Gas adsorption in mesoporous micelle-templated silicas: MCM-41, MCM-48, and SBA-15.
This paper reports a molecular simulation and experimental study on the adsorption and condensation of simple fluids in mesoporous micelle-templated silicas MCM-41, MCM-48, and SBA-15. MCM-41 is described as a regular cylindrical silica nanopore, while SBA-15 is assumed to be made up of cylindrical nanopores that are connected through lateral channels. The 3D-connected topology of MCM-48 is described using a gyroid periodic minimal surface. Argon adsorption at 77 K is calculated for the three materials using Grand Canonical Monte Carlo simulations. Qualitative comparison with experiments for nitrogen adsorption in mesoporous micelle-templated silicas is made. The adsorption isotherm for SBA-15 resembles that for MCM-41. In particular, capillary condensation and evaporation are not affected by the presence of the connecting lateral channels. In contrast, the argon adsorption isotherm for MCM-48 departs from that for MCM-41 having the same pore size. While condensation in MCM-41 is a one-step process, filling of MCM-48 involves two successive jumps in the adsorbed amounts which correspond to condensation in different domains of the porosity. The condensation pressure for MCM-48 is larger than that for MCM-41. We attribute this result to the morphology of the MCM-48 surface (made up of both concave and convex regions) that differs from that for MCM-41 (concave only). Our results suggest that the pore connectivity affects pore filling when the size of the connections is comparable to that of the nanopores.
Coasne
Benoit
B
Laboratoire de Physicochimie de la Matière Condensée, Institut Charles Gerhardt, UMR 5617 CNRS and Université Montpellier 2, Place Eugène Bataillon, 34095 Montpellier Cedex 05, France. bcoasne@lpmc.univ-montp2.fr
Galarneau
Anne
A
Di Renzo
Francesco
F
Pellenq
Roland J M
RJ
D000327:Adsorption; D001128:Argon / Q000737:chemistry*; D008823:Micelles; D016062:Porosity; D012822:Silicon Dioxide / Q000737:chemistry*
C509968:MCM-41; D008823:Micelles; C509969:SBA-15; D001128:Argon; D012822:Silicon Dioxide