Multilayer adsorption equilibrium model for gas adsorption on solids
- PDF / 431,777 Bytes
- 9 Pages / 595.276 x 790.866 pts Page_size
- 10 Downloads / 222 Views
Multilayer adsorption equilibrium model for gas adsorption on solids Sébastien Thomas · Pierre Schaetzel
Received: 22 October 2011 / Accepted: 17 September 2012 / Published online: 11 October 2012 © Springer Science+Business Media New York 2012
Abstract Adaptation of the ENSIC model to physisorption of nitrogen or argon on a solid surface first led to a 3 parameters model called multilayer adsorption equilibrium model (MAE model). One of these parameters is related to the formation of a multilayer of adsorbate on the solid surface. Exploitation of data from the literature pointed out that this parameter does not depend on the nature of the solid surface and an average value was calculated in the case of N2 and Ar. As a consequence, the MAE model can be considered as a 2 parameters model. Linearization of the model was established allowing an easy determination of surface areas of macroporous and some mesoporous solids. Fitting of isotherms of meso and macroporous solids has led to promising results compared to the ones obtained with the BET model. Moreover, adaptation of this model to microporous solids can also be used for an uncomplicated determination of porous volume and external surface. Results obtained from data of the literature were close to those obtained with the t-plot model. Keywords Adsorption isotherm · Surface area · Pore volume · Mesoporous solid · Microporous solid
2004), drug hosts (Ramila et al. 2003; Anglin et al. 2008) or sensors (Leite et al. 2010; Whalley et al. 2001). In fact, in addition to attractive chemical surface properties, high surface areas and specific pore systems are often required to enhance solid properties. Characterization and quantification of these two last parameters are generally obtained from physisorption isotherms (Sing et al. 1985), which have been the subject of many reviews (Ramsay 1998; Leofanti et al. 1998; Sing and Williams 2005; Rodrigues et al. 1989). Among models describing the adsorption isotherm, the BET model, developed by Brunauer, Emmett and Teller (Brunauer and Emmett 1938; Brunauer 1945), is the most widely used. It allows an easy determination of the surface area of non-microporous solids. This model is based on uniformity of the surface and on the absence of lateral interactions of adsorbed molecules. Moreover, this model implies that the second and further layers can start to build up before the completion of the first one. Based on these hypotheses, adsorption and desorption rates can be expressed as function of the partial pressure and of the proportion of each adsorbed layer. At equilibrium, adsorption and desorption rates on each layer are supposed to be equal. This results in a 2 parameters equation:
1 Introduction Porous materials are of great interest in many fields such as heterogeneous catalysis (Ramsay 1998), separation processes such as chromatography (Thielmann et al. 2001; Rodrigues 1997) or membranes (Blanco et al. 2006; Yan et al. S. Thomas () · P. Schaetzel Laboratoire Catalyse et Spectrochimie, ENSICAEN, Université de Caen, CNRS,
Data Loading...
