Formation of active sites in titanium-containing zeolites with MFI structure in propylene epoxidation with hydrogen peroxide

Propylene epoxidation with hydrogen peroxide on titanosilicates with different Si/Ti ratios and various states of titanium in the catalysts, prepared by hydrothermal crystallization according to two different procedures, has been investigated. It has been demonstrated that a change in the pH of the crystallizing gel leads to a change in the sequence of titanium insertion in the zeolite structure at a hydrothermal synthesis temperature of 170°C. It was shown that titanium incorporated in the zeolite framework in the tetrahedral positions is an active site in the epoxidation reaction, whereas titanium in the form of titanium dioxide leads to unproductive degradation of hydrogen peroxide.     

Production of isobutylene from acetone over micro–mesoporous catalysts

The production of isobutylene from acetone over micro–mesoporous catalysts with different mesopore contents, which have been prepared using hydrothermal recrystallization of mordenite (MOR) zeolite modified with cesium acetate by incipient wetness impregnation, has been studied. It has been shown that cesium is inserted into the cation positions during the modification, at the same time the number of Brønsted acid sites in the samples decreased. It has been found that an increase in the content of mesopores in the catalyst leads to an increase in the initial rates of acetone conversion and isobutylene formation as a result of removing diffusion limitations. Brønsted acid sites have been shown to be preferable for the selective production of isobutylene from acetone. Micro–mesoporous materials operate more stably as compared to microporous materials.     

Sorption of Methylene Blue on Polystyrene/Bentonite Film Composites

The method of mechanochemical dispersion of bentonite in a polystyrene solution was used to modify the polymer and obtain film materials with improved sorption characteristics with respect to the methylene blue (MB) thiazine dye. It is found that the kinetics of the dye sorption are described by the pseudo-first-order equation. The sorption equilibrium is described by the Langmuir isotherm. The values of the limiting sorption capacity and specific surface area of the composite are determined. It is shown that the sorption efficiency of the dye on the PS/bentonite composite increases tenfold as compared with the non-modified sorbent; the extraction rate increases from 10 to 90%. The method of IR spectroscopy is used to show that MB sorption on polystyrene and the PS/bentonite composite is accompanied by electrostatic and donor–acceptor interactions of the reaction sites of MB with the hydroxyl–containing groups of the composite.     

Electron Paramagnetic Resonance of Tb3+ Ions in YBa2Cu3O6

The first observation of electron paramagnetic resonance (EPR) of Tb³⁺ doped into YBa₂Cu₃O₆ is reported. EPR is used to determine the local symmetry of the rare-earth ion and to study the effect of suppression of high-T _c superconductivity by doping. The distance between the lowest singlets of Tb³⁺ ion 7.1 GHz 0.24 cm^–1 and g-factor g 17.9 have been estimated from measurements. Both these parameters are in a good agreement with the corresponding calculated values. No evidence of Tb⁴⁺ ions was found.     

Corrosion of Heating Surfaces of Power Station Boiler Equipment Made of Steel 12X18H10T

The long-term operation of thermal power equipment made of 12X18H10T steel at a temperature of 550°C and higher changes its performance due to the changed composition of inside surfaces and bodies of tubes. To avoid deterioration of service characteristics during the operation, the thermal equipment is recommended to make of low-carbon chrome-nickel stainless steels or niobium-stabilized steels. Preservation of the equipment by octadecylamine should be carried out only at a working temperature below its thermodestruction temperature.     

New calcium-containing product for complex treatment of osteoporosis

The article presents results of clinical tests of calcium-containing product--dry breakfast "Bodrost"--having in its composition a mineral part of bones of slaughter animals, on patients with menopausal and senil forms of osteoporosis. A chemical composition of the developed product is presented. Results of biochemical tests of blood and urine as well as densitometry of bones of skeleton of patients at the age from 50 to 80 years old are presented. It is established that dry breakfast "Bodrost" can be recommended for complex treatment of osteoporosis.     

Progress in the technology for the production of automobile sheet

Studies that are focused on developing qualitatively new steels for automobile sheet and technologies for making these materials are becoming more and more important. Such studies can be properly carried out only on the basis of extensive fundamental and applied research into the processes and phenomena which take place in the production and subsequent use of automobile sheet. Theoretical principles and applied research findings obtained by specialists at the I. P. Bardin Central Research Institute of Ferrous Metallurgy have allowed several Russian metallurgical plants to use oxygen converters for the mass production of high-quality automobile sheet that is competitive in the international market. __________ Translated from Metallurg, No. 5, pp. 51–54, May, 2007.     

Condensation on curvilinear fins (effect of groove flooding): EMERALD experiment of ESA

Some aspects of the ESA space program EMERALD are presented. A problem of the film type condensation on curvilinear fin is considered with taking into account the essential influence of the capillary forces and non uniform temperature of the fin. Disjoining pressure effect on condensate film flow is studied numerically, because of very thin film of condensate on the fin tip. Value of the groove flooding depth changes significantly the condensate outflow from the condenser. Calculations for water condensation predict a very high value of the heat transfer coefficient, more than 50 kW/m²K, on a quite important part of the surface area and confirm the idea of proposed condenser and Double Capillary Pumped Loop.