The Hydrothermal Synthesis of Zeolites: History and Development from the Earliest Days to the Present Time

The literature on open-framework materials has shown numerous examples of porous solids with additional structural, chemical, or physical properties. These materials show promise for applications ranging from sensing, catalysis and separation to multifunctional materials. This critical review provides an up-to-date survey to this new generation of multifunctional open-framework solids. For this, a detailed revision of the different examples so far reported will be presented, classified into five different sections: magnetic, chiral, conducting, optical, and labile open-frameworks for sensing applications. (413 references.)

Old materials with new tricks: multifunctional open-framework materials.

This short review describes the evolution of the nature of microporous solids and the related concepts that were at the origin of this evolution. The paper begins with the different families of classical organically templated inorganic porous solids, their parameters of synthesis, the mechanisms of formation, their consequences, and their limits. From the latter, the concept of hybrid organic−inorganic frameworks is introduced as well as their tentative classification according to the decrease of the dimensionality of the inorganic subnetwork. The last part of the paper is devoted to the new trends in the field:  the creation of very large pores, their design from topological considerations, and the introduction of computational methods.

Microporous Solids: From Organically Templated Inorganic Skeletons to Hybrid Frameworks...Ecumenism in Chemistry

Siliceous mesostructured cellular foams (MCFs) with well-defined ultralarge mesopores and hydrothermally robust frameworks are described. The MCFs are templated by oil-in-water microemulsions and are characterized by small-angle X-ray scattering, nitrogen sorption, transmission electron microscopy, scanning electron microscopy, thermogravimetry, and differential thermal analysis. The MCFs consist of uniform spherical cells measuring 24−42 nm in diameter, possess BET surface areas up to 1000 m2/g and porosities of 80−84%, and give, because of their pores with small size distributions, higher-order scattering peaks even in the absence of long-range order. Windows with diameters of 9−22 nm and narrow size distribution interconnect the cells. The pore size can be controlled by adjusting the amount of the organic swelling agent that is added and by varying the aging temperature. Adding ammonium fluoride selectively enlarges the windows by 50−80%. In addition, the windows can be enlarged by postsynthesis treatm...

Microemulsion Templating of Siliceous Mesostructured Cellular Foams with Well-Defined Ultralarge Mesopores

The conditions required to produce zeolites with low framework density and extra-large pores are discussed. Correlations between framework stability and geometrical and topological descriptors are presented. An attempt has been made to rationalize the synthesis of extra-large-pore zeolites in terms of the synthesis mechanism, the directing effect of the organic structure directing agent (OSDA), the framework atoms, and the gel concentration. Extra-large-pore zeolites, including the recently discovered chiral mesoporous ITQ-37, are described and their catalytic and adsorption properties discussed. Finally, strategies are presented for the preparation of extra-large-pore zeolites with different pore topologies that can fulfill pre-established catalytic and adsorption targets.

Extra‐Large‐Pore Zeolites: Bridging the Gap between Micro and Mesoporous Structures

Silica-rich, Al-, B- and (Al + B) MFI zeolites called Zeosilites, Aluzeosilites, Borozeosilites and Aluborozeosilites respectively were obtained by hydrothermal crystallization at 60–200°C from mixtures containing F anions and tetra-, tri- and di-propylamraonium cations as templates; pH values were 3–10. Crystal size is a function of the Si substitution degree, it may reach 800 um in some cases. DSC, DTA and TG curves corresponding to the decomposition of the templates occluded as fluoride salts are different from those observed for samples obtained in alkaline medium. Mass spectrometer analysis shows that the presence of fluoride in the as-synthesized samples leads to organic fluro compounds formation on calcination. High resolution 29 si-, 27 Al- and 11 B magic angle spinning NMR evidences Si substitution by Al and B in the zeolite framework.

New Route to Pentasil-Type Zeolites Using a Non Alkaline Medium in the Presence of Fluoride Ions

The invention relates to the preparation of synthetic zeolites selected from the group formed by chabazite, merlinoite, edingtonite, ZSM 5 and ZSM 11. In accordance with the invention, a zeolite selected from the group formed by mordenite, ferrierite, clinoptilolite and the type X and type Y zeolites is subjected to a treatment with at least one base. The invention further relates to zeolites obtained by said process.

Process for the preparation of synthetic zeolites and zeolites obtained by this process

The process consists in forming a reaction mixture comprising especially water, a source of silica, a source of alumina, a source of a structuring agent which can supply cations chosen from the group consisting of tetrapropylammonium (TPA ), tripropylammonium (TRIPA ), dipropylammonium (DIPA ) and tetrapropylphosphonium (TPP ) cations and fluoride anions F , the pH of the mixture being lower than 10, in heating the said reaction mixture to a temperature of between 60 and 230 DEG C, this second stage resulting in the production of a crystalline solid which is separated off, and then heating the said solid to a temperature above 450 DEG C.

Process for synthesizing zeolites of the aluminosilicate-type, products obtained by this process and use thereof

A partly hydrated faujasite zeolite can selectively adsorb p - or m -xylene from a mixture of both isomers according to the nature of its cations (Na + or K + ). Microcalorimetric and Raman laser spectroscopic studies of the adsorption interactions enable us to explain the observed selectivity. The Na + faujasite selectivity for m -xylene is due to the difference in enthalpy of adsorption in favor of m -xylene which is not compensated by the difference in entropy of adsorption, the latter in favor of p -xylene. With K + faujasite the difference in enthalpy of adsorption is not great enough and it is now the difference in entropy of adsorption, always favoring p -xylene, which determines the selectivity.

On the thermodynamic factors governing the adsorption of p- and m-xylene onto faujasite zeolite containing Na+ and K+ cations

The invention relates to the preparation of the zeolite ZK-5 from a starting zeolite selected from the group consisting of the zeolites P (Cl), P' (Cl), Q (Br) and Q' (Br). In accordance with the invention, the barium ions contained in the starting zeolite are extracted therefrom by means of a barium-binding agent selected from the group consisting of precipitating agents which form with the barium ions a compound that precipitates, and of complexing agents which form with the barium ions a barium complex. The zeolite ZK-5 obtained may be used in the separation or cracking of hydrocarbons.

Raymond Wey

Papers

New Route to Pentasil-Type Zeolites Using a Non Alkaline Medium in the Presence of Fluoride Ions

Process for the preparation of synthetic zeolites and zeolites obtained by this process

Process for synthesizing zeolites of the aluminosilicate-type, products obtained by this process and use thereof

On the thermodynamic factors governing the adsorption of p- and m-xylene onto faujasite zeolite containing Na+ and K+ cations

Process for the preparation of zeolite ZK 5