Behavior of benzene in siliceous faujasite: A comparative study by [sup 2]H NMR and molecular dynamics
- Univ. of California, Santa Barbara, CA (United States)
- Biosym Technologies, Inc., San Diego, CA (United States)
- Inorganic Chemistry Lab., Oxford (United Kingdom)
The diffusion coefficients and activation energies of benzene in siliceous faujasite (D[sup 298] = (4.5 [plus minus] 3.3) [times] 10[sup [minus]10] m[sup 2] s[sup [minus]1], E[sub a] = 10.2 [plus minus] 0.8 kJ mol[sup [minus]1]) and Na-Y (D[sup 298] = (3.6 [plus minus] 1.4) [times] 10[sup [minus]12] m[sup 2] s[sup [minus]1], E[sub a] = 23.5 [plus minus] 0.9 kJ mol[sup [minus]1]) have been determined from [sup 2]H NMR spin-lattice relaxation experiments. Unlike Na-Y where benzene binds to SH cations, no specific adsorption site is observed in the siliceous analogue; this is reflected in significantly higher diffusion coefficients and a lower activation energy. Molecular dynamics simulations of benzene adsorbed in siliceous Y zeolite (D[sup 298] = (2.0 [plus minus] 0.3) [times] 10[sup [minus]9] m[sup 2] s[sup [minus]1]) are in good agreement with the experimental result, and from the trajectories it can be seen that the sorbate maintains close interactions with the walls of the supercage. On the 25-ps time scale of the MD simulation, the behavior of benzene is largely dominated by intracavity rather than intercavity motion. For the slower diffusion of benzene in Na-Y, trajectories over a period of [much gt] 1 ns would be needed to observe intercavity motion. 32 refs., 6 figs., 3 tabs.
- OSTI ID:
- 5575693
- Journal Information:
- Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 97:45; ISSN JPCHAX; ISSN 0022-3654
- Country of Publication:
- United States
- Language:
- English
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ADSORPTION
AROMATICS
BENZENE
CATALYSTS
CATALYTIC CRACKING
CHEMICAL ACTIVATION
CHEMICAL REACTIONS
COMPUTERIZED SIMULATION
CRACKING
DATA
DECOMPOSITION
DIFFUSION
EXPERIMENTAL DATA
FAUJASITE
HYDROCARBONS
INFORMATION
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
MAGNETIC RESONANCE
MATERIALS
MINERALS
NUCLEAR MAGNETIC RESONANCE
NUMERICAL DATA
ORGANIC COMPOUNDS
PYROLYSIS
RELAXATION
RESONANCE
SILICATE MINERALS
SIMULATION
SORPTION
SPIN-LATTICE RELAXATION
THEORETICAL DATA
THERMOCHEMICAL PROCESSES
ZEOLITES