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ChemInform Abstract Both Lewis and Bronsted sites are found to be present on the surfaces of V2O5 and MoO3, while TiO2 does not display significant Bronsted acidity. The number of acid sites on Mo/SiO2 and V/SiO2 is greater than that found for MoO3 and V2O5 alone. The number of Lewis sites increases upon reduction by formation of oxygen vacancies. Silica-supported TiO2 exhibits strong Lewis acidity, analogous to unsupported TiO2. Addition of water generates Bronsted acid sites at the expense of Lewis sites. This behavior is observed only for the oxidized forms of silica-supported TiO2, V2O5, and MoO3. A model accounting for the generation of Bronsted acidity is proposed, which employs Pauling's electrostatic bond strength to evaluate the degree of undersaturation for surface oxygens.

There are five carbon atoms in this molecule, so Nc = 5. By use of eq 4, the upper flammability limit is estimated to be 11.4 vol %. Sax (1984) reported an experimental value of 9.0 vol %.

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N u m z u 41 0, Japan Synopsis Thermal analysis in combination with infrared spectroscopy was applied to investigate the states of ethylbenzoate (EB) and TiC1, in the simple type of the MgC1,-supported high-yield catalysts. A further attempt was made to evaluate kinetic parameters in the initial stage of propylene polymerization (i Is) by a stopped flow method. The catalysts employed in the present study were prepared by co-grinding MgC1, and TiCl, . EB complex. Thermal analysis and infrared spectroscopy showed that TiC1, . EB complex decomposes during co-grinding process. It was also indicated that EB, thus produced, has strong interaction with MgCl,. This was consistent with observations made by infrared spectroscopy. It was deduced that EB and TiCl, are supported at separate sites of MgCl, in the co-ground catalyst. Kinetic parameters including rate constants of propagation ( h,) and transfer (k,,), and concentration of polymerization centers ([C*]) were determined. The values of k , and k,, remained almost constant throughout the range of co-grinding time, but [C*] increased with time of co-grinding. No significant changes in the value of k , were observed. Accordingly, the improvement of catalyst activity was attributed to an increase in [C*] rather than k,. These results lead to the conclusion that the complex decomposes during the co-grinding to yield EB and TiC1, which interact only with MgCl,.