Toward molecular characterization of asphaltene from different origins under different conditions by means of FT-IR...

Asphaltene is one of the polar and heavy fractions of crude oil that is complex from a molecular perspective. For this reason, the interaction between asphaltene molecules and the surface, as well as the interaction of asphaltene with chemicals such as amphiphile, are not well identified. Fourier-transform infrared spectroscopy (FTIR) is a useful tool for identifying the functional groups of molecules, as well as intra-molecular and inter-molecular bonds. Through reviewing previous studies, here the peaks in an FTIR spectrum of an asphaltene molecule were divided into polar, aromatic and aliphatic groups and discussed using quantitative indices. Then, the difference in the FTIR spectrum of asphaltene with wax and resin was addressed according to molecular structure. The effect of common impurities such as moisture, CO₂ and saturated and aromatic compounds of crude oil in asphaltene on the FTIR spectrum is assessed. Moreover, the application of the FTIR spectrum of asphaltene is used to determine the API value of crude oil, the asphaltene onset is given. In addition, possible changes in the FTIR spectra of asphaltene are investigated by various processes such as pyrolysis, microwave and ultrasonic radiation. Also, asphaltene subfractions is also one of the best methods to better understand asphaltene components. This study examines the FTIR spectrum of asphaltene subfractions from conventional methods and examines the spectral properties, which in many cases can be useful to researchers working in this field.