Determination of Asphaltenes in Petroleum Crude Oils by Fourier Transform Infrared Spectroscopy

Abstract

An analytical method was developed to quantitatively determine the asphaltene content in petroleum crude oils by Fourier transform infrared spectroscopy (FT-IR). Asphaltenes are a solubility class of compounds found in crude oils. They are black to dark brown solids defined by their insolubility in n-alkane solvents. The structure of asphaltene molecules is polynuclear aromatic rings with alkyl side chains and heteroatoms such as nitrogen, oxygen, and sulfur attached. Asphaltenes are known to cause oil well plugging and irreversible catalyst deactivation in refineries. The asphaltene content of 50 crude oils from a wide array of geochemical conditions was determined by the standard n-pentane insolubles method. FT-IR spectra of the 50 crude oils were collected using an attenuated total reflectance cell. A partial least squares model was generated to predict the amount of asphaltenes from 42 of the crude oils. The model was shown to have an R 2 value of 0.95 and a standard error of estimate of 0.92 wt %. An independent prediction set of eight crude oils was used to test the validity of the model. The prediction set was shown to have an R 2 value of 0.96 and a standard error of prediction of 0.99 wt %. The FT-IR method compares favorably with the current laboratory method in terms of results, is faster, and uses no solvents.

Bio-oil production from hydrothermal liquefaction of high-protein high-ash microalgae including wild Cyanobacteria sp. and cultivated Bacillariophyta sp.

“…bio-oil due to its more nitrogenous compounds as detected by GC-MS and higher nitrogen content ( Table 2). It was further found that, the spectra of bio-oil derived from high-protein algae were distinct from that of conventional petroleum crudes [36], which display stronger alkane peaks (3000-2800 cm À1 ) and exhibit weaker heteroatom associated peaks consistent with their higher hydrocarbon and lower heteroatom contents.…”

Asphaltene Content Measurement Using an Optical Spectroscopy Technique

“…18,19 Various techniques have been developed for the measurement of asphaltene content without the precipitation and extraction of asphaltenes. These methods are based on nuclear magnetic resonance (NMR), 20 Fourier transform infrared (FTIR), 21,22 near-infrared (NIR), 23 mid-infrared (MIR), 24 ultraviolet (UV), 25 and fluorescence spectroscopies. 26 These methods usually rely on a calibration curve that correlates the measurements with a gravimetric technique.…”

Recent Advances in the Characterization of Gaseous and Liquid Fuels by Vibrational Spectroscopy

“…A comparison with NIR data showed that the mid-infrared spectra lead to a more reliable differentiation between the samples. In the context of crude oil characterization it is a common analytical task to determine the so-called saturate, aromatic, resin, asphaltenic (SARA) compounds [84][85][86]. For this purpose, FTIR and NIR are commonly employed in combination with multivariate data analysis.…”