Title: Chemical and structural characterisation of nC7 asphaltenes extracted from atmospheric tower bottom and low waxy crude oil from Indian reservoir

Authors: Siddhant Kumar Prasad; Jitendra S. Sangwai

Addresses: Petroleum Engineering Program, Gas Hydrate and Flow Assurance Laboratory, Department of Ocean Engineering, Indian Institute of Technology Madras, Chennai 600-036, India ' Petroleum Engineering Program, Gas Hydrate and Flow Assurance Laboratory, Department of Ocean Engineering, Indian Institute of Technology Madras, Chennai 600-036, India

Abstract: Detailed studies on asphaltenes from Indian sources are scarce. In this study, nC7 asphaltenes were extracted from an atmospheric tower bottom and a low waxy crude oil using IP143-based method and characterised using elemental analysis, nuclear magnetic resonance, Fourier-transform infrared spectroscopy, matrix-assisted laser desorption-time of flight mass spectroscopy, X-ray diffraction, and scanning electron microscopy. Results show that both asphaltenes differ widely in structures and molecular weights. It was deduced that both asphaltenes might have formed from kerogen degradation process resulting in higher oxygen content. Lower molecular weight and structural parameters (NMR) of atmospheric tower bottom asphaltene could be due to degradation of aliphatic part during preheating before atmospheric distillation process. Although dispersed, the XRD derived aromaticity of petroleum asphaltenes seems to vary inversely with stacking height and average diameter of the aromatic sheets, possibly due to compact structure of the cluster resulting from decreased stack height. [Received: September 29, 2019; Accepted: November 9, 2019]

Keywords: asphaltenes; atmospheric tower bottom; characterisation; structure; waxy crude oil.

DOI: 10.1504/IJOGCT.2021.112880

International Journal of Oil, Gas and Coal Technology, 2021 Vol.26 No.2, pp.157 - 183

Received: 29 Sep 2019
Accepted: 09 Nov 2019

Published online: 22 Jan 2021 *

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