Acetic Acid Purification via Distillation and Extraction
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Solution Overview
Problem
Current processes for producing acetic acid through methanol carbonylation with Group VIII metal catalysts face challenges in removing permanganate reducing compounds and multi-carbon alkyl iodides, which affect catalyst poisoning and product quality, especially when trying to increase production rates or reduce impurities.
Innovation Solution
A process involving the separation of carbonylation products into vapor and catalyst phases, followed by distillation and extraction steps to enrich and remove permanganate reducing compounds, primarily acetaldehyde, using a single distillation column and water extraction to achieve high purity acetic acid production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional carbonylation processes are used to produce acetic acid, then production rate can be increased, but permanganate reducing compounds and multi-carbon alkyl iodides accumulate, causing catalyst poisoning and product quality degradation
Solution Approach 1:
The patent applies preliminary action by removing permanganate reducing compounds and multi-carbon alkyl iodides from the reaction stream before they can accumulate and poison the catalyst. This is achieved through selective extraction using a liquid membrane module that contacts the reaction stream, selectively removing harmful impurities while allowing acetic acid and other desired products to pass through. This preventive removal approach maintains catalyst stability and enables sustained high production rates.
2Manufacturing precision
If conventional purification methods are used to remove impurities, then product quality improves, but energy consumption and equipment complexity increase
Solution Approach 1:
The patent uses an intermediary substance - a liquid membrane - to facilitate selective removal of impurities. The liquid membrane module acts as a mediator between the reaction stream and the purification process, allowing selective extraction of permanganate reducing compounds and multi-carbon alkyl iodides based on their differential solubility and affinity for the liquid membrane material. This intermediary approach achieves high product quality with lower energy consumption compared to conventional thermal purification methods.
3Manufacturing precision
If multiple distillation columns are used to remove impurities, then purification effectiveness increases, but device complexity and capital costs increase
Solution Approach 1:
The patent applies the extraction principle by using a liquid membrane module to selectively remove permanganate reducing compounds and multi-carbon alkyl iodides from the reaction stream. Instead of using multiple distillation columns, the liquid membrane extraction process directly extracts harmful impurities from the stream, achieving effective purification with simpler equipment. This extraction approach reduces device complexity while maintaining high purification effectiveness.
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 effectively reduces permanganate reducing compounds and their precursors from intermediate streams, improving acetic acid quality and reducing catalyst poisoning, while minimizing energy usage and equipment costs compared to previous methods.
Implementation Method 1
distilling the vapor overhead stream to yield a purified acetic acid product and a low boiling overhead vapor stream
Implementation Method 2
distilling the condensed light liquid phase in a single distillation column to form a second vapor phase stream overhead and a higher boiling liquid phase residuum
Implementation Method 3
condensing the second vapor phase stream and extracting the condensed stream with water to obtain an aqueous acetaldehyde stream comprising PRC
Data Source
AI summary
A process for the reduction and/or removal of permanganate reducing compounds formed by the carbonylation of methanol in the presence of a Group VIII metal carbonylation catalyst to produce acetic acid is disclosed. More specifically, a process for reducing and/or removing permanganate reducing compounds or their precursors from intermediate streams during the formation of acetic acid by said carbonylation processes is disclosed. In particular, a process in which a low boiling overhead vapor stream from a light ends column is subjected to a single distillation to obtain an overhead that is subjected to an extraction to selectively remove and/or reduce PRCs from the process is disclosed.