CN113086985A

CN113086985A - Low-cost preparation method of molybdenum silicide without emission of sulfur-containing gas

Info

Publication number: CN113086985A
Application number: CN202110321383.2A
Authority: CN
Inventors: 张国华; 常贺强
Original assignee: University of Science and Technology Beijing USTB
Current assignee: University of Science and Technology Beijing USTB
Priority date: 2021-03-25
Filing date: 2021-03-25
Publication date: 2021-07-09
Anticipated expiration: 2041-03-25
Also published as: CN113086985B

Abstract

The invention discloses a method for preparing molybdenum silicide at low cost without sulfur-containing gas emission, which is directly used for MoS₂The molybdenum silicide is prepared by the next step under the condition of high-temperature inert atmosphere by using the substances with main components, such as molybdenum concentrate, as a molybdenum source, substances with Si as a main component as a reducing agent and lime as a sulfur-fixing agent. During the reaction, MoS₂S in the desulfurization solution is captured by desulfurizer lime and exists in an external desulfurization layer in the form of CaS, and the desulfurization layer and internal molybdenum silicide (MoSi) can be separated by simple stripping operation₂、Mo₅Si₃Or Mo₃Si). The method can directly use the molybdenum concentrate as the molybdenum source, thereby avoiding the roasting process of the molybdenum concentrate and greatly shortening the production flow of the molybdenum source; the invention uses lime as a desulfurizer, can avoid sulfur element in molybdenum concentrate from being discharged into the atmosphere in the form of sulfur-containing gas when the molybdenum concentrate is used as a molybdenum source, and can simply crush and separate a desulfurization layer and an inner layer product after the reaction is finished, thereby being suitable for large-scale industrial production.

Description

Low-cost preparation method of molybdenum silicide without emission of sulfur-containing gas

Technical Field

The invention belongs to the field of material preparation, and discloses a method for preparing a molybdenum silicide material.

Background

Si and Mo can generate Mo under different conditions₃Si、Mo₅Si₃And MoSi₂Three intermetallic compounds, currently only MoSi₂Has wide application. MoSi₂Has oxidation resistance under high temperature condition, and is mainly used as heating element and high temperature structural material of industrial furnace. Compared with MoSi₂，Mo₅Si₃And Mo₃Si has a higher melting point and better high temperature creep resistance, but has poor high temperature oxidation resistance. Further, Mo₃Si has the highest Mo content (about 91%) of the three compounds₅Si₃The content of Mo in the molybdenum-containing steel is 79.7 percent, and the molybdenum content of the molybdenum-containing steel and the molybdenum-containing steel is higher than that of ferromolybdenum serving as a conventional molybdenum additive, so that the molybdenum-containing steel and the molybdenum-containing steel are hopeful to be used as the molybdenum additive for smelting molybdenum-containing steel. Further, Mo₃Si、Mo₅Si₃And MoSi₂Is used as a titanium alloy surface coating material to enhance the corrosion resistance of the titanium alloy surface coating material.

Since the discovery of molybdenum silicide in 1906, a number of processes including powder metallurgy reduction, self-propagating high temperature synthesis, mechanical alloying, low vacuum plasma deposition and spraying, solid state transfer reaction, and thermal dispersion have been used to prepare molybdenum silicide. The molybdenum source used in the above method comprises high purity MoO₃Molybdenum powder and molybdenum carbide, wherein the three raw materials are prepared by a series of steps of roasting molybdenum concentrate by molybdenum oxide, leaching ammonia water, pyrolyzing ammonium molybdate and the like, and overlong production flow causes high raw material cost, and in addition, a large amount of unrecoverable low-concentration SO can be generated in the roasting link of the molybdenum concentrate₂A gas. In order to avoid the use of the above three raw materials as molybdenum source in the molybdenum silicide production process, there are patents and articles that propose the direct use of MoS₂Preparation of MoSi using Si powder as a reducing agent as a molybdenum source₂However, the product prepared has MoSi in addition₂Also SiS and SiS₂A gas. SiS and SiS₂The gas is difficult to collect, and after being discharged into the air, the gas can generate H through hydrolysis reaction₂S gas causes environmental pollution, so that the S gas is difficult to be applied to the industrial preparation of MoSi₂。

Disclosure of Invention

The invention aims to solve the problems of Mo and MoO used in the current molybdenum silicide production process₃Or Mo₂C, the emission problem of low-concentration sulfur-containing gas caused by the preparation of C, and provides a method for preparing molybdenum silicide, which has the advantages of wide raw materials, no emission of sulfur-containing gas, simple process and suitability for large-scale process production.

In order to achieve the purpose, the invention adopts the following technical scheme:

using molybdenum concentrates or in MoS₂A substance containing Si as a main component as a molybdenum source, a substance containing Si as a main component as a reducing agent, and lime as a desulfurizing agent. Uniformly mixing a molybdenum source and a reducing agent according to a certain proportion, pressing and forming to obtain an inner layer sample, then covering a layer of reducing agent with a certain amount outside the inner layer sample, and reacting for a certain time under an inert atmosphere with a reaction temperature range of 1100-1600 ℃. And when the sample is cooled to room temperature, stripping the external desulfurization layer to obtain the target product molybdenum silicide.

The invention provides a method for preparing molybdenum silicide at low cost without sulfur-containing gas emission, which specifically comprises the following steps:

and uniformly mixing a molybdenum source and a reducing agent according to a certain proportion, pressing and forming to obtain an inner layer sample, covering a certain amount of desulfurizer on the surface of the inner layer sample, reacting for a period of time under the condition of high-temperature inert atmosphere, and stripping an outer desulfurization layer after the sample is reacted and cooled to room temperature to obtain the molybdenum silicide.

The mixture ratio of the molybdenum source and the reducing agent is MoS in the molybdenum source₂Is in a molar ratio to the actual content of Si in the reducing agent of 1: 2.33-1: 4; the amount of the desulfurizer is MoS in a molybdenum source₂Theoretical amount (MoS) required when all sulfur elements in the sulfur are fixed in the form of CaS₂The mol ratio of CaO to CaO is 1: 2) 1-4 times of the total weight of the composition; the temperature range of the high-temperature reaction is 1100-1600 ℃; the reaction time is 0.5-10 h.

The molybdenum source is MoS₂Materials that are the major component, including but not limited to molybdenite, molybdenum concentrate, or molybdenum disulfide reagent; the reducing agent is a substance containing Si as a main component, such as Si powder.

The stripping of the outer desulfurization layer comprises two steps of crushing and separating the desulfurization layer.

The desulfurization reaction equation of the desulfurizing agent at high temperature is as follows:

2CaO+2SiS＝2CaS+Si+SiO₂ (1)

2CaO+SiS₂＝2CaS+SiO₂ (2)

the prepared molybdenum silicide comprises MoSi₂、Mo₅Si₃Or Mo₃Si。

Direct use of the invention with MoS₂Substances that are the main component, such as molybdenum concentrate, are the molybdenum source,the molybdenum silicide is prepared by the next step under the condition of high-temperature inert atmosphere by taking a substance taking Si as a main component as a reducing agent and lime as a sulfur-fixing agent. During the reaction, MoS₂The S in the molybdenum silicide is reduced by silicon to generate silicon sulfide gas which is captured by lime serving as a desulfurizing agent and exists in an external desulfurization layer in the form of CaS, and the desulfurization layer and the internal molybdenum silicide can be separated by simple stripping operation.

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

1. the method can directly use the molybdenum concentrate as a molybdenum source, avoids the roasting process of the molybdenum concentrate, greatly shortens the production flow of the molybdenum source, and has extremely short production flow compared with the traditional process of preparing molybdenum trioxide, molybdenum powder or molybdenum carbide by a series of steps of molybdenum concentrate oxidizing roasting, ammonia leaching, ammonium molybdate roasting and the like and then using the molybdenum trioxide, molybdenum powder or molybdenum carbide for preparing molybdenum silicide;

2. the method can synthesize Mo by controlling the ratio of Mo and Si in the raw materials and the reaction temperature₃Si、Mo₅Si₃And MoSi₂Three intermetallic compounds;

3. the invention only uses lime as a desulfurizer, and can avoid sulfur-containing gas (SiS and SiS) as sulfur element in molybdenum concentrate when the molybdenum concentrate is used as a molybdenum source₂) The sulfur-containing gas is discharged into the atmosphere, no sulfur-containing gas is discharged, the desulfurization layer and the inner layer product can be simply crushed and separated after the reaction is finished, and the process is free from pollution and suitable for large-scale industrial production.

Detailed Description

For a further understanding of the present invention. The present invention will be further described with reference to examples.

The first embodiment is as follows:

molybdenum concentrate (MoS)₂95%) and Si powder according to the actual MoS₂The mol ratio of the content to Si is 1: 2.33 batching, mixing homogeneously and compression moulding as an inner layer sample, then covering (covering the inner layer sample with desulphurizer lime) a layer of desulphurizer outside the inner layer sample, the amount of desulphurizer lime corresponding to MoS in the molybdenum concentrate₂The mol ratio of the lime to CaO content in the lime is 1: 4, and reacting for 0.5 hour at 1100 ℃ in an inert atmosphereThen (c) is performed. Cooling to room temperature, stripping the outer desulfurizer layer to obtain Mo₃And (3) Si. XRD analysis is carried out on samples at different positions of the stripped outer layer substance, and the result shows that the main phase of the position contacted with the inner layer sample is CaS, which shows that the lime in the invention can fix the sulfur element in the molybdenum concentrate in the form of CaS; in addition, the outermost surface phase of the outer sample had only CaO, so the sulfur element of the molybdenum concentrate was all captured in CaS form by CaO in the outer desulfurization agent layer.

Example two:

molybdenum disulfide and high-purity Si powder are mixed according to actual MoS₂The molar ratio of the content to C is 1: 4, preparing materials, uniformly mixing, pressing and forming to obtain an inner layer sample, and then coating a layer of desulfurizer on the outer part of the inner layer sample, wherein the amount of the desulfurizer lime is corresponding to MoS in molybdenum disulfide₂The mol ratio of the lime to CaO content in the lime is 1: 3, and reacting for 10 hours at 1200 ℃ in an inert atmosphere. Cooling to room temperature, and stripping the outer desulfurizer layer to obtain pure MoSi₂. In addition, XRD analysis of the outer surface of the outer desulfurization layer revealed that only CaO was detected, indicating that no sulfur-containing gas was emitted during the reaction.

Example three:

molybdenum concentrate (MoS)₂95%) and Si powder according to the actual MoS₂The mol ratio of the content to Si is 1: 2.6 preparing materials, uniformly mixing, pressing and forming to obtain an inner layer sample, and then coating a layer of desulfurizer on the outer part of the inner layer sample, wherein the amount of the desulfurizer lime is corresponding to MoS in the molybdenum concentrate₂The mol ratio of the lime to CaO content in the lime is 1: 4, and reacting for 5 hours at 1300 ℃ in an inert atmosphere. Cooling to room temperature, stripping the outer desulfurizer layer to obtain Mo₅Si₃. In addition, XRD analysis of the outer surface of the outer desulfurization layer revealed that only CaO was detected, indicating that no sulfur-containing gas was emitted during the reaction.

Claims

1. A method for preparing molybdenum silicide with low cost and without sulfur-containing gas emission is characterized in that a molybdenum source and a reducing agent are uniformly mixed according to a certain proportion and are pressed and formed to be used as an inner layer sample, then a certain amount of desulfurizer is covered on the surface of the inner layer sample, the inner layer sample reacts for a period of time under the condition of high-temperature inert atmosphere, and when the sample finishes the reaction and is cooled to room temperature, an outer desulfurization layer is peeled off, so that molybdenum silicide is obtained.

2. The method of claim 1, wherein the molybdenum source and the reducing agent are mixed at a ratio of MoS to MoS in the molybdenum source₂Is in a molar ratio to the actual content of Si in the reducing agent of 1: 2.33-1: 4; the amount of the desulfurizer is MoS in a molybdenum source₂The sulfur element in the sulfur-containing material is 1-4 times of theoretical amount required when all sulfur elements are fixed in the form of CaS, and the theoretical amount is MoS₂Molar ratio to CaO 1: 2; the temperature range of the high-temperature reaction is 1100-1600 ℃; the reaction time is 0.5-10 h.

3. The method for preparing molybdenum silicide at low cost without sulfur-containing gas emission according to claim 1, wherein the molybdenum source is MoS₂Substances as the main component, including molybdenite, molybdenum concentrate or molybdenum disulfide reagent; the reducing agent is a substance containing Si as a main component.

4. The method for preparing molybdenum silicide at low cost without sulfur-containing gas emission as claimed in claim 1, wherein the stripping of the outer desulfurization layer comprises two steps of crushing and separating the desulfurization layer.

5. The method for preparing molybdenum silicide at low cost without sulfur-containing gas emission as claimed in claim 1 or 3, wherein the desulfurization reaction equation of the desulfurizing agent at high temperature is as follows:

2CaO+2SiS＝2CaS+Si+SiO₂ (1)

2CaO+SiS₂＝2CaS+SiO₂ (2)。

6. the method for preparing molybdenum silicide at low cost without sulfur-containing gas emission as claimed in claim 1, wherein the molybdenum silicide is prepared by a method comprisingThen, the obtained molybdenum silicide is MoSi₂、Mo₅Si₃Or Mo₃Si。