Adsorption of H₂S from Hydrocarbon Gas Using Doped Bentonite: A Molecular Simulation Study

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Hydrogen sulfide (H₂S) is a toxic impurity in hydrocarbon gases like natural gas and landfill gas.
• H₂S causes significant downstream processing issues, including pipeline corrosion in the presence of moisture.
• Cost-effective and energy-efficient H₂S removal methods are crucial for gas refinement and utilization.

Purpose of the Study:

• To predict adsorption isotherms for methane, H₂S, and nitrogen in cation-doped bentonites.
• To evaluate the potential of doped bentonites for targeted H₂S removal from natural gas and landfill gas.
• To guide the development of low-cost pressure-swing adsorption systems.

Main Methods:

• Grand canonical Monte Carlo (GCMC) simulations were employed.
• An ab initio force field was utilized for accurate molecular modeling.
• Simulations were conducted for pure species and gas mixtures under relevant conditions.

Main Results:

• All three doped bentonites (K⁺, Li⁺, Na⁺) demonstrated highly selective adsorption of H₂S.
• The adsorbed phase primarily consisted of H₂S, indicating effective contaminant removal.
• Performance ranking of adsorbents was determined as K⁺ > Li⁺ > Na⁺.

Conclusions:

• Doped bentonites show significant promise for selective H₂S removal from hydrocarbon gas streams.
• Potassium-doped bentonite exhibits superior performance compared to lithium- and sodium-doped variants.
• Understanding gas-gas and gas-solid interactions is important for optimizing adsorption processes, especially at low pressures.