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Adsorption

, Volume 13, Issue 5–6, pp 425–437 | Cite as

Argon and krypton adsorption on templated mesoporous silicas: molecular simulation and experiment

  • Francisco R. Hung
  • Supriyo Bhattacharya
  • Benoit Coasne
  • Matthias Thommes
  • Keith E. GubbinsEmail author
Article

Abstract

In this work we report molecular simulation results for argon and krypton adsorption on atomistic models of templated mesoporous silica materials. These models add atomistic levels of detail to mesoscale representations of these porous materials, which were originally generated from lattice Monte Carlo simulations mimicking the synthesis process of templated mesoporous silicas. We generate our atomistic pore models by carving out of a silica block a ‘mathematically-smooth’ representation of the pores from lattice MC simulations. Following that procedure, we obtain a model material with mean mesopore and micropore diameters of 5.4 nm and 1.1 nm, respectively (model A). Two additional model materials were considered: one with no microporosity, and with mesopores similar to those of model A (model B), and a regular cylindrical pore (model C). Simulation results for Ar and Kr adsorption on these model materials at 77 K and 87 K shows that model A provides the best agreement with experimental data; however, our results suggest that fine-tuning the microporosity and/or the surface chemistry (i.e., by decreasing the density of OH groups at the pore surface) of model A can lead to better agreement with experiments. The filling of the mesopores in model materials A and B proceeded via a classical capillary condensation mechanism, where the pores fill at slightly different pressures. This observation contrasts with what was observed in our previous study (Coasne, et al. in Langmuir 22:194–202, 2006), where we considered atomistic silica mesopores with an important degree of surface roughness at length scales below 10 Å, for which we observed a quasi-continuous mesopore filling involving intermediate phases with liquid-like “bridges” and gas-like regions. These results suggest that pore surface roughness, and other morphological features such as constrictions, play an important role in the mechanism of adsorption and filling of the mesopores.

Keywords

Templated mesoporous silica materials MCM-41 SBA-15 Gas adsorption Molecular simulation Monte Carlo 

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Copyright information

© Springer Science+Business Media, LLC 2007

Authors and Affiliations

  • Francisco R. Hung
    • 1
  • Supriyo Bhattacharya
    • 2
    • 3
  • Benoit Coasne
    • 4
  • Matthias Thommes
    • 5
  • Keith E. Gubbins
    • 2
    Email author
  1. 1.Department of Chemical and Biological EngineeringUniversity of WisconsinMadisonUSA
  2. 2.Center for High Performance Simulation and Department of Chemical and Biomolecular EngineeringNorth Carolina State UniversityRaleighUSA
  3. 3.City of Hope National Medical CenterBeckman Research InstituteDuarteUSA
  4. 4.Institut Charles Gerhardt Montpellier, CNRS (UMR 56253)University Montpellier 2, and ENSCMMontpellierFrance
  5. 5.Quantachrome InstrumentsBoynton BeachUSA

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