Qualitative and Quantitative Analysis of Heavy Crude Oil Samples and Their SARA Fractions with 13C Nuclear Magnetic Resonance

Ilfat Rakhmatullin,Marat Gafurov,Vladimir Klochkov,Mikhail Varfolomeev,Sergey Efimov,Vladimir Tyurin,Ameen Al-Muntaser

doi:10.3390/pr8080995

Ilfat Rakhmatullin, Marat Gafurov + Show 5 more

Open Access

https://doi.org/10.3390/pr8080995

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Journal: Processes	Publication Date: Aug 16, 2020
Citations: 22	License type: CC BY 4.0

Affiliation: Kazan Federal University, Institute of Physics

Abstract

Nuclear magnetic resonance (NMR) approaches have unique advantages in the analysis of crude oil because they are non-destructive and provide information on chemical functional groups. Nevertheless, the correctness and effectiveness of NMR techniques for determining saturates, aromatics, resins, and asphaltenes (SARA analysis) without oil fractioning are still not clear. In this work we compared the measurements and analysis of high-resolution 13C NMR spectra in B0 ≈ 16.5 T (NMR frequency of 175 MHz) with the results of SARA fractioning for four various heavy oil samples with viscosities ranging from 100 to 50,000 mPa·s. The presence of all major hydrocarbon components both in crude oil and in each of its fractions was established quantitatively using NMR spectroscopy. Contribution of SARA fractions in the aliphatic (10–60 ppm) and aromatic (110–160 ppm) areas of the 13C NMR spectra were identified. Quantitative fractions of aromatic molecules and oil functional groups were determined. Aromaticity factor and the mean length of the hydrocarbon chain were estimated. The obtained results show the feasibility of 13C NMR spectroscopy for the express analysis of oil from physical properties to the composition of functional groups to follow oil treatment processes.

Highlights

Knowledge of the chemical composition of crude oil is necessary both for fundamental research and technological processes [1]
Our current work presents the new results of a comprehensive investigation of samples of four crude oils and their sixteen SARA fractions to obtain data on structural group composition using quantitative 13 C Nuclear magnetic resonance (NMR) spectroscopy in the magnetic field of B0 ≈ 16.5 T (f RF = 175 MHz)
Information on the content of general functional groups obtained by 13 C NMR spectroscopy can be useful for fast prediction of oil product properties that change under different types of treatment, in addition to the development of a fingerprinting approach

Summary

Introduction

Knowledge of the chemical composition of crude oil is necessary both for fundamental research and technological processes [1]. NMR spectroscopy has been known to be used for the characterization of petroleum components since 1959 [12,13,14,15,16,17,18] The significance of this unique spectral analysis in terms of efficiency lies in the fact that it allows the determination of the structure of complex natural molecules, and to determine their three-dimensional structure. Our current work presents the new results of a comprehensive investigation of samples of four crude oils and their sixteen SARA fractions to obtain data on structural group composition using quantitative 13 C NMR spectroscopy in the magnetic field of B0 ≈ 16.5 T (f RF = 175 MHz). Information on the content of general functional groups obtained by 13 C NMR spectroscopy can be useful for fast prediction of oil product properties that change under different types of treatment, in addition to the development of a fingerprinting approach

Materials and Methods

SARA Fractionation

Results and Discussion

Conclusions