Acetic Acid Distillation Conditions to Suppress Acetal Formation
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Solution Overview
Problem
Conventional processes for producing acetic acid are inefficient in removing acetaldehyde impurities, leading to low-purity acetic acid due to the formation of acetals and hemiacetals, which are difficult to separate using existing distillation methods.
Innovation Solution
A process that controls the operating conditions in a distillation column, including temperature, water composition, and acetic acid composition, to inhibit acetal and hemiacetal formation, allowing efficient separation of acetaldehyde and reducing the formation of 1,1-dimethoxyethane, thereby improving acetic acid purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional distillation methods are used to remove acetaldehyde, then separation is attempted, but acetal formation interferes with efficient separation and purity is reduced
Solution Approach 1:
The patent changes operating parameters (temperature, pressure, composition ratios) in the distillation column to control acetal formation. By maintaining specific temperature ranges and composition profiles, the system prevents acetal from forming in significant amounts, enabling efficient acetaldehyde separation while achieving high acetic acid purity
Solution Approach 2:
The patent introduces water as an intermediary substance that participates in the distillation process. Water forms azeotropic mixtures with acetaldehyde and other components, facilitating their separation from acetic acid. The water-rich vapor phase carries away acetaldehyde impurities while leaving purified acetic acid in the liquid phase
2Manufacturing precision
If acetaldehyde is removed by conventional extraction or reaction methods, then some purification is achieved, but the process complexity increases and efficiency decreases
Solution Approach 1:
The patent modifies the distillation process parameters (temperature, pressure, feed composition, reflux ratio) to optimize acetaldehyde removal. By operating at elevated temperatures and controlling the vapor-liquid equilibrium, the system achieves efficient separation without requiring complex extraction or reaction units, thereby reducing overall process complexity
Solution Approach 2:
The distillation column serves multiple functions simultaneously: it separates acetaldehyde from acetic acid, controls acetal formation, and produces a purified product stream. This multi-functional approach eliminates the need for separate extraction or reaction units, simplifying the overall process while maintaining high purity
3Productivity
If methanol carbonylation is used to produce acetic acid, then high yields are achieved, but acetaldehyde impurities are generated that are difficult to remove
Solution Approach 1:
The patent extracts acetaldehyde from the reaction mixture using a distillation column. The acetaldehyde, being more volatile than acetic acid, is carried over in the vapor phase and separated from the liquid acetic acid product. This extraction method effectively removes the impurity while preserving the high yield of the carbonylation process
Solution Approach 2:
The patent changes the temperature and composition parameters of the distillation column to selectively remove acetaldehyde. By operating at temperatures that favor vaporization of acetaldehyde and controlling the vapor-liquid equilibrium, the system achieves high purity acetic acid while maintaining the high yield of the carbonylation reaction
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 effectively reduces acetaldehyde impurities by inhibiting acetal formation, resulting in higher-purity acetic acid production with reduced acetaldehyde content in the product stream.
Implementation Method 1
distilling a first mixture containing at least methanol, water, C1-C12 alkyl iodides, and at least one permanganate reducing compounds (e.g., acetaldehyde) at specific operating conditions in a distillation column
Implementation Method 2
separation of acetaldehyde from the first mixture
Implementation Method 3
overhead extraction of a permanganate reducing compound (PRC), such as but not limited to acetaldehyde
Data Source
AI summary
A process for producing acetic acid is provided that is capable of lowering acetaldehyde mass composition in acetic acid. The process for producing acetic acid according to the present invention comprises at least one distillation step that satisfies the following operating conditions (i) temperature in a lower portion of the distillation column is not less than 40° C.; (ii) water mass composition in the lower stream is not less than 0.3 wt. %; or (iii) acetic acid mass composition in the lower stream on weight percentage basis is greater than the acetic acid mass composition in the first mixture; wherein the methanol mass composition in the first mixture is less than or equal to 2 wt. %.