by Eddy Dib, Hussein El Siblani, Shrikant M Kunjir, Aurelie Vicente, Nicolas Nuttens, Danny Verboekend, Bert F Sels, and Christian Fernandez in Cryst. Growth Des.,
In previous works aiming at understanding the mesoporous network after alkaline treatment in presence of organic additives, conventional bulk characterization techniques led to the con- clusion that the dissolved zeolite does not undergo any kind of recrystallization [Verboekend et al. Cryst. Growth. Des., 2103, 5025-5035]. Here for the first time, we demonstrate us- ing the data obtained from 1H and 129Xe NMR spectroscopy that such recrystallization does occur, which lead to the formation of a very thin coating of the mesopore walls. This demon- stration is done on a beta (BEA) zeolite treated in presence of TPA+ in an alkaline solution. The formation of a small amount of nanosized crystals or embryonic phases of silicalite- 1 (MFI) zeolite is evidenced, as well as their homogeneous dispersion on the mesoporous surface of the beta zeolite. We think that these results may explain why a homogeneous mesopore size distribution is obtained, when organic pore-directing agents are used in the zeolite hierarchization process performed in an alkaline medium.