Solid-state reaction, naming system

A CVD reaction can occur in one of two basic systems the closed reactor or the open reactor (also known as close or open tube). The closed-reactor system, also known as chemical transport, was the first typetobeusedforthe purification of metals. It is a hybrid process which combines vapor-phase transfer with solid-state diffusion. As the name implies, the chemicals are loaded in a container which is then tightly closed. A temperature differential is then applied which provides the driving force for the reaction. 

The utility of thallium(III) salts as oxidants for nonaromatic unsaturated systems is a consequence of the thermal and solvolytic instability of mono-alkylthallium(III) compounds, which in turn is apparently dependent on two major factors, namely, the nature of the associated anion and the structure of the alkyl group. Compounds in which the anion is a good bidentate ligand are moderately stable, for example, alkylthallium dicar-boxylates 74, 75) or bis dithiocarbamates (76). Alkylthallium dihalides, on the other hand, are extremely unstable and generally decompose instantly. Methylthallium diacetate, for example, can readily be prepared by the exchange reaction shown in Eq. (11) it is reasonably stable in the solid state, but decomposes slowly in solution and rapidly on being heated [Eq. (23)]. Treatment with chloride ion results in the immediate formation of methyl chloride and thallium(I) chloride [Eq. (24)] (55). These facts can be accommodated on the basis that the dicarboxylates are dimeric while the... 

Sakamoto et al. also demonstrated an absolute oxetane synthesis in the solid-state photolysis of Y-( ,(3-unsaturatcd carbonyl)benzoylformamides 43. [28] The X-ray analysis of Y-isopropyl substituted imide 43a revealed that the crystal system was monoclinic and the space group P2. Crystals of 43a were powdered and photolyzed at 0°C. The imide undergoes the [2+2] cycloaddition to afford the bicyclic oxetane 44a, which is a mixture of diastereomers, namely, syn- and anh-isomers at the C-7 position. In this reaction optically active. syn-oxctanc 44a with 37% ee (84% chemical yield) and racemic anti-44a were obtained. The solid-state photoreaction proceeded even at -78°C, and optically active syn-44n which showed ee value as high as >95% ee, (conv 100%, chemical yield 89%) was formed in a higher diastereomeric ratio (syn/anti = 6.5). Under identical conditions A-bcnzyl substituted 43b was irradiated in the solid state. 

Earlier work by Matsuura et al. reported that there was a difference in the photochemical behaviour of santonin dependent on whether the reactions were carried out in the liquid or solid phase. - More recent work has demonstrated that the dienones (273) and (274) do not exhibit this difference in behaviour. Irradiation of these compounds yields the same products (275) and (276) respectively whether the reactions are in solution or in the crystal. The authors - suggest that this similarity in behaviour is due to loose crystal lattice structures. The solid state irradiation of the dienone (277) results in the formation of the normal products for such systems, namely the corresponding photoketone, photophenol, and lumiketone. The ratio of these three products was sensitive to temperature. In solution no temperature dependence was detected. Interestingly when the dienone is irradiated in the solid with wavelengths > 400 nm a quantitative yield of the lumiketone is obtained. ... 

According to the complexes investigated so far, the distances between the atoms directly involved in abstraction, namely O etone td Hsuroid between the atoms to be bonded, namely C gtone steroid atoms, range from 2.9—3.9 A and from 3.7—4.2 A, respectively. In these examples the angle between the C—H bond and the plane of the carbonyl system >C =0 varies from approximately 55° to 90° (Table 4). Thus we are able to predict, with some certainty, the available steroid sites for reaction. According to Scheffer and Dzakpasu, solid-state intramolecular... 

Iron-zeolite catalysts present an important type of materials with broad application for selective oxidations (i.e. benzene hydroxylation) and environmentally important processes, like SCR reduction of NOx or N2O decomposition. In the case of SCR reaction they could provide a convenient substitution of the vanadia-based system using environmentally problematic ammonia, by more convenient paraffin as a reducing agent. Unfortunately, the efficiency in utilization of paraffin is inferior in comparison to ammonia, namely due to paraffin nonselective oxidation by oxygen catalyzed by unspecified iron-oxide type species typically present in the iron-zeolite catalysts. The mostly used preparation processes include impregnation from water solutions, ion exchange procedures, both in water solution or solid state, as well as gas phase CVD. 

Rather than survey all of the possible modifications that can be made to an alumina surface, we will focus on a subset involved in two different types of surface-catalyzed chemical reactions, namely, the partial oxidation of ethylene to ethylene oxide (EO) and hydrodesulfurization (HDS) processes. Both of these catalytic systems have functional points in common, in that alumina serves as a support (a-alumina for the EO process and 7-alumina for the HDS process) and alkali-metal salts serve as promoters for both reactions. To illustrate this commonality, this section will be divided into three parts (1) the adsorption of alkali-metal salts to 7-alumina, as reflected in the Rb and Cs solid-state NMR spectroscopy of these systems (2) the absorption of ethylene to silver supported on aluminas in the presence and absence of cesium salts, as followed by C NMR spectroscopy, and (3) the solid-state Mo NMR of fresh and reduced/ sulfided molybdena-alumina catalysts. 

While the acid strength of HPAs is high, they have a limitation in their use in catalysis, and this is due to their low surface area in the solid state (SlOm g- ), which corresponds to the external surface area of the crystal. When the reactants have a polar character, however, HPAs can take up polar molecules in amounts that correspond to more than 100 surface layer, and in this case their catalytic behaviour has been called bulk type catalysis [31"). Therefore, in the case of catalytic reactions involving polar molecules, they occur not only at the surface but also in the bulk solid of certain HPAs. The practical effect is that the catalytic system behaves like a highly concentrated solution, and this explains why these solids have been named pseudoliquids [31 j. Under the pseudoliquid conditions all acid sites are accessible to reactants, and the benefits of the system have been used commercially for reactions such as the hydration of propylene and n-butenc, separation of isobutene, and polymerization of tetrahydrofuran 20, 31". ... 

The natural state of the constituents listed above may be gas, liquid, or solid. This leads to an important issue, namely, the preparation procedure for the homogeneous catalytic system and its impact on the initial state of the system. For batch and semibatch reactions, preparation is normally carried out in a stepwise manner, by sequential addition of all components. Two types of systems will be defined and used in further discussion. 

The development of the kinetic theory made it possible to obtain a solution of the problem on the self-consistent description in time and in an equilibrium state of the distributions of interacting species between the sites of homogeneous and inhomogeneous lattices. This enables one to solve a large number of matters in the practical description of processes at a gas-solid interface. The studied examples of simple processes, namely, adsorption, absorption, the diffusion of particles, and surface reactions, point to the fundamental role of the cooperative effects due to the interaction between the components of the reaction system in the kinetics of these processes. 

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