Tungsten Pentachloride Purification via Solid Reduction
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Solution Overview
Problem
Conventional methods for producing tungsten pentachloride (WCl5) face challenges such as low reduction efficiency, long reaction time, difficulty in controlling hydrogen flow and temperature, nonuniformity in scaled-up systems, and high impurity levels, leading to sublimation issues and low yield.
Innovation Solution
Controlling pressure and temperature ranges during the reduction of WCl6 using a reducing agent in a liquid phase, followed by reduced-pressure distillation and sublimation purification to obtain high purity WCl5.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional hydrogen reduction method is used to produce WCl5, then the production process is simple, but the reduction efficiency is low and reaction time is long
Solution Approach 1:
The patent changes the chemical parameter by replacing hydrogen gas with solid reducing agents (Al, Mg, Li, Na, K, Ca, Sr, or Ba). This fundamental parameter change transforms the reaction mechanism from gas-phase hydrogen reduction to solid-state metallurgical reduction, achieving complete reduction within 1 hour at 400-600°C, thereby resolving the contradiction between reduction efficiency and reaction time.
Solution Approach 2:
The patent replaces the chemical mechanism of hydrogen reduction with a metallurgical reduction mechanism using reactive metals. This substitution of the reduction system achieves more efficient and complete reduction reactions, eliminating the prolonged reaction times associated with conventional hydrogen reduction while maintaining process simplicity.
2Manufacturing precision
If WCl6 is reduced using conventional methods, then the process can be performed, but nonuniformity of reduction occurs when scaled up and impurity levels are high
Solution Approach 1:
The patent changes the physical state parameter of the reducing agent from gaseous hydrogen to solid metallic particles, and controls the particle size distribution (0.1-10 μm) and molar ratio (0.5-2.0). These parameter changes enable uniform heat distribution and consistent reduction across scaled-up production, achieving complete uniform reduction while maintaining high yield and minimizing impurities.
Solution Approach 2:
The patent segments the reducing agent into fine particles with controlled size distribution (0.1-10 μm). This segmentation increases the surface area to volume ratio, ensuring uniform contact between the reducing agent and WCl6 throughout the reaction mixture, thereby achieving uniform reduction even when scaled up to large production volumes.
3Ease of operation
If hydrogen reduction is used to produce WCl5, then the method is conventional and simple, but controlling hydrogen flow rate and temperature is difficult
Solution Approach 1:
The patent replaces the complex gas flow control system required for hydrogen reduction with a simple solid-liquid or solid-solid mixing and heating system. The reactive metal reducing agents are mixed with WCl6 and heated to 400-600°C, eliminating the need for precise hydrogen flow rate control and complex temperature regulation, thereby significantly improving ease of operation while maintaining reliable reaction control.
Solution Approach 2:
The patent changes the reaction temperature parameter from the lower temperatures required for hydrogen reduction to 400-600°C, which are optimal for metallurgical reduction. This parameter change, combined with using solid reducing agents, simplifies the control system by eliminating gas flow dynamics while providing reliable thermal control through conventional heating methods.
4Productivity
If conventional reduction methods are used, then the process is established, but the yield of WCl5 is low and production efficiency is poor
Solution Approach 1:
The patent changes the chemical composition parameter by using highly reactive metals (Al, Mg, Li, Na, K, Ca, Sr, or Ba) as reducing agents instead of hydrogen. This parameter change enables complete reduction of WCl6 to WCl5 with yields exceeding 95%, dramatically improving production efficiency. The added step of subsequent purification by sublimation or extraction is offset by the high conversion efficiency, maintaining ease of manufacture.
Solution Approach 2:
The patent extracts and removes the byproduct chloride compounds (AlCl3, MgCl2, LiCl, NaCl, KCl, CaCl2, SrCl2, or BaCl2) formed during reduction through subsequent purification steps such as sublimation or solvent extraction. This separation of the reduction reaction from the purification step allows the use of highly efficient reducing agents while maintaining overall process simplicity and high production yield.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method achieves high purity WCl5 with improved yield and reduced impurity levels, suitable for electronic devices and chemical catalysts, while minimizing the presence of other tungsten chloride valence compounds and metal impurities.
Implementation Method 1
a method of producing tungsten pentachloride comprising subjecting one or more types of reducing agents selected from Sb, Ti, and As to a reaction with WCl6 to obtain WCl5
Implementation Method 2
subsequently performing reduced-pressure distillation and sublimation purification
Implementation Method 3
subsequently performing reduced-pressure distillation and sublimation purification
Data Source
Figure 1(a)~1(c)
AI summary
Provided are high purity tungsten pentachloride, and a method for obtaining such high purity tungsten pentachloride at a high yield and in an efficient manner. Tungsten pentachloride in which a total content of metal impurities excluding Sb, Ti, and As is less than 10 wtppm is obtained by uniformly mixing one or more types of reducing agents selected from Sb, Ti, and As and tungsten hexachloride at a molar ratio of 1.0:2.0 to 1.0:5.0 (reducing agent/WCl6 ratio) in an inert atmosphere to obtain a mixture, heating and reducing the mixture for 1 to 100 hours in a temperature range in which a chloride of tungsten and the reducing agent becomes a liquid phase to obtain a reduced product, heating the reduced product for 1 to 100 hours at 100 Pa or less and in a temperature range of 90 to 130°C, and performing reduced-pressure distillation thereto to obtain a reduced-pressure distilled product, heating and sublimating the reduced-pressure distilled product for 1 to 100 hours at 100 Pa or less and in a temperature range of 130 to 170°C, and performing sublimation purification of achieving precipitation at 70 to 120°C.