A method for preparing rare earth sulfides and pigments

Abstract

This invention discloses a method for preparing rare earth sulfides and colorants. The method uses rare earth oxides, molybdenum sulfide, and elemental silicon as raw materials. First, molybdenum sulfide and elemental silicon undergo a high-temperature reaction to generate silicon sulfide gas. Then, the silicon sulfide gas undergoes a reducing sulfidation reaction of the rare earth oxides to generate the corresponding rare earth sulfides. Finally, the reaction product is leached with alkali to remove soluble impurities, followed by filtration, rinsing, and drying to obtain high-purity rare earth sulfides. This process yields rare earth sulfide powder and ultrafine molybdenum silicide powder as a byproduct. Furthermore, the phase and color of the rare earth sulfides can be controlled by doping with alkali metals and alkaline earth metals. This invention is a novel method for synthesizing rare earth sulfide powder. Compared to other methods, it has the following advantages: universal applicability, low raw material cost, safe and controllable reaction process, high purity of reaction products with no solid waste generation, and ease of industrial-scale production.

Description

Technical Field

[0001] This invention belongs to the field of inorganic non-metallic materials, and in particular relates to a method for preparing rare earth sulfides and colorants using rare earth oxides, molybdenum sulfide and silicon as raw materials. Background Technology

[0002] Rare earth sulfides are an important class of functional materials with rich optical, electrical, and magnetic properties, and are widely used in many fields such as inorganic pigments, thermoelectric materials, and optical materials. The diversity of their composition and structure, as well as the unique properties of their 4f electrons, endow rare earth sulfides with a series of excellent properties, such as rich and bright colors and good coloring performance, good semiconductor properties, excellent optical and magnetic properties, and good heat resistance. These properties make rare earth sulfides promising for applications in many fields.

[0003] Most rare earth pigments on the market are composed of rare earth sulfides because their colors are generally deeper than those of rare earth oxides. Furthermore, the color change of inorganic compounds is related to the polarization of their contained ions. The energy levels of the polarized electrons change accordingly, reducing the energy difference between the excited and ground states, thus allowing them to absorb light and become colored substances. This is why rare earth sulfides can be used as pigments. The main colors of rare earth sulfides are: La₂S₃ (yellow), Ce₂S₃ (red), Pr₂S₃ (yellow-green), Nd₂S₃ (bright green), Gd₂S₃ (purple), Tb₂S₃ (bright yellow), and Dy₂S₃ (orange).

[0004] The preparation of rare earth sulfides is a key technical issue in rare earth sulfide research. Rare earth elements are highly oxidizing, with a relatively low affinity for sulfur, making the preparation of their sulfides difficult. Industrial preparation methods typically use gaseous sulfiding agents (carbon disulfide and hydrogen sulfide) to sulfide rare earth oxides. This method has drawbacks: the reaction is a gas-solid two-phase reaction, requiring high temperatures and handling small volumes, resulting in high costs and low production efficiency. Furthermore, the storage and transportation of gaseous sulfiding agents are more difficult and dangerous, and hydrogen sulfide or carbon disulfide also have significant environmental impacts. Therefore, the need for safe and controllable sulfiding agents for the preparation of rare earth sulfides is of great importance.

[0005] Meanwhile, rare earth sulfides are defective Th3P4 structures with numerous randomly distributed vacancies. Therefore, other ions can be introduced into the crystal lattice for doping, and these dopant ions can stabilize the phase, significantly reducing the preparation temperature of the sulfides. Introducing alkali metal and alkaline earth metal ions into the crystal lattice for doping enables the low-temperature synthesis of rare earth sulfides. Furthermore, appropriate doping amounts can adjust the electronic structure of rare earth sulfides, specifically changing the band gap width Eg between the valence and conduction bands, thereby altering the wavelength and reflectivity of reflected light. This allows for the adjustment of the hue of rare earth sulfides and the improvement of colorant performance. Summary of the Invention

[0006] In view of the above reasons, and in order to overcome the problems existing in the prior art, the present invention provides a method for preparing rare earth sulfides and a colorant, which is used to solve the above-mentioned problems existing in the prior art.

[0007] The technical solution of this invention is: a method for preparing rare earth sulfides, the specific preparation steps of which are as follows:

[0008] S1) Silicon and molybdenum sulfide are mixed and pressed into blocks according to the chemical reaction stoichiometric ratio;

[0009] S2) Under the protection of an inert atmosphere, the mixed briquettes obtained in S1) are calcined to obtain molybdenum silicide and gaseous silicon sulfide;

[0010] S3) The gaseous silicon sulfide obtained in S2) is used as a sulfur source to perform high-temperature reduction sulfidation on a mixture containing rare earth oxides to obtain the product;

[0011] S4) The product obtained in S3) is subjected to alkali leaching, filtration, rinsing and drying to obtain rare earth sulfide powder.

[0012] Furthermore, the molar ratio of silicon to molybdenum sulfide in S1) is 1:3.5 to 1:4.

[0013] Furthermore, in step S2), the inert atmosphere is argon, the calcination temperature is 900–1600°C, and the holding time is 1–10 hours.

[0014] Furthermore, the mixture containing rare earth oxides in S3) includes: dopant elements and rare earth oxides, wherein the molar ratio of the dopant elements is 0 to 0.3.

[0015] Furthermore, the molar ratio of gaseous silicon sulfide to rare earth oxide in S3) is 1:1 to 3:1;

[0016] The specific process of the high-temperature reduction vulcanization is as follows: the reaction temperature is 900-1600℃, and the holding time is 1-10 hours.

[0017] Furthermore, the doping element is an alkali metal or an alkaline earth metal, and the doping element is added in the form of an oxide, hydroxide, or carbonate.

[0018] Furthermore, the alkali metal is any one of Li, Na, K, Rb, and Cs; and the alkaline earth metal is any one of Mg, Ca, Sr, and Ba.

[0019] Furthermore, the rare earth element in the rare earth oxide is any one of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Y, Ho, Er, Tm, Yb, Lu, and Sc.

[0020] Furthermore, the leaching solution used in the alkaline leaching in S4) includes, but is not limited to, sodium hydroxide and potassium hydroxide.

[0021] A colorant, said colorant is made from rare earth sulfides prepared by the above-described preparation method.

[0022] Compared with existing known technologies, the technical solution provided by this invention has the following beneficial effects:

[0023] (1) This invention uses rare earth oxides, molybdenum sulfide and silicon as raw materials. The solid sulfur source reaction process is safer. The raw materials are all general metallurgical and chemical products and the raw material cost is low.

[0024] (2) The present invention can select raw materials according to different types of target products, and can obtain a series of rare earth sulfides. The method is universal.

[0025] (3) The present invention can design and control the physical and chemical properties of the product, such as color, by means of doping ions, which is flexible and convenient.

[0026] (4) The byproduct of this invention is high-value ultrafine molybdenum silicide powder, and no other solid waste is generated, which meets the environmental protection requirements. Attached Figure Description

[0027] Figure 1 This is a flowchart of a method for preparing rare earth sulfides according to the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0029] like Figure 1 As shown, this invention provides a method for preparing rare earth sulfides, and the specific preparation steps of this method are as follows:

[0030] S1) Silicon and molybdenum sulfide are mixed and pressed into briquettes according to the chemical reaction stoichiometric ratio; wherein both silicon and molybdenum sulfide are solids and their molar ratio is 1:3.5 to 1:4.

[0031] S2) Under the protection of an inert atmosphere of argon, the mixed briquettes obtained in S1) are calcined at a temperature of 900–1600℃ for 1–10 hours to complete the transformation from solid to gaseous state, yielding molybdenum silicide and gaseous silicon sulfide; the intermediate product molybdenum silicide can be obtained here.

[0032] S3) The gaseous silicon sulfide obtained in S2) is used as a sulfur source to perform high-temperature reduction sulfidation on a mixture containing rare earth oxides to obtain the product;

[0033] S4) The product obtained in S3) is subjected to alkali leaching, filtration, rinsing and drying to obtain rare earth sulfide powder.

[0034] The mixture containing rare earth oxides includes: dopant elements and rare earth oxides, wherein the molar ratio of the dopant elements is 0 to 0.3.

[0035] The molar ratio of gaseous silicon sulfide to rare earth oxides is 1:1 to 3:1;

[0036] The reaction temperature is 900–1600℃, and the temperature is maintained for 1–10 hours.

[0037] The doping elements are alkali metals and alkaline earth metals, and are added as oxides, hydroxides or carbonates.

[0038] The alkali metal is any one of Li, Na, K, Rb, and Cs; the alkaline earth metal is any one of Mg, Ca, Sr, and Ba.

[0039] The rare earth elements in the rare earth oxides are any one of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Y, Ho, Er, Tm, Yb, Lu, and Sc.

[0040] The leaching solution used in the alkaline leaching process includes, but is not limited to, sodium hydroxide and potassium hydroxide.

[0041] A colorant, said colorant is made from rare earth sulfides prepared by the above-described preparation method.

[0042] Example 1:

[0043] (1) Weigh molybdenum sulfide and silicon at a molar ratio of 1:4, mix them evenly, and then press them into blocks.

[0044] (2) Under an argon protective atmosphere, the mixture obtained in (1) was placed in a crucible and heat-treated at 1000°C to obtain molybdenum silicide and gaseous silicon sulfide.

[0045] (3) React the gaseous silicon sulfide obtained by calcination in (2) with lanthanum oxide powder at 1000℃ for 4 hours;

[0046] (4) After the heat preservation is completed, the reaction product is cooled to room temperature in an argon atmosphere. The reaction product is then subjected to alkaline leaching, filtration, rinsing and drying to obtain lanthanum sulfide.

[0047] Example 2:

[0048] (1) Weigh molybdenum sulfide and silicon at a molar ratio of 1:3.5, mix them evenly, and then press them into blocks.

[0049] (2) Under an argon protective atmosphere, the mixture obtained in (1) was placed in a crucible and heat-treated at 1200°C to obtain molybdenum silicide and gaseous silicon sulfide.

[0050] (3) React the gaseous silicon sulfide obtained by calcination in (2) with cerium oxide powder at 1200℃ for 4 hours;

[0051] (4) After the heat preservation is completed, the reaction product is cooled to room temperature in an argon atmosphere. The reaction product is then leached with alkali, filtered, rinsed and dried to obtain cerium sulfide.

[0052] Example 3:

[0053] (1) Weigh molybdenum sulfide and silicon at a molar ratio of 1:4, mix them evenly, and then press them into blocks.

[0054] (2) Under an argon protective atmosphere, the mixture obtained in (1) was placed in a crucible and heat-treated at 1000°C to obtain molybdenum silicide and gaseous silicon sulfide.

[0055] (3) Mix sodium carbonate and cerium oxide powder evenly, and react the gaseous silicon sulfide obtained by calcination in (2) with the mixed powder at 1000℃ for 4 hours using argon.

[0056] (4) After the heat preservation is completed, the reaction product is cooled to room temperature in an argon atmosphere. The reaction product is then subjected to alkaline leaching, filtration, rinsing and drying to obtain sodium ion-doped cerium sulfide.

[0057] The foregoing has provided a detailed description of a method for preparing rare earth sulfides and pigments according to embodiments of this application. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and its core ideas; furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

[0058] Certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that hardware manufacturers may use different names to refer to the same component. This specification and claims do not distinguish components based on differences in name, but rather on differences in function. The terms "comprising" and "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising / including but not limited to". "Approximately" means that within an acceptable margin of error, those skilled in the art can solve the technical problem and substantially achieve the technical effect within a certain margin of error. The following descriptions in the specification are preferred embodiments for carrying out this application; however, these descriptions are for the purpose of illustrating the general principles of this application and are not intended to limit the scope of this application. The scope of protection of this application shall be determined by the appended claims.

[0059] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a product or system comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a product or system. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the product or system that includes said element.

[0060] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0061] The foregoing description illustrates and describes several preferred embodiments of this application. However, as previously stated, it should be understood that this application is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the application concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of this application should be within the protection scope of the appended claims.

Claims

1. A method for producing a rare earth sulfide, characterized by, The specific preparation steps are as follows: S1) mixing and briquetting silicon and molybdenum sulfide according to the stoichiometric ratio of chemical reaction; S2) calcining the mixed briquetting obtained in S1) under the protection of inert atmosphere to obtain molybdenum silicide and gaseous silicon sulfide; S3) high-temperature reduction sulfuration of the gaseous silicon sulfide obtained in S2) as a sulfur source to a mixture containing rare earth oxide to obtain a product; S4) obtaining a rare earth sulfide powder by alkali leaching, filtering, rinsing and drying the product obtained in S3).

2. The method of claim 1, wherein, The molar ratio of silicon and molybdenum sulfide in S1) is 1:3.5-1:

4.

3. The method of claim 1, wherein, The inert atmosphere in S2) is argon, and the calcination temperature is 900-1600℃, and the holding time is 1-10 hours.

4. The method of claim 1, wherein, The mixture containing rare earth oxide in S3) includes doped elements and rare earth oxides, wherein the molar ratio of doped elements is 0-0.

3.

5. The method of claim 4, wherein, The molar ratio of gaseous silicon sulfide to rare earth oxide in S3) is 1:1-3:

1. The process parameters of high-temperature reduction sulfuration are as follows: the reaction temperature is 900-1600℃, and the holding time is 1-10 hours.

6. The method of claim 4, wherein, The doped elements are alkali metals and alkaline earth metals, and the doped elements are added in the form of oxides, hydroxides or carbonates.

7. The method of claim 6, wherein, The alkali metal is any one of Li, Na, K, Rb, Cs; the alkaline earth metal is any one of Mg, Ca, Sr, Ba.

8. The method of claim 4, wherein, The rare earth element in the rare earth oxide is any one of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Y, Ho, Er, Tm, Yb, Lu, Sc.

9. The method of claim 1, wherein, The leaching solution used in S4) is sodium hydroxide or potassium hydroxide.

10. A colorant characterized by, The colorant is made of the rare earth sulfide prepared by the preparation method of any one of claims 1-9.

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