Oxygen single-phase experiments, reaction

Buffered Solutions. Single phase experiments in 0.5 M acetic acid-0.5 M sodium acetate buffer solutions, with HS07 (0.01 to 0.04 H) in large excess over oxygen, gave approximately a zero order dependence on oxygen. The data actually indicated a somewhat less than zero order initially which gradually became zero order as the reaction approached completion. The complete rate law for these buffered solutions at pH 4.7 appears to be... 

The separation of the two sets of desorption products may indicate that they are from different sites. That is, branching of the selective and nonselec-tive oxidation takes place on adsorption of butene. This can be confirmed if the two sets of products can be varied independently. This is shown by two experiments. The first experiment makes use of the fact that butene and butadiene adsorb on the same sites. Butadiene is first adsorbed onto the catalyst (5). The catalyst is then heated to 210°C, desorbing all of the unreacted butadiene, but leaving on the surface the precursors of the combustion products. Since desorption of the unreacted butadiene does not involve a net chemical reaction, the adsorpton sites involved are not affected. The catalyst is then cooled to 22°C, and cis-2-butene is adsorbed. If selective oxidation and combustion take place on the same site, the adsorbed butene would undergo both reactions. If they take place on separate sites, and butene adsorbs only on the selective oxidation site (because the combustion site is covered by species from butadiene adsorption), the adsorbed butene would form only butadiene. Subsequent desorption yields a profile similar to that for a single adsorption of ds-2-butene (Fig.l, curve b). More importantly, within experimental errors, the amount of butadiene evolved is the same as in a ds-2-butene adsorption experiment, and the amount of C02 evolved is the same as in a butadiene adsorption experiment. Thus, the adsorbed butene forms only butadiene. These results show that under these experimental conditions (i.e., in the absence of gas-phase oxygen), the production of butadiene and carbon dioxide takes place on separate sites. 

The combustion of sprays in a high-temperature furnace is a complex physical and chemical process that involves simultaneous heat, mass and momentum transfer, phase transition, and chemical reactions. The droplet size, composition of the fuel, ambient temperature and pressure, and oxygen concentration are major factors that affect the combustion process. Owing to the complexity of the process, it is very difficult to obtain accurate information on the combustion of the spray. However, the evaporation and combustion of a single droplet of oil have been well studied since it is relative easy to carry out an experiment for the measurement of combustion. Furthermore, it has been theoretically investigated due to its simplicity. 

Detailed studies of the coadsorption of oxygen and carbon monoxide, hysteresis phenomena, and oscillatory reaction of CO oxidation on Pt(l 0 0) and Pd(l 1 0) single crystals, Pt- and Pd-tip surfaces have been carried out with the MB, FEM, TPR, XPS, and HREELS techniques. It has been found that the Pt(l 0 0) nanoplane under self-osciUation conditions passes reversibly from a catalytically inactive state (hex) into ahighly active state (1 x 1). The occurrence of kinetic oscillations over Pd nanosurfaces is associated with periodic formation and depletion of subsurface oxygen (Osub)- Transient kinetic experiments show that CO does not react chemically with subsurface oxygen to form CO2 below 300 K. It has been found that CO reacts with an atomic Oads/Osub state beginning at temperature 150 K. Analysis of Pd- and Pt-tip surfaces with a local resolution of 20 A shows the availability of a sharp boundary between the mobile COads and Oads fronts. The study of CO oxidation on Pt(l 0 0) and Pd(l 1 0) nanosurfaces by FEM has shown that the surface phase transition and oxygen penetration into the subsurface can lead to critical phenomena such as hysteresis, self-oscillations, and chemical waves. 

The chemisorptive state of oxygen significantly exceeds the single-layer saturated adsorption quantity for many metals. This shows that the absorbed oxygen can penetrate into the bulk-phase of catalyst. With isotopic tracer experiments, it can be proved that the lattice oxygen in metal oxide is also involved in the reactions. 

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