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

100%

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

tom Vol. 77 / nr 7

909-915

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.

Surface acidity of VPO catalysts

88%

Grinenko S. , Stoch J. , Podobiński J. , Zazhigalov V. A. , Mikołajczyk M.

Bulletin of the Polish Academy of Sciences. Chemistry

2000

tom Vol. 48, No. 2

145-151

In the study of vanadium-phosphorus catalysts and related substances with the TPD/QMS of ammonia the higher resolution spectra have been obtained. They show the presence at the catalysts surface of two well resolved bands of weakly bonded ammonia (120-140° C) tentatively assigned to two kinds of surface phosphate groups of different acidity and the band of much stronger bonded ammonia (200° C) assigned to vanadate groups. Introduction of bismuth atoms increases the number of active phosphate groups and the strength of their acid function. The effect of lanthanum additives is opposite.