Nitrogen-Rich Mesoporous Carbons: Highly Efficient, Regenerable Metal-Free Catalysts for Low-Temperature Oxidation of H2S

Abstract

We demonstrate that it is possible to transform traditional mesoporous carbons into a superior metal-free catalyst for low-temperature H2S removal via doping a high concentration of nitrogen atoms into the carbon. The nitrogen doping level is important for the activity of mesoporous carbons as a metal-free catalyst. Although carbons doped with only an intermediate amount of nitrogen (e.g., 4.3 wt %), show little aptitude for the catalytic oxidation of H2S when nitrogen doping reaches a certain high level (e.g., 8.5 wt %), the nitrogen-rich mesoporous carbons (NMC) exhibit high catalytic activity and selectivity toward H2S oxidation at low temperature. Further study suggests that the pyridinic nitrogen atoms are responsible for the catalytic activity in H2S oxidation. Owing to the metal-free nature of the NMC catalyst, it can be easily regenerated by CS2 scrubbing, and the product sulfur can be recovered. Our desulfurization results suggest that such metal-free carbons could, indeed, overcome the limitations of the conventional H2S catalysts and provide suitable, sustainable, and inexpensive solutions for technological development in H2S removal.