Sodium form unit cell composition

The cubic unit cell constants, a, of a number of P-A zeolites were determined over a range of phosphorus content (0 to 10 wt % P2O5). The unit cell dimension decreases with increase in phosphorus content (Table IV, Figure 7). This reduction in unit cell constant is consistent with the substitution of phosphorus in the zeolite framework by the mechanism discussed later, and is attributed to the smaller tetrahedral P—O bond distance of 1.54 A, compared to the tetrahedral Si—O bond distance of 1.61 A and A1—O bond distance of 1.75 A. Unit cell compositions for P-A zeolites calculated on the basis of the pseudo cubic unit cell of Type A zeolite, a <—12 A, are included in Table V. Measured densities for the sodium forms and calcium-exchanged forms of zeolite A and zeolite P-A are given in Table VI. 

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. 

Stoichiometric amounts of sodium iodate and zirconium sulfate dissolved in water form a white precipitate immediately. The air-dried product is amorphous, but upon exposing the precipitate to refluxing nitric acid in a Soxhlet extractor, small well-formed crystals of Zr(IOs)4 appear in the bottom of the flask. The iodate ion is bidentate 334) along the I edge of a nearly perfect antiprism. The average Zr-0 distance is 2.206 A. There are two formula units in the unit cell and the space group is P4/w. lodates precipitated from solutions of Cl Zr ratios <2 gave products of variable composition (530). 

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