Extractive Distillation of Monochloroacetic and Dichloroacetic Acids
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Solution Overview
Problem
Current methods for separating monochloroacetic acid (MCA) and dichloroacetic acid (DCA) are inefficient, as they require multiple crystallization steps and result in a mother liquor that cannot be converted into a sellable product, and existing extractive distillation methods using sulfuric acid or sulfolane do not achieve sufficient separation or are economically unfeasible.
Innovation Solution
A process using a chemically stable extractive agent with a specific BF3 affinity and an organic solvent with defined pKa and boiling point characteristics, which are contacted with the MCA/DCA mixture to enhance relative volatility, allowing for effective separation through extractive distillation and easy regeneration of the extractive agent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If simple distillation is used to separate MCA and DCA, then the process is simple, but separation is ineffective due to close boiling points (relative volatility about 1)
Solution Approach 1:
An extractive agent is introduced as an intermediary substance that selectively interacts with DCA through complexation, thereby mediating the separation process. The extractive agent forms a complex with DCA that has different volatility characteristics, enabling effective separation from MCA while maintaining process feasibility
Solution Approach 2:
The relative volatility between MCA and DCA is changed by introducing the extractive agent. The extractive agent alters the vapor-liquid equilibrium characteristics of the mixture, increasing the volatility difference between the two components and enabling effective distillation separation
2Manufacturing precision
If sulfuric acid is used as extractive agent, then relative volatility increases, but MCA requires additional crystallization and catalyst deactivation occurs
Solution Approach 1:
The extractive agent is designed to be easily regenerable and reusable, replacing the consumable nature of sulfuric acid. The new extractive agent can be recovered and reused multiple times without degradation, eliminating the need for continuous replenishment and reducing waste treatment requirements
Solution Approach 2:
The strong interaction between the extractive agent and DCA, which initially seemed to cause tight binding difficult to reverse, is converted into a benefit by designing the system so that this strong complexation can be easily reversed under controlled conditions, enabling both effective separation and easy regeneration
3Ease of operation
If sulfolane is used as extractive agent, then extractive agent recovery is easy, but separation degree is insufficient
Solution Approach 1:
The extractive agent is designed with optimized interaction parameters - the complexation strength is tuned to achieve both effective separation (sufficient volatility difference) and easy regeneration (reversible complexation). The molecular structure and chemical properties are selected to provide optimal balance between these competing requirements
4Manufacturing precision
If multiple crystallization steps are used to reduce DCA concentration, then MCA purity is improved, but mother liquor cannot be converted to sellable product and process is economically unfeasible
Solution Approach 1:
The extractive agent acts as a mediator that enables the mother liquor to be processed into sellable products. By adding the extractive agent to the mother liquor and performing extractive distillation, both MCA and DCA can be recovered in high purity forms, converting what was previously waste into valuable products
Solution Approach 2:
Instead of discarding the mother liquor after multiple crystallizations, the process recovers both MCA and DCA from the mother liquor through extractive distillation. This transforms a waste stream into valuable recovered materials, improving overall process economics and sustainability
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 achieves good separation of MCA and DCA, allowing for the regeneration of the extractive agent and reducing waste, making it economically feasible and improving the purity of the recovered DCA for reuse.
Implementation Method 1
it is known that components in a mixture having a relative volatility value close to 1 may be separated via extractive distillation. Extractive distillation is a distillation in the presence of a third component (hereinafter denoted as extractive agent or EA) that interacts differently with the components of the mixture, thereby causing their relative volatility to change
Implementation Method 2
Upon distillation, DCA containing a small amount of MCA is distilled over the top, while the bottom product is a mixture of sulfuric acid and MCA containing a very small amount of DCA
Data Source
AI summary
The present invention pertains to a process for separating monochloroacetic acid and dichloroacetic acid from one another via extractive distillation using (a) an extractive agent that is chemically stable and has a BF3 affinity of between 65 kJ/mole and 110 kJ/mole and (b) an organic solvent that is either an acid with a lowest pKa of between 3.0 and 6.5 or a base with a BF3 affinity of between 40 kJ/mole and 75 kJ/mole with the proviso that said BF3 affinity is lower than the BF3 affinity of the extractive agent, said organic solvent being chemically stable, and having a boiling point at atmospheric pressure of at least 468K, comprising the steps of (i) contacting a mixture comprising monochloroacetic acid and dichloroacetic acid with the extractive agent, (ii) distilling the mixture obtained in step (i) to obtain a monochloroacetic acid stream and a stream comprising dichloroacetic acid and the extractive agent, (iii) subjecting the stream comprising dichloroacetic acid and the extractive agent to a regeneration step, wherein the organic solvent is contacted with the mixture comprising monochloroacetic acid and dichloroacetic acid of step (i), or wherein the organic solvent is contacted with the mixture obtained in step (i) prior to and/or during step (ii), or wherein the organic solvent is contacted with the stream comprising dichloroacetic acid and the extractive agent obtained in step (ii) prior to or during step (iii), or any combination thereof.