Two-Phase Electrolysis for Carboxylic Acid Production
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Solution Overview
Problem
Electrolysis cells used for producing lactic acid and other carboxylic acids face membrane poisoning due to the acidic nature of the produced acids, which disrupts sodium ion conduction through solid ion conducting membranes like NaSICON, leading to a halt in acid formation.
Innovation Solution
A two-phase electrolysis approach is employed, using a mixture of aqueous and non-aqueous solvents where lactic acid is preferentially absorbed into the non-aqueous phase, maintaining a basic pH in the anolyte and preventing membrane fouling by keeping sodium lactate in the aqueous phase, allowing continuous sodium ion conduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a solid ion conducting membrane (e.g., NaSICON membrane) is used in the electrolysis cell to enable sodium ion conduction, then the electrolysis reaction can proceed to produce lactic acid, but the produced lactic acid decreases the pH of the anolyte solution which stops sodium ion conduction through the membrane, causing membrane poisoning and halting acid formation
Solution Approach 1:
The harmful lactic acid product is extracted from the aqueous anolyte phase into a separate non-aqueous organic phase. This extraction removes the acid from the environment that would otherwise poison the membrane, allowing continuous operation without pH-induced conduction stoppage
Solution Approach 2:
The anolyte is segmented into two distinct phases: an aqueous phase that maintains basic pH for membrane conduction and a non-aqueous organic phase that absorbs the produced lactic acid. This segmentation isolates the harmful acid from the membrane interface while preserving the conduction function in the aqueous phase
2Quantity of substance
If the electrolysis continues to produce lactic acid, then the desired product yield increases, but the accumulated acid poisons the membrane and stops the reaction
Solution Approach 1:
The harmful lactic acid that would normally poison the membrane is converted into a beneficial separated phase. The acid's natural tendency to partition into the organic phase is exploited to remove it from the aqueous phase, transforming the poisoning problem into a separation advantage that enables continuous high-yield production
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 prevents membrane poisoning, allowing for continuous production of lactic acid and other carboxylic acids without disrupting sodium ion flow, thus maintaining the electrolysis cell's operational efficiency.
Implementation Method 1
The present embodiments use a mixture of aqueous (or more polar) and non-aqueous (or less polar) solvents in the anolyte. In one embodiment, the lactic acid (or another carboxylic acid) that is produced in the anolyte is removed into the non-aqueous (organic) second phase. The second phase (organic phase) therefore preferentially absorbs the lactic acid from the aqueous phase, leaving sodium lactate anions in the aqueous phase. This phenomenon is called partitioning.
Implementation Method 2
During the chemical reaction, the produced sodium ions (Na+) flow through the cell's membrane (e.g., towards the cathode).
Implementation Method 3
This reaction involves sodium lactate aqueous solution (under the influence of an applied voltage) to produce lactic acid at the cell's anode. This chemical oxidation reaction of the cell's anolyte solution is represented as follows:
Data Source
AI summary
A method for producing and recovering a carboxylic acid in an electrolysis cell. The electrolysis cell is a multi-compartment electrolysis cell. The multi-compartment electrolysis cell includes an anodic compartment, a cathodic compartment, and a solid alkali ion transporting membrane (such as a NaSICON membrane). An anolyte is added to the anodic compartment. The anolyte comprises an alkali salt of a carboxylic acid, a first solvent, and a second solvent. The alkali salt of the carboxylic acid is partitioned into the first solvent. The anolyte is then electrolyzed to produce a carboxylic acid, wherein the produced carboxylic acid is partitioned into the second solvent. The second solvent may then be separated from the first solvent and the produced carboxylic acid may be recovered from the second solvent. The first solvent may be water and the second solvent may be an organic solvent.