USY zeolite mesoporosity probed by NMR cryoporometry

We report on the application of the NMR cryoporometry (C NMR) technique to probe the micro- and mesopore size distributions in industrially important USY zeolites (Si/Al ratio of 30, 15, and 6). The technique provides the clues to small mesopore structure range (20–110 Å) created by various postsynthesis treatments of zeolites like ion exchange, steaming, acid leaching and mesoporization. C NMR is compared with the conventional Barrett-Joyner-Halenda (BJH) model to construct the pore size distributions. Both methods account for the mesopore volume, and under some approximations the micropore volume. The C NMR approach has been effectively applied to the study of extruded samples. It is concluded that the significant increase of mesoporosity in extrudates is more due to the binder possessing this porosity range. The effect of mesoporization when comparing the extrudates of parent sample and mesoporized zeolites is less pronounce than in the initial porous material as observed by both C NMR and BJH pore size distributions. Therefore, an important transport amelioration in extrudates is observed apparently due to alumina playing a role of binder.