Asphaltene structure determination: FTIR, NMR, EA, ICP-OES, MS, XRD and computational chemistry considerations

Abstract

As complex hydrocarbon molecules, petroleum asphaltenes pose significant challenges in the crude oil production, making them the focus of many investigations in the literature. Despite this, fewer studies have examined in-depth the structure of asphaltenes. In fact, when trying to understand and predict the macroscopic properties of asphaltene especially its colloidal behaviors, knowledge of its micro and macro structures as well as its chemical composition is of crucial importance. In the present work, the asphaltene separated from one of the Middle East (Iranian) crude oil field is studied by different spectroscopic and diffraction techniques. Indeed, successful determination of asphaltene structure with monomer molecular formula of C90H50O15 and four repeating units via stepwise procedures for handling X-ray diffraction and NMR laboratory data, along with other techniques including FTIR, EA, ICP-OES, and MS, reflecting crucial complementary information, is presented. To optimize the current asphaltene structure, a computational chemistry method (DFT) is applied, and its results show excellent agreement with experimental data.