Adsorption of hydrogen sulfide, carbon dioxide, methane, and their mixtures on activated carbon

H₂S and CO₂ are acid contaminants of natural gas and biogas, which removal have been studied using adsorption data for monocomponent and binary mixtures. However, equilibrium adsorption data for H₂S + CO₂ + CH₄ mixture has not been investigated yet. In this work, H₂S and CO₂ partition coefficients (K) and activated carbon (AC) selectivity (S) for H₂S + CO₂ + CH₄ mixture separation at high-pressure and different temperatures were determined. To reach this goal, monocomponent isotherms for H₂S, CO₂ and CH₄ on Brazilian babassu coconut hush AC were experimentally determined at different temperatures and pressures. Then, obtained data were correlated by Langmuir and Tóth models, and multicomponent adsorption was predicted using Extended Langmuir, Extended Tóth and Ideal Adsorption Solution Theory (IAST) methods. Results indicate AC captures approximately 26 wt% of H₂S or CO₂. K values for CO₂ and H₂S reached more than 3 and 26, respectively, depending on the predictive model utilized and were higher for diluted mixtures (high CH₄ content in gas phase). S values for CO₂ and H₂S can reach values greater than 25 for Tóth + IAST. Furthermore, selectivity toward H₂S is approximately 5.6 times greater than CO₂. The effect of temperature on multicomponent results indicate K and S values decrease as temperature increases. Therefore, results obtained herein show that is possible to separate H₂S and CO₂ from mixture containing CH₄ using this AC as adsorbent and better separation performance was observed for low H₂S and CO₂ concentrations and lower temperatures.