Manipulation of Waste-Activated Carbon Absorbers as Efficient Carbocatalysts for H₂S Selective Oxidation

Carbon-based catalysts have been widely reported as efficient metal-free catalysts for the selective oxidation of hydrogen sulfide (H2S). Waste-activated carbon adsorbed with saturated VOCs (i.e., styrene) has a complicated composition, and its recycling and reuse have become a major global concern due to the catastrophic environmental damage that wrong treatment may create. Here, we show a simple, green, and low-energy solvent-free method to prepare N-doped porous carbocatalysts for selective oxidation of H2S by direct carbonization of waste-activated carbon adsorbed with saturated VOCs mixed with melamine. The as-synthesized catalysts (N@AC-T) have high specific surface areas and a significant number of active pyridinic N sites. The optimized N-doped carbon (N@AC-700) catalyst exhibits competitive H2S selective oxidation activity (H2S conversion of 96.2% and sulfur formation rate of 225 gsulfur·kgcat.–1·h–1 at 190 °C) and superior stability (around 50 h) and water vapor resistance. Furthermore, the monolithic carbon catalysts prepared by using a biomass binder also present excellent desulfurization performance (H2S conversion >90% at 190 °C). The excellent catalytic performance was shown by a series of characterization results to be related to the combined effect of specific surface areas and the pyridinic N active sites. This work aims to design and prepare efficient N-doped carbon desulfurization catalysts for high potential industrial applications by rationally recycling and reusing waste carbon through a green and nonpolluting solvent-free method.