Hydrogen sulfide (H2S), often referred to as “sour gas,” is naturally present in both crude oil and natural gas formations. It can be found throughout the oil and gas extraction process, including in oil wells, gas pipelines, processing plants, and even during drilling operations. Due to its heavier-than-air nature, H2S can accumulate in low-lying areas like cellars, pits and tanks. Hydrogen sulfide can also be found in biogas produced by the breakdown of organic waste in landfills as well as from the manure produced by cows on dairy farms.
Due to detrimental implications, H2S removal is mandated at every stage of hydrocarbon production. Given its toxicity and explosive nature, removing H2S is required for ensuring personnel safety, compliance with pipeline specifications, catalyst performance, corrosion prevention, and environmental preservation.
Exploration and production (E&P) companies are known to pay $15+ million a year in operating costs to remove H2S, but some existing technologies being used in production fields may fail to achieve their purpose. Some contain no flash pots to recover methane, so untreated plumes of H2S are released into the atmosphere, risking both the environment and the safety of the people working at the facility.
E&P companies are tasked with finding the most appropriate H2S removal solution, taking into consideration key factors such as the concentration of H2S present, the application environment, desired removal efficiency, operational costs, waste management needs, and the potential for regeneration of the H2S.
The use of scavengers for H2S removal emerged alongside the development of chemical gas treating processes in the mid-20th century. H2S scavengers have evolved from primarily using iron sponge-based systems to more advanced chemical-based scavengers driven by concerns about environmental impact, improved efficiency, and the need to handle increasingly complex production environments. There are water-based or liquid scavengers, solid scavengers, oil-soluble scavengers, and regenerative scavengers. Each type of scavenger has unique benefits and challenges, and each must be reviewed on a case-by-case basis to determine the best choice for the individual treatment need.
Solid scavengers, also known as adsorbents, play a crucial role in H2S removal by providing a large exterior surface area as well as internal sites where the H2S molecules can bind and be effectively captured from gas streams. Adsorbents are one of the most efficient and widely used methods for H2S removal in downstream, midstream, upstream and renewables processes due to their ability to handle low to high concentrations of H2S, and they can be used in a wide range of application conditions and provide ease of operation.
There is a recent entry into the adsorbent market that has proven disruptive. SULFURTRAP EX® is a fixed bed, concentrated iron-based scavenger for removal of H2S and light mercaptans in batch processing applications. The composition of the adsorbent and its unique manufacturing process give the media high surface area and crush strength, and a pore structure that allows sulfur species to bond throughout the media. Bed life is extended beyond what is traditionally experienced with other iron-based scavengers and provides unprecedented sulfur loading capacity and price per pound of H2S removed economics.
Operations also will realize the benefit of low and consistent pressure drop from start of run to end of run due to the robust nature of the product and will find improved bed disposal and replacement because the product does not cake or agglomerate while in service. SULFURTRAP® EX adsorbent is manufactured to flow out of each vessel during a changeout as opposed to other adsorbents that may have to be chiseled or jack-hammered out of vessels, thus providing faster and more cost-effective bed changes.
Adopting and applying innovative techniques or technologies that are successful in one sector can be strategic for solving problems or improving operations in another. The same is true for oil and gas operations across sectors. There is a well-known refinery process that has been used in downstream since the 1980s that is getting the attention of companies needing larger quantities of H2S removal.
LO-CAT® liquid redox system has become the predominant solution for H2S removal for treatment of 1.5 tons per day up to 20 tons per day (TPD) of sulfur removed from gas streams. While LO-CAT has long been the preferred choice for large-scale midstream and refinery operations, these flexible, efficient systems offer a proven, cost-effective solution for upstream and renewables applications
LO-CAT’s aqueous-based ambient temperature process features a chelated-iron catalyst that can be used to treat almost any gas stream. With removal efficiencies of over 99.9% and up to 100% turndown, H2S is converted to elemental sulfur.
The process chemistry of the LO-CAT technology is embedded in its name: Liquid Oxidation CATalyst. The overall system oxidation reaction is as follows:
H2S (gas) + ½ O2 (gas) → H2O + S0
This is a well-known oxidation reaction. This overall reaction is sub-divided into two parts:
(i) H2S gas absorption, ionization, and reaction to make solid sulfur in the liquid solution;
(ii) The liquid solution is then oxidized using air and regenerated for re-use.
In chemistry terms, step (i) is called REDUCTION, and step (ii) is called OXIDATION. Therefore, the LO-CAT process is called a REDOX (REDUCTION-OXIDATION) reaction process.
Operators should be aware that not all liquid redox systems are equal. Some companies bring decades of experience, having successfully addressed a wide variety of applications and challenges. This extensive track record translates into a deep understanding of how different feedstocks, operating conditions, and customer needs affect system performance. With the ability to design both standard and custom liquid redox units for ranges of sulfur removal from 1.5 to 20 TPD, these companies ensure optimal reliability, and long-term operational efficiency. The value of such experience is crucial when selecting a sulfur removal solution – helping to mitigate risks, improve performance, and reduce the likelihood of costly operational setbacks.
There is a variety of H2S treatment technologies available, each suited to different applications, process conditions, costs and technical requirements. In selecting the right technology, it is valuable to consider the proven success of each solution. By evaluating the track record of these technologies, operators can gain insight into their effectiveness in achieving positive outcomes and delivering consistent value in real-world applications over time.
Headline photo: Modular SULFURTRAP® Lead/Lag Vessel System, an Iron Solid Adsorbent Option for H2S Mitigation. ©2025 Merichem Technologies™
Jim Aiello is Managing Director of Sales & Technology Licensing at Merichem Technologies LLC. He has over 30 years in global leadership roles key to improving performance in complex markets, regulatory and political environments. He was Vice President Energy, Mining & Infrastructure with International SOS, a leading worldwide medical assistance and security company. Aiello also held strategic positions with Lurgi Oil, Gas & Chemicals, AlliedSignal Engineered Materials and Pacific Refining Co. He began his career at Exxon Research & Engineering Co.
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