Multi-Column Distillation for Boron Removal in Chlorosilane Purification
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Solution Overview
Problem
Current methods for purifying chlorosilanes, particularly trichlorosilane (TCS), are inefficient in removing boron impurities due to their similar boiling points with dichlorosilane (DCS), leading to incomplete separation and economic losses, with existing processes either requiring additional apparatus, introducing impurities, or resulting in significant TCS waste.
Innovation Solution
A multi-column distillation process is employed to separate boron-containing compounds from TCS, utilizing overhead and bottom streams in different columns to concentrate low-boiling and high-boiling boron compounds separately, allowing for the production of TCS with boron concentrations below 20 ppb while minimizing TCS loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If single-column distillation is used to separate BCl3 from TCS, then the separation process is simple, but the separation is incomplete due to similar boiling points
Solution Approach 1:
The distillation process is divided into multiple columns with different functions: a first distillation column for preliminary separation and a second distillation column for final purification. This segmentation allows each column to be optimized for specific separation tasks, achieving complete boron removal while maintaining process feasibility
Solution Approach 2:
The invention introduces a new dimension to the separation process by adding a second distillation column and implementing a two-stage distillation methodology. This transforms the single-stage separation into a multi-stage process, enabling complete boron removal that cannot be achieved in a single column
2Device complexity
If BCl3 is discharged together with TCS from the system, then the distillation process is simple, but significant TCS is lost as waste
Solution Approach 1:
The invention extracts boron compounds from the TCS stream through targeted distillation columns. By taking out boron in the overhead stream of the first column and further purifying in the second column, the process removes impurities without requiring discharge of large amounts of TCS, thus minimizing substance loss
Solution Approach 2:
The process discards boron-containing compounds in targeted streams while recovering and recycling TCS. The bottom stream from the first column and overhead from the second column contain concentrated boron and are disposed of, while purified TCS is recovered, maximizing substance utilization
3Manufacturing precision
If multi-column distillation is used to achieve high purity TCS, then boron removal efficiency is improved, but the device complexity increases
Solution Approach 1:
The purification system is segmented into two distinct distillation columns, each performing a specific separation function. The first column handles preliminary separation and the second column performs final purification, dividing the complex task into manageable stages that together achieve high boron removal efficiency
Solution Approach 2:
The invention uses intermediate streams as mediators between the two distillation columns. The bottom stream from the first column serves as feed to the second column, and overhead streams from both columns serve as intermediate boron-enriched streams for disposal. These intermediaries enable efficient mass and energy transfer between stages
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 effectively reduces boron content in TCS to semiconductor-grade levels, minimizing waste and operational costs, and allows for continuous, economically viable production of high-purity chlorosilanes with low risk of introducing further impurities.
Implementation Method 1
purifying the mixture of chlorosilanes by distillation in a plurality of distillation columns
Implementation Method 2
low-boiling boron compounds are branched off from the distillation columns by means of overhead streams containing boron-enriched DCS
Implementation Method 3
high-boiling boron compounds are branched off by means of a boron-enriched bottom stream containing high boilers
Data Source
AI summary
The invention relates to a process for purifying chlorosilanes by distillation, which includes providing a boron-containing mixture of chlorosilanes containing TCS, DCS and STC and purifying the mixture of chlorosilanes by distillation in a plurality of distillation columns, wherein low-boiling boron compounds are branched off from the distillation columns by overhead streams containing boron-enriched DCS and high-boiling boron compounds are branched off by a boron-enriched bottom stream containing high boilers.