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Reduction and cluster growth of palladium in zeolite Y containing transition metal ions. X-ray absorption studies

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  • Chemie Und Pharmazie
  • Ddc:540

Abstract

J. Phys. Chem. 1990, 94, 845-853 845 anchored to the air/solution interface. From this result is easily inferred a folding of the alkanediyl chain and its penetration into the inner micelle. The folding can also be examined by the following approach. The partial molar volume v of tetradecane- sulfonate anion in the micellar state is estimated to be 254.4 cm3 mol-l 2o by applying the Stokes’ radius of 1.84 A to the sodium ion. Then, the micellar surface area (S) made only of surfactant ions is given by where the micelles are assumed to be spherical due to relatively small aggregation numbers. On the other hand, the distance (6) between anionic head groups is related with the above surface area in the form s = ( 4 7 ) ’ / 3 ( 3 f i V ) * / 3 (7) s = ( f i / 2 ) , d 2 (8) where the hexagonal packing is assumed as for the anionic groups. (20) Tanaka, M.; Kaneshina, S.; Sin-no, K.; Okajima, T.; Tomida, T. J . Colloid Interface Sci. 1974, 46, 132. From the u and f i values obtained above, the distance d can be evaluated for each counterion. At the same time, the distance between two cationic charges in the counterions is also evaluated from the CPK model. These two distances are plotted against the carbon number of the alkanediyl group of the counterions (Figure 6 ) . From this figure, the distance between the two cationic charges of the counterions becomes longer than that between anionic head groups of micellized surfactant ions above an eight CH2 groups separation of counterions, which also strongly indicates the folding of the alkanediyl chain of the counterions. The above two simplified calculations substantiate the as- sumption made from the cmc change in the previous paper1* that the divalent cationic charges whose separation is more than eight methylene groups become anchored to the micellar surface due to electrostatic attraction by anionic head groups of surfactant ions, while the alkanediyl chain folds and penetrates into a hy- drophobi

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