Didier Anglerot

Synthesis, characterization, and catalytic properties of silica-rich faujasite-type zeolite (FAU) and its hexagonal analog (EMT) prepared by using crown-ethers as templates

High silica faujasite (FAU) and its hexagonal analog (EMT) were synthesized using 15-crown-5 and 18-crown-6, respectively, as templating agents. By mixing these two crown-ethers in the starting hydrogel, a material with a crystal morphology resulting from an overgrowth of both cubic and hexagonal structures was obtained. These three zeolites with a SiAl molar ratio close to 4 were ion-exchanged and transformed into their protonated forms. The samples were characterized by chemical analysis, 29Si, 27Al, and 23Na solid-state MAS n.m.r., and it was shown that the sodium removal was more complete in the hexagonal and overgrown samples. The acidity (determined by STD of ammonia) and the catalytic activity (evaluated by n-heptane cracking) are closely related to the residual amount of Na+, and they proved to be higher for the two latter samples.

Single step dealumination of zeolite beta precursors for the preparation of hydrophobic adsorbents

Abstract Zeolite beta precursors containing the occluded organic template have been dealuminated by reaction with nitric acid solution at reflux temperature. Si/Al ratios greater than 1000 can be obtained in a single step, without significant loss of crystallinity, porous volume and thermal stability. The dealuminated zeolite contains mesopores and three types of silanol defect groups. The latter are readily annealed by calcination. Dealuminated zeolite beta exhibits a strong hydrophobic/organophilic character.

Investigations of the structure orienting role of acyclic molecules containing (—OCH2CH2—) groups in the synthesis of high-silica faujasitelike zeolites

Abstract The possible structure-directing role of acyclic (—OCH2CH2—)-containing molecules in the synthesis of faujasitelike zeolites was investigated. FAU silica-rich frameworks were obtained by using tris(3,6-dioxaheptyl)amine (TDA-1) and poly(ethylene oxides) (PEO) with a molecular weight ranging from 2000 to 8000. The solids were characterized by chemical analysis, thermal analysis, and MAS n.m.r. spectroscopy. The Si/Al molar ratios (3.4–3.6) are higher than those of conventional Y zeolite (2.7) but slightly lower than the Si/Al ratio of a FAU zeolite prepared in the presence of 15-crown-5 (3.8). The acid properties of the materials synthesized with PEO 3400, TDA-1, and 15-crown-5 were studied comparatively by NH3 STD.