424175 Single-File Diffusion of Gas Mixtures By High Field Diffusion NMR

Tuesday, November 10, 2015: 10:35 AM
255C (Salt Palace Convention Center)
Akshita Dutta1, Poorvajan Sekar1, Muslim Dvoyashkin1,2,3, Clifford R. Bowers3, Kirk J. Ziegler1 and Sergey Vasenkov1, (1)Department of Chemical Engineering, University of Florida, Gainesville, FL, (2)Institute of Chemical Technology, Universitšt Leipzig, Leipzig, Germany, (3)Department of Chemistry, University of Florida, Gainesville, FL

Molecules restricted to diffuse through unidimensional channels so narrow that they cannot pass each other exhibit single-file diffusion (SFD). An important consequence of SFD is a significant slowdown in the growth of MSD with time in comparison to that for normal Fickian diffusion. This property opens a possibility for highly selective separations if one component in the mixture exhibits normal diffusion and another SFD. Inducing SFD in catalytic systems can also be beneficial since single-file conditions offer better control over catalytic reactions. These applications are expected to involve more than one type of sorbate molecules in the single-file channels.  However, currently there are no experimental studies that explore molecular SFD of gas mixtures.

Here, we report the observation of single-file diffusion of pure CO and CH4 as well as their mixture in Ala-L-Val (AV) nanochannels by C-13 pulsed field gradient (PFG) NMR. High magnetic field gradients up to 23 T/m were used to study diffusion in a broad range of diffusion times. Under similar experimental conditions the single-file mobility factor of CH4 was found to be smaller than that of CO in the nanochannels containing only one type of gas molecules. At the same time, the single-file mobilities were the same for both gases in the nanochannels loaded with the gas mixture. The single-file mobility in the mixture sample was intermediate to those obtained in the single-sorbate samples. These results will be discussed in the context of relevant molecular dynamics simulation studies that explore this phenomenon of SFD of gas mixtures.

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See more of this Session: Effects of Confinement on Molecular Properties
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