Significant impact of γ-Al2O3 facet structure on the character and performance of surface Co-Mo sulfides for CO removal in H2 fuel via water gas shift

Three morphologically uniform gamma-Al2O3 crystallites [Al2O3 hexagonal plates (Al2O3-HP), stacked hexagonal plates (Al2O3-SHP) and rods (Al2O3-R)] were controllably synthesized. The Co-Mo oxide precursor was loaded on these gamma-Al2O3 substrates via aqueous incipient wetness impregnation and transformed to the sulfides under 10% H2S/H-2 (v/v) atmosphere. The mainly exposed facet of Al2O3-HP and Al2O3-SHP was identified to be the (1 1 0) and (10 0)/(1 1 1), respectively; whereas a polycrystalline structure was observed over Al2O3-R. The original structural feature of oxide precursors, i.e., 2D polymeric/monomeric as well as 3D polymeric/MoO3 species substantially varied over Al2O3-HP, Al2O3-SHP, and Al2O3-R, which in turn determines the effectiveness in sulfidation of surface oxide precursors. The richness of MoS2/Co9S8/Co-Mo-S species, and less fraction of partially sulphurated CoMoOxS2 as well as CoOx/SOx2- entities were recognized over Al2O3-HP. Based on the areal activity at 250 degrees C, the sulfides-Al2O3 (1 1 0) interface is approximately 6-13.8 times more active than the poly-crystalline or commercial gamma-Al2O3 supported sulfides for water gas shift (WGS) in a hydrogen-rich stream. The sulfides-Al2O3 (110) interface also notably outperformed the sulfides-Al2O3 (10 0)/(1 1 1) interfaces for the reaction.