Zeolite formation factors

Figure 2. Relative significance of the zeolite formation factors...

In order to reduce the total time of synthesis ( 30 min), it has been reported to employ two stage synthesis processes, an initial microwave heating for around 30 min. followed by the conventional synthesis method [8, 40, 41]. Although, the purity of zeolite has been of much concern, the final yield used to contain unreacted (read residual) fly ash, which can affect the characteristics of synthesized zeolite. In fact, the presence of considerable quantity of unreacted fly ash residue in the final yield can be attributed to the factors, which are being discussed in the next chapter The mechanism of zeolite formation . 

The mere exposure of diphenyl-polyenes (DPP) to medium pore acidic ZSM-5 was found to induce spontaneous ionization with radical cation formation and subsequent charge transfer to stabilize electron-hole pair. Diffuse reflectance UV-visible absorption and EPR spectroscopies provide evidence of the sorption process and point out charge separation with ultra stable electron hole pair formation. The tight fit between DPP and zeolite pore size combined with efficient polarizing effect of proton and aluminium electron trapping sites appear to be the most important factors responsible for the stabilization of charge separated state that hinder efficiently the charge recombination. 

Xiang, Y., Larsen, S.C. and Grassian, V.H. (1999). Photooxidation of 1-alkenes in zeolites a study of the factors that influence product selectivity and formation. J. Am. Chem. Soc. 121, 5063-5072... 

Kerr, G.T. (1955) Chemistry of crystalline aluminosilicates 1. Factors affecting the formation of zeolite A. 

The identification of a specific zeolite species with a particular genesis or environment of formation is very difficult if natural mineral occurrence is used as the sole criteria. Most alkali zeolites are found at one place or another in most low temperature geological situations. Various authors have cited various physical and chemical factors which would control the sequence or particular species of alkali zeolite found in nature. Silica and alkali activities in solution are of great importance in surface and buried deposits (Sheppard and Gude, 1971 Honda and Muffler, 1970 Hay, 1964 Coombs, t al.. 1959 Read and Eisbacher, 1974). 

The zeolite catalysts are very effective in removing volatile organic bromine. However, they are not very effective in removing antimony bromide from the volatile pyrolysis products. Actually, the zeolites cause a dramatic increase of the formation of hydrogen by a factor of 10. In addition, zeolite catalysts were found to reduce the formation of some valuable pyrolysis products, such as styrene and cumene, but other products, such as naphthalene were formed instead (53). 

Analogous mechanistic studies of the formation of zeolite minerals have been reported. Kossowskaya (51), in this volume, considers the genetic associations of sedimentary zeolites and the dominant factors controlling their process of formation. An especially lucid and concise presentation of the mechanism of formation of sedimentary zeolites under low temperature conditions is given by Mariner and Surdam (52). In studies on the formation of zeolites in saline alkaline lakes, they show differential... 

It is known that temperature is a critical factor for the crystallization of zeolites and molecular sieve materials. Since the mesoporous structures can be formed in a wide range of temperature [2], it is essential to investigate a suitable range of temperatures for the formation of integrated MCM-41 structures in fluoride medium. 

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