Kinetics and mechanisms of the thermal decomposition of copper(II) hydroxide under different water vapour pressures
Résumé
Thermal decomposition of Cu(OH)2 exhibits specific physico-geometric kinetic characteristics involving the significant induction period (IP) and subsequent sigmoidal mass-loss behaviour under isothermal conditions and the two-step mass-loss process with a long lasting reaction tail under linearly increasing temperature conditions. In addition, the rate behaviours of IP and mass-loss process are largely influenced by the environmental water vapour pressure, p(H20). The IP at a constant temperature is prolonged with increasing p(H20). The mass-loss curves shift systematically to higher temperatures with increasing p(H20). Therefore, the kinetic approach to this complex reaction requires the detailed considerations of the mechanistic features and the impact of p(H20).
For the universal kinetic approach to each kinetic process under different p(H20), an accommodation function with respect to p(H20) was derived: cf. file abstract. The accommodation function a(p(H20), Peq(T)) can be introduced into different kinetic equations for describing the IP and mass-loss process. The IP at different temperatures and under different p(H20) analysed kinetically by a single Arrhenius-type plot, providing a statistically significant linearity and the activation energy Ea,IP = 243 ± 13 kJ mol-1. Similarly, a(p(H20), Peq(T)) is introduced into the isoconversional kinetic equation for analyzing universally the mass-loss process under different temperature conditions and p(H20). The isoconversional plots applied to the major mass-loss step of the thermal decomposition of Cu(OH)2 represent straight lines and the average Ea,l = 148 ± 1 kJ mol-l (Fig. 1) (cf. file abstract). Furthermore, the overall thermal decomposition of Cu(OH)2 under isothermal conditions can be described by the IP-surface reaction (SR)-phase boundary controlled reaction (PBR) model. The rate constants of each component reaction step determined under different p(H20) are subjected to the Arrhenius plot by considering a(p(H20), Peq(T)).
Domaines
Génie des procédésOrigine | Fichiers produits par l'(les) auteur(s) |
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