Bio-electrochemical Cathode for Sulfur Compound Conversion
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Solution Overview
Problem
Current processes for converting mercaptans and disulphides in hydrocarbon streams are complex, chemically intensive, and inefficient, particularly in reducing mercaptans to less toxic compounds like bisulfide, with long hydraulic retention times and multiple processing steps.
Innovation Solution
A bio-electrochemical process involving a mixed culture of methanogens and anaerobic bacteria in a bio-electrochemical cell, where electrons are transferred from the cathode to convert thiol or polyorgano polysulphide compounds to bisulfide under anaerobic conditions, simplifying the conversion process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional processes (Merox process, hydrotreating) are used to convert mercaptans, then mercaptans are converted to disulphide oil or H2S, but the process becomes complex with numerous steps and chemical consumption
Solution Approach 1:
The patent combines multiple conventional process steps into a single bio-electrochemical reactor. The cathode serves as both the electron source for reduction and the support for microbial communities that catalyze the conversion, merging what were previously separate chemical treatment steps into one integrated biological-electrochemical system.
Solution Approach 2:
The cathode in the bio-electrochemical system performs multiple functions: it provides electrons for direct electrochemical reduction, supports microbial communities for biocatalysis, and serves as a substrate for biofilm formation. This multi-functionality replaces the need for multiple separate units in conventional processes.
2Reliability
If conventional processes are used to convert mercaptans, then conversion occurs, but long hydraulic retention times are required
Solution Approach 1:
The bio-electrochemical system operates continuously with constant electron supply to the cathode, maintaining steady-state conversion conditions. The microbial communities remain active and metabolically functional, ensuring continuous degradation without the batch processing interruptions that extend retention times in conventional systems.
Solution Approach 2:
The system changes the fundamental reaction parameters by providing direct electron transfer to the cathode and maintaining anaerobic conditions with controlled potential, creating optimal conditions for rapid microbial metabolism and electrochemical reduction that significantly accelerate conversion rates compared to conventional aerobic or chemical processes.
3Reliability
If methyl mercaptan is reduced in anaerobic digestion process, then bisulfide and methane are produced, but degradation rates are limited
Solution Approach 1:
The cathode acts as an intermediary electron donor, providing a direct electron transfer pathway to the mercaptan molecules and microbial cells. This external electron supply supplements the limited endogenous electron availability in conventional anaerobic digestion, dramatically enhancing degradation rates while maintaining the ability to produce bisulfide and methane.
Solution Approach 2:
The system creates a composite functional layer on the cathode surface consisting of extracellular electron transfer proteins, microbial cells, and electron mediators. This composite structure facilitates efficient electron transfer from the cathode to the substrates, overcoming the kinetic limitations of conventional anaerobic digestion while preserving the desired conversion products.
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
Effectively reduces organic sulfur compound levels to below 10 ppm, providing a simpler alternative to existing methods and enabling further conversion of bisulfide to elemental sulfur or hydrogen sulfide, thus addressing corrosion and toxicological concerns.
Implementation Method 1
by direct or indirect transfer of electrons from a cathode of a bio-electrochemical cell to the thiol or the polyorgano polysulphide (POPS) compound
Implementation Method 2
in the presence of methanogens. In addition, anaerobic or facultative anaerobic bacteria may be present
Data Source
Figure 1
AI summary
The invention is directed to a process to convert a sulphur compound to bisulphide by direct or indirect transfer of electrons from a cathode of a bio-electrochemical cell to the sulphur compound under anaerobic conditions and in the presence of mixed culture comprising methanogens and suitably also a anaerobic or facultative anaerobic bacteria. The sulphur compound may be a thiol like methanethiol or ethanethiol or a polysulphide, like dimethyl disulphide.