Galina V. Bondarenko

An infrared study of water vapour in the temperature range 573–723 K. Dimerization enthalpy and absorption intensities for monomer and dimer

A high-temperature high pressure cell with changeable path length was used to obtain the integrated intensities of the low density vapour in the spectral region λ = 2·7 μm along four isotherms in the range from 573 to 723 K. A linear dependence of the intensity was observed and interpreted in terms of the ‘monomer-dimer’ equilibrium. A dimerization enthalpy of 16·65 ± 3·77 kJ mol-1 has been found using the Arrhenius behaviour of the intensity isotherms. All isotherms intersect at zero pressure giving the total integrated intensity 54·92 ± 0·5 km mol-1. Rough estimation of the total intensity for the water dimer gives 318 ± 120 km mol-1.

Experimental Technique for Quantitative IR Studies of Highly Absorbing Substances at High Temperatures and Pressures

A new high-temperature/high-pressure IR cell with a changeable pathlength is described. The pathlength can be varied immediately during a run at high pressure and temperature with a driving mechanism attached to the body of the cell. This arrangement presents the possibility of avoiding most of the common and specific errors connected with intensity measurements in the difficult case of highly absorbing substances. The cell can be used up to 780 K at a pressure of 100 MPa. The algorithms of data processing and examples of representative spectra of water are also discussed.

Comparison of the sensitivities of IR absorption and raman scattering spectra to hydrogen bonding in methanol

The sensitivity of infrared (IR) absorption and Raman scattering (RS) spectra to hydrogen bonding in methanol is quantified by a comparative sensitivity factor, which can be expressed as the K = (Ib/Iub)IR/(Ib/Iub)RS, where the indices b and ub refer to H-bonded and unbound (free) OH groups, respectively. The resulting value for methanol, K ∼ 20, is identical to that found previously for n-butanol, although the methods of measuring the degree of hydrogen bonding for these two alcohols were quite different. It is shown that, in some cases, Raman spectra can be converted to IR absorption spectra and vice versa. It is important for understanding differences in the shapes of OH stretching vibration bands in IR absorption and Raman spectra.

The causes of vertical zonation in the distribution of hydrocarbons over the Earth’s interior: Experimental evidence of the cracking of crude oil in high-temperature water-hydrocarbon fluids

Some specific features of the behavior and phase states of hydrocarbons have experimentally been studied at temperatures from 220 to 500°C and pressures of saturated vapor and higher (up to 150 MPa). The objects of study are synthetic fluid inclusions of quartz crystals grown under the conditions of the interaction between aqueous solutions and crude oil. It has been shown that the water-hydrocarbon fluids formed at a temperature below 320°C (at pressures of close to 30–50 MPa), depending on the thermobaric parameters and the quantitative ratio of water vapor (L1), oil (L2), and the gas phase (G), which generally consists of water vapor, may exist in a three-phase state (from L1 > G ≥ L2 to L2 ≥ L1 > G) or a two-phase state (from L1 ≥ L2 to L2 ≥ L1). No oil cracking is observed in such water-oil fluids. The fluids formed at temperatures above 330°C (and, especially, at 380–450°C) are characterized by the growth of the content of light and medium oil fractions with the simultaneous formation of gaseous hydrocarbons and residual solid bitumens; i.e., the hydrocarbons are subjected to cracking at the mentioned temperatures under hydrothermal conditions. The reheating of such multiphase fluids to temperatures of 240–280°C leads to the complete dissolution of their liquid phase and the fluid transits into a two-phase state (an aqueous solution and gaseous hydrocarbons saturated by liquid hydrocarbons). When the temperature increases from 350 to 380°C, the fluid either homogenizes into a one-phase liquid or gas state or becomes supercritical upon the attainment of the corresponding thermobaric parameters. The cooling of a fluid results in its heterogenization with the consecutive restoration of all its intermediate phases. On the whole, the experimental studies confirm the possible effect of the cracking of hydrocarbons on the appearance of vertical zonation in the distribution of oil-andgas deposits in the Earth’s interior.

Pressure dependence of the Raman spectra of aqueous solutions and anthracene

The shifts of the main bands in the Raman spectra during isothermal pressurization up to 140 MPa for anthracene and 1 M solutions of NaClO4 and Na2WO4 are measured using an optical cell with sapphire windows. The resulting shifts in the maxima of the spectral bands (from 0.6 to 1.1 cm−1 per 100 MPa) are close to the published value for a 1 M Na2SO4 aqueous solution.