KR20210008215A - metallic naonoparticle bound to the surface of mesoporous silica support having ordered 3-D pore structure and method for preparation thereof - Google Patents

Abstract

The present invention relates to a mesoporous silica support having an ordered three-dimensional pore structure, a method for preparing a composite including a metallic nanoparticle immobilized on a surface inside and outside the same, and a metallic nanoparticle immobilized on a mesoporous silica support having a three-dimensional pore structure prepared thereby. The method comprises: (a) introducing a multi-amine group onto a surface of a mesoporous silica support having an ordered three-dimensional pore structure; (b) introducing metal ions by contact of an active metal precursor with the mesoporous silica support having an ordered three-dimensional pore structure on which the multi-amine group is immobilized; and (c) reducing the adsorbed metal ions to form metal nanoparticles. A process is simplified and a surface area is increased by using a silica support having a three-dimensional shape, and thus can be applied as a heterogeneous catalyst.

Description

Metallic naonoparticle bound to the surface of mesoporous silica support having ordered 3-D pore structure and method for preparation thereof}

Immobilizing multiple amine groups on the surface of the mesoporous silica support having an ordered three-dimensional pore structure; Introducing metal ions by contacting the mesoporous silica support having a regular three-dimensional pore structure in which the multiamine groups are immobilized with an active metal precursor; And comprising the step of forming metal nanoparticles by reducing the adsorbed metal ions, comprising a mesoporous silica support having a regular three-dimensional pore structure and metal nanoparticles fixed to the inner and outer surfaces of the pores It relates to a method of manufacturing a composite and a composite produced thereby.

In the case of a mesoporous silica material, due to the structural advantages of a large surface area and regular pores, there is an advantage in the aspect of application as a catalyst carrier.

Mesoporous silica material has many silanol (Si-OH) groups on the pore surface. Therefore, an alkoxy silane having an organic functional group ((R'O) ₃ Si(CH ₂ ) _n R, R'= methyl or ethyl, R=N, O, S, P, or an aliphatic hydrocarbon chain containing an atom such as C Cyclic aliphatic groups, aromatic groups or derivatives thereof) can be modified through chemical reactions. These modified nanoporous silica materials have a regular pore arrangement, uniform pore size, and high surface area, and have very high potential for application in macromolecular adsorption, enzyme adsorption, metal ion adsorption, catalysis, sensors, drug delivery, nanomaterial manufacturing, etc. Have.

The principle of physical adsorption on the silica support is that the isoelectric point of electrostatic attraction and hydrogen-bonded silica is pH 2, and in an environment greater than 2, silica has negative (-). Therefore, it can be physically adsorbed and immobilized by metal ions and electrostatic attraction. The only method for producing alloy nanoparticles on a metal catalyst support is a recently published strong electrostatic adsorption (SEA). The SEA method is a method of producing single metal or double metal nanoparticles on a support after adsorbing charged metal precursors onto an oxide or carbon surface having an opposite charge, followed by drying and reduction processes.

In order to introduce a charge opposite to that of the metal precursor to the surface of the support, the method (SEA) needs to carefully adjust the pH, but since the pH value representing the maximum adsorption efficiency is different for each metal, there is a problem that a process to be investigated for each metal is required. In addition, as investigated through the present method, most metal precursors have a maximum adsorption value at a high pH, but in such basic conditions, a fatal disadvantage of melting the silica support may be caused. In addition, so far, the SEA method has not used a mesoporous silica support.

The adsorption equilibrium constant (K) between the silica support and the metal precursor by the electrostatic adsorption method under basic conditions is 10 ⁴ or less. That is, most of them can be adsorbed in a single layer on a silica support, but this corresponds to a weaker force than a coordination bond between a metal ion and an amine ligand. For this reason, a drying process is essentially accompanied after adsorption, and there is a problem of using hydrogen gas as a gas in the reduction process.

In addition, in order to obtain maximum efficiency in the adsorption process, adsorption must be performed under a high pH condition, but there is a stability problem in that the silica support melts under a high basic condition (pH> 11).

Patent Document 1 Korean Patent Registration No. 10-1926354 Patent Document 2 Korean Patent Registration No. 10-1812671

As a result of intensive research efforts to simplify the process and to solve the problems of the conventional electrostatic adsorption method, the present inventors are irrelevant to conditions such as pH based on increased bonding strength by introducing metal ions through coordination by modifying the surface of the silica support with a multiamine group. It was confirmed that metal ions can be adsorbed in a way, and the present invention was completed.

A catalyst having a high specific surface area with a regular three-dimensional pore structure while simplifying the process due to the fact that the production process of the present invention can be performed even when the production process is not basic conditions, the pH optimization process is eliminated, and a drying process is not required separately. As it can be produced, it is intended to broaden its application range as a catalyst.

A first aspect of the present invention comprises the steps of: (a) introducing multiple amine groups to the surface of the mesoporous silica support having an ordered three-dimensional pore structure; (b) introducing metal ions by contacting the mesoporous silica support having a regular three-dimensional pore structure in which the multiamine groups are immobilized with an active metal precursor; And (c) reducing the adsorbed metal ions to form metal nanoparticles, comprising a mesoporous silica support having a regular three-dimensional pore structure, and metal nanoparticles fixed to the inner and outer surfaces of the pores thereof. It provides a method for producing a composite containing.

A second aspect of the present invention is a composite comprising a mesoporous silica support having a regular three-dimensional pore structure and metal nanoparticles fixed on the inner and outer surfaces of the pores, which are prepared by the manufacturing method of the first aspect. to provide.

A third aspect of the present invention provides a catalyst composition for hydrogen peroxide synthesis reaction comprising as an active ingredient a complex including a mesoporous silica support having a regular three-dimensional pore structure and metal nanoparticles fixed on the inner and outer surfaces of the pores do.

Hereinafter, the present invention will be described.

The manufacturing process of the present invention can be carried out even in non-basic conditions, the pH optimization process is eliminated, and the drying process is not required, so the process is simplified and the metal fixed on the mesoporous silica support having a regular three-dimensional pore structure. The present invention has been completed as a catalyst and manufacturing process with high utility since it can generate nanoparticles.

The present invention is a novel method of adsorbing one or more metal ions through coordination by modifying the surface of a silica support with multiple amine groups, (a) on the surface of a mesoporous silica support having an ordered three-dimensional pore structure. Introducing a multiamine group; (b) introducing metal ions by contacting the mesoporous silica support having a regular three-dimensional pore structure in which the multiamine groups are immobilized with an active metal precursor; And (c) reducing the adsorbed metal ions to form metal nanoparticles, comprising a mesoporous silica support having a regular three-dimensional pore structure, and metal nanoparticles fixed to the inner and outer surfaces of the pores thereof. It provides a method for producing a composite containing.

The mesoporous silica support having a regular three-dimensional pore structure has a higher specific surface area than that of a general silica support, and may contribute to catalytic stability of metal nanoparticles due to structural characteristics.

The pore structure may have a cylinder or gyroid shape, but is not limited thereto. For example, the pore structure can be controlled by varying the molar ratio of BuOH and HCl used in the preparation of other mesoporous silica supports by hydrothermal synthesis.

Preparation of the silica support having the cylinder structure is prepared by a hydrothermal synthesis method using a structure inducing agent: silica precursor: BuOH: HCl: water in a molar ratio of 1: 65 to 75: 65 to 75: 380 to 400: 10,000 to 13,000 Can be.

The preparation of the silica support having the gyroid structure is a hydrothermal synthesis method in which the mixing molar ratio of the old guiding agent: silica precursor: BuOH: HCl: water is 1: 65 to 75: 90 to 100: 80 to 90: 10,000 to 13,000. Can be prepared by

보다 구체적으로 120 내지 140

에서 12 내지 48시간동안 가열하는 것일 수 있으나, 이에 제한되지 않는다. The hydrothermal synthesis is one of the liquid phase synthesis methods and collectively refers to a process of synthesizing a substance using water or an aqueous solution under high temperature and high pressure. In other words, it is a single crystal synthesis method that relies on the solubility of minerals under a high temperature aqueous solution and high pressure, and is a synthesis method commonly used when direct melting is difficult. For example, in the present invention, after transferring the Teflon container containing the solution to a hydrothermal reactor, 110 to 150

More specifically 120 to 140

It may be heated for 12 to 48 hours at, but is not limited thereto.

The structure directing agent may be a block copolymer having hydrophilic and hydrophobic blocks. Materials that can be used as structure inducing agents in the manufacturing method of the present invention are polyethylene oxide-block-polystyrene block copolymer (poly(ethylene oxide)-bpoly(styrene)), polyethylene oxide-block-polymethylmethacrylate block copolymer (poly(ethylene oxide)-bpoly(styrene)). (ethylene oxide)-bpoly(methyl methacrylate)), polyisoprene-block-polyethylene oxide block copolymer (poly(isoprene)-bpoly(ethylene oxide)), polyisoprene-block-polystyrene-block-polyethylene oxide block copolymer Polye (isoprene)-b-poly(styrene)-b-poly(ethylene oxide); P123), and pluronic-based commercial block copolymers (Polyoxypropylenepolyoxyethylene Block Copolymer; F127) selected from the group consisting of It may be one or more, but is not limited thereto.

For example, a polyisoprene-block-polestyrene-block-polyethylene oxide (P123) block copolymer may be used to prepare a silica support having a regular three-dimensional pore structure in the form of a cylinder or a gyroid.

The silica precursor may be at least one selected from the group consisting of tetramethyl orthosilicate, tetraethylorthosilicate, tetrapropyl orthosilicate, and tetrabutyl orthosilicate. For example, tetraethyl orthosilicate (TEOS) may be used, but is not limited thereto.

The polyamine group may be a chelating agent capable of coordinating bonds as used for surface modification of a silica support. According to the conventional electrostatic adsorption method, most metal precursors have a maximum adsorption value at a high pH, and the adsorption equilibrium constant (K) between the silica support and the metal precursor is 10 ⁴ or less under basic conditions. This corresponds to a weaker force than a coordination bond between a metal ion and an amine ligand. In the present invention, a metal can be introduced into the inner and outer surfaces of the pores of the silica support through coordination bonding, which is a stronger bond than the electrostatic adsorption method. For example, ethylene diamine (EDA), which is a bidentate ligand, may be used, but is not limited thereto. More specifically, for the introduction of EDA, N-(3-(trimethoxysilyl)propyl)ethylenediamine (N-[3-(Trimethoxysilyl)propyl]ethylenediamine; PEDA), a silica support, and a toluene solvent may be mixed. .

The active metal may be one metal or two or more metal alloys. In the conventional electrostatic adsorption method, the pH must be carefully adjusted to introduce a charge opposite to that of the metal precursor to the surface of the support, because the pH value representing the maximum adsorption efficiency is different for each metal. Therefore, according to the above method, it is particularly difficult to introduce two or more kinds of metals into the silica support. The present invention solves the conventional problem by confirming that a separate pH adjustment is not required by introducing a multiamine group to the surface of a silica support to include metal precursors through coordination bonds. For example, it may be a Pd type 1 metal nanoparticle or an alloy nanoparticle of Pd/Pt, but is not limited thereto. More specifically, in the case of Pd and Pt alloys, when only Pt is used, when Pt is oxidized, there is a problem that it becomes a gaseous phase, making it difficult to immobilize, and the stability of Pt is improved through the alloy with Pd, thereby extending the catalyst life. In the case of Pd-Pt dissimilar metal nanoparticles, it is possible to improve the stability of the catalyst and improve the recyclability of the catalyst. In particular, if Pt, which has relatively low stability, is alloyed with Pd, the stability of Pt is improved and the catalyst life can be extended.

The step (b) may be performed in an aqueous solution condition other than a basic condition.

Although there has been a problem in that the stability of the silica support is reduced because the conventional electrostatic adsorption method must be performed under basic conditions, the present invention can solve such a problem. In addition, after step (b), a separate drying process is not required. In the case of the conventional electrostatic adsorption method, the adsorption power of the metal nanoparticles on the silica support was weak, and this was necessary, but it can be performed without a separate drying process due to an increase in adsorption power due to coordination bonding. Whether or not the nano-metal particles are adsorbed in the silica support can be confirmed through the absorption signal appearing at 230 to 300 nm, before the silica support is added, disappears after the silica support is placed, as shown in FIG. 3. This is because Pt-Pd forms a complex through a stable coordination bond with a chelate having a diamine group located on the surface of the silica support.

The present invention provides a composite including a mesoporous silica support having a regular three-dimensional pore structure and metal nanoparticles fixed on the inner and outer surfaces of the pores. The metal may be one metal or two or more alloys.

The specific surface area of the silica support having the regular three-dimensional pore structure may be 300 m ² /g or more, and the pore size may be 5.5 to 7.5 nm, but is not limited thereto. For example, those having a specific surface area value of 300 m ² /g or more and a pore size of 5.6 to 7.1 nm may be included.

The metal nano may have a size of 3 nm or less, but is not limited thereto. For example, the size of the metal nanoparticles may be 2 nm or less.

The prepared composite may be applied to a catalytic reaction related to an oxygen reduction reaction, a diesel oxidation catalytic reaction, a hydrogen peroxide synthesis catalytic reaction, etc., but is not limited thereto. The present invention confirmed the catalytic reaction of hydrogen peroxide synthesis of Pd nanoparticles fixed on a gyroid-structured silica support in Example 4 as a specific example.

The manufacturing method of the present invention can adsorb metal ions irrespective of conditions such as pH based on increased bonding strength by modifying the surface of the support with a multiamine group in preparing a composite in which alloy nanoparticles are supported on a mesoporous silica support. Alloy nanoparticles of 3 nm or less can be prepared.

1 is a graph for confirming whether or not metal ions, which are metal nanoparticle precursors, are introduced into a silica support through ultraviolet absorption spectroscopy.
2 is an electron microscope and EDX (Energy Dispersive X-ray spectroscopy) photographs of Pd-Pt alloy nanoparticles prepared in a cylindrical silica support.
3 is an electron microscope and EDX photograph of Pd-Pt alloy nanoparticles prepared in a gyroid silica support.

Hereinafter, the present invention will be described in more detail through examples. These examples are for explaining the present invention more specifically, and the scope of the present invention is not limited to these examples.

Preparation Example 1. Preparation of a mesoporous silica support having a three-dimensional pore structure

1.1 Mesoporous silica support with cylinder structure

P123, a polyethylene glycol-polypropylene glycol-polyethylene glycol block copolymer, was used as a structure inducing agent, and its reaction product was P123/ TEOS/ BuOH/ HCl/ H ₂ O = 0.017/ 1.2/ 1.21/ 6.66/ 195 Having a cylinder structure using the molar ratio of A mesoporous silica support was prepared.

에서 24시간 동안 가열하였다. 수열반응 후, 여과하여 흰색의 고체를 얻어, 100

에서 12시간 동안 테프론 페트리디쉬 상에서 건조하였다. 메조크기의 기공을 만들기 위해, 수득한 시료를 100

에서 1시간, 분당 1

의 속도로 450

까지 가열하고, 450

에서 3시간 더 가열을 진행하여, 유기물을 제거하였다.Specifically, in a Teflon reactor, 5 g of P123, 179 g of water, and 35.23 g of hydrochloric acid having a weight mass ratio of 35 were added, followed by stirring at room temperature for 1.5 hours. Thereafter, 4.51 g of BuOH was added, followed by stirring at room temperature until the solution became transparent. Then, 12.68 g of tetramethylorthosilicate (TEOS) was added, and the mixed solution was stirred at room temperature for 24 hours. Thereafter, the Teflon bottle containing the solution was transferred to a hydrothermal reactor, and then 130

Heated at for 24 hours. After the hydrothermal reaction, it was filtered to obtain a white solid, 100

It was dried on a Teflon Petri dish for 12 hours. In order to make meso-sized pores, 100

At 1 hour, 1 per minute

At a speed of 450

Heated up to 450

The heating was further performed for 3 hours to remove organic matter.

1.2 Mesoporous silica support with gyroid structure

P123, a polyethylene glycol-polypropylene glycol-polyethylene glycol block copolymer, was used as the structure inducing agent, and the reaction product thereof was P123/ TEOS/ BuOH/ HCl/ H ₂ O = 0.017/ 1.2/ 1.61/ 1.46/ 195 Having a gyroid structure using the molar ratio of A mesoporous silica support was prepared. Only the molar ratio of BuOH and HCl was different, and the synthesis was carried out in the same manner as in Preparation Example 1.1.

Example 1. Immobilization of diamine groups on the surface of a mesoporous silica support having a regular three-dimensional pore structure

N-(3-(trimethoxysilyl)propyl)ethylenediamine (N-(3-(trimethoxysilyl)propyl)ethylenediamine; PEDA) and the silica support prepared according to the above Preparation Example were reacted for 18 hours in a toluene solvent, ethylene Diamine groups were introduced on the silica surface. The reaction was carried out by adjusting the mass ratio of PEDA to silica (PEDA/SiO ₂ ) to 0.4.

Example 2. Introduction of active metal ions into a mesoporous silica support having a three-dimensional pore structure in which a diamine group is immobilized

As Pd and Pt precursors soluble in aqueous solution, PdCl ₄ ^2- and PtCl ₆ ^2- were selected, respectively, and used in the metal ion introduction process. Specifically, of PtCl ₆ ^2- K ₂ PtCl ₆ was used as a reagent, and the PdCl ₄ ^2- aqueous solution was prepared by mixing PdCl ₂ and NaCl in an aqueous solution at a molar ratio of 1:2.

Metal ions were adsorbed by immersing the mesoporous silica support prepared according to Example 1 in a 1:1 mixture of PdCl ₄ ^2- aqueous solution and PtCl ₆ ^2- aqueous solution prepared as described above.

Whether the metal ions were introduced into the support was confirmed through ultraviolet absorption spectroscopy (FIG. 1), and the results are shown in FIG. Before the silica support was added, the absorption signal appearing at 230 to 300 nm disappeared after the silica support was placed. This indicates that Pd and Pt formed a complex through a stable coordination bond with an ethylene diamine group located on the silica surface.

Example 3. Formation of metal nanoparticles by reduction of active metal ions introduced into three-dimensional mesoporous silica support

The reaction mixture of Example 2 was centrifuged to remove the aqueous solution, and a reduction reaction was performed by adding an aqueous solution of NaBH _{4 as a} reducing agent to form Pd-Pt alloy nanoparticles on a silica support.

In addition, by obtaining a transmission electron microscope image of the composite in which the alloy nanoparticles were introduced into the pores inside and outside the pores of the silica support according to Examples 1 to 3, it was confirmed that the formed metal particles exist on the inside and outside the pores ( 2 and 3). At this time, the size of the synthesized alloy nanoparticles was 2 nm or less, and it was confirmed that the dispersion in the silica support was remarkably excellent when the metal particles were introduced due to the high specific surface area of the silica support. Furthermore, as a result of obtaining the content (mass%) of Pd and Pt contained in the composite sample prepared through ICP-AES (inductively-coupled plasma atomic emission spectrometer) mass spectrometry, Pd was 2.65% and Pt was 4.6%, Converting this to the number of moles, it was found that the ratio equal to the number of 1:1 moles entered was well maintained. By comparing the transmission electron microscope image with the result of elemental analysis through Energy-Dispersive X-ray spectroscopy (EDX), it was confirmed that Pd and Pt metal were found at the same location, which is Pd-Pt alloy nanoparticles. It was confirmed that was successfully manufactured on the inner and outer surfaces of its pores (FIGS. 2 and 3 ).

Example 4. Catalytic reaction of hydrogen peroxide synthesis of Pd nanoparticles introduced on a mesoporous gyroid structure silica support

Hydrogen peroxide synthesis reaction was performed using a composite having a weight ratio of 0.5% in which Pd nanoparticles were introduced into the pores of the gyroid structure silica support according to Examples 1 to 3 as a heterogeneous catalyst. Before the catalytic reaction, in order to remove organic substances present in the catalyst, it was treated at 500° C. for 2 hours in the presence of oxygen, and then treated at 150° C. for 1 hour in a 10% hydrogen atmosphere, followed by Pd reduction. The production amount according to the use of the Pd catalyst used in the hydrogen peroxide synthesis reaction was investigated, and the results are shown in Table 1.

catalyst
(Pd wt%) Condition Pd mass
(mg) H ₂
Conversion rate (%) H ₂ O ₂ selectivity
(%) H ₂ O ₂ production amount
(mmol/g _pd h) 0.5
(0.599) 500℃
2 hours 0.15 19.75 59.28 5882.717 0.3 23.84 58.06 3537.327 0.5 26.61 26.17 1047.19

Experimental Example 1. Characterization

As a result of analyzing the mesoporous silica support having a regular three-dimensional structure prepared in Preparation Examples 1.1 and 1.2 through a nitrogen adsorption experiment, the specific surface area value in both was 300 m ² /g or more, and the pore size was 5.6 to It appeared to be 7.1 nm. Further, the structures of the silica support including the double metal nanoparticles prepared in Examples 1 to 3 were structurally analyzed using an X-ray scattering method, and the results are shown in FIGS. 2 and 3. As shown in FIGS. 2 and 3, it was confirmed that the cylinder and gyroid structure of the support itself were maintained even after the alloy metal particles were formed.

Claims (15)

(a) introducing multiple amine groups to the surface of the mesoporous silica support having an ordered three-dimensional pore structure;
(b) introducing metal ions by contacting the mesoporous silica support having a regular three-dimensional pore structure in which the multiamine groups are immobilized with an active metal precursor; And
(c) comprising the step of reducing the adsorbed metal ions to form metal nanoparticles, comprising a mesoporous silica support having a regular three-dimensional pore structure, and metal nanoparticles fixed to the inner and outer surfaces of the pores Method for producing a composite.
The method of claim 1, wherein the mesoporous silica support structure having a regular three-dimensional pore structure has pores in the form of a cylinder or a gyroid.
The method of claim 1, wherein the mesoporous silica support having a regular three-dimensional pore structure is prepared by hydrothermal synthesis using a structure directing agent, a silica support, BuOH, HCl, and water.
The method of claim 3, wherein the mesoporous silica support having a regular three-dimensional pore structure is a composition inducing agent: silica precursor: BuOH: HCl: water 1: 65 to 75: 65 to 75: 380 to 400: 10,000 to 13,000 or 1 : 65 to 75: 90 to 100: 80 to 90: It is prepared using a molar ratio of 10,000 to 13,000, a method for producing a composite.
The method of claim 1, wherein the polyamine group in step (a) is introduced into the silica surface by covalent bond by reacting with an alkoxysilane derivative containing two or more amine groups spaced apart from C _1-3 alkylene in a single molecule. That is, a method for producing a composite.
The method of claim 1, wherein in step (a), the mesoporous silica support having a regular three-dimensional pore structure is N-(3-(trimethoxysilyl)propyl)ethylenediamine (N-(3-(trimethoxysilyl)propyl). To be carried out by immersing in a solution in which ethylenediamine; PEDA) is dissolved, the method of manufacturing a composite.
The method of claim 1, wherein the active metal is palladium (Pd), platinum (Pt), or an alloy thereof.
The method of claim 1, wherein in the step (b), the multiamine group and the metal ion are coordinated. The method of claim 1, wherein the step (b) does not require a basic condition.
The method of claim 1, wherein there is no drying process after step (b).
A composite comprising a mesoporous silica support having a regular three-dimensional pore structure and metal nanoparticles fixed on the inner and outer surfaces of the pores, which are prepared by the manufacturing method of any one of claims 1 to 10.
The composite of claim 11, wherein the silica support has a specific surface area of 300 m ² /g or more.
The composite of claim 11, wherein the silica support has an average pore size of 5.5 to 7.5 nm.
The composite of claim 11, wherein the nanoparticles have an average diameter of 3 nm or less.
A catalyst composition for hydrogen peroxide synthesis reaction comprising as an active ingredient a composite including a mesoporous silica support having a regular three-dimensional pore structure and metal nanoparticles fixed on the inner and outer surfaces of the pores.

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