Influence of Nonbasic Nitrogen Compounds and Condensed Aromatics on Coker Gas Oil Catalytic Cracking and Their Characterization

Contrastive fluid catalytic cracking (FCC) performances of coker gas oil (CGO) narrow-boiling fractions before and after HCl aqueous solution and furfural further treatment were investigated. Nonbasic nitrogen compounds and condensed aromatics in test oil samples were identified by negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) and gas chromatography and mass spectrometry (GC-MS), respectively. The results show that basic nitrogen compounds mainly retard the feed conversion and liquid products due to their interaction with Bronsted acid sites or Lewis acid sites during catalytic cracking reactions, while the nonbasic nitrogen compounds and condensed aromatics are hard to convert into smaller molecules, just resulting in obvious effects on yields of gasoline and diesel. Moreover, nonbasic nitrogen compounds with single N species are dominant in CGO, identified as carbazoles, cycloalkyl-carbazoles, benzocarbazoles, and cycloalkyl-benzocarbazoles. Condensed aromatics include three to four rings of large dynamic size, usually presented as chrysene, pyrene, and phenanthrene. These compounds deposit on the surface of catalysts and thus redundant coke is formed; consequently, entrances for other hydrocarbons into acid centers are jammed.