Kinetic parameters, decomposition, single

The decomposition of dolomite shows many points of similarity with the reactions of calcite and of other single carbonates of Group IIA metals (Sects. 3.1.1 and 3.1.2) the reaction is reversible, occurs at an interface, and both apparent kinetic parameters and reactivity are influenced by the prevailing C02 pressure. 

Kinetic parameters of fast pyrolysis were derived while assuming a single process for the decomposition of wood, including three parallel first-order decay reactions for the formation of the product classes. This is the so-called Shafizadeh scheme [56]. The three lumped product classes are permanent gas, liquids (biooil, tar), and char a classification that has become standard over the years. The produced vapors are subject to further degradation to gases, water and refractory tars. Charcoal, which is also being formed, catalyzes this reaction and therefore needs to be removed quickly [57]. 

Decomposition acetic acid, 29 35-36 single crystals, kinetic parameters, 29 2S-29... 

Kinetic Parameters for the Decomposition of HCOOD or HCOOH on Single Crystal Surfaces... 

Temperature-programmed DSC, or DTA measurements, can only suggest the autocatalytic nature of the decomposition. Neither the influence of the thermal history and contamination can be detected by them, nor can the kinetic parameters be determined from a single experiment. 

The most common initiation or homolysis reaction is the breaking of a covalent C-C bond with the formation of two radicals. This initiation process is highly sensitive to the stability of the formed radicals. Its activation energy is equal to the bond dissociation enthalpy because the reverse, radical-radical recombination reaction is so exothermic that it does not require activation energy. C-C bonds are usually weaker than the C-H bonds. Thus, the initial formation of H radicals can be ignored. The total radical concentration in the reacting system is controlled both by these radical initiation reactions and by the termination or radical recombination reactions. In accordance with Benson (1960), the rate constant expressions of these unimolecular decompositions are calculated from the reverse reaction, the recombination of two radical species to form the stable parent compound, and microscopic reversibility (Curran et al., 1998). The reference kinetic parameters for the unimolecular decomposition reactions of K-alkanes for each single fission of a C-C bond between secondary... 

A comparison of the kinetic parameters for the thermal decomposition of 2, 2 -azobis(isobutyronitrile) (AIBN) obtained by different DSC methods is given in Table 5.14 (184). The ASTM E-698 method is a modification of the Ozawa method (181), whereas the single scan DSC method is that described by Prime (182, 183). 

In this study, only the first two stages (i.e., heating and decomposition) are considered. Moreover, one single Arrhenius equation is assumed in the decomposition process with one set of kinetic parameters, as described in Chapter 4. 

The time, temperature and temperature-rate data collected from the exothermic decomposition of materials in adiabatic calorimeters such as adiabatic Dewars or ARC are handled by a single-step A B reaction model. Townsend and Tou 2 first introduced this model as a means of obtaining safety limits and simple kinetic parameters from such adiabatic data. 

The broad variation in the kinetic parameters of decomposition (see Table 10) is essentially due to two reasons differences in PO characteristics (MW, presence of weak links, impurities, etc.), and differences in experimental conditions for which kinetic parameters were evaluated. In particular a single step model is not able to cover, using the same kinetic parameters, a wide range of heating rates, temperatures, and conversion levels. It has been established that the reaction order is equal to 1 and decreases with the aging time of the waste [388]. 

On the basis of a single TG curve using Eqs. (22.9-22.12), the values of the apparent activation energy E and the pre-exponential factor A were calculated, as well as the most probable reaction mechanism functions were determined. For comparison, the best kinetic parameters, characterizing the three (I, II, and III) stages of thermal decomposition of CaC O H O obtained at different heating rates and sample masses by the Coats—Redfern calculation procedure are presented in Table 22.6. 

Kinetic studies have traditionally been extremely useful in characterizing several physical and chemical phenomena in organic, inorganic and metallic systems. It provides valuable qualitative, quantitative and kinetic information on phase transformations, solid state precipitation, crystallization, oxidation and decomposition. Unfortunately, no single reference comprehensively presents non-isothermal kinetic analysis method for the study of complex processes, determining the actual mechanism and kinetic parameters. This book provides a new method for non-isothermal kinetics and its application in heterogeneous solid state processes. In the backdrop of limitations in existing methods, this book presents a brief review of the widely used isothermal and non-isothermal kinetic analysis methods. 

The retarding influence of the product barrier in many solid—solid interactions is a rate-controlling factor that is not usually apparent in the decompositions of single solids. However, even where diffusion control operates, this is often in addition to, and in conjunction with, geometric factors (i.e. changes in reaction interfacial area with a) and kinetic equations based on contributions from both sources are discussed in Chap. 3, Sect. 3.3. As in the decompositions of single solids, reaction rate coefficients (and the shapes of a—time curves) for solid + solid reactions are sensitive to sizes, shapes and, here, also on the relative dispositions of the components of the reactant mixture. Inevitably as the number of different crystalline components present initially is increased, the number of variables requiring specification to define the reactant completely rises the parameters concerned are mentioned in Table 17. 

As with the decompositions of single solids, rate data for reactions between solids may be tested for obedience to the predictions of appropriate kinetic expressions. From the identification of a satisfactory representation for the reaction, the rate-limiting step or process may be identified and this observation usually contributes to the formulation of a reaction mechanism. It was pointed out in Sect. 1, however, that the number of parameters which must be measured to define completely all contributory reactions rises with the number of participating phases. The difficulties of kinetic analyses are thereby also markedly increased and the factors which have to be considered in the interpretation of rate data include the following. 

The effectiveness of incineration has most commonly been estimated from the heating value of the fuel, a parameter that has little to do with the rate or mechanism of destraction. Alternative ways to assess the effectiveness of incineration destraction of various constituents of a hazardous waste stream have been proposed, such as assessment methods based on the kinetics of thermal decomposition of the constituents or on the susceptibility of individual constituents to free-radical attack. Laboratory studies of waste incineration have demonstrated that no single ranking procedure is appropriate for all incinerator conditions. For example, acceptably low levels of some test compounds, such as methylene chloride, have proved difficult to achieve because these compounds are formed in the flame from other chemical species. 

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