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 CO2-induced precipitation of asphaltenes from crude oil on a molecular level. The behavior of model and real oils subjected to high-pressure CO2 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 CO2 precipitated from crude oil at such conditions. It is supposed that CO2 is able to interact with precipitated asphaltenes. On the basis of the obtained spectroscopic data, the mechanism of CO2-induced precipitation of asphaltenes has been proposed.