Asphaltene cracking in catalytic hydrotreating of heavy oil
A Boscan crude, an Athabasca bitumen and a Khafji vacuum residue were chosen as typical asphaltenic feedstocks for this study, since they contain a lot of asphaltenes as well as sulfur and their metal contents are considerably different from one another. Any changes on these asphaltenes caused by metals and sulfur removal should, therefore, be observed easier than on other asphaltenes similar to one another. Various measurements reported here vapor pressure osmometry, gel permeation chromatography, nuclear magnetic resonance, x-ray diffraction, small angle x-ray scattering and electron spin resonance are mainly for the asphaltenes isolated from these feedstocks and from their product oils. Further, the model of the asphaltene cracking mechanism is proposed from these results and is discussed in the correspondence with the activities and selectivities among demetallation, desulfurization and asphaltene cracking. The features of asphaltene cracking are summarized as follows: (1) the removal of vanadium and sulfur from asphaltenes; (2) the decrease of molecular weight of remaining asphaltene; (3) the decrease of unit number and no change of unit sheet weight; (4) no change of asphaltene macrostructure in the stacking portion (cracking occurring at the non-stacked portion); (5) no major change of asphaltene particle size; and (6) the change of vanadyl association type in remaining asphaltenes from free to bound state and the decrease of the dissociation energy of the vanadyl. According to these features, the model of asphaltene cracking previously proposed, was confirmed, where the main reactions are the destruction of asphaltene micelles caused by vanadium removal and the depolymerization of asphaltene molecules by removal of heteroatoms such as sulfur. By comparing the model with the reactivities and selectivities, it is shown that the contribution of the two reactions in the model for asphaltene cracking depends on the kinds of feedstocks.
- Research Organization:
- Chiyoda Chemical Engineering and Construction Co., Ltd., Tokyo, Japan
- OSTI ID:
- 6446174
- Report Number(s):
- CONF-810308-(Vol.2)
- Journal Information:
- Am. Chem. Soc., Div. Pet. Chem., Prepr.; (United States), Vol. 26:2; Conference: American Chemical Society symposium on the chemistry of engine combustion deposits, Atlanta, GA, USA, 29 Mar 1981
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ASPHALTENES
HYDROCRACKING
MOLECULAR WEIGHT
BITUMENS
REFINING
PETROLEUM
RESIDUAL FUELS
SULFUR
REMOVAL
VANADIUM
CATALYTIC CRACKING
CHROMATOGRAPHY
ELECTRON SPIN RESONANCE
NUCLEAR MAGNETIC RESONANCE
X-RAY DIFFRACTION
ASPHALTS
CHEMICAL REACTIONS
COHERENT SCATTERING
CRACKING
DECOMPOSITION
DIFFRACTION
ELEMENTS
ENERGY SOURCES
FOSSIL FUELS
FUEL OILS
FUELS
LIQUID FUELS
MAGNETIC RESONANCE
METALS
NONMETALS
OILS
ORGANIC COMPOUNDS
OTHER ORGANIC COMPOUNDS
PETROLEUM PRODUCTS
PROCESSING
PYROLYSIS
RESONANCE
SCATTERING
SEPARATION PROCESSES
TAR
THERMOCHEMICAL PROCESSES
TRANSITION ELEMENTS
020400* - Petroleum- Processing