Wave formation in the lower pool of the Bureya hydroproject

Results are presented for a model study of wave formation in the lower pool of a hydroproject. __________ Translated from Gidrotekhnicheskoe Stroitel’stvo, No. 10, October 2007, pp. 43–47.     

Semiconductor Voltage Regulators-Stabilizers for Distribution Networks

Power Technology and Engineering - The article describes the issues of the operation of semiconductor regulators-stabilizers of alternating voltage for distribution networks (PRSPN). The relevance...     

Influence of rock-forming and catalytic additives on transformation of highly viscous heavy oil

The influence of the rock-forming additives kaolin and alumina in the presence of nickel compounds on the thermal catalytic conversion of heavy oil at a temperature of 360°C in a reducing atmosphere at different pressures in the system has been revealed. The effect of poly-α-olefins as a hydrogen donor has been examined. It has been found that there are predominant degradation reactions of the resinous components, aliphatic substituents in asphaltenes, and branched aliphatic structures accompanied by redistribution of n-alkanes toward homologues with a lower molecular weight, resulting in reduction in the viscosity of heavy oil. Conducting the process in the presence of Al₂O₃, Ni, and poly-α-olefins at a pressure of 8 MPa increases the quantity of light fractions of the oil and facilitates the degradation of asphaltenes. A decrease of pressure in the experiment on the oil with kaolin in a reducing atmosphere leads to a decrease in aromaticity of the final product and an increase in the yield of lube oil hydrocarbon and low-boiling fractions.     

Hydrogenation of aromatic compounds in the presence of dibenzothiophene over bimetallic catalysts containing mesoporous aluminosilicates

The hydrogenation of a mixture of naphthalene, tetralin, and toluene (a solution in n-heptane) in the presence of dibenzothiophene (150 and 400 ppm on a sulfur basis) over Pt-Pd catalysts containing Al-HMS mesoporous aluminosilicates has been studied. The catalyst supports contained 35 wt % Al-HMS and 65 wt % γ-Al₂O₃. The Pt and Pd loadings in the catalysts were 0.2 and 0.8 wt %, respectively. The process was carried out at 200–240°C, a pressure of 30 atm, and a weight hourly space velocity of 1.7 h^?1. It has been found that the catalyst based on Al-HMS with Si/Al = 10 exhibits the highest activity. Thus, in the hydrogenation of a model mixture containing 150 and 400 ppm of sulfur, the conversion of toluene at 240°C was 22.2 and 10.9 wt %, respectively. In the presence of this catalyst, the concentration of aromatic hydrocarbons in the hydrotreated diesel fraction decreased from 28.4 to 6.8 wt %, and the sulfur content decreased from 45 to 5 ppm.     

The role of labile products of styrene epoxide conversion in its oxidation in polar acid medium

Phenylacetaldehyde (PAA) and benzyl alcohol (BAl) are formed in oxygen atmosphere from styrene epoxide in the presence of p- toluenesulfonic acid (TSA) in a solution of 90 vol % tert-butanol with 10 vol % chlorobenzene (BUC). The ratio of the propagation (k ₂ ) to the termination (k ₆) rate constants has been measured to be k ₂/√k ₆ = 8.6 × × 10^?3 (L/(mol s))^1/2 at 343 K by the method of initiated oxidation of PAA in a BUC solution. One of the products of the radical chain PAA oxidation is BA. This reaction leads to BAl accumulation during the conjugated oxidation of PAA with the epoxide in an acid alcohol medium. The contribution of BAl formed to the oxidation is almost unnoticeable.     

An assessment of electrolytic hydrogen production from H2S in Black Sea waters

In the deeper parts of the Black Sea basin, water is anoxic. Hydrogen sulfide (H₂S) occurs naturally, and its concentration is nearly constant, around 9.5 mg/L at 1500 m depth. Its high solubility, and the existing chemical environment facilitate its accumulation and containment in the seawater, and its extraction poses a challenge.Possibility of hydrogen and sulfur production from H₂S contained in the waters of Black Sea is investigated conceptually. A multistage process is considered which involves extraction of seawater, adsorption of H₂S, electrochemical production of hydrogen and polysulfides; fresh water production by desalination of seawater and further hydrogen production from the resulting salty solution through chlorine-alkaline electrolysis. Some consideration is included regarding the economic and environmental aspects of the process.     

Effect of polar solvents on the conversion of styrene epoxide in the presence of <Emphasis Type="Italic">p</Emphasis>-toluenesulfonic acid

The addition of tert-butyl alcohol to a styrene epoxide and catalyst (p-toluenesulfonic acid) solution in acetonitrile accelerates the acid-catalyzed total conversion of epoxide and simultaneous oxygen absorption by this binary system (BS). The introduction of water into the alcohol solution of BS increases the oxidation rate to an even greater extent. Experiments with the indicator m-nitroaniline showed that the addition of alcohol and water decreased the deprotonating ability, i.e., the acidity of the solution. The attempt was made to rationalize the paradoxical situation, at which the decline in acidity is accompanied by enhancement of the acidcatalyzed reaction of the epoxide conversion and oxidation, in terms of the participation of the protonated alcohol in the intermediate complex with epoxide.     

Direct starch conversion into L‐(+)‐lactic acid by a novel amylolytic strain of Lactobacillus paracasei B41

A new amylolytic strain of Lactobacillus paracasei able to convert starch directly into L ‐(+)‐lactic acid (LA) was isolated. The identification of the by 16S rDNA sequencing proved that this strain, B41, is the first amylolytic representative of Lactobacillus casei group. The amylase activity assay revealed that L. paracasei B41 produced extracellular amylolytic enzyme, reaching 62 U/mL in the cell‐free supernatants. The optimal conditions for its action were pH 5.0 and temperature 45°C. The gene amy1 (1779 bp) encoding the putative B41 amylopullulanase was cloned, sequenced, and analyzed. The deduced protein contained a leader peptide of 28 amino acids and a mature peptide of 564 amino acids. Compared to the amylases of closely related species, B41 enzyme had several amino acid substitutions. An inducible control at amy1 expression was demonstrated. The starch fermentation abilities of L. paracasei B41 were studied in batch processes performed with and without pH control. The highest amount of LA from starch was obtained during 48 h fermentation from 40 g/L substrate at pH maintained at 5.0–37.3 g/L. In addition, 93.3% starch conversion into LA and the highest reported productivity for 24 h were achieved – 1.30 g/L/h.     

Spectral Reflectivity of Ceramics of Cubic Zirconium Oxide on the Wavelength of 0.63 μm under Intense Surface Heating above the Melting Point and Subsequent Cooling

The experimental data on the normally hemispherical reflectivity of zirconium oxide ceramics are obtained for the wavelength of 0.63 m in the course of the first cycle of heating by concentrated laser radiation up to temperatures above the melting point and free cooling in ambient air. The obtained data are compared with analogous results of the second and subsequent cycles of heating and cooling. Analysis is made of the effect of the temperature field in the heated layer on the reflectivity and on the effective temperature measured by a pyrometer.