Structure and millisecond pyrolysis behavior of heavy oil and its eight group-fractions on solid base catalyst

Abstract

To understand the millisecond pyrolysis behavior of heavy oil over solid base catalyst from the near-molecular level and the relationship between the structural composition and the solid base catalytic cracking behavior of heavy oil, the Changqing vacuum residue (CVR) was firstly separated into eight group-fractions, then the modified Brown-Ladner method was used to calculate the average structural parameters. The Py-GC/MS apparatus was used to investigate the millisecond thermal and solid base catalytic pyrolysis behavior of CVR and its eight group-fractions. The results showed that the eight group-fractions from saturate to asphaltene showed different compositions and structures which provided valuable information for understanding the structure of heavy oil in depth. The millisecond thermal pyrolysis results could give the direct information of crackable alkyl side chains from C2 to C27, and aromatics from C6 to C14 for different group-fractions. The solid base catalyst significantly enhanced the cracking of alkanes and the aromatization of alkenes and alkadienes, leading to the increase of propene, butene, alkadienes and aromatics yields. Due to the difference in composition and structure, the eight group-fractions showed different cracking behaviors. The result of the present work implied that the proposed method based on the eight group-fractions separation, structural characterization and Py-GC/MS was helpful to understand the millisecond pyrolysis behavior of heavy oil directly from the near-molecular level.