Lactic Acid Purification via Membrane Filtration and Distillation
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Solution Overview
Problem
Current methods for producing lactic acid and polylactic acid face challenges such as low productivity, impurities affecting thermal stability and mechanical strength, and high costs associated with purification processes like ion-exchange resin regeneration and expensive bipolar membranes.
Innovation Solution
A method involving continuous fermentation using a porous membrane followed by nanofiltration and distillation to produce high-quality lactic acid, which is then used for direct polymerization to achieve high-yield synthesis of lactide and polylactic acid with improved thermal stability and mechanical strength, while minimizing impurities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ion-exchange resin is used to remove inorganic ions from lactic acid solution, then purification quality improves, but operational cost increases due to regeneration requirements
Solution Approach 1:
The patent extracts and removes inorganic ions from the lactic acid solution using ion-exchange resin, separating the harmful impurities from the valuable lactic acid product. This extraction approach achieves high purification quality while the resin can be regenerated and reused, reducing operational costs compared to disposable purification methods.
Solution Approach 2:
The ion-exchange resin is not discarded after use but regenerated and reused multiple times. The regeneration process restores the resin's ion-exchange capacity, allowing continuous operation without frequent replacement. This recovering approach significantly reduces operational costs while maintaining consistent purification quality.
2Manufacturing precision
If bipolar membrane is used for inorganic ion removal, then purification quality improves, but device cost increases
Solution Approach 1:
The patent uses conventional ion-exchange resin that can be easily regenerated, replacing expensive bipolar membranes with a more economical solution. The resin operates effectively for multiple cycles before regeneration is needed, providing a cost-effective alternative to high-cost membrane technologies while achieving comparable purification quality.
Solution Approach 2:
The patent changes the purification approach from using expensive bipolar membranes to using regenerable ion-exchange resin, altering the technical parameter of purification method selection. This parameter change reduces device cost and complexity while maintaining effective inorganic ion removal capability.
3Ease of operation
If conventional filtration is used to remove calcium salt, then operational simplicity improves, but purification quality deteriorates due to dissolved calcium salt remaining
Solution Approach 1:
The patent introduces ion-exchange resin as an intermediary substance that selectively binds to inorganic ions in the lactic acid solution. This intermediary mechanism effectively removes dissolved calcium salts and other inorganic ions that conventional filtration cannot capture, achieving high purification quality while maintaining operational simplicity through a single-pass treatment process.
4Ease of manufacture
If inorganic ions are not sufficiently removed from lactic acid solution, then operational cost decreases, but product quality deteriorates due to racemization and oligomerization
Solution Approach 1:
The patent applies preliminary ion-exchange treatment to remove inorganic ions from the lactic acid solution before subsequent processing steps. This preliminary anti-action prevents the harmful effects of inorganic ions (racemization and oligomerization) from occurring during concentration and polymerization, ensuring high product quality and reliability while maintaining cost-effectiveness through a single regeneration-capable resin unit.
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 enhances the productivity and quality of lactic acid and polylactic acid, reducing impurities and operational costs by effectively removing inorganic ions and improving the thermal and mechanical properties of the final products.
Implementation Method 1
a fermentation culture medium of a microorganism having an ability of lactic acid fermentation is filtered through a porous membrane having an average pore size of not less than 0.01 μm and less than 1 μm
Implementation Method 2
the permeate is filtered through a nanofiltration membrane
Implementation Method 3
the permeate is distilled to recover lactic acid
Implementation Method 4
Lactic acid is known to be produced by fermentation by microorganisms which convert carbohydrate-containing substrates represented by glucose into lactic acid
Data Source
AI summary
Lactic acid is obtained by a method including (A) a step of continuous fermentation wherein a fermentation culture medium of a microorganism having an ability of lactic acid fermentation is filtered through a porous membrane having an average pore size of not less than 0.01 μm and less than 1 μm with a transmembrane pressure difference within the range of 0.1 to 20 kPa, and the permeate is collected, while retaining the non-permeated liquid in or returning the non-permeated liquid to the culture, and adding a fermentation feedstock to the culture; (B) a step of filtering the permeate obtained in Step (A) through a nanofiltration membrane; and (C) a step of distilling the permeate obtained in Step (B) under a pressure of not less than 1 Pa and not more than atmospheric pressure, at 25° C. to 200° C. to recover lactic acid.