One-Step Preparation of N-Doped Coal-Based Carbon for H2S Desulfurization

Hydrogen sulfide (H2S) commonly exists in natural gas, syngas, and coal-derived gas, and the elimination of H2S from industrial gases is essential before application. In this study, we utilized low-cost lignite as a raw material. After acid-washing pretreatment, nitrogen-containing substances (urea or dicyandiamide) were incorporated into the coal, and two types of N-modified activated carbon desulfurizers for ambient-temperature H2S removal were prepared via an in situ loading method, integrating the synthesis of activated carbon with the loading of active components. When the dicyandiamide content was 9 wt.%, and the oxygen concentration for desulfurization was 5%, the breakthrough time reached 550 min with a corresponding breakthrough sulfur capacity of 79.6 mg/g. Characterization revealed that the dicyandiamide-N-modified desulfurizer possessed elevated oxygen and nitrogen contents, which may partially augment the density of surface alkaline active sites. This enhancement is likely to induce alkalization of the interfacial water layer, thereby potentially accelerating H2S dissociation into HS− and subsequently facilitating its oxidative conversion to elemental sulfur via reaction with oxygen.