Acetic Acid Decanter Phase Separation via Alkane Promoter
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Solution Overview
Problem
The existing processes for producing acetic acid by carbonylating methanol face challenges in efficient phase separation under low water-high acid conditions, leading to incomplete separation in decanters, which affects the recycling of methyl iodide, increases energy consumption, and results in the formation of undesired by-products, making the process costly and inefficient.
Innovation Solution
The process involves carbonylating methanol in the presence of a catalyst to form a reaction mixture, followed by separating the vapor stream into a product stream and an overhead stream, condensing the overhead stream to form a liquid mixture with a water content of at most 20% by weight, and partitioning it with an alkane content of 0.1 to 15% by weight to achieve efficient phase separation into an aqueous and organic phase, thereby stabilizing the decanter operation and simplifying the removal of by-products.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the amount of water in the reaction mixture is reduced to increase catalyst stability and reduce by-product formation, then catalyst stability is improved, but phase separation in the decanter becomes incomplete
Solution Approach 1:
The patent introduces a phase separation promoter (such as methyl tert-butyl ether, dimethyl carbonate, or dialkyl sulfates) as an intermediary substance to facilitate phase separation in the decanter. This promoter acts as a mediator between the organic and aqueous phases, reducing mutual solubility and enabling complete separation even under low-water conditions where catalyst stability is prioritized. The promoter concentration is controlled at 0.1-10 wt% of the overhead stream to achieve effective separation without interfering with catalyst performance.
2Productivity
If the concentration of acetic acid in the overhead stream is increased to improve production efficiency, then productivity is improved, but phase separation becomes more difficult
Solution Approach 1:
The phase separation promoter serves as an intermediary that enables the system to handle high acetic acid concentrations in the overhead stream (up to 80-95 wt%) without compromising separation ease. The promoter reduces the solubility of acetic acid in the organic phase and water in the aqueous phase, creating a clearer phase boundary that facilitates separation even when acetic acid concentration is high for improved productivity.
Solution Approach 2:
The patent changes the chemical composition parameters of the overhead stream by introducing the phase separation promoter, which alters the phase behavior and interfacial tension between organic and aqueous phases. This parameter change enables efficient separation of high-concentration acetic acid streams that would otherwise be difficult to separate, maintaining ease of operation while improving productivity.
3Productivity
If the residence time in the decanter is reduced to increase process throughput, then productivity is improved, but separation completeness deteriorates
Solution Approach 1:
The phase separation promoter acts as a kinetic catalyst for phase separation, dramatically accelerating the separation process. With the promoter present, complete phase separation is achieved in seconds rather than minutes or hours, enabling the decanter to operate at very high throughput while maintaining complete separation. The promoter reduces the activation energy for phase separation, allowing rapid separation that meets both productivity and completeness requirements.
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 and stable phase separation in the decanter, reducing the residence time and energy consumption, improving the quality of acetic acid production, and maintaining a stable water balance in the reactor, thus enhancing the overall efficiency and reliability of the acetic acid production process.
Implementation Method 1
condensing the overhead stream to form a liquid mixture
Implementation Method 2
partitioning it with an alkane content of 0.1 to 15% by weight to achieve efficient phase separation into an aqueous and organic phase
Data Source
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AI summary
The phase separation in the decanter of a process for producing acetic acid by carbonylating methanol in the presence of a catalyst under low water-high acid conditions is improved by forming a liquid mixture (D) which has a water content of at most 20% by weight, based on the weight of the liquid mixture, and a weight ratio of acetic acid to water of at least 1 :1, and partitioning the liquid mixture by providing for an alkane(s) content of D of from 0.1 to 15% by weight, based on the weight of D, to obtain a light, aqueous phase and a heavy, organic phase.