Extractive Distillation Separation of Monochloroacetic and Dichloroacetic Acids
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Solution Overview
Problem
Current methods for separating monochloroacetic acid and dichloroacetic acid are inefficient, with existing extractive distillation techniques either requiring additional refining steps or leaving behind impurities, and simple distillation is impractical due to similar boiling points and volatility.
Innovation Solution
The process involves using specific extractive agents like tetraglyme, diethylene glycol dibutyl ether, dihexyl ether, or dihexyl ketone in extractive distillation to separate monochloroacetic acid and dichloroacetic acid, with the agent being regenerated and reused, allowing for effective separation and reducing the need for subsequent crystallization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If simple distillation is used to separate monochloroacetic acid and dichloroacetic acid, then the process is simple, but separation is impractical due to similar boiling points and volatility
Solution Approach 1:
An extractive agent is introduced as an intermediary substance that selectively interacts with one of the components (monochloroacetic acid or dichloroacetic acid) to modify its volatility. This mediator creates a significant volatility difference between the two components, enabling effective separation by distillation despite their initially similar boiling points.
Solution Approach 2:
The relative volatility parameter of the mixture is changed by adding the extractive agent. The agent alters the vapor-liquid equilibrium characteristics of the system, transforming the mixture from one with near-unity relative volatility (unseparable by simple distillation) to one with sufficient volatility difference for practical separation.
2Manufacturing precision
If extractive distillation with sulfuric acid is used to separate monochloroacetic acid and dichloroacetic acid, then separation is achieved, but additional crystallization step is required and catalyst deactivation occurs
Solution Approach 1:
The patent employs an extractive agent that can be easily removed and regenerated, effectively making it a temporary, reusable component rather than a permanent process additive. This allows the agent to perform its separation function and then be discarded or regenerated without complicating the overall process, unlike sulfuric acid which requires additional crystallization steps.
Solution Approach 2:
The extractive agent is selected to have specific physical and chemical properties (volatility, selectivity, stability) that differ from sulfuric acid. These parameter changes enable the agent to achieve separation while being easily removable, thus avoiding the need for additional refining steps and preventing catalyst deactivation issues.
3Manufacturing precision
If multiple crystallization steps are used to purify monochloroacetic acid, then purity is improved, but time and economic feasibility deteriorate
Solution Approach 1:
The extractive agent acts as a mediator that enables single-stage separation of the mother liquor containing both monochloroacetic acid and dichloroacetic acid. This intermediary approach replaces multiple sequential crystallization operations with a single extractive distillation step, significantly reducing processing time and improving economic feasibility while maintaining high purity.
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 achieves a significant improvement in the separation of monochloroacetic acid and dichloroacetic acid, enabling the regeneration and reuse of the extractive agent, thus making the process economically feasible and reducing waste.
Implementation Method 1
an extractive agent selected from the group consisting of tetraglyme, diethylene glycol dibutyl ether, dihexyl ether, diethylene glycol dipentyl ether, and dihexyl ketone... contacting a mixture comprising monochloroacetic acid and dichloroacetic acid with an extractive agent... the extractive agent which interacts differently with the components of the mixture, thereby causing their relative volatility to change
Implementation Method 2
distilling the mixture to obtain a monochloroacetic acid stream and a stream comprising dichloroacetic acid and the extractive agent... Upon distillation, dichloroacetic acid containing a small amount of monochloroacetic acid is distilled over the top
Data Source
AI summary
The present invention pertains to a process for separating monochloroacetic acid and dichloroacetic acid from one another via extractive distillation, comprising the steps of (i) contacting a mixture comprising monochloroacetic acid and dichloroacetic acid with an extractive agent which is chemically stable and which hasa BF3 affinity of between 65 kJ/mole and 110 kJ/mole, (ii) distilling the mixture to obtain a monochloroacetic acid stream and a stream comprising dichloroacetic acid and the extractive agent, and (iii) regenerating the extractive agent.