H2S to H2 and Sulfur: Converting a Dangerous and Destructive Waste Gas into Useful Products: Ongoing Research

     Research in 2021 from a couple of different papers shows that the dangerous and destructive gas hydrogen sulfide, or H2S, can be converted into hydrogen gas (H2) and sulfur, both desirable and valuable products. In one case, a reactor design achieved 24% higher sulfur uptake in 2% Molybdenum-doped iron-based sulfur carriers compared with undoped sulfur carriers. Both processes use a sulfur looping reactor that involves two processes: sulfidation and regeneration.

     H2S is commonly emitted from manure ponds, sewers, and is a major byproduct of oil refining, paper production, and mining. It also occurs naturally in some rock formations and in some oil & gas reservoirs, where it can endanger workers. I experienced low-level H2S poisoning while working on a well in Eastern Kentucky in the 1990s. We had an H2S detector and measured 10 parts per million (ppm) constant flow, but about 40ppm when the rig made a connection (added more drill pipe). The gas was from the St. Peter Sandstone, and we were drilling “on air” using compressed air to clean the hole. The H2S actually caused a hole to form in the flow line. After a few days of this, while staying onsite, I developed a constant headache and neck ache and decided to get a hotel room away from the site. Once we loaded the hole with drilling mud, there was no longer any HS coming from the well. I also took an H2S training course where we had to use Scott Air Packs and learn protocols for dealing with the gas. Several oil and gas workers have been killed by H2S, some due to a lack of training and not observing necessary safety protocols. H2S is also known as a very corrosive agent to metals, even at low levels.

     An article in the Brighter Side of News explains common industrial practices for dealing with H2S. Currently, one of the most widespread technologies for H2S processing is the Claus process, a catalytic process that converts H2S into elemental sulfur and steam.

“Current industry practices use the Claus process to remove hydrogen sulfide from waste streams. This process burns the gas to recover elemental sulfur and steam, but it wastes hydrogen and requires large amounts of energy. It's costly, inefficient, and doesn't recover hydrogen as a fuel. Alternative strategies, like selective oxidation and reactive adsorption using metal oxides, can capture more sulfur but still destroy the hydrogen content.”

“A better way would be to keep the hydrogen and transform it into usable fuel. That’s where the new process—nonoxidative decomposition of hydrogen sulfide—comes in. Instead of burning the gas, this method splits it directly into hydrogen and sulfur. However, there's a catch. The chemical reaction needed is highly endothermic, meaning it demands a lot of heat. Worse, the reaction tends to reverse itself before much hydrogen is made.”

     A research team at Ohio State University developed a one-reactor sulfur looping design with two stages: sulfurization and regeneration.

“In the first step, a metal absorbs sulfur from hydrogen sulfide while releasing hydrogen gas. In the second step, the sulfur-laden metal is regenerated by heating it in an inert atmosphere to release solid sulfur, readying it for another round.”

     Low-cost, non-toxic iron sulfide (FeS) is used as the sulfur carrier in the reaction. However, it does not react fast enough alone to make the process effective. 2% Molybdenum doping is utilized as a catalyst to speed up the reaction, leading to 24% more sulfur absorption, making it more effective and economical. Hydrogen yield was also increased. The process is still at lab scale, so commercialization of it is still far off, but the results are promising.

     Another sulfur looping reactor scheme to decompose H2S into H2 was developed utilizing CO2  and Ni3S2 as carriers and zirconium oxide (ZrO2) and magnesium aluminate (MgAl2O4) as supports. The results were published in a December 2021 paper in the Chemical Engineering Journal. The abstract notes:

“This work demonstrates a novel strategy for H2S and CO2 utilization and provides new insights into effective support selection aiding the design of a robust and efficient sulfur carrier.”

 

    

 

References:

 

Researchers transform ‘sewer gas’ into clean hydrogen fuel. The Brighter Side of News. June 10, 2025. Researchers transform ‘sewer gas’ into clean hydrogen fuel

Mo-Doped FeS Mediated H2 Production from H2S via an In Situ Cyclic Sulfur Looping Scheme. Kalyani Jangam, Yu-Yen Chen, Lang Qin, and Liang-Shih Fan. ACS Sustainable Chemistry & Engineering. Vol 9/Issue 33. August 12, 2021. Mo-Doped FeS Mediated H2 Production from H2S via an In Situ Cyclic Sulfur Looping Scheme | ACS Sustainable Chemistry & Engineering

Researchers transform ‘sewer gas’ into clean hydrogen fuel. Researchers found a way to turn hydrogen sulfide—a toxic industrial byproduct—into clean hydrogen fuel using iron and molybdenum. Joseph Shavit. The Brighter Side of News. June 5, 2025. Researchers transform ‘sewer gas’ into clean hydrogen fuel - The Brighter Side of News

Synergistic decomposition of H2S into H2 by Ni3S2 over ZrO2 support via a sulfur looping scheme with CO2 enabled carrier regeneration. Kalyani V. Jangam, Anuj S. Joshi, Yu-Yen Chen, Shailaja Mahalingam, Ashin A. Sunny, and Liang-Shih Fan. Chemical Engineering Journal. Volume 426, 15 December 2021, 131815. Synergistic decomposition of H2S into H2 by Ni3S2 over ZrO2 support via a sulfur looping scheme with CO2 enabled carrier regeneration - ScienceDirect