Diffusion of petroleum asphaltenes through well characterized porous membranes
Because of the importance of asphaltenes in resid processing, it became desirable to obtain additional information on the size of asphaltenes and their ability to diffuse through pores. Direct measurements of asphaltene diffusion coefficients can provide information relating to the rate of mass transfer through catalytic size pores; but, in addition, with the Stokes-Einstein relation, a semi-quantitative measure of asphaltene molecular size can be made. Track-etched mica membranes provide a good model system in which to conduct diffusion measurements. All the pores are the same size and shape and are straight, meaning that no tortuosity factor need be considered. The asphaltenes used in this study were derived from a Middle East high sulfur vacuum resid. The diffusion coefficient for these Middle East high sulfur resid asphaltenes has been found to be 4.5 x 10/sup -6/ cm/sup 2//sec in toluene at room temperature. When used in the Stokes-Einstein relation (D = kT/6..pi.. eta a where k is Botzmann's constant, T is the absolute temperature, eta is the solvent viscosity and a is the molecule radius), a molecular diameter of approx. 16 A is obtained. Such a molecular size indicates that catalyst pore sizes of the order of 200 A or larger should be adequate to allow free diffusion of asphaltenes if high temperature and pressure effects can be neglected. In addition, the molecular weight of these asphaltenes has been calculated by approximation to be 3300.
- Research Organization:
- Standard Oil Co., Naperville, IL
- OSTI ID:
- 6485712
- 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
DIFFUSION
MOLECULAR WEIGHT
SIZE
MASS TRANSFER
MEMBRANES
MOLECULES
MUSCOVITE
PETROLEUM RESIDUES
POROUS MATERIALS
TOLUENE
AROMATICS
ASPHALTS
BITUMENS
ENERGY SOURCES
FOSSIL FUELS
FUELS
HYDROCARBONS
MATERIALS
MICA
MINERALS
ORGANIC COMPOUNDS
OTHER ORGANIC COMPOUNDS
PETROLEUM
PETROLEUM FRACTIONS
TAR
023000* - Petroleum- Properties & Composition