Acetic Acid Purification with Acetal Impurity Control
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Solution Overview
Problem
Existing carbonylation processes for producing acetic acid face challenges in reducing the concentration and preventing the formation of acetal impurities like 1,1-dimethoxyethane, which affect the quality and efficiency of the acetic acid product by forming additional impurities such as acetaldehyde.
Innovation Solution
A multi-step process involving reaction, evaporation, distillation, phase separation, and additional purification steps to control the mass composition of 1,1-dimethoxyethane to less than 0.2 wt.%, including regulating methanol amounts and residence times in distillation columns, and using ion-exchange resins to remove impurities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional carbonylation process is used to produce acetic acid, then production efficiency is high, but acetal impurities like 1,1-dimethoxyethane form and reduce product quality
Solution Approach 1:
The patent applies preliminary action by controlling the concentration of 1,1-dimethoxyethane to not more than 0.2 wt.% before it can form harmful by-products. This preventive measure stops the acetal impurity from reaching levels that would trigger further unwanted reactions, thereby maintaining high production efficiency while ensuring product quality.
Solution Approach 2:
The patent changes the concentration parameter of 1,1-dimethoxyethane to not more than 0.2 wt.% in the liquid stream. This parameter change prevents the formation of acetaldehyde and other harmful by-products while maintaining the efficiency of the carbonylation process.
2Productivity
If acetal impurities are present in the reaction stream, then production continues, but additional impurities like acetaldehyde form through subsequent reactions
Solution Approach 1:
The patent applies preliminary anti-action by preemptively controlling the concentration of 1,1-dimethoxyethane to not more than 0.2 wt.% before it can undergo aldol condensation to form acetaldehyde and other harmful impurities. This prevents the chain reaction of impurity formation while allowing continuous production to proceed.
3Manufacturing precision
If distillation and phase separation steps are added to remove impurities, then product quality improves, but process complexity increases
Solution Approach 1:
The patent applies preliminary action by controlling the concentration of 1,1-dimethoxyethane to not more than 0.2 wt.% in advance, which prevents the formation of most harmful by-products. This reduces the burden on subsequent distillation and phase separation steps, allowing for simpler purification processes while still achieving high product 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
The process effectively reduces 1,1-dimethoxyethane and acetaldehyde levels, maintaining high product quality and efficiency by minimizing impurity formation and buildup, thereby improving the potassium permanganate test value of acetic acid.
Implementation Method 1
The reaction mixture is evaporated in an evaporator (e.g., flasher), and the flashed vapor portion is purified
Implementation Method 2
condensing the first overhead stream in one or more condensers, collecting the condensates in a receiver
Implementation Method 3
separating the condensates into an upper phase and a lower phase
Implementation Method 4
an iodine removal step of contacting the acetic acid product stream with an ion-exchange resin and separating an iodine compound from the acetic acid product stream
Data Source
AI summary
Provided herein is a process for the production and purification of acetic acid. In particular, this disclosure relates to improved processes for producing and purifying acetic acid by the carbonylation of methanol in the presence of a Group VIII metal carbonylation catalyst. The acetic acid production and purification process described herein controls the formation and mass composition of acetal impurities, such as 1,1-dimethoxyethane.