Modernization of Air Supply Unit for Oxidation Towers Used in Bitumen Production

Chemical and Petroleum Engineering - The hydrodynamics of oxidation towers used for bitumen production were studied using a model tower having transparent walls. Experiments were carried out in two...     

The Construction of Differential Inclusions with Prescribed Attainable Sets

For given ε > 0 and a given continuous set-valued mapping t → Z(t), t ∈ [t ₀, θ], where Z(t) ⊂ ℝ ⁿ is a compact and convex set for every t ∈ [t ₀, θ], a differential inclusion is constructed such that the Hausdorff distance between the attainable set of the constructed differential inclusion at the instant of time t and Z(t) is less than ε for every t ∈ [t ₀, θ]. The right-hand side of the defined differential inclusion is affine with respect to the phase state vector and satisfies certain conditions which guarantee the existence and extendability of solutions. The solution of the problem is based on the existence of convex extensions of the affine-type convex compact set-valued mappings.      

Stimulation of negative magnetoresistance by an electric field and light in silicon doped with boron and manganese

It is experimentally ascertained that light stimulates the negative magnetoresistance observed in a high electric field in silicon doped with boron and manganese. The optimum conditions (the electric field, temperature, illumination, and resistivity of the material) for observation of the largest magnitude of negative magnetoresistance in (Si:B):Mn are determined. The dependence of the negative magnetoresistance on the concentration of compensating impurity is established.     

Temperature-dependent I-V characteristics of organic-inorganic heterojunction diodes

In this paper, heterojunctions were fabricated by employing p-type Si and thin films of poly-N-epoxipropylcarbazole (PEPC) doped with tetracyanoquinodimethane (TCNQ). The PEPC films were grown on Si wafers at room temperature but with different gravity (g) conditions:-1, 123, 277, and 1107g. Current-voltage (I-V) characteristics of the grown hybrid structures were evaluated as a function temperature (T) ranging from 20/spl deg/C to 60/spl deg/C. It was found that all samples are p-p isotype heterojunctions and the junctions fabricated at a high value of g, i.e., at 277 and 1107 g, showed reversible rectifying properties as a function of device temperature. Whereas the behavior of devices fabricated at 123 and 1 g were rectifying at room temperature, but became almost nonconductive after treating the samples at 60/spl deg/C. Rectification ratio, threshold voltage, reverse saturation current, and junction resistance of the fabricated junctions were evaluated at different temperatures. At T=60/spl deg/C, the devices grown at 1107 g exhibited rectification ratio less than unity which may be attributed to the switching of the depletion at the interface. This has been explained by assuming the generation of carriers are at elevated temperatures in the organic film, and their subsequent emission from the organic to the inorganic side of the heterojunction.     

Mathematical Modeling of Ion Transport and Water Dissociation at the Ion-Exchange Membrane/Solution Interface in Intense Current Regimes

At current densities exceeding the limiting current density, H⁺ and OH^? ions are generated at the interface of the ion-exchange membrane with a depleted solution as a result of the dissociation of water molecules. At present, it is generally accepted that water splitting occurs in a thin (a few nanometers) layer inside the membrane, this reaction being catalytic in nature. The mathematical model of ion transport in the diffusion layer near the membrane surface has been constructed and numerically studied under conditions when dissociation and recombination processes involving water molecules and H⁺ and OH^? ions occur simultaneously. It has been shown that in overlimiting current regimes under very high voltages, intense noncatalytic dissociation of water molecules in the extended space charge region of the depleted solution can occur irrespective of the catalytic splitting of water. Since this region has macroscopic dimensions, the rate of noncatalytic water dissociation is comparable with the rate of the corresponding catalytic process. The obtained results significantly supplement modern concepts of the mechanism of generation of H⁺ and OH^? ions in membrane systems, showing that this process can proceed not only in accordance with the conventional mechanism with the catalytic participation of functional groups and/or other compounds, but also via the noncatalytic mechanism that has not been taken into account to the present.     

Heavy Oil Hydroconversion in the Presence of Ultrafine Catalyst

The hydroconversion of heavy oil in the presence of an in situ synthesized catalyst (MoS₂) is studied. It is shown that ultrafine aggregates of amorphous components and crystalline particles of molybdenum sulfide with a particle diameter of 20–70 nm are formed from catalyst precursor (ammonium paramolydbate) emulsion under hydroconversion conditions in a medium of heavy oil. The kinetic characteristics of the hydroconversion of heavy oil and separate groups of its components—paraffin-naphthene hydrocarbons, aromatic hydrocarbons, resins, and asphaltenes—are determined.     

Cumene hydroperoxide decomposition in the presence of organic zinc salts

Cumene hydroperoxide degradation in chlorobenzene in the presence of zinc naphthenate was studied. It was found and kinetically corroborated that the degradation is preceded by the formation of an intermediate complex of the hydroperoxide with the catalyst monomeric form. The kinetic and thermodynamic parameters of the complex are close to those recently found for zinc 2-ethylhexanoate. A procedure for the calculation of the concentration of the catalyst monomeric form from kinetic data is proposed.     

Hydroalkoxycarbonylation of olefins in the presence of palladium phosphine complexes: High activity and regioselectivity

Several types of catalyst systems were examined in the olefin hydroalkoxycarbonylation reaction. The systems contained Pd(PPh₃)₄, PdCl₂(PPh₃)₂, or some other palladium compounds as a principal component. The second component (promoter) was p-toluenesulfonic acid or diphenyl(m-sulfophenyl)phosphine, which combines both the ligand and promoter functions. An important feature of these systems is their high activity in the hydroalkoxycarbonylation of ethylene and a high regioselectivity (83–100%) in the hydroalkoxycarbonylation of α-olefins with respect to linear products. Thus, it was unnecessary to introduce additional stabilizing ligands to augment the catalyst and promoter. The esters obtained can find application in the pharmaceutical industry and perfumery, as well as in other industries.     

On the charge-transport mechanisms in Cr-<Emphasis Type="Italic">n</Emphasis>-InP and Mo-<Emphasis Type="Italic">n</Emphasis>-InP diode structures

Electrical characteristics of Cr-n-InP and Mo-n-InP diode structures were investigated, and the charge-transport mechanism was estimated. It was established that this is either a thermionic or generation-recombination current that dominates in the Cr-n-InP structures, depending on temperature. In Mo-n-InP structures, the double injection of charge carriers dominates in the drift transport.