Radical solvent-refined

Nature of the Free Radicals in Coals, Pyrolyzed Coals, Solvent-Refined Coal, and Coal Liquefaction Products... 

Solvent-Refined Coal. The solvent-refined coal (SRC 1) process (40) produces a low-sulfur, low-ash solid fuel from coal. Through the courtesy of L. Taylor, samples of SRC produced from five different feed coals were made available to us for ESR studies. Each of the five samples gave a strong ESR resonance near g=2 g values and spectral line widths are summarized in Table II. The g value and line width data, viewed collectively, suggest the presence of organic free radicals, with only minor interaction (except possibly for the Monterey sample) between the unpaired electrons and heteroatoms in the samples. 

In an attempt to further elucidate the nature of the free radicals, ENDOR spectra of the asphaltenes were obtained. Unfortunately, these spectra revealed no hyperfine lines and consisted only of a matrix peak as was found for solvent-refined coal (4). 

The patent describing this development discloses that a mixture of a thermally stable phenolic antioxidant and a sterically hindered phosphite was used in a hydrotreated base stock. However, the heterosynergism between the radical scavenger (phenolic antioxidant) and the hydroperoxide decomposer (phosphite) was not shown in solvent-refined base stocks. An additional benefit of this technology is energy saving, due to extremely good control of viscosity. 

The refined grade s fastest growing use is as a commercial extraction solvent and reaction medium. Other uses are as a solvent for radical-free copolymerization of maleic anhydride and an alkyl vinyl ether, and as a solvent for the polymerization of butadiene and isoprene usiag lithium alkyls as catalyst. Other laboratory appHcations include use as a solvent for Grignard reagents, and also for phase-transfer catalysts. 

NMHC. A large number of hydrocarbons are present in petroleum deposits, and their release during refining or use of fuels and solvents, or during the combustion of fuels, results in the presence of more than a hundred different hydrocarbons in polluted air (43,44). These unnatural hydrocarbons join the natural terpenes such as isoprene and the pinenes in their reactions with tropospheric hydroxyl radical. In saturated hydrocarbons (containing all single carbon-carbon bonds) abstraction of a hydrogen (e,g, R4) is the sole tropospheric reaction, but in unsaturated hydrocarbons HO-addition to a carbon-carbon double bond is usually the dominant reaction pathway. 

Many of the available computations on radicals are strictly applicable only to the gas phase they do not account for any medium effects on the molecules being studied. However, in many cases, medium effects cannot be ignored. The solvated electron, for instance, is all medium effect. The principal frameworks for incorporating the molecular environment into quantum chemistry either place the molecule of interest within a small cluster of substrate molecules and compute the entire cluster quantum mechanically, or describe the central molecule quantum mechanically but add to the Hamiltonian a potential that provides a semiclassical description of the effects of the environment. The 1975 study by Newton (28) of the hydrated and ammoniated electron is the classic example of merging these two frameworks Hartree-Fock wavefunctions were used to describe the solvated electron together with all the electrons of the first solvent shell, while more distant solvent molecules were represented by a dielectric continuum. The intervening quarter century has seen considerable refinement in both quantum chemical techniques and dielectric continuum methods relative to Newton s seminal work, but many of his basic conclusions... 

In this review, we are interested in the ESR signal of stable free radicals (spin probes) dissolved in liquid environments with particular reference to water. The key question to be addressed is the effectiveness of the spin probe as transmitter to supply information on the host. First studies of paramagnetic solutes in liquids involved copper chelates in organic solvents [10] and transition ions in solution [11] with attempts to describe the ESR lineshape as being influenced by the Brownian tumbling motion of the paramagnet in the liquid state [12]. Subsequent theoretical refinements in the case of fast reorientation [13,14] (see also Refs [4,15]) with clear experimental confirmation [16] and further extension and experimental validation of the theory of the ESR lineshape to arbitrary reorientation rates [17-21] paved the way to the quantitative use of ESR to characterize the liquid state of matter. 

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