Kinetics of oxidative dehydrogenation of propane and ethane on VOx/SiO2 pure and with potassium additive

Application of Eley-Rideal steady-state model (ER-SSAM) for the description of oxidative dehydrogenation (ODH) of ethane/propane over vanadia-silica catalyst doped by potassium and undoped, using an extensive set of the experimental data was studied. It has been shown for a broad range of feed mixture, contact time and temperature that the model which take into account the adsorption of water on the surface (ER-SSAM II) of the catalysts describes more adequately (less fitting error) the kinetics of the studied reaction than the model, which neglects this effect. Kinetic constants (activation energies, pre-exponential factors) for both applied models of ODH reaction of ethane/propane on these catalysts, obtained on the bases of steady-state results, are given. Potassium exhibits strong inhibitory effect on the consecutive propene and parallel propane combustion and has lower influence on ethene and ethane combustion. The secondary combustion is the main source of carbon oxides in studied reaction and potassium additive modifies the catalytic properties of these catalysts by blocking active centers on the surface of the catalysts (decreasing pre-exponential factors). The re-oxidation rate constant for doped and undoped catalyst is almost not influenced by potassium addition.