Kinetics of adsorption of n-butane on an aggregate of silicalite by transient non-equilibrium molecular dynamics

Here we present the results obtained by using a transient non-equilibrium molecular dynamics procedure (TNEMD) which allows us to study the kinetics of gas adsorption at different gas pressures. Our simulations were focused on the adsorption of n-butane on aggregates of silicalite at 300 K. These simulations give relevant information on both the equilibrium state and the kinetics of adsorption. The isotherms obtained are in agreement with previous experimental and simulated results. At the equilibrium state our simulations allowed us to identify five energetic sites on the aggregate: three inside the micropores (straight and zig-zag channels and their intersections) and two additional ones at the external surface. Moreover, our simulations show, as determined exprimentally, that the n-butane is adsorbed on the external sites of the zeolite only at high filling (high loadings) of the zeolite-i.e. close to the saturation. From the simulated kinetics we calculated the Fick's diffusion coefficients at different loadings.