Carbon Molecular Sieves Prepared from Polymeric Precursors: Porous Structure and Hydrogen Adsorption Properties

Abstract

The textural characterization of a series of carbon molecular sieves (CMS) prepared from different polymer precursors has been investigated using N2 adsorption at 77 K and CO2 adsorption at 273 K, together with immersion calorimetry into liquids of different molecular dimensions. Experimental results show that the carbon molecular sieves cover a wide range of porosity, from pure microporous CMS (pore diameter below 0.56 nm) to CMS combining larger micropores (above 0.7 nm) together with a certain proportion of mesoporosity. H2 adsorption measurements on these CMS at cryogenic temperature (77 K) and ambient pressure (0.1 MPa) show that the hydrogen adsorption capacity exhibits a linear correlation with the volume of narrow micropores (V n). Furthermore, these results confirm experimentally the necessity of a tailored micropore size in order to achieve an optimum packing density of the adsorbed hydrogen molecules (micropore size around 0.6 nm).

CO2 adsorption on binderless activated carbon monoliths

“…Apparently, narrow micropores (pores below 0.7 nm) are responsible for the adsorption of a small molecule such as CO 2 (kinetic diameter 0.33 nm) under these experimental conditions. Similar correlations with the volume of narrow micropores has been described in the literature for the adsorption of a similar molecule (in a dimension basis) such as hydrogen (kinetic diameter 0.29 nm) into commercial carbon molecular sieves (Silvestre-Albero et al 2009). The crucial role of the narrow microporosity in the adsorption of CO 2 at atmospheric pressure can explain the excel- Correlation between the amount of CO 2 adsorbed at atmospheric pressure and 273 K for the different activated carbon monoliths, and the different textural parameters (S BET , V 0 (N 2 ) and V n (CO 2 )) lent results recently described by Wahby and co-workers for CO 2 adsorption, with total amount adsorbed on highsurface area carbon molecular sieves (V n above 1.40 cm 3 /g) of ∼380 mg CO 2 /g, this value being even larger than those reported in the literature for traditional adsorbents such as zeolites and MOF materials (Bae et al 2008(Bae et al , 2009Himeno et al 2005;Inagaki 2009, Kapoor andYang 1989;Wahby et al 2010;Yazaydin et al 2009).…”

An accurate model for the filling pressure of carbon slit-like micropores

“…We obtained S BET = 1750 AE 50 m 2 /g. Previous published results for Carboxen-1012 provide a specific surface area included between 1375 m 2 /g [22] and 2000 m 2 /g [23] in agreement with our measurement.…”

CO2 adsorption on carbon molecular sieves

“…The selected CMS cover different pore size distributions, and all of them are commercially available from Supelco. Preparation conditions and particle size distribution, for some CMS, were detailed elsewhere [32].…”