Abstract
The microscopic diffusivity of methane (CH4) confined in nano-porous carbon aerogel was investigated as a function of added carbon dioxide (CO2) and nitrogen (N2) pressure using quasi-elastic neutron scattering (QENS). In the range of the external pressure of 1-2.5 MPa, the self-diffusivity of methane was found to increase with CO 2 pressure and remain practically unchanged in the N2 environment. Increasing mobility of methane with CO2 pressure suggests that the adsorbed CH4 molecules become gradually replaced by CO2 on the surface of carbon aerogel pores, whereas the presence of N2 does not induce the replacement. The molecular mobility of the methane, with or without added carbon dioxide and nitrogen, is described by the unrestricted diffusion model, which is characteristic of methane compressed in small pores. On the other hand, both nitrogen and carbon dioxide molecules in carbon aerogel, when studied alone, with no methane present, follow a jump diffusion process, characteristic of the molecular mobility in the densified adsorbed layers on the surface of the aerogel pores.
Original language | English |
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Pages (from-to) | 101-106 |
Number of pages | 6 |
Journal | Microporous and Mesoporous Materials |
Volume | 148 |
Issue number | 1 |
DOIs | |
State | Published - Jan 15 2012 |
Funding
This research at Oak Ridge National Laboratory’s Spallation Neutron Source and High Flux Isotope Reactor was sponsored by the Laboratory Directed Research and Development Program and the Scientific User Facilities Division, Office of Basic Energy Sciences, US Department of Energy. This research was supported in part by the ORNL Postdoctoral Research Associates Program, administered jointly by the ORNL and the Oak Ridge Institute for Science and Education.
Keywords
- Aerogel
- Diffusivity
- Methane
- Neutron scattering