Synthesis of mesoporous-zeolite materials using Beta zeolite nanoparticles as precursors and their catalytic performance in m-xylene isomerization and disproportionation

摘要

Hierarchical Beta nanozeolites with the properties of both Beta nanozeolite and mesoporous material were prepared by two different methods: (1) Direct Hydrothermal Method (DHM) by the assembly of nanocrystals of preformed Beta seeds in the presence of the surfactant P123 under hydrothermal conditions, (2) Acidification of Beta seeds suspension (without the use of the mesopore directing agent). For the two methods, the effect of crystallization time of Beta nanozeolite precursor (seeds) was studied: 6, 12 and 24 h. The obtained materials were characterized using nitrogen sorption measurements, thermogravimetric analysis (TGA), X-ray diffraction (XRD), transmission electron microscopy (TEM), ammonia Temperature Programmed Desorption (NH3-TPD) and adsorption/desorption of pyridine monitored by FTIR. The characterization results show that acidification of Beta seeds suspension leads to best structured nano-Beta (Beta nanoparticles). However, with the DHM method physical mixtures of Beta nanoparticles and mesoporous SBA-15 phases were obtained.