AVILA adolfo Maria
congresos y reuniones científicas
Transient permeation of ternary hydrocarbon mixtures across Y-type zeolite hollow fiber membranes
Zaragoza, España
Conferencia; 4th International Zeolite Membrane Meeting; 2007
Institución organizadora:
University of Zaragoza
The knowledge of the dynamics of the fluxes of different species through membranes is useful for designing separation, microreactor or sensor devices. One of the key aspects of useful simulation techniques is screening the permeation behavior of different mixtures and membrane materials, among which zeolites are showing increasing importance. The permeation of a ternary hydrocarbon mixture was simulated to predict the transient behavior of the components through an ideal Y zeolite membrane, where the effects of crystal defects, membrane support and inter-crystalline resistances were neglected. The transient permeation of a ternary mixture of n-hexane, n-decane and toluene through a 40 mm tubular Y-type zeolite membrane at 250 ºC was modeled based on the Maxwell-Stefan formulation [1] to express hydrocarbon fluxes and the ideal adsorbed solution theory [2] to account for  the different adsorption capacities of the species in the mixture. The required individual adsorption parameters were obtained with a batch fluidized bed reactor [3], and the corresponding diffusion parameters were taken from the literature. The membrane support was considered with negligible resistance to the mass transfer. The prediction of the fluxes showed the characteristic behavior of the interactive diffusion-adsorption process for multi-component systems. For example, the permeate flux of the fastest-diffusing component in the mixture (n-hexane) overshoots its steady-state permeance. This maximum propagates with time toward the membrane permeation side. The transient profiles for the fractional coverage of n-hexane in the mixture develops differently from the one shown when it is a single component. In that case, the fractional coverage at any point in the initially empty membrane increases monotonically from zero to the steady state value. The fractional coverage of n-hexane in the permeation of the ternary mixture, on the contrary, increases above the steady state value and shows a maximum. The fractional coverage profiles for the slowest-diffusing species (toluene) are very similar to those when it is a single component.