阅读说明：本技术 一种五氯化钨的制备及纯化方法 (Preparation and purification method of tungsten pentachloride ) 是由 马建修 靖宇 杜文东 于 2021-08-27 设计创作，主要内容包括：本发明提出一种五氯化钨的制备及纯化方法,涉及五氯化钨提纯技术领域。上述五氯化钨的制备及纯化方法包括以下步骤：预处理：将钨粉放置在上层,六氯化钨设置在下层；氯化反应：将氯气通入过量的所述钨粉表面反应制得五氯化钨粗品；纯化反应：将所述五氯化钨粗品加热至280-300℃进行升华,再进行凝华制得高纯五氯化钨。上述五氯化钨的制备及纯化方法采用过量钨粉、氯气作为原料,六氯化钨为下层粉体保护层制备五氯化钨,再利用升华炉进行纯化,制备高纯度五氯化钨。(The invention provides a preparation and purification method of tungsten pentachloride, and relates to the technical field of tungsten pentachloride purification. The preparation and purification method of the tungsten pentachloride comprises the following steps: pretreatment: placing tungsten powder on an upper layer, and arranging tungsten hexachloride on a lower layer; chlorination reaction: introducing chlorine gas into the excessive tungsten powder surface to react to prepare a tungsten pentachloride crude product; and (3) purification reaction: heating the tungsten pentachloride crude product to 280-300 ℃ for sublimation, and then performing desublimation to obtain the high-purity tungsten pentachloride. The preparation and purification method of the tungsten pentachloride adopts excessive tungsten powder and chlorine as raw materials, uses tungsten hexachloride as a lower layer powder protective layer to prepare the tungsten pentachloride, and then uses a sublimation furnace to purify the tungsten pentachloride to prepare the high-purity tungsten pentachloride.)

1. A preparation and purification method of tungsten pentachloride is characterized by comprising the following steps:

pretreatment: placing tungsten powder on an upper layer, and arranging tungsten hexachloride on a lower layer;

chlorination reaction: introducing chlorine into the tungsten powder to react to prepare a tungsten pentachloride crude product, wherein the tungsten powder is excessive or the molar ratio of the tungsten powder to the chlorine is stoichiometric;

and (3) purification reaction: heating the tungsten pentachloride crude product to 280-300 ℃ for sublimation, and then performing desublimation to obtain the high-purity tungsten pentachloride.

2. The method for preparing and purifying tungsten pentachloride according to claim 1, wherein the mass ratio of the tungsten powder to the tungsten hexachloride is 5 (1-2).

3. The method for preparing and purifying tungsten pentachloride according to claim 2, wherein the thickness of the tungsten powder on the upper layer is less than or equal to 20mm, and the thickness of the tungsten hexachloride on the lower layer is greater than or equal to 2 mm.

4. The method for preparing and purifying tungsten pentachloride according to claim 1, wherein the amount ratio of the chlorine gas to the tungsten powder is (1.5-2.5) mol: 183.84 g.

5. The method for preparing and purifying tungsten pentachloride according to claim 2, wherein the chlorination reaction has the following process parameters: the residence time of the chlorine is 20-30s, the reaction temperature is 250-320 ℃, and the reaction pressure is normal pressure.

6. The process for the preparation and purification of tungsten pentachloride according to claim 1, wherein the sublimation is carried out in a sublimation furnace.

7. The method for the preparation and purification of tungsten pentachloride according to claim 6, wherein the desublimation is performed under natural cooling conditions.

Technical Field

The invention relates to the technical field of tungsten pentachloride purification, and particularly relates to a preparation and purification method of tungsten pentachloride.

Background

Tungsten pentachloride (CAS: 13470-14-9), monoclinic system and needle-shaped dark green crystal are used as a rare compound with a tungsten-chlorine ratio of 1:5, have unique tungsten valence variation and chlorine atom decomposition characteristics, have the advantages of strong timing positioning controllability as well as the valence variation rule and the released chlorine free radical, and are regarded as potential substances in the high-precision technical fields of future semiconductors, solar energy, catalysis, military industry, national defense and the like. Research shows that tungsten pentachloride is particularly unstable and is easily converted into tungsten tetrachloride, and further is disproportionated into tungsten dichloride and tungsten hexachloride, so that the tungsten pentachloride is often doped with numerous metal impurities, and the basic data of the melting point and the boiling point of the tungsten pentachloride are seriously lost. In addition, tungsten pentachloride is easy to oxidize, reduce and hydrolyze, and reacts with the environment to generate short-life special metal halide, and reports on preparation of high-purity tungsten pentachloride are very few, especially technical reports on large-scale industrialization.

Currently, the methods for preparing tungsten pentachloride include: 1. reducing tungsten hexachloride by a reducing agent; 2. tungsten pentachloride is prepared by tungsten tetrachloride chloride. However, the above method still has the following problems:

1. in the first process, transient reduction easily occurs. Namely, the tungsten hexachloride can not only generate tungsten pentachloride, but also become tungsten tetrachloride and tungsten dichloride. The temperature and pressure need to be strictly controlled, and in particular the residence time is very demanding.

2. In the second process, transition oxidation easily occurs. Namely, tungsten dichloride or tungsten tetrachloride can not only generate tungsten pentachloride, but also generate tungsten hexachloride. In particular, tungsten hexachloride is more stable than tungsten pentachloride, and is easy to generate a transitional oxidation phenomenon.

3. In the purification process, the tungsten pentachloride has a crystal structure between tungsten hexachloride and tungsten tetrachloride and presents beard needle-shaped crystals, and the tungsten pentachloride is not fully sublimated and forms a spider web shape along a pipeline in the sublimation purification process, so that the yield of high-purity tungsten pentachloride is low.

Disclosure of Invention

In order to overcome the defects and shortcomings of the prior art, the invention aims to provide a method for preparing and purifying tungsten pentachloride.

The technical problem to be solved by the invention is realized by adopting the following technical scheme.

The invention provides a method for preparing and purifying tungsten pentachloride, which comprises the following steps:

pretreatment: placing tungsten powder on an upper layer, and arranging tungsten hexachloride on a lower layer;

chlorination reaction: introducing chlorine into the tungsten powder to react to prepare a tungsten pentachloride crude product, wherein the molar ratio of the tungsten powder to the chlorine is in stoichiometric ratio or the tungsten powder is excessive;

and (3) purification reaction: heating the tungsten pentachloride crude product to 280-300 ℃ for sublimation, and then performing desublimation to obtain the high-purity tungsten pentachloride.

Preferably, the mass ratio of the tungsten powder to the tungsten hexachloride is 5 (1-2).

Preferably, the thickness of the tungsten powder of the upper layer is less than or equal to 20mm, and the thickness of the tungsten hexachloride of the lower layer is greater than or equal to 2 mm.

Preferably, the amount ratio of chlorine to tungsten powder is (1.5-2.5) mol: 183.84 g.

Preferably, the process parameters of the chlorination reaction are: the residence time of the chlorine is 20-30s, the reaction temperature is 250-320 ℃, and the reaction pressure is normal pressure.

Preferably, the sublimation is carried out in a sublimation furnace.

Preferably, desublimation is carried out under natural cooling conditions.

The preparation and purification method of tungsten pentachloride of the embodiment of the invention has the beneficial effects that:

the method has the advantages that the excessive tungsten powder and chlorine are used as raw materials, the tungsten hexachloride is used as a lower powder protective layer to prepare the tungsten pentachloride, the excessive oxidation and reduction of the tungsten pentachloride are effectively prevented, the generation of byproducts of tungsten tetrachloride, tungsten dichloride and tungsten hexachloride is effectively reduced, the purity of the prepared tungsten pentachloride is high, meanwhile, the method does not need to finely control various reaction parameters, the result of low purity and the like caused by the uneven traditional temperature is avoided, and the method is suitable for mass production.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

Tungsten pentachloride (CAS: 13470-14-9) is glittery dark green crystal with molecular formula WCl₅Molecular weight 361.2, melting point 243 deg.C, boiling point 275.6 deg.C.

The embodiment of the invention provides a method for preparing and purifying tungsten pentachloride, which comprises the following steps:

pretreatment: placing tungsten powder on an upper layer, and arranging tungsten hexachloride on a lower layer; the tungsten hexachloride is cheap, easy to obtain and easy to store, and is prepared by combining tungsten powder and excessive chlorine. The tungsten hexachloride is used as a lower powder protective layer, so that the tungsten hexachloride generated by excessive oxidation can be effectively avoided. Meanwhile, the tungsten hexachloride can be subjected to a centering reaction with tungsten tetrachloride and tungsten dichloride to generate tungsten pentachloride, so that excessive reduction of the tungsten pentachloride is effectively hindered, and the amount of byproducts of the tungsten tetrachloride and the tungsten dichloride is greatly reduced. Therefore, the tungsten hexachloride can effectively prevent the over-reduction and oxidation of tungsten pentachloride.

Further, in the preferred embodiment of the invention, the mass ratio of the tungsten powder to the tungsten hexachloride is 5 (1-2).

Further, in the preferred embodiment of the present invention, the thickness of the tungsten powder of the upper layer is less than or equal to 20mm, and the thickness of the tungsten hexachloride of the lower layer is greater than or equal to 2 mm.

Chlorination reaction: introducing chlorine into the tungsten powder to react to prepare a tungsten pentachloride crude product, wherein the molar ratio of the tungsten powder to the chlorine is in stoichiometric ratio or the tungsten powder is excessive; in the chlorination reaction process, the tungsten powder is excessive, the chlorine amount is less, and the tungsten hexachloride and the tungsten pentachloride are mainly generated without excessive oxidation. Because of the low amount of chlorine, tungsten tetrachloride and tungsten dichloride are also produced as by-products. Because the tungsten hexachloride on the lower layer can generate oxidation-reduction reaction with the two byproducts to generate tungsten pentachloride, the conversion rate of chlorine is greatly improved, and the utilization rate of metal tungsten is improved. This mode of operation is very convenient, does not require very strict flow control of the raw materials, and has low residence time requirements. The process is stable and convenient for industrialization.

Further, in the preferred embodiment of the present invention, the ratio of the amount of chlorine to the amount of tungsten powder is (1.5-2.5) mol: 183.84 g.

Further, in the preferred embodiment of the present invention, the process parameters of the chlorination reaction are as follows: the residence time of the chlorine is 20-30s, the reaction temperature is 250-320 ℃, and the reaction pressure is normal pressure.

And (3) purification reaction: heating the tungsten pentachloride crude product to 280-300 ℃ for sublimation, and then performing desublimation to obtain the high-purity tungsten pentachloride. The sublimation is carried out within the temperature range of 280 plus 300 ℃, so that the sublimation of the tungsten hexachloride caused by overhigh temperature can be effectively prevented, and the purity of the product is greatly improved.

Further, in a preferred embodiment of the invention, sublimation is carried out in a sublimation furnace.

Further, in the preferred embodiment of the present invention, the desublimation is performed under natural cooling conditions.

The features and properties of the present invention are described in further detail below with reference to examples.

Example 1

This embodiment provides a method for preparing and purifying tungsten pentachloride, which includes the following steps:

pretreatment: 5kg of tungsten powder having a thickness of 15mm was placed on the upper layer, and 1.5kg of tungsten hexachloride having a thickness of 3mm was placed on the lower layer.

Chlorination reaction: and introducing 54.4mol of chlorine gas into the surface of the tungsten powder in the excessive pretreatment step at the temperature of 280 ℃ under normal pressure, and staying for 25 seconds to react to obtain a crude product of the tungsten pentachloride. In this example, the ratio of the chlorine gas to the tungsten powder was 2 mol: 1mol, in other embodiments, the dosage ratio of chlorine to tungsten powder is only less than or equal to 2.5 mol: 1 mol. I.e., excess tungsten powder or reaction of chlorine and tungsten powder in a stoichiometric ratio as a molar ratio is within the scope of this embodiment.

And (3) purification reaction: heating the crude tungsten pentachloride to 290 ℃ in a sublimation furnace for sublimation. Transferring to a collecting bottle, and performing desublimation under a natural cooling condition to obtain the high-purity tungsten pentachloride.

Example 2

This embodiment provides a method for preparing and purifying tungsten pentachloride, which includes the following steps:

pretreatment: 5kg of tungsten powder having a thickness of 20mm was placed on the upper layer, and 1kg of tungsten hexachloride having a thickness of 2mm was placed on the lower layer.

Chlorination reaction: introducing 40.8mol of chlorine gas into the surface of the tungsten powder in the excess pretreatment step at the temperature of 250 ℃ under normal pressure, and staying for 30 seconds to react to obtain a crude product of tungsten pentachloride.

And (3) purification reaction: heating the tungsten pentachloride crude product to 300 ℃ for sublimation in a sublimation furnace under the condition of reverse rotation speed of 50 r/min. Transferring to a collecting bottle, and performing desublimation under a natural cooling condition to obtain the high-purity tungsten pentachloride.

Example 3

This embodiment provides a method for preparing and purifying tungsten pentachloride, which includes the following steps:

pretreatment: 5kg of tungsten powder having a thickness of 10mm was placed on the upper layer, and 2kg of tungsten hexachloride having a thickness of 2mm was placed on the lower layer.

Chlorination reaction: introducing 68.0mol of chlorine gas into the surface of the tungsten powder in the excess pretreatment step at the temperature of 320 ℃ under normal pressure, and staying for 20 seconds to react to obtain a crude product of tungsten pentachloride.

And (3) purification reaction: heating the tungsten pentachloride crude product to 280 ℃ for sublimation in a sublimation furnace under the condition of reverse rotation speed of 100 r/min. Then transferring the tungsten chloride to a collecting bottle for water cooling at the temperature of 100-150 ℃ for desublimation to obtain the high-purity tungsten pentachloride.

Test example 1

This test example is intended to illustrate the method of evaluating the purity of tungsten pentachloride. The purity of the crude tungsten pentachloride and the high purity tungsten pentachloride prepared in examples 1-3 were analyzed by X-ray fluorescence spectroscopy. Quantitative and qualitative analyses were carried out using an X-ray diffraction analyzer XRD (equipment model: Bruker D8 advanced diffraction instrument), respectively.

The X-ray fluorescence spectrum XRF was used for quantitative analysis using a PFX-Rh 60Kv LiF220 Ge111 AX03 fluorometer. The range of the collimation mask in the X-ray fluorescence analysis is 20-40 mm, the observation diameter is 10-40 mm, the observation mass is 1000-20000 mg, and the sample thickness is 2-10 mm.

XRD was performed using an X-ray diffraction analyzer model Bruker D8 ADVANCE Diffractometer for qualitative analysis of the product. The mode in the X-ray diffraction analysis selects a continuous scanning mode, full spectrum scanning is carried out, scanning is started from 5 degrees to be stopped from 90 degrees, and the step length range is 0.02-0.10 degrees per second.

The results of test example 1 are shown in Table 1 below. Examples 2-3 differ from example 1 in part of the process parameters, and for the sake of clarity of illustration, the data of examples 2-3, which differ from example 1, are also shown in table 1.

TABLE 1 Process parameters for examples 1-3 and purity of the high purity tungsten pentachloride prepared

	Example 1	Example 2	Example 3
				Thickness/mm of tungsten powder	15	20	10
Mass/kg of tungsten hexachloride	1.5	1	2
				Thickness/mm of tungsten hexachloride	3	4	2
Temperature of chlorination reaction/. degree.C	280	250	320
				Amount of chlorine gas used per mol	54.4	40.8	68.0
Hydrogen residence time/s	25	30	20
				Sublimation temperature/. degree.C	290	300	280
Desublimation conditions	Natural cooling	Natural cooling	100 ℃ and 150 ℃ water cooling
				Purity/% of crude tungsten pentachloride	99.9	99.7	99.6
Purity/% of high purity tungsten pentachloride	99.9994	99.9990	99.9991

As can be seen from the numerical values in Table 1, the purity of the tungsten pentachloride crude products prepared in all the examples is above 99.5%, and the purity of the high-purity tungsten pentachloride is above 99.999%, which indicates that the tungsten pentachloride prepared by the method of the present invention has high purity and stable purity.

In conclusion, the invention provides a method for preparing and purifying tungsten pentachloride, which adopts excessive tungsten powder and chlorine as raw materials, and tungsten hexachloride as a lower layer powder protective layer to prepare tungsten pentachloride, thereby effectively preventing over-oxidation and reduction of tungsten pentachloride, effectively reducing the generation of byproducts of tungsten tetrachloride, tungsten dichloride and tungsten hexachloride, and ensuring that the prepared tungsten pentachloride has high purity. The invention also adopts the inner and outer ring tube type sublimers and rotates reversely, thereby avoiding the occurrence of low yield of high-purity tungsten pentachloride caused by spider web-shaped connection in the pipeline due to the precipitation of needle-shaped crystals of tungsten pentachloride.

The embodiments described above are some, but not all embodiments of the invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.