Asfaltenos policiclos aromáticos

Asphaltenes and Polycyclic Aromatic Hydrocarbons
Oliver C. Mullins Schlumberger-Doll Research

Collaborators: FLUORESENCE: H. Groenzin, L. Buch XANES: U. Bergmann, P. Glatzel, J. Fetzer, S.P. Cramer

Outline
1) Why study Crude Oils? 2) Asphaltene Molecular Weight – 25 Year Controversy 3) X-ray 4) Petroleomics 5) Conclusions

N

Deepwater Market will remain large for a long time.Information is at a Premium.

Undiscovered Gas
Undiscovered Oil
USGS Est. 2000

USGS Est. 2000

Est. from USGS 200 Man-Year
Onshore 47% 2205 TCF
Undiscovered Natural Gas Liquids

Onshore 53% 342 BBO

Offshore 47% 306 BBO

Offshore 53% 2464 TCF

USGS Est. 2000

648 BBO

778 BBOE

Offshore Onshore 46% 54% 111 BBNGL 95 BBNGL

206 BBO

Total = 1.6 TBO (= ~60 years at today’srate)

Oil Chemistry affects…
Athabasca Bitumen ρ>1 g/cc

Asphaltene

Wax
Diamondoids

Organic Scale
Gas Hydrate

Asphaltene Molecular Structure; >20 year, x10 fight!
Ring sizes known from STM, HRTEM, 13C NMR, Consistent with Optics + MO, C XRRS, Solubility OR... 10 of these (NOT identical) cross linked EITHER this...

N

Fluorescence Depolarization
Polarized Excitation Ex

∆tRotation Random Walk

Rotational Diffusion

excited molecule

Polarized (in new direction) Emission

Em

Chromophore Selection
Use Excitation, Emission Wavelength to Select Chromophore Size
Fluorescence Intensity

285

333

400

450

500

600

UV

Visible

Fluorescence Emission Wavelength (nm)

1.2

UG8 Asphaltene
H. Groenzin, O.C. Mullins J. Phys. Chem. A(1999) H. Groenzin, O.C. Mullins E&F (2000) Editor’s Choice Article

Rotational CorrelationTime (ns)

1 0.8 0.6 0.4 0.2 0
400

Average Size
OEP
450 500

Solar Dye

550

600

650

Fluorescence Emission Wavelength (nm)

1500

Polarization Decay
typical

Fluorescence Intensity

1 0.8 0.6 0.4 0.2 0 400

1000

Intensity [counts]

500

0
66 68

nanoseconds

7072

74

76

450

500

550

600

650

Fluorescence Emission Wavelength (nm)

Which Asphaltene Molecule Description?
(This is correct!)

THEN

1) Small Rotation Times 2) Wavelength DEpendent Times 1 ns Rotation Cor. Time X X X X X

IF
and

0 ns X 400 nm 450 nm 550nm 650nm 1) BIG Rotation Times 2) Wavelength INdependent Times X X X X X

THEN IF

15 ns X Rotation Cor.Time 0 ns

450 nm

550nm

650nm

Fluorescence Depolarization
1) Asphaltenes are small! 2) Coal Asphaltenes much smaller than Petroleum Asphaltenes
1.4 1.2 KU Ven20 Resid UG8 0.8 Coal

(ns)

τc

1

0.6

0.4

0.2

0

Coal Asphaltene ~ 500 g / mole

400

450

500

550

600

650

Emission Wavelength (nm)

Petroleum Asphaltenes ~ 750 g / mole
E.BuenrostroGonzalez, et al, E&F 2001

1

O D
0 . 8

0 . 6

0 . 4

0 . 2

C U K R V 4 0 0 4 5 0

o a l G 8 U e s i d e n 2 0 5 0 0 5 5 0 6 0 0 6 5 0

0

E m i s s i o n

W

a v e l e n g t h

( n m )

Asphaltenes
Coal – Small alkane fraction, Small ring systems Oil - Large Alkane fraction, Large Ring Systems
0.7

0.6

Petroleum
Asphaltenes

0.5

(ns)

τc

0.4

FluoroDepol.

0.3

0.2

Coal
Asphaltene
0 1 2 3 4 5 6 7 8

0.1

13C NMR

Caro/Csat

π-System Stacking vs Steric Hindrance (Structure to Properties)
S

Asphaltene Solubility:

N H

N

From Petroleum: Lots-o-Alkane thus Lots-o-rings
Mol. Wt. 708

From Coal: Few Alkanes thus Few Rings
Mol. Wt. 309

Cracking makes smaller asphaltenes
L. Buch, H. Groenzin, E.Buenrostro-Gonzalez, S.I. Andersen, C. Lira-Galeana, O.C. Mullins, Effect of hydrotreatment on asphaltene fractions, Fuel, 82, 1075, (2003)

Asphaltene

Coke (insoluble)

N

N

N
N

Resin Asphaltene

X-Ray Spectroscopy
Sulfur XANES. 1s-3p à oxidation state
Geoffrey S. Waldo, Oliver C. Mullins, James E. Penner-Hahn, Stephen P. Cramer, Fuel, 71, 53 (1992)

Nitrogen XANES. 1s-π* à Pyrrole or...