Preparation of a new micro-mesoporous omega zeolite by hydrothermal route: Effect of crystallization time

This work concerns the preparation of a new micro-mesoporous omega zeolite by hydrothermal route. This method consists of the self-assembly of the omega zeolite precursors with a cethyltrimethyl-ammonium bromide surfactant. Different stages of crystallization were studied in order to determine their impact on the textural and structural properties of the resulting materials. For this, several characterization methods were used such as X-ray diffraction, N2 adsorption/desorption, scanning electron microscopy, and Energy-Dispersive X-ray. The results showed that the processing time significantly influences on the crystallinity, porosity and Si/Al ratio of the resulting materials. A specific surface area almost three times greater than the parent zeolite was obtained when using non-hydrothermally treated zeolite precursors. While the precursors prepared hydrothermally for 48 hours or 72 hours essentially lead to the formation of the microporous phase corresponding to the Omega zeolite. These new properties can open new applications of these solids notably in the catalysis for the conversion of bulky molecules and also in the adsorption of organic and organic pollutants.

Study on the Synthesis of Chabazite Zeolites via Interzeolite Conversion of Faujasites

The interzeolite conversion of faujasite (FAU-type) zeolites to chabazite (CHA-type) zeolite in the presence of N,N,N-trimethyladamantammonium and N,N,N-dimethylethylcyclohexylammonium cations was investigated over a large compositional range by carefully controlling the reaction mixture compositions. Highly crystalline CHA zeolites were also obtained by the transformation of several zeolite types including EMT, LTL, LEV, RTH, and MFI frameworks. The formation of CHA zeolite from FAU zeolite precursors was substantially faster than that from zeolite L with a similar composition. High-silica CHA zeolites were also produced successfully using a mixture of TMAda with a number of less expensive organic structure-directing agents. The CHA zeolite materials have been synthesized with high crystallinity and with a Si/Al ratio ranging from 5 to 140. Our data support the importance of structural similarity between the zeolite precursors, nucleation/crystallization processes, and the zeolite product in the interzeolite conversion compared to conventional amorphous aluminosilicate gels. Our synthetic methods could be used to prepare other 8-membered ring zeolites such as AEI and AFX frameworks, potential candidates for selective catalytic reduction of NOx, light olefin production, and CO2 abatement.

Titanosilicate zeolite precursors for highly efficient oxidation reactions

Titanosilicate zeolite precursors, with open structures of zeolite units and high amounts of catalytically active Ti species, show superior catalytic performance in the oxidative reactions.

Pillaring of layered zeolite precursors with ferrierite topology leading to unusual molecular sieves on the micro/mesoporous border

Pillaring of FER layers gives porous products depending on the temperature of TEOS treatment.