Kinetics of contracting geometry-type reactions in the solid state: implications from the thermally induced transformation processes of α-oxalic acid dihydrate.

This study focuses on the physico-geometrical constraints of the kinetics of the thermal decomposition of solids as exemplified by the thermal dehydration of α-oxalic acid dihydrate and the subsequent thermally induced sublimation/decomposition of the as-produced anhydride using the samples of crystalline particles (CPs) and a single crystal (SC) form. The CP and SC samples possess approximately similar geometrical figures with different sizes. The shapes of the original dihydrate and the as-produced anhydride from thermal dehydration are practically congruent.

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

This study aims to establish an advanced kinetic theory for reactions in solid state and solid-gas systems, achieving a universal kinetic description over a range of temperature and partial pressure of reactant or product gases. The thermal decomposition of Mg(OH)2 to MgO was selected as a model reaction system, and the effect of water vapor pressure p(H2O) on the kinetics was investigated via humidity controlled thermogravimetry. The reaction rate of the thermal decomposition process at a constant temperature was systematically decreased by increasing the p(H2O) value, accompanied by an increase in the sigmoidal feature of mass-loss curves.

Impact of atmospheric water vapor on the thermal decomposition of calcium hydroxide: a universal kinetic approach to a physico-geometrical consecutive reaction in solid-gas systems under different partial pressures of product gas.

Thermal decomposition of Ca(OH)2 under atmospheric water vapor exhibits special features, including an induction period (IP) and a subsequent sigmoidal mass-loss behavior under isothermal conditions. Atmospheric water vapor reduces the reaction rate at a specific temperature and causes a systematic shift of the mass-loss curve, which was recorded at a specific heating rate, to higher temperatures as the water vapor pressure, p(H2O), increases. The challenge in this study was to universally describe the kinetics of thermal decomposition under various p(H2O) conditions by introducing an accommodation function in the fundamental kinetic equation.

Thermally induced carbonation of Ca(OH) in a CO atmosphere: kinetic simulation of overlapping mass-loss and mass-gain processes in a solid-gas system.

Thermally induced carbonation of Ca(OH) in a CO atmosphere is a reaction exhibiting particular features, including stoichiometric completeness to form CaCO and a kinetic advantage over the carbonation of CaO particles. This study aims to gain further insight into the reaction mechanisms of CO capture by Ca(OH) and CaO. It focuses on the kinetic modeling of the carbonation of Ca(OH) as a consecutive reaction in a solid-gas system.