SulfaTrap^TM-R7Q is a low-cost absorbent that can achieve a sulfur removal at a cost <$4.0/kg S (depending on the size of the application, moisture and oxygen content of the gas). While iron oxide-based scavengers represent the lowest cost option for solid-state H₂S removal, their application is limited to gas streams that contain sufficient concentration of moisture for the sorbent to achieve a high sulfur uptake (at a minimum of 5,000 ppmv H₂O is recommended for successful use of our sorbent).

SulfaTrap^TM-R7Q sorbent is typically housed in fixed-bed vessels where gas flows through the adsorbent material, reacting with and removing H₂S.  In conventional systems, the sorbent is loaded into a single vertical vessel, while a lead-lag configuration typically provides a much higher sorbent utilization and lower the operating cost.  The H₂S chemically reacts with the sorbent pellets to form a safe, stable, non-hazardous and free-flowing byproduct.

Primary uses of SulfaTrap^TM-R7Q sorbent includes:

• Refinery applications
  • Emission control (via purification of fuel gas)
  • Sour water gas treatment
  • Treatment of refinery off-gases used as chemical feedstock (e.g., H₂ production)
• Petrochemical plants
• Wellhead and off-shore gas processing
• Biogas plants
• CO₂ purification
• Wastewater treatment
• Odor control

A few of the noteworthy applications of this product include the following (references will be available):

• Refinery off-gas treatment system removing H₂S from an H₂-rich fuel gas stream (with high concentrations of CO, CO₂ and minor contaminants such as C2-C6 hydrocarbon and C2-C4 olefins) in North Dakota, U.S. Each vessel holds 150 m³ of SulfaTrap^TM-R7Q sorbent

• Sour water gas treatment system removing H₂S from an ammonia (NH₃)-rich CO₂ stream in a refinery located in Martinez, CA. Each vessel holds 45 m³ of SulfaTrap^TM-R7Q sorbent.

• Biogas treatment system removing H₂S from an anaerobic digester generated biogas (55/45 CH₄/CO₂ molar ratio). Sorbent is housed in 22.5 m³

While the Cu-based mixed metal oxide/hydroxide sorbent is more expensive than the iron-based scavengers, it can operate on dry gas, achieving lower H₂S levels while removing other sulfur compounds like mercaptans.

The configuration of vessels housing the SulfaTrap^TM-R7J are similar to those used for SulfaTrap^TM-R7Q.  Due to its significantly faster absorption kinetics, SulfaTrap^TM-R7J can be used in single columns (rather than lead-lag configuration) providing a high utilization.  In these systems:

• Sour gas (gas containing H₂S) is fed into a vertical pressure vessel containing the absorbent bed
• The H₂S in the gas reacts with the scavenger material, forming a stable metal sulfide and water
• The treated gas then flows out, with the H₂S removed
• The spent scavenger media is periodically replaced with fresh material

The use of SulfaTrap^TM-R7J does not require presence of moisture in high concentrations; in fact the moisture content of the gas can be at undetectable levels, which will have no impact on the sulfur uptake of this sorbent.  Hence, the primary use of this sorbent is with high pressure gas (where the gas has limited capacity to hold water).

Some noteworthy uses are listed below:

• Pipeline gas treatment (deodorization/desulfurization) – Largest application is a two-column system operating in series, treating 230 MMSCFD pipeline natural gas in Weld County, CO.

• Another major use is for the treatment of high pressure natural gas supporting the operation of aluminum smelters. High performance aluminum manufacturing processes require a low sulfur feed to the natural gas direct firing furnaces.  SulfaTrap^TM-R7J sorbent has been successfully used in aluminum smelters in Saudi Arabia, Bahrain and United Arab Emirates, vessel sizes housing the sorbent ranging from 20 to 30 m³.

• The most widespread use of the sorbent is in the removal of H₂S from biomethane downstream of the polymer membranes used in CH₄/CO₂ As water is rejected along with the CO₂, the gas stream is very dry in these applications.  SulfaTrap^TM-R7J is used in more than 50 plants in the U.S., Canada and Europe.

• SulfaTrap^TM-R7J is also used in H₂S removal from CO₂ in Canada.

This sorbent requires the presence of oxygen (O₂) to achieve the removal of H₂S, which significantly enhances H₂S removal over carbon sorbents by promoting the catalytic oxidation of H₂S to elemental sulfur and, to a lesser extent, sulfates. This process is crucial for the efficient and high-capacity desulfurization of gas streams.  The carbon support contains meso-scale pores (10-50 angstrom range) to accommodate the depositing sulfur.

Without oxygen, H₂S is primarily removed through weak and reversible physical adsorption or reaction with existing oxygen-containing surface functional groups, forming sulfates (SO₄²⁻), which offers limited capacity.  In the presence of O₂, the mechanism shifts to a more efficient catalytic oxidation process:

1. Adsorption: Both H₂S and O₂ are adsorbed onto the active sites of the carbon sorbent surface.
2. Catalytic Reaction: The activated carbon acts as a catalyst, facilitating the reaction between the adsorbed H₂S and O₂ to produce elemental sulfur (S) and water (H₂O). This reaction is highly favorable thermodynamically but requires the catalytic surface to proceed efficiently at typical operating temperatures (below 100°C).

The primary reaction:

2H₂S + O₂ → 2S + 2H₂O

This reaction deposits solid elemental sulfur within the carbon's pore structure, which can create an autocatalytic effect for further H₂S oxidation.  At higher temperatures (above 100°C, especially above 300°C) or with excess oxygen, elemental sulfur can further react to form gaseous sulfur dioxide (SO₂):

S + O₂ → SO₂

A secondary reaction of H₂S to SO₂:

2H₂S + 3O₂ → 2SO₂ + 2H₂O

Key Effects of Oxygen

• Increased Capacity: Oxygen dramatically increases the H₂S removal capacity and breakthrough time of the sorbent compared to non-oxidative conditions.
• Enhanced Kinetics: The presence of O₂ facilitates faster reaction rates, crucial for efficient removal in continuous flow systems.
• Optimal Conditions: The process works best at lower temperatures (sub-100°C) and requires sufficient moisture to prevent the over-oxidation to SO₂ and to allow for optimal reaction conditions.

The primary use of this sorbent is in odor control (removing H₂S from air) and biogas treatment (where some air intake to anaerobic process results in low but finite concentration of O₂ in the biogas).