Acetaldehyde Removal from Methyl Acetate via Pressurized Distillation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods fail to effectively remove acetaldehyde from methyl acetate/methanol mixtures due to its low boiling point and the formation of a low boiling azeotrope with methanol, leading to difficulties in separating acetaldehyde and methanol, which results in impurities in the carbonylation process for producing acetic acid.
Innovation Solution
A pressurized distillation column operating at elevated temperatures and pressures is used to separate acetaldehyde from a mixture of methyl acetate, methanol, and acetaldehyde, favoring the formation of low boiling 'free' acetaldehyde, which can be removed as an overhead vapor stream, thereby purifying the methyl acetate/methanol mixture for direct use in carbonylation processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional distillation is used to remove acetaldehyde from methyl acetate/methanol mixture, then the low boiling point of acetaldehyde should facilitate its removal, but acetaldehyde forms a low boiling azeotrope with methanol making separation difficult
Solution Approach 1:
The patent applies parameter changes by operating the distillation column at elevated pressures (e.g., 10-50 psig) and temperatures rather than atmospheric conditions. This shifts the vapor-liquid equilibrium to favor acetaldehyde in the overhead stream while preventing azeotrope formation, achieving >90% acetaldehyde removal in a single column without complex purification trains.
2Manufacturing precision
If methyl acetate is hydrolyzed to acetic acid and methanol prior to purification, then acetaldehyde removal becomes easier, but the process becomes more elaborate and time-consuming
Solution Approach 1:
The patent performs preliminary action by adjusting distillation operating parameters (pressure and temperature) before separation to create favorable equilibrium conditions. This prevents the need for subsequent hydrolysis reactions and multiple purification steps, directly achieving acetaldehyde removal from the original methyl acetate/methanol mixture in a single distillation operation.
Solution Approach 2:
The patent extracts acetaldehyde directly from the methyl acetate/methanol mixture using a single distillation column operating at elevated pressure. The overhead stream enriched in acetaldehyde is removed, and the purified methyl acetate/methanol mixture is obtained in the bottoms stream, eliminating the need for hydrolysis and elaborate treatment steps.
3Device complexity
If a single distillation column is used to remove acetaldehyde, then the process is simplified, but acetaldehyde and methanol form an azeotrope that is difficult to separate
Solution Approach 1:
The patent changes the operating parameters of the single distillation column to elevated pressures (10-50 psig) and temperatures. This parameter change modifies the vapor-liquid equilibrium to prevent azeotrope formation between acetaldehyde and methanol, allowing efficient separation in a single column with >90% acetaldehyde removal efficiency without requiring complex multi-column arrangements.
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 greater than 90% removal of acetaldehyde from the methyl acetate/methanol mixture, allowing for the direct feeding of the purified mixture to a carbonylation unit without further treatment, significantly improving the efficiency and reducing the need for elaborate purification steps.
Implementation Method 1
removal of acetaldehyde from a methyl acetate/methanol mixture by distillation at elevated pressure
Implementation Method 2
methanol reversibly forms a high boiling hemicaetal with acetaldehyde at relatively low temperatures and that at the higher temperatures and pressures of the invention, the methyl acetate/methanol/acetaldehyde equilibrium favors the formation of low boiling 'free' acetaldehyde
Data Source
AI summary
A method for removing acetaldehyde from a mixture of methyl acetate, methanol and acetaldehyde includes: (a) feeding the mixture of methyl acetate, methanol and acetaldehyde to a distillation column; (b) distilling the feed mixture of methyl acetate methanol and acetaldehyde at a pressure of 10 psig or more to generate an overhead vapor stream enriched in acetaldehyde as compared with the feed mixture and a residue stream depleted in acetaldehyde as compared with the feed mixture; and (c) withdrawing the residue stream depleted in acetaldehyde from the distillation column.