Propionic Acid Absorbent for Methyl Iodide Separation
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Solution Overview
Problem
The existing acetic acid production methods using acetic acid, methanol, or methyl acetate as absorbing solvents in the methanol carbonylation process face inefficiencies in separation due to small differences in boiling points, leading to increased energy consumption and poor energy savings during distillation.
Innovation Solution
Employing an organic acid with a higher boiling point than acetic acid as the absorbing solvent in the absorption step allows for efficient separation of methyl iodide, reducing the steam required in the distillation process by utilizing a solvent with a larger boiling point difference, such as propionic acid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If acetic acid, methanol, or methyl acetate is used as the absorbing solvent, then the absorption step can be performed, but the separation efficiency is improved while the steam consumption increases due to small boiling point difference
Solution Approach 1:
The patent changes the boiling point parameter of the absorbing solvent by selecting propionic acid (boiling point 141°C) instead of acetic acid (boiling point 118°C), methanol (boiling point 65°C), or methyl acetate (boiling point 77°C). This parameter change creates a larger boiling point difference with methyl iodide, enabling efficient separation at lower reflux ratios and reduced steam consumption.
2Manufacturing precision
If a higher reflux ratio is used in distillation, then the separation efficiency improves, but the steam amount required increases
Solution Approach 1:
The patent changes the physical parameter (boiling point) of the absorbent to propionic acid, which has a higher boiling point than the conventional solvents. This creates a larger temperature gap with methyl iodide, allowing the distillation column to achieve effective separation at lower reflux ratios, thereby reducing steam consumption while maintaining separation 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
This approach enables energy-saving and efficient separation of methyl iodide, reducing the reflux ratio needed in distillation and minimizing steam usage, thereby improving the overall energy efficiency of the acetic acid production process.
Implementation Method 1
the fed offgas is brought in contact with an absorbent including an organic acid having a higher boiling point as compared with acetic acid to allow the absorbent to absorb an iodine compound from the offgas
Implementation Method 2
the resulting solution after absorption of such useful components is then fed to a distillation column and is separated, by distillation, into the useful components and the absorbing solvent (absorbent)
Data Source
AI summary
Provided is an acetic acid production method including an absorption step that enables efficient and energy-saving separation of methyl iodide in a downstream step, when provided, of separating methyl iodide from a solution after the absorption of methyl iodide. The acetic acid production method according to the present invention includes an absorption step in an acetic acid production process. In the absorption step, at least a portion of offgases formed in the process is fed to an absorption column, is brought into contact with an absorbent including an organic acid having a higher boiling point as compared with acetic acid to allow the absorbent to absorb an iodine compound from the offgas, and a gas having a lower iodine compound concentration as compared with the offgas, and a solution containing the absorbent and the iodine compound are thereby to be separated.