Kinetic analysis coatings

We have developed a compact photocatalytic reactor [1], which enables efficient decomposition of organic carbons in a gas or a liquid phase, incorporating a flexible and light-dispersive wire-net coated with titanium dioxide. Ethylene was selected as a model compound which would rot plants in sealed space when emitted. Effects of the titanium dioxide loading, the ethylene concentration, and the humidity were examined in batches. Kinetic analysis elucidated that the surface reaction of adsorbed ethylene could be regarded as a controlling step under the experimental conditions studied, assuming the competitive adsorption of ethylene and water molecules on the same active site. 

Although cyclic voltammetry could fruitfully be applied to the kinetic analysis of these catalytic systems, it has mostly been investigated by means of rotating disk electrode voltammetry (Section 1.3.2). The simplest case is that of an irreversible catalytic reaction at a monolayer coating. The next section is devoted to the analysis of these systems by the two techniques. 

Table 4. Kinetic analysis of DSC scan data for epoxy powder coating compositions (Ref.108))...

Rajeshwar I52) determined the kinetics of the thermal decomposition of Green River oil shale kerogen by using direct Arrhenius. Freeman and Carroll, and Coats and Redfern methods. The E, A, and values are given in Table 2.7. Rajeshwar concluded that the ability to resolve multiple processes hinges on the efficacy of the particular kinetic analysis employed and is not an inherent difficulty with nonisothermal TG techniques in general. The direct Arrhenius and Coats and Redfern methods clearly indicate the presence of two reactions with distinctly different kinetic parameters. On the olher hand, the Freeman and Carroll method is handicapped at low fractional... 

J. Saien, M. Asgari, A.R. Soleymani, N.Taghavinia, Photocatalytic decomposition of direct red 16 and kinetics analysis in a conic body packed bed reactor with nanostructure titania coated Raschig rings , Chemical Engineering Journal, 151, 295-301, (2009). 

This situation does not necessarily mean that all kinetic data that have been obtained by the Coats and Redfem and similar methods are incorrect. For example, the calculated activation energy frequently has about the same value regardless of whether the correct rate law has been identified or not. That happens because the rate of the reaction responds to a change in temperature according to the Arrhenius equation. The rate law used to fit the kinetic data does not alter the influence of temperature. Also, many kinetic studies on reactions in the solid state have dealt with series of reactions using similar compounds. As long as a consistent kinetic analysis procedure is used, the trends within the series will usually be vahd. Undoubtedly, however, many studies based on incomplete data analysis procedures have yielded incorrect kinetic parameters and certainly have yielded no reliable information on reaction mechanisms. 

The parameters E and A of the coal samples were obtained from the kinetic analysis of TG data. The Coats-Redfern method has a great advantage of simplicity among the kinetic approaches and is extensively acknowledged. The reaction kinetic equation can be deduced as ... 

The effect of the methoxy group at the 4-, 5- or 6-position of the aUyl vinyl ether on the rate of the Claisen rearrangement was investigated by Coates et al. in 1987 using h NMR data for their kinetic analysis [28]. Compared to the unsubstituted allyl vinyl ether, the methoxy substituent can either decrease or dramatically increase the rate of the rearrangement (Scheme 11.20). A very impressive 3800-fold rate acceleration was observed for the 4-methoxy-substituted allyl vinyl ether compared to 5-methoxy-substituted allyl vinyl ether. The rate-accelerating effect of the 6-methoxy substituent was less pronounced but still significant. 

We now discuss the mediated oxidation of [Fe(CN)6] at [Ru(bpy)2PVP5Cl]Cl coated electrodes in aqueous perchlorate media. We illustrate the kinetic analysis of this system using the Andrieux-Saveant approach. The mediation process can be described as follows... 

Typical examples discussed below can help us gain a better understanding of the application of RDEs. Jiang et al. [44] studied the ORR at a rotating disk electrode with multiple small potential steps. Figure 21.6 shows a serial of current-potential curves for the ORR at a HT-FeTPP/CoTPP/PG rotating disk electrode in an 02-saturated 0.5 M sulfuric acid electrolyte. With increasing rotation rate, the catalytic current increases. The kinetic analysis of the ORR at the catalyst coated RDE can be carried out by the Koutecky-Levich equation ... 

A kinetic analysis based on the Coats-Redfern method applied nonisothermal TGA data to evaluate the stability of the polymer during the degradation experiment. Of the different methods, the Coats-Redfern method has been shown to offer the most precise results because gives a linear fitting for the kinetic model function [97]. This method is the most frequent in the estimation of the kinetic function. It is based on assumptions that only one reaction mechanism operates at a time, that the calculated E value relates specifically to this mechanism and that the rate of degradation, can be expressed as the basic rate equation (Eq. 5.3). This method is an integral method that assumes various... 

---