Estimating the adsorption characteristics of a methylated amorphous silica membrane from permeation data
Advancing the chemical engineering fundamentals
Membranes and Membrane Science (T2-8P)
Keywords: amorphous silica, adsorption, pervaporation, maxwell-stefan
Knowing the adsorption behavior of permeating components on microporous membranes is of key importance in determining the membrane performance. To describe the mass transport through a membrane using the Maxwell-Stefan equations, data on the adsorption on the membrane material is required. Although, in most cases, the adsorption data can be measured from bulk material, the adsorption behavior on a membrane could differ greatly from the bulk adsorption data [1].
Using the Maxwell-Stefan equations [2], the method proposed here provides a simple way to estimate the adsorption characteristics of the membrane. From the ratio of pure component fluxes measured under pervaporation conditions at different permeate pressures the Langmuir adsorption parameter can be calculated. By calculating the adsorption parameter at different temperatures, the heat of adsorption can be estimated using the Arrhenius type of temperature dependence of the Langmuir adsorption parameter [3].
The pure component single site Langmuir adsorption parameter and heat of adsorption of methanol and ethanol on a methylated amorphous silica membrane (provided by ECN, The Netherlands) are estimated using this method. Pervaporation experiments are conducted at 338, 347, and 360K and the permeate pressure is varied between 10 and 200 mbar. The obtained adsorption isotherm for methanol is comparable to the data measured on bulk silica by deBruijn et al. [4].
1 T. E. Clark, H. W. Deckman, D. A. Cox, and R. R. Chance, Journal of Membrane Science, vol.230, 91 (2004)
2 R. Krishna, R. Baur, Chemical Engineering Journal, vol.97, 37 (2004)
3 Bakker, W. J. W., Structured Systems in Gas Separation thesis, Delft University of Technology (1998)
4 de Bruijn, F. T., J.Gross, Z.Olujic, P.J.Jansens, F.Kapteijn, Industrial and Chemistry Research (2007) in press
Presented Tuesday 18, 13:30 to 15:00, in session Membranes and Membrane Science (T2-8P).
