Hydroxycarboxylic Acid Purification via Crystallization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for purifying hydroxycarboxylic acids, such as glycolic acid, face challenges in achieving high yields and purity due to their tendency to undergo polycondensation under heating, making distillation inefficient and crystallization from aqueous solutions prone to low recovery yields and impurity issues.
Innovation Solution
A process involving crystallization of hydroxycarboxylic acid aqueous solutions, followed by separation and washing with a hydroxycarboxylic acid aqueous solution, reduces thermal load and effectively removes impurities like glycolic acid dimer, allowing for high-purity hydroxycarboxylic acid production, which is then used for producing cyclic esters and subsequently polyhydroxycarboxylic acids through ring-opening polymerization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If distillation is used to purify hydroxycarboxylic acid, then purity can be improved, but the hydroxycarboxylic acid undergoes polycondensation under heating causing loss of substance and reduced yield
Solution Approach 1:
The patent changes the purification parameter from thermal-based (distillation) to non-thermal based (crystallization). By using crystallization from aqueous solution at controlled temperatures, the process achieves high purity without the heating that causes polycondensation, thus resolving the contradiction between purity improvement and yield loss.
Solution Approach 2:
The patent replaces the thermal-mechanical distillation system with a crystallization system based on solubility differences. This substitution eliminates the need for high-temperature heating, preventing polycondensation while achieving effective separation of impurities through controlled crystallization and filtration.
2Temperature
If crystallization from aqueous solution is used to purify hydroxycarboxylic acid, then thermal load is reduced, but recovery yield becomes extremely low due to lack of concentration step
Solution Approach 1:
The patent implements a continuous crystallization process where the aqueous solution is continuously cooled to precipitate crystals, separated by filtration, and the mother liquor is continuously recycled. This continuous operation maintains high recovery yield while keeping thermal load low, as the process operates at controlled temperatures without requiring extensive concentration steps.
Solution Approach 2:
The patent recovers and recycles the mother liquor from crystallization to continue the purification process. By recovering the solution containing dissolved hydroxycarboxylic acid and impurities, the process maximizes recovery yield while maintaining low thermal load throughout the continuous operation.
3Manufacturing precision
If high concentration aqueous solution is used for crystallization, then purification efficiency is improved, but polycondensation of hydroxycarboxylic acid becomes liable to occur
Solution Approach 1:
The patent employs dynamic control of crystallization conditions, including controlled cooling rates, agitation speeds, and residence times. By dynamically adjusting these parameters, the process achieves efficient purification at lower concentrations while preventing polycondensation through optimized kinetic control, resolving the contradiction between purification efficiency and compositional stability.
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 achieves an industrially feasible high yield of high-purity hydroxycarboxylic acids with minimal thermal load, enhancing the production efficiency and purity suitable for polyhydroxycarboxylic acid synthesis, while maintaining a high recovery yield.
Implementation Method 1
a crystallization step of subjecting a hydroxycarboxylic acid aqueous solution to crystallization for purification
Implementation Method 2
a separation step of separating a hydroxycarboxylic acid crystal from a mother liquid
Data Source
AI summary
Disclosed is a process for purifying a hydroxycarboxylic acid, comprising: a crystallization step of subjecting a hydroxycarboxylic acid aqueous solution to crystallization for purification, a separation step of separating a hydroxycarboxylic acid crystal from a mother liquid, and a washing step of washing the hydroxycarboxylic acid crystal for further purification with a washing liquid, wherein the washing liquid is a hydroxycarboxylic acid aqueous solution. The purified or refined hydroxycarboxylic acid obtained through the above process is suitably used as a starting material for production of a polyhydroxycarboxylic acid. The above process is suitably included in a process for producing a cyclic ester and a process for producing a polyhydroxycarboxylic acid.