CN112142110A

CN112142110A - Preparation method of tungsten sulfide nanosheet with catalytic performance

Info

Publication number: CN112142110A
Application number: CN201910576942.7A
Authority: CN
Inventors: 宋吉明; 张冰倩; 陈京帅; 牛和林; 毛昌杰
Original assignee: Anhui University
Current assignee: Anhui University
Priority date: 2019-06-28
Filing date: 2019-06-28
Publication date: 2020-12-29
Anticipated expiration: 2039-06-28
Also published as: CN112142110B

Abstract

The invention discloses a preparation method of a tungsten sulfide nanosheet with catalytic performance, and particularly relates to a method for preparing tungsten sulfide by a colloid method, wherein the tungsten sulfide nanosheet has the property of catalyzing coupling reaction of benzylamine. Preparing loose nano sheets at a certain reaction temperature by using oleylamine as a solvent and a sulfur source and a tungsten source in a certain ratio as reactants; the nanosheet has the function of efficiently catalyzing benzylamine to be coupled into N-benzyl methylene benzylamine; in acetonitrile solvent, the yield of N-benzyl methylene benzylamine obtained by coupling benzylamine is as high as 98%. The catalyst has high catalytic efficiency, does not use noble metal, has low cost, and still maintains higher catalytic performance after 5 times of cycle experiments. The preparation method has the advantages of simple preparation process, easy operation, no need of using an organic template and a surfactant, and suitability for industrial production.

Description

Preparation method of tungsten sulfide nanosheet with catalytic performance

Technical Field

The invention belongs to the technical field of material preparation and application, and particularly relates to a tungsten sulfide nanosheet prepared by a colloid method, wherein the tungsten sulfide nanosheet has the property of catalyzing the coupling of benzylamine to generate imine.

Background

The research of the two-dimensional transition metal chalcogenide with atomic thickness reveals some interesting physical phenomena, including quantum spin Hall effect, valley polarization and two-dimensional superconductor, and brings potential application prospects for the fields of nano-electronics, photonics, sensing, energy storage, photoelectrons and the like. Song, et al (Carbon, 2019, 142, 697)706) An improved one-step hydrothermal method is adopted by the people to prepare the graphene-doped honeycomb WS with controllable appearance and excellent electrochemical performance₂As a composite anode material for lithium/sodium ion batteries; ruppert, et al (Nano Lett., 2017, 17, 644-₂Transient changes in the optical response of the monolayer film; li, et al (sensor. actual. B-chem., 2017, 240, 273-₂The nano sheet is used as a sensing material to develop a selective room temperature ammonia sensor; liu, et al (Nanoscale, 2017, 9, 5806-₂Deposited on the side of the tapered fiber and applied to the preparation of Saturable Absorbers (SA). The related patents are: (1) application No.: 201510005822.3, name: preparation of WS having solid lubrication by atomic layer deposition₂Thin film method for preparing WS having solid lubrication effect by atomic layer deposition₂A film, the application being in an effective period; (2) application No.: 201510263421.8, name: solvothermal method for preparing three-dimensional nano-layered structure WS₂And electrochemical application thereof, and preparation of three-dimensional nano-layered structure WS by adopting solvothermal method₂And applying the catalyst to lithium ion batteries and electrocatalytic hydrogen evolution reaction, wherein the application is in the validity period; (3) application No.: 201610480368.1, name: a tungsten disulfide nanosheet tubular aggregate and a preparation method thereof are disclosed, wherein WS is obtained by directly evaporating sulfur powder as a sulfur source in a vacuum tube furnace by using a thermal evaporation technology₂Nanosheet tubular aggregates, which application is in the process of being useful.

From the above description and examples, it can be seen that there are many methods for producing tungsten sulfide nanosheets, but most of the methods require high reaction conditions and have high technical difficulty, and few reports report that tungsten sulfide nanosheets are synthesized by a colloid method. Different from the reports in the above documents, the inventor adopts a colloid method, takes sulfur powder and tungsten hexachloride as raw materials, takes oleylamine as a solvent, and prepares a tungsten sulfide nano sheet; the material shows excellent catalytic performance on N-benzyl methylene benzylamine generated by coupling benzylamine.

Disclosure of Invention

The invention aims to provide a preparation method of a material with catalytic property and application of the material in catalyzing benzylamine to generate N-benzyl methylene benzylamine. The method has simple preparation process and good repeatability, can be synthesized in large quantities, and is suitable for industrial production. The prepared nano-flake has higher catalytic performance, and the conversion rate of catalytic benzylamine is up to 98%.

The preparation method of the nano-flake comprises the following steps:

A. adding a certain amount of sulfur source into oleylamine with a certain volume, and magnetically stirring at room temperature until sulfur powder is completely dissolved.

B. Adding a certain amount of tungsten source into a certain volume of oleylamine, heating to 60 ℃ after three cycles of vacuum nitrogen, degassing for 1 hour, and then heating the solution to 320 ℃.

C. Injecting the sulfur source precursor prepared in the step A into the step B, reacting for 60 minutes, placing reaction liquid into centrifuge tubes after the reaction is finished, adding 3 ml of trichloromethane dispersed reaction liquid into each centrifuge tube, adding 3 ml of ethanol for washing, using 6500 r/min for centrifugation for 5 minutes, repeatedly washing precipitates for 3 times, and drying the product in a vacuum drying oven at 60 ℃.

The reactant sulfur source is sulfur powder;

the reactant tungsten source is tungsten hexachloride.

The specific operation of catalyzing benzylamine coupling reaction by using the tungsten sulfide nanosheet prepared by the invention is as follows:

putting magnetons into a glass tube, adding a certain amount of tungsten sulfide product as a catalyst, adding a certain volume of benzylamine into the glass tube by using a liquid-transferring gun, then adding a certain volume of solvent (acetonitrile, n-hexane, cyclohexane, ethanol and water respectively), carrying out magnetic stirring reaction at 60 ℃ for 30 hours, centrifuging the catalyst, and carrying out quantitative analysis on the product by using gas chromatography to obtain the conversion rate.

The solvents of acetonitrile, normal hexane, cyclohexane and ethanol are in chromatographic purity grade;

the gas chromatography is Katsumadu GC-2010 plus.

The tungsten sulfide nanosheet prepared by the method has good catalytic performance on benzylamine coupling reaction, and the preparation and detection methods of the material are simple, can be synthesized in a large amount, are low in dosage and can be repeatedly used.

Description of the drawings:

fig. 1 is a Transmission Electron Micrograph (TEM) of tungsten sulfide nanosheets prepared in example 1;

figure 2 is an X-ray powder diffraction pattern (XRD) of tungsten sulfide nanosheets prepared in example 1;

FIG. 3 is an X-ray photoelectron spectroscopy (XPS) of tungsten sulfide nanosheets prepared in example 1;

FIG. 4 is a bar graph of the yield of catalytic benzylamine coupling in different solvents as in example 2;

FIG. 5 is a graph showing the effect of temperature on the catalytic reaction in example 2 (taking 6 hours as an example);

FIG. 6 is a graph of a cyclic experiment of the catalytic benzylamine coupling of example 2;

the specific implementation mode is as follows:

the invention is illustrated in detail below with reference to the examples:

example 1: preparing tungsten sulfide nano sheets:

adding 1 mmol of sulfur powder (0.032 g) into 3 ml of oleylamine solution, and magnetically stirring at room temperature until the sulfur powder is completely dissolved to obtain a sulfur source precursor. 0.5 mmol of tungsten chloride (0.199 g) was added to 30 ml of oleylamine solution, vacuum nitrogen was circulated three times to remove air in the reaction system, and the reaction system was heated to 60 ℃ and degassed by vacuum for 1 hour to remove low boiling substances in the reaction system. And (3) heating to 320 ℃, injecting the sulfur source precursor, reacting for 60 minutes, placing the reaction solution into centrifuge tubes after the reaction is finished, adding 3 ml of trichloromethane dispersed reaction solution into each centrifuge tube, adding 3 ml of ethanol, washing, rotating at 6500 rpm, centrifuging for 5 minutes, repeatedly washing the precipitate for 3 times, and drying in a vacuum drying oven at 60 ℃ to obtain the final product.

The obtained sample was subjected to morphology characterization by using Japanese Electron JEM-2100 Transmission (TEM), and the chemical composition of the sample was analyzed by using SmartLab 9 KW X-ray diffractometer (XRD) and Escalab 250Xi X-ray photoelectron Spectroscopy (XPS).

As can be seen from the transmission electron micrograph of the sample of figure 1,the product is formed by aggregation of a plurality of loose nano-flakes, and the thin layers are not sequentially and randomly stacked; FIG. 2 is an x-ray powder diffraction (XRD) pattern and hexagonal 2H-WS pattern of the product₂The PDF card numbers of the phases are consistent, and no obvious impurities exist. FIG. 3 is an XPS analysis of the W and S peaks in the product. From the left image, two characteristic peaks are observed, located in the vicinity of 32.2 eV and 34.3 eV, respectively, which may correspond to 4f of W_7/2And W4 f_5/2. In addition, a couple of doublets in the spectrum at 33.1 eV and 34.3 eV is attributed to WO₂W4 f in (1)_7/2And W4 f_5/2Or WO in non-stoichiometric proportions_3-xDue to surface oxidation of W under air exposure conditions. A broad peak corresponding to W5 p was also observed at 37.2 eV. From the XPS spectrum of the S on the right, two characteristic peaks, appearing at 161.9 eV and 163.2 eV, are observed, corresponding to S2 p_3/2And 2p_1/2。

Example 2: catalytic coupling of tungsten sulfide nanosheets to benzylamine:

the coupling method of benzylamine catalyzed by the tungsten sulfide nanosheet prepared by the invention comprises the following steps: 55 microliter benzylamine is measured and dissolved in 0.5 ml of different solvents, and the conversion rate of the reaction is tested after the reaction is carried out for a period of time at a certain temperature.

Selecting five solvents of acetonitrile, n-hexane, cyclohexane, ethanol and water for testing the catalytic performance.

The specific operation is as follows:

putting magnetons into a glass tube, adding 30 mg of tungsten sulfide product as a catalyst, adding 55 microliters (0.5 mmol) of benzylamine into the glass tube by using a pipette gun, then adding 0.5 ml of solvent, carrying out magnetic stirring reaction at 60 ℃ for 30 hours, adding the same solvent for dilution, centrifuging and separating the catalyst, and carrying out quantitative analysis on the product by using gas chromatography to obtain the yield.

As can be seen from the bar graph of FIG. 4, when the solvent is acetonitrile, the coupling of benzylamine gives N-benzylmethylenebenzylamine in yields of up to 98%, respectively. FIG. 5 is a graph showing the measured yields after the reactions were allowed to stand at 20 deg.C, 40 deg.C, 60 deg.C and 80 deg.C, respectively, for 6 hours. The yields of N-benzylmethylenebenzylamine were 11%, 25%, 51%, 84%, respectively, indicating that higher temperatures favor efficient reaction. Fig. 6 is a graph of the conversion and selectivity of each reaction after five times of catalyst recycling, and it can be seen from the graph that the catalyst still maintains excellent catalytic performance after repeated use for several times.

Claims

1. A preparation method of tungsten sulfide nano-sheets with catalytic performance comprises the specific steps of adding 1 mmol of sulfur powder into 3 ml of oleylamine, and magnetically stirring at room temperature until the sulfur powder is completely dissolved to obtain a sulfur source precursor; adding 0.5 mmol of tungsten chloride into 30 ml of oleylamine, circulating vacuum nitrogen for three times to remove air in a reaction system, heating to 60 ℃, vacuumizing and degassing for 1 hour to remove low-boiling-point substances in the reaction system; and (3) heating to 320 ℃, injecting the sulfur source precursor, reacting for 60 minutes, placing the reaction solution into centrifuge tubes after the reaction is finished, adding 3 ml of trichloromethane dispersed reaction solution into each centrifuge tube, adding 3 ml of ethanol, washing, rotating at 6500 rpm, centrifuging for 5 minutes, repeatedly washing the precipitate for 3 times, and drying in a vacuum drying oven at 60 ℃ to obtain the final product.

2. The tungsten sulfide nanosheet obtained by the preparation method according to claim 1 has catalytic performance on benzylamine coupling reaction, and the specific experimental steps are as follows: putting magnetons into a glass tube, adding 30 mg of tungsten sulfide product as a catalyst, adding 55 microliters of benzylamine into the glass tube by using a liquid transfer gun, then adding 0.5 ml of solvent, magnetically stirring at 60 ℃ for reaction for 30 hours, adding the same solvent for dilution, centrifugally separating the catalyst, and quantitatively analyzing the product by using gas chromatography to obtain the yield; the result shows that when the solvent is acetonitrile, the yield of the N-benzyl methylene benzylamine obtained by the coupling of benzylamine is as high as 98 percent, so that the method can be used for catalyzing the coupling of benzylamine to generate the N-benzyl methylene benzylamine.