OLAOSEBIKAN ABIDOYE OLAFADEHAN
@unilag.edu.ng
Professor/Department of Chemical and Petroleum Engineering
University of Lagos, Lagos, Nigeria
RESEARCH INTERESTS
Modelling and Simulation of Chemical and Biochemical Reaction Systems, Computational Fluid Dynamics, Adsorption, Separation Processes, Environmental Engineering and Optimization studies.
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Olubunmi G. Abatan, Olaosebikan A. Olafadehan, Vincent E. Efeovbokhan, Olagoke Oladokun, and Augustine O. Ayeni
Elsevier BV
Olaosebikan Abidoye Olafadehan, Victor Ehigimetor Bello, and Kehinde Olawale Amoo
Springer Science and Business Media LLC
A. O. Olatunde, O. A. Olafadehan and M. Usman
A two-dimensional mathematical model was developed for a porous heterogeneous catalytic fixed bed reactor. The model took into account the effect of heat generated by adsorption of reactants on the catalyst surface and heat transfer from the fluid phase to the surroundings which have significant effect on reactor performance especially at reactor hotspot. The developed model predicted the partial oxidation of methanol to formaldehyde on FeO/MoO3 catalyst, a complex reaction system. Excellent agreement was achieved when the resultant simulated results were compared with experimental data in the literature. The proposed model predicted the location of hotspot at a dimensionless distance of 0.4413 (= 0.0309 m) the same as the experiment value but with a temperature of 619 K compared with experimental value of 622 K. The conventional heterogeneous and pseudo-homogeneous models predicted the hotspot temperature to be about 8 K and 34 K lower than the experimental value respectively.
V.E. Bello and O.A. Olafadehan
Elsevier BV
O. A. Olafadehan, T. O. Ajayi, and K. O. Amoo
Pleiades Publishing Ltd
The optimization of process variables for the extraction of chitin and chitosan from crab (Callinectes amnicola) shell waste and for the degree of deacetylation (DDA) of extracted chitosan was investigated using response surface methodology (RSM). The respective effects of four and three process parameters on the extraction yields of chitin and chitosan and on the DDA of chitosan were examined. The optimized chitin extraction conditions based on the yield (4.84 g or 19.36%) were obtained to be 3.25 M HCl solution, 18.55 h demineralization time, 2.39 M NaOH solution and 2 h deproteinization time, while the maximum chitosan yield (5.98 g or 13.29%) was obtained at modelled optimized conditions of 50% w/w NaOH solution, 85.05°C deacetylation temperature, and 133.64 min deacetylation time. The modelled optimization conditions for the highest DDA of chitosan produced from crab shell waste were 50% w/w NaOH solution, 84.46°C deacetylation temperature, and 187 min deacetylation time, with the corresponding predicted DDA of 84.20%. Excellent agreement was obtained between experimental DDA of chitosan (84.50%) and the predicted value, with the percentage error being ±0.36. Independent predicted robust quadratic models for predicting the yields of chitin and chitosan extraction and the DDA of chitosan from the crab shell waste were obtained, validated and verified.
A.A. Ayoola, F.K. Hymore, C.A. Omonhinmin, P.O. Babalola, E.O. Bolujo, G.A. Adeyemi, R. Babalola, and O.A. Olafadehan
Elsevier BV
K. E. Abhulimen, V. O. Adeniyi, and O. A. Olafadehan
Pleiades Publishing Ltd
An optimal waste minimisation exchange network was designed for the control of effluent, thermal and gaseous wastes generated from process systems. The model used the concept of pinch technique, which was based on a weighted design superstructure that set design products production targets at 25, 50 and 75% against an operating benchmark status, to optimize the product/waste production from a crude distillation unit of an existing operating refinery. The linear programming model that resulted from the analysis of these waste systems and the composite plots were generated for thermal, gaseous and liquid effluent waste streams. The dynamics of waste recovery systems was investigated in relation to the movement of the pinch position as the process conditions are modified or changed based on design targets of 25, 50 and 75% of the products production scheme. The pinch point was located and the high and low waste generating systems were identified and quantified. The analysis of the composite plots and the solution of the linear programming model showed that a design target that minimized the production of gaseous and liquid wastes was obtained when the deviation of the pinch point favoured movement of product curve away from the waste curve. Thus, a new design model that allows the user to predict and minimize waste from a refinery process system was presented.
O. A. Olafadehan and E. U. Okinedo
Informa UK Limited
Abstract A feasible, comprehensive, and rigorous mechanistic kinetic model was developed for hydrogenolysis of benzothiophene on a commercial Co-Mo/γ-Al2O3 catalyst. The kinetics was modelled with 28-rate expressions based on molecular and atomic adsorption of hydrogen. The kinetic parameters were estimated for each model using the optimization routine of the Nelder—Mead simplex algorithm. Discrimination among rival models was based on physicochemical criteria, analysis of residuals, and statistical tests. The surface reaction between adsorbed benzothiophene and adsorbed hydrogen on σ sites in the direct hydrogenolysis of benzothiophene to ethylbenzene, the surface reaction between adsorbed benzothiophene and adsorbed hydrogen on τ sites in the hydrogenation of benzothiophene to dihydrobenzothiophene, and the surface reaction between adsorbed dihydrobenzothiophene and adsorbed hydrogen on σ site in the hydrogenolysis of dihydrobenzothiophene to ethylbenzene when hydrogen is adsorbed atomically are found to be the rate-determining steps. The predicted activation energies and enthalpies of adsorption compare exceedingly well with previously reported values in the literature.
O. A. Olafadehan, D. S. Aribike, and A. M. Adeyemo
Pleiades Publishing Ltd
A detailed mathematical model for evaluating lactose hydrolysis with immobilized enzyme in a packed bed tubular reactor is presented. The model accounts for axial and radial dispersion effects, chemical reaction and external mass transfer resistances but is void of significant internal diffusion resistances of the particles. The comprehensive model was then simplified to a plug flow model for lactose-lactose hydrolysis in fixed bed. The resulting plug flow model was solved by using Runge-Kutta-Gill method via employing different kinetics for lactose hydrolysis. The reliability of model simulations was tested using experimental data from a laboratory packed bed column, where the β-galactosidase of Kluyveromyces fragilis was immobilized on spherical chitosan beads. Comparison of the simulated results with experimental exit conversion show that the plug flow model incorporating Michaelis-Menten kinetics with competitive product (galactose) inhibition are appropriate to interpret the experimental results and simulate the process of lactose hydrolysis in a fixed bed when the mass transfer resistance was reduced by a factor of 34.5.
O. A. Olafadehan, A. A. Susu, and A. Jaiyeola
Informa UK Limited
Abstract The kinetics of the reforming of n-heptane on a platinum/alumina catalyst has been studied in a pulse microcatalytic reactor at a total pressure of 391.8 kPa over a relatively wide temperature range of 420°C–500°C. The differential and integral methods were used for the kinetic analyses of the reforming reaction. Twenty-nine reaction rate equations of the Langmuir-Hinselwood-Hougen-Watson type, based on molecular and atomic adsorption of hydrogen, were developed. Parameter estimates for the n-heptane reforming reactions were obtained by application of the Nelder-Mead simplex optimization technique to the predicted and observed conversion/production rates of the reaction components. Discrimination among rival kinetic models was based upon physicochemical criteria, analysis of the residuals, and statistical and thermodynamic tests. The rate-determining step was found to be the surface reaction of adsorbed iso-heptane to adsorbed methylcyclohexane with dissociative adsorption of hydrogen on the catalyst surface during dehydrocyclization of iso-heptane to methylcyclohexane. Hence, the surface reaction on the metallic function is rate-determining for the n-heptane reforming on the Pt/Al2O3 catalyst.
D. S. Aribike and O. A. Olafadehan
Pleiades Publishing Ltd
Mathematical modeling of liquid phase adsorption of phenols in fixed beds of granular activated carbon was investigated. The model considered the effects of axial diffusion in the fluid, the external film and internal diffusional mass transfer resistances of the particles, and the nonlinear adsorption isotherm of Freundlich. It was shown that the analysis of a complex multicomponent adsorption system could be simplified by converting it into a pseudo single-component adsorption system. This was achieved by lumping the concentrations of the components together as one single parameter, chemical oxygen demand. The resulting model equations were solved using the orthogonal collocation method and third-order semi-implicit Runge-Kutta method combined with a step-size adjustment strategy. Excellent agreement between simulated results and pilot plant data was obtained. Also, the breakthrough profiles revealed the formation of a primary monomolecular layer on the adsorbent surface.
O. A. Olafadehan and S. O. Oghenekaro
Informa UK Limited
Abstract A feasible, comprehensive, and rigorous mechanistic kinetic model was developed for hydrogenolysis of thiophene on a commercial hydrodesulphurization Co-Mo/γ-Al2O3 catalyst. The kinetics were modeled with 24 rate expressions based on three modes of adsorption: molecular and atomic adsorption of hydrogen, and Eley Rideal mechanism. The experimental data were obtained in a bench-scale tubular reactor with plug flow, and the conditions varied over the following range: total pressure, P t = 2–30 bar, temperature = 533–625 K, and molar hydrogen to hydrocarbon ratios 4–9. The experimental rate data were described by a set of Lagmuir-Hinshelwood-Hougen-Watson rate equations for both the hydrogenolysis of thiophene to butene and the hydrogenation of butene to butane on two different sites, σ and τ. The kinetic rate constants and adsorption equilibrium constants were estimated for each model using the optimization routine of Nelder-Mead simplex algorithm. Discrimination among rival models was based upon physicochemical criteria, analysis of the residuals, and statistical tests. The surface reaction between adsorbed thiophene and adsorbed hydrogen on σ sites in the hydrogenolysis, and the surface reaction between adsorbed butene and adsorbed hydrogen on τ sites in the hydrogenation when hydrogen is adsorbed molecularly are found to be the rate-determining steps. The predicted activation energies, enthalpies of adsorption, Gibbs free energies, and adsorption entropies compare exceedingly well with previously reported values in the literature.
Olaosebikan A. Olafadehan and Alfred A. Susu
Hindawi Limited
A generalized mathematical model is presented to describe the process of multi-component adsorption onto porous media in fixed beds. The model was applied to the binary adsorption, without reaction, of aromatics and sulphur compounds onto a fixed bed of Porocel clay for kerosene deodorization using linear, Freundlich and Langmuir isotherms independently. A computational scheme for the solution of the model equations is presented. The scheme is based on orthogonal collocation for spatial discretization of the resulting set of coupled hyperbolic and parabolic partial differential equations for the macro-and micro-system, respectively. Michelsen's modified third-order semi-implicit Runge-Kutta method combined with step-size adjustment strategy was used to integrate the resulting 4N ordinary differential equations. Excellent agreement between the simulated results and pilot plant data was obtained for the breakthrough profiles for the non-linear adsorption isotherms of Freundlich and Langmuir. No agreement was obtained for the linear isotherm. Also, using the Freundlich and Langmuir isotherms, the exit concentration of the less preferentially adsorbed component (aromatics) exceeded its inlet concentration to the adsorption column for a certain period. This is indicative of the behaviour of competitive multi-component adsorption: relative to aromatics, sulphur compounds are selectively adsorbed onto Porocel clay. The relationship between solid- and liquid-phase concentration profiles for the Freundlich isotherm revealed the formation of multiple adsorption layers upon the primary mono-molecular layer. Again, for the Freundlich isotherm, the structure of the profiles exhibited a highly pronounced maximum for sulphur. An experimental breakthrough time of 8 h was also predicted for both aromatics and sulphur compounds using the non-linear Freundlich and Langmuir isotherms.
Olaosebikan A. Olafadehan and Alfred A. Susu
Informa UK Limited
Abstract A mathematical model equation for binary adsorption-reaction process is developed and illustrated for the catalytic dehydrogenation of cyclohexane to benzene on Platinum-Rhenium/Alumina catalyst with unadsorbed hydrogen in inert (argon, he lium) and active (hydrogen) carrier gases using pulse and continuous flow techniques. The optimization routine of Nelder-Mead simplex algorithm is developed with a view to estimating surface reaction rate and adsorption equilibrium constants at different temperatures, which in turn are used to determine activation energies and adsorption equilibrium energies for cyclohexane dehydrogenation in inert and active carrier gases using pulse and continuous flow techniques.
Olaosebikan A. Olafadehan and Alfred A. Susu
American Chemical Society (ACS)
A computational procedure is presented for solving the set of stiff hyperbolic and parabolic partial differential equations describing the simultaneous adsorption of a ternary system in a column packed with adsorbent particles using nonlinear adsorption isotherms of Fritz and Schluender. The model equations account for the effects of axial diffusion in the fluid and in the film and internal diffusional mass-transfer resistances of the particles. Orthogonal collocation and Michelsen's modified third-order semiimplicit Runge−Kutta methods combined with a step-size adjustment strategy are used to solve the general form of the resulting 6N coupled ordinary differential equations for simultaneous adsorption of 2-butanol, tert-amyl alcohol, and phenol in fixed beds. Simulated results obtained from this model are compared with experimental data. Excellent agreement between simulated results and previously published experimental data is obtained in 0.41- and 0.82-m adsorbers when the film mass-transfer coefficien...
Olaosebikan A. Olafadehan and Alfred A. Susu
Hindawi Limited
A computational procedure is presented for solving the set of rigid hyperbolic and parabolic partial differential equations describing the simultaneous adsorption of a ternary system in a column packed with adsorbent particles using the non-linear adsorption isotherms of Fritz and Schluender. The model equations account for the effects of axial diffusion in the fluid and the film and internal diffusional mass-transfer resistances of the particles. Orthogonal collocation and Michelsen's modified third-order semi-implicit Runge-Kutta method combined with a step-size adjustment strategy were used to solve the general form of the resulting 6N coupled ordinary differential equations for the simultaneous adsorption of butan-2-ol, t-amyl alcohol and phenol in fixed beds. The simulated results obtained from this model were compared with experimental data. Excellent agreement between the simulated results and previously published experimental data was obtained. The breakthrough profiles were also indicative of the competitive multi-component adsorption behaviour as well as the formation of multiple adsorption layers upon the primary monomolecular layer.
Olaosebikan A. Olafadehan and Alfred A. Susu
American Chemical Society (ACS)
O. A. Olafadehan and A. A. Susu
Springer Science and Business Media LLC
A mathematical model equation for the ternary adsorption–reaction process was developed and illustrated for the catalytic dehydrogenation of cyclohexane to benzene with the adsorption of hydrogen atoms as a monomolecular species on platinum–rhenium/alumina catalyst in inert and active carrier gases using pulse and continuous flow techniques. An optimization routine of the Nelder–Mead simplex method was used to estimate the surface reaction rate constant and adsorption equilibrium constant at different temperatures. These constants were then used to determine activation energies and adsorption equilibrium energies for cyclohexane dehydrogenation in inert (argon, helium) and active (hydrogen) carrier gases using pulse and continuous flow techniques. Numerical solutions for the ternary adsorption–reaction scheme were compared with the binary adsorption–reaction case where hydrogen adsorption is ignored. The predicted results for the ternary adsorption–reaction revealed that hydrogen adsorption during cyclohexane dehydrogenation is significant.