Ionic Liquid Purification of Terephthalic Acid
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Solution Overview
Problem
Current methods for purifying terephthalic acid, such as catalytic hydrogenation, are expensive and inefficient in removing impurities like 4-carboxybenzaldehyde, which co-crystallizes with terephthalic acid, requiring multiple costly purification steps.
Innovation Solution
A process using ionic liquids as solvents to contact crude terephthalic acid without oxidizing agents, reducing 4-carboxybenzaldehyde content by at least 30 wt% through separation methods like filtration or centrifugation, optionally with ionic solids or aqueous solvents, eliminating the need for expensive catalytic hydrogenation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If catalytic hydrogenation is used to purify terephthalic acid, then purity is improved, but cost and equipment investment increase significantly
Solution Approach 1:
The invention changes the chemical environment parameters by using ionic liquids with specific properties (high boiling point, non-volatile, tunable solubility) instead of conventional solvents. This parameter change enables selective dissolution of terephthalic acid while leaving 4-CBA impurities in the solid phase, achieving purification without expensive hydrogenation equipment
Solution Approach 2:
The ionic liquid acts as an intermediary substance that mediates the separation between terephthalic acid and 4-CBA impurities. By selecting ionic liquids with appropriate solubility characteristics, the process enables selective dissolution of the desired product while impurities remain undissolved, facilitating easy separation through filtration
2Manufacturing precision
If multiple purification steps are used to remove 4-CBA, then purity is improved, but process complexity and time increase
Solution Approach 1:
The invention extracts the purification function into a single selective dissolution step using ionic liquids. Instead of multiple sequential purification operations, the ionic liquid selectively dissolves terephthalic acid from the crude mixture, and a single filtration step removes the undissolved 4-CBA impurities, greatly simplifying the overall process
Solution Approach 2:
The purification process is segmented into two distinct phases: a selective dissolution phase where ionic liquid selectively dissolves terephthalic acid, and a separation phase where undissolved impurities are removed by filtration. This segmentation allows each step to be optimized independently and simplifies the overall process design
3Manufacturing precision
If conventional solvents are used for washing, then some impurities are removed, but 4-CBA co-crystallizes and remains in the product
Solution Approach 1:
The invention changes the solvent parameter from conventional volatile organic solvents to ionic liquids with fundamentally different properties: high boiling points, non-volatility, and tunable solubility. These parameter changes enable selective dissolution of terephthalic acid while 4-CBA remains insoluble, preventing co-crystallization and ensuring effective impurity removal
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 4-carboxybenzaldehyde levels to below 25 ppm, achieving polymer-grade purity without the need for costly hydrogenation processes, offering a more economical and efficient purification route.
Implementation Method 1
contacting the crude or contaminated terephthalic acid with a solvent in the absence of an oxidizing agent to form a purified product, wherein the solvent consists essentially of an ionic liquid
Implementation Method 2
separating the purified product from the solvent
Implementation Method 3
separating methods like filtration or centrifugation
Data Source
AI summary
Methods of purifying crude or contaminated terephthalic acid using ionic liquids are described. Crude or contaminated terephthalic acid is contacted with a solvent in the absence of an oxidizing agent to form a purified product having at least 30 wt % less 4-carboxybenzaldehyde compared to the crude or contaminated terephthalic acid. The solvent consists essentially of an ionic liquid, optionally an ionic solid or a material capable of forming an ionic salt, and optionally an aqueous solvent. The ionic liquid is formed in situ from at least one ionic liquid precursor.