Product selectivity and reaction pathways for H2S catalytic oxidation over Fe- and Al-modified catalyst

This study used metal oxide-modified metal-organic frameworks to examine H 2 S catalytic oxidation selectivity. The findings revealed that the oxidation mechanisms and products differed between Fe 2 O 3 /UiO-66 and Al 2 O 3 /UiO-66. The dithionates were intermediate products of H 2 S oxidation on Al 2 O 3 /UiO-66, whereas the bisulfates were intermediate products on Fe 2 O 3 /UiO-66. Fe 2 O 3 /UiO-66 showed stronger surface oxidation activity than Al 2 O 3 /UiO-66. The formation of sulfate/SO 2 was primarily attributable to surface oxygen, whereas elemental sulfur was primarily related to lattice oxygen. The product generation processes of H 2 S on Fe 2 O 3 /UiO-66 and Al 2 O 3 /UiO-66 surfaces were as follows: H 2 S → HSO 4 2− → SO 2 → S for Fe 2 O 3 /UiO-66, while H 2 S → S 2 O 4 2− → SO 2 for Al 2 O 3 /UiO-66. H 2 O and surface oxygen have the potential to alter H 2 S adsorption on the catalyst surface. For Fe 2 O 3 , the conversion of H 2 S to SO 2 involves both an oxidation process and a reduction process. For Al 2 O 3 , the conversion of H 2 S to SO 2 includes two oxidation processes. Due to the oxidation step of S 2 O 4 2− limiting the generation of SO 2 , the reduction process of SO 2 was also hindered, which in turn restricted the production of S over Al 2 O 3 . Fe 2 O 3 can achieve the oxidation and removal of H 2 S at lower reaction temperatures, while also creating elemental S.