Influence of Graphene Oxide on Asphaltene Nanoaggregates
Journal article, 2021
Asphaltenes are a group of exotic hydrocarbons found in bitumen and other forms of heavy crude oil derivatives. These hydrocarbons, with elusive chemistry, give crude oil derivatives (CODs), such as bitumen, its characteristic properties. In bitumen, they form stable aggregates by interacting with other molecules, called asphaltene aggregates. Attempts have been made to enhance bitumen with nanoparticles, like graphene derivatives. Such studies have been successful in displaying the enhanceability of bitumen, but no studies have been directly focused on how the structural stability of asphaltene aggregates present in bitumen is affected by the incorporation of nanoparticles. The phase stability of the asphaltene aggregates is a pertinent question, which is often ignored. In this study, we investigate the physical impact of incorporating graphitic nanoparticles on the structure of bitumen. For this, we utilise graphene oxide (GO). GO is a form of polyaromatic nanoparticle with a similar structure to asphaltenes, such that both have molecular defects induced by heteroatoms. We have experimentally investigated the structural stability of the asphaltenes, using XPS, XRD and SEM-EDX to elucidate the interaction between asphaltenes and GO, and its implications for the stability of bitumen used for e.g., the surface layer of roads. In roads, asphaltene aggregates exist as stable structures, until GO has been introduced. The experimental results show that the introduction of GO initiates destabilisation of the asphaltene aggregates, and we discuss the destabilisation mechanism in this paper. Thereby, we conclude that counter intuitively, the introduction of graphene or GO has a negative impact on the structure of bitumen, thus hindering any functional enhancements to bituminous roads.