Polyphosphate Ferric Iron Catalyst for Sulfur Recovery
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Solution Overview
Problem
Conventional chelated iron catalysts used in liquid redox sulfur recovery (LRSR) processes are prone to oxidation and loss due to hydroxyl radical generation, leading to increased costs and impure sulfur recovery, with no economically viable means to employ Fenton reactions at circumneutral pH.
Innovation Solution
A process utilizing a ferric ion complexed with polyphosphate, such as sodium tetrapolyphosphate, which is resistant to oxidation and maintains stability, allowing for efficient oxidation of hydrogen sulfide and organic contaminants, and recovery of sulfur with minimal catalyst loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional chelated iron catalysts are used in LRSR processes, then hydrogen sulfide oxidation and sulfur recovery can be achieved, but the catalyst undergoes oxidation and loss over time due to hydroxyl radical generation
Solution Approach 1:
The patent changes the chemical parameter of the ligand from conventional chelating agents (EDTA, NTA) to polyphosphate, which fundamentally alters the catalyst's resistance to oxidation. This parameter change enables the catalyst to maintain stability while continuing to achieve efficient sulfur recovery.
Solution Approach 2:
The patent creates a composite catalyst system by combining ferric ion with polyphosphate ligand, forming a new chelate complex that exhibits both high catalytic activity for sulfur recovery and enhanced stability against hydroxyl radical oxidation, resolving the contradiction between productivity and reliability.
2Reliability
If conventional chelating agents are used to stabilize ferric iron, then catalyst stability is improved, but the cost increases and residual environmental impact occurs
Solution Approach 1:
The patent replaces expensive conventional chelating agents (EDTA, NTA) with polyphosphate, which is more economical and environmentally benign. The polyphosphate ligand provides sufficient stability without the high cost and environmental concerns associated with traditional chelators.
Solution Approach 2:
The patent changes the ligand parameter from expensive conventional chelating agents to polyphosphate, fundamentally altering both the cost structure and environmental profile while maintaining catalyst stability through the unique binding properties of polyphosphate to ferric ion.
3Reliability
If hydroxyl radical scavengers are added to prolong catalyst life, then catalyst stability is improved, but the useful life is still limited and H2O2 cannot be used to enhance the process
Solution Approach 1:
The patent applies preliminary anti-action by designing the polyphosphate-chelated ferric iron complex to inherently resist hydroxyl radical attack before the degradation can occur. The polyphosphate ligand's molecular structure provides built-in protection against oxidation, eliminating the need for external scavengers and enabling prolonged catalyst life.
Solution Approach 2:
The patent changes the ligand parameter to polyphosphate, which fundamentally alters the catalyst's resistance properties. This parameter change enables the catalyst to withstand hydroxyl radical generation without degradation, allowing the use of H2O2 to enhance the process while maintaining stable catalyst operation.
4Productivity
If conventional LRSR processes are used, then sulfur recovery can be achieved, but the recovered sulfur is impure and of lesser value
Solution Approach 1:
The patent changes the catalyst system parameter to polyphosphate-chelated ferric iron, which improves the selectivity and efficiency of the oxidation process. This parameter change leads to more complete oxidation of hydrogen sulfide and reduces impurities in the recovered sulfur, enhancing both productivity and manufacturing precision.
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 process achieves fast and economical sulfur recovery with reduced catalyst loss and toxicity reduction, enabling continuous operation without large reaction tanks, and enhances the performance of LRSR and Fenton-like oxidation processes.
Implementation Method 1
Fe(III)-L acts as a catalyst for the oxidation of H2S by oxygen... Fe(II)-L is oxidized by air to Fe(III)-L... The overall reaction for the oxidation of H2S in these processes is: 1/2O2+H2S→H2O+1/8S8
Implementation Method 2
Fenton-like oxidation processes carried out in solutions with pH ranging from neutral to alkaline... Fe(II)-L+H2O2→Fe(III)-L+OH−+●OH
Implementation Method 3
The OH-radical generated in the above process reacts with, and degrades, the ligand... Fe(II)-L+H2O2→Fe(III)-L+OH−+●OH
Data Source
AI summary
Described is a process for treatment of a fluid comprising an oxidizable contaminant selected from one or both of a sulfide and a thiol, the process comprising the step of contacting the fluid with a first complex of ferric iron and a polyphosphate to oxidize the oxidizable contaminant and generate a second complex of ferrous ion and the polyphosphate.