CN111747413A

CN111747413A - Preparation method of pellet-shaped molybdenum carbide easy to separate and recover

Info

Publication number: CN111747413A
Application number: CN201910247575.6A
Authority: CN
Inventors: 林少华; 范舒婷; 刘国华; 陈阳; 肖冬梅; 陈忱
Original assignee: Nanjing Forestry University
Current assignee: Nanjing Forestry University
Priority date: 2019-03-27
Filing date: 2019-03-27
Publication date: 2020-10-09
Anticipated expiration: 2039-03-27
Also published as: CN111747413B

Abstract

A preparation method of pellet-shaped molybdenum carbide easy to separate and recover comprises the following steps of mixing inorganic mineral clay powder and molybdenum carbide powder according to a mass ratio of (0.5-3) to 1, and mixing the mixture with sodium alginate, polyethylene glycol and methyl cellulose according to a mass ratio of: fully mixing 20: 0.5-3.5: 0.05-0.15: 0.05-1.5: 12-20 to form a plastic mixed material; then pelleting and drying are carried out; then roasting for 0.5-2h at 500-800 ℃ under the protection of nitrogen or helium; and finally naturally cooling to room temperature to obtain the pill-shaped molybdenum carbide which is easy to separate and recover. The pill-shaped molybdenum carbide prepared by the method keeps the catalytic activity of the molybdenum carbide and has the advantages of simple preparation process, mild conditions, high mechanical strength of particles, controllable particle size and the like.

Description

Preparation method of pellet-shaped molybdenum carbide easy to separate and recover

Technical Field

The invention relates to a preparation method of pellet-shaped molybdenum carbide, which is easy to separate and recover, simple in preparation process and high in catalytic activity, and belongs to the technical field of energy sources and catalytic materials.

Background

In recent years, carbides have attracted considerable attention as catalytic materials. Molybdenum carbide is a "interstitial alloy" formed by embedding C atoms with a small radius into a metal Mo atom lattice with a large radius, thereby forming a simple lattice structure. The metal Mo atom transfers electrons to the C atom, and three chemical bonds of metallic bond, ionic bond and covalent bond can be formed, so that the metal Mo shows excellent performance after being carbonized, which is different from that of a parent metal. Molybdenum carbide not only has noble metal-like catalytic properties, but also has good catalytic properties in the aspects of hydrogenation reaction, hydrogen production reaction, oxygen reduction reaction, desulfurization reaction, denitrification reaction and the like, and also has excellent properties of high melting point, high stability, roasting resistance and the like, so that the molybdenum carbide also attracts attention in various mechanical and environment-friendly fields with high temperature resistance, abrasion resistance and chemical corrosion resistance. Molybdenum carbide has been recently favored by researchers because of its high price advantage over noble metals of the platinum group and its excellent anti-poisoning properties.

The preparation method of the molybdenum carbide mainly comprises the following steps: temperature programmed reaction method, thermal decomposition method, liquid phase reaction method, chemical vapor deposition method, organic-inorganic hybridization method, ultrasonic method, microwave preparation method, etc. Or modification is carried out on the molybdenum carbide, such as doping of hetero atoms and addition of metal additives. The prepared molybdenum carbide is mainly nano-grade particles, has large specific surface area and high catalytic efficiency, but has the problems of easy loss, difficult separation and recovery and the like when applied in some fields, such as the environmental protection field.

Disclosure of Invention

The technical problem is as follows: the invention aims to disclose a preparation method of pellet-shaped molybdenum carbide, which is easy to separate and recover. The pill-shaped molybdenum carbide prepared by the method keeps the catalytic activity of the molybdenum carbide and has the advantages of simple preparation process, mild conditions, high mechanical strength of particles, controllable particle size and the like.

The technical scheme is as follows: the preparation method of the pellet-shaped molybdenum carbide easy to separate and recover comprises the following steps:

fully mixing inorganic mineral clay powder and molybdenum carbide powder, and fully mixing the mixture with sodium alginate, polyethylene glycol and methyl cellulose; adding deionized water, and stirring to obtain plastic mixed material; then pelletizing and granulating the obtained plastic mixed material; then drying the pellet particles; and finally, roasting and naturally cooling under the protection of inert gas, thereby obtaining the pill-shaped molybdenum carbide which is easy to separate and recover.

When materials are mixed, the mass ratio of the inorganic mineral clay powder to the molybdenum carbide powder is (0.5-3) to 1.

When materials are mixed, the mass ratio of the mixture of inorganic mineral clay powder and molybdenum carbide powder to sodium alginate, polyethylene glycol, methylcellulose and deionized water is as follows: 20 to (0.5 to 3.5) to (0.05 to 0.15) to (0.05 to 1.5) to (12 to 20).

The inorganic mineral clay is one or more of montmorillonite, palygorskite and bentonite, and is sieved by a 200-mesh sieve.

The molybdenum carbide powder is in a nanometer or micrometer scale.

The drying temperature of the pill-shaped particles is 60-80 ℃, and the drying time is 12-24 h.

The inert gas is nitrogen or helium, and the flow rate of the gas flow is 100-250 mL/min.

The roasting temperature is 500-800 ℃, the temperature rising program is 2-10 ℃/min, and the roasting temperature is kept at 500-800 ℃ for 0.5-2 h.

Has the advantages that: the invention has the following advantages:

1. the prepared pill-shaped molybdenum carbide is easy to separate, and the problems that the molybdenum carbide is easy to lose and difficult to separate and recover when applied in some fields are solved.

2. The heat treatment process of the pellet-shaped particles has lower roasting temperature, saves energy and simplifies the process.

3. The prepared pill-shaped molybdenum carbide has high mechanical strength and controllable particle size.

4. The invention has the advantages of easily obtained raw materials, simple process and equipment, convenient operation and easy batch production.

Drawings

FIG. 1 is a process flow diagram of the present invention

FIG. 2 is an X-ray diffraction analysis of a sample of example 1 of the present invention

FIG. 3 is an X-ray diffraction analysis of a sample of example 2 of the present invention

FIG. 4 is an X-ray diffraction analysis of a sample of example 3 of the present invention

Detailed Description

In order to achieve the purpose, the invention adopts inorganic mineral clay and organic sodium alginate, polyethylene glycol and methylcellulose as adhesives, and organic materials as pore-forming agents. Mixing the molybdenum carbide powder with molybdenum carbide powder according to a certain proportion, processing the mixture into pills with required particle size, and roasting the pills under the protection of inert gas to prepare the pills of molybdenum carbide which is easy to separate and recover. The method specifically comprises the following steps:

first step, mixing the materials

Fully mixing inorganic mineral clay powder and molybdenum carbide powder which are ground and sieved by a 200-mesh sieve, and fully mixing the mixture with sodium alginate, polyethylene glycol and methyl cellulose; adding deionized water, and stirring to obtain plastic mixed material;

when materials are mixed, the mass ratio of the inorganic mineral clay powder to the molybdenum carbide powder is (0.5-3) to 1. The weight ratio of the mixture of inorganic mineral clay powder and molybdenum carbide powder, sodium alginate, polyethylene glycol, methyl cellulose and deionized water is as follows: 20 to (0.5 to 3.5) to (0.05 to 0.15) to (0.05 to 1.5) to (12 to 20).

Second, making pills

And granulating the obtained plastic mixed material by a pelleting machine, wherein the obtained particle size can be adjusted according to the requirement.

Thirdly, drying

And drying the obtained pellet-shaped particles in an electrothermal blowing drying oven at the temperature of 60-80 ℃ for 12-24 h.

The fourth step, roasting

Raising the temperature to 500-800 ℃ in a muffle furnace at the speed of 2-10 ℃/min under the protection of nitrogen or helium, and keeping the temperature for 0.5-2 h. The flow rate of the nitrogen or helium gas is 100-250 mL/min.

Fifth step, natural cooling

Finally, the pill-shaped molybdenum carbide which is easy to separate and recover is prepared.

The inorganic mineral clay used in the invention is one or a mixture of more of montmorillonite, palygorskite and bentonite. Drying one or more of montmorillonite, palygorskite and bentonite at 105 deg.C, grinding into powder, sieving with 200 mesh sieve, and sealing.

The molybdenum carbide is powder prepared by a high-temperature carbon thermal reduction method, a temperature programmed pyrolysis method, a chemical vapor deposition method, a liquid phase reaction method and the like.

Example 1:

mixing materials: the montmorillonite powder and the molybdenum carbide powder are fully mixed according to the mass ratio of 3: 1, and then the mixture is fully mixed and stirred with sodium alginate, polyethylene glycol, methyl cellulose and deionized water according to the mass ratio of 20: 3: 0.09: 1: 18 to form a plastic material.

Pelleting: the obtained plastic mixed material is granulated by a pelleting machine, and the obtained particle size is 1 mm.

Drying: the obtained pellet-shaped granules were dried in an electric hot air drying oven at 80 ℃ for 12 hours.

Roasting: the temperature was raised to 750 ℃ in a muffle furnace at a rate of 2 ℃/min under nitrogen and held for 2 h. The nitrogen flow rate was 100 mL/min.

Finally, naturally cooling to room temperature to prepare the pill-shaped molybdenum carbide which is easy to separate and recover.

Fig. 2 is an X-ray diffraction (XRD) analysis of the sample, showing that the diffraction peaks at 34.5 °, 37.4 °, 39.5 °, 52.1 °, 61.8 °, and 69.5 ° are characteristic peaks of molybdenum carbide, indicating that the prepared pellet retains highly active molybdenum carbide crystals.

Example 2:

mixing materials: the palygorskite powder and the molybdenum carbide powder are fully mixed according to the mass ratio of 2: 1, and then the mixture is fully mixed and stirred with the sodium alginate, the polyethylene glycol, the methyl cellulose and the deionized water according to the mass ratio of 20: 2: 0.1: 1: 13 to form a plastic material.

Pelleting: the obtained plastic mixed material was granulated by a pellet mill to obtain a particle size of 3 mm.

Drying: the obtained pellet-shaped granules were dried in an electric hot air drying oven at 60 ℃ for 24 hours.

Roasting: the temperature was raised to 600 ℃ in a muffle furnace at a rate of 5 ℃/min under nitrogen and held for 2 h. The nitrogen flow rate was 100 mL/min.

Fig. 3 is an X-ray diffraction (XRD) analysis of the sample, showing that the diffraction peaks at 34.5 °, 37.4 °, 39.5 °, 52.1 °, 61.8 °, and 69.5 ° are characteristic peaks of molybdenum carbide, indicating that the prepared pellet retains highly active molybdenum carbide crystals.

Example 3:

mixing materials: the bentonite powder and the molybdenum carbide powder are fully mixed according to the mass ratio of 1: 1, and then the mixture is fully mixed and stirred with the sodium alginate, the polyethylene glycol, the methyl cellulose and the deionized water according to the mass ratio of 20: 2.5: 0.1: 1.5: 15 to form a plastic material.

Roasting: the temperature was raised to 500 ℃ in a muffle furnace at a rate of 5 ℃/min under nitrogen and held for 2 h. The nitrogen flow rate was 150 mL/min.

Fig. 4 is a sample X-ray diffraction (XRD) analysis, showing that the diffraction peaks at 34.5 °, 37.4 °, 39.5 °, 52.1 °, 61.8 °, and 69.5 ° are characteristic peaks of molybdenum carbide, indicating that the prepared pellet retains highly active molybdenum carbide crystals.

Claims

1. A preparation method of pellet-shaped molybdenum carbide easy to separate and recover is characterized by comprising the following steps: the preparation method specifically comprises the following steps:

first step, mixing the materials

Fully mixing inorganic mineral clay powder and molybdenum carbide powder, and fully mixing the mixture with sodium alginate, polyethylene glycol and methyl cellulose; adding deionized water, and stirring to obtain plastic mixed material;

when materials are mixed, the mass ratio of the inorganic mineral clay powder to the molybdenum carbide powder is (0.5-3) to 1, and the mass ratio of the mixture of the inorganic mineral clay powder and the molybdenum carbide powder to the sodium alginate, the polyethylene glycol, the methylcellulose and the deionized water is as follows: 20: 0.5-3.5: 0.05-0.15: 0.05-1.5: 12-20;

second, making pills

Granulating the obtained plastic mixed material by a pelleting machine, wherein the obtained particle size can be adjusted according to the requirement;

thirdly, drying

Drying the obtained pellet-shaped particles in an electrothermal blowing drying oven at the temperature of 60-80 ℃ for 12-24 h;

the fourth step, roasting

Under the protection of nitrogen or helium, heating to 500-800 ℃ in a muffle furnace at the speed of 2-10 ℃/min, and keeping for 0.5-2h, wherein the flow velocity of nitrogen or helium is 100-250 mL/min;

fifth step, natural cooling

Under the protection of nitrogen or helium, the mixture is continuously and naturally cooled to the room temperature, and then the pill-shaped molybdenum carbide which is easy to separate and recover is obtained.

2. The method for preparing the pelletized molybdenum carbide easy to separate and recover according to claim 1, wherein the method comprises the following steps: the inorganic mineral clay powder is one or more of montmorillonite, palygorskite and bentonite, and is prepared by drying at 105 deg.C, grinding into powder, sieving with 200 mesh sieve, and sealing.

3. The method for preparing the pelletized molybdenum carbide easy to separate and recover according to claim 1, wherein the method comprises the following steps: the molybdenum carbide is powder prepared by a high-temperature carbon thermal reduction method, a temperature programmed pyrolysis method, a chemical vapor deposition method, a liquid phase reaction method and the like.