1. Characteristics of hydrogen abstraction involved in thermal processing of heavy oil.
- Author
-
Liu, Xiao-Sa, Wang, Li-Tao, Huang, Zi-Bin, and Yuan, Pei-Qing
- Subjects
- *
ABSTRACTION reactions , *CHEMICAL kinetics , *HEAVY oil , *RADICALS (Chemistry) , *DENSITY functional theory - Abstract
• H-abstraction in heavy oil thermal processing was studied by DFT calculations. • Homolysis of alkanes produces alkyl primary C radicals active in H-abstraction. • H-abstraction by alkyl primary C radicals has Ea between 42 and 52 kJ.mol−1. • Homolysis of alkyl substitutes of aromatics mainly produces benzylic radicals. • Benzylic radicals cannot abstract H from n -alkanes or cycloalkanes. The characteristics of H-abstraction during thermal processing of heavy oil were studied through density functional theory calculations. Homolysis of alkanes produces two alkyl primary C radicals. They can all effectively participate in the H-abstraction from alkanes, alkyl substituents and cycloalkanes, with activation energies ranging from 42 to 52 kJ.mol−1. The homolysis of alkyl substituents of aromatics occurs preferentially at the C α -C β position, with bond energy as low as 317 kJ.mol−1. In the temperature range involved in thermal processing, homolysis of alkyl substituents mainly produces benzylic radicals rather than phenylethyl and phenylpropyl radicals. Except for abstracting tertiary H from branched alkanes, the abstraction of other types of H by benzylic radicals is not feasible in terms of reaction kinetics and reaction thermodynamics. Paraffinic heavy oil has higher thermal processing activity than naphthenic heavy oil due to differences in the number of radicals that can effectively participate in H-abstraction. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF