Oxygen excess ratio

In order to clarify the resistivity characteristics of the specimens, we obtained the relationship between an equilibrium oxygen partial pressure and the oxygen excess ratio from both theoretical calculations and measurements using the oxygen sensor. The complete propane oxidation can be described by the following reaction. 

The reaction mechanism involves silylation of a nitro group oxygen followed by deprotonation to give the intermediate silyl nitronate 137, which undergoes 1,3-dipolar cycloaddition to give the product 136 in excellent yields and with diastereomeric excess ratios often exceeding 99 1 (Scheme 15). 

For most polymers, the yield of hydroperoxides is relatively low even in the presence of oxygen excess. The relatively high values were, e.g., obtained during oxidation of atactic polypropylene [79], In the initial phases of oxidation, the yield of hydroperoxide related to 1 mol of oxygen absorbed is 0.6 at 130 °C when passing the maximum concentration it decreases considerably. In isotactic polypropylene, the maximum yield of hydroperoxides attains the value 0.2, only [80]. This may be probably related with a local accumulation of hydroperoxides in domains of defects in the crystalline structure which leads to an increased ratio of participation of hydroperoxide groups in the chain reaction of an oxidation process (induced decomposition of hydroperoxides) and finally to a lower yield of hydroperoxides... 

In all of this work, the samples were prepared by chemical reduction, under conditions where no liquid phase was present and the reaction mixture was completely transformed into a bronze of one or two phases. According to Ingold and de Vries (11), such preparations should lie on the pseudobinary join, W03-NaWOs, whereas bronzes prepared by methods such as electrolytic reduction may contain oxygen in excess of an oxygen-tungsten ratio of 3.0. Chemical analyses for sodium and tungsten at several compositions indicated that our samples have an O/W ratio of 3.0 0.15. Precision lattice constants of those samples which fell in the cubic range (x > 0.40), lay on the same lattice constant-nominal composition plot as reported by Brown and Banks (4). 

We have previously (3,4) characterized in detail a series of dealuminated H-mordenites with Si/Al ratios = 5.9, 7.3, 11.0, and 16.9 through FTIR spectroscopy, 27A1-MAS NMR, XRD, and nitrogen adsorption. We have also found a correlation between the aluminum content of the samples and the catalytic activity for the selective reduction of NO with CH4 in the presence of oxygen excess. Despite the aluminum content, catalysts are partially deactivated on dry stream at temperatures of 650 C or higher. 

The NO reduction with ammonia in tlie presence of oxygen was performed over CeNa-MOR(58) at three NH3 to NO feed ratios, i.e., NH3/NO = 1, 1.3 or 1.6. As shown in Table 2, tlie maximum NO conversion (87 %) observed at equivalent amounts of NH3 and NO was found to improve to a complete conversion using a 30 % excess of ammonia at 300 - 500 °C. Moreover, tliere was no ammonia observed in the product gas at tins excess ratio above 200 °C. In otlier words, there was no ammonia slip even at a 30 % ammonia excess condition above 200 °C. At the NH3/NO ratio of 1.6, NO conversion remained at 100 %, though NH3 conversion was not complete under these conditions. It should be noted tliat at the NH3/NO ratio of 1.6, the converted ammonia (0.63 x572 ppm) at 200 °C is calculated to be 1.26 times more than tlie converted NO amount (0.81 x 357 ppm), and 1.33 times more at 300 °C (Table 2). These results suggest tliat under tlie present reaction conditions, ammonia can be introduced in excess of up to 30 % to obtain complete NO conversion witliout an ammonia slip above 200 °C. 

Usually, a fuel is properly burned with excess air or oxygen to ensure complete combustion and prevent the formation of soot. The excess of air is usually characterized by the air excess ratio defined as ... 

The more homogeneous the fuel/air mixture is, the less air excess would be required to complete the reaction. The gas combustion can be carried out near to the stoichiometric point with just a slight oxygen excess. For each fuel depending on the kind of burner, an optimal 2 value and therefore an optimal fuel/air ratio is recommended. Some optimized data are summarized in Table 1. 

FeO is an oxygen excessive (defect of Fe ions) non-stoichiometrical oxide, usually expressed as Fei xO, and commonly known as wiistite in crystallography. Wiistite (Fei xO) contains 23.1%-25.6% of oxygen, which indicates that it cannot reach the theoretical ratio of Fe O = 1 that is corresponding to 22.3% of oxygen. Wiistite is a non-ferromagnetic substance as same as hematite. 

---