Hierarchically porous γ-Al2O3 nanosheets: Facile template-free preparation and reaction mechanism for H2S selective oxidation

Abstract

A template-free strategy has been developed for the controlled synthesis of hierarchically porous γ-Al2O3 with three dimensional (3D) “cluster-like” architectures assembled from 2D nanosheets (∼15 nm thick). This unique structure endows the material with large active surface area, high accessibility and ready mass transport ability, capable of promoting the catalytic performance. As a result, the designed γ-Al2O3 exhibits high activity for selective oxidation of H2S to elemental sulfur. All the porous γ-Al2O3 samples show outstanding sulfur selectivity (∼100%) below 200 °C. At higher temperatures, the H2S conversion increases while the sulfur selectivity decreases. The maximum sulfur yield (93%) can be achieved over the optimal sample at 240 °C, which is much higher than those of commercial alumina and most of the reported alumina-based catalysts. The structure–activity relationship of the catalysts has been systematically studied. It is demonstrated that the surface acidity of the γ-Al2O3 has a great influence on catalytic activity. By means of pyridine and H2S in situ FTIR, the nature of the active sites as well as the reaction mechanism of H2S selective catalytic oxidation over γ-Al2O3 is revealed, providing important insights into the design of alumina-based materials for the removal of sulfur-containing compounds.