Preparation of nitrogen-doped activated carbon used for catalytic oxidation removal of H₂S

In this study, nitrogen-doped modified activated carbons were synthesized for H₂S removal from Zhuxi activated carbon and 4,4′-bipyridine as raw material and nitrogen source, respectively. The synthesis strategy was hydrothermal treatment and subsequent NH₃ annealing, and the formation and conversion patterns of the different N configurations were investigated. When the annealing temperatures were 500 °C and 600 °C, N-5 account for the majority. As the annealing temperature increased, the proportion of N-6 gradually increased. After the temperature increased to 1000 °C, N-5 and N-6 were converted to N-Q to a certain degree, while the amount of nitrogen doping decreased significantly. The sample H160-0.2-800 exhibited excellent H₂S removal with a high sulfur capacity of up to 206.89 mg/g, significantly higher than that of the original activated carbon ZX1200 (67.56 mg/g). The reason for this is that the micropores (V_mic = 0.5155 cm³/g) and specific surface area (S_BET = 1369.5 m²/g) of the modified activated carbon are more developed than those of the original activated carbon. A high nitrogen content (3.14 wt%) and N-6 configuration proportion (73.56 %) are significant reasons for the excellent adsorption properties. The mechanism of the catalytic oxidation was investigated. The introduction of surface nitrogen-containing functional groups alkalizes the activated carbon surface, enhancing the adsorption and dissociation of H₂S and O₂ and facilitating the formation of sulfur radicals and elemental sulfur.