A nanoporous polymeric sorbent for deep removal of H₂S from gas mixtures for hydrogen purification

A nanoporous composite sorbent (PEI/SBA-15) was developed by the wet impregnation loading of a linear polyethyleneimine (PEI) on a mesoporous molecular sieve SBA-15, which was prepared by hydrothermal synthesis. The sorbent was characterized by XRD at low angles, N₂ physisorption, scanning electron microscopy (SEM) and FT-IR. The sorption performance of the sorbent for removing H₂S from H₂-containing gas mixtures was evaluated in a flow system. The characterization results showed that after PEI loading, PEI was dispersed inside the meso-channels of SBA-15 with almost no change of the SBA-15 structure, and the interaction of amine groups in PEI with the functional groups on the SBA-15 surface may anchor PEI on the inner surface of SBA-15. The effects of the inlet H₂S concentration and co-existing moisture on the sorption performance were examined. With increasing inlet H₂S concentration, both the breakthrough capacity and the saturation capacity increased. The sorption of H₂S on the PEI/SBA-15 sorbent can be expressed by the Langmuir adsorption isotherm. A higher sorption capacity was observed in the presence of moisture, indicating that moisture has a promoting effect on the sorption removal of H₂S from gas streams on the PEI/SBA-15 sorbent. However, the desorption rate of the sorbed H₂S was also reduced in the presence of moisture. The sorption/desorption cycles showed that the PEI/SBA-15 sorbent had a good regenerability and stable sorption performance.