119This work was done using the methods of chemical and radiation chemical reduction of metal ions in a reverse micelle solution of nanoparticles (NPs) devel oped by Revina [1,2]. These methods allow the prep aration of stable metal nanoparticles [3] in the liquid phase and have some advantages:(1) Metal reduction and formation of nanoparticles are performed in the polar core of the micelle, i.e., in an organized medium, which favors the formation of nanostructured aggregates.(2) The micelle shell creates certain limitations to the growth of nanoaggregates, which gives rise to small sized particles.(3) It is possible to control the NP size by specify ing the size of the aqueous core of the micelle.(4) The use of reverse micelle solutions enables the use of advanced optical methods for detection and study of the evolution and adsorption/desorption of NPs.The goals of this work are the synthesis of Re NPs, the study of the effect of the initial NH 4 ReO 4 concen tration on the physicochemical properties of these particles, study of the optical properties of NPs, and determination of the concentration change upon stor age and adsorption on a support (γ Al 2 O 3 , ShN brand) surface.It is not by chance that rhenium is called "high tech metal." In recent years, the demand for rhenium, especially in electronic industry, catalysis and rocket and aircraft construction has rapidly increased [4]. EXPERIMENTAL Reagents. (i) γ Al 2 O 3 (ShN brand), employed as the support to prepare nanocomposites based on Re NPs, was provided by O. A. Boeva (Mendeleev Uni versity of Chemical Technology). (ii) Ammonium perrhenate NH 4 ReO 4 . The rhe nium weight fraction was no less than 69.2%. Appears as tetragonal crystals. Molecular weight 268.24 amu. Decomposition point 200°C. Solubility (in 100 g of water): 6.234 g at 20°C and 32.34 g at 80°C. Density: 3.63 g/cm 3 at 20°C [5]. (iii) Solvent (isooctane). (iv) Inert gas (Ar). (v) Surfactant (sodium bis(2 ethylhexyl)sulfosuc cinate (AOT)). (vi) Water (triply distilled). (vii) Aqueous solutions of the rhenium salt NH 4 ReO 4 with concentrations (mol/L): 0.04, 0.10, 0.15, 0.20, and 0.25. Preparation of reverse micelle solutions for the syn thesis of Re NPs using various methods for reduction of the metal ion. The appropriate amount of an aqueous solution of (NH 4 )ReO 4 of the required concentration according to the chosen degree of hydration ω, where ω is the water to AOT molar ratio in the reverse micelle solution: ω = [H 2 O]/[АОТ], was added to a 0.15 M solution of the surfactant (AOT). The concen tration of rhenium ions in the micelle water pool remained constant, [Re 7+ ] wp = const, depending on the chosen initial concentration of the salt, whereas the ion concentration in the reverse micelle solution increased in proportion to the ω value, i.e., [Re 7+ ] RMS ~ ω [1]. (a) Radiation chemical reduction of Re (RadChem) and synthesis of Re NPs [2]. The prepared reverse micelle solutions of Re, Re 7+ -H 2 O-0.15 M AOT-isooctane,were dispensed into dedicated glass tubes designed in such a w...

The total concentration of normal alkanes ( n -alkanes) in the most widespread sort of oil exceeds 20%, and the n -alkane concentration as a function of the molecular weight has a pronounced maximum in the range ë 7 -ë 10 . In petrochemical technology, these alkanes are both raw material and the end product of oil processing. The processes involving these alkanes are performed in the liquid and vapor phases near the saturation line in the supercritical region of state parameters and are accompanied by phase transitions. An insignificant change in the process parameters (pressure P and temperature T ) causes changes in the caloric properties (specific heat at constant pressure C p , enthalpy H , entropy S , and heat of evaporation ∆ H v ) by one to two orders of magnitude, which immediately affect the economic performance of the process.The experimental basis of this study was our precise experimental data on C  and also the most reliable published data on the caloric properties of normal alkanes (for extending the generalization range). The experimental data were obtained at 320-620 K and 0.5-60 MPa. C  was measured in the liquid and vapor phases in the immediate vicinity of the boundary line in a wide neighborhood of the critical point.Our own experimental data on C  were obtained using a modified closed-circuit adiabatic flow calorimeter equipped with a calorimetric flowmeter [1]. A substance under investigation was pumped through the main calorimeter and the calorimetric flowmeter by a pressure-balanced gear pump. The pressure in the circuit was created and measured with MP dead-weight pressure-gauge testers (class 0.05). The temperature at the inlet of the main calorimeter was measured with a PTS-10 standard resistance thermometer and, in parallel, with an absolutely tapped six-junction differential gold/platinum thermocouple over a wide range of state parameters. The differential part of this thermocouple measured the temperature difference across the main calorimeter, and a similar thermocouple measured the temperature difference ∆ T across the calorimetric flowmeter. The adiabaticity of the main calorimeter and the calorimetric flowmeter was controlled with 300-junction differential Chromel/Copel thermocouples sheathed in a heat-insulating sheath made of microfiber pressed basalt wool.Calculation showed that, taking into account all measures adopted, the confidence limit for the total error in measuring C p with allowance for the nonexcluded residues of the systematic and random error components and also the assignment errors did not exceed 0.4% over a wide range of state parameters at a confidence level of α = 0.95. Near the saturation line (0.5-1.5 K) with allowance for the assignment errors, the error in a single measurement of C p reached 3% or more. This is explained by the fact that, as the boundary curve is approached both from the liquid side and from the vapor side, C  sharply increases and, hence, ∆ T decreases.To decrease this error, for the main calorimeter, a six-junction differential Chro...

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