Transport properties of catalyst supports studied by pulsed field gradient (PFG) and 2D exchange (EXSY) NMR spectroscopy

The self-diffusivity of xenon and n -hexane in alumina supports was measured by 129 Xe and 1 H PFG NMR. The obtained values were used to evaluate the tortuosity of the complex porosity of the aluminas. The pore connectivity was investigated by 129 Xe 2D EXSY NMR. The exchange rates of xenon atoms between different pore domains and between the adsorbed and gas phase were determined using a two-site exchange model. The exchange rate together with the diffusivity values allowed evaluating the mean size of the pore domains. 2D-EXSY and PFG 129 Xe NMR provide a powerful means for probing tortuosity and pore connectivity in bimodal alumina catalysts.