Theoretical investigation of H₂S removal on γ-Al₂O₃ surfaces of different hydroxyl coverage

Abstract

The sulfurized processes of H 2 S on dehydrated (100) and (110) as well as partially hydrated (110) surfaces of g-Al 2 O 3 were investigated using a periodic density functional theory method. The adsorption configurations of possible intermediates and the potential energy profiles of reaction are depicted. Our results show that H 2 S adsorbs preferentially on the Al site along with the S bond, and the adsorption energies are À32.52 and À114.38 kJ mol À1 on the dehydrated (100) and (110) surfaces, respectively. As the reaction temperature of the desulfurization changes, the (110) surface presents different levels of hydroxyl coverage, which affects the adsorption structures of species and reaction energies of dissociation processes. The bonding strengths of H 2 S on the partially hydrated (110) surfaces are weaker than on the dehydrated (110) surface. Compared with the 3.0 and 8.9 OH per nm 2 surfaces, the H 2 S has the weakest adsorption energy (À39.85 kJ mol À1 ) and the highest activation energy (92.06 kJ mol À1 ) on the 5.9 OH per nm 2 surface. On the 8.9 OH per nm 2 surface, the activation energy of the second dissociation step (rate-determining step) for H 2 S dissociation is merely 38.32 kJ mol À1 . On these involved surfaces, cleavage processes of the two H-S bonds present facile activation energies, which are facilitative to desulfurization. View Article Onlinea Param: parameters. b D100, the dehydrated g-Al 2 O 3 (100) surface. c D110, the dehydrated g-Al 2 O 3 (110) surface. d FS denotes the nal state. e 3.0 OH per nm 2 , 5.9 OH per nm 2 and 8.9 OH per nm 2 represent the different levels of hydroxyl coverage for g-Al 2 O 3 (110) surface. This journal isFig. 6 Calculated probable potential energy profiles for dissociation of H 2 S (a) and HS (b) on dehydrated and partially hydrated g-Al 2 O 3 surfaces. (D100 surface, the dehydrated g-Al 2 O 3 (100) surface; D110 surface, the dehydrated g-Al 2 O 3 (110) surface).This journal is

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