Tungsten Pentachloride Synthesis via Metal Reduction
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Solution Overview
Problem
Conventional methods for synthesizing tungsten pentachloride face challenges such as low yield, contamination with unintended substances, difficulty in controlling reaction conditions, safety concerns due to hydrogen leakage, and equipment rupture during reduction/distillation processes.
Innovation Solution
The method involves using high purity tungsten hexachloride as a starting material and a reducing agent like Bi, Hg, Sb, Ti, Al, or As, combined with distillation under reduced pressure, to achieve higher purity and safety in tungsten pentachloride production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If hydrogen reduction method is used to synthesize WCl5, then the synthesis can be performed, but the compound purity decreases due to generation of unreduced portion and excessively reduced portion forming WCl6 residue or WCl4, WCl2, W
Solution Approach 1:
The patent changes the reducing agent from hydrogen to metals (Bi, Hg, Sb, Ti, Al, P, or As) and modifies the reaction conditions including temperature range (80-210°C), pressure conditions (reduced pressure of 13 Pa or less), and molar ratios (WCl6:reducing agent from 2.8:1.0 to 3.2:1.0). These parameter changes prevent excessive reduction while achieving complete conversion, thereby improving both compound purity (95% or more) and yield simultaneously
Solution Approach 2:
The patent introduces high purity Bi, Hg, Sb, Ti, Al, P, or As as intermediary reducing agents that facilitate the reduction of WCl6 to WCl5 without causing further reduction to WCl4 or lower chlorides. These intermediaries enable precise control of the reduction process, eliminating the harmful side reactions that occur with hydrogen reduction while maintaining high productivity
2Ease of operation
If conventional hydrogen reduction is used, then synthesis can proceed, but it is very difficult to control flow rate of hydrogen and temperature in the producing process
Solution Approach 1:
The patent replaces hydrogen gas with solid metal reducing agents (Bi, Hg, Sb, Ti, Al, P, or As) and conducts the reaction in an inert atmosphere under reduced pressure. This eliminates the need to control hydrogen flow rate and temperature precisely, as the solid-liquid or solid-solid reaction system is inherently safer and easier to control, while preventing hydrogen leakage and explosion risks
Solution Approach 2:
The patent substitutes the gas-phase hydrogen reduction system with a solid-liquid or solid-solid reduction system using metals. This mechanical substitution eliminates the need for complex gas flow control equipment and temperature regulation systems, making the process easier to operate and more reliable, while maintaining effective reduction to produce WCl5 with 95% or higher compound purity
3Manufacturing precision
If reduction/distillation in sealed ampule using Bi, Hg, Sb or the like as reducing agent is used, then reduction can occur, but WCl4 and WCl2 are synthesized by excessive reduction or internal pressure increases causing ampule rupture
Solution Approach 1:
The patent employs dynamic pressure control by conducting the reduction reaction under reduced pressure (13 Pa or less) rather than in a sealed ampule. This allows the system to maintain controlled pressure conditions throughout the reaction, preventing dangerous pressure buildup while enabling complete reduction to WCl5 without excessive reduction to WCl4 or WCl2, achieving both precise composition control (95% or more purity) and safety
Solution Approach 2:
The patent extracts the reaction system from the sealed ampule configuration and performs reduction under controlled reduced pressure using high purity Bi, Hg, Sb, Ti, Al, P, or As. This extraction allows removal of excess reducing agent and byproducts through sublimation and distillation under reduced pressure, preventing excessive reduction while eliminating the pressure buildup problem that causes ampule rupture, thereby improving both product purity and safety
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 approach results in higher purity tungsten pentachloride with improved yield, reduced production time, and enhanced safety, while minimizing metal impurities and production costs.
Implementation Method 1
reducing the mixture of the reducing agent and the tungsten hexachloride by heating the mixture at a temperature of from 80 to 210° C.
Implementation Method 2
subjecting the reduced mixture of the reducing agent and the tungsten hexachloride to distillation under a reduced pressure by heating the reduced mixture at a temperature of from 120 to 290° C. under a pressure of 66 Pa or less to remove impurities
Implementation Method 3
subjecting the reduced product in which the impurities have been removed by the distillation under a reduced pressure to sublimation purification by heating the reduced product at a temperature of from 140 to 350° C. under a pressure of 13 Pa or less to obtain tungsten pentachloride
Data Source
AI summary
The purpose of the present invention is to safely synthesize high purity tungsten pentachloride at a higher yield and at a higher purity than in prior art. This method for producing tungsten pentachloride includes: a step of mixing a reducing agent selected from the group consisting of Bi, Hg, Sb, Ti, Al, P, and As with tungsten hexachloride uniformly in an inert atmosphere with a molar ratio of the tungsten hexachloride to the reducing agent being 2.8:1.0 to 3.2:1.0 to obtain a mixture; a step of heating the mixture of the reducing agent and the tungsten hexachloride to 80 to 210° C. at 13 Pa or lower and reducing the same; a step of heating the reduced product of the mixture of the reducing agent and the tungsten hexachloride to 120 to 290° C. at 66 Pa or lower and vacuum distilling the same to remove impurities; and a step of heating the reduced product from which impurities have been removed by the vacuum distillation to 140 to 350° C. at 13 Pa or lower and purifying the same by sublimation to obtain the tungsten pentachloride.