Sample age effect on parameters of dynamic nuclear polarization in certain difluorobenzen isomers/MC800 asphaltene suspensions

Hüseyin Ovalioglu

doi:10.1515/chem-2021-0114

Abstract

Abstract Because of magnetic spin–spin interactivity between 19F nucleus of the solvent and delocalized electrons on the MC800 asphaltene, the Overhauser dynamic nuclear polarization (DNP) method is able to give a substantial boost in the signal acquired from studies focused on nuclear magnetic resonance (NMR). The suspensions of asphaltene in difluorobenzene isomers were studied using Overhauser effect type DNP and NMR investigations at room temperature in a small magnetic field of 1.53 mT. The used asphaltene was obtained from MC800 liquid asphalt from Heavy Iran. Each sample of the solvent medium was produced at three different concentrations of asphaltene. These samples were stored in the refrigerator for 7 years, until DNP parameters were found by new DNP tests. As a result, the influence of sample age on parameters of DNP was studied, and then the findings were analyzed.

Highlights

Asphaltene is the heaviest and most viscous aromatic component of crude oil
This study aimed to investigate the dynamic nuclear polarization (DNP) parameters (A∞, U∞, ρ, f, s, and K) of difluorobenzene isomer solvents in MC800 asphaltene free radical against time at room temperature at 1.53 mT low magnetic field
The whole DNP phenomenon theory through the Overhauser effect in free radicals solutions has already been published in the technical literature [15–20]; in this article, we present just a short overview of the theory that applies to our study

Summary

Introduction

Asphaltene is the heaviest and most viscous aromatic component of crude oil. It is the most polar component, being soluble in aromatic solvents such as toluene and xylene but insoluble in normal aliphatic hydrocarbons such as n-heptane and n-hexane [1–3]. Its stability is affected by different parameters, including the pressure, temperature, and characteristics of crude oil mixtures [4,5]. Asphaltenes, are a part of petroleum, are considered to be polar species, have greater aromatic complexes, and consist of heteroatoms (e.g., O, S, and N), alkyl chains, and certain metals [6]. Asphaltenes have unpaired electrons, which are observed in crude petroleum by using the electron spin resonance (ESR) experiments [7]

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