Modern view at asphaltenes. (Lecture 4)

1. Modern view at asphaltenes

• The basic idea about the PDS dispersed phase resins, asphaltenes, carbenes and carboids
• Separating crude oil (SARA)
• Definition onset
• The various models of a structure asphaltenes :
packing (onion), continental (or island) and fractal
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2. Component analysis

• Paraffines [alkanes]:
n-/izostructure
Naphthenes: [cycloalkanes]
• Aromatic hydrocarbons [arenes]
• Hydrocarbons of mixed structure: in Diesel fraction and above
• Non-hydrocarbon oil components: S, N, O
• Mineral components: H2O, salts
• Macromolecular components
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3. High-molecular oil components

• Wax:
– С18-С35 (300-450 а.е.)
• Cerezines:
– С36-С55 (500-700 а.е.)
• Resins-asphaltenic substances (RAS):
– Resines:
– Asphaltenes:
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< 1000 а.е.
> 1000 а.е.
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4. RAS classification

• Resins:
• M <1000
• soluble in alkanes
• condensed systems related with aliphatic chains
• Asphaltenes:
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M > 1000
≈ 1 D and above
insoluble in alkanes
soluble in benzene,CS2, CCl4, etc.
tend to associations, define the structure of oil disperse systems
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5.

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6.

АFМ-image of asphaltenes at solid surface
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Energy&Fuels 2009

7.

Two approaches in development of
representations about structure RA
• Chemical
- structural formulas of molecules of resins and
asphaltenes СnH2n-z NpSqOr
(The calculated values z for resins 40-50,
for asphaltenes- 130-140)
• Physical
- packing model of asphaltene structure(Yen,1961);
- a scale sedimentators and solvents in relation to
asphaltene (Hotier, 1980);
- fractal model of a structure asphaltene(1994).
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8. Separating crude oil into saturates, aromatics, resins and asphaltenes (SARA)

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9.

The histogram of distribution of RAcomponents in oil and the oil rests
• The scheme of division of RA
• Oil + n-penthane (1:40)
100%
75%
• Asphaltenes (in a deposit) and
hydrocarbons + resines (in a
solution) ¯ method LAC
50%
25%
0%
Oil
Hydrocarbons
• Hydrocarbons (eluate - npenthane) and resins (eluate
pyridine)
Resins
Asphaltenes
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10. Molecular structure of proposed resin molecule

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11. The main properties and hypothetical asphaltene molecule

H/C = 0,8-1,4
molecular weight distribution
Monomers= 500-1000
Oligomers= 1000-5000
Heteroatoms, мас. %:
S = 0,5 - 10; N = 0,6 – 2,6; O = 0,3 - 4,8
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Metals: Ni, V, Fe
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12.

Asphaltenes extracted with two alkanes
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13.

Средние молекулярные массы асфальтенов,
определенные разными методами
Метод определения
Ультрацентрифугирование
Осмотическое давление
80
Ультрафильтрация
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Молекулярная масса,
тыс. у.е.
300
80 - 140
Эбулиоскопия
2,5- 4
Криоскопия
0,6 - 6
Осмометрия
1-8
Вязкость
0,9 - 2
Светорассеяние
1 -4
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14. Packing model of asphaltene structure (Yen, 1961)

• Packing structures in
diameter of 0,9-1,7 nm
from 4-5 layers, being at
0,36 nm each one from
other.
• By rectilinear pieces are
shown flat polyarenous,
and broken lines - the
saturated fragments of
molecules.
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15. The scheme of association asphaltenes in process of introduction sedimentator (lungs n-alkanes) in the PDS (T.Yen, 1961)

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I - molecular state
(up to 1 nm)
II – colloidal state
(1-100 nm)
III - disperse - stable state
(100 nm - 1 mc)
IY- disperse - unstable state
(> 1 mc)
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16. Organization level of ashaltens (1)

Monomers
Yen elementary particles (9 ÷ 17 Å)
Oligomers (25 ÷ 50 Å)
Polymers (> 150 Å)
+ Aggregation processes, including the
processes of gel / glass
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17. Organization level of ashaltens (2)

Monomers
Yen elementary particles
Oligomers (dimers, trimers, tetramers)
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18. Dimers structure

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19.

Molecular structures of proposed asphaltens molecules
(a) Maya crude oil (Mexico)
(b)Venezuelan crude oil
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20. The histogram of distribution of components in the ODS of a destructive origin (the rests of thermal processes of oil refining)

• The scheme of allocation
carbens and carboids
100%
hydrocarbons
+resins
asphaltenes
80%
60%
carbens
40%
20%
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asphaltenes (in solution CCl4) and
carbens + carboids
(in a deposit)
CS2
Carbens (in solution CS2) and
carboids (in a deposit)
0%
cracking
residues
Asphaltenes+carbens+ carboids
CCl4
pitches
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21. A way of looking at aggregation behavior of asphaltenes with increasing concentration

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22. The fractal model of consecutive aggregation of asphaltenes

Average density of a fractal
(r) = const / r D-d
• Weight of a fractal of M
(number of forming particles)
М ~ r d , where
r - radius particle,
d, D - topological and
fractal dimension
1 - paramagnetic skeleton of
asphaltenes
2- solvate layer formed by resins
3 - dispersive environment.
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