72 research outputs found
A lumped kinetic model for liquid-phase catalytic oxidation of p-xylene to terephthalic acid
No full textA lumped kinetic scheme for the liquid-phase oxidation of p-xylene to terephthalic acid catalyzed by cobalt naphthenate is developed. It is assumed that all The reactions are zeroth- and first-order with respect to gaseous and liquid reactants, respectively. The reliability of the developed kinetic model is investigated by comparison with experimental data obtained in a semibatch oxidation reactor where the gar. phase and the liquid phase are well mixed. The experiments included different values of the initial concentration of the liquid reactants, two gaseous reactants (i.e. pure oxygen and air) and temperature values in the range 100-130 degrees C
Microalgal cell disruption through Fenton reaction: Experiments, modeling and remarks on its effect on the extracted lipids composition
No full textA novel cell disruption technique, based on the use of Fenton reaction, for the improvement of lipid extraction from microalgae has been recently presented in the literature. In this work, a mathematical model is proposed to quantitatively interpret the relevant experimental results obtained so far. Model results and experimental data are successfully compared. Moreover, a mechanistic explanation of the relevant phenomena underlying the positive effects of disruption on the composition of fatty acids methyl esters, obtained through trans-esterification of the extracted lipids, is presented
Modeling of gas-liquid reactors. Isothermal semibatch and continuous stirred tank reactors
No full textA computer code for the simulation of isothermal stirred gas-liquid reactors, both continuous and semibatch, has been developed. The models are constituted of two moduli. The first one describes the diffusion-reaction processes at the gas-liquid interphase, and is based on the film model. This modulus is the same for all reactors. The second one describes the time evolution (semibatch reactor) or the steady state behavior (continuous reactor) of the composition of the bulk liquid and gas phases, which depends on the specific reactor configuration and fluodynamics. The simulation code has been developed for the most general case, involving any type of kinetic scheme and reaction rate expressions, evaporation of volatile liquid components, recycle of condensed liquid from the condenser, etc. Specific numerical algorithms have been implemented for the solution of the mathematical models in all possible operating conditions. All fluodynamic and transport parameters are evaluated internally using selected semi-empirical relations derived from the literature. Thus the required input data to the computer code involve only the physicochemical properties of the involved chemical species and the kinetic parameters involved in the reaction rate expressions. The performance of the simulation models has been tested by comparison with experimental data for two processes of practical interest: catalytic oxidation of p-xylene and photochemical chlorination of p-xylene. (C) 1997 Elsevier Science Ltd
Stripping of ammonia from aqueous solutions of amino acids and inorganic ions
No full textThe stripping of ammonia from aqueous solutions of amino acids and strong electrolytes has been investigated both experimentally and theoretically. The experiments have been carried out in an isothermal stirred semibatch stripper. A good agreement between experimental data and model predictions has been obtained for all the examined operating conditions. The model accounts for all dissociation equilibria while it assumes ideal behavior for the liquid phase. It does not include any adjustable parameter, and so it can be readily extended to various systems of practical interest, such as those involved in the treatment of side-streams arising in the production of amino acids
Kinetics of P-xylene Liquid-phase Catalytic-oxidation
No full textA semibatch gas-liquid reactor model based on a lumped kinetic scheme for the liquid-phase oxidation of p-xylene to p-toluic acid catalyzed by cobalt naphtenate is developed. The model accounts for the complex nature of the involved reaction network, as well as for the interphase and interphase mass transport processes of both reactants and products. The model reliability is tested by comparison with suitable experimental data obtained in a semibatch oxidation reactor, where the role of the composition of both the gaseous and the liquid feed has been investigated. It is shown that the model describes the reactor behavior in any of the regimes which may prevail depending upon the operating conditions and the depletion of liquid reactants in time
Mechanochemical Treatment of Soils Contaminated by Heavy Metals in Attritor and Impact Mills: Experiments and Modeling
No full textAn integrative approach was developed to support the scale-up from lab-into pilot-scale mechano-chemical reactors for immobilize heavy metals in contaminated mining soil
Experiments and modeling of the growth of C. sorokiniana in lab batch and BIOCOIL photobioreactors for lipid production
No full textA novel mathematical model for the quantitative assessment of the effect of dissolved nitrogen on the autotrophic batch-growth and lipid accumulation of C. sorokiniana, is proposed in this work. Model results have been validated through comparison with suitable experimental data performed in lab photobioreactors. Further experiments have been then performed using a BIOCOIL operated in fed-batch mode. The experimental results have been successfully predicted through the proposed model. Therefore, the model might represent a first step toward the development of a tool for the scale-up and optimization of the operating conditions of BIOCOIL photobioreactors. Furthermore, the fatty acid methyl esters obtained by transesterification of lipids extracted from C. sorokiniana, have been analysed in view of the assessment of their usability for producing biofuels. Subsequently, on the basis of the fatty acids profile, a wide range of biodiesel fuel properties have been predicted through suitable software
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