Abstract
A number of crude oils, fuel oils, and asphalts containing sulfur with a concentration in the range of 0.16–4.61 wt % were studied by the nuclear magnetic resonance technique. The NMR relaxation parameters were measured with a 08/PC laboratory NMR relaxometer made in-house according to TU 25-4823764.0031-90 and a computerized portable proton magnetic resonance analyzer. A multiexponential character of the spinecho envelope was revealed for all samples, which was deconvoluted into three exponentials having relaxation times of T 2A, T 2B, and T 2C. The obtained high-resolution NMR spectra of crude oil, fuel oil, and asphalt show that sulfur contributes to the width of all spectral lines. The slope of the T 1A, T 1B, T 1C, T 2A, T 2B, and T 2C plots varies depending on the temperature range of the measurement in all cases, thereby indicating a change in the activation energy E Ai of molecular motion. All of the activation energies increase with an increase in the sulfur concentration. Over the entire range of measurement temperatures, there is one activation energy for crude oils and two activation energies E A 1 and E A 2 for fuel oils, with the low-temperature activation energies having higher values. An analysis of the asphalt revealed five, not two, activation energies or intervals of constant E B 2 values (structurally-dynamically ordered phases of the shells of asphalt structure units).
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