Physico-Geometrical Mechanism and Overall Kinetics of Thermally Induced Oxidative Decomposition of Tin(II) Oxalate in Air: Formation Process of Microstructural Tin(IV) Oxide

Abstract

This study focuses on the physico-geometrical mechanism and the overall kinetics of the microstructural tin(IV) oxide formation process by the thermally induced oxidative decomposition of tin(II) oxalate in flowing air. Two tin(II) oxalate samples with different morphologies were subjected to a kinetic study involving thermogravimetrical and morphological observations. The reactions exhibited different behaviors at different steps (multistep behaviors); therefore, the overall reactions were resolved into each reaction step using kinetic analyses based on the cumulative kinetic equation. Oxidative decomposition is characterized by a phase boundary controlled reaction initiated by the surface reaction. The formation of the surface product layer at an early stage of the reaction inhibits diffusion of the product and reactant gases. Gaseous diffusion channels are produced via reformulation of the surface product layer by the reaction itself, and the residual reaction advances in the manner of autocatalytic reaction. The kinetic behavior is regulated by the self-generated reaction conditions under specific, transiently formed structural characteristics of the reacting particles, which vary depending on the applied reaction conditions. Therefore, the process control of the oxidative decomposition is an important factor for controlling the microstructure and physicochemical properties of the resulting tin(IV) oxide.

Thermal Decomposition of Tin(II) Oxyhydroxide and Subsequent Oxidation in Air: Kinetic Deconvolution of Overlapping Heterogeneous Processes

“…From the slopes of the plots, the E a values for the thermal dehydration−decomposition and oxidation processes were determined to be 93.2 ± 3.2 and 115.1 ± 4.8 kJ mol −1 , respectively. Assuming partial overlap of the kinetically independent processes, the overall rate behavior can be expressed by the sum of the kinetic equations of the two component processes: 42 …”

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

“…The physico-geometrical consecutive process comprising the initial SR and subsequent PBR, i.e., the Mampel-type model, is a possible explanation for the sigmoidal mass-loss behavior. 41,42,44,[46][47][48]65,[92][93][94][95][96][97] In the scheme of the consecutive SR-PBR model, the variation in the mechanistic feature with the p(H2O) value, as appearing in the sigmoidal shape of the mass-loss curves, is…”

Kinetic analysis of overlapping multistep thermal decomposition comprising exothermic and endothermic processes: thermolysis of ammonium dinitramide

“…13 Furthermore, a great deal of experimental effort has recently been focused on finding rigorous kinetic solutions based on the physico-chemistry and physico-geometry of heterogeneous multistep processes. 7,[14][15][16][17][18][19] Considering the thermoanalytical approaches to heterogeneous multistep reactions, further complications are introduced when the overall reaction comprises partially overlapping processes with oppositely signed thermoanalytical signals, e.g., mass loss and mass gain [20][21][22] or exothermic and endothermic events. 23 When two overlapping mass-loss processes indicate endothermic and exothermic effects, respectively, the apparent kinetic data recorded using differential scanning calorimetry (DSC) are different from those recorded with thermogravimetry (TG), as has been shown for isopropylammonium nitrate decomposition.…”