High-pressure adsorption of H₂S, CO₂ and CH₄ on porous aromatic framework (PAF-30) at different temperatures

H₂S and CO₂ are considered two main impurities of natural gas and biogas. These impurities must be removed in order to achieve economic and environmental restrictions. Adsorption is a promising technology studied to achieve this goal. Among alternative adsorbents studied to capture H₂S and CO₂, porous aromatic frameworks (PAFs) had shown potential application because of suitable selectivity and remarkable adsorption capacity. However, H₂S and CO₂ adsorption/desorption data on PAF-30 are still scarce in literature. Thus, in this work, H₂S (up to 2.5 bar) and CO₂ and CH₄ (up to 50 bar) adsorption/desorption isotherms on PAF-30 were determined at 293, 303 and 313 K for the first time in literature. PAF-30 was synthesized and characterized by XRD, FTIR, ¹³C-NMR, Ar and CO₂ physisorption, SEM, TEM, TGA and DSC analyzes. Then, adsorption isotherms were determined gravimetrically. Experimental data were modelled with Jensen-Seaton equation. The results indicated that PAF-30 presents adsorption capacities in the order H₂S > CO₂ > CH₄. Adsorption/desorption branches do not match for systems studied, due to a hysteresis effect. Adsorption capacity decreases with temperature, indicating that physisorption is the main phenomenon observed. Experimental data were represented by Jensen-Seaton model. Thermodynamic analysis showed that all systems are exothermic and spontaneous. Working capacities obtained indicate that temperature reduces the performance for gas purification and that H₂S systems are affected by hysteresis loop. Moreover, cyclic adsorption results show that PAF-30 has potential to be applied and further studied in PSA simulations for H₂S and CO₂ capture under high-pressure conditions.