Silicon-aluminum ratio various

Table II. Elemental Atomic Ratios for Copper/Aluminum Catalyst Following Various Treatments as Obtained Using Silicon Ka X-Radiation...

The soil cover of the forest and thin-forest zone of Alaska consists of various sub-types of Gleysols, which are generally similar to analogous soils of North Siberia. Kaolinite and motmorillonite and also chloritized monmorillonite are present in the most intensely gleyed horizons. Lepidocrocite (monohydrate of iron oxide) and a large quantity of amorphous hydrated oxides of silicon and aluminum are found in almost all soils. The ratio of silicon to aluminum in the clay fraction is low, in certain places less than 1.0. 

Oxidation of Alkoxides in Air Vapors of aluminum iec-butoxide and silicon ethoxide (premixed or sequentially delivered) were oxidized in air at 700-1400°C for various times (64-170ms) and different. VFOj/SiO, ratio (mass%). 

Silicon atoms in the zeoHte framework are tetrahedrally coordinated (Q ), resulting in five different silicon environments denoted as Si(nAl) units, where n corresponds to the number of aluminum atoms in the second coordination sphere. Each type of Si( Al) unit ( =0,1,2,3 or 4) yields Si MAS NMR signals in a well-defined range of chemical shifts [1,56-58]. These ranges are summarized for the various siHcon units in Fig. 6. The Si MAS NMR spectra of zeolites consisting of sihcon atoms on crystallographically equivalent T-sites, e.g., zeolite X and Y, are only a function of framework composition (Fig. 7). Therefore, the framework s/ Ai ratio of these materials may be calculated directly from the Si MAS NMR intensities using the formula ... 

The structure of zeolites consists of a three-dimensional framework of Si04 or AIO4 tetrahedra, each of which contains a silicon or aluminum atom in the center. The oxygen atoms are shared between adjoining tetrahedra, which can be present in various ratios and arranged in a variety of ways. The framework thus obtained contains pores, channels, and cages, or interconnected voids. 

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