Interactions in chromatographic separation of resins from deasphaltened crude oils studied by means of infrared spectroscopy and principal component analysis

Resins were extracted from crude oils by adsorption onto various particles followed by desorption using various solvent combinations in a two-step desorption procedure. The extracted resins were analyzed using infrared spectroscopy, followed by local principal component analysis on the polar and aromatic absorption bands. It was found that the adsorption and desorption processes can be related to interactions involving specific functional groups such as amides, esters and aromatics in the resins with the adsorbents and solvents. The results are discussed in terms of polar forces, hydrogen bonds, dispersion forces and acid-based characteristics. Polar functional groups in the resins were found to interact with polar groups at the adsorbents and with solvents by polar forces and hydrogen bonds. It is also found that the aromatic character of the extracted resins is greater when benzene is used as solvent than if polar solvents are used. When using a low-polarity adsorbent the extracted resins contain less polar functional groups than when using a high-polarity solvent, showing that dispersion forces are important in the extraction. Some intercrude differences were also found and discussed.