3D-RISM-KH molecular theory of solvation and density functional theory investigation of the role of water in the aggregation of model asphaltenes

Abstract

We applied a multiscale modeling approach that involves the statistical-mechanical three-dimensional reference interaction site model with the Kovalenko-Hirata closure approximation (3D-RISM-KH molecular theory of solvation) as well as density functional theory (DFT) of electronic structure to study the role of water in aggregation of the asphaltene model compound 4,4'-bis(2-pyren-1-yl-ethyl)-2,2'-bipyridine (PBP) [X. Tan, H. Fenniri and M. R. Gray, Energy Fuels, 2008, 22, 715]. The solvation free energy and potential of mean force predicted by 3D-RISM-KH reveal favorable pathways for disaggregation of PBP dimers in pure versus water-saturated chloroform solvent. The water density distribution functions elucidate hydrogen bonding preferences and water bridge formation between PBP monomers. The ΔG(298) values of -5 to -7 kcal mol(-1) for transfer of water molecules in chloroform to a state interacting with PBP molecules are in agreement with experimental results. Geometry optimization and thermochemistry analysis of PBP dimers with and without water bridges using WB97Xd/6-31G(d,p) predict that both PBP dimerization and dimer stabilization by water bridges are spontaneous (ΔG(298) < 0). The (1)H NMR chemical shifts of PBP monomers and dimers predicted using the gauge-independent atomic orbital method and polarizable continuum model for solvation in chloroform are in an excellent agreement with the experimental results for dilute and concentrated PBP solutions in chloroform, respectively [X. Tan, H. Fenniri and M. R. Gray, Energy Fuels, 2009, 23, 3687]. The DFT calculations of PBP dimers with explicit water show that bridges containing 1-3 water molecules lead to stabilization of PBP dimers. Additional water molecules form hydrogen bonds with these bridges and de-shield the PBP protons, negating the effect of water on the (1)H(C3) NMR chemical shift of PBP, in agreement with experiment. The ΔG(298) results show that hydrogen bonding to water and water-promoted polynuclear assembly bridging is as important as π-π interactions for asphaltene aggregation.

Simple and complex forms of disorder in ionic liquids

“…Conversely, many important features on the underlying statistical properties of real systems can be learned from the ability of approximate theories to reproduce or not cluster structures, particularly in comparison with cases where the agreement between theory and simulation is particularly good. Liquid state integral equation theories have been applied to RTILs, both from the perspective of structural properties [31,32] and thermodynamical properties, and in particular those related to solvation [33][34][35]. Refs.…”

Molecule–Surface Recognition between Heterocyclic Aromatic Compounds and Kaolinite in Toluene Investigated by Molecular Theory of Solvation and Thermodynamic and Kinetic Experiments

“…13 We have explored the molecular recognition between HAC and metalloporphyrins relevant to bitumen spectroscopic characterization, 14,15 the effect of the presence of trace amounts of water on asphaltene aggregation and other aspects of supramolecular interactions in heavy oils. 16,17 Kaolinite, a predominant Oil Sands clay mineral, is a 1:1 phyllosilicate made up of one tetrahedral silicon oxide sheet linked to an octahedral aluminum hydroxide sheet. 18−20 Numerous hydrogen bonds between the silicon dioxide and aluminum hydroxide surfaces from adjacent kaolinite layers hold kaolinite layers stacked together.…”

“…In bitumen and Oil Sands research, the 3D-RISM-KH theory of solvation has been employed to study the molecular recognition of thiophenic bitumen fragments toward transition metal ion-exchanged chabazite nanoparticle surfaces in the presence of benzene solvent 52 and adsorption of indole on kaolinite in toluene and heptane solvents 31 as well as the role of water in the stabilization of supramolecular asphaltene aggregates. 16 In this Article, we employ several experimental adsorption methods as well as the 3D-RISM-KH molecular theory of solvation to study the molecule−surface recognition between a series of HAC (Scheme 1) and kaolinite in toluene solvent. With this collaborative computational and experimental approach, we investigate the affinity, capacity, preferred molecular configurations and thermodynamics of adsorption between HAC and kaolinite surfaces.…”

Adsorption of Bitumen Model Compounds on Kaolinite in Liquid and Supercritical Carbon Dioxide Solvents: A Study by Periodic Density Functional Theory and Molecular Theory of Solvation

“…65 The effect of trace amounts of water in a chloroform solvent on the free energy of aggregation of model asphaltene compounds containing polyaromatic hydrocarbon moieties tethered to pyridyl groups has been investigated using the 3D-RISM−KH theory, and the contributions of hydrogen-bonding and π−π stacking interactions to aggregation are evaluated on the basis of electronic structure calculations. 66,67 Recently, we have reported on a 3D-RISM−KH investigation of the adsorption of indole on kaolinite and presented insights into its preferred adsorption orientation and effective interaction potential for adsorption in heptane and toluene solvents. The calculated multilayer adsorption profiles have been correlated with experimentally determined monolayer and saturation loading of organoclays driven by strong adsorbate− adsorbate interactions.…”