Three-Chamber Electrolysis Cell With Mechanical Stirring

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Solution Overview

Problem

The existing electrolytic cells with solid electrolytes like NaSICON face challenges due to pH gradients forming in the middle chamber during electrolysis, leading to damage and reduced longevity of the electrolyte, as well as inefficient use of alkali metal alkoxide solutions.

Innovation Solution

Incorporating a mechanical stirring device in the middle chamber of a three-chamber electrolytic cell, separated by a cation-conducting solid electrolyte and a diffusion barrier, to prevent pH gradients and enhance the stability and efficiency of alkali metal alkoxide production.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a three-chamber electrolytic cell with solid electrolyte (NaSICON) is used to protect it from acidic anolyte, then the electrolyte stability is improved, but a pH gradient forms in the middle chamber leading to local corrosion and reduced electrolyte lifespan

Engineering Contradiction:
Improveelectrolyte stabilityVSAvoidelectrolyte lifespan
Core Design Contradiction:
ReliabilityVSDuration of action of stationary object

Solution Approach 1:

A mechanical stirring device is introduced in the middle chamber to dynamically mix the electrolyte solution, preventing the formation of static pH gradients. The stirring converts the static electrolyte environment into a dynamic one, ensuring uniform pH distribution and preventing localized acid accumulation that would otherwise corrode the solid electrolyte.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The invention changes the physical state parameter of the electrolyte in the middle chamber from static to dynamic by introducing mechanical stirring. This parameter change affects the pH distribution uniformity, preventing local pH drops and the associated corrosion of the solid electrolyte while maintaining its protective function.

Inventive Principle:
Principle #35Parameter changes

2Reliability

If the middle chamber is supplied with alkaline solution from the cathode chamber to protect the solid electrolyte, then the electrolyte protection is improved, but the alkali metal alkoxide solution is consumed and contaminated

Engineering Contradiction:
Improveelectrolyte protectionVSAvoidalkali metal alkoxide consumption
Core Design Contradiction:
ReliabilityVSLoss of substance

Solution Approach 1:

The middle chamber is equipped with a mechanical stirring device that enables it to self-regulate its pH environment. The stirring promotes uniform distribution of OH- ions produced during electrolysis, allowing the middle chamber to maintain alkaline conditions and protect the solid electrolyte autonomously, without requiring continuous supply of alkaline solution from the cathode chamber.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The invention changes the pH control mechanism in the middle chamber from passive (relying on solution supply from cathode chamber) to active (using mechanical stirring to distribute OH- ions uniformly). This parameter change in pH distribution uniformity allows protection of the solid electrolyte while preventing consumption and contamination of the alkali metal alkoxide solution.

Inventive Principle:
Principle #35Parameter changes

3Device complexity

If no stirring is applied in the middle chamber, then the device complexity is reduced, but pH gradients form causing local corrosion and reduced productivity

Engineering Contradiction:
Improvecell structure simplicityVSAvoidelectrolysis efficiency
Core Design Contradiction:
Device complexityVSProductivity

Solution Approach 1:

A mechanical stirring device is introduced to create dynamic mixing in the middle chamber, converting the static electrolyte environment into a dynamic one. This dynamic mixing prevents pH gradient formation and associated corrosion, maintaining high electrolysis efficiency without significantly increasing device complexity.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The invention introduces a parameter change from static to dynamic electrolyte mixing in the middle chamber. This change prevents local pH drops and corrosion, maintaining optimal electrolysis conditions and productivity while adding only a simple stirring mechanism to the cell structure.

Inventive Principle:
Principle #35Parameter changes

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 mechanical stirring effectively prevents pH gradients, extending the lifespan of the solid electrolyte and improving the economical use of alkali metal alkoxide solutions by maintaining stable conditions and reducing corrosion.

Implementation Method 1

The mechanical stirring device can be used to stir the electrolyte solution in the middle chamber during electrolysis, which prevents the formation of a pH gradient.

Methodology Applied
Scientific EffectConvection: Convection

Implementation Method 2

a concentration gradient forms in the middle chamber of the electrolytic cell during electrolysis

Methodology Applied
Scientific EffectDiffusion: Diffusion

Implementation Method 3

The cathode compartment and the anode compartment are separated by a ceramic which conducts the alkali metal ion used, for example NaSICON

Methodology Applied
Scientific EffectIon conduction: Conduction (electrical)

Implementation Method 4

from the anode chamber by a diffusion barrier

Methodology Applied
Scientific EffectDiffusion: Diffusion

Implementation Method 5

When a current is applied, chlorine is formed at the anode - if a chloride salt of the alkali metal is used - and hydrogen and alcohol ions are formed at the cathode.

Methodology Applied
Scientific EffectElectrolysis: Electrolysis

Implementation Method 6

the pH drops in the anode chamber during electrolysis as a result of oxidation processes

Methodology Applied
Scientific EffectOxidation: Oxidation

Data Source

PatentEP4112779B1Three-chamber electrolysis cell for the production of alkali metal alcoholate
Publication Date: 2023.08.16 EVONIK OPERATIONS GMBH
  • EP4112779B1 patent drawingFigure 1
  • EP4112779B1 patent drawingFigure 2
  • EP4112779B1 patent drawing

AI summary

The present invention relates, in a first aspect, to an electrolysis cell comprising three chambers, wherein the middle chamber is separated from the cathode chamber by a solid electrolyte permeable to cations, for example NaSICON, and from the anode chamber by a diffusion barrier, for example, a membrane selective for cations or anions. The invention is characterized in that the middle chamber includes a mechanical stirring device. The electrolysis cell according to the invention solves the problem that a concentration gradient forms in the middle chamber of the electrolysis cell during electrolysis, leading to locally lowered pH values ​​and thus to damage of the solid electrolyte. The electrolyte solution in the middle chamber can be stirred during electrolysis by means of the mechanical stirring device.This leads to a mixing of the electrolyte solution in the central chamber, thereby preventing the formation of a pH gradient. In a second aspect, the present invention relates to a method for producing an alkali metal alkoxide solution in the electrolysis cell according to the invention.