Acid Catalyst Recovery via Tertiary Amine Extraction
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Solution Overview
Problem
The recovery of strong acid catalysts from aqueous glycolic acid mixtures is challenging due to strong hydrogen-bonding and polar interactions, making it difficult to separate the acid catalyst from the glycolic acid product, and existing methods do not provide for direct recycling of the catalyst to the hydrocarboxylation reaction.
Innovation Solution
A process involving the extraction of an aqueous glycolic acid mixture using a solvent comprising a tertiary amine, an onium carboxylate compound, and a modifier, followed by separation and back-extraction into an aqueous formaldehyde solution to recycle the acid catalyst, allowing for the recovery and reuse in the hydrocarboxylation reaction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional extraction methods are used to separate acid catalyst from glycolic acid, then the acid catalyst can be removed from the product mixture, but significant quantities of glycolic acid are co-extracted with the catalyst
Solution Approach 1:
The patent introduces an intermediary extraction solvent system comprising a tertiary amine and a carboxylic acid modifier that selectively interacts with the acid catalyst. This intermediary medium enables selective transfer of the catalyst from the aqueous glycolic acid phase without co-transferring significant amounts of glycolic acid, thus resolving the contradiction between catalyst separation purity and product loss.
Solution Approach 2:
The patent modifies the extraction process by changing the chemical parameters of the extraction solvent system. By using a specific combination of tertiary amine and carboxylic acid modifier with controlled ratios, the extraction system achieves selective affinity for the acid catalyst over glycolic acid, enabling high-purity catalyst recovery with minimal product loss.
2Ease of operation
If the acid catalyst is converted to an insoluble salt for separation, then the catalyst can be easily separated from the glycolic acid product, but the catalyst cannot be directly recycled to the hydrocarboxylation reactor
Solution Approach 1:
The extraction solvent system acts as an intermediary that temporarily holds the acid catalyst in a soluble, transferable form. This intermediary medium enables both easy separation from the product phase and subsequent back-extraction/recycling to the reactor, combining the ease of separation with the versatility of recyclability.
Solution Approach 2:
The patent establishes a continuous cycle where the acid catalyst is extracted, separated, and then back-extracted to the aqueous formaldehyde feed stream for continuous recycling. This continuous process maintains the catalyst in an active, reusable state throughout the operation, eliminating the need for conversion to insoluble salts and enabling direct recycling.
3Productivity
If strong acid catalysts are used for hydrocarboxylation, then the reaction efficiency is improved, but the separation and recycle of the catalyst from the glycolic acid product becomes difficult
Solution Approach 1:
The tertiary amine-carboxylic acid modifier extraction system serves as a specialized intermediary that is particularly effective for separating strong acid catalysts. The system's chemical design creates strong interactions with the acid catalyst while maintaining phase separation from glycolic acid, enabling efficient recovery without excessive 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 process efficiently separates the acid catalyst from glycolic acid without co-extracting significant quantities of glycolic acid, enabling its direct recycling and reuse in the hydrocarboxylation reaction, thereby improving process efficiency and economic viability.
Implementation Method 1
extracting an aqueous glycolic acid mixture... with an extraction solvent... to form an aqueous raffinate phase comprising a major amount of the glycolic acid... and an organic extract phase comprising a major amount of the acid catalyst
Implementation Method 2
extracting the organic extract phase... with an aqueous formaldehyde solution to form an aqueous formaldehyde extract comprising a major amount of the acid catalyst
Data Source
AI summary
Disclosed is a process for the extractive recovery of an acid catalyst from an aqueous mixture of glycolic acid with an extraction solvent comprising a tertiary amine or an onium carboxylate compound, a modifier, and a diluent. The acid catalyst, which can comprise strong acids such as sulfuric acid, alkyl sulfonic acids, and fluoroalkyl sulfonic acids, can be recovered by back extraction with aqueous formaldehyde and recycled to a process for the preparation of glycolic acid by the acid-catalyzed carbonylation of formaldehyde.