Universal Kinetic Description for Thermal Decomposition of Copper(II) Hydroxide over Different Water Vapor Pressures

Abstract

The impact that product gas in the reaction atmosphere has on the kinetics of the thermal decomposition of inorganic solids is an outstanding issue that requires a solution to understand the reactions in a solid−gas system. Among a variety of kinetic phenomena induced by atmospheric gas, the restraining effect of the overall reaction rate with increasing partial pressure of the product gas in the reaction atmosphere is the most widely observed phenomenon. In this study, we describe the universal kinetics of the thermal decomposition of solids over different temperatures and partial pressures of the gas, as exemplified by the thermal decomposition of Cu(OH) 2. Universal kinetic descriptions were enabled by introducing an accommodation function, with respect to atmospheric water vapor pressure, into the fundamental kinetic equation for solidstate reactions. The thermoanalytical curves as measured systematically under different temperatures and water vapor pressure conditions were kinetically analyzed in a step-by-step manner to attain kinetic modeling of the physico-geometrical consecutive process that comprises the induction period, surface reaction, and phase boundary-controlled reaction. The impact that atmospheric water vapor has on the kinetics of each physico-geometrical reaction step was separately evaluated using the universal kinetic approach.

Thermal Dehydration of Lithium Sulfate Monohydrate Revisited with Universal Kinetic Description over Different Temperatures and Atmospheric Water Vapor Pressures

“…However, the present study clearly indicates that the thermal dehydration of crystalline hydrates provides suitable model reactions for challenging the advanced kinetic understanding via the universal kinetic approach over different temperatures and partial pressures of the product gas, as well as for the thermal decomposition of metal hydroxides reported previously. [58][59] 4. Conclusions…”

“…Recently, we have succeeded in providing the desired universal kinetic description for a series of thermal decompositions of metal hydroxides. [58][59] The present study aims to provide the universal kinetic description in each physico-geometrical reaction step for the well-studied model reaction of the thermal dehydration of LSM, as a necessary step toward reaching a new level of kinetic understanding.…”

Revealing the effect of water vapor pressure on the kinetics of thermal decomposition of magnesium hydroxide

“…When the product gas presented in the reaction atmosphere causes a distinguishable effect on the reaction rate of the thermal decomposition, an accommodation function (AF) 7 is needed in the fundamental kinetic equation. 5,6,[8][9][10][11] For the simple thermal decomposition of a solid: A(s) ⇄ B(s) + C(g), the AF may be a function of partial pressure of the product gas p(C(g)) and the equilibrium pressure of the reaction Peq(T), i.e., a(p(C(g)),Peq(T)). The kinetic equation for the singlestep thermal decomposition of solids considering the p(C(g)) is thus expressed as: 9,10 (1)…”

“…If the universal kinetic description based on eqn (1) is achieved, further insight into the kinetics of the thermal decomposition of solids via the functional form of the AF and associated parameters can be gained, in addition to the conventional kinetic description via the so-called kinetic triplet, i.e., Ea, A, and f(α). 9,10 The success of the universal kinetic approach based on eqn (1) depends on the AF. The effect of p(C(g)) on the kinetics of thermal decomposition of solids has been investigated for nearly a century.…”

“…Recently, the effect of p(H2O) on the kinetics of thermal decomposition of divalent metal hydroxides exemplified by: M(OH)2(s) ⇄ MO(s) + H2O(g) were reexamined through theoretical considerations for finding the possible functional forms of AF. 9,10 In the theoretical considerations, the induction period (IP) and mass-loss process of the thermal decomposition were considered as consecutive processes of various elementary steps, based on the classical theories of surface nucleation and interface reaction, respectively. A series of differential kinetic equations for each reaction process were formulated based on the combined rate-limiting step and steady-state assumptions by selecting an elementary step from the consecutive process and assuming the other elementary steps were at equilibrium.…”