J. Phys. Chem. 1990, 94, 1477-1482 micellar surface potential decreases, whereas the ion-exchange decreases with surfactant and salt equilibrium parameter, PHBr, concentration. We note that Ks was obtained experimentally by ultrafiltration and at low surfactant concentration, and in the absence of salt, K s S 0 = 122 M-I. This value is equivalent to = 8500 in the electrostatic treatment. According to the electrostatic treatment, the second-order rate constant for the reaction in the micellar phase is more than twice the second-order rate constant in water. This means that the micelles produce an authentic catalytic effect on this reaction, while the second-order rate constant for the reaction in the micellar phase, according to the pseudophase ion-exchange equilibrium model, is smaller than the second-order rate constant in water. We conclude that the Poisson-Boltzmann ion distribution
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around spherical micelles fits experimental kinetic results assuming a specific bromide ion interaction with the micelle. It improves the pseudophase ion-exchange kinetic model as it predicts that cationic substrate to cationic micelle binding increases with surfactant and ion concentration in solution, according to the experimental evidence, and only two parameters are needed to explain kinetic data: k,, the rate constant in the micellar phase, and Pos, related to the Ar value. According to this treatment, there is a big variation in the ion-exchange equilibrium parameter although we are aware that a constant value of this parameter explains kinetic data at low salt concentration according to the pseudophase ion-exchange model. At this moment, we continue working trying to improve this electrostatic treatment although until now we could not find a better one.
Morphology of Molybdena Supported on Various Oxides and Its Activity for Methanol Oxidation Yoshihito Matsuoka, Miki Niwa,* and Yuichi Murakami Department of Synthetic Chemistry, Faculty of Engineering, Nagoya University, Furo-cho, Chikusa- ku. Nagoya 464-01, Japan (Received: December 5, 1988; In Final Form: August 16, 1989)
This paper describes a method of benzaldehyde-ammonia titration (BAT) that can distinguish surfaces of supports and loaded oxides. Such a method has been found to be effective in examining the morphology of molybdena when held on a variety of supports; the results achieved are corroborated by spectroscopic and electron microscopic studies. A molybdena monolayer of tetrahedral or octahedral coordination was loaded at a surface concentration of
