Catalytic Activity of Rare Earth-Promoted SO42-/SnO2in the Oxidative Dehydrogenation of Ethylbenzene

Rare earth-promoted (10%) sulfated SnO2 catalysts were prepared by different methods and have been characterized by employing XRD, SEM, Mercury porosimetry, BET surface-area analysis, TG-DTA, and IR spectroscopy. The strength of generated acid sites depends on the preparation method. A thermogravimetric analysis revealed that the removing the sulfate species from the catalyst surface took place at temperatures > 1193 K. The adsorption of butylamine and acetic acid was used to probe the acid-base properties of the catalysts. The catalytic activity of these materials in the oxidative dehydrogenation of ethylbenzene was tested at different temperatures. It was found that rare earth-modified sulfated tin oxide catalysts are more active when compared to the corresponding mixed-oxide systems and sulfated tin oxide. The combined effect of rare earth oxide and the sulfate anion leads to a enhanced oxidation activity. The existence of strong acid sites generated as a result of a sulfate treatment is involved in the activation of ethylbenzene; the addition of rare earth oxides brings about an enhancement of the reaction between the adsorbed oxygen atoms and the adsorbed ethylbenzene.