n-Pentane hopping in zeolite ZK-5 studied with13C NMR

Hydrocarbon Behavior at Nanoscale Interfaces

“…The question of interest here is how fast n-pentane molecules can diffuse across the zeolite. Experimental data have been obtained by 13 C NMR techniques when the zeolite was filled with n-pentane (Magusin et al 1999). The results are consistent with a "hopping" diffusion mechanism with molecules jumping between neighboring cages with a hopping rate of 1 to 10 3 jumps per second in the temperature range 247 to 317 K. The resultant self-diffusion coefficient was found to be of the order 10 −18 to 10 −15 m 2 /s.…”

Structural analysis of hierarchically organized zeolites

“…While the diffusion path lengths accessible by pulsed field gradient NMR vary from approximately a hundred nanometres to tens of micrometres, quasielastic neutron scattering is sensitive to displacements over nanometres enabling the rate of molecular displacements within the purely microporous regions to be monitored even in hierarchical pore systems. Complementing information about molecular exchange rates between different pore spaces may be provided by 129 Xe NMR 85 86 and solid state exchange NMR 100 by exploiting their sensitivity to the chemical environment. Simulation studies searching of the structural origin of these resistances are also gaining increasing relevance 101 102 .…”

Nanostructures ofMg0.65Ti0.35Dxstudied with x-ray diffraction, neutron diffraction, and magic-angle-spinningSrinivasan1, Magusin2, Kalisvaart3 et al. 2010Phys. Rev. BSelf Cite

“…In short, this technique correlates the chemical shift before and after a selectable time window t mix , during which the deuterium atoms have the opportunity to move to another environment. [49][50][51] The lack of such correlation between the signals at −43 and −143 ppm in 2D Exsy is inconsistent with the small distance between T and O sites inside the fcc unit cell.…”

“…To study the deuterium exchange quantitatively as a function of, e.g., time and temperature, we have employed the related 1D Exsy technique. 48,51 Systematic 1D Exsy measurement of the transient response of the deuterium spins in the TiD y phase at varying mixing times after a selective polarization inversion of the deuterium spins in the MgD 2 phase indicates an exchange time scale of 0.9 s at room temperature ͓Fig. 6͑c͔͒ with only a weak temperature dependence represented by an effective activation energy of 12 kJ mol −1 ͓Fig.…”