Non-isothermal kinetic study of the solid-gas thermal decompositions of some coordination compounds of CoII and NiII

Using a method developed by us, a non-isothermal kinetic study of the thermal decomposition of some coordination compounds (CC) with the general formula Me^IIL_pX₂, where

, was performed.     

On the maximum reaction rate and inflexion points on the DTG curve

The authors present some theoretical considerations concerning the influence of the form of the conversion functionf() on the values of the degree of conversion corresponding to the maximum value of the reaction rate (_max) as well as on the inflexion points (_inf) of the DTG curve. The obtained equations are characterized by a general validity no matter the form off().

---

Zusammenfassung Es werden einige theoretische Überlegungen bezüglich des Einflusses der Form der Konversionsfunktionf() auf die Werte der Konversionsrate bei maximalen Reaktionsgeschwindigkeiten (_max) sowie auf Inflexionspunkte () der DTG-Kurve angestellt. Die erhaltenen Gleichungen sind unabhängig von der Form vonf() durch eine all-gemeine Gültigkeit charakterisiert.

     

Improved Iterative Version of the Coats-Redfern Method to Evaluate Non-Isothermal Kinetic Parameters

An improved version of the Coats-Redfern method of evaluating non-isothermal kinetic parameters is presented. The Coats-Redfern approximation of the temperature integral is replaced by a third-degree rational approximation, which is much more accurate. The kinetic parameters are evaluated iteratively by linear regression and, besides the correlation coefficient, the F test is suggested as a supplementary statistical criterion for selecting the most probable mechanism function. For applications, both non-isothermal data obtained by theoretical simulation and experimental data taken from the literature for the non-isothermal dehydration of Mg(OH)₂ have been processed.This revised version was published online in November 2005 with corrections to the Cover Date.     

General Kinetic Equation for Solid State Reactions

A general kinetic equation is suggested in order to describe solid state decompositions or, more generally, solid state reactions and transformations on the basis of some existing general equations. This differential equation can be expressed as: dα/dt=k[(1-α)^q]^x{[1-(1-α)^1−q]/(1-q)}^y, where α represents the degree of conversion, k is the rate constant while q, x and y are characteristic parameters for a given mechanism. This revised version was published online in July 2006 with corrections to the Cover Date.     

The heating rate as a variable in non-isothermal kinetics. A new method to evaluate the nonisothermal kinetic parameters

The heat exchange calorimetry, hitherto developed for ordinary size samples, was modified for diminishing the sample size to one tenth or less of that commonly used in previous reports. Improvements were made with respect to the vessels for sample and reference, the stirrer of the sample solution, the thermistor and the calibration heater. The value of α, a constant relating to the heat transfer and critically affecting the sensitivity to smaller heat effects, was given an appropriately small value. The improved version of the calorimeter employed a sample vessel of a capacity of 6 cm³ and was suited to accomodate about 3 cm³ of a solution. The calorimeter proved to give sufficiently precise results when total heats ranging from 0.05 to 0.4 J were evolved.     

Integral dependent on parameter E in classical non-isothermal kinetics with linear heating rate

A simple procedure to obtain the derivative of the temperature integral with respect to the activation energy is presented.