Eley-Rideal model

An Eley—Rideal model with dissociative adsorption of oxygen is proposed by Bhattacharyya et al. [48]. Because the oxygen adsorption is assumed to be irreversible, the model is identical with a redox model and... 

The models described above are termed Langmuir-Hinshelwood-Hougen-Watson (LHHW) models, named after the scientists that contributed a lot to the development of these engineering models. The characteristics of these models are that adsorption follows the Langmuir isotherm, and that reaction takes place between adsorbed species. Sometimes, one distinguishes Eley Rideal models, whereby a molecule reacts directly from the gas phase with a surface complex ... 

These reactions are based on the assumptions only irreversible dissociative adsorption of oxygen (2), and instantaneous desorption of the carbon dioxide produced (3)(4)(5). In the temperature range of this study (300-650 K) these assumptions were found to be valid. Reaction (3) represents a reaction according to the Langmuir-Hinshelwood model, whereas reactions (4) and (5) represent reactions according to an Eley-Rideal model. 

Pulsing CO over O-covered platinum does not show an inhibition. This can either be because the reaction of CO with adsorbed oxygen can occur according to the Eley-Rideal model, or because some free sites are always available for CO adsorption. Whichever is the case cannot be concluded from the experiments performed. 

Of the equations given reaction (3) represents a reaction according to the Langmuir-Hinshelwood model and reactions (4) and (5) represent reactions according to an Eley-Rideal model. 

Langmuir-Hinshelwood models involving the reaction between adsorbed oxygen and adsorbed reactant molecules (Luo and Ollis, 1996 Nimlos et ai, 1996 Feral and Ollis, 1992) and b) Eley-Rideal models, which consider the reaction between adsorbed oxygen and gas phase reactant molecules (Fox, 1988). Cunningham and Hodnett (1981) suggested a combination of the Langmuir-Hinshelwood and Eley-Rideal kinetics. 

All four models give a good fit to the data, though with quite different values for the adsorption constants and rate constant. An Eley-Rideal model involving hydrogen from the gas phase gives a poor fit because it predicts first-order behavior for hydrogen. 

Can the data in Figure 2.12 be correlated with a standard Langmuir-Hinshelwood or Eley-Rideal model for reaction on the silver catalyst ... 

Figure 3.10 Test of Eley-Rideal model for benzene alkylation using initial rate data from Example 3.5. 

An oxidation mechanism of the carbon monoxide following the Eley-Rideal model is realistic if we consider the existence of a weakly bonded oxygen species and, subsequently, extremely reactive oxygen species. Nevertheless, it seems that... 

The choice to work with a macrokinetic model (i.e., an empirical equation) is made to simplify the kinetic parameters to be regressed. Because the WGS reaction has been discovered, many kinetic expressions have been developed and used. In general, either the Langmuir—Hinshelwood or the Eley—Rideal models have been used. In Table 1.1, most of the macrokinetic models are reported as an extract of a review of Smith, Loganathan, Shantha (2010). 

Altiokka et al. (2003) obtained the kinetics data on the esterification of acetic acid with isobutanol from both homogeneously (autocatalyzed) and heterogeneously catalyzed reactions using dioxane as a solvent in a stirred batch reactor. The uncatalyzed reaction was found to be second-order reversible. In the presence of the catalyst, on the other hand, the reaction was found to occur between an adsorbed alcohol molecule and a molecule of acid in the bulk fluid (Eley-Rideal model). It was also observed that the initial reaction rate decreased with alcohol and water concentrations and linearly increased with that of acid. The temperature dependency of the constants appearing in the rate expression was also determined. 

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