Behavior of Asphaltenes in Crude Oil at High-Pressure CO2 Conditions: In Situ Attenuated Total Reflection–Fourier Transform Infrared Spectroscopic Imaging Study

An attenuated total reflection–Fourier transform infrared (ATR–FTIR) spectroscopic imaging approach has been used in situ to study CO 2 -induced precipitation of asphaltenes from crude oil on a molecular level. The behavior of model and real oils subjected to high-pressure CO 2 has been monitored, and precipitation has been detected. The precipitated species have been chemically analyzed in situ at high-pressure conditions. It has been observed that only asphaltenes with oxygen-containing functional groups that are capable of specific Lewis acid–base interactions with CO 2 precipitated from crude oil at such conditions. It is supposed that CO 2 is able to interact with precipitated asphaltenes. On the basis of the obtained spectroscopic data, the mechanism of CO 2 -induced precipitation of asphaltenes has been proposed.