Search results for "Kinetic model"
showing 10 items of 58 documents
Copolymerization of VDF and HFP in Supercritical Carbon Dioxide: A Robust Approach for Modeling Precipitation and Dispersion Kinetics
2012
A kinetic model is developed for the heterogeneous free-radical copolymerization of vinylidene fluoride and hexafluoropropylene in supercritical CO 2. The model accounts for polymerization in both the dispersed (polymer-rich) phase and in the continuous (polymer-free) supercritical phase, for radical interphase transport, diffusion limitations, and chain-length-dependent termination in the polymer-rich phase. A parameter evaluation strategy is developed and detailed to estimate most of the kinetic parameters a priori while minimizing their evaluation by direct fitting. The resulting model predictions compare favorably with the experimental results of conversion and MWD at varying monomer fe…
A multilevel object-oriented modelling methodology for physiologically-based pharmacokinetics (PBPK): Evaluation with a semi-mechanistic pharmacokine…
2019
Abstract Background and objective The aims of this study are (i) to assess the predictive reliability of the physiologically based software PhysPK versus the well-known population approach software NONMEM for the cited semi-mechanistic PK model, (ii) to determine whether these modelling approaches are interchangeable and (iii) to compare acausal with causal modelling approaches in the framework of semi-mechanistic PK models. Methods A semi-mechanistic model was proposed, which assumed oral administration of a solid dosage form with a peripheral compartment and two active metabolites. The model incorporates intestinal transit, dissolution limited by solubility, variable efflux transporter ex…
Modeling of the process of moisture loss during the storage of dried apricots
2011
[EN] Moisture content is a reference parameter for dried food because the growth of most microorganisms is inhibited below certain water activity levels. In addition, it has a determining influence on the evolution of important parameters, such as color and flavor, and on other properties and deterioration reactions, such as texture, oxidation processes and nutritional value. During the storage of some dried fruits, moisture is produced due to Maillard reactions and exchanged with the surrounding environment through the packaging. The evolution of dried foods during their shelf life depends on the storage conditions. The aim of this study is to analyze the evolution of the moisture content …
Kinetic Aspects of Heterogeneous Catalytic Versus Photocatalytic Reactions
2019
Abstract Kinetics aspects of heterogeneous catalysis and photocatalysis are reported together with the most used models developed for both fields. The chapter describes the main mechanisms involved in the different processes and the parameters used to determine their performances. A comparison of the behaviors and kinetics features of heterogeneous catalysis and photocatalysis is presented.
On-line monitoring of photosynthetic activity based on pH data to assess microalgae cultivation
2020
[EN] Microalgae performance of outdoor cultivation systems is influenced by environmental and operating dynamics. Monitoring and control systems are needed to maximise biomass productivity and nutrient recovery. The goal of this work was to corroborate that pH data could be used to monitor microalgae performance by means of data from an outdoor membrane photobioreactor (MPBR) plant. In this system, microalgae photosynthetic activity was favoured over other physical and biological processes, so that the pH data dynamics was theoretically related to the microalgae carbon uptake rate (CUR). Shortand long-term continuous operations were tested to corroborate the relationship between the first d…
General Kinetic Analysis and Comparison of Molecular Weight Distributions for Various Mechanisms of Activity Exchange in Living Polymerizations
1997
The molecular weight distributions in many living (e.g. anionic, group transfer, cationic, and radical) polymerizations strongly depend on the dynamics of various equilibria between chain ends of d...
Green synthesis of bromine by TiO2 heterogeneous photocatalysis and/or ozone: A kinetic study
2018
Abstract Elemental bromine is an industrially relevant compound traditionally produced from bromide ions by using chlorine as the oxidizing agent. Problems related to transportation and handling of the corrosive, expensive and toxic chlorine make green synthetic alternatives highly desirable. In this paper the green synthesis of bromine from bromide in aqueous solutions under mild conditions by means of TiO2 photocatalysis and/or ozonation has been investigated from a kinetic point of view. The ozonation in the absence of the photocatalyst follows a first order kinetic with respect to both ozone and bromide. The kinetics of the reactions in the presence of the photocatalyst has been describ…
An experimental and kinetic modeling study on the oxidation of 1,3-dioxolane
2021
International audience; The modern catalytic or enzymatic advances allow the production of novel biofuel. Among them, 1,3dioxolane can be produced from formaldehyde and ethylene glycol, both can be obtained from biomass. In this study, the oxidation of 1,3-dioxolane is studied at stoichiometric conditions. The ignition delay times of 1,3-dioxolane/O 2 /inert mixtures were measured in a shock tube and in a rapid compression machine at pressures of 20 to 40 bar and temperatures ranging from 630 to 1300 K. The pressure profiles recorded in the rapid compression machine show a first stage of ignition enlightening the influence of the low temperature chemistry of combustion. Furthermore, mole fr…
Kinetic Modeling of Ethyl Benzoylformate Enantioselective Hydrogenation over Pt/Al2O3
2014
A kinetic model was developed for the enantioselective hydrogenation of ethyl benzoylformate (EBF) on a modified Pt/Al2O3 catalyst. This model was based on the assumption of different numbers of si...
On the integration of kinetic models using a high-order taylor series method
1992
A general equation to derive kinetic models up to any order is given. This equation greatly facilitates the application of the Taylor series method to the integration of kinetic models up to very high orders. When dealing with non-stiff models, computing time is always reduced by increasing the integration order, at least up to the 20th order. When the model is stiff, the integration order should be optimized; however, a twelfth order is recommended to integrate weakly stiff models. The use of an algorithm which permits the immediate calculation of the integration step size required to maintain a given accuracy leads to further reductions in computing time. When implemented as recommended h…