CN105858663A - Preparation method of bowl-shaped carbon-molybdenum carbide composite material - Google Patents

Abstract

The invention relates to the field of catalytic materials, in particular to a method for preparing a bowl-shaped carbon and molybdenum carbide composite material. or resorcinol or pyrogallol, formaldehyde solution, hydrazine hydrate, ammonium molybdate or phosphomolybdic acid, mixed and stirred, dried, and then calcined and heated to obtain a composite material. The preparation method of a bowl-shaped carbon and molybdenum carbide composite material of the present invention has simple preparation process, convenient operation, and easy control of process parameters. The obtained new composite material is expected to be used in the field of catalysis.

Description

A kind of preparation method of bowl-shaped carbon and molybdenum carbide composite material

technical field

The invention relates to the field of catalytic materials, in particular to a method for preparing a bowl-shaped carbon and molybdenum carbide composite material.

Background technique

Metal carbides are a new class of functional materials with high hardness, high melting point, good thermal stability and corrosion resistance, and have been applied in many fields. In the 1990s, Ledoux et al. reported that metal carbides have the characteristics of noble metals. They believed that in metal carbides, carbon atoms are filled in the metal lattice, causing changes in electron density, increasing the lattice parameters, and the lattice spacing. Increase, resulting in shrinkage of the d-band, increase in the density of d-electrons in the Fermi energy state, and thus have similar surface properties and absorption characteristics to noble metals. In recent years, carbides, especially molybdenum carbides, have attracted widespread attention as a new class of catalytic materials. In terms of catalytic activity, molybdenum carbide is similar to Pt noble metals in many aspects, especially its hydrogen evolution activity is comparable to noble metals such as Pt and Pd, and it is expected to become a substitute for noble metals.

With the deepening of research, new methods for preparing molybdenum carbide are constantly proposed and verified. At present, the preparation methods of molybdenum carbide mainly include the following: (1) temperature programmed reaction method, the precursor of molybdenum oxide is carbonized by temperature programming (TPRe) in light hydrocarbon or light hydrocarbon/H ₂ mixed gas. The method is simple and easy to empty and the product is relatively pure, but the method easily leads to carbonization of the surface area of the catalyst, and the specific surface area of the obtained molybdenum carbide is small. (2) Carbothermal reduction method, which reacts molybdenum oxide and an appropriate amount of carbon carrier in a protective atmosphere or a reducing atmosphere. The product obtained by this method has a larger specific surface area, but the reaction temperature is usually higher. (3) Solvothermal reduction method, which is to reduce molybdenum oxide to molybdenum carbide by using a substance with strong reducing ability (KBH4). This method is simple and easy to control, and the temperature is low, but the product is impure. (4) Metal precursor cracking The method is to use metal organic compounds and high temperature pyrolysis of the mixture of ammonium molybdate and hexamethylenetetramine, but the preparation of the precursor is complicated and the obtained particles are relatively large. In addition, there are reports of CVD, hydrothermal method, ultrasonic method, microwave method, etc., but these methods also have the problems of small yield, insufficient reaction, large product particles, and impure products. The above methods are limited and have their own characteristics, so there are big deficiencies in practical application, especially in the mass production of catalysts.

Contents of the invention

The invention aims to provide a novel composite catalytic material, specifically a method for preparing a bowl-shaped carbon and molybdenum carbide composite material.

The present invention is achieved through the following technical solutions: a preparation method of bowl-shaped carbon and molybdenum carbide composite material, which is achieved through the following steps:

(1) Fully dissolve cetyltrimethylammonium bromide in a mixture of ethanol and water with a volume ratio of 1:2 to form a 0.6-4g/L cetyltrimethylammonium bromide solution, Add silicon dioxide micronanospheres with a molar ratio of 0.1 to 0.6:5 to 6 to cetyltrimethylammonium bromide, and after uniform dispersion, add a molar ratio of 0.1 to cetyltrimethylammonium bromide ～0.6: 0.9～2 hydroquinone or resorcinol or pyrogallol, and then add formaldehyde solution, the molar ratio of formaldehyde and cetyltrimethylammonium bromide in the formaldehyde solution is 0.1～0.6 : 5~10; then add hydrazine hydrate with cetyltrimethylammonium bromide molar ratio of 0.1~0.6:7~14, and finally add cetyltrimethylammonium bromide molar ratio of 0.1~ 0.6: 1-6 ammonium molybdate or phosphomolybdic acid, after stirring at room temperature for 15-18 hours, dry to obtain solid powder;

(2) Calcining the solid powder obtained in step (1) at 700-900 ^o C for 3 hours to obtain the primary product of the composite material;

(3) Add the primary product obtained in step (2) to 2mol/L sodium hydroxide solution, and heat it at 100-120 ^o C for 18 hours to obtain a bowl-shaped carbon and molybdenum carbide composite material.

In the present invention, the function of cetyltrimethylammonium bromide is to disperse and modify silica micro-nanospheres; the function of silica micro-nanospheres is to act as a template to coat the surface with organic reaction products; The role of diphenol (resorcinol or phloroglucinol) and formaldehyde is to act as a reactant and provide a carbon precursor; the role of hydrazine hydrate is to provide the alkaline environment required for the reaction. Among them, cetyltrimethylammonium bromide, silica micro-nanospheres and post-treatment (heat treatment) make the carbon particles form a bowl-shaped carbon morphology.

The preparation method of a bowl-shaped carbon and molybdenum carbide composite material of the present invention has simple preparation process, convenient operation, and easy control of process parameters. The obtained new composite material is expected to be used in the field of catalysis.

Description of drawings

Fig. 1 is a scanning electron microscope image of a bowl-shaped carbon and molybdenum carbide composite material prepared by the method of the present invention.

Figure 2 is a transmission electron microscope image of the composite material.

Fig. 3 is the XRD pattern of the bowl-shaped carbon and molybdenum carbide composite material prepared by the method of the present invention.

detailed description

Example 1

A kind of preparation method of bowl-shaped carbon and molybdenum carbide composite material, it is realized by following steps:

(1) Fully dissolve cetyltrimethylammonium bromide in a mixture of ethanol and water with a volume ratio of 1:2 to form a 0.6g/L cetyltrimethylammonium bromide solution, add Silica micro-nanospheres with a molar ratio of 0.3:6 to cetyltrimethylammonium bromide, after uniform dispersion, add p-benzene with a molar ratio of 0.1:1.5 to cetyltrimethylammonium bromide Diphenol, then add formaldehyde solution, the molar ratio of formaldehyde in the described cetyltrimethylammonium bromide and formaldehyde solution is 0.6:5; Then add and cetyltrimethylammonium bromide molar ratio is 0.3: 14 hydrazine hydrate, finally add ammonium molybdate with a molar ratio of 0.1:3 to cetyltrimethylammonium bromide, stir at room temperature for 18 hours, and dry to obtain a solid powder;

(2) Calcining the solid powder obtained in step (1) at 700 ^o C for 3 hours to obtain the primary product of the composite material;

(3) The primary product obtained in step (2) was added to 2mol/L sodium hydroxide solution, and heated at 110 ^o C for 18 hours to obtain a bowl-shaped carbon and molybdenum carbide composite material.

Example 2

A kind of preparation method of bowl-shaped carbon and molybdenum carbide composite material, it is realized by following steps:

(1) Fully dissolve cetyltrimethylammonium bromide in a mixture of ethanol and water with a volume ratio of 1:2 to form a 2g/L cetyltrimethylammonium bromide solution, add Silica micro-nanospheres with a molar ratio of cetyltrimethylammonium bromide of 0.6:5, after uniform dispersion, add m-phthalamide with a molar ratio of 0.3:2 to cetyltrimethylammonium Phenol, then add formaldehyde solution, the molar ratio of formaldehyde and cetyltrimethylammonium bromide in the said formaldehyde solution is 0.1:8; hydrazine hydrate, and finally add phosphomolybdic acid with cetyltrimethylammonium bromide molar ratio of 0.3: 6, after stirring at room temperature for 15h, dry to obtain solid powder;

(2) Calcining the solid powder obtained in step (1) at 800 ^o C for 3 hours to obtain the primary product of the composite material;

(3) The primary product obtained in step (2) was added to 2mol/L sodium hydroxide solution, and heated at 120 ^o C for 18 hours to obtain a bowl-shaped carbon and molybdenum carbide composite material.

Example 3

A kind of preparation method of bowl-shaped carbon and molybdenum carbide composite material, it is realized by following steps:

(1) Fully dissolve cetyltrimethylammonium bromide in a mixture of ethanol and water with a volume ratio of 1:2 to form a 4g/L cetyltrimethylammonium bromide solution, add Silica micronanospheres with cetyltrimethylammonium bromide molar ratio of 0.1:5.5, after uniform dispersion, add phthalic trimethylammonium bromide with cetyltrimethylammonium bromide molar ratio of 0.6:0.9 Phenol, then add formaldehyde solution, the molar ratio of formaldehyde and cetyltrimethylammonium bromide in the said formaldehyde solution is 0.3:10; hydrazine hydrate, finally added phosphomolybdic acid in a molar ratio of 0.6:1 to cetyltrimethylammonium bromide, stirred at room temperature for 17 hours, and dried to obtain a solid powder;

(2) Calcining the solid powder obtained in step (1) at 900 ^o C for 3 hours to obtain the primary product of the composite material;

(3) The primary product obtained in step (2) was added to 2mol/L sodium hydroxide solution, and heated at 100 ^o C for 18 hours to obtain a bowl-shaped carbon and molybdenum carbide composite material.

Claims (1)

1. the preparation method of a bowl-shape carbon and molybdenum carbide composite, it is characterised in that it is through the following steps that realize:

(1) cetyl trimethylammonium bromide is completely dissolved in the mixed liquor of the second alcohol and water that volume ratio is 1:2 the cetyl trimethylammonium bromide solution of formation 0.6～4g/L, add and the silicon dioxide micro-nano ball that cetyl trimethylammonium bromide mol ratio is 0.1～0.6:5～6, after being uniformly dispersed, add and the hydroquinone that cetyl trimethylammonium bromide mol ratio is 0.1～0.6:0.9～2 or resorcinol or pyrogallol, it is subsequently adding formalin, in described formalin, formaldehyde and cetyl trimethylammonium bromide mol ratio are 0.1～0.6:5～10；Add and the hydrazine hydrate that cetyl trimethylammonium bromide mol ratio is 0.1～0.6:7～14, it is eventually adding and the ammonium molybdate that cetyl trimethylammonium bromide mol ratio is 0.1～0.6:1～6 or phosphomolybdic acid, after 15-18h is stirred at room temperature, it is dried to obtain pressed powder；

(2), by the pressed powder that obtains in step (1) 700～900^oCalcine 3 hours under C, obtain composite first product；

(3), the primary product that will obtain in step (2), join in 2mol/L sodium hydroxide solution, 100～120^oHeat treated 18 hours under C, i.e. obtain bowl-shape carbon and molybdenum carbide composite.