Hydrogen Iodide Removal in Acetic Acid Carbonylation
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Solution Overview
Problem
Conventional processes for producing acetic acid through methanol carbonylation fail to effectively separate and remove hydrogen iodide, which acts as a corrosion agent and poses environmental and cost-related concerns.
Innovation Solution
The process involves carbonylating methanol, dimethyl ether, or methyl acetate in a reactor with a metal catalyst and methyl iodide, followed by flashing the crude acetic acid product to separate hydrogen iodide, and using an absorber tower with absorbents like acetic acid or methanol to absorb and remove hydrogen iodide from the vapor streams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional carbonylation processes are used to produce acetic acid, then acetic acid can be synthesized efficiently, but hydrogen iodide accumulates in the reaction system causing corrosion and metallurgical problems
Solution Approach 1:
The patent extracts and removes hydrogen iodide from the carbonylation reaction system through a dedicated removal step. The process involves separating HI from the reaction mixture, typically through distillation or extraction techniques, thereby eliminating the corrosive agent while maintaining continuous acetic acid production. This resolves the contradiction by removing the harmful substance without stopping the productive carbonylation reaction.
Solution Approach 2:
The patent introduces an intermediary substance or process step that facilitates the removal of hydrogen iodide. This may involve using a scavenger compound or intermediate reaction step that converts HI into a less harmful form or enables its selective separation. The intermediary mechanism allows the system to handle the corrosive byproduct without compromising the main acetic acid synthesis process.
2Manufacturing precision
If conventional separation processes are applied to crude acetic acid, then general purification can be achieved, but hydrogen iodide specifically cannot be effectively separated
Solution Approach 1:
The patent applies local quality by implementing a specialized separation step specifically targeted at hydrogen iodide removal, rather than using a general-purpose purification process. This may involve a dedicated distillation column section, selective extraction stage, or catalytic conversion step that is specifically designed for HI separation. The local quality approach ensures that the unique properties of hydrogen iodide are exploited for its selective removal while the rest of the acetic acid purification process continues as before.
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 method effectively reduces hydrogen iodide levels in process streams, minimizing corrosion and environmental issues while improving catalyst stability and acetic acid purification.
Implementation Method 1
carbonylating, in a reactor, at least one of methanol, dimethyl ether, and methyl acetate in a reaction medium comprising a metal catalyst, methyl iodide, an iodide salt
Implementation Method 2
contacting the absorber tower feed with a first absorbent comprising acetic acid to absorb methyl iodide and to form a first absorber return stream
Implementation Method 3
flashing the crude acetic acid product, with or without heat, to form a first vapor stream comprising acetic acid and methyl iodide
Data Source
AI summary
Processes for producing acetic acid wherein at least one process vent stream is treated in an absorber column that utilizes a scrubber solvent, e.g., acetic acid, methanol, and/or methyl acetate to remove hydrogen iodide therefrom.