Influence of Loading a Tertiary Amine on Activated Carbons and Effect of CO₂on Adsorptive H₂S Removal from Biogas

This work studied the influence of loading a tertiary amine on activated carbons (ACs) and the effect of CO2 on adsorptive H2S removal from biogas. After loading a tertiary amine, tetramethyl hexanediamine (THMDA), the H2S adsorption capacity increased for all ACs but with different levels. Detailed characterization results (TGA-MS, TGA/DTG, and in situ FT-IR) demonstrate the TMHDA-induced changes of surface oxygen or nitrogen functional groups, pH value, and textural properties and their impacts on H2S adsorption performance, which also varied with CO2 concentrations. On bare AC adsorbents, the H2S adsorption is attributed to the surface oxygen functional groups, whereas on tertiary amine-loaded ACs, the H2S adsorption is due to the interaction between H in H2S and N in the amine group. The presence of CO2 can promote H2S adsorption on some ACs and THMDA-loaded ACs. The formation of solid sulfur and CH4 was observed for the H2S adsorption in the presence of CO2.