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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

2006

Vol. 80, nr 5

825-833

Potassium Effects on Kinetics of Propane Oxydehydrogenation on Vanadia-Titania Catalyst

Grabowski R., Samson K.

Polish Journal of Chemistry

2003

Vol. 77 / nr 4

459-470

Oxidative dehydrogenation of propane (ODH) over V2O5/TiO2 and V2O5/TiO2 doped with K was carried out by measuring conversions and selectivities for various feed compositions, contact times and temperatures. The results obtained for both catalysts were interpreted on the basis of the mechanism, in which propene is formed through Eley-Rideal sequence of steps, i.e. without participation of the adsorbed propane species. Kinetic constants (activation energies, pre-exponential factors) for the model ofODHreaction of propane on these catalysts, obtained on the basis of steady-state results, are given. Addition of K to vanadia-titania catalysts leads to the decrease of total combustion of propane and consecutive combustion of propene. It has been found that the direct propane total oxidation is 5_9 times lower than that of the consecutive propene oxidation and is almost temperature independent for potassium doped catalyst, whereas it quickly decreases with temperature for a non-doped catalyst. Secondly, the addition of K to a vanadia-titania catalyst decreases the activation energies for propene formation (k1), parallel formation of COx (k3) and reoxidation of the catalyst (kOS). Potassium exhibits a stronger inhibitory effect on the secondary propene combustion, what reflects the lower acidity of V+5 cations modified by the strongly basic alkali oxide species.

Effect of the Potassium Promoter Content in V2O5/TiO2 Catalysts on Their Physicochemical and Catalytic Properties in Oxidative Dehydrogenation of Propane

Grzybowska B.

Polish Journal of Chemistry

2001

Vol. 75, nr 10

1513-1519

To optimize the content of the potassium promoter in V2O5/TiO2 system for oxidative dehydrogenation of propane ODH, the vanadia-titania catalysts of the potassium/vanadium (K/V) ratio ranging from 0.01 to 0.2 were obtained and tested in the title reaction. It has been found that the total rate of the propane consumption decreases considerably already on addition of small amounts of K (K/V = 0.01) to vanadia-titania system and only slightly at higher K content: its value is constant beginning from K/V = 0.05. The distinct increase in the selectivity to propene on addition of K is, on the other hand, observed at higher K content (K/V = 0.05-0.1). Addition of K to vanadia-titania catalysts leads to the decrease in acidity and increase in basicity of the system, as shown by measurements of the isopropanol decomposition, a probe reaction of acido-basic properties.