Mixed-Oxide Anode Coating for Chlorine Selectivity and Reversal Resistance
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Solution Overview
Problem
Existing electrodes for chlorine production in electrolytic cells face challenges in achieving high catalytic activity, selectivity for chlorine evolution over oxygen, and resistance to current reversals, while also dealing with volatile precursors that cause uncontrolled losses during heat treatments.
Innovation Solution
A catalytic coating formulation based on RuO2, IrO2, and TiO2, applied from hydroxyacetochloride complexes, is used on a valve metal substrate, optimizing the molar ratios and thermal decomposition process to enhance resistance to current reversals and improve chlorine selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a formulation based on RuO2 mixed with SnO2 and a second noble metal (iridium or platinum) is used, then the overvoltage of chlorine evolution is lowered and process voltage is reduced, but the overvoltage of oxygen evolution is also lowered, causing excessive oxygen in the chlorine produced
Solution Approach 1:
The patent modifies the chemical composition parameters of the catalytic coating by incorporating specific ratios of RuO2, IrO2, and SnO2, along with TiO2 as a support oxide. This parameter optimization allows the electrode to maintain low chlorine overvoltage while suppressing oxygen evolution, resolving the contradiction between energy efficiency and product purity
Solution Approach 2:
The patent creates a composite catalytic coating material combining multiple metal oxides (RuO2, IrO2, SnO2, TiO2) with specific synergistic properties. This composite formulation achieves selective catalysis that favors chlorine evolution while minimizing oxygen evolution, solving the problem of excessive oxygen contamination
2Loss of energy
If formulations based on RuO2 and SnO2 with small amounts of IrO2 are applied, then optimum values of cell potential and moderate amounts of oxygen are obtained, but the electrode does not have optimum resistance to current reversals
Solution Approach 1:
The patent develops a composite material system where TiO2 serves as a robust support structure that provides mechanical stability and resistance to current reversals, while the catalytic components (RuO2, IrO2, SnO2) are dispersed on this stable framework. This composite architecture simultaneously achieves good electrochemical performance and structural reliability
Solution Approach 2:
The patent assigns different functional roles to different components of the coating: TiO2 provides structural stability and resistance to current reversals in the bulk, while the surface layers containing RuO2, IrO2, and SnO2 provide catalytic activity. This spatial differentiation of properties resolves the contradiction between electrochemical performance and mechanical reliability
3Ease of manufacture
If tetravalent tin precursors such as tin tetrachloride are used in the coating formulation, then the catalytic coating can be prepared, but the extreme volatility of the precursors causes uncontrolled losses during heat treatments
Solution Approach 1:
The patent changes the physical and chemical parameters of the precursor materials by selecting hydroxyacetochloride complexes instead of highly volatile tetravalent tin precursors. This substitution maintains the ability to form the desired catalytic coating while dramatically reducing volatility and uncontrolled losses during the heating and drying processes
Solution Approach 2:
The patent employs precursors that are stable enough to handle and process without special precautions against volatility, eliminating the need for complex containment and control measures during manufacturing. This simplifies the production process and reduces material losses
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 new formulation significantly increases the electrode's resistance to current reversals and improves chlorine evolution selectivity, maintaining optimal cell potential and reducing precursor volatility issues.
Implementation Method 1
a catalytic layer containing oxides of tin, ruthenium, iridium and titanium applied to a substrate of a valve metal
Implementation Method 2
a formulation based on RuO2, IrO2, SnO2 and TiO2 on a metallic substrate; a formulation thus obtained leads to an appreciable improvement of the resistance of the electrode in situations of current reversal
Data Source
AI summary
The invention relates to a process for obtaining a electrode usable as a anode in electrolytic cells for the production of chlorine. The electrode thus obtained comprises a catalytic layer containing oxides of tin, ruthenium, iridium and titanium applied to a substrate of a valve metal.