Yu. Yu. Tanashev

Thermal conductivity of a silica gel + calcium chloride system: The effect of adsorbed water

The effective thermal conductivity of a KSK porous silica gel + calcium chloride composite is measured at T=293 K using the hot-wire method, and the effect of the quantity w of sorbed water on it is studied. It is shown that the w-dependence of the thermal conductivity λ is determined by the degree of filling of the matrix pores with a salt + water system and by the phase transitions in this system. The value of λ increases with a filling increase, this occurring most sharply when a continuous phase of the aqueous solution of salt is formed inside the sorbent layer. The results obtained are adequately described by the Luikov-Bjurström model.

Preparation and study of porous uranium oxides as supports for new catalysts of stream reforming of methane

Abstract We describe the method of synthesis of the porous uranium oxides (U 3 O 8 and UO 2 ) with specific surface area as high as 10–15 m 2 /g. Physico-chemical structure and properties of these materials were studied by X-ray diffraction, scanning electron microscopy and adsorption techniques. Porous U 3 O 8 was used as a support for Ni- and Ru-catalysts for steam reforming of methane for new ICAR-process of direct nuclear-to-chemical energy conversion (Int. J. Hydrogen Energy 18 (1) (1993)) Catalytic activity as a function of the metal (Ni or Ru) content, temperature and contact time was studied in non-gradient catalytic reactor at P =1 atm and T =600–780°C. The catalysts studied were shown to be very active in methane reforming by steam and allow to reach at these conditions the hydrogen production rate as high as 17–18 n cm 3 /s per 1 gram of the catalyst. The reaction rate obeys the law r = k 0 exp(− E a / RT)(p m - p m ∗ ), where p m is a partial pressure of methane, p m ∗ is close to the equilibrium pressure of methane at temperature T . The activation energy E a was found to be 54 kJ/mol for Ru/U 3 O 8 catalysts. To reduce the expected contamination of the produced syn-gas by radioactive products of nuclear splitting under application in the ICAR process we build up a thin oxide (MgO, Al 2 O 3 ) layer, coating the porous uranium particle. The results of the coating study are also presented.

Synthesis of aluminum oxides from the products of the rapid thermal decomposition of hydrargillite in a centrifugal flash reactor: II. Physicochemical properties of the products obtained by the centrifugal thermal activation of hydrargillite

A variety of physicochemical methods were used to characterize the product of the rapid thermal decomposition of hydrargillite in a centrifugal flash reactor under the following conditions: the average particle size of the reactant, 80–120 μm; the temperature of the solid heating surface (plate or cylinder), 300–700°C; hot-zone residence time, ∼1 s; transfer of the product to the cooled zone of the reactor. The composition of the product and the extent of decomposition of hydrargillite were determined as a function of the processing temperature. The centrifugal thermal activation (CTA) of hydrargillite affords an X-ray-amorphous, highly reactive product with a developed surface and a disordered and inhomogeneous porous structure. This structure is capable of forming different modifications of aluminum hydroxide and oxide. The properties of the CTA product are compared with the properties of the earlier reported hydrargillite rapid decomposition products obtained using a gaseous heat-transfer agent (thermochemical activation product) or a fluidized bed of a granular heat-transfer agent (thermal dispersion product).

ICAR process (immediate catalytic accumulation of ionizing radiation energy) as a new promising approach to the development of cheminuclear power plants

Abstract A new thermocatalytic method, ICAR, for nuclear-to-chemical energy conversion is suggested. The method is based on a combination of both nuclear and catalytic reactors in the same technological volume, by loading the catalyst directly into the active (energy releasing) zone of a nuclear reactor. Two variations of the suggested method are studied, based on the endothermic catalytic reactions of methane- and methanol - steam reforming as well as on ammonia decomposition. The conditions of intensive heat release immediately inside the catalyst bed were simulated by means of an electron accelerator. A new type of uranium-containing catalyst for steam reforming of methane was synthesized and studied. These special catalysts, as well as conventional commercial catalysts being used in the ICAR method were shown to be capable of ensuring a considerable intensification of the energy-accumulating chemical reaction and of increasing the specific power loading of the energy conversion up to 100–150 kW dm−3. The results of mathematical simulation of direct thermochemical conversion of radiation (nuclear) energy are also presented. Some advantages of the ICAR method and expected difficulties of its practical application are discussed here in order to point out some problems that should be solved in the near future.

Initiation of underground fire sources

Porous structure parameters of different rank Kuzbass coal and gas- and mass-exchange processes under coal heating are analyzed. The main part of volatile matter is dissolved in the volume of coal beds. For all coal specimens, it is typical that mass fraction of methane and ethane decreases with temperature while mass fraction of hydrogen, carbonic oxide and ethane increases. The latter gases can be the sources of violent burning of coal beds. UHF pyrolysis of bituminous coal reveals physical balance and composition of gaseous products. The results permit coal rating based on carbonization, enable recommending the use of inert gases in underground fire fighting and allow estimating temperature level in fire source zones in coal beds based on chemical composition of emitted gases.

New approach to the novel synthesis of boehmite (γ-AlOOH) by microwave irradiation of gibbsite: Kinetics of solid-phase reactions and dielectric properties of the reactants

Microwave irradiation of gibbsite is suggested as a method of obtaining crystalline boehmite. The kinetics of solid-state transformations of gibbsite under microwave radiation has been investigated, and the dielectric properties of the initial and microwave-activated gibbsite samples have been determined. Extending the gibbsite irradiation time leads to an increase in tanδ. This indicates that microwave-activated gibbsite has a stronger capacity for dissipating microwave energy owing to the formation of an amorphous component containing a variable amount of weakly bound molecular water. The general chemical formula of the amorphous component can be represented as Al2O3 · xH2O (0.5 < x < 3.0). The results of this study can provide a basis for developing new, low-waste, resource- and energy-saving methods for the synthesis of crystalline boehmite and for converting it into γ-Al2O3 with acid-base and textural properties that are atypical of the known low-temperature modifications of Al3+ oxides.

Characteristics of a chemical reactor that is a loaded microwave resonator

Relationships for calculation of the following parameters of reactors with microwave heating of chemical reagents are presented: the coefficient of absorbed microwave energy distribution in the reactor (in the cavity between the resonator walls and reagents) and the efficiency of transformation of microwave energy into heat of the reagents. The range of variation of microwave properties of the reactor during variation of reagent properties is estimated, and the coupling parameters of the resonator with the external line that provide for a high efficiency are determined.

New low waste and energy saving technology for supports and catalysts production: Electron beam activation of oxygen containing solid compounds

We present the know-how of fundamentally new low-waste and energy saving support and catalyst production. High-energy electron beam activation of initial substances forms the basis of this technology. We report results of studies on the catalytically important properties of activated hydrargillite and kaolinite. They can be used in the synthesis of supports and catalysts.

SHF stand for performing high-temperature chemical processes

SHF stand for performing high-temperature chemical processes is designed. SHF stand includes high-Q cavity excited on H102 mode and the magnetron SHF generator of the level of SHF power of 1 kW, the operating frequency of 2470±100 MHz. The power of energy release up to 100 W/cm3, the rate of heating is more than 1000°C/sec. The study of selective catalytic pyrolysis of high-molecular hydrocarbons is performed. The formation of carbon nanostructure from alkanes has studied.

Physicochemical properties of TiO2 (anatase) prepared by the centrifugal thermal activation of hydrated titanium dioxide

The physicochemical properties of titania (anatase) prepared from hydrated titanium dioxide by centrifugal thermal activation (CTA) at 140–700°C were studied. It was found that the microstructure and the texture parameters of anatase prepared by the above method were considerably different from those of the samples prepared by the traditional thermal decomposition of titanium hydroxide. The conditions of centrifugal activation exerted a considerable effect on the structure and the texture parameters of the resulting anatase. The crystal structure of anatase prepared at a temperature lower than 650°C was imperfect, and it approached a regular structure only at a temperature of >650°C. At temperatures higher than 300°C, the samples of TiO2 prepared using CTA were characterized by higher specific surface areas, fine pore structures, and comparable mesopore volumes, as compared with the samples prepared by commonly used synthetic methods.