Activation parameters ethylene oxide reaction

Compensation effects have been reported for the oxidation of ethylene on Pd-Ru and on Pd-Ag alloys (207, 254, 255) discussion of the activity patterns for these catalysts includes consideration of the influence of hydrogen dissolved in the metal on the occupancy of energy bands. Arrhenius parameters reported (208) for ethylene oxidation on Pd-Au alloys were an appreciable distance from the line calculated for oxidation reactions on palladium and platinum metals (Table III, H). Oxidation of carbon monoxide on Pd-Au alloys also exhibits a compensation effect (256). 

Fig. 9. Influence of chlorine coverage on the kinetic parameters for selective ethylene oxidation over a Ag(llO) surface. Parameters for both the production of ethylene epoxide (EtO, circles) and the undesired side reaction to full combustion (C02, squares) are presented. Steady-state reaction orders in P02 and Pei and activation energies a versus chlorine coverage near 563 K, Pb = 20 torr, and P02 = 150 torr. From Ref. 118.

The first mode of the high resolution C-NMR of adsorbed molecules was recently reviewed Q-3) and the NMR parameters were thoroughly discussed. In this work we emphasize the study of the state of adsorbed molecules, their mobility on the surface, the identification of the surface active sites in presence of adsorbed molecules and finally the study of catalytic transformations. As an illustration we report the study of 1- and 2-butene molecules adsorbed on zeolites and on mixed tin-antimony oxides (4>3). Another application of this technique consists in the in-situ identification of products when a complex reaction such as the conversion of methanol, of ethanol (6 7) or of ethylene (8) is run on a highly acidic and shape-selective zeolite. When the conversion of methanol-ethylene mixtures (9) is considered, isotopic labeling proves to be a powerful technique to discriminate between the possible reaction pathways of ethylene. 

Fig. 2 Selected geometric parameters (A) of the optimized structures of key species for oxidative coupling via the most feasible pathway for cis-riVcis-ri -butadiene coupling along la 4, commencing from the [Ni (ri -butadiene)2] precursor la. Activation and reaction free energies (kcal moT ) are given relative to the [Ni°(ri -traMS-butadiene)2(ethylene)] isomer of lb...

CF2 CF2 < CF2 CF-CH CHMe < CF2 CF CH CH2 < CF2 CF-CF CF2 Approximate Arrhenius parameters have been obtained for the reaction of oxygen atoms ( F), from the mercury-sensitized decomposition of nitrous oxide, with the fluoroethylenes at two temperatures (25 and 150 °C) using the olefin CH2 C(CFs)Me as reference compound. All the fluoroethylenes appear less reactive than ethylene again with the exception of tetrafluoroethylene, reactivity being least for cis-l,2-di-fluoroethylene. The differences appear largely due to differences in activation energy, and the anomalous reactivity of tetrafluoroethylene is noteworthy. 

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