Synthesis of molecular sieve

Szostak R 1998 Synthesis of molecular sieve phosphates Molecular Sieves Science and Technology vol 1, ed H G Karge and J Weitkamp (Berlin Springer) pp 157-85... 

During the last 20 years, great progress was made in the synthesis of molecular sieves (Table 1.1) and in the understanding of the catalytic transformation of organic molecules on zeolites. This fundamental knowledge was successfully... 

The Poitiers School was held in an informal and friendly atmosphere, giving the opportunity to world famous academic and industrial experts, as well as PhD students, to exchange their views. The key role of zeolites in sustainable development and the constant creativity and dynamism of academic and industrial researchers in the synthesis of molecular sieves, and in the design and development of new zeolite catalysts were particularly emphasized. 

The synthesis of molecular sieves with large pores is of great importance for many applications such as catalysis, separation, adsorption and fabrication of various quantum materials [1-7]. With the recent discovery of hexagonal and cubic large pore mesoporous materials (SBA-15, SBA-16, FDU-1) [2,3], block copolymers have turned out to be valuable supramolecular templates for the synthesis of ordered large pore mesoporous materials because of their facile structure-directing ability, low-cost commercial availability and biodegradability. 

Nair BN, Yamagushi T, Okubo T, Suematsu H, Keizer K, and Nakao S-I. Sol-gel synthesis of molecular sieving silica membranes. J. Membr. Sci. 1997 135 237-243. 

J. Lin, J. Dipre, and M. Yates, Microemulsion-directed Synthesis of Molecular Sieve Fibers. Chem. Mater., 2003, 15, 2764-2773. 

Morris, Weigel 1997 Synthesis of molecular sieves from non-aqueous solvents [261... 

Microwave synthesis of molecular sieves is a very useful alternative approach, in which case the synthesis proceeds in microwave-transparent glass or plastic reaction vessel. The benefits of nanoporous synthesis under microwave conditions have been reported [12,13]. The most apparent advantage of microwave synthesis is a substantial shortening of the synthesis time. In addition, the special conditions of microwave synthesis can lead also to higher product selectivity [14]. 

After a brief review on the templating role of F in the synthesis of molecular sieves, this study focuses on the transformation of Mu-3 into Mu-2, two fluorinated gallophosphates with ID and 3D arrangement of fluorinated D4R units respectively. Depending on the water content and on the temperature, Mu-2 or another gallophosphate free of D4R units crystallizes. The transformation is studied by XRD analysis and NMR spectroscopy. The different results obtained show clearly that this transformation does not occur via a complete dissolution. Based on the F NMR spectra, the presence of a fluorinated D4R unit, in the solution, cannot be excluded. 

In the last two decades there has been considerable progress in the synthesis of molecular sieve materials. One result of these efforts is cloverite, a large-pore gallophosphate molecular sieve with a 20 T-atom cloverleaf-shaped entrance into a supercage of about 30 A diameter, which has attracted attention not only due to potential novel adsorption and catalytic properties and the uptake of bulky adsorbates, but also as a host for the preparation of semiconductor nanoclusters, as an example for the development of new advanced materials. 

Synthesis of molecular sieves with T sites isomorphously substituted by other elements is frequently accompanied by the formation of more or less oxidic extraframework species as by-products (see Sect. 4.1.2.2). In this section the intended preparation of finely divided oxides or oxide clusters within the voids of the framework will be discussed. 

ORGANIC AND INORGANIC AGENTS IN THE SYNTHESIS OF MOLECULAR SIEVES... 

The first step consists in the synthesis of molecular sieve materials. This field has been widely broadened in the past two decades for synthetic materials since the introduction by R. Barrer of organic compounds such as quaternary amine cations as template molecules. Other presentations in this Advanced Study Institute are dealing with synthesis of molecular sieves. 

A wealth of techniques can be applied at the nascence of a catalyst material. This will be illustrated using two showcases, namely the synthesis of molecular sieve silicalite-1, which possesses one of the most well-known microporous frameworks. 

Fig. 2.19 Synthesis of molecular sieve carbon (MSC) through nanocasting pathway The sacrificial templates include the crystalhne zeolites and MOFs. Reproduced from Ref [97] by permission of John Wiley Sons Ltd...

Cobaltocene cations, Coi y -CsHsjJ, can serve as templates for the synthesis of molecular sieves as metallocenium inclusion compounds [268, 269]. 

Following upon the pioneering work of Freund [42] and Lowe et al. [43], Hamilton et al. [44] reported on a study in which several different powdered silica sources were used in the synthesis of molecular sieve zeoHte NaX. In the two previous works [42,43] the authors had determined that active siHcates were those which had relatively high levels of aluminate impmities. The more recent study sought to correlate active siHcates with those from which an increased number of nuclei formed in the hydrothermal system, that is, the activity was associated with the number of crystals which were formed, which added to the cumulative crystal surface area available to assimilate material from solution. In that study, the batch composition was the same in all experiments, and given by ... 

Gilson J-P (1992) Organic and inorganic agents in the synthesis of molecular sieves. In Derouane EG et al. (eds) Zeohte microporous solids synthesis, structure, and reactivity. Kluwer Academic, Netherlands, p 19... 

---