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 (Ed) 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 γ-Al2O3 with H2PdCl4 solution used as examples. From the graphic method, the values ofn=2, andv=1.37±0.80×109 s−1 were successfully determined for the desorption. The value ofEd depended on the dispersion of palladium (D) on PdO/Al2O3 samples, and was expressed by the equation:Ed=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.
Authors:J.-M. Tseng, M.-Y. Liu, S.-L. Chen, W.-T. Hwang, J.-P. Gupta, and C.-M. Shu
Methyl ethyl ketone peroxide (MEKPO) is an unstable material above certain limits of temperature, decomposing into chain reactions
by radicals. The influence of runaway reactions on this basic characteristic was assessed by evaluating kinetic parameters,
such as activation energy (Ea), frequency factor (A), etc., by thermal activity monitor III (TAM III). This was done under three isothermal conditions of 70, 80, and 90 °C,
with MEKPO 31 mass% combined with nitric acid (HNO3 6 N) and sodium nitrate (NaNO3 6 N). Nitric acid mixed with MEKPO gave the maximum heat of reaction (△Hd) and also induced serious reactions in the initial stage of exothermic process under the three isothermal temperatures. The
time to maximum rate (TMR) also decreased when HNO3 was mixed with MEKPO. Thus, MEKPO combined with HNO3 6 N forms a very hazardous mixture. Results of this study will be provided to relevant plants for alerting their staff on
adopting best practices in emergency response or accident control.