Graphic determination of kinetic parameters in temperature-programmed desorption of oxygen from alumina-supported PdO

A graphic method is proposed to determine all of the kinetic parameters in Wigner-Polanyi equation of desorption. A desorption rate curve from a single temperature-programmed desorption experiment is required by this method to determine the order of reaction (n), the activation energy (E(d)) and the pre-exponential factor (v) of the equation. The proposed method has been applied to the oxygen desorption from PdO/Al2O3 samples prepared by impregnating gamma-Al2O3 with H2PdCl4 solution used as examples. From the graphic method, the values of n = 2, and v = 1.37 +/- 0.80 x 10(9) s(-1) were successfully determined for the desorption. The value of Ed depended on the dispersion of palladium (D) on PdO/Al2O3 samples, and was expressed by the equation: E(d) = 175 + 174D kJ . mol(-1). This graphic method is a direct and time-saving technique, on comparing with other methods suggested in the literature, for analysis of data from temperature-programmed desorption of simple desorption processes.