Kinetics of reactive absorption of propylene in RTIL-Ag+ media

In the present work the kinetics of absorption of propylene in Ag+-BMImBF(4) medium have been analysed, discriminating the kinetic regime and determining the expression and parameters of the rate of reactive absorption as a function of the concentration of both reagents. A stirred cell reactor was used to obtain the kinetic information by loading pure absorption gas and recording the total pressure decrease at different silver salt concentrations [AgBF4 = 0-1 M] at 288-308 K. The experimental values of the enhancement factors (E-A) due to the presence of the chemical reaction indicate that for concentrations equal to or higher than 0.25 M of Ag+ in BMImBF(4) it is possible to assume instantaneous chemical reaction between propylene and silver ions. Therefore, the rate of absorption in this case is governed by the rate at which dissolved C3H6 and Ag+ diffuse to the reaction plane from the G-L interface and liquid bulk, respectively. Physico-chemical parameters necessary to predict the absorption rate have been experimentally determined in this work. The liquid mass transfer coefficient (k(L)) was obtained in a non-reactive BMImBF(4) medium as a function of stirring speed and temperature, showing a significant increase from 1.61 x 10(-6) to 17.9 x 10(-6) m s(-1) when the temperature increased from 288 to 308 K at 500 rpm. Experimental viscosity measurements for the reactive system Ag+-BMImBF(4) are reported in order to predict the diffusion coefficient of propylene in the absorptive media. Diffusivity of the silver ions in BMImBF(4) has been determined by the chronoamperometry technique, showing a concentration dependency in the range of AgBF4 = [0.05-0.25 M]. (C) 2010 Elsevier B.V. All rights reserved.