Acetic Acid Aldehyde Removal via Acetal Extraction
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Solution Overview
Problem
The acetic acid production process faces challenges in reducing aldehyde impurities, particularly due to high water concentrations which lead to corrosive conditions and iodide impurities, and existing methods for removing aldehydes are either costly or pose safety concerns with the use of explosive free radical initiators.
Innovation Solution
A method involving the reaction of methanol and carbon monoxide in the presence of a carbonylation catalyst, such as rhodium or iridium, with a catalyst stabilizer like triphenylphosphine oxide, and the use of an alcohol to convert aldehydes into acetals, which are then separated and recycled, reducing aldehyde content in the acetic acid product.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If water concentration is lowered in the methanol carbonylation process, then corrosiveness and iodide impurities are reduced, but aldehyde formation increases
Solution Approach 1:
The patent extracts and removes aldehyde impurities from the acetic acid product stream using extraction distillation with water as the extractive solvent. This allows the process to operate with lower water concentration (reducing corrosiveness) while still achieving low aldehyde levels in the final product through targeted removal.
Solution Approach 2:
The patent employs a composite approach combining extraction distillation with a specific solvent system (water as extractive solvent) to simultaneously address multiple problems: it removes aldehydes from the organic phase while allowing the carbonylation process to run at optimized low water concentrations, thus reducing both corrosiveness and aldehyde content.
2Object-generated harmful factors
If free radical initiators are used to remove aldehydes, then aldehyde impurities are reduced, but safety concerns and explosion risks increase
Solution Approach 1:
The patent uses water as an intermediary extractive solvent in the extraction distillation process. This physical separation method using a mediator substance (water) replaces the need for chemical reactions with free radical initiators, thereby removing aldehydes safely without explosion risks while still achieving the desired reduction in aldehyde impurities.
3Stability of the object's composition
If lithium iodide is added to the rhodium catalyst system, then catalyst stability is improved, but stress crack corrosion and iodide impurities increase
Solution Approach 1:
The patent removes iodide impurities (including those from lithium iodide) from the system through extraction distillation using water. This allows the use of lithium iodide for catalyst stabilization while selectively extracting the harmful iodide species into the aqueous phase, preventing stress crack corrosion in the reactor vessels.
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 effectively minimizes aldehyde impurities in the acetic acid product, reduces water usage, and avoids safety concerns associated with free radical initiators, resulting in a more efficient and safer production process with lower aldehyde levels.
Implementation Method 1
reacting methanol and carbon monoxide in the presence of a carbonylation catalyst
Implementation Method 2
use of an alcohol to convert aldehydes into acetals
Data Source
AI summary
A method for reducing aldehydes in an acetic acid production process is disclosed. The acetic acid is produced by reacting methanol and carbon monoxide in the presence of a carbonylation catalyst. The method comprises reacting an aldehyde-containing stream with an alcohol to form an acetal-containing stream. An acetal-enriched stream is separated from the acetal-containing stream and then hydrolyzed to form a hydrolysis mixture comprising the alcohol and the aldehydes. The alcohol is isolated from the hydrolysis mixture and used to react with the aldehyde-containing stream to form the acetal-containing stream. The invention reduces aldehydes in the acetic acid produced.