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

In the present work the kinetics of absorption of propylene in Ag+-BMImBF4 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 (EA) due to the presence of the chemical reaction indicate that for concentrations equal to or higher than 0.25 M of Ag+ in BMImBF4 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 (kL) was obtained in a non-reactive BMImBF4 medium as a function of stirring speed and temperature, showing a significant increase from 1.61 × 10-6 to 17.9 × 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+-BMImBF4 are reported in order to predict the diffusion coefficient of propylene in the absorptive media. Diffusivity of the silver ions in BMImBF4 has been determined by the chronoamperometry technique, showing a concentration dependency in the range of AgBF4 = [0.05–0.25 M].