Solid state oxide phases

Oxidation of dihydroquinacridone to quinacridone may be achieved, for instance, with the sodium salt of m-nitrobenzene sulfonic acid in aqueous ethanol in the presence of sodium hydroxide solution [7]. A distinction is made between heterogeneous and homogeneous oxidation. The reaction is referred to as a solid state oxidation if the solvent contains approximately 2% sodium hydroxide solution. A content of approximately 30% sodium hydroxide solution relative to the solvent mixture, on the other hand, converts the reaction into a so-called solution oxidation . The type of ring closure defines the crystal modification of the resulting dihydroquinacridone, while the oxidation technique defines the crystal phase of the quinacridone pigment. 

Solid state oxidation, both of the a- and the 3-phase [8] of dihydroquinacridone, affords crude a-quinacridone. Subsequent milling with salt in the presence of dimethylformamide produces the 7-modification, while the 3-form evolves in the presence of xylene. Solution oxidation of dihydroquinacridone, possibly performed as air oxidation in the presence of 2-chloroanthraquinone [9], forms crude 3-quinacridone. Milling with xylene likewise affords 3-quinacridone pigment (see tables of chemical structures on p. 613). 

To illustrate the capabilities of the aerosol process for the synthesis of solid state oxidation catalysts not normally obtained from classical synthesis, the preparation of a series of P-V-0 catalysts was examined. The original objective was to determine whether the synthesis of the reported (4) active phase, P-(VO)2P207, of the catalyst responsible for the selective oxidation of butane to maleic anhydride could be synthesized by the aerosol technique. 

Hochstrasser and Porter4 reported on Primary Processes in Photo-Oxidation. A short review was given on direct photooxygenation reactions in solution as well as in the solid state. Gas-phase reactions in the presence of oxygen were also discussed. 

This response can be rationalized by assuming that two different electrocatalytic pathways, where H2Q acts as solution-phase catalyst on solid-state oxidation of NADH to NAD+, are operative. First, for NADH MCM, a reaction/regeneration mechanism as described by Equations (3.15) and (3.16) operates, the catalytic process being initiated by the electrochemical oxidation of hydroquinone to quinone, Q ... 

While much of the surveyed research exhibits promising vapor-phase sensing performance, many of the technologies remain experimental and bound to a laboratory setting. Most of the commercial gas sensors available today utilize older, more mature technologies such as electrochemical cells, catalytic beads, photoionization detectors (PID), SAW, metal oxide semiconductors (MOS), and QCM. The dearth of viable organic solid-state vapor-phase chemosensors indicates that there is much work still to be done (in terms of material stability, selectivity, etc.) before commercialization becomes commonplace for organic sensors. 

It was previously pointed out (cf. Section 2.4.2) that the enthalpy demand of combustion is deduced from the heat of oxidation proceeding either in the flame source or in the solid phase. The authors concerned are not in general agreement, but it can be established that these reactions take place in the vicinity of the burning surface of the solid phase. According to the analysis of the gas phase, the primary combustible decomposition products (such as hydrocarbons) are consumed within a few millimetres from the surface. Beyond this zone, only combustion end-products (H2O, CO, CO2, etc.) are detected (Figs 2.14 and 2.15). On the other hand, as supposed by Stuetz, the solid-state oxidation proceeds below the surface at a distance not greater than 1.6 mm (Fig. 2.12). 

This section considers a number of extremely important structure types in which A1 combines with one or more other metals to form a mixed oxide phase. The most significant of these from both a theoretical and an industrial viewpoint are spinel (MgAl204) and related compounds, Na- -alumina (NaAlnOi ) and related phases, and tricalcium aluminate (Ca3Al20g) which is a major constituent of Portland cement. Each of these compounds raises points of fundamental importance in solid-state chemistry and each possesses properties of crucial significance to... 

The application of ly transition metal carbides as effective substitutes for the more expensive noble metals in a variety of reactions has hem demonstrated in several studies [ 1 -2]. Conventional pr aration route via high temperature (>1200K) oxide carburization using methane is, however, poorly understood. This study deals with the synthesis of supported tungsten carbide nanoparticles via the relatively low-tempoatine propane carburization of the precursor metal sulphide, hi order to optimize the carbide catalyst propertira at the molecular level, we have undertaken a detailed examination of hotii solid-state carburization conditions and gas phase kinetics so as to understand the connectivity between plmse kinetic parametera and catalytically-important intrinsic attributes of the nanoparticle catalyst system. 

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