Hydrogen form unit cell composition

Materials. The NaY faujasite was supplied by Linde Co (SK UO Sieves). A conventional exchange with NH Cl provides a NH Y sample (unit cell composition (NH J gNa-jQAl5531-135033 ). Heating this sample for 15h in oxygen and 3h in vacuo (l0 5torr) at 350°C leads to the hydrogen form HY. 

In a sodium mordenite of unit cell composition Nag[Al8Si4o096]24 H2O the ideal ou assed hydrogen form should have 1.61 x 10 Brcinsted acid sites per gram of dry zeolite. The maximum reaction rate correspcmds with 1.7 xlO molecules of water added to the zeolite. This quantity of water is just suffident to convert the hydrogen mordenite to hydronium mordenite. However, for general validity of the water co-catalysis mechanism it is necessary to prove that maximum reaction rates should appear in other hydrogen zeolite catalysts when the water added is equal to the number of Bronsted add sites. 

In the face-centred cubic structure tirere are four atoms per unit cell, 8x1/8 cube corners and 6x1/2 face centres. There are also four octahedral holes, one body centre and 12 x 1 /4 on each cube edge. When all of the holes are filled the overall composition is thus 1 1, metal to interstitial. In the same metal structure there are eight cube corners where tetrahedral sites occur at the 1/4, 1/4, 1/4 positions. When these are all filled there is a 1 2 metal to interstititial ratio. The transition metals can therefore form monocarbides, niU ides and oxides with the octahedrally coordinated interstitial atoms, and dihydrides with the tetrahedral coordination of the hydrogen atoms. 

The key conclusion that is relevant here is that the native celluloses are composites of more than one crystaline form, but that the difference between the two forms lies not in the molecular conformation but in the hydrogen bonding patterns. Thus, it is possible that the native celluloses have unit cells with very similar atomic coordinates for the heavy atoms, but with different coordinates for the hydrogens. The similarities in the heavy atom locations could account for the many comonalities in the diffraction patterns, while the differences in the coordinates of the hydrogen atoms could be responsible for the differences between the patterns. This would account for the greater incidence of nonallowed reflections in the electron diffraction patterns. 

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