CN108298586B - Preparation method of tungsten pentachloride - Google Patents
Preparation method of tungsten pentachloride Download PDFInfo
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- CN108298586B CN108298586B CN201810269194.3A CN201810269194A CN108298586B CN 108298586 B CN108298586 B CN 108298586B CN 201810269194 A CN201810269194 A CN 201810269194A CN 108298586 B CN108298586 B CN 108298586B
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Abstract
The invention discloses a preparation method of tungsten pentachloride, which comprises the following steps: grinding raw material tungsten hexachloride, transferring the ground raw material tungsten hexachloride into a reactor, introducing high-purity hydrogen to realize reduction reaction on the tungsten hexachloride, wherein the reaction temperature is 280-400 ℃, the reaction pressure is 0.01-0.5MPa, the reaction residence time is 2 seconds-5 minutes, and a tungsten pentachloride crude product with the concentration of more than 95% is obtained, and the conversion rate of the tungsten hexachloride is more than 80%; the method has the advantages that the method accurately regulates the reduction reaction process, improves the stability and the purification rate of the tungsten pentachloride product, is simple and easy to implement, has strong controllability and low cost, and is easy for large-scale industrial production.
Description
Technical Field
The invention relates to synthesis and purification of metal halide, in particular to a preparation 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.
Tungsten pentachloride was first described in the literature manuscript in the sixties of the last century (acta. cryst.1978.b34,2833-2834) and is a by-product obtained by scientists when studying the synthesis of tungsten chloride in other valence states (e.g., tungsten hexachloride, tungsten tetrachloride, dichloride, etc.). Limited by the development of science and technology, no report on the production of high-purity tungsten pentachloride exists, the tungsten pentachloride is often doped with a plurality of metal impurities, basic data of melting points and boiling points of the tungsten pentachloride are seriously lost, the tungsten pentachloride is sporadically recorded in various tungsten metal chemical dictionaries (acta. Cryst.1974.B30,1216, J mol. Cat., 199165, 261 and 267), the data fluctuation range is very wide, for example, the melting point is 220-290 ℃, the boiling point is 270-290 ℃, and only empirical reference is available.
While the industrial production route of large-scale tungsten pentachloride has not been systematically studied, the clue that can be found at present is the record of the synthetic method for studying the properties of tungsten metal chlorides on a laboratory scale (several grams at a time) (inorganic syntheses, 1957, e.l. mccann, t.m. browse).
The synthesis route of the tungsten pentachloride mainly comprises two types, wherein the first type is prepared by reducing tungsten hexachloride by red phosphorus at the temperature of 250-280 ℃ or by reducing tungsten hexachloride by hydrogen at the temperature of 380-400 ℃, and the chemical formula is as follows:
the preparation method 1: 3WCl6+P→3WCl5+PCl3；
2WCl6+H2→2WCl5+2HCl，
The method requires heating tungsten hexachloride at 410-425 ℃ in a quartz tube while introducing hydrogen for reduction. Due to the simultaneous formation of tungstic oxychloro compounds and low-valent WCl4、WCl3、WCl2And the product is purified by sublimation in a nitrogen stream and stored in a closed tube. More complicated, the chemical dictionary describes the nature of tungsten chloride, which can be disproportionated to tungsten pentachloride and dichloride. Therefore, the method does not have strict scientific demonstration, the given description is very different, the reaction conditions are uncertain, and the product and impurities thereof are not very clear.
The second method uses the synthesis method of tungsten tetrachloride as a reference, and adopts a mild and controllable reduction reagent tetrachloroethylene to reduce the raw material tungsten hexachloride. The reaction was carried out in an oil bath for 24 hours and irradiated with a 100W bulb in a vacuum chamber. By changing the irradiation intensity and the oil bath temperature, the initially produced reddish brown solution can be changed into blue-green, namely, tungsten pentachloride is produced, and finally, fine dark powder is produced, wherein the chemical formula is as follows:
the preparation method 2: 2WCl6+C2Cl4→2WCl5+C2Cl6，
This procedure is exactly the same as the procedure for the preparation of tungsten tetrachloride, but the product is not in contact with air because of its very strong hygroscopicity, and should be dried sufficiently and stored. Under the reaction condition, no protective atmosphere exists, so that the tungsten pentachloride is difficult to be guaranteed not to be decomposed. During refining, the product is placed in a hard glass tube in vacuum or in the airflow of nitrogen and carbon dioxide, the glass tube is placed in an electric furnace to form a temperature gradient, so that the most sublimable tungsten pentachloride is firstly separated out, and the tungsten tetrachloride is finally left as black.
Tungsten pentachloride has the chemical formula W2Cl10Formed by tungsten tetrachloride and tungsten hexachloride sharing a chlorine bridge, and the structure of the tungsten tetrachloride and the tungsten hexachloride is MoCl5And NbCl5The crystal structures are similar and twin with each other. The tungsten hexachloride powder is brown crystal, and the tungsten tetrachloride powder is black (in other words, brownish red), but the tungsten pentachloride and the tungsten chloride in other valence states can hardly be distinguished by naked eyes due to the difference of the particle sizes of the powder and the crystal, and the scattering of visible light. The most important academic research (j. chem.soc., Dalton trains., 2001, 1616-.
In conclusion, tungsten pentachloride is a short-life special metal halide which is extremely unstable, easy to oxidize, reduce and hydrolyze and easy to react with the environment, and the preparation, separation and purification technology aspects of the tungsten pentachloride have no reference report.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a preparation method of tungsten pentachloride, which aims to achieve the effects of accurately regulating and controlling the reduction reaction process and improving the stability and the purification rate of the tungsten pentachloride.
The technical purpose of the invention is realized by the following technical scheme:
a preparation method of tungsten pentachloride comprises the following steps:
(1) pretreating a raw material tungsten hexachloride;
(2) preparing in the early stage of reaction;
(3) preparing tungsten pentachloride by reaction;
(4) purifying a tungsten pentachloride product;
(5) the collection of the tungsten pentachloride product is carried out,
wherein, in the step (3): heating a reactor filled with the raw material tungsten hexachloride to 280-400 ℃, introducing high-purity hydrogen, wherein the relation between the flow of the high-purity hydrogen and the mass of the tungsten hexachloride is 100-1000 mL/min: 1kg, the internal pressure range of the reactor is 0.01-0.5MPa, and the residence time of hydrogen in the reactor is 2s-5 min;
in the step (4): the gas with the main product of tungsten pentachloride enters a purifier I from a reactor, the temperature of the purifier I is raised to 280-310 ℃, the tungsten pentachloride and light component impurities are gasified and transferred to a purifier II, the temperature of the purifier II is raised to 230-260 ℃, and the light component impurities are gasified and transferred to a tail gas washing bottle.
Preferably, the temperature of the reactor filled with the raw material tungsten hexachloride in the step (3) is raised to 300-350 ℃.
Preferably, the internal pressure of the reactor in the step (3) is in the range of 0.1 to 0.2 MPa.
Preferably, the residence time of the hydrogen in the reactor in the step (3) is 5s-1 min.
By adopting the scheme, in the aspect of reaction preparation, considering the characteristics that tungsten pentachloride is extremely unstable and is easy to deliquesce and react with air, a hydrogen reduction method is selected, so that the tungsten pentachloride product is very suitable for industrial production in an atmosphere protected by hydrogen, and meanwhile, the method is single in product and convenient for subsequent purification. Through a large number of experiments, the reaction temperature, the feeding proportion and the reaction retention time are accurately controlled, specific parameter ranges are given, tungsten pentachloride is selectively produced, the situations of over reduction or under reduction of tungsten hexachloride are reduced, and WCl is reduced2、WCl3、WCl4Etc. by-product generation.
In terms of purification, although the melting points of tungsten tetrachloride and tungsten dichloride are not determined, it can be concluded that the melting points of tungsten dichloride and tungsten tetrachloride are certainly much lower than that of tungsten pentachloride, based on the relationship that the van der waals force of covalent compounds is mainly proportional to the relative molecular mass. In addition, there may be other metal chloride impurities in the tungsten hexachloride feedstock that also have a significant difference in boiling point from tungsten pentachloride. Therefore, according to the boiling point difference of the tungsten pentachloride and other metal chlorides (refer to table 1), the light component impurities and the heavy component impurities are respectively removed, and the high-purity tungsten pentachloride is obtained.
Table 1 melting point property table of tungsten chloride in different valence states.
| Melting Point (. degree.C.) | Boiling point (. degree.C.) | |
| Tungsten hexachloride | 270-280 | 330-350 |
| Tungsten pentachloride | 220-250 | 270-290 |
| Tungsten tetrachloride | Uncertainty (<200) | Uncertainty (<200) |
| Tungsten dichloride | Uncertainty (<180) | Uncertainty (<180) |
| Zinc chloride | 290 | 732 |
| Sodium chloride | 801 | 1465 |
| Aluminium chloride | 190 | 178 |
| Nickel chloride | 1001 | 987 |
| Ferric chloride | 306 | 315 |
| Magnesium chloride | 714 | 1412 |
Preferably, in step (5): the temperature of the purifier II is raised to 300-305 ℃, and the tungsten pentachloride is gasified and transferred to a collector.
By adopting the scheme, the tungsten pentachloride is gasified by utilizing the boiling point characteristic of the tungsten pentachloride, so that the tungsten pentachloride is conveniently transferred out of the purifier and enters the collector, the boiling point of the tungsten pentachloride is 290 ℃, and the gasification temperature is slightly higher than the boiling point, but the large reason is to prevent impurities with higher boiling points from being mixed.
Preferably, the raw material tungsten hexachloride in the step (1) is ground to a particle size of 20-1000 μm under an inert gas.
Preferably, the raw material tungsten hexachloride in step (1) is ground to a particle size of 100-400 μm under an inert gas.
Preferably, in step (2): after the reactor is dried, introducing inert gas to purge for at least 2 hours, charging the raw material tungsten hexachloride into the reactor, then heating and preheating, wherein the heating rate is 5-20 ℃/min, and when the temperature is raised to 100 ℃, keeping the temperature for at least 2 hours.
Preferably, the inert gas is one of high-purity nitrogen, high-purity helium, high-purity neon and high-purity argon.
By adopting the scheme, the moisture and the air in the reactor are reduced, and the stability of the tungsten pentachloride product is further improved.
Preferably, the reactor, the purifier and the collector are made of high-temperature-resistant, reduction-resistant and corrosion-resistant materials, such as glass, enamel and quartz.
In conclusion, the invention has the following beneficial effects:
1. the extremely unstable tungsten pentachloride avoids the decomposition of environmental water and air, and the reaction product is accurately controlled by controlling the reaction temperature, the hydrogen flow and the reaction residence time, so that the tungsten pentachloride is specifically reduced to the tungsten pentachloride, the generation of tungsten tetrachloride and tungsten dichloride is reduced, the conversion rate of the tungsten hexachloride is greatly improved, the purity of the tungsten pentachloride at a first-stage reaction outlet can reach more than 95 percent, and the difficulty of subsequent separation and purification is reduced;
2. the purification of the high-purity tungsten pentachloride is realized by utilizing the boiling point difference of the tungsten pentachloride, the tungsten chloride with other valence states and the metal chloride impurities. As far as the present, the preparation and purification technology of high-purity tungsten pentachloride is reported for the first time in the international scope, the invention undoubtedly makes an important contribution to the scientific basic research of tungsten pentachloride which is an unknown blank substance;
3. the high-purity tungsten pentachloride prepared by the method can improve the physical and chemical properties of pure substance standards, supplement data loss in a chemical dictionary and promote the wide application of the tungsten pentachloride in high precision fields such as light, electricity, magnetism, catalysis and the like in the future;
4. the method has the advantages of strong operation controllability, low cost and easy amplification, and can be used for producing high-purity tungsten pentachloride powder on a large scale.
Drawings
FIG. 1 is a process flow diagram of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
Example 1
A preparation method of tungsten pentachloride is combined with figure 1, and comprises the following steps:
(1) all the devices such as the reactor, the auxiliary collector, the raw material sampling equipment, the analytical balance, the connecting pipeline, the glass container and the like are dried overnight, high-purity nitrogen is introduced for purging for 2 hours, and the tail gas is detected by chromatography to ensure that no water and air exist;
(2) grinding tungsten hexachloride raw material to particle size of 40 μm in a glove box under nitrogen atmosphere, weighing 1kg of tungsten hexachloride raw material by balance, transferring to a reactor, and continuously introducing nitrogen for protection;
(3) heating the reactor to 280 ℃, heating at the rate of 5-20 ℃/min, keeping the temperature for 2 hours when the temperature is raised to 100 ℃;
(4) introducing high-purity hydrogen, wherein the flow of the high-purity hydrogen is 100mL/min, the internal pressure range of the reactor is 0.01MPa, and the retention time of the high-purity hydrogen in the reactor is 1 min;
(5) the gas with the main product of tungsten pentachloride enters a purifier I from a reactor, the temperature of the purifier I is raised to 280 ℃, the tungsten pentachloride and light component impurities are gasified and transferred to a purifier II, the temperature of the purifier II is raised to 230 ℃, and the light component impurities are gasified and transferred to a tail gas washing bottle; (6) heating the purifier II to 300 deg.c, gasifying tungsten pentachloride and transferring to collector,
wherein, the reactor, the purifier, the collector, the accessory pipeline fittings and the vessel for sampling are all made of high-temperature resistant, reduction resistant and corrosion resistant materials, such as glass, enamel and quartz, wherein, the preferred material is quartz material;
the inert shielding gas may be high purity nitrogen, helium, neon, argon, etc., among which argon is preferred,
the purity of the tungsten pentachloride was analyzed by X-ray fluorescence spectroscopy, and the purity of the crude tungsten pentachloride after the first-order reaction in this example was 99.1%, the purity of the purified high-purity tungsten pentachloride was 99.9991%, and the yield of the tungsten hexachloride was 82.1%.
Examples 2-8 differ from example 1 in part of the process parameters, conversion of starting tungsten hexachloride and purity of product tungsten pentachloride, and for simplicity of illustration, the data for examples 2-8 are tabulated differently from example 1, the data for examples 1-4 are shown in Table 2, and the data for examples 5-8 are shown in Table 3.
Table 2 process parameters, feedstock conversion and product purity for examples 1-4.
| Example 1 | Example 2 | Example 3 | Example 4 | |
| (2) Medium raw material grain diameter/mum | 40 | 100 | 400 | 700 |
| (3) Medium reaction temperature/. degree.C | 280 | 310 | 360 | 400 |
| (4) Flow rate of medium-high purity hydrogen/mL/min | 100 | 300 | 400 | 500 |
| (4) Internal pressure/MPa of intermediate reactor | 0.1 | 0.15 | 0.17 | 0.18 |
| (4) Residence time in/s | 60 | 50 | 47 | 30 |
| (5) Temperature rise/DEG C of the intermediate purifier I | 280 | 290 | 300 | 310 |
| (5) Temperature rise/deg.C of secondary purifier II | 230 | 240 | 250 | 260 |
| (6) Temperature rise/deg.C of secondary purifier II | 300 | 301 | 302 | 304 |
| Yield of tungsten hexachloride/% | 82.1 | 80.7 | 87.5 | 84.7 |
| Purity/% of crude tungsten pentachloride | 99.1 | 98.1 | 99.2 | 98.0 |
| Purity/% of high purity tungsten pentachloride | 99.9991 | 99.9966 | 99.9972 | 99.9924 |
Table 3 process parameters, feedstock conversion and product purity for examples 5-8.
| Example 5 | Example 6 | Example 7 | Example 8 | |
| (2) Medium raw material grain diameter/mum | 1000 | 200 | 300 | 600 |
| (3) Medium reaction temperature/. degree.C | 400 | 330 | 310 | 290 |
| (4) Flow rate of medium-high purity hydrogen/mL/min | 600 | 800 | 900 | 1000 |
| (4) Internal pressure/MPa of intermediate reactor | 0.19 | 0.2 | 0.21 | 0.22 |
| (4) Residence time in/s | 10 | 7 | 6 | 5 |
| (5) Temperature rise/DEG C of the intermediate purifier I | 300 | 290 | 280 | 310 |
| (5) Temperature rise/deg.C of secondary purifier II | 260 | 250 | 240 | 230 |
| (6) Temperature rise/deg.C of secondary purifier II | 303 | 305 | 305 | 304 |
| Yield of tungsten hexachloride/% | 85.7 | 87.1 | 89.2 | 88.8 |
| Purity/% of crude tungsten pentachloride | 99.1 | 99.3 | 98.7 | 98.2 |
| Purity/% of high purity tungsten pentachloride | 99.9874 | 99.9988 | 99.9992 | 99.9994 |
As can be seen from the values in tables 2 and 3, the purity of the crude tungsten pentachloride in all the examples is 98% or more, the purity of the final product, namely the high-purity tungsten pentachloride, is 99.9% or more, and the purity of the high-purity tungsten pentachloride in the examples 1 and 7 is even 99.999% or more, which indicates that the tungsten pentachloride prepared by the method of the present invention has high purity. The method of the invention avoids the decomposition of environmental water and air by the extremely unstable tungsten pentachloride, and precisely controls the reaction product by controlling the reaction temperature, the hydrogen flow and the reaction residence time, so that the tungsten pentachloride is specifically reduced, the generation of tungsten tetrachloride and tungsten dichloride is reduced, the conversion rate of the tungsten hexachloride is greatly improved, the purification temperature is precisely controlled, and the purification of the high-purity tungsten pentachloride is realized. In addition, the method has the advantages of strong operation controllability, low cost and easy amplification, and can be used for producing high-purity tungsten pentachloride powder on a large scale.
The present embodiment is only for explaining the present invention, and it is not limited to the present invention, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present invention.
Claims (11)
1. A preparation method of tungsten pentachloride is characterized by comprising the following steps: the method comprises the following steps:
(1) pretreating a raw material tungsten hexachloride;
(2) preparing in the early stage of reaction;
(3) preparing tungsten pentachloride by reaction;
(4) purifying a tungsten pentachloride product;
(5) the collection of the tungsten pentachloride product is carried out,
wherein, in the step (3): heating a reactor filled with the raw material tungsten hexachloride to 280-400 ℃, introducing high-purity hydrogen, wherein the relation between the flow of the high-purity hydrogen and the mass of the tungsten hexachloride is 100-1000 mL/min: 1kg, the internal pressure range of the reactor is 0.01-0.5MPa, and the residence time of hydrogen in the reactor is 2s-5 min;
in the step (4): the gas with the main product of tungsten pentachloride enters a purifier I from a reactor, the temperature of the purifier I is raised to 280-310 ℃, the tungsten pentachloride and light component impurities are gasified and transferred to a purifier II, the temperature of the purifier II is raised to 230-260 ℃, and the light component impurities are gasified and transferred to a tail gas washing bottle.
2. The process for the preparation of tungsten pentachloride according to claim 1, characterized in that: the temperature of the reactor filled with the raw material tungsten hexachloride in the step (3) is raised to 300-350 ℃.
3. The process for the preparation of tungsten pentachloride according to claim 1, characterized in that: the internal pressure range of the reactor in the step (3) is 0.1-0.2 MPa.
4. The process for the preparation of tungsten pentachloride according to claim 1, characterized in that: in the step (3), the residence time of the hydrogen in the reactor is 5s-1 min.
5. The process for the preparation of tungsten pentachloride according to claim 1, characterized in that: in the step (5): the temperature of the purifier II is raised to 300-305 ℃, and the tungsten pentachloride is gasified and transferred to a collector.
6. The process for the preparation of tungsten pentachloride according to claim 1, characterized in that: grinding the raw material tungsten hexachloride in the step (1) under inert gas until the particle size is 20-1000 mu m.
7. The method of preparing tungsten pentachloride according to claim 6, characterized in that: grinding the raw material tungsten hexachloride in the step (1) under inert gas until the particle size is 100-400 μm.
8. The process for the preparation of tungsten pentachloride according to claim 1, characterized in that: in the step (2): after the reactor is dried, introducing inert gas to purge for at least 2 hours, charging the raw material tungsten hexachloride into the reactor, then heating and preheating, wherein the heating rate is 5-20 ℃/min, and when the temperature is raised to 100 ℃, keeping the temperature for at least 2 hours.
9. The process for the preparation of tungsten pentachloride according to any one of claims 6 to 8, characterized in that: the inert gas is one of high-purity nitrogen, high-purity helium, high-purity neon and high-purity argon.
10. The process for the preparation of tungsten pentachloride according to any one of claims 1 to 8, characterized in that: the reactor, the purifier I and the purifier II are all made of high-temperature-resistant, reduction-resistant and corrosion-resistant materials, and the high-temperature-resistant, reduction-resistant and corrosion-resistant materials are glass, enamel or quartz.
11. The method of preparing tungsten pentachloride according to claim 5, characterized in that: the collector is made of high-temperature-resistant, reduction-resistant and corrosion-resistant materials, and the high-temperature-resistant, reduction-resistant and corrosion-resistant materials are glass, enamel or quartz.
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