catalyst support, the reduction treatment in step d) is carried out under normal pressure of a gaseous mixture of hydrogen and argon, hydrogen and nitrogen or hydrogen and a mixture of argon and nitrogen at a temperature in a range of 150 ℃ –800 ℃, wherein the volume ratio of hydrogen to argon, to nitrogen, or to the mixture of argon and nitrogen is in the range of 0.1%to 20%.
Preferably, the inventive method for preparing a catalyst support comprises subjecting the catalyst to a shaping treatment.
According to a further embodiment of the method for preparing a catalyst support, the catalyst is shaped by tablet pressing under a pressure in the range of 1 bar –100 bar.
The extra aspects and advantages of the invention are illustrated in the following description, some of the contents are obvious from the description or may be obtained during the operation.
Brief Description of the Figures
Fig. 1 is a sketch of the preparation of the bimetallic catalyst
Fig. 2 shows a STEM image of the supported metal nanocluster seeds prepared in Example 1
Fig. 3 shows a TEM image (3a) and XRD analysis (3b) of the shaped bimetallic shaped catalyst Pd ₁Au _0.25 prepared in Example 2
Fig. 4 shows a SEM image (4a) and a shaped entity of the shaped of the bimetallic shaped catalyst Pd ₁Au _0.25 prepared in Example 2
Fig. 5 shows a TEM image of the shaped bimetallic shaped catalyst Pd ₁Au _0.5 prepared in Example 3
Fig. 6 shows a TEM image (6a) and an XRD analysis (6b) of the shaped bimetallic shaped catalyst Pd ₁Ag _0.5 prepared in Example 4
Fig. 7 shows a TEM image (7a) and an XRD analysis (7b) of the shaped bimetallic shaped catalyst Pd ₁Cu _0.5 prepared in Example 5
Fig. 8 shows a TEM image (8a) and an XRD analysis (8b) of the shaped bimetallic shaped catalyst Pd ₁Ru _0.5 prepared in Example 6

Detailed Description of the Invention

The method according to the present invention for preparing bimetallic catalysts and the bimetallic catalysts prepared thereby are described as follows in detail.
For the inventive method, at first an aromatic compound having at least one N-containing group, a surfactant, an aldehyde compound and a first metal salt are mixed to provide an aqueous solution. In said solution the polymer support is prepared by means of hydrothermal process, on which the nanoparticles of the first metal are deposited in situ; uniformly introducing the second metal, wherein during the reduction process, the ultrafine nanoparticles of the first metal function as seeds directing the growth of the second metal on the catalyst support by means of Solid State Seeded-Growth Strategy to synthesize the uniform bimetallic catalyst.
Herein, the aromatic compound having at least one N-containing group may be one selected from 2-aminophenol, 3-aminophenol, 4-aminophenol, 3-amino-1, 2-benzendiol, 4-aminocatechol, 2-amino-1, 3-benzenediol, 4-amino-1, 3-benzenediol, 5-amino-1, 3-benzenediol, 2-amino-1, 4-benzenediol, 2, 3-diaminophenol, 3, 4-diaminophenol, 2, 4-diamino-phenol, 3, 5-diaminophenol, 2, 5-diaminophenol, pyrrole, aniline, diaminopyridine, dopamine or a mixture thereof. Forming ultrafine metal nanoclusters seeds uniformly on the surface of the support is a crucial issue for the implementation of the inventive method, i.e. the solid state seeded-growth strategy for preparing the supported ultrafine bimetallic nanocluster catalysts. It is the consideration of the inventors that the interaction between the aromatic compound having at least one N-containing group and the first metal is essential. Said interaction ensures the formation of the metal nanoparticle seeds on the support. Uniformly introducing the second metal onto the support is another crucial issue for implementation of the inventive method of solid state seeded growth of the supported ultrafine bimetallic catalyst. The uniformly introducing the second metal may be achieved when an abundant of amino, hydroxyl, or carboxyl functional groups etc. are available in the synthesized support. Thus, the aromatic compound having at least one N-containing group is one selected from the group consisting of 2-aminophenol, 3-aminophenol, 4-aminophenol, 3-amino-1, 2-benzendiol, 4-aminocatechol, 2-amino-1, 3-benzenediol, 4-amino-1, 3-benzenediol, 5-amino-1, 3-benzenediol, 2-amino-1, 4-benzenediol, 2, 3-diaminophenol, 3, 4-diaminophenol, 2, 4-diamino-phenol, 3, 5-diaminophenol, 2, 5-diaminophenol, pyrrole, aniline, diaminopyridine, dopamine.
The aldehyde compound can be an aliphatic aldehyde having 1 to 12 carbon atoms, such as formaldehyde, paraformaldehyde, furfural, acetaldehyde, crotonaldehyde, or an aromatic aldehyde, or a compound which can be decomposed to release formaldehyde, such as hexamethylenetetramine or paraformaldehyde.
The surfactant is used as a pore-forming agent to form a mesoporous structure in the support and as a crosslinking agent to form a coral-like crosslinked structure. Said surfactant is one or more selected from the group consisting of Pluronic F127, P123, Tween-80, and polyvinylpyrrolidone (PVP) , Brij-58, PEO-b-PS, cetyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, sodium oleate and amino acids. Preferably, the surfactant is selected from Pluronic F127, P123, Tween-80, PEO-b-PS and amino acids, more preferably is Pluronic F127 and PEO-b-PS.
The surfactant is used in an amount of 0.01 to 100 times of the weight of the aromatic compound having at least one N-containing group, preferably in an amount of 0.1 to 10 times of the weight of the aromatic compound. If the surfactant is used less than 0.1 times by weight, the support is formed without mesoporous structure; if the surfactant is used more than 100 times, the rate of polymerization and the yield will be too slow, and is economically not favored. Meanwhile, the formation of a cross-linked structure is not favored when the surfactant exceeds the above range.
The molar ratio of the aromatic compound having at least one N-containing group to the first metal is in the range of 1 : 1 to 1000 : 1. The amount of loading of the metal on the support can be adjusted by tuning the ratio of the aromatic compound having at least one N-containing group to the first metal. If the ratio is below 1 : 1, the loading of metal will be too high to control the size of the metal nanocluster seeds; on the other hand, if the molar ratio of the aromatic compound having at least one N-containing group to the first metal is more than 1000: 1, the loading rate of the metal will be too low to form applicable supported metal catalyst.
Once the solution containing the components for preparing the support and the first metal is prepared, it can be heated to form in a single step the polymer support supported metal particles, i.e. the metal nanocluster seeds. The solution is heated at a temperature in the range of 40 –200 ℃. If the reaction temperature is lower than 40 ℃, the rate of polymerization is two slow and it is difficult to reduce the metal ions to form metal nanoclusters. If the reaction temperature is above 200 ℃, the support is formed too fast and the metal ions are reduced too fast. Consequently, the supported catalyst with an uneven distribution of the particle sizes of the metal nanocluster seeds is formed. Therefore, the reaction temperature of the solution is preferably controlled in the range of 60 –150 ℃.
The first metal ions may be selected from one of Pd, Au, Pt. Salt containing one of the above metal ions is added to the solution, which –on heating the reaction solution –forms particles of the first metal, i.e. the supported first metal nanoparticle seeds. The inventive metal nanoclusters seeds formed herein are extremely small and uniformly distributed on the support (shown in Figure 2) , which is the key to the synthesis of the inventive highly dispersed ultrafine supported bimetallic catalysts.
The metal salt containing the first metal ions may be selected from the group consisting of palladium nitrate, potassium tetrachloropalladate (II) , palladium acetylacetonate, palladium dichloride, chlopllatinic acid, platinum tetrachloride, potassium hexachloroplatinate, chloroauric acid, potassium tetrachloroaurate, preferably potassium tetrachloro palladate.
Furthermore, the present invention achieves directly loading metal nanoparticle seeds on the solid support, said metal nanocluster seeds function as anchor positions guiding the loading of the second metal to form therewith the supported bimetallic catalyst.
The polymer support loaded with metal nanocluster seeds is dispersed in water, on which the second metal is loaded, wherein the pH value is set to 2-12. Uniformly introducing the second metal is another crucial issue for the synthesis of highly dispersed ultrafine bimetallic shaped catalyst. In this concern, the functional groups on the support such as for example the nitrogen-containing functional groups act as binding sites for the second metal salts, leading to uniform or even homogeneous dispersion of the second metal on the support. Besides the functional groups on the surface of the support, the pH value of the solution may exert an important influence. A base solution such as ammonia solution, lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, and an acid such as hydrochloric acid, nitric acid, sulfuric acid, organic acid and carboxylic acid may be used to set the pH value of the solution.
The amount of substance of the second metal is added in a molar ratio of 1: 100 to 10: 1 relative to the first metal. Taking the amount of substance of the first metal as 1 equivalent, if the second metal is added in an amount below 1: 100 equivalent, the bimetallic effect is not prominent; if the second metal is added in an amount higher than 10 equivalents, it will result in formation of oversized metal particles or formation of the separate second metallic particles.
The second metal may be selected from the group consisting of Pd, Pt, Ag, Ni, Cu, Fe, Zn, Co, Ru, Rh, Ir, Os, Sb, Bi, W. Correspondingly, a salt containing one of the above metal ions may be used, such as for example palladium nitrate, potassium tetrachloropalladate, palladium acetylacetonate, palladium dichloride, chloroplatinic acid, potassium tetrachloroplatinate, chloroauric acid, potassium tetrachloroaurate, silver nitrate, nickel nitrate, copper nitrate, iron nitrate, zinc nitrate, cobalt nitrate, potassium ferricyanide, potassium hexacyanocobaltate, ruthenium trichloride, ferric chloride, zinc chloride, and the like, with the proviso that the second metal is different from the first metal.
The support of the inventive supported bimetallic catalyst has a crosslinked structure. The supported bimetallic catalyst can be shaped by a tablet press machine at a pressure in the range of 1 –100 bar. Furthermore, the mechanical strength will be increased upon maturing during hydrogenation. These reduce the possibility of reduction of the catalytic activity during the post shaping process and lower the production costs.
The reduction treatment temperature is usually set in the range of 150 ℃ –800 ℃.
The supported bimetallic catalyst can be prepared by the above-described method.
The synthesized catalysts may be characterized by transmission electron microscopy (TEM) , scanning electron microscopy (SEM) , X-ray diffraction, and ICP.
The inventive bimetallic catalyst obtained by the above-mentioned inventive method has ultrafine metal particles size, uniform particle size distribution. The catalyst can be easily separated and regenerated, and is suitable for studying reaction mechanism. The preparation process of the catalyst is green and energy effective. It is highly recommendable in the fields of catalytic hydrogenation and oxidation.
Furthermore, the solid state seeded-growth strategy (the inventors name it SSSG) developed for the first time in the present invention can be expanded to other systems, such as silicone oxide, metal oxide supported bimetallic nano-catalyst. The technical solutions of the present invention will be described in detail in the following with respect to the specific embodiments, which serve solely the purpose of illustrating the invention and not limiting the scope of the present invention.
According to the present invention, catalyst support loaded with different metals, i.e. different kinds of bimetallic catalysts can be prepared by altering the metal ions. The present invention will be illustrated taking the syntheses of PdAu, PdAg, PdCu, PdRu bimetallic catalysts as examples. The first metal component Pd can be put into use in a form of a salt, such as for example palladium nitrate, potassium tetrachloropalldate, palladium acetylacetonate, palladium (II) chloride in an amount of 0.01 mmol to 0.5 mmol. Pluronic F127 is selected as surfactant in an amount of 0.1 to 10 g. 3-Aminophenol is selected to be the aromatic compound in an amount of 0.1 to 5 g. Hexamethylenetetramine, which on heating releases formaldehyde serving as monomer for copolymerizing with the 3-aminophenol and at the same time as a reducing agent for the reduction of metal ions, is used in an amount of 0.1-6 g. The above starting materials are dissolved in 40 –1000 mL water to give a homogeneous solution. The second metal component is gold in examples 2 and 3, silver in example 4, copper in example 5 and ruthenium in example 6. The bimetallic catalysts can be synthesized as follows:
Example 1
Preparation of the supported metal nanocluster seeds: 0.36 g 3-Aminophenol (3.3 mmol) , 0.28 g hexamethylenetetramine (2.0 mmol) , 0.16 g Pluronic F127 and 15.7 mg potassium tetrachloropalladate (II) (0.048 mmol) were dissolved in 80 ml of water to give a clear solution. Said solution was allowed to react for 24 hours at 80 ℃. After the reaction, the reaction mixture was vacuum-filtered, washed until it was neutral to provide the nitrogen-containing polymer supported Pd nanocluster seeds (as shown Fig. 2) .
Example 2
Preparation of Pd ₁Au _0.25 catalyst: 0.36 g 3-Aminophenol (3.3 mmol) , 0.28 g hexamethylenetetramine (2.0 mmol) , 0.16 g Pluronic F127 and 15.7 mg potassium tetrachloropalladate (II) (0.048 mmol) were dissolved in 80 ml of water to give a clear solution. Said solution was allowed to react for 24 hours at 80 ℃. After reaction, the reaction mixture was vacuum-filtered, washed until it was neutral to provide the nitrogen-containing polymer supported palladium nanocluster seeds. Said palladium nanocluster seeds supported on nitrogen-containing polymer as obtained in Example 1 was dispersed in 50 ml of water, to which was added 4.53 mg potassium tetrachloroaurate (0.012 mmol) . The reaction mixture was allowed to react under stirring for 2 hours. After reaction, the product was vacuum-filtered, washed, pressed with a tablet press, and dried, followed by reducing at 360 ℃ under an reductive atmosphere for 2 hours to provide the polymer supported highly dispersed ultrafine Pd-Au bimetallic catalyst (as shown Fig. 3 and Fig. 4) .
Example 3
Preparation of Pd ₁Au _0.5 catalyst: Ratio of the metals in the bimetallic catalysts may be adjusted by amount of the second metal added to the nitrogen-containing polymer supported palladium nanocluster seeds. 0.36 g 3-Aminophenol (3.3 mmol) , 0.28 g hexamethylenetetramine (2.0 mmol) , 0.16 g Pluronic F127 and 15.7 mg potassium tetrachloropalladate (II) (0.048 mmol) were dissolved in 80 ml of water to give a clear solution. Said solution was allowed to react for 24 hours at 80 ℃. After reaction, the reaction mixture was vacuum-filtered, washed until it was neutral to provide the nitrogen-containing polymer supported palladium nanocluster seeds. Said nitrogen-containing polymer supported palladium nanocluster seeds was dispersed in 50 ml water, to which was added 9.07 mg chloroauric acid (0.024 mmol) . The mixture was allowed to react for under stirring 2 hours. After reaction, the reaction mixture was vacuum-filtered, washed, pressed with a tablet press, dried, followed by reducing at 360 ℃ in a reductive atmosphere for 2 hours to provide the polymer supported highly dispersed ultrafine Pd-Au bimetallic catalyst (as shown in Fig. 5) .
Example 4
Preparation of Pd ₁Ag _0.5 catalyst: 0.36 g 3-Aminophenol (3.3 mmol) , 0.28 g hexamethylenetetramine (2.0 mmol) , 0.16 g Pluronic F127 and 15.7 mg potassium tetrachloropalladate (II) (0.048 mmol) were dissolved in 80 ml of water to give a clear solution. Said solution was allowed to react for 24 hours at 80 ℃. After reaction, the reaction mixture was vacuum-filtered, washing until it was neutral to provide the nitrogen-containing polymer supported palladium nanocluster seeds. Said nitrogen-containing polymer supported palladium nanocluster seeds was dispersed in 50 ml water, to which was added 4.08 mg silver nitrate (0.024 mmol) . The mixture was allowed to react for 2 hours under stirring. After reaction, the reaction mixture was vacuum-filtered, washed, pressed with a tablet press, dried, followed by reduction at 360 ℃ in a reductive atmosphere for 2 hours to provide the polymer supported highly dispersed ultrafine Pd-Ag bimetallic catalyst (as shown in Fig. 6) .
Example 5
Preparation of Pd ₁Cu _0.5 catalyst: 0.36 g 3-Aminophenol (3.3 mmol) , 0.28 g hexamethylenetetramine (2.0 mmol) , 0.16 g Pluronic F127 and 15.7 mg potassium tetrachloropalladate (II) (0.048 mmol) were dissolved in 80 ml of water to give a clear solution. Said solution was allowed to react for 24 hours at 80 ℃. After reaction, the reaction mixture was vacuum-filtered, washed until it was neutral to provide the nitrogen-containing polymer supported palladium nanocluster seeds. Said nitrogen-containing polymer supported palladium nanocluster seeds was dispersed in 50 ml water, to which was added 5.80 mg copper nitrate (0.024 mmol calculated with respect to trihydrate) . The mixture was allowed to react for 2 hours under stirring. After reaction, the reaction mixture was vacuum-filtered, washed, pressed with a tablet press, dried, followed by reduction at 360 ℃ in a reductive atmosphere for 2 hours to provide the polymer supported highly dispersed ultrafine Pd-Cu bimetallic catalyst (as shown in Fig. 7) .
Example 6
Preparation of Pd ₁Ru _0.5 catalyst: 0.36g 3-Aminophenol (3.3 mmol) , 0.28 g hexamethylenetetramine (2.0 mmol) , 0.16 g Pluronic F127 and 15.7 mg potassium tetrachloropalladate (II) (0.048 mmol) were dissolved in 80 ml of water to give a clear solution. Said solution was allowed to react for 24 hours at 80 ℃. After reaction, the reaction mixture was vacuum filtered, washed until it was neutral to provide the nitrogen-containing polymer supported palladium nanocluster seeds. Said nitrogen-containing polymer supported palladium nanocluster seeds was dispersed in 50 ml water, to which was added 4.98 mg ruthenium (III) chloride (0.024 mmol) . The mixture was allowed to react for 2 hours under stirring. After reaction, the reaction mixture was vacuum-filtered, washed, pressed with a tablet press, dried, followed by reduction at 360 ℃ in a reductive atmosphere for 2 hours to provide the polymer supported highly dispersed ultrafine Pd-Ru bimetallic catalyst (as shown in Fig. 8) .
A person of ordinary skill should keep in mind that the above embodiments serve merely the purpose of illustrating the present invention, while not limiting the same. Within the essence of the present invention, any variation and modification should be considered to fall into the scope of the present invention.

Claims

A method for preparing a catalyst support loaded with a first metal and loaded with a second metal, comprising the steps of:

a) providing an aqueous solution comprising an aromatic compound having at least one N-containing group or a mixture of several said aromatic compounds, at least one surfactant, an aldehyde compound and a salt of the first metal being selected from Pd, Au and Pt,

b) heating the aqueous solution obtained in step a) to a temperature in the range of 40 ℃ –200 ℃, preferably in the range of 60 ℃ –150 ℃, whereby the catalyst support is formed and particles of the first metal are formed on the catalyst support,

c) treating the catalyst support obtained in step b) with an aqueous solution of a salt of the second metal, wherein the second metal is selected from the group consisting of Pd, Pt, Au, Ag, Ni, Cu, Fe, Zn, Co, Ru, Rh, Ir, Os, Sb, Bi, W with the proviso that the second metal is different from the first metal,

d) separating the polymer catalyst support obtained in step c) from the aqueous solution, optionally washing the separated solid catalyst support and subjecting it, after optionally drying, to a reduction treatment whereby the catalyst support loaded with the first metal and loaded with the second metal is obtained.
The method for preparing a catalyst support according to claim 1, wherein in step a) the molar ratio of the aromatic compound having at least one N-containing group to the first metal is in the range of 1: 1 to 1: 1000.
The method for preparing a catalyst support according to claim 1 or 2, wherein in step a) the molar ratio of the aldehyde compound to the aromatic compound having at least one N-containing group is in the range of 0.1: 1 to 10: 1, preferably in the range of 0.5: 1 to 5: 1.
The method for preparing a catalyst support according to any one of claims 1-3, wherein in step a) the molar ratio of the at least one surfactant to the aromatic compound having at least one N-containing group is in the range of 0.01: 1 to 100: 1, preferably in the range of 0.1: 1 to 10: 1.
The method for preparing a catalyst support according to any one of claims 1-4, wherein in step a) the aromatic compound is selected from 2-aminophenol, 3-aminophenol, 4-aminophenol, 3-amino-1, 2-benzendiol, 4-aminocatechol, 2-amino-1, 3-benzenediol, 4-amino-1, 3-benzenediol, 5-amino-1, 3-benzenediol, 2-amino-1, 4-benzenediol, 2, 3-diaminophenol, 3, 4-diaminophenol, 2, 4-diamino-phenol, 3, 5-diaminophenol, 2, 5-diaminophenol, pyrrole, aniline, diaminopyridine, dopamine or a mixture thereof.
The method for preparing a catalyst support according to any one of claims 1-5, wherein in step a) the aldehyde compound is an aliphatic aldehyde having 1 to 12 carbons, such as formaldehyde, acetaldehyde, crotonaldehyde, or an aromatic aldehyde such as furfural, or a compound which can release formaldehyde, such as hexamethylenetetramine or paraformaldehyde.
The method for preparing a catalyst support according to any one of claims 1-6, wherein in step a) the at least one surfactant is selected from the group consisting of Pluronic F127, P123, Tween-80, Polyvinylpyrrolidone (PVP) , Brij-58, PEO-b-PS, hexadecyl trimethyl ammonium Bromide, sodium dodecyl benzene sulfonate, sodium oleate, amino acids or a mixture thereof, preferably Pluronic F127, P123, Tween-80, PEO-b-PS and amino acids, more preferably Pluronic F127, PEO-b-PS.
The method for preparing a catalyst support according to any one of claims 1-7, wherein in step a) the salt of the first metal is selected from the group consisting of palladium nitrate, potassium tetrachloropalladate (II) , palladium acetylacetonate, palladium (II) chloride, chloroplatinic acid, potassium tetrachloroplatinate, chloroauric acid, postaasium tetrachloroaurate.
The method for preparing a catalyst support according to any one of claims 1-8, wherein in step b) the aqueous solution is heated at a temperature in the range of 40 ℃ –200 ℃, preferably in the range of 60 ℃ –150 ℃..
The method for preparing a catalyst support according to any one of claims 1-9, wherein in step c) the second metal is loaded in an amount that the molar ratio of the second metal to the first metal is in the range of 1: 100 to 10: 1.
The method for preparing a catalyst support according to any one of claims 1-10, wherein in step c) the second metal component is selected from palladium nitrate, potassium tetrachloropalladate (II) , palladium acetylacetonate, palladium dichloride, chloroplatinic acid, potassium tetrachloroplatinate, chloroauric acid, potassium tetrachloroaurate, silver nitrate, nickel nitrate , copper nitrate, iron nitrate, zinc nitrate, cobalt nitrate, potassium ferricyanide, potassium hexacyanocobaltate, antimony trichloride, ferric chloride, zinc chloride, with the proviso that the second metal is different from the first metal.
The method for preparing a catalyst support according to any one of claims 1-11, wherein in step c) the second metal is loaded at a pH in the range of 2 –12.
The method for preparing a catalyst support according to any one of claims 1-12, wherein in step d) the reduction treatment is carried out under a normal pressure of a gaseous mixture of hydrogen and argon, hydrogen and nitrogen or hydrogen and a mixture of argon and nitrogen at a temperature in a range of 150 ℃ –800 ℃, wherein the volume ratio of hydrogen to argon, to nitrogen, or to the mixture of argon and nitrogen is in the range of 0.1%to 20%.
The method for preparing a catalyst support according to any one of claims 1-13, wherein the catalyst support is subjected to a shaping treatment.
The method for preparing a catalyst support according to claim 14, wherein the catalyst is shaped by tablet pressing under a pressure in the range of 1 bar –100 bar.