The Experts below are selected from a list of 1326 Experts worldwide ranked by ideXlab platform
Katarzyna Bizon - One of the best experts on this subject based on the ideXlab platform.
-
optimal design of a non isothermal hybrid Catalyst Pellet based on pod deim reduced order methodology
2020Co-Authors: Katarzyna Bizon, Gaetano ContinilloAbstract:Abstract The problem of the optimal design of a Catalyst Pellet occupied by different types of active sites was formalized and solved for a non-isothermal system of two consecutive chemical reactions. The maximization of the desired product yield was tackled with model-order reduction techniques. Proper Orthogonal Decomposition (POD) and Discrete Empirical Interpolation Method (DEIM) were employed to reduce the Catalyst Pellet balance equations that need to be resolved to evaluate the objective function. It was demonstrated that the Pellet performance may be significantly improved by choosing proper fractions of two types of catalytic active centers. Moreover, application of the model-order reduction procedure permitted to solve the problem with a minimal numerical effort without affecting significantly the accuracy.
-
determination of the optimal distribution of active centers in a multifunctional Catalyst Pellet using global searching combined with reduced order modeling approach
2019Co-Authors: Katarzyna Bizon, Gaetano ContinilloAbstract:Abstract The problem of optimal distribution of two types of catalytic active sites for yield maximization is solved for a spherical porous Catalyst Pellet. The case where two consecutive chemical reactions with one reversible step following arbitrary kinetics occur under isothermal conditions is investigated numerically using the global searching technique. The constraints given by mass balances of the reactants within the Pellet accounting both for internal and external mass transfer resistances are reduced by means of Proper Orthogonal Decomposition combined with Galerkin projection method. The applied computational procedure gives significant savings in calculation time as compared to classical discretization approach based on finite differences. Results demonstrate that particle microstructuring via optimal Catalyst distribution within the Pellet may constitute a powerful means of multistep process intensification.
-
Assessment of a POD method for the dynamical analysis of a Catalyst Pellet with simultaneous chemical reaction, adsorption and diffusion: Uniform temperature case
Computers and Chemical Engineering, 2017Co-Authors: Katarzyna BizonAbstract:A model reduction method applied to the dynamic model of a single isothermal Catalyst Pellet with simultaneous chemical reaction, diffusion and adsorption is presented. The model of the Pellet accounts for both internal and external resistances to mass transfer, and variable bulk gas concentration. The reduction of the model was performed by means of proper orthogonal decomposition (POD). Accuracy and computational efficiency of the reduced order model (ROM) were discussed for two kinetic models, i.e. a first order chemical kinetics and a Langmuir???Hinshelwood kinetics. To improve the computational efficiency of the model described by the Langmuir???Hinshelwood equation, the non-linear terms were approximated by a discrete empirical interpolation method (DEIM). High accuracy and efficiency of the proposed reduction approach was demonstrated.
-
Dynamics of an isothermal Catalyst Pellet with simultaneous chemical reaction and adsorption
Chemical Engineering Research & Design, 2016Co-Authors: Katarzyna Bizon, Bolesław TabiśAbstract:Abstract The dynamics of a porous, isothermal Catalyst Pellet with simultaneous chemical reaction, diffusion and reactant adsorption is analyzed. The influence of reactant adsorption is characterized for the linear isotherm and two Freundlich isotherms. Transient responses of the Catalyst Pellet to different initial conditions and to external perturbations of the reactant concentration are evaluated. External perturbations include step and periodic variations of the bulk reactant concentration. It is demonstrated that both adsorption of the reactant and the shape of the isotherms considered have a significant impact on the dynamics of the Catalyst Pellet. Such influence is verified with both disturbances, by imposing initial conditions different from the steady state and by applying external perturbations. For periodic variations of the bulk reactant concentration, the shape of the sorption isotherm adopted also influences the concentration profiles of the reactant in the Pellet. The sorption phenomenon causes damping of the concentration oscillations within the Pellet. Depending on the shape of the sorption isotherm, marked concentration oscillations are observed in part or in the whole volume of the Pellet.
V. A. Kirillov - One of the best experts on this subject based on the ideXlab platform.
-
self oscillation liquid front inside a partially wetted Catalyst Pellet under α methylstyrene hydrogenation experiment and theory
Industrial & Engineering Chemistry Research, 2005Co-Authors: A. B. Shigarov, And Alexander V Kulikov, V. A. KirillovAbstract:Self-oscillations on a partially wetted cylindrical Catalyst Pellet 1% Pd/γ-Al2O3 in α-methylstyrene (AMS) hydrogenation accompanied by liquid evaporation are studied. By NMR tomography (magnetic resonance microimaging), images of the liquid-phase distribution within the porous Pellet are obtained and the liquid-phase redistribution is monitored immediately during the process. The physical mechanism and simplified one-dimensional model are suggested to explain the observed phenomenon. The model predicts well the experimental period (2−3 min) and the amplitudes of the temperature oscillations at the lower (dry) part of the Pellet and also the liquid front oscillations at the upper part. The instability mechanism (negative feedback with time lag) is based on complex interaction among the processes of imbibition, evaporation, and gas-phase hydrogenation.
-
Self-oscillations on a partially wetted Catalyst Pellet in α-methylstyrene hydrogenation: Experiment and mathematical modeling
Theoretical Foundations of Chemical Engineering, 2005Co-Authors: V. A. Kirillov, I. V. Koptyug, A. V. Kulikov, N. A. Kuzin, A. A. Lysova, A. B. Shigarov, V. N. ParmonAbstract:Self-oscillation modes on an irrigated porous Catalyst Pellet in exothermic hydrogenation accompanied by liquid evaporation is studied. By NMR tomography (magnetic resonance microimaging), images of the liquid-phase distribution within the porous object are obtained and the liquid-phase redistribution is monitored immediately during the process without destroying the object and without introducing any probes or molecular labels.
-
modeling of critical phenomena for liquid vapor gas exothermic reaction on a single Catalyst Pellet
Chemical Engineering Journal, 2003Co-Authors: A. B. Shigarov, N. A. Kuzin, A. V. Kulikov, V. A. KirillovAbstract:Abstract Physical mechanisms are discussed and crude mathematical models with lumped parameters are developed, which explain the authors recent experimental data [4] , concerning temperature hysteresis and multiplicity phenomena for α-methylstyrene (AMS) liquid–vapor hydrogenation on a single Catalyst Pellet. The interplay between endothermic vaporization and exothermic vapor phase reaction is elucidated. The results of this study may help to develop more sophisticated models and theory of hot spots formation and runaway phenomena in trickle-bed reactors.
-
nmr imaging of the distribution of the liquid phase in a Catalyst Pellet during α methylstyrene evaporation accompanied by its vapor phase hydrogenation
Journal of the American Chemical Society, 2002Co-Authors: Igor V Koptyug, V. A. Kirillov, A. A. Lysova, Alexander V Kulikov, And Valentin N Parmon, R Z SagdeevAbstract:This communication reports the first application of NMR imaging to study the progress of a multiphase heterogeneous catalytic reaction in situ. Various stationary regimes of α-methylstyrene (AMS) hydrogenation on a single Pt/γ−Al2O3 Catalyst Pellet have been investigated. The two-dimensional maps of the liquid-phase distribution within the Pellet have been obtained in the course of the catalytic reaction, with the Pellet temperature rising up to 185 °C. The large liquid-phase concentration gradients have been shown to exist under conditions of liquid AMS evaporation accompanied by its vapor-phase hydrogenation. It has been demonstrated that despite a substantial broadening of the NMR lines of liquids permeating porous solids the quantification of the relative amounts of AMS and the major reaction product cumene with spatial resolution across the Pellet is feasible.
-
External diffusion control in the gas-phase dehydrogenation of hydrocarbons on a Catalyst Pellet
Theoretical Foundations of Chemical Engineering, 2000Co-Authors: V. A. Kirillov, A. V. Kulikov, N. A. Kuzin, B. N. Luk’yanov, V. M. Khanaev, A. B. ShigarovAbstract:External-diffusion gas-phase mass transfer in the catalytic hydrogenation of hydrocarbons was studied theoretically and experimentally. For the model of a stationary diffusion film around a Catalyst Pellet, an approximate solution of Maxwell-Stefan equations was obtained, which allowed the multicomponent diffusion problem to be reduced to a Fick equation involving a pseudobinary effective diffusion coefficient. A comparison was made between the theoretical and experimental results for the hydrogenation of α-methylstyrene, octene, and their mixtures.
José Carlos Pinto - One of the best experts on this subject based on the ideXlab platform.
-
Hybrid Modeling of Methane Reformers. 3. Optimal Geometries of Perforated Catalyst Pellets
Industrial & Engineering Chemistry Research, 2009Co-Authors: André Luís Alberton, Marcio Schwaab, Roberto Carlos Bittencourt, Martin Schmal, José Carlos PintoAbstract:This paper studies the optimization of Catalyst Pellet geometries for the simultaneous maximization of the mechanical strength and Catalyst activity of perforated Catalyst Pellets used for the reforming of methane. This multiobjective problem can be analyzed with the help of Pareto fronts. A previous work (Part 1: Alberton; et al. Ind. Eng. Chem. Res., in press) demonstrated that the effectiveness factor of Catalysts with complex geometry used for the reforming of methane can be expressed as a linear function of the specific area of the Pellet; consequently, Catalyst activity can be expressed in terms of the geometric parameters of the Pellet. It can also be assumed that the mechanical strength of perforated Catalyst Pellets is related to the minimum wall thickness of the solid piece. Therefore, two optimization problems can be proposed: (i) the simultaneous maximization of the specific area and of the minimum wall thickness of the Pellet and (ii) the simultaneous maximization of the overall Catalyst acti...
-
hybrid modeling of methane reformers 1 a metamodel for the effectiveness factor of a Catalyst Pellet with complex geometry
Industrial & Engineering Chemistry Research, 2009Co-Authors: André Luís Alberton, Marcio Schwaab, Carlos Eduardo Fontes, Roberto Carlos Pontes Bittencourt, José Carlos PintoAbstract:In this work, effectiveness factors for methane steam reforming reactions were obtained by solving mass and heat balance equations inside catalytic Pellets for different reaction conditions and catalytic Pellet geometries with the help of CFD (computational fluid dynamic) techniques. CFD computations were performed for real particle geometries and real kinetic rate expressions as described in the technical literature. A linear correlation was found between the effectiveness factor and the area/volume ratio, which characterizes the methane steam reforming as a diffusion-controlled process. The slopes of the straight lines depend of the external reaction conditions, thermal conductivity, and effective diffusivity. On the basis of the CFD results, empirical metamodels were built to represent effectiveness factors for methane steam reforming reactions at different reaction conditions. The metamodels can be easily inserted into a reactor model for simulation of the full industrial process.
Ee Gonzo - One of the best experts on this subject based on the ideXlab platform.
-
approximate expression for the effectiveness factor estimation and a simple numerical method for concentration profile calculation in porous Catalyst
Chemical Engineering Journal, 2005Co-Authors: Jc Gottifredi, Ee GonzoAbstract:Abstract The model of steady state diffusion and reaction in a Catalyst Pellet where a single reaction takes place is analyzed with the scope to predict effectiveness factor through a very simple and practical procedure. Non-linear usual reaction kinetics are used to investigate the agreement among exact or numerical predictions with approximate results. In all cases studied maximum deviations in the whole range of ϕ values are below 4% which turns the procedure attractive and useful. To perform numerical integration of the classical non-linear diffusion and reaction differential equation a new procedure was used that avoid usual instabilities or the introduction of spline collocation methods when concentration profiles are very steep. Concentration resulting profiles are compared with those generated by an early expression proposed by the authors.
-
an approximate expression for predicting concentration and temperature profiles inside a Catalyst Pellet
Chemical Engineering Science, 1996Co-Authors: Jc Gottifredi, Ee GonzoAbstract:The scope of this contribution is to develop an approximate expression based on the available information, since η (effectiveness factor) values are related to the slope of concentration in a region near the surface. Since η values can be accurately predicted, it is possible to build up an approximate expression that also describes the profiles inside the particle
-
diffusion and reaction inside a Catalyst Pellet for a parallel consecutive reaction scheme
Chemical Engineering Science, 1994Co-Authors: Jc Gottifredi, Ee Gonzo, Gilbert F. FromentAbstract:Abstract An analytical solution is presented for the concentration profiles inside a Catalyst particle with uniform activity for a parallel-consecutive reaction scheme containing a reversible step and in which the reactions are all of the first order. An accurate approximate solution for the surface fluxes was developed for the case of non-uniform activity The effects of the degree of reversibility of the first step of the consecutive chain and of the ratio of the surface concentrations of the intermediate and feed component are illustrated. The influence of a non uniform Catalyst activity is shown to be important, particularly in the mixed control regime.
-
Diffusion and reaction inside a Catalyst Pellet for a parallel—consecutive reaction scheme
Chemical Engineering Science, 1994Co-Authors: Jc Gottifredi, Ee Gonzo, Gilbert F. FromentAbstract:Abstract An analytical solution is presented for the concentration profiles inside a Catalyst particle with uniform activity for a parallel-consecutive reaction scheme containing a reversible step and in which the reactions are all of the first order. An accurate approximate solution for the surface fluxes was developed for the case of non-uniform activity The effects of the degree of reversibility of the first step of the consecutive chain and of the ratio of the surface concentrations of the intermediate and feed component are illustrated. The influence of a non uniform Catalyst activity is shown to be important, particularly in the mixed control regime.
Jc Gottifredi - One of the best experts on this subject based on the ideXlab platform.
-
approximate expression for the effectiveness factor estimation and a simple numerical method for concentration profile calculation in porous Catalyst
Chemical Engineering Journal, 2005Co-Authors: Jc Gottifredi, Ee GonzoAbstract:Abstract The model of steady state diffusion and reaction in a Catalyst Pellet where a single reaction takes place is analyzed with the scope to predict effectiveness factor through a very simple and practical procedure. Non-linear usual reaction kinetics are used to investigate the agreement among exact or numerical predictions with approximate results. In all cases studied maximum deviations in the whole range of ϕ values are below 4% which turns the procedure attractive and useful. To perform numerical integration of the classical non-linear diffusion and reaction differential equation a new procedure was used that avoid usual instabilities or the introduction of spline collocation methods when concentration profiles are very steep. Concentration resulting profiles are compared with those generated by an early expression proposed by the authors.
-
an approximate expression for predicting concentration and temperature profiles inside a Catalyst Pellet
Chemical Engineering Science, 1996Co-Authors: Jc Gottifredi, Ee GonzoAbstract:The scope of this contribution is to develop an approximate expression based on the available information, since η (effectiveness factor) values are related to the slope of concentration in a region near the surface. Since η values can be accurately predicted, it is possible to build up an approximate expression that also describes the profiles inside the particle
-
diffusion and reaction inside a Catalyst Pellet for a parallel consecutive reaction scheme
Chemical Engineering Science, 1994Co-Authors: Jc Gottifredi, Ee Gonzo, Gilbert F. FromentAbstract:Abstract An analytical solution is presented for the concentration profiles inside a Catalyst particle with uniform activity for a parallel-consecutive reaction scheme containing a reversible step and in which the reactions are all of the first order. An accurate approximate solution for the surface fluxes was developed for the case of non-uniform activity The effects of the degree of reversibility of the first step of the consecutive chain and of the ratio of the surface concentrations of the intermediate and feed component are illustrated. The influence of a non uniform Catalyst activity is shown to be important, particularly in the mixed control regime.
-
Diffusion and reaction inside a Catalyst Pellet for a parallel—consecutive reaction scheme
Chemical Engineering Science, 1994Co-Authors: Jc Gottifredi, Ee Gonzo, Gilbert F. FromentAbstract:Abstract An analytical solution is presented for the concentration profiles inside a Catalyst particle with uniform activity for a parallel-consecutive reaction scheme containing a reversible step and in which the reactions are all of the first order. An accurate approximate solution for the surface fluxes was developed for the case of non-uniform activity The effects of the degree of reversibility of the first step of the consecutive chain and of the ratio of the surface concentrations of the intermediate and feed component are illustrated. The influence of a non uniform Catalyst activity is shown to be important, particularly in the mixed control regime.