DIFFUSION IN POROUS CATALYST GRAINS AS STUDIED BY EPR IMAGING

Diffusion of the spin probe perchlorotriphenylmethyl into the solvent- saturated porous catalyst support prepared from two types of aluminium oxide (Al2O3) and into pure solvent (CCl4) is studied by EPR imaging. By comparison of the experimental tomograms (spectra in nonuniform ma gnetic field) with the computed ones obtained on: the basis of the Fic k's diffusional equation solution, the effective diffusion coefficient s D-e are determined and values of tortuosity are estimated. Two-dimen sional spatial distribution of spin probe 2,2,6,6-tetramethyl-4-hydrox ypiperidine-1-oxyl at different times of diffusion into alumina suppor t are detected and D-e is estimated to be less than 6 x 10(-8) cm(2)/s .