Zeolites /zeolite

Zeolite Zeolite Zeolite Zeolite Zeolite + Pellets Zeolite Zeolite Zeolite Co-electrodeposition Silane-linked... 

Molecular Sieve is a term applied to zeolite. Zeolite exhibits shape selectivity and hydrocarbon absorptions. 

J. Fraissard, T. Ito, 1988 (Xe-129 NMR-study of adsorbed xenon - a new method for studying zeolites and metal-zeolites), Zeolites 8, 350. 

Jacobs, P.A. and Mortier, W.J. (1982) An attempt to rationalize stretching frequencies of lattice hydroxyl groups in hydrogen-zeolites, Zeolites, 2, 226. 

Many experimental and, more recently, simulation methods have been put to use to try to localise the cations in faujasite (figure 1) in different situations hydrated or dehydrated zeolites, zeolites saturated with organic molecules, e.g. benzene, toluene, xylene. The four techniques that are described below have been used in more than 90% of all published works to detect and localise extraframework cations in faujasite type zeolites. 

In recent years, there has been a growing interest in the synthesis and application of nano-scale zeolites. Zeolites with a crystal size smaller than 100 nm are the potential replacement for existing zeolite catalysts and can be used in novel environmentally benign catalytic processes. It is well known that the crystal size of zeolites has a great effect on their catalytic properties. The improved catalytic activity and selectivity as well as lower coke formation and better durability can be obtained over nano-sized zeolite crystals [2]. 

Small Pore Zeolites Zeolite A (LTA) 4.1 A diameter pore, 11.4 A diameter cavity... 

Large Pore Zeolites Zeolite X/Y (FAU) 7.4 A diameter pore,... 

Csicsery, S.M. (1984). Shape-selective catalysis in zeolites. Zeolites 4, 202-213... 

Yu, J. (2007) Synthesis of zeolites, in Introduction to Zeolite Zeolite Molecular Sieves, Studies in Surface Science and Catalysis, vol. 168, Elsevier Science Publishers B V, Amsterdam, p. 52. 

The third factor that makes zeolites particularly suitable for simple aromatic separahon is the subtle difference in adsorptive affinity between the various aromatics onto the zeolite. Zeolites, especially the eight-member ring (e.g., ZSM-5)... 

Blower, C. J., Smith, T. D. The gas-phase decomposition of nitromethane over metal ion-exchanged sodium Y zeolite and sodium X zeolite. Zeolites, 1993, Volume 13, Issue 5, 394-398. 

Zeolite, zeolite group A collective term for a family of aluminosilicate minerals characterized by framework structures that allow easy access and exchange of cations and small molecules (see chapter 2), The name derives from the Greek terms zein, meaning to boil, and lithos, meaning stone. The term is also applied to synthetic materials of comparable composition, crystal structure, and physical properties (see chapter 2). 

Barrer and Mainwaring (20) report the use of metakaolin as the aluminosilicate raw material for reaction with the hydroxides of K and Ba as well as the binary base systems Ba-K and Ba-TMA to form zeolites. Zeolite phases previously synthesized in the analogous hydrous aluminosilicate gel systems were crystallized with KOH, including phillipsite-, chabazite-, K-F-, and L-type structures. The barium system yielded two unidentified zeolite phases (Ba-T and Ba-N) and a species Ba-G,L with a structural resemblance to Linde zeolite L. Ba-G,L was reported previously by Barrer and Marshall (21) as Ba-G. Similar phases were formed in the Ba-K system and in the TMA-Ba system where, in addition, erionite-type phases were formed. The L-type structures are said to represent aluminous analogs of the zeolite L previously reported (22). 

This speculation was not only completely vindicated in the preparation of silica-rich forms of a variety of known zeolites (2, 3) it was found that direct use of organic cations in syntheses promoted unusual structural designs which led to novel zeolites. Zeolite omega (S2) was one such material and was first synthesized by Flanigen and Kellberg (4) These... 

Photochlorination of n-alkanes in solution results in substitution at both primary and secondary carbon atoms [213], When n-alkanes included in the channels of zeolite LZ-105 (structure very much like ZSM-5 with channel diameter 5.5 A) were photochlorinated, selective substitution at the primary carbon atom occurred also multiple chlorination was avoided. The high selectivity can be attributed to the template effect of the zeolite. Zeolite LZ-105 includes n-alkanes into its channels and holds them in such a way that only the primary (terminal) carbons are exposed to the attacking chlorine atom (Figure 34). It is the tight fit of the alkanes in the channels that forbids both access of chlorine atoms to secondary carbon atoms and folding of the alkane chain, which would permit secondary carbons to be exposed to the reagent. 

Zeolite Zeolites are crystalline aluminosilicates, which exhibit high selectivity for ammonia, but can also remove some heavy metals (or add small amounts of calcium to a sample). Effluent samples are passed through a column containing zeolite and then tested for toxicity. 

Figure 3.9 Schematic of the process used by Pinnavaia et al. for the preparation of steam-stable aluminosilicate nanostructures assembled from zeolite seeds, (a) Nanosize zeolites (zeolite seeds) (b) zeolite seeds assembling around the surfactant (CTAB) (c) assembled structure and,...

There is a lot of evidence that the crystallization of zeolites from aluminosilicate gels is a solution-mediated transformation process in which the amorphous phase is a precursor for silicate, aluminate and/or aluminosilicate species needed for the growth of the crystalline phase (1-9). Generally, it is well known that the kinetics of most gel-zeolite and zeolite-zeolite transformations can be expressed mathematically by the simple kinetic equation (1,2, 10-12),... 

Our earlier studies of zeolite-zeolite (10,26) and gel-zeolite (11, 12) transformations have shown that, under the assumption that the crystallization of zeolite is a solution-mediated transformation process (1-9) and that the crystal growth is size-independent (5,6, 12-16), the crystallization (transformation) kinetics can generally be expressed as ... 

---