Mixed Diol Separation via Hydrophobic Solvent Extraction
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Solution Overview
Problem
Current methods for separating mixed diol streams, particularly those containing two-, three-, and four-carbon diols, face challenges due to close boiling points and the formation of azeotropes, making complete separation by single-feed fractional distillation difficult or impossible.
Innovation Solution
A process involving the extraction of mixed diol streams using hydrophobic solvents such as alkanols, ketones, and trialkylphosphine oxides to separate ethylene glycol and other diols, forming a raffinate phase with a major amount of ethylene glycol and a minor amount of three- and four-carbon diols, and an extract phase with a major amount of these diols and a minor amount of ethylene glycol.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If single-feed fractional distillation is used to separate mixed diol streams, then the process is simple and common, but complete separation is difficult or impossible due to close boiling points and azeotrope formation
Solution Approach 1:
The patent introduces a separating agent as an intermediary substance that forms a heterogeneous azeotrope with the diol mixture. This agent mediates the separation process by creating a distinct phase that selectively carries certain components, enabling complete separation where ordinary distillation fails due to the close boiling points and azeotrope formation between diol components
Solution Approach 2:
The patent changes the physical-chemical parameters of the system by adding a separating agent that alters the volatility relationships and phase behavior of the diol mixture. This parameter change enables the formation of a heterogeneous azeotrope system with different separation characteristics, allowing complete separation of components that otherwise cannot be separated by temperature-based distillation alone
2Manufacturing precision
If ordinary fractional distillation is used, then the equipment and operation are straightforward, but separation into pure fractions is extremely difficult due to numerous azeotropes
Solution Approach 1:
A separating agent is introduced as a mediator that interacts with the diol components to form a heterogeneous azeotrope. This agent simplifies the manufacturing process by creating a clear phase separation mechanism that readily produces pure fractions, eliminating the complexity of managing multiple overlapping azeotropes through sophisticated distillation column configurations
3Manufacturing precision
If extraction with hydrophobic solvents is used to separate diols, then high purity ethylene glycol is achieved, but the process becomes more complex than simple distillation
Solution Approach 1:
The patent utilizes phase transition phenomena by forming a heterogeneous azeotrope that separates into distinct liquid phases. This phase transition approach achieves high purity ethylene glycol separation through liquid-liquid equilibrium, which is operationally simpler than complex multi-column extraction processes while maintaining the high separation precision required for ethylene glycol purification
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 process efficiently separates ethylene glycol and other diols from mixed diol streams, achieving high purity of ethylene glycol and recovering significant amounts of three- and four-carbon diols, overcoming the limitations of traditional distillation methods.
Implementation Method 1
extracting the mixed diol stream with an extractant to form a raffinate phase and an extract phase
Implementation Method 2
extracting the mixed diol stream, comprising ethylene glycol, three-carbon diols, and four-carbon diols with an extractant to form a raffinate phase comprising a major amount of the ethylene glycol and a minor amount of the three-carbon diols and/or four-carbon diols
Data Source
AI summary
Disclosed is a process for the purification of a mixed diol stream. The mixed diol stream comprising two-, three-, and four-carbon diols is separated into component diols by extraction with a hydrophobic solvent mixture. The diols recovered in the extractant may be removed from the extractant stream by back extraction with water or by distillation with an azeotrope-forming agent present, preferably an azeotroping agent already present in the extractant mixture.