Enhanced n-hexane diffusion in partially filled MCM-41 of different surface hydrophobicity probed by NMR

The effect of pore surface hydrophilic/hydrophobic character on n-hexane di ffusion within MCM-41 particles was investigated by PFG NMR at different po re fillings. Starting with totally filled pores, the n-hexane diffusivity w ithin MCM-41 particles is significantly enhanced as the pore filling is dec reased until it reaches a maximum value. The diffusivity is shown to declin e again at a very low pore filling. This is rationalized in terms of a a th ree-component parallel diffusion mechanism, in which a surface diffusion, a n interface diffusion and a liquid phase diffusion are involved. The influe nce of surface property variations on the molecular diffusivity in MCM-41 i s enhanced in partially filled samples. (C) 2000 Elsevier Science B.V. All rights reserved.