Purifying Biphenyldicarboxylic Acid via Selective Hydrogenation
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Solution Overview
Problem
Existing methods for producing biphenyldicarboxylic acids through dimethylbiphenyl compounds result in by-products like formylbiphenylcarboxylic acid, which hinder polymer growth and color quality, and conventional purification techniques are ineffective due to the low volatility and solid solution formation of these acids.
Innovation Solution
A process involving the combination of crude biphenyldicarboxylic acid with a liquid, followed by hydrogenation in the presence of a catalyst, selectively reduces formylbiphenylcarboxylic acid to hydroxymethyl or methyl derivatives, allowing for easy separation of purified biphenyldicarboxylic acid through crystallization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If oxidation of DMBP compounds is used to produce BPDAs, then the desired diacids are produced, but by-products such as formylbiphenylcarboxylic acid and fluorenones are also produced that reduce polymer quality and color
Solution Approach 1:
The patent applies preliminary action by performing hydrogenation of the crude oxidation product before final purification. The formylbiphenylcarboxylic acid by-products are converted to their corresponding alcohols (hydroxymethylbiphenylcarboxylic acid) through catalytic hydrogenation, which prevents these by-products from forming colors during subsequent polymerization processes. This preliminary chemical modification eliminates the harmful effect before the main purification step.
Solution Approach 2:
The patent converts the harmful by-products (formylbiphenylcarboxylic acid and fluorenones) into beneficial forms through selective hydrogenation. The aldehyde groups are reduced to alcohol groups, transforming color-forming impurities into non-color-forming compounds that can be easily separated. This principle transforms the harmful oxidation by-products into removable intermediates that do not adversely affect the final polymer product.
2Manufacturing precision
If typical physical separation techniques are used to purify crude BPDA, then separation is attempted, but the low volatility and solid solution formation of BPDA make these techniques ineffective
Solution Approach 1:
The patent applies parameter changes by modifying the chemical structure of the impurities through hydrogenation rather than attempting to separate BPDA from its by-products using physical properties. By changing the functional groups of the by-products (from aldehyde to alcohol), the patent creates compounds with different solubility and crystallization behaviors, enabling effective separation through conventional crystallization techniques that would otherwise be ineffective due to solid solution formation.
Solution Approach 2:
The patent introduces an intermediary chemical transformation step (catalytic hydrogenation) that converts the difficult-to-separate by-products into intermediate compounds (alcohols) that can be easily separated from the desired diacid product. This intermediary step acts as a bridge between the problematic crude oxidation product and the easily separatable components, allowing standard purification techniques to work effectively.
3Productivity
If by-products are not removed from crude BPDA, then polymerization can proceed, but chain termination occurs and color quality deteriorates
Solution Approach 1:
The patent performs preliminary hydrogenation of the crude BPDA to convert color-forming by-products into non-color-forming alcohols before polymerization. This preliminary action ensures that when polymerization subsequently occurs, the by-products present do not cause chain termination or color deterioration, thereby maintaining both high productivity and reliable polymer quality.
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 impurities to less than 200 ppm, preventing chain termination and color issues, and enables the production of high-purity biphenyldicarboxylic acid suitable for polymerization and polyester production.
Implementation Method 1
contacting the mixture with hydrogen in the presence of a hydrogenation catalyst. By these steps, the FBCA and color-forming impurities in the crude product can be selectively reduced
Implementation Method 2
contacting the mixture with hydrogen in the presence of a hydrogenation catalyst
Implementation Method 3
separating at least a portion of the biphenyldicarboxylic acid from the hydrogenation effluent
Data Source
AI summary
Processes are described for purifying a biphenyldicarboxylic acid product containing one or more impurities, particularly at least formylbiphenylcarboxylic acid. In the processes, a mixture comprising the biphenyldicarboxylic acid product is contacted with hydrogen in the presence of a hydrogenation catalyst under conditions to selectively reduce at least part of the formylbiphenylcarboxylic acid to produce a hydrogenation effluent comprising (i) hydroxymethylbiphenylcarboxylic acid and/or methylbiphenylcarboxylic acid, and (ii) biphenylcarboxylic acid. At least a portion of the biphenyldicarboxylic acid is then separated from the hydrogenation effluent. Advantageously, a polyester product may be produced from the separated biphenyldicarboxylic acid.