Pyrosulfate

Abstract: Catalytic activation and conversion of light alkanes by sulfated zirconia is unequivocally shown to be initiated by producing small concentrations of olefins. This occurs via stoichiometric oxidative dehydrogenation of butane by SO3 or pyrosulfate groups to butene (present mostly as alkoxy groups), water, and SO2. Thermal desorption and in situ IR spectroscopy have been used to determine all three reaction products. The concentration of butene formed determines both the catalytic activity of sulfated zirconia as well as the deactivation via formation of oligomers. The thermodynamics of the oxidative dehydrogenation of n-butane by different SZ surface structures has been examined by density functional (DFT) calculations. The calculations show that pyrosulfate or re-adsorbed SO3 species have the highest oxidizing ability.

Abstract: In the present study, we have examined sulfation of cerium oxide via impregnation of (NH4)2SO4, followed by heating in the temperature range of 220–720°C, using Raman Spectroscopy. Based on the S O and S O stretching frequencies in the range of 900–1400 cm−1, a wide range of surface oxysulfur species and bulk cerium-oxy-sulfur species are identified. At 220°C, a mixture of (NH4)2SO4 crystals, SO2−4(aq) and HSO1−r(aq) is found to have formed on ceria's surface, whereas complete conversion of (NH4)2SO4 to SO2−4(aq) and HSO1−4(aq) occurs at 280°C. At 350°C, formation of a mixture of surface pyrosulfate S2O2−7(surf.0, consisting of two S O oscillators and a bulk type compound identified as Ce(IV)(SO4)x(SO3)2−x (0