Acetic Acid Distillation Column PRC Separation
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Solution Overview
Problem
Current processes for producing acetic acid through methanol carbonylation face challenges in efficiently separating permanganate reducing compounds (PRCs) like acetaldehyde and methyl iodide, leading to low-quality acetic acid due to energy-intensive distillation requirements and additional steps such as water extraction, which increase costs and complexity.
Innovation Solution
A process involving the distillation of a mixture containing methyl iodide and acetaldehyde, where water is allowed to rise to an upper position, forming an azeotropic mixture that separates into an organic phase rich in methyl iodide and an aqueous phase rich in acetaldehyde, allowing for efficient separation without additional steps or energy-intensive methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ordinary distillation means is used to separate acetaldehyde and methyl iodide, then the separation process is simple, but the separation efficiency is low due to close boiling points
Solution Approach 1:
Water is introduced as an intermediary substance to enable efficient separation. The process involves contacting the overhead mixture with water to form an aqueous phase that selectively absorbs acetaldehyde, while methyl iodide remains in the organic phase. This intermediary water facilitates separation despite the close boiling points of the target compounds.
Solution Approach 2:
The invention changes the physical-chemical parameters of the system by introducing water, which alters the distribution coefficients and solubility characteristics. This parameter change enables selective partitioning of acetaldehyde into the aqueous phase while maintaining methyl iodide in the organic phase, achieving efficient separation.
2Manufacturing precision
If water extraction is added to separate acetaldehyde from methyl iodide, then separation efficiency is improved, but process complexity and cost increase
Solution Approach 1:
The invention merges the distillation and extraction operations into a integrated process. The overhead from distillation is directly contacted with water in a combined separation step, eliminating the need for separate extraction equipment and reducing overall process complexity while maintaining high separation efficiency.
Solution Approach 2:
The invention extracts only the necessary component (acetaldehyde) from the overhead mixture using water, while leaving methyl iodide undisturbed in the organic phase. This selective extraction approach achieves efficient separation without requiring complex multi-step processes.
3Manufacturing precision
If water extraction is used to remove acetaldehyde, then acetaldehyde removal efficiency is improved, but methyl iodide is also extracted into aqueous phase causing loss
Solution Approach 1:
The invention applies local quality by creating distinct phases with different compositions. The aqueous phase selectively concentrates acetaldehyde while the organic phase retains methyl iodide. This localized separation ensures high acetaldehyde removal efficiency while preventing methyl iodide loss to the aqueous phase.
Solution Approach 2:
The invention converts the potential harm of water extraction (which could dissolve both compounds) into a benefit by exploiting the differential solubility. The water extraction process, which might seem to risk methyl iodide loss, actually benefits from the fact that methyl iodide has low water solubility, ensuring selective acetaldehyde removal without significant methyl iodide loss.
4Manufacturing precision
If distillation of water-containing mixture is performed, then large amount of energy is required due to water's large latent heat, but separation can be achieved
Solution Approach 1:
The invention extracts water from the distillation process by introducing it as a separate phase for extraction. Instead of distilling off water (which would require large energy input due to its high latent heat), water is added to create an aqueous phase that selectively absorbs acetaldehyde, eliminating the need for energy-intensive water distillation while achieving effective separation.
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 approach enables efficient separation of PRCs and methyl iodide with low energy consumption, reducing the need for water extraction and additional steps, thereby improving the quality and cost-effectiveness of acetic acid production.
Implementation Method 1
water is allowed to rise to an upper position than a feed port to form an azeotropic mixture
Implementation Method 2
the azeotropic mixture separates into an organic phase rich in methyl iodide and an aqueous phase rich in acetaldehyde
Implementation Method 3
distilling the first mixture to separate the first mixture into an upper stream and a lower stream
Data Source
AI summary
A process for separating or removing permanganate reducing compounds (PRC's) from a first mixture containing at least one PRC, methyl iodide, and water comprises the steps of: feeding the first mixture to a feed port of a distillation column, and distilling and separating the first mixture into an upper stream and a lower stream, wherein the distillation of the first mixture forms a second mixture at an upper position than the feed port, and the process further comprises the steps of: withdrawing the second mixture as the upper stream, and withdrawing the lower stream from a lower position than the feed port.