Acetic Acid Purification via Water Extraction of PRCs
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Solution Overview
Problem
Current processes for producing acetic acid through carbonylation of methanol with Group VIII metal catalysts face challenges in efficiently removing permanganate reducing compounds (PRCs) and alkyl iodides, which affect the quality of acetic acid and increase production costs due to the need for additional purification steps and energy consumption.
Innovation Solution
The process involves separating crude acetic acid into a PRC-enriched stream and an acetic acid stream, followed by phase separation and distillation to remove PRCs, with extraction using a medium like water or dimethyl ether to reduce methyl iodide concentration, and directing return streams to optimize water control and reduce reactor load, thereby enhancing production efficiency and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional purification steps are used to remove PRCs and alkyl iodides, then acetic acid quality is improved, but production costs and energy consumption increase
Solution Approach 1:
The patent applies preliminary action by removing PRCs and alkyl iodides during the carbonylation reaction process itself through in-situ reaction with water, rather than relying on subsequent purification steps. Water is introduced to react with and remove these impurities at the source, preventing their accumulation and eliminating the need for energy-intensive post-reaction purification operations.
Solution Approach 2:
The patent converts the harmful effect of PRCs and alkyl iodides into a beneficial process by utilizing water to react with these impurities. The water that would otherwise be a simple solvent becomes an active participant that transforms harmful substances into removable by-products, turning a purification problem into a controlled reaction process.
2Manufacturing precision
If additional purification steps are added to remove PRCs and alkyl iodides, then acetic acid quality is improved, but production costs increase
Solution Approach 1:
The patent merges the purification function with the main carbonylation reaction process. By introducing water into the reaction system, the removal of PRCs and alkyl iodides is combined with the primary production reaction, eliminating the need for separate purification equipment and steps. This integration simplifies the overall process architecture while maintaining product quality.
Solution Approach 2:
The patent applies self-service by enabling the reaction system to remove its own impurities through the in-situ reaction of water with PRCs and alkyl iodides. The system becomes self-cleaning, where the carbonylation process itself generates the conditions for impurity removal, eliminating the need for external purification systems.
3Productivity
If water concentration is increased to remove PRCs, then PRC removal efficiency is improved, but reactor load and production costs increase
Solution Approach 1:
The patent applies parameter changes by optimizing the water concentration parameter to achieve effective PRC removal without excessive water addition. By carefully controlling water levels and using it reactively rather than in large excess, the system achieves high PRC removal efficiency while minimizing the increase in total substance quantity and associated costs.
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 reduces the load on reactors and separation systems, decreases energy usage, and improves acetic acid quality by effectively removing PRCs and alkyl iodides, leading to increased production capability and reduced costs.
Implementation Method 1
treating the acetic acid product stream with water or another extraction medium to remove the PRCs and/or alkyl iodides
Implementation Method 2
treating the acetic acid product stream with water or another extraction medium to remove the PRCs and/or alkyl iodides
Data Source
AI summary
Processes for the reduction and/or removal of permanganate reducing compounds (PRC'S) formed by the carbonylation of methanol in the presence of a Group VIII metal carbonylation catalyst to produce acetic acid are disclosed. More specifically, processes for reducing and/or removing PRC's or their precursors from intermediate streams during the formation of acetic acid by said carbonylation processes are disclosed. In particular, processes in which a low boiling overhead vapor stream from a light ends column is subjected to a distillation to obtain an overhead that is subjected to an extraction to selectively remove and/or reduce PRC's from the process is disclosed. The processes include steps of recycling one or more return streams derived from the distillation step and/or the extraction step to a light ends column and/or a drying column in order to improve water control in the overall reaction system.