Comprehensive analysis of multiple asphaltene fractions combining statistical analyses and novel visualization tools

Abstract

Marine heavy fuel oils (HFOs), derived from and often blended with hydrotreated residual cuts, typically possess high boiling point, viscosity, and molecular complexity, and so are inherently challenging to analyze at the molecular level. Their high asphaltene content is associated with undesirable phenomena including flocculation, deposition, and black paint formation in marine engines. Asphaltene fractions of eight HFOs were selected for analysis by Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) due to their differing behaviour, including responsiveness to additive chemistries designed to stabilise against asphaltene handling issues. A selected mass region was isolated and fragmented using infra-red multiphoton dissociation (IRMPD), and the relative heteroatom content in asphaltene cores and smaller aromatic moieties, and degree of alkylation and aromaticity, of the fragments generated for each sample compared. A more extensive elucidation of the molecular-level differences between the n-alkane insoluble asphaltene fractions is afforded, with key components underlying variation in bulk behaviour identified through statistical approaches. The approach presented allows additive packages to be adjusted to address asphaltene handling issues presented by more challenging samples, and simpler and more ubiquitous formulations may eventually be developed.