Hydrogen sulfide removal from biogas on ZIF-derived nitrogen-doped carbons

This work studied the H₂S removal from biogas, a CO₂-containing gas mixture, over nitrogen-doped carbon materials deriving from the carbonization of ZIF-8. The H₂S sorption performance on a series of N-doped porous carbon materials was investigated, in which the N-doping composition and textural properties of adsorbents were turned by varying the carbonization temperatures. By changing the carbonization temperatures from 750 to 950 ℃, the N contents vary in the range of 17.75−5.46 wt.%, and the BET surface area in the range of 373-757 cm²/g, while the H₂S sorption capacity vary from 28.4–48.2 mg-H₂S/g-sorb accordingly. Detailed characterization results (XPS, XRD, FTIR, and TGA/DTA) reveal the correlation of H₂S sorption capacity with doped N species and porosity, in which the N surface area/volumetric density is crucial. This observation is corroborated by the kinetic studies by fitting H₂S adsorption isotherms with Langmuir and Dubinin-Radushkevich isotherm (DR) isotherms. The H₂S sorption capacity is independent of CO₂ concentrations examined (up to 40 vol%) on ZIF-8-derived sorbents, making them promising candidates for H₂S removal from biogas.