Effect of Aluminum Addition and Surface Moisture Content on the Catalytic Activity of Sulfated Zirconia in n-Butane Isomerization
2019
Wang, Pengzhao | Wang, Siqi | Yang, Chaohe | Li, Chunyi | Bao, Xiaojun
The effects of aluminum addition and surface moisture on the surface-structure properties and catalytic activity of sulfated zirconia were investigated in n-butane isomerization. Adding 4 mol % Al into zirconia support with coprecipitation method greatly improves the catalytic activity. This is attributed to the monolayer coverage of sulfate species and the maximum of Brønsted acid sites, resulting from the strongly stabilized sulfate species on the tetragonal zirconia (t-ZrO₂) surface. The in situ DRIFTS investigations and density functional theory (DFT) calculations show that the dehydration temperature affects both the density and the strength of Brønsted acid sites, and there is a balance between them. The optimal catalytic activity is reached with complete desorption of physical adsorbed water and partial desorption of surface hydroxyl groups. The strongly stabilized sulfate species on appropriately dehydrated surface of t-ZrO₂ provide the superacidity and the strong oxidizing ability via a strong electron-withdrawing effect of S═O bonds.
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