Molecular Behaviors on Asphaltenes during Atmospheric Residue Hydrodesulfurization

A two-stage hydrotreatment of the two atmospheric residues (LF-AR and KEC-AR) over the MoO3/γ-alumina catalyst at the first stage and the NiMo/γ-alumina catalyst at the second stage was performed. Evolution of various heteroatom classes in the asphaltenes during the hydrotreating process was examined, focusing on removing sulfur and nitrogen species from asphaltenes. Various heteroatom classes (C c H h , C c H h -S s , C c H h -N n , C c H h -O o , C c H h -N n S s , C c H h -O o S s , C c H h -N n O o , and C c H h -N n O o S s ) in the asphaltenes were analyzed by using Fourier transfer ion cyclotron mass spectrometry (FT-ICR MS) linked with atmospheric pressure photoionization (APPI). According to the changes of their relative abundance, double bond equivalent (DBE), and the carbon number in the hydrotreating process, behaviors of the various heteroatom classes in the asphaltenes during the hydrotreating process were interpreted. Two distinctive differences in heteroatom reduction were observed for two different AR samples, and qualitative evaluation was attempted for providing possible scenarios.