Crude Oil Asphaltenes Studied by Terahertz Spectroscopy

Area of Science:

• Materials Science
• Analytical Chemistry
• Petroleum Engineering

Background:

• Asphaltenes are complex organic molecules found in crude oil.
• Characterizing asphaltenes is crucial for understanding crude oil properties and refining processes.
• Traditional methods for asphaltene analysis can be time-consuming and destructive.

Purpose of the Study:

• To investigate the application of Terahertz time-domain spectroscopy (THz-TDS) for analyzing asphaltenes in crude oil.
• To establish a correlation between THz-TDS measurements and asphaltene content.
• To explore the spectral characteristics of asphaltenes in the terahertz frequency range.

Main Methods:

• Terahertz time-domain spectroscopy (THz-TDS) was employed to analyze neat crude oil samples.
• THz-TDS measurements were also performed on maltene (asphaltene-removed oil) for comparison.
• Analysis focused on changes in time delay and peak amplitude of the THz signal.

Main Results:

• A linear relationship was observed between the differences in time delay and peak amplitude (neat oil vs. maltene) and the asphaltene content.
• Asphaltene refractive index spectra showed variations at low THz frequencies and similarities at higher frequencies.
• Mild absorption by asphaltenes was detected, with narrow peaks attributed to adsorbed water molecules.

Conclusions:

• THz-TDS is a viable technique for non-destructively quantifying asphaltene content in crude oil.
• The spectral properties of asphaltenes in the terahertz range provide valuable compositional information.
• The presence of adsorbed water molecules on asphaltenes can be identified via THz absorption.