Hexyl Ester Synthesis Removing Rhodamine B Impurities
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Solution Overview
Problem
The existing processes for manufacturing 2-(4′-diethylamino-2′-hydroxybenzoyl)benzoic acid hexyl ester suffer from the formation of Rhodamine B type dyes as impurities, leading to undesired discoloration and requiring additional purification steps, which are inefficient and costly.
Innovation Solution
A process involving the reaction of phthalic acid anhydride with 3-N,N-diethylaminophenol, followed by esterification with n-hexanol, pH adjustment, and adsorption over multiple adsorbents such as activated carbon and silica gel, effectively reduces Rhodamine B content to less than 5 ppm, minimizing color impurities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional purification steps are used to remove Rhodamine B type dyes, then the product can be purified to less than 5 ppm rhodamine content, but the process becomes more complex and less efficient
Solution Approach 1:
The patent extracts and removes Rhodamine B type dye impurities from the reaction mixture through selective adsorption onto activated carbon, separating the harmful impurity from the desired product and achieving high purification levels
Solution Approach 2:
The patent changes the purification approach by adjusting pH parameters during the extraction process and utilizing the different adsorption characteristics of activated carbon at different pH levels to selectively remove rhodamine dyes while preserving the product
2Manufacturing precision
If additional purification steps are added to reduce color impurities, then the Gardner value and Yellowness Index improve, but the manufacturing time and cost increase
Solution Approach 1:
The patent performs preliminary purification during the reaction process itself by incorporating activated carbon adsorption into the synthesis workflow, preventing color impurities from accumulating rather than correcting them afterward
Solution Approach 2:
The patent merges the purification function with the existing reaction process by combining the esterification reaction step with the activated carbon adsorption step, allowing both product formation and impurity removal to occur simultaneously in an integrated process
3Manufacturing precision
If multiple adsorbents are used in sequence, then the rhodamine content reduces to less than 1 ppm, but the device complexity and operational difficulty increase
Solution Approach 1:
The patent segments the adsorption process into distinct stages using different adsorbents (activated carbon followed by silica gel), where each stage targets specific impurity ranges, achieving progressive purification from conventional levels to ultra-low levels
Solution Approach 2:
The patent uses activated carbon as an intermediary adsorbent that selectively binds to Rhodamine B type dyes through their chromophore structures, acting as a mediator that transfers impurity removal responsibility from the main reaction system to a dedicated purification component
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
The process achieves a significant reduction in Rhodamine B impurities, resulting in a product with a Gardner value of 8.2 or less, Yellowness Index of less than 89, and Hess-Ives value of less than 19, thereby eliminating reddish and brownish discoloration, and improving the overall efficiency and economy of the manufacturing process.
Implementation Method 1
adsorption over at least two different adsorbents
Implementation Method 2
adsorption over an adsorbent
Implementation Method 3
extracting at least once with an aqueous phase
Implementation Method 4
reacting phthalic acid anhydride with 3-N,N-diethylaminophenol to obtain 2-(4'-diethylamino-2'-hydroxybenzoyl)benzoic acid
Implementation Method 5
reacting the 2-(4'-diethylamino-2'-hydroxybenzoyl)benzoic acid obtained in step a) with n-hexanol to obtain 2-(4'-diethylamino-2'-hydroxybenzoyl)benzoic acid hexyl ester
Data Source
AI summary
The present invention relates to a process of manufacturing 2-(4′-diethylamino-2′-hydroxybenzoyl)benzoic acid hexyl ester having a Gardner value of 8.2 or less comprising adjusting the reaction mixture obtained by reacting 2-(4′-diethylamino-2′-hydroxybenzoyl)benzoic acid with n-hexanol to a pH of more than 7 followed by extracting at least once with an aqueous phase and adsorbing the dissolved 2-(4′-diethylamino-2′-hydroxybenzoyl)benzoic acid hexyl ester over at least two different adsorbents.