Kinetic parameters from calorimetry

The techniques referred to above (Sects. 1—3) may be operated for a sample heated in a constant temperature environment or under conditions of programmed temperature change. Very similar equipment can often be used differences normally reside in the temperature control of the reactant cell. Non-isothermal measurements of mass loss are termed thermogravimetry (TG), absorption or evolution of heat is differential scanning calorimetry (DSC), and measurement of the temperature difference between the sample and an inert reference substance is termed differential thermal analysis (DTA). These techniques can be used singly [33,76,174] or in combination and may include provision for EGA. Applications of non-isothermal measurements have ranged from the rapid qualitative estimation of reaction temperature to the quantitative determination of kinetic parameters [175—177]. The evaluation of kinetic parameters from non-isothermal data is dealt with in detail in Chap. 3.6. 

Evaluation of kinetic parameters from the synthesis of triaryl phosphates using reaction calorimetry. Organic Process Research af Development, 6,... 

Coats, A.W. Redfern J.P. (1964). Kinetic Parameters from Thermogravimetric Data, Nature (London), Vol. 201, pp. 68-69 ISSN 0028-0836 (Print), EISSN 1476 687 Criado, J.M. Sanchez-Jimenez, P.E. Perez-Maqueda, L.A. (2008). Journal of Thernml Analysis and Calorimetry, Vol. 92, pp. 199-203 ISSN 1388-6150 (Print), 1572-894 (electronic version)... 

In the following sections, the basic concepts of temperature-programmed methods (primarily temperature-programmed desorption, but also temperature-programmed reactions) are outlined. At the beginning, fundamental principles of adsorption and desorption—their thermodynamic and kinetic aspects, are presented. Furthermore, the descriptions of experimental setups, the data that can be obtained from the experiments and their interpretation are given. The possibilities to extract the adsorption energies and kinetic parameters from experimental results are discussed. Finally, the examples of possible applications and the comparison of results obtained by TPD with those obtained from adsorption calorimetry, are presented. 

Fig. 8.5 Hydrolysis of acetic anhydride investigated separately at Tr = 25°C (a) by calorimetry and (b) by infrared spectroscopy. Graph (a) shows measured and simulated reaction power graph (b) shows measured and simulated concentration-time curves of acetic anhydride. The simulated curve is from the kinetic parameters obtained from the calorimetric measurements, and is compared with the one determined by the IR measurements at 1139 cm-1. Reprinted in modified form with permission [18],...

The values of the kinetic parameters obtained from calorimetry measurements are collected in Table 3.3. 

The versatile nature of calorimeters, commercial and home-made, instruments allows direct access to the thermodynamic properties of materials being studied. Calorimetry is unintrusive in the way information is extracted during a study and highly versatile, measuring from nW to MW, from near absolute zero to several thousand kelvin. The sample studied can be in any phase or mixtures of phases and calorimetry can, in principle, be used to obtain all the thermodynamic and kinetic parameters relating to a reaction, and is limited only by the sensitivity of the instrument to detect a change. 

Glass transitions involve mainly the onset or freezing of cooperative, large-amplitude motion and can be studied using thermal analysis. Temperature-modulated calorimetry, TMC, is a new technique that permits to measure the apparent, fiequency-dependent heat capacity. The method is described and a quasi-isodiermal measurement method is used to derive kinetic parameters of the glass transitions of poly(ethylene terephthalate) and polystyrene. A first-order kinetics expression can describe the approach to equilibrium and points to the limits caused by asymmetry and cooperativity of the kinetics. Activation energies vary from 75 to 350 kJ/mol, dependent on thermal pretreatment. The preexponential factor is, however, correlated with the activation energy. 

Abstract. The Thermal Analsysis (TA) applies a great variety of techniques suitable for determining the thermophysical properties of solids. Here after a wide and detailed review on more conventional methods of differential thermal analysis (DTA) and differential scanning calorimetry (DSC) to study non-equilibrated materials, the experimental results obtained from Short-Range Ordering (SRO) in a Cu-Al alloys is presented and discussed. The kinetic parameters and laws in these materials are deeply discussed focusing attention also to vacancy behavior and effects of quenching conditions. 

The curing reactions of UPRs based on glycolyzed PET and maleic anhydride were studied by differential scanning calorimetry and various kinetic parameters were obtained from dynamic data using the Kissinger expression [59]. It was demonstrated that the polymerization heat, associated with styrene and polyester double bonds, can be calculated by extrapolating the heat of reaction obtained from different styrene contents. 

The detailed investigation of this process was done using two types of semi-IPNs made of cross-linked PU and linear PBMA [202]. The difference between these two cases is that in one case the previously polymerized PBMA was introduced into the reaction mixture for PU network formation, whereas in the other case the reactions of PU formation and BMA polymerization proceeded simultaneously. PU based on POPG and TDI-TMP adduct was formed under the action of dibutyltin laurate (catalyst). The kinetics of PU network formation and BMA polymerization were studied by calorimetry. The kinetic parameters of the reaction for pure PU and for PU in the presence of the second component were found from equation of the second-order reaction ... 

From the experimental kinetic data obtained by isothermal and adiabatic calorimetry, a technique for determining the kinetic and thermodynamic parameters for a somewhat simplified Scheme (8) has been developed. Table 2 presents thermodynamic parameters for two models and a real systems. 

In addition to these kinetic studies, there has been a considerable amount of work on the thermodynamic parameters associated with this type of reaction. Thus the interaction of [M(edta)aq] with anions of 8-hydroxyquinoline-5-sulfonic acid (oxs ), ida2- and nitrilotriace-tic acid (nta3-) was thoroughly studied for M = Y, La-Lu (except Pm) by calorimetry and pH titration,419 and AG, AH, AS and K found. Some of these values are given in Table 5. It was, however, concluded from the variation of these parameters with atomic number that all M3+ in aqueous solution have the same coordination number (nine) but that the coordination number of the [M(edta)aq] species changes between Sm3+ and Tb. ... 

As pointed out in Section 8.2, most physical and chemical processes, not just the chemical transformation of reactants into products, are accompanied by heat effects. Thus, if calorimetry is used as an analytical tool and such additional processes take place before, during, or after a chemical reaction, it is necessary to separate their effects from that of the chemical reaction in the measured heat-flow signals. In the following, we illustrate the basic principles involved in applying calorimetry combined with IR-ATR spectroscopy to the determination of kinetic and thermodynamic parameters of chemical reactions. We shall show how the combination of the two techniques provides extra information that helps in identifying processes additional to the chemical reaction which is the primary focus of the investigation. The hydrolysis of acetic anhydride is shown in Scheme 8.1, and the postulated pseudo-first-order kinetic model for the reaction carried out in 0.1 M aqueous hydrochloric acid is shown in Equation 8.22 ... 

A study of the relaxational transitions and related heat capacity anomalies for galactose and fructose has been described which employs calorimetric methods. The kinetics of solution oxidation of L-ascorbic acid have been studied using an isothermal microcalorimeter. Differential scanning calorimetry (DSC) has been used to measure solid state co-crystallization of sugar alcohols (xylitol, o-sorbitol and D-mannitol), and the thermal behaviour of anticoagulant heparins. Thermal measurements indicate a role for the structural transition from hydrated P-CD to dehydrated P-CD. Calorimetry was used to establish thermodynamic parameters for (1 1) complexation equilibrium of citric acid and P-CD in water. Several thermal techniques were used to study the decomposition of p-CD inclusion complexes of ferrocene and derivatives. DSC and derivative thermogravimetric measurements have been reported for crystalline cytidine and deoxycytidine. Heats of formation have been determined for a-D-glucose esters and compared with semiempirical quantum mechanical calculations. ... 

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