This paper presents an one-dimensional isothermal modelling for a three-phase trickle bed system (N2/H2O- NaC6H11O7/??-Al2O3, 298K, 1.01 bar). The transient behavior was studied using a dynamic tracer method. The system has been operated with liquid and gas phases flowing downward with constant gas flow Qg = 2.86x10-6 m3 s-1 and the liquid phase flow Ql varying in the range from 4.95x10-6 m3 s-1 to 1.25x10-6 m3 s-1. The evolution of the NaC6H11O7 concentration in the aqueous liquid phase was measured at the exit of the reactor in response to the concentration increase at the reactor inlet. A mathematical model was developed and the solutions of the equations fitted to the measured tracer concentrations. The order of magnitude of the axial dispersion and liquid-solid mass transfer coefficients were estimated based on a numerical optimization procedure where the initial values of these coefficients, obtained by empirical correlations, were modified by comparing experimental and calculated tracer concentrations. The final optimized values of the coefficients were calculated by the minimization of a quadratic objective function. Two correlations were proposed to estimate the parameters values under the conditions employed. By comparing experimental and predicted tracer concentration step evolutions under different operating conditions the model was validated.