Pilot unit for permanent transesterification of vegetable oils in supercritical methanol or ethanol media

Synthesis of methyl and ethyl esters of fatty acids via transesterification of vegetable oils in supercritical methanol and ethanol is carried out on a pilot installation with a continuous flow reactor. The corresponding procedures are described, and the results are analyzed. The effect of preliminary ultrasonic treatment of the initial mixture on the product yield is studied, and the correlation between the stability of the obtained emulsions and the composition of the initial mixture, as well as the intensity of the ultrasonic treatment, are determined. The isobaric heat capacity of the supercritical alcohol (methanol, ethanol) — vegetable oil mixtures is measured.     

Anisotropic pseudorotation of the photoexcited triplet state of fullerene C60 in molecular glasses studied by pulse EPR

Spin-polarized echo-detected electron paramagnetic resonance (EPR) spectra and the transversal relaxation rate T2(-1) of the photoexcited triplet state of fullerene C60 molecules were studied in o-terphenyl, 1-methylnaphthalene, and decalin glassy matrices. The model is composed of a fast (correlation time approximately 10(-12) s) pseudorotation of (3)C60 in a local anisotropic potential created by interaction of the fullerene molecule with the surrounding matrix molecules. In simulations, this potential is assumed to be axially symmetric around some axis of a preferable orientation in a matrix cage. The fitted value of the potential was found to depend on the type of glass and to decrease monotonically with a temperature increase. A sharp increase of the T2(-1) temperature dependence was found near 240 K in glassy o-terphenyl and near 100 K in glassy 1-methylnaphthalene and decalin. This increase probably is related to the influence on the pseudorotation of the onset of large-amplitude vibrational molecular motions (dynamical transition in glass) that are known for glasses from neutron scattering and molecular dynamics studies. The obtained results suggest that molecular and spin dynamics of the triplet fullerene are extremely sensitive to molecular motions in glassy materials.     

Framed aromatic polyurethanes based on an anionic macroinitiator, 4,4'-diphenylmethane diisocyanate,and 4,4'-dihydroxy-2,2-diphenylpropane: Metal-complex modification

Metal complexes are prepared from poly(oxyethylene glycol) and iron(III) chloride and studied as modifiers of framed aromatic polyurethanes. The latter polymers are synthesized on the basis of macroinitiators, 4,4'-dihydroxy-2,2-diphenylpropane, and polyisocyanate, which is a mixture of 4,4'-diphenylmethane diisocyanate and its branched derivatives. The interaction of iron(III) chloride with poly(oxyethylene glycol) is accompanied by redox processes that lead to its degradation and partial reduction of Fe(III) to Fe(II). Aromatic polyurethanes are modified in the concentration range of metal complexes from 0.5 to 20%. At a concentration of metal complexes of 4–7%, the polymer shows high mechanical characteristics and excellent thermal stability. The framed structure of aromatic polyurethanes hampers the effective contacts of coordinately bonded Fe atoms that are present in various oxidation states.     

Use of Additional Fast-Relaxing Paramagnetic Species for Improvement of RIDME Performance

A method of improving relaxation-induced dipolar modulation enhancement (RIDME) performance by an artificial increase of electron spin–lattice relaxation rate is introduced and tested on a model nitroxide biradical. A substantial increase of its electron spin–lattice relaxation rate is achieved by the addition of a fast-relaxing paramagnetic holmium complex to the sample solution. The electron spin–spin relaxation rate of the nitroxide does not change dramatically upon this addition. The suggested method allows obtaining a deep dipolar modulation in the RIDME experiment, which is free from distortions caused by spectral diffusion processes.     

Raman Spectra of <Emphasis Type="Italic">n</Emphasis>-Butane,Isobutane, <Emphasis Type="Italic">n</Emphasis>-Pentane,and Isopentane in a Methane Environment

We have studied the particular features of the Raman spectra of gaseous n-butane, isobutane, n-pentane, and isopentane in a methane medium at a pressure of 25 atm. It has been found that, under these conditions, changes in the conformational equilibria of these molecules are negligible, and most significant changes in the spectra are observed in the range of 2850–3000 cm^–1, in which bands corresponding to the stretching vibrations of CH₂ and CH₃ groups shift to lower frequencies. The data obtained will be usefull in determining the composition of natural gas using Raman spectroscopy.     

Self-organization in the van der Pol generator for nonextensive systems

Based on the S- and I-theorems of evolution of q entropy and q discrimination information, the process of self-organization developing in the van der Pol generator with variation of the feedback parameter at induced transitions between stationary states in an open nonextensive system is studied.