Asphaltenes and maltenes in crude oil and bitumen: A comprehensive review of properties, separation methods, and insights into structure, reactivity and aging

Abstract

Asphaltenes and maltenes, integral components of petroleum systems, wield profound influence over the properties of crude oils and derived products. This literature review reports their multifaceted behavior, shedding light on structural features, reactivity, contribution to material characteristics and methods for separation. A total of 229 articles were summarized in this report, with the highest number of publications relating to asphaltene structure and properties and the second highest number to asphaltene/maltene separation techniques. Less work has been done on properties of maltenes and reactions of maltenes and asphaltenes. Even though extensive knowledge has been gathered on the listed topics, there is still no consensus on some important aspects. Opinions differ on the exact appearance of asphaltenes in bitumen, with some studies suggesting a colloidal structure with asphaltenes at micelles cores, while also evidence for a complete dissolution of asphaltenes in the maltene fraction exists. Additionally, the aging processes are not yet explained in detail, with researchers stating that aromatics are most susceptible to aging and moving to the asphaltene fraction, but other studies listing the resins as the most altered fraction after aging. Hence, there are ample possibilities for future studies, including the development of separation methods for generating high asphaltenes and maltenes quantities, detailed mechanical investigations and larger and more diverse sample sets. This review aims to provide a suitable starting point for new research and to support the path to a post-carbon society and the search for alternative building materials.