Changes in composition of atmospheric resid upon hydrodesulpurization

This article examines an atmospheric resid from Romashkino crude before and after hydrodesulfurization in order to show how high-resolution mass spectrometry (HRMS) can be applied to high-molecular-weight organic sulfur compounds and aromatic compounds. The original atmospheric resid and a hydrodesulfurized boiler fuel were subjected to adsorptive separation into fractions. Results are presented from an investigation of the fractions that are the most complex in composition, the ''heavy aromatic'' concentrates, the yields of which before and after hydrodesulfurization were 35% and 25.8% by weight on the original atmospheric resid. The data indicate that in the process of hydrodesulfurization, the hydrogenation of aromatic rings is followed by the splitting of the naphthenic rings. The homologue composition was determined along with the group composition. The distribution curves were investigated for the alkyl ions C /SUB n/ H/sup +/ /SUB 2n+1/ in the singlet monoisotope mass spectra. The number of alkyl substituents on the ring from the structure of the mass spectrum in the region of pseudomolecular ions is calculated. It is concluded that in the hydrodesulfurization of an atmospheric resid from Romashkino crude, hydroaromatic hydrocarbons and polythiaalkanes are removed, and alkylaromatic hydrocarbons and derivatives of pyrene, chrysene, benzothiophene, and dibenzothiophene are accumulated.