Stoichiometry with oxygen

Butane-Based Fixed-Bed Process Technology. Maleic anhydride is produced by reaction of butane with oxygen using the vanadium phosphoms oxide heterogeneous catalyst discussed earlier. The butane oxidation reaction to produce maleic anhydride is very exothermic. The main reaction by-products are carbon monoxide and carbon dioxide. Stoichiometries and heats of reaction for the three principal reactions are as follows ... 

It should be emphasized that very little is quantitatively known about how the total pressures of plutonium-bearing species vary with oxygen potential, stoichiometry, and temperature in the bivariant region of oxygen-deficient plutonia between the phase limits at very high temperatures. New (though limited) oxygen potential data have been obtained in our laboratory above the fluorite, diphasic, and sesquioxide phases in the Pu-0 system at 1750, 2050, and 2250 K. 

Although the nonmetals do not readily form cations, many of them combine with oxygen to form polyatomic oxoanions. These anions have various stoichiometries, but there are some common patterns. Two second-row elements form oxoanions with three oxygen atoms carbon (four valence electrons) forms carbonate, C03, and nitrogen (five valence electrons) forms nitrate, NO3. In the third row, the most stable oxoanions contain four oxygen atoms Si04 -, P04 -, S04, and CI04. ... 

There is a tendency toward alternation in the copolymerization of ethylene with carbon monoxide. Copolymerizations of carbon monoxide with tetrafluoroethylene, vinyl acetate, vinyl chloride, and acrylonitrile have been reported but with few details [Starkweather, 1987]. The reactions of alkenes with oxygen and quinones are not well defined in terms of the stoichiometry of the products. These reactions are better classified as retardation or inhibition reactions because of the very slow copolymerization rates (Sec. 3-7a). Other copolymerizations include the reaction of alkene monomers with sulfur and nitroso compounds [Green et al., 1967 Miyata and Sawada, 1988]. 

Other researchers attempted improved control of product stoichiometry by wrapping reactant-mixture pellets (Tl2Os, BaO, CaO, and CuO) in gold foil and then sealing them in silica ampoules that had been flushed with oxygen (8)(51). Multiphase samples, however, were still obtained. Nominal starting metal compositions of 1 1 3 3 and 2 2 2 3 (Tl Ba Ca Cu) resulted in the largest amounts of 2223 and 2212 phases, respectively the samples... 

Figure 16 (a) Location of the x2 - y2 (planes) and z2 - y2 (chains) bands in the 1-2-3 superconductor showing plane-chain electron transfer and the removal of the half-filled x2 - y2 band, (b) Variation in Tc with oxygen atom stoichiometry showing the dramatic plunge at around S = 0.6. (c) Location of the x2 - y2 (planes) and z2 - y2 (chains) bands in the 1-2-3 system for S > 0.6 showing how plane-chain electron transfer is switched off and the half-filled x2 -y2 band is generated. 

Oxides are widely exploited as catalysts for the selective oxidation of hydrocarbons. They provide lattice oxygen in selective oxidation reactions and exchange it with oxygen gas (e.g. from air in the reactant stream). The periodic lattice oxygen loss for the hydrocarbon oxidation occurs because of reducing gases, despite the presence of gas phase oxygen in the reactant stream. This results in the formation of anion vacancies, local non-stoichiometry and defect structures as discussed in chapter 1. 

The reaction of ammonia with oxygen over V-based catalysts produces mainly nitrogen, according to the stoichiometry of R5 in Table V. Analogously to the case of the ammonia adsorption-desorption, specific runs were carried out in order to extract the intrinsic kinetics of ammonia oxidation and at the same time to validate the previously fitted kinetics of the ammonia adsorption-desorption process. 

The stoichiometry of the partial combustion of methane with oxygen can be expressed as the sum of four reactions ... 

A similar relationship can be observed with promoted M0S2. Each family of catalysts has its own linear correlation, which cannot be compared to each other directly because of the corrosivity problem. More recently, low-temperature oxygen chemisorption has been claimed to be more reliable, but it also lacks a well-determined stoichiometry (52). Oxygen chemisorption has also been applied to tungsten and rhenium sulfides, as well as promoted molybdenum and tungsten sulfides. In the isotropic class, it has been applied only to ruthenium sulfide, in which case it gives approximately the same result as a BET measurement due to the isotropic nature of this sulfide (41). 

The situation is different in the case of ammonia oxidation. Both on platinum (156) and nonplatinum (157) catalysts under the conditions of a commercial process, the reaction occurs in the external diffusion region. Diffusion of ammonia rather than of oxygen is determining the rate since the reaction is conducted with oxygen in excess with respect to stoichiometry, as given by (397). Concentration of ammonia at the surface of the catalyst is so small as compared to its concentration in the gas flow that the difference of concentrations that determines the rate of diffusion virtually coincides with the ammonia content in the flow. 

Reversible oxygen binding has also been examined using poly(ethyleneimine)-cobalt complexes in aqueous solution. Cobalt(II) complexes of linear and branched poly(ethyleneimine) in aqueous solution are able to form with oxygen a p-peroxo adduct as is evidenced from stoichiometry and spectral properties 107). 

Activation in vacuo at high temperature (needed to eliminate most of the hydroxyl groups) is usually accompanied by a loss of oxygen and of stoichiometry (with the accompanying optical effects preventing spectroscopic observations). 

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