Communications Quinolin-65 and Violanthrone-79 as Model Molecules for the Kinetics of the Adsorption of C7 Athabasca Asphaltene on Macroporous Solid Surfaces Francisco Lo ´pez-Linares, Lante Carbognani, Manuel F. Gonza ´lez, Clementina Sosa-Stull, Maria Figueras, and Pedro Pereira-Almao* Schulich School of Engineering, Department of Chemical and Petroleum Engineering, UniVersity of Calgary, Calgary, Alberta T2N 1N4, Canada ReceiVed August 1, 2006. ReVised Manuscript ReceiVed September 12, 2006 Several of the major problems encountered at different stages in petroleum processing are related to the precipitation and consequent adsorption of petroleum asphaltene. This phenom- enon appears commonly following changes in operational conditions (temperature, pressure, and composition) resulting in the precipitation, flocculation, and adhesion of the asphaltene within the reservoir rock or production equipment. 1-7 Consid- ered one of the heaviest fractions of crude oil, asphaltenes are defined by their solubility in toluene and insolubility in n-pentane or n-heptane. 8 Asphaltenes are currently described as complex mixtures of molecules consisting of planar polyaro- matic cores containing 4-10 fused rings and polar functional groups. 9 Attached to the polar core are hydrophobic naphthenic rings and short aliphatic side chains. As a solubility class, asphaltene is remarkably polydisperse in carbon backbone structure, polar heteroatom functionality, and molecular weight. Because of the complexity of asphaltene structures, the studies of their adsorption behavior have some limitations. One of them is their isolation, which is a time-consuming procedure employ- ing large volumes of solvent. Considering that an adsorption experiment requires first the adsorbate for the corresponding study, recently, we reported the use of a set of structurally well- known molecules, commercially available, suitable, and capable of simulating the adsorptive behavior of averaged asphaltenic fractions, that helped in understanding their adsorption behavior from toluene solution over macroporous kaolin. 10 In these studies, it was found that model molecules can be selected to have specific properties similar to the ones present in the Athabasca Bitumen C7 asphaltene (AB-C7-A). This may include molecular weight, aromaticity, naphtenicity, heteroatom content, and nature of functional groups. 11 Thermodynamic and kinetic experiments were carried out using kaolin as an adsorbent, and the results indicated that the adsorption was governed by the presence of an aromatic framework, heteroatoms such as N, O, and to a lesser extent S and a minor dependence on molecular weight. A further study showed that an adequate balance between nitrogen, oxygen, and sulfur in connection with the type of aromatic moieties allows for the simulation of asphaltene adsorption with model molecules. 12 These results encouraged a search for other model molecules that would have a closer match to asphaltene properties to evaluate and simulate the adsorption studies of asphaltene over solid surfaces. The new molecules may contain the features previously described above, which we believe govern the adsorption phenomena. In this communication, a derivative of 2,3,7,8-dibenzopyrene containing N, O, and S, quinolin-65 (Q-65), and dibenzanthrones containing O, such as violanthrone-79 (VO-79) were selected as model molecules. They may resemble the adsorption behavior of Bitumen C7 asphaltene from whole Athabasca Bitumen (AB- C7-A), 10 Athabasca vacuum residue (VR), and Athabasca vacuum residue under a visbreaking process (VB). These model molecules represent the asphaltene of the continental type: one rather large aromatic region per molecule plus side chains. This agrees with the views of different authors. 13,14 However, other * To whom correspondence should be addressed. E-mail: ppereira@ ucalgary.ca. (1) Piro, G.; Canonico, L. B.; Galbariggi, G.; Bertero, L.; Carniani, C. Asphaltene Adsorption onto Formation Rock: An Approach to Asphaltene Formation Damage Prevention. SPE Prod. Facil. 1996, August, 156. (2) Pernyeszi, T.; Patzko, A.; Berkesi, O.; Dekany, I. Asphaltene Adsorption on Clays and Crude Oil Reservoir Rocks. Colloids Surf., A 1998, 137, 373. (3) Gonza ´lez, G.; Moreira, M. B. C. The Wettability of Mineral Surfaces Containing Adsorbed Asphaltene. Colloids Surf. 1991, 58, 293. (4) Gonza ´lez, G.; Moreira, M. B. C. Adsorption of Asphaltenes and Resins on Various Minerals, in Asphaltenes and Asphalts, 1; Yen, T. F., Ed.; Elsevier Science: Amsterdam, The Netherlands, 1994; p 219. (5) Yan, J.; Plancher, H.; Morrow, N. R. Wettability Changes Induced by Adsorption of Asphaltene. SPE Prod. Facil. 1997, 12, 239. (6) Crocker, M. E. Marchin, L. M. Wettability and Adsorption Character- istics of Crude-Oil Asphaltene and Polar Fractions, J. Pet. Tech. 1988, 470. (7) Al-Maamari, R. S. H.; Buckley, J. S. Asphaltene Precipitation and Alteration of Wetting: Can Wettability Change during Oil Production? paper SPE 59292 at the 2000 SPE/DOE IOR Symposium, Tulsa, OK, April 3-5, 2000. (8) Speight, J. G. The Chemistry and Technology of Petroleum; Marcel Dekker: New York, 1999. (9) Yen, T. F., Chilingarian, G. V., Eds. Asphaltene and Asphalts, 2. DeVelopments in Petroleum Science; Elsevier Science: Amsterdam, The Netherlands, 2000. (10) Lopez-Linares, F.; Sosa, C.; Gonzalez, M.; Pereira-Almao, P. The Adsorption of Asphaltene Compared to Model Heavy Molecules over Mac- roporous Solids. Prepr. Symp.-Am. Chem. Soc., DiV. Fuel Chem. 2005, 50, 786. (11) Strausz, O. P.; Lown, E. M. The Chemistry of Alberta Oil Sands, Bitumens and HeaVy Oils; AERI: Calgary, Alberta, Canada, 2003; Chapter 8, pp 151-177. (12) Gonza ´lez, M. F.; Sosa, C.; Lo ´pez-Linares, F.; Pereira-Almao, P. Comparing Asphaltene Adsorption with Model Heavy Molecules over Macroporous Solid Surfaces, Energy Fuels, manuscript submitted. (13) Groenzin, H.; Mullins O. C. Molecular Size and Structure of Asphaltenes from Various Sources. Energy Fuels 2000, 14, 677-684. (14) Rogel, E.; Carbognani, L. Density Estimation of Asphaltenes Using Molecular Dynamics Simulations. Energy Fuels 2003, 17, 378-386. 2748 Energy & Fuels 2006, 20, 2748-2750 10.1021/ef060354x CCC: $33.50 © 2006 American Chemical Society Published on Web 10/06/2006