Toward Value-Added Applications of Asphaltenes

Abstract

Asphaltenes are the heaviest fraction of crude oils. Asphaltenes are composed of carbon rings with aliphatic side chains, and they are precipitated from crude oils with small-chain alkanes, such as pentane or heptane. This complex class of molecules can be problematic during oil extraction, production, and transportation because asphaltenes are known to precipitate and adsorb onto surfaces. Therefore, there is extensive motivation to better understand the chemistry and behaviour of asphaltenes. The literature of asphaltene research is long and extensive. However, the vast majority of the research is motivated by understanding its chemistry. There is very little research into applications of this material. This dissertation strives to remedy this by exploring several different applications of asphaltenes. Asphaltene is a rich source of carbon atoms and can be used as a precursor for graphitic carbon. Two different graphitic materials are made from asphaltenes: asphaltene-derived thin films and electrospun carbon fibres. The electrochemical reactivities of these materials are found to be comparable to glassy carbon. Asphaltene is also used as an additive to electrospin composite fibres with polyethylene oxide, polyvinylpyrrolidone, and polyacrylonitrile. Smooth fibres are successfully spun with polyvinylpyrrolidone and polyacrylonitrile, and subsequently carbonized in an inert atmosphere. Asphaltene is found to have a positive effect on carbon yield, increasing the diameter of carbonized fibres, compared to those without any asphaltene additive. Finally, an asphaltene coating is used to construct a simple solid-phase microextraction device for the extraction and detection of four polycyclic aromatic hydrocarbons (fluorene, fluoranthene, pyrene, benz[a]anthracene) using HS-SPME-GC. The limits of detection for the asphaltene-coating is lower than commercially available SPME fibres, such as PDMS and PA, and also superior to many advanced nanomaterials such as MWCNTs. These applications show asphaltenes can be more than just a problematic fraction of crude oils. Its properties can be exploited to create useful, value-added materials.