Recrystallization on Alkaline Treated Zeolites in the Presence of Pore-Directing Agents

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.,

DOI: 10.1021/acs.cgd.7b01416



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.


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