Trichlorosilane Purification via Chlorine Disproportionation
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Solution Overview
Problem
Conventional methods face difficulties in separating methyldichlorosilane from trichlorosilane due to their close boiling points, leading to a high burden on distillation purification and residual carbon impurities in trichlorosilane production for semiconductor-grade polycrystalline silicon.
Innovation Solution
A method involving the distillation of a mixture containing methyldichlorosilane, tetrachlorosilane, and trichlorosilane to fractionate a methyldichlorosilane-rich fraction, followed by heating to disproportionate chlorine and convert methyldichlorosilane into methyltrichlorosilane, which is then purified by distillation to separate high-purity trichlorosilane, without the need for excessive distillation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If distillation is used to separate trichlorosilane from methyldichlorosilane, then trichlorosilane can be purified, but the close boiling points (41°C for methyldichlorosilane and 32°C for trichlorosilane) make the separation difficult and require excessive distillation
Solution Approach 1:
The invention changes the chemical composition parameter by converting methyldichlorosilane into methyltrichlorosilane through chlorine disproportionation reaction. This parameter change results in a significant boiling point difference (66°C for methyltrichlorosilane vs. 32°C for trichlorosilane), making separation by distillation feasible and reducing process complexity while maintaining high purity.
2Manufacturing precision
If conventional distillation is used to remove carbon impurities, then some purification is achieved, but carbon-containing compounds from carbon electrodes and CVD reactor members remain in the product
Solution Approach 1:
The invention converts the harmful carbon impurities and carbon-derived methylchlorosilanes into separable components through the chlorine disproportionation reaction. The reaction selectively converts methyldichlorosilane (containing carbon impurities) into methyltrichlorosilane, which has a higher boiling point and can be easily separated from trichlorosilane by distillation, thus transforming the harmful carbon-containing impurities into removable substances.
3Manufacturing precision
If methyldichlorosilane is removed by distillation, then trichlorosilane purity improves, but the close boiling points create a high distillation burden and require excessive energy input
Solution Approach 1:
The invention changes the boiling point parameter of methyldichlorosilane by converting it to methyltrichlorosilane through chlorine disproportionation. This parameter change creates a large boiling point difference (66°C vs. 32°C), which significantly reduces the distillation burden and energy consumption required for separation, while achieving high purity trichlorosilane production.
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 simplifies the removal of methyldichlorosilane by converting it into methyltrichlorosilane with a higher boiling point, reducing the distillation burden and achieving high-purity trichlorosilane production.
Implementation Method 1
heating the fraction thus fractionated to disproportionate chlorine between methyldichlorosilane and tetrachlorosilane and thus convert the methyldichlorosilane into methyltrichlorosilane
Implementation Method 2
distilling the mixture to fractionate a fraction with a higher content of methyldichlorosilane than the mixture before distillation
Implementation Method 3
purifying the fraction after the disproportionation containing the methyltrichlorosilane by distillation to separate trichlorosilane
Data Source
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AI summary
A mixture containing methyldichlorosilane, tetrachlorosilane, and trichlorosilane is distilled to fractionate a fraction with a higher content of methyldichlorosilane than the mixture before distillation. Subsequently, the fraction thus fractionated is heated to disproportionate chlorine between methyldichlorosilane and tetrachlorosilane to disproportionate methyldichlorosilane into methyltrichlorosilane. Subsequently, the fraction after disproportionation containing methyltrichlorosilane is purified by distillation to separate high-purity trichlorosilane. Having a close boiling point to that of trichlorosilane (32°C), which is a target product to be purified by distillation, removal of methyldichlorosilane (boiling point of 41°C) has been difficult. The present invention removes methyldichlorosilane more easily by converting it into methyltrichlorosilane (boiling point of 66°C) through disproportionation of chlorine between methyldichlorosilane and tetrachlorosilane.