Propylene activation energies

Campbell reported that propylene adsorbs weakly on gold surfaces and adsorbs moderately on T1O2 (11 0) with a desorption activation energy of 11.3kcal/mol and that propylene adsorbs most strongly at the perimeter of gold islands on Ti02 (11 0) [68]. 

A guide to the manner in which structural theory may be applied to a detailed consideration of the mechanism of a surface-catalyzed reaction is found in papers by Cossee (113), Arlman (114), and Arlman and Cossee (115) concerning the mechanism of the stereoregular heterogeneous catalyzed polymerization of propylene. Particular crystallographic sites are shown to be the active centers at which the reactants combine and ligand field theory is used to demonstrate a plausible relationship between the activation energy for the conversion of adsorbed reactants to the product and the properties of the transition metal complex which constitutes the reaction center. 

The effect of the addition of water and molecular solvents such as propylene carbonate, N-methylformamide, and 1-methylimidazole on the conductivity of [C4Cilm][Br] and [C2Cilm][BF4] was measured at 298 K [211]. The mixture of the IL and the molecular solvent or water showed a maximum on the conductivity/mole fraction IL curves. The maximum for nonaqueous solvents was at the level of approximately 18-30 mScm at low mole fraction of the IL and the maximum for water was at level approximately 92-98 mScm [211]. The conductivity of a mixture of these two ILs depends monotonically on the composition. The temperature dependence of the conductivity obeys the Arrhenius law. Activation energies, determined from the Arrhenius plot, are usually in the range of 10-40 kj mol / The mixtures of two ILs or of an IL with molecular solvents may find practical applications in electrochemical capacitors [212]. 

The activation energy referred to the concentration of the olefin in the liquid phase can be deduced from the one referred to the pressure in the gaseous phase, by adding the solution heat of the propylene in n-heptane. 

With Na+, as a cation, the activation energies for the anionic polymerization of acrolein and propylene sulfide (11) are approximately the same. On the other hand, with Li+, it is impossible to compare the acrolein activation energy with the same monomer or another polar monomer because no result is found in the literature. Moreover, for the acrolein polymerization, (Raj u+) lower than ( > +). 

Pino and Miilhaupt considered four diastereomeric jt complexes formed as a result of the four possible modes of complexation of propylene.328 They suggested that diastereomeric and rotameric equilibria between these jt complexes and/or activation energy for the insertion reaction control the large regioselectivity and enan-tioface discrimination necessary for stereoregular polymerization. 

Fig. 15. The apparent activation energy for the oxidation of propylene over the supported bismuth molybdate catalysts (52). (O) Bi2 Mo3 012/CoMoO., ( )...

The diffusional activation energies, listed in Table III, show a clear correlation with the critical diameters of the sorbite molecules (calculated as the diameter of the smallest cylinder which cap circumscribe the molecule). The data for the olefins are of particular interest since propylene, 1-butene, and frcms-2-butene, which all have the same critical diameter,... 

Table 7.3 shows values of effective rate constants for different temperatures. Table data indicate that the epoxidation rate (7.8) is low compared with the complex formation rate (ki/k2) 102-103). If we plot keS values in Arrhenius coordinates, the numerical value of effective activation energy for propylene epoxidation is determined 8.76kcal/mol corresponding to enzymatic processes (7-15kcal/mol). 

The reported apparent activation energies for disproportionating propylene are lower for the cobalt molybdate-alumina than for tungsten oxide-silica. With co-... 

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