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Supported Vanadia Catalysts with Alkali and Alkaline Earth Additives in Oxidative Dehydrogenation of Propane. Part II. V2O5/SiO2 System

Klisińska A., Gressel I., Grzybowska B., Mikołajczyk M., Stoch J.

Polish Journal of Chemistry

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2006

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Vol. 80, nr 5

835-842

EN

Alkali metals (Li, Na, K, Rb) and Ca were introduced to vanadia dispersed on magnesia: the catalysts obtained were characterized by XRD, XPS isopropanol decomposition (a probe of acido-basic properties) and tested in oxidative dehydrogenation of propane, ODH. No vanadia phase was observed by XRD, vanadium being most probably present in the samples as magnesium orthovanadate dispersed on the MgO surface. Low concentration of acidic and high of basic centres have been observed in the catalysts. Selectivity to propene does not exceed 40%, andCO2 is themain product of total oxidation. The presence of the additives leads to: a) decrease of the acidity and increase the basicity, b) decrease of the total activity in ODH, c) decrease in the selectivity to propene (except for the Ca additive). The effect of additives to VMg catalysts is compared with that reported in Part I for VSi catalysts, and reasons for opposite effect of the additives on the selectivity to propene (increase for VSi and decrease for VMg series) are suggested.

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Supported Vanadia Catalysts with Alkali and Alkaline Earth Additives in Oxidative Dehydrogenation of Propane. Part I. V2O5/SiO2 System

Klisińska A., Gressel I., Grzybowska B., Mikołajczyk M., Stoch J.

Polish Journal of Chemistry

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2006

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Vol. 80, nr 5

825-833

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Effect of Additives to VPO System on Its Catalytic Properties in Oxidative Dehydrogenation of Propane and Ethane

Gąsior M., Gressel I., Zazhigalov V. A., Grzybowska B.

Polish Journal of Chemistry

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2003

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Vol. 77 / nr 7

909-915

EN

Oxidative dehydrogenation (ODH) of propane and ethane has been studied on VPO catalysts with additives of Bi, La, Mo and Zr. The catalysts show promising properties in the ethane ODH, with selectivities to ethene of ~85% at 10% conversion of ethane, but are poor in the propane ODH (maximal selectivities to propene of ~40%). For both alkanes introduction of the additives leads to an increase in the overall rate of the reaction. The effect of the additives on the selectivity to olefins is complex and depends on the reaction temperature, the additive content and the type of alkane. The same additive has in several cases an inverse effect on the selectivity for the propane and ethane ODH. The Mo additive and higher amounts of the La additive increase the selectivity to propene, whereas they decrease the selectivity to ethene. Low content of La additive gives rise to the increase of selectivity to ethene and decrease in that to propene. The differences between the selectivities to olefins in ODH of propane and ethane are discussed as being due to different acido-basic properties of the propene and ethene and their different strength of bonding to the catalyst surface.