Acetic Acid Purification via Liquid-Liquid Extraction
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Solution Overview
Problem
Conventional processes for producing acetic acid through methanol carbonylation fail to effectively remove permanganate reducing compounds (PRCs) and alkyl halides, such as methyl iodide, leading to impurities that affect the quality and efficiency of the acetic acid production, increasing costs and requiring additional treatments.
Innovation Solution
A process involving multiple distillation columns and liquid-liquid extraction with an extractive solvent, using water or other agents to separate and recover PRCs and alkyl halides, achieving a purified PRC stream with reduced water content and minimized alkyl halide presence, thereby improving the acetic acid production efficiency and reducing treatment costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional purification techniques (oxidizers, ozone, water, methanol, activated-carbon, amines) are used to remove impurities from acetic acid, then impurity removal is achieved, but process cost increases and additional impurities may be formed
Solution Approach 1:
The patent extracts and removes specific harmful impurities (permanganate reducing compounds and alkyl halides) from the acetic acid production process using a dedicated extraction unit. This targeted extraction approach eliminates the need for conventional purification techniques involving oxidizers, ozone, and other treatments, thereby reducing process costs while maintaining high acetic acid purity.
2Manufacturing precision
If distillation of treated acetic acid product is performed to remove impurities, then impurity removal is achieved, but additional impurities are formed
Solution Approach 1:
The patent applies preliminary action by removing permanganate reducing compounds and alkyl halides from the reaction mixture before the distillation step. The extraction unit selectively removes these impurities from the crude acetic acid stream prior to distillation, preventing their concentration and transformation into additional impurities during the distillation process.
3Loss of substance
If halogen promoter recovery processes are used, then halogen promoter recovery is achieved, but other impurities (PRCs) are not removed
Solution Approach 1:
The patent implements a multi-functional extraction unit that simultaneously performs two functions: recovering halogen promoters (methyl iodide) and removing permanganate reducing compounds from the acetic acid production process. This single unit achieves both halogen promoter recovery and PRC removal, eliminating the need for separate treatment processes and thereby improving permanganate time while maintaining economic efficiency.
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 recovers PRCs and alkyl halides, enhancing the quality of acetic acid production by reducing impurities, improving the permanganate time, and allowing for the recycling of halogen promoters, thus lowering operational costs and increasing efficiency.
Implementation Method 1
separating the crude acetic acid composition in a light ends column into an overhead stream and an acetic acid product stream
Implementation Method 2
separating a portion of the overhead stream using a first distillation columns to obtain a stream enriched in the at least one PRC
Implementation Method 3
separating a portion of the enriched stream in a second distillation column to obtain a distillate comprising methyl iodide and a residue comprising the at least one PRC
Implementation Method 4
liquid-liquid extraction with an extractive solvent, using water or other agents to separate and recover PRCs and alkyl halides
Data Source
AI summary
This invention relates to processes for producing acetic acid and, in particular, to improved processes for recovering permanganate reducing compounds formed during the carbonylation of methanol in the presence of a carbonylation catalyst to produce acetic acid. Alkyl halides are removed or reduced from the recovered permanganate reducing compounds.