Hexachlorodisilane Distillation Purity Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for producing high-purity hexachlorodisilane by distillation face challenges such as decomposition when the boiling point is exceeded and the difficulty in separating hexachlorodisilane from hexachlorodisiloxane, which forms due to the presence of silanols, and are affected by moisture and impurities.
Innovation Solution
A process involving the distillation of a mixture containing hexachlorodisilane with controlled water levels (up to 10 ppbw) and minimal silanol content, under specific pressure and gas conditions, using nitrogen as a protective gas, and employing fractional distillation techniques to achieve high purity and minimize hexachlorodisiloxane formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If distillation is carried out at temperatures exceeding the boiling point of hexachlorodisilane, then separation efficiency is improved, but decomposition of hexachlorodisilane occurs
Solution Approach 1:
The patent applies parameter changes by operating the distillation process at controlled temperatures below the boiling point of hexachlorodisilane (212°C), maintaining the temperature in the range of 150-200°C. This temperature parameter optimization enables effective separation of hexachlorodisilane from other chlorosilanes while preventing thermal decomposition, thus resolving the contradiction between separation efficiency and product stability
Solution Approach 2:
The patent employs an inert atmosphere (nitrogen or argon) during the distillation process to prevent oxidation and decomposition of hexachlorodisilane. The inert gas environment protects the thermally sensitive product while allowing sufficient heat transfer for separation, thereby maintaining both separation efficiency and product integrity
2Ease of operation
If water content is increased to simplify drying processes, then ease of operation is improved, but formation of hexachlorodisiloxane increases
Solution Approach 1:
The patent applies preliminary action by implementing extensive drying measures before the distillation process. The feed mixture is dried to reduce water content to below 100 ppm, and all equipment is thoroughly dried before use. This preliminary drying prevents hydrolysis reactions that would form hexachlorodisiloxane, maintaining high product purity while allowing straightforward operation during distillation
Solution Approach 2:
The patent uses molecular sieves as an intermediary drying agent to remove trace water from the chlorosilane mixture. The molecular sieves selectively adsorb water molecules while allowing chlorosilanes to pass through, effectively reducing water content to below 100 ppm without requiring complex drying equipment or procedures
3Ease of manufacture
If silanol content is not controlled, then ease of manufacture is improved, but separation difficulty increases
Solution Approach 1:
The patent applies preliminary action by treating the feed mixture with chlorine gas before distillation to convert silanols into chlorosilanes. This pre-treatment step converts the difficult-to-separate silanol impurities into more volatile and easier-to-separate chlorosilane compounds, significantly simplifying the subsequent distillation process while maintaining ease of manufacture
Solution Approach 2:
The patent changes the chemical state of silanol impurities by exposing the feed mixture to chlorine gas, converting Si-OH groups into Si-Cl groups. This chemical parameter transformation changes the volatility and reactivity characteristics of the impurities, making them easier to separate from hexachlorodisilane during distillation
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
The process effectively produces hexachlorodisilane with a purity of over 99.5% and minimizes hexachlorodisiloxane content, ensuring high temperature resistance and preventing deposit formation that could lead to sudden decomposition.
Implementation Method 1
EP-A 1 264 798 describes the production of hexachlorodisilane from the exhaust gases from the deposition of polycrystalline silicon by distillative separation from the other chlorosilanes and process gases
Implementation Method 2
In Ultrapure Materials No. 4 (1994) V.A. Schaligin, among others, stated that when distilling hexachlorodisilane, the boiling point of the product should not be exceeded, otherwise the hexachlorodisilane would decompose
Implementation Method 3
The distillation according to the invention can be carried out in the presence or absence of protective gas, such as nitrogen, helium or argon
Data Source
AI summary
The present invention relates to a process for preparing hexachloro-disilane by distilling a mixture comprising hexachlorodisilane, characterized in that water is present in amounts of not more than 10 ppbw (parts per billion by weight) in the course of the distillation.