Modelling gas permeation through new microporous titanosilicate AM-3 membranes

Titanosilicate AM-3 membrane: A new potential candidate for H2 separation

“…The permeances of N 2 , CO 2 , and O 2 over the temperature range are almost constant. It is well known that when temperature increases the permeance due to viscous flow through macropores and Knudsen diffusion through mesopores decreases, while the permeance due to activated diffusion through micropores increases [24,25]. The constant permeance over the temperature range studied strongly suggests the existence of an activated contribution which compensates the lowering effect of the viscous and Knudsen components.…”

Inorganic microporous membranes for H2 and CO2 separation—Review of experimental and modeling progress

“…Lee (2007) Compared to hydrocarbons, light gases such as H 2 , CO 2 and N 2 exhibit a relatively "weak" adsorption on zeolites and tend to show activated behavior. Therefore some researchers turn to a concept of combined mechanisms for the transport of light gases, which includes surface diffusion and activated diffusion through micropores and Knudsen diffusion (plus viscous flow) through defects in the zeolite layer (Wirawan et al,2011;Hanebuth et al, 2005;Lito et al, 2010). These transport mechanisms are assumed to occur in parallel within the micropores, as shown in Fig.…”

“…16. The investigations over two microporous titanosilicate AM-3 membranes with distinct qualities indicated that Knudsen diffusion and viscous flow are the dominant transport mechanisms through the low quality membrane, while activated diffusion prevailed for the high quality membrane, especially at high temperatures (Lito et al, 2010). Hanebuth et al (2005) concluded that the concept of combined mechanisms is only valid for dilute systems at high temperatures, where little interaction exists between adsorbed and desorbed molecules and further no interference between the flow path of surface diffusion, activated diffusion and Knudsen diffusion.…”

“…For example, in the study of gas permeation through titanosilicate AM-3 membranes, the embodied parameters for different transport mechanisms are derived by fitting to gas permeation data (Lito et al, 2010). For a low quality titanosilicate AM-3 membrane, H 2 permeance is dominated by Knudsen diffusion through defects with a minor contribution from viscous flow.…”

“…Yet, it is challenging to obtain the model parameters for two mechanisms respectively. One possibility is by fitting model predictions to experimental data (Lito et al, 2010;Wirawan et al, 2011). For example, in the study of H 2 and CO 2 permeation through a silicalite-1 composite membrane (Wirawan et al, 2011), the adsorption parameters are referred to literature values while diffusion parameters for both surface diffusion and activated transport are obtained through a non-linear regression fit using LSQNONLIN in MATLAB 6.5.…”