Discontinuous Tank Reactor Research Articles

Kinetic Study of the Enzymatic Synthesis of 2-Phenylethyl Acetate in Discontinuous Tank Reactor

There is increasing interest in new processes to produce aromatics labeled as “natural”, and as a consequence, enzymatic processes, in some organic solvent or in solvent-free medium, have been deve...

Application of a diffusion-reaction kinetic model for the removal of 4-chlorophenol in continuous tank reactors

A continuous tank reactor was used to remove 4-chlorophenol from aqueous solutions, using immobilized soybean peroxidase and hydrogen peroxide. The influence of operational variables (enzyme and substrate concentrations and spatial time) on the removal efficiency was studied.By using the kinetic law and the intrinsic kinetic parameters obtained in a previous work with a discontinuous tank reactor, the mass-balance differential equations of the transient state reactor model were solved and the theoretical conversion values were calculated. Several experimental series were used to obtain the values of the remaining model parameters by numerical calculation and using an error minimization algorithm.The model was checked by comparing the results obtained in some experiments (not used for the determination of the parameters) and the theoretical ones.The good concordance between the experimental and calculated conversion values confirmed that the design model can be used to predict the transient behaviour of the reactor.

Screening of three commercial plant peroxidases for the removal of phenolic compounds in membrane bioreactors

A comparative study of three plant peroxidases, horseradish (HRP), soybean (SBP) and artichoke (AKPC), was carried out to select the most appropriate one for 4-chlorophenol treatment in an ultrafiltration membrane reactor. Soybean peroxidase showed the highest enzymatic activity, followed by HRP and AKPC. The same tendency was observed in a discontinuous tank reactor, where SBP attained more than 90% of 4-chlorophenol removal within the pH range tested. The optimum temperature was 30 °C, with SBP showing highest thermostability. With the ultrafiltration membrane reactor, SBP attained the highest operational stability, with 4-chlorophenol conversions of around 90% in the permeate stream for up to 200 minutes. Finally, permeate samples were analysed and no significant amount of enzyme was detected, so the observed loss of activity, less pronounced with SBP, was attributed to enzyme adsorption on the polymeric products deposited on the membrane surface. Soybean peroxidase was selected as the most appropriate peroxidase for future research.

A diffusion-reaction kinetic model for the removal of aqueous 4-chlorophenol with immobilized peroxidase

A diffusion-reaction kinetic model is presented for the kinetic analysis of the removal process of phenolic compounds using hydrogen peroxide and immobilized peroxidase. The good results obtained in the fitting of the experimental data to the model confirm its validity, in the experimental range considered, as well as the one of the extended version of the Dunford mechanism proposed in a previous paper.The phenomenon of enzyme deactivation and/or sequestration by the precipitated olygomers/polymers, which has been widely described in the literature, is here modeled as the growth of a polymeric film over the external surface and inside the pores of the catalytic particles that contain the enzyme, thus determining the appearance of diffusional limitations and an increasing loss of activity. The deactivation phenomena, interpreted and modeled in terms of the effectiveness factor, are included in the kinetic model.To confirm the validity of the model, several series of experiments were carried out in a discontinuous tank reactor. Some of these experimental series were used to obtain the values of the kinetic parameters by numerical calculation and using an error minimization algorithm. Since the model reproduces the behavior of the system for the series of experiments not used for the determination of the parameters, it can be affirmed that the model is suitable for the kinetic analysis of the system under study.

Removal of 4-chlorophenol by soybean peroxidase and hydrogen peroxide in a discontinuous tank reactor

A discontinuous tank reactor was used to eliminate 4-chlorophenol using soybean peroxidase (SBP) and hydrogen peroxide in an attempt to reduce the concentrations of buffer solutions used and to avoid adding polyethylene glycol. The stirred-tank reactor was operated in different operating conditions, and the influence of enzyme and substrate concentrations on the elimination of 4-chlorophenol was determined. Most of the assays provided good elimination percentages, which reached almost 90% for an enzyme concentration of 7.5·10 –3 mg cm –3 and a stoichiometric ratio of 1:1 for both substrates, when concentrations of 1.5 mmol dm –3 or less were used. This work is a first step in the study of the SBP/4-chlorophenol system in order to observe the influence of the reagents concentrations when no polyethylene glycol is added.

Degradation of Propoxur by ozone

Abstract The kinetics of the reaction between ozone and the insecticide Propoxur (also known as Baygon) is studied from ozone absorption experiments carried out in a semicontinuous tank reactor. Mass transfer coefficients and interfacial areas for the reactor were determined previously, and a stoichiometric ratio of 3 moles of ozone consumed per mole of Propoxur reacted is deduced from homogeneous experiments in a discontinuous tank reactor. The overall reaction orders and rate constants are determined following the film theory which is applied to the experimental data, and a general equation which correlates these constants as a function of pH and temperature is proposed. The process develops in the fast pseudo‐first‐order kinetic regime of absorption.

Protocatechuic acid ozonation in aqueous solutions

The oxidation of protocatechuic acid with ozone in aqueous solution has been studied varying the temperature, pH, ozone partial pressure and initial acid concentration. A stoichiometric ratio of 2 mol of ozone consumed per mol of protocatechuic acid reacted is deduced from homogeneous experiments in a discontinuous tank reactor. In the ozonation experiments, the influence of the operating variables was established and the kinetic regime of ozone absorption was shown to be fast and pseudo m-order with respect to ozone, except at pH 2, when the reaction develops in the moderate kinetic regime. After applying a mass transfer with chemical reaction model, the reaction orders are deduced and the kinetic rate constants are determined as a function of pH and temperature. A modified Arrhenius expression is proposed to correlate them.