Two-Stage Absorption for Acetic Acid Production
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing methods for producing acetic acid, such as the methanol carbonylation process, face challenges in efficiently separating and recovering methyl iodide and hydrogen iodide, as well as causing corrosion in distillation columns due to the close boiling points of the solvents used and the corrosive nature of acetic acid.
Innovation Solution
A method involving two absorption steps using different solvents with varying compositions, where the first absorbent includes C2 or higher alcohols, esters, ethers, ketones, water, and basic aqueous solutions, and the second absorbent includes C2 or higher alcohols, esters, ethers, ketones, water, and acetic acid, to efficiently separate and recover methyl iodide and hydrogen iodide, reducing corrosion and improving recovery efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If acetic acid is used as the absorbing solvent, then the absorption of hydrogen iodide is effective, but the distillation column interior is corroded during distillation
Solution Approach 1:
The patent introduces a two-stage absorption system where the first stage uses acetic acid to effectively absorb hydrogen iodide, and the second stage uses water to absorb hydrogen iodide from the first gas stream. This intermediary water absorption step prevents corrosive acetic acid-hydrogen iodide mixture from entering the distillation column, thereby protecting the column interior while maintaining effective hydrogen iodide removal
Solution Approach 2:
The absorption process is divided into two separate stages: first absorption (acetic acid) and second absorption (water). This segmentation allows each absorbent to perform its optimal function - acetic acid for initial hydrogen iodide capture and water for final cleanup - while preventing the corrosive effects from reaching the distillation column
2Ease of manufacture
If methanol or methyl acetate is used as the absorbing solvent, then the absorption process is simple, but the separation efficiency by distillation is poor due to small boiling point difference
Solution Approach 1:
The patent changes the key parameter of solvent selection from low-boiling solvents (methanol, methyl acetate) to high-boiling solvents (acetic acid, water). This parameter change creates a large boiling point difference with methyl iodide, enabling efficient separation by distillation while maintaining process simplicity through the two-stage absorption approach
3Device complexity
If a single absorption step is used, then the process is simple, but the separate recovery of hydrogen iodide and methyl iodide is insufficient
Solution Approach 1:
The absorption process is segmented into two distinct stages: first absorption using acetic acid and second absorption using water. This segmentation enables separate recovery streams - the first solution contains absorbed hydrogen iodide and the second solution contains absorbed methyl iodide - achieving precise separation and recovery of both components while maintaining reasonable process complexity
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 and recovery of methyl iodide and hydrogen iodide, reducing corrosion in distillation columns and improving the overall recovery efficiency, allowing for the effective reuse of methyl iodide and minimizing environmental impact.
Implementation Method 1
the first absorbent to absorb hydrogen iodide from the offgas
Implementation Method 2
the second absorbent to absorb methyl iodide from the first gas
Implementation Method 3
the first solution is separated, by distillation, into hydrogen iodide and the first absorbent
Implementation Method 4
the second solution is separated, by distillation, into methyl iodide and the second absorbent
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Provided is an acetic acid production method that enables, in a scrubbing system, efficient separation and obtaining of methyl iodide and an absorbing solvent; restrainment of corrosion of the interior of a distillation column; efficient separation between and recovery of hydrogen iodide and methyl iodide; or sufficient recovery of hydrogen iodide. The acetic acid production method according to the present invention includes a first absorption step and a second absorption step. In the first absorption step, an offgas is brought into contact with a first absorbent to allow the first absorbent to absorb an iodine compound from the offgas, to give a first gas, where the first absorbent includes at least one of C2 or higher alcohols, esters of C3 or higher carboxylic acids, esters between carboxylic acids and C2 or higher alcohols, ethers, ketones, water, and basic aqueous solutions. In the second absorption step, the first gas is brought into contact with a second absorbent to allow the second absorbent to absorb an iodine compound from the first gas, where the second absorbent includes at least one of C2 or higher alcohols, esters of C3 or higher carboxylic acids, ethers, esters between carboxylic acids and C2 or higher alcohols, ketones, water, basic aqueous solutions, and acetic acid and differs in composition from the first absorbent.