Ca-Cu/Al2O3 catalysts for H2S removal at near ambient temperature: Synthesis, characterization, DFT calculation, and mechanistic insights

Abstract

A series of Ca-doped CuxO/Al2O3 catalysts were developed using the excessive impregnation method for H2S catalytic oxidation at near-ambient temperatures. Ca(NO3)-CuxO/Al2O3 catalyst with 2.5 wt% Ca exhibited optimal H2S desulfurization performance at 60 °C and RH 60%, achieving an H2S removal capacity of 401.34 mg/g. Experimental, characterization, and DFT calculation results demonstrate that during the catalytic oxidation of H2S, H2O can be catalytically convert into ·OH while simultaneously capturing and dissociating H2S. The ·OH and NO3- then catalyze the oxidation of HS-/S2- to elemental S. Moreover, the redundant OH adsorbed on the basic sites can buffer the pH and promote the dissociation of H2S. The above cyclic process could alleviate the deactivation of the Ca-Cu/Al2O3 catalyst. Therefore, a ·OH-induced desulfurization mechanism assisted with Ca2+ buffer the pH and NO3- cyclic oxidation of H2S has been proposed. This work contributes to the preparation of high-capacity mental-based catalysts for H2S oxidation.