Continuous Lactic Ester Purification via Vacuum Distillation
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Solution Overview
Problem
The production of ethyl lactate from lactic acid and ethanol is challenging due to spontaneous formation of water, leading to hydrolysis, azeotrope formation between ethanol and water, and the formation of ethyl lactate oligomers, which complicate purification and separation.
Innovation Solution
A continuous process involving esterification in the presence of excess lactic acid, where ethanol is introduced to catalyze the reaction, and the vapor phase containing water, ethanol, ethyl lactate, and traces of lactic acid is continuously extracted and separated using distillation columns under reduced pressure, allowing for self-catalysis and minimizing oligomerization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If esterification reaction is carried out with excess ethanol to suppress oligomerization, then ethyl lactate production is improved, but water formation causes hydrolysis and azeotrope formation complicating purification
Solution Approach 1:
The purification process is divided into multiple distillation columns (first distillation column for water-ethanol separation, second distillation column for ethyl lactate recovery) to handle the complex mixture systematically. Each column performs a specific separation function, making the overall purification manageable despite the complexity introduced by water formation and azeotrope issues.
Solution Approach 2:
The process operates under reduced pressure (vacuum conditions) to change the boiling points and azeotrope characteristics of the mixture components. This parameter change allows for effective separation of water-ethanol azeotrope and facilitates the distillation process, enabling purification that would be difficult or impossible at atmospheric pressure.
2Productivity
If esterification is performed at high temperature to increase reaction rate, then productivity is improved, but oligomerization and hydrolysis reactions are promoted
Solution Approach 1:
The esterification reaction is carried out continuously with continuous removal of water and ethyl lactate via distillation. This continuous operation maintains the reaction in a state that favors monomer formation while preventing the accumulation of conditions that would promote oligomerization. The continuous extraction of products shifts the equilibrium and prevents reverse reactions.
Solution Approach 2:
Water and ethyl lactate are continuously extracted from the reaction medium through distillation under vacuum. By removing these products as they form, the system prevents their participation in reverse hydrolysis reactions and oligomerization, thereby maintaining high productivity while minimizing harmful side reactions.
3Manufacturing precision
If water is removed during esterification to prevent hydrolysis, then product purity is improved, but azeotrope formation between ethanol and water requires additional purification steps
Solution Approach 1:
The water removal and purification process is segmented into multiple distillation columns. The first distillation column handles the water-ethanol azeotrope separation, while the second distillation column recovers pure ethyl lactate. This segmentation allows each column to be optimized for its specific separation task, achieving high purity despite the multi-step process.
Solution Approach 2:
Operating under reduced pressure changes the vapor pressure relationships between components, allowing the first distillation column to effectively separate water from ethanol-ethyl lactate mixture. This parameter change enables the removal of water without forming difficult-to-break azeotropes, simplifying the overall purification compared to atmospheric pressure operation.
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 achieves purified ethyl lactate with a purity of 97% or higher, low water content, and reduced acidity, effectively overcoming the challenges of oligomerization and azeotrope formation, resulting in a high-quality product.
Implementation Method 1
the vapor phase composed of water, ethanol, ethyl lactate formed as well as traces of lactic acid are continuously extracted
Implementation Method 2
This gas mixture is injected approximately halfway up a first distillation column, working at this same reduced pressure where it is separated into two fractions
Data Source
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AI summary
A continuous process for obtaining a lactic ester, characterized in that it comprises the following steps: a) reaction for esterification of a composition comprising an alcohol in the presence of a composition comprising lactic acid in excess; b) extraction of a vapour phase of this reaction medium, loaded with lactic ester, alcohol, water and traces of lactic acid; c) distillation of the vapour phase obtained in step b) so as to recover the lactic ester, the alcohol and the water at the top; d) distillation of the fraction obtained in step c) so as to recover the purified lactic ester at the bottom.