Dinâmica de adsorção de metanol em leito fixo de zeólitas.

Abstract

The present work deals with the adsorption of methanol in fixed bed of zeolite pellets. The dynamics of the column was studied by means of the breakthrough curves obtained by a response to a step perturbation at the input. The breakthrough curves were obtained by refractometric analysis of the concentration of the mcthanol'toluene solutions at the output of a 3 cm diameter, 16 cm high column. The concentration of the input solution was varied between 10% and 20% by weight of methanol in toluene with a flow rate from 0,32 ml/s to 4,4 ml/s. All the experiments were done with input temperature in turn of 30°C . The breakthrough curves are influenced by the flow rate as well as by the input concentration. It was observed that the effect of flow rate is more important at low input concentrations. In these situations it may be observed that the axial dispersion tends to be negligible as the flow rate increases. It was also observed that the rate of adsorption increases with the input concentration. Nevertheless, this effect is only important for the breakthrough curves obtained at low flow rates. The Thomas model, for Langmuir equilibrium, and The Adams & Burhart model, as a limit to rectangular isotherms were used to model the dynamics of the column. Both models were chosen based in previous results obtained about equilibrium isotherms of the system. The global transfer coefficients were estimated by fitting the experimental breakthrough curves. In spite of the drastic simplifying hypothesis, both models fit well the experimental data. Nevertheless, the Thomas model predicts the breakthrough curves with good agreement in all the situations studied in this work but the Adams & Borhart model is worst, specially at low flow rate. The transfer parameters obtained in this work are useful for the knowledge of the dynamics of adsorption of methanol in fixed bed of zeolite 4A pellets.