CN113070064B

CN113070064B - Preparation method and application of graphite alkynyl monatomic catalyst

Info

Publication number: CN113070064B
Application number: CN202110332664.8A
Authority: CN
Inventors: 宋卫国; 于珈; 曹昌燕; 李玉良
Original assignee: Institute of Chemistry CAS
Current assignee: Institute of Chemistry CAS
Priority date: 2021-03-29
Filing date: 2021-03-29
Publication date: 2022-02-18
Anticipated expiration: 2041-03-29
Also published as: CN113070064A

Abstract

The invention discloses a preparation method and application of a graphite alkynyl monatomic catalyst, and belongs to the technical field of catalyst design and preparation. The preparation method of the graphite alkynyl monatomic catalyst comprises the following steps: and mixing hexaethynylbenzene with metal salt, and then carrying out heat treatment to obtain the graphite alkynyl monatomic catalyst. The method has the advantages of low cost, high efficiency, simple operation and good reproducibility.

Description

Preparation method and application of graphite alkynyl monatomic catalyst

Technical Field

The invention relates to the technical field of catalyst design and preparation, in particular to a preparation method and application of a graphite alkynyl monatomic catalyst.

Background

Monatomic catalysts are catalysts that anchor a single metal atom to a specific support, such as a metal oxide, metal sulfide, carbon material, covalent organic polymer, etc., thereby creating a single active site. Compared with the traditional catalyst, the monatomic catalyst has the following remarkable advantages: the atom utilization rate can reach 100% theoretically, the cost of the catalyst can be effectively reduced, and particularly the noble metal catalyst is used; has single catalytic active site, avoids side reaction caused by non-uniform composition of the particle catalyst, and has higher selectivity. In addition, the monatomic catalyst has the characteristic of single coordination structure of the homogeneous catalyst, and also has the characteristic of easy separation, recovery and recycling of the heterogeneous catalyst, and the homogeneous catalysis and the heterogeneous catalysis are linked, so that the monatomic catalyst has great prospect in industrial application.

2011, the billow task group first reported that Pt is loaded on FeO by single atom_xThe use of a carrier for CO oxidation, and on the basis of the concept of atomic catalysis, the subsequent report of various types of monatomic catalysts, is now a hot research problem in the field of catalysis.

The main problems faced by monatomic catalysts include: stably dispersing on the surface of the carrier; increasing the specific surface area of the support increases the exposure of active sites; and simple and rapid preparation. In order to solve the above problems, it is important to select a suitable vector. The carrier not only provides a support base for the atoms, but also must interact with the atoms to achieve stable single atoms that are prevented from migrating and aggregating at the surface to form clusters and even nanoparticles.

Theoretical research shows that the alkyne bond and the metal atom in the graphyne form a d-pi bond through electron transfer and the unique triangular hole of the graphyne has good functions of capturing and stabilizing the metal monoatomic atom, after the metal atom is adsorbed on the surface of the graphyne, valence electrons of the metal atom can be hybridized with three P orbitals of alkyne bond carbon, so that the metal atom and the graphyne have strong binding force, and the uniform anchoring of the metal monoatomic atom with catalytic activity on the two-dimensional graphyne can effectively improve the active area of the catalyst. However, the research on the graphite alkyne supported metal monatomic catalyst is slow in progress, the preparation method is limited, and at present, two methods are mainly adopted: electrochemical deposition and wet impregnation. The electrochemical deposition method takes a metal salt solution as electrolyte and graphite alkyne as cathode, and by applying proper voltage, metal ions are reduced and adsorbed on the graphite alkyne cathode to obtain the monatomic catalyst. Graphite alkyne monatomic catalysts of Fe, Ni, Pd, Rh, Cu have been prepared by this method at present. The method needs to reasonably control various factors such as electrolysis time, current intensity, electrolyte concentration and the like, and needs good experimental equipment. The wet impregnation method is to disperse the carrier into the solution, mix the carrier solution and the metal salt solution uniformly, make the metal adsorbed on the surface of the carrier by utilizing the interaction between the metal ions and the carrier, then make the metal ions converted into low valence state by high temperature reduction or adding reducing agent, the subsequent treatment makes the metal atoms agglomerated into particles easily. Only Pd and Pt single atoms are prepared by the method. Other methods for synthesizing monatomic at high temperature are not suitable for the graphyne substrate because the synthesized graphyne has more defects and the structure of the graphyne can be obviously changed under the high-temperature condition. Therefore, it is urgently needed to develop a simple and convenient synthesis method of the graphite alkynyl monatomic catalyst.

Disclosure of Invention

The invention provides a preparation method and application of a graphite alkynyl monatomic catalyst, which are used for solving the technical problem of difficulty in synthesis of graphite alkynyl monatomic. The method has the advantages of low cost, high efficiency, simple operation and good reproducibility.

The invention firstly provides a preparation method of a graphite alkynyl monatomic catalyst, which comprises the following steps: and mixing hexaethynylbenzene with metal salt, and then carrying out heat treatment to obtain the graphite alkynyl monatomic catalyst.

In the above preparation method, the hexaethynylbenzene is mixed with the metal salt in the presence of the solvent;

the solvent is at least one of water, tetrahydrofuran, acetone, ethanol, dichloromethane, pyridine and ethyl acetate;

the solvent may be tetrahydrofuran or acetone.

The mixing is carried out in an inert atmosphere; the inert atmosphere may be specifically a nitrogen atmosphere or an argon atmosphere.

In the above preparation method, the metal element in the metal salt is Cu, Pd or Ir; the metal salt is at least one of nitrate, sulfate, acetate, acetylacetone salt, chloride and iodide.

Specifically, the metal salt is anhydrous copper acetate, monohydrate copper acetate or acetylacetone copper.

In the preparation method, the mass ratio of the hexaethynylbenzene to the metal salt is 1000: 1-1000: 40; specifically, the ratio can be 1000:1, 1000:10, 1000:30 or 1000: 40.

The mixing is carried out under stirring conditions; the mixing temperature is room temperature, and the mixing time is 0.5-5 h; specifically, the mixing time is 2-3 h.

In the above preparation method, the method further comprises the step of spin-drying the solvent in the mixed solution before the heat treatment; specifically, the spin-drying is spin-drying in a rotary evaporator at room temperature.

In the above preparation method, the room temperature is known to those skilled in the art, and is generally 15-40 ℃.

In the above preparation method, the temperature of the heat treatment is above 90 ℃; specifically, the temperature can be 100-150 ℃; more specifically, it may be 120 ℃ or 140 ℃.

The heat treatment can be completed in a moment; specifically, the time period may be 1 to 10 seconds.

The invention also provides the graphite alkynyl monatomic catalyst prepared by the preparation method.

The application of the graphite alkynyl monatomic catalyst in benzene oxidation also belongs to the protection scope of the invention.

The invention also provides a benzene oxidation method, which comprises the following steps: and mixing benzene, acetonitrile, hydrogen peroxide and the graphite alkynyl monatomic catalyst for reaction.

In the method, the reaction temperature is 25-60 ℃ and the reaction time is 0.5-9 h.

Compared with the prior art, the invention has the following advantages:

(1) the method can quickly prepare the graphite alkynyl monatomic, is short in time consumption, can prepare the graphite alkynyl monatomic catalyst with better thermal stability within seconds under mild conditions, and saves time and cost;

(2) compared with the traditional monatomic catalyst, the copper monatomic catalyst prepared by the preparation method has unique coordination configuration and electronic structure, has excellent benzene oxidizing performance, improves the utilization rate of monatomic, and reduces the cost of the catalyst;

(3) the method adopts one-step pyrolysis to synthesize the graphite alkynyl monatomic catalyst, has simple and convenient preparation process and high preparation efficiency, and can realize certain large-scale production.

Drawings

FIG. 1 is a flow chart of a synthetic route of a graphite alkynyl monatomic catalyst provided by the invention;

FIG. 2 is a photograph of a spherical aberration corrected high angle annular dark field scanning transmission electron microscope (HAADF-STEM) of a copper monatomic catalyst supported on graphdiyne prepared in example 1 of the present invention;

FIG. 3 is a surface scan distribution plot of a copper monatomic catalyst supported on a graphitic alkyne prepared in example 1 according to the present invention;

FIG. 4 is an energy spectrum of a copper monatomic catalyst supported on graphite alkyne as prepared in example 1 of the present invention;

FIG. 5 is a graph of the benzene oxidation performance at 60 ℃ of a copper monatomic catalyst supported on graphite alkyne prepared in example 1 of the present invention.

Detailed Description

The present invention is described in further detail below with reference to specific embodiments, which are given for the purpose of illustration only and are not intended to limit the scope of the invention.

The experimental procedures in the following examples are conventional unless otherwise specified.

Materials, reagents and the like used in the following examples are commercially available unless otherwise specified.

The hexaethynylbenzene in the following examples was prepared according to the following literature: li, G.; li, Y.; liu, h.; guo, y.; li, Y.; zhu, D., Architecture of graphics nanoscales files chemical Communications 2010,46(19), 3256-.

FIG. 1 is a flow chart of a synthetic route of a graphite alkynyl monatomic catalyst provided by the invention, and the following example is carried out according to the steps of FIG. 1.

Example 1

100mg of hexaethynylbenzene was charged into a flask containing 40mL of tetrahydrofuran, placed under an inert atmosphere with nitrogen, and 1mg of anhydrous copper acetate was added. Stirring for 2h at room temperature, and then spin-drying the solvent at room temperature by a rotary evaporator; and then placing the obtained powder into a wide-mouth bottle which is preheated to 120 ℃ for polymerization to obtain the copper monatomic catalyst loaded on the graphite alkyne.

The bright spots distributed uniformly can be seen as copper atoms by a spherical aberration electron microscope (as shown in fig. 2). Fig. 3 is a morphology diagram and an element distribution diagram of a copper monatomic catalyst loaded on graphite alkyne, which are shot by a common transmission electron microscope, and it can be seen that carbon elements and copper elements are uniformly distributed in the catalyst. FIG. 4 is a total area spectrum of example 1 taken by transmission electron microscopy, and it can be seen that the catalyst contains carbon and copper.

Example 2

100mg of hexaethynylbenzene was charged into a flask containing 40mL of tetrahydrofuran, placed under an inert atmosphere with nitrogen, and 4mg of anhydrous copper acetate was added. Stirring for 2h at room temperature, and then spin-drying the solvent at room temperature by a rotary evaporator; and then placing the obtained powder into a wide-mouth bottle which is preheated to 120 ℃ for polymerization to obtain the copper monatomic catalyst loaded on the graphite alkyne.

Example 3

100mg of hexaethynylbenzene was added to a flask containing 40mL of acetone, placed under an inert atmosphere with nitrogen, and 0.1mg of anhydrous copper acetate was added. Stirring for 2h at room temperature, and then spin-drying the solvent at room temperature by a rotary evaporator; and then placing the obtained powder into a wide-mouth bottle which is preheated to 120 ℃ for polymerization to obtain the copper monatomic catalyst loaded on the graphite alkyne.

Example 4

100mg of hexaethynylbenzene was charged into a flask containing 40mL of tetrahydrofuran, placed under an inert atmosphere with nitrogen, and 3mg of copper acetate monohydrate was added. Stirring for 2h at room temperature, and then spin-drying the solvent at room temperature by a rotary evaporator; and then placing the obtained powder into a wide-mouth bottle which is preheated to 140 ℃ for polymerization to obtain the copper monatomic catalyst loaded on the graphite alkyne.

Example 5

100mg of hexaethynylbenzene was charged into a flask containing 40mL of tetrahydrofuran, placed under an inert atmosphere with nitrogen, and 3mg of copper acetate monohydrate was added. Stirring for 3h at room temperature, and then spin-drying the solvent at room temperature by a rotary evaporator; and then placing the obtained powder into a wide-mouth bottle which is preheated to 140 ℃ for polymerization to obtain the copper monatomic catalyst loaded on the graphite alkyne.

Example 6

100mg of hexaethynylbenzene was charged into a flask containing 40mL of tetrahydrofuran, placed under an inert atmosphere with nitrogen, and 3mg of copper acetylacetonate was added. Stirring for 2h at room temperature, and then spin-drying the solvent at room temperature by a rotary evaporator; and then placing the obtained powder into a wide-mouth bottle which is preheated to 140 ℃ for polymerization to obtain the copper monatomic catalyst loaded on the graphite alkyne.

Example 7

The copper monatomic catalyst supported on graphite alkyne prepared in example 1 was used for benzene oxidation.

Benzene (300. mu.L, 3.38mmol), acetonitrile (6mL), hydrogen peroxide (5mL, 30 wt%) and the catalyst prepared in example 1 (10mg) were mixed, stirred at 60 ℃ for 9h, n-tridecane (100. mu.L) was added as an internal standard, extracted with ethyl acetate (10mL), and the supernatant was aspirated and filtered to give a reaction product.

The reaction products were analyzed by gas chromatography and gas chromatography-mass spectrometry, respectively (see FIG. 5), and it was found from FIG. 5 that the conversion of benzene was 86% and the selectivity of phenol was 96%.

Claims

1. A preparation method of a graphite alkynyl monatomic catalyst comprises the following steps: mixing hexaethynylbenzene with metal salt, and then carrying out heat treatment to obtain the graphite alkynyl single-atom catalyst;

mixing the hexaethynylbenzene with a metal salt in the presence of a solvent;

the mixing is carried out in an inert atmosphere;

the method also comprises the step of spin-drying the solvent in the mixed solution at room temperature before the heat treatment;

the metal salt is anhydrous copper acetate, monohydrate copper acetate or acetylacetone copper;

the temperature of the mixing is room temperature;

the temperature of the heat treatment is 100-150 ℃;

the heat treatment was performed in jars.

2. The method of claim 1, wherein: the mass ratio of the hexaethynylbenzene to the metal salt is 1000: 1-1000: 40;

the mixing time is 0.5-5 h.

3. The graphite alkynyl monatomic catalyst produced by the production method according to claim 1 or 2.

4. Use of the graphene-based monatomic catalyst of claim 3 in benzene oxidation.

5. A method of benzene oxidation comprising the steps of: mixing benzene, acetonitrile, hydrogen peroxide and the graphite alkynyl monatomic catalyst according to claim 3, and reacting.

6. The method of claim 5, wherein: the reaction temperature is 25-60 ℃ and the reaction time is 0.5-9 h.