Phenol kinetic modeling

Escher, B. I. Hunziker, R. Schwarzenbach, R. R Westall, J. C., Kinetic model to describe the intrinsic uncoupling activity of substituted phenols in energy transducing membranes, Environ. Sci. Technol. 33, 560-570 (1999). 

A kinetic model was developed to describe the pH-dependent uncoupling activity of substituted phenols in bacterial photosynthetic membranes [2]. In this model, the overall uncoupling activity is quantitatively separated into the contribution of membrane concentration, which can be estimated by the Kmw, and of intrinsic activity. The intrinsic activity of an uncoupler is influenced not only by the hydrophobicity and acidity, but also by steric effects and by the charge distribution within the molecule [2]. 

All the surface recombination processes, including back reaction, can be incorporated in a heavy kinetic model [22]. The predicted, and experimentally observed, effect of the back reactions is the presence of a maximum in the donor disappearance rate as a function of its concentration [22], Surface passivation with fluoride also showed a marked effect on back electron transfer processes, suppressing them by the greater distance of reactive species from the surface. The suppression of back reaction has been verified experimentally in the degradation of phenol over an illuminated Ti02/F catalyst [27]. 

Because of the wide application of these resins to diverse industries and their very different kinetic models and mechanisms of cross-linking and reactions, phenomenological kinetic models for epoxy, vinyl ester, and phenolic resins are presented in the next three subsections. 

Kang N, Lee DS, Yoon J (2002) Kinetic Modeling of Fenton Oxidation of Phenol and Monochlorophenols. Chemosphere 47 915... 

Wu, Y., Taylor, K., Biswas, N., and Bewtra, J., Kinetic model-aided reactor design for peroxidase-catalyzed removal of phenol in the presence of polyethylene glycol, /. Chem. Technol. Biotechnol., 74(6), 519-526, 1999. 

Removal rates greater than 90% were observed for all of the phenols studied. The decay kinetics for phenol p-methoxyphenol p-cresol p-fluo-rophenol p-chlorophenol p-bromophenol 4-hydroxyacetophenone a,a,a-trifluoro-p-cresol p-cyanophenol and p-iodophenol were found to be consistent with the Langmuir-Hinshelwood kinetic model. After employing all the substituents, little variation on the Langmuir-Hinshelwood kinetic parameters was observed. 

Involved in extensive study of SCWO processes Investigated SCWO process for pulp mill sludges Explored kinetics of SCWO of phenol Explored supercritical water reactor Investigated the unique features of supercritical water in terms of density, dielectric constant, viscosity, diffusivity, electric conductance, and solvating ability Explored multistep kinetic model of phenol in SCWO Involved in extensive SCWO study of priority pollutants... 

Tufano, V., A multi-step kinetic model for phenol oxidation in high pressure water, Chem. Eng. Technol., 16, 186-190. 

Aaron Ortiz-Gomez, Benito Serrano-Rosales, Jesus Moreira-del-Rio, and Hugo de-Lasa, Mineralization of Phenol in an Improved Photocata lytic Process Assisted with Ferric Ions Reaction Network and Kinetic Modeling... 

The chapter ends with a case study. Four different reduced kinetic models are derived from the detailed kinetic model of the phenol-formaldehyde reaction presented in the previous chapter, by lumping the components and the reactions. The best estimates of the relevant kinetic parameters (preexponential factors, activation energies, and heats of reaction) are computed by comparing those models with a wide set of simulated isothermal experimental data, obtained via the detailed model. Finally, the reduced models are validated and compared by using a different set of simulated nonisothermal data. 

In this section, the phenol-formaldehyde reaction is introduced as a case study. This reaction has been chosen because of its kinetic complexity and its high exothermic-ity, which poses a strong challenge for modeling and control practice. The kinetic model presented here is adopted to simulate a realistic batch chemical process the identification, control, and diagnosis approaches developed in the next chapters are validated by resorting to this model. 

Only a few studies have tackled the problem of deriving a detailed kinetic model of the phenol-formaldehyde reactive system, mainly because of its complexity. In recent years, a generalized procedure has been reported in [11,14] that allows one to build a detailed model for the synthesis of resol-type phenolic resins. This procedure is based on a group contribution method and virtually allows one to estimate the kinetic parameters of every possible reaction taking place in the system. 

The kinetic model developed in Sect. 2.4 for the phenol-formaldehyde reaction belongs to a wider class of kinetic networks made up of irreversible nonchain reactions. In this section, a general form of the mathematical model for this class of reactive systems is presented moreover, it is shown that the temperature attainable in the reactor is bounded and the lower and upper bounds are computed. 

In this section, the phenol-formaldehyde reactive system is considered as an example of identification of reduced kinetic models. The kinetic model containing 13 components and 89 reactions, developed in Sect. 2.4 to study the production of 1,3,5-methylolphenol, is too detailed and complex for control and monitoring purposes. Thus, in this section this model is referred to as detailed model, while four reduced kinetic models, based on lumped components and reactions, are developed. 

According to the approach described in [11], two alternative reduced kinetic models are proposed here to describe the phenol-formaldehyde reaction network introduced in Sect. 2.4. This approach includes, first, the selection of a general class... 

Phenol, here denoted as reactant A. Since the second reactant, formaldehyde, is fed to the reactor in large excess, its concentration can be assumed as a constant during the reaction thus, it does not explicitly appear in the rate expressions and has not been considered in the reduced kinetic models. 

Table 3.4 Percent phenol conversion X, asymptotic values of concentration computed with the detailed and the reduced kinetic models for phenol, Ca.co, and trimethylolphenol, Cpi0o> and relevant percent errors relative to the detailed model used as reference (indicated by the superscript °)...

Moreover, the results are graphically shown in Figs. 3.3—3.6. In detail, Fig. 3.3 shows the results obtained with the kinetic model (3.57) with first-order kinetics. The fitting of concentrations (left) is rather poor in particular, the asymptotic values at the largest reaction times are not correctly estimated. This reduced model underestimates the Anal product concentration and overestimates the final conversion of phenol by more than 7 percent, which corresponds to an error of more than 43 percent on the phenol concentration and of about 13 percent on product concentration (Table 3.4). A better fitting is obtained for the specific thermal power (Fig. 3.3, right). 

Figure 3.5 Reaction scheme of the gas phase phenol acylation with acetic acid (AcOH) over HMFI at 553 K. Reprinted with permission from Industrial Engineering Chemistry Research, Vol. 34, Guisnet et al., Kinetic modelling of phenol acylation with acetic acid on HZSM5, pp. 1624-1629, Copyright (1995), American Chemical Society...

At neutral pH values, a high variation of reactivity of o-chlorophenol with ozone is observed with small changes in pH. These /cD values were found after gas-liquid kinetic model application to experimental data. Thus, the ozonation of o-chlorophenol was found to be a pseudo first-order fast gas liquid reaction as found by Hoigne and Bader [46] in homogeneous ozonation experiments. Trends of /cD with pH for other ozone-phenol reactions are similar to that depicted in Fig. 9. 

In general, a reaction kinetics following a LHHW model is suitable, but the identification of parameters remains demanding. For some catalysts power-law models may be appropriate, for others not. For example, reaction orders identical with stoichiometric coefficients were suitable for Pd/Al203 doped with different metals. On the contrary, for Pd/MgO reaction orders with respect to phenol ranging from -0.5 to 0.5 were observed [17]. However, the bibliographic search was not able to find a quantitative kinetic model for Pd-type catalysts suitable for reactor design. 

Santos, A. (2005) Kinetic model of wet oxidation of phenol at basic pH using a copper catalyst. Chem. Eng. Sci. 60,4866 1878. 

Regarding fhe kinefic modeling, few contributions propose kinetic models for fhe PC oxidation of phenol and other aromatics (Chen and Ray, 1998, 1999 Li et al., 1999b Wei and Wan 1992 ), with kinetic models being based mainly on the initial rates of reacfion only. Such models fail to account for fhe formafion of fhe differenf reaction intermediates, which may play an important role in the overall mineralization rate. More recently, Salaices et al. (2004) developed a series-parallel kinetic model based on observable aromatic intermediates. This model was applied to a wide range of pH, phenol concenfrafion, and cafalysf t)q)e. In this model, however, some steps... 

KINETIC MODELING UNPROMOTED PC OXIDATION AND Fe-ASSISTED PC OXIDATION OF PHENOL... 

Figures 21a, b show the 4-CP, 4-CC, and HQ concentrations derived from inserting the estimated parameters in the kinetic model and a comparison with the experimental data under different operating conditions. Symbols correspond to experimental data and solid lines to model predictions calculated with Equations (64)-(66) and Equations (71)-(74). Eor these experimental runs, the RMSE was less than 14.4%. These experimental 4-CC and HQ concentrations are in agreement with the proposed kinetic mechanism of parallel formafion of fhe intermediate species (Figure 16), and also with the series-parallel kinetic model reported by Salaices et al. (2004) to describe the photocatalytic conversion of phenol in a slurry reactor under various operating conditions. ...

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