Applicability of the Langmuir Equation of State for Asphaltene Adsorption at the Oil–Water Interface: Coal-Derived, Petroleum, and Synthetic Asphaltenes

Abstract

Preparation of synthetic asphaltenes: a) 1,2-bis(4-bromophenyl)-3,4,5,6-tetraphenylbenzene A mixture of tetraphenylcyclopentadienone (5.0 mmol), and bis(p-bromophenyl) acetylene (5.0 mmol) in diphenyl ether (20 ml) was heated to 260 °C overnight. Then the temperature was raised to 270 °C. After 69 h, the reaction mixture was cooled, and methanol (100 ml) was added. After stirring for 1 h, the product was filtered off, washed with methanol, and finally dried in vacuum overnight. Yield: Quantitative. b) 1,2-bis(4-dodecylphenyl)-3,4,5,6-tetraphenylbenzene 1-dodecene (30.0 mmol) was slowly added to a 0.5 M solution of 9-borabicyclo[4.4.1] nonane in THF (65 ml), and the mixture was stirred at room temperature overnight. Then a solution of NaOH (45.0 mmol) in water (15 ml) was slowly added, and the mixture was stirred for 20 min. The dibromide (2.5 mmol) was added, followed by Pd(dppf)Cl2 (80 mg). The reaction mixture was stirred at room temperature for 5 h. Then TLC analysis indicated incomplete reaction, and the temperature was increased. After boiling at reflux overnight, the reaction mixture was cooled to room temperature and concentrated in vacuo. The residue was dissolved in CH2Cl2, washed with water and with brine, and then dried (Na2SO4). The dry solution was diluted with hexane, filtered thru celite, and concentrated in vacuo. Finally the product was purified by flash chromatography (SiO2, pentane w/ 5-10% CH2Cl2). Yield: 80 %. c) 2,5-didodecylhexaperihexabenzocoroneneThe didodecylhexaphenylbenzene (1.5 mmol) was dissolved in dry CH2Cl2 (750) ml, and argon was bubbled thru the solution for 15 min. Then anhydrous FeCl3 (45 mmol) dissolved in nitromethane (15 ml) was added, and the mixture was stirred at room temperature while being bubbled with argon. After 75 min, the reaction mixture was poured into methanol (1 l). The reaction mixture was then concentrated in vacuo to remove most of the CH2Cl2, and the precipitated product was filtered off, washed thoroughly with dilute hydrochloric acid and with methanol, and then dried in vacuo. The crude product was dissolved in hot THF, precipitated once again with methanol, and finally dried in vacuum overnight. Yield: 55 %.Confirmation of expected structure was first sought for by solid state NMR. 1H-MAS was performed to qualitatively evaluate the relative contribution of aromatic and aliphatic protons to the total resonance signal. 1H MAS solid state NMR signal shows that aromatic and aliphatic contributions are well separated. Deconvolution and integration of peaks leads to: Aliphatic protons: 72 %, Intermediate protons: 3 % Aromatic protons: 25 % The match with the expected structure (50-16 ratio between aliphatic and aromatic protons) appears to

Probing the Adsorption of Polycyclic Aromatic Compounds onto Water Droplets Using Molecular Dynamics Simulations

“…In addition, the perpendicular orientation of PAC molecules observed here can be partly attributed to the oxygen functional groups, such as ketone and ester, present in the chemical structures. For PAC molecules without oxygen moieties, their polyaromatic core may prefer parallel to the interface, as reported by Banerjee and co-workers [15][16][17][18]. Indeed, it has been suggested by Mullins and co-workers 19,20 that the presence of oxygen moiety can alter the preferred orientations of PAC molecules from being parallel to being perpendicular.…”

Combined interfacial shear rheology and microstructure visualization of asphaltenes at air-water and oil-water interfaces

“…In the last two decades, the interfacial viscoelasticity of asphaltenes have been studied, including air-water [15,[22][23][24][25][26][27][28][29][30][31] and oil-water interfaces with either air [32][33][34][35] or oil induced aggregation [14,[36][37][38][39][40][41][42][43] as well as oil-water interfaces with asphaltenes in the dispersed phase [43][44][45]. These studies have shown that the conditions by which the asphaltene film forms at the interface determine its rheological responses.…”

Effect of the Asphaltene Oxidation Process on the Formation of Emulsions of Water in Oil (W/O) Model Solutions

“…In the emulsions formation, the accumulation of asphaltenes at the water-oil interface forms a rigid film that directly influences the stability of the emulsion and prevents droplet coalescence of the dispersed phase [23,24]. According to Rane et al [25][26][27][28], asphaltenes form a film at the water-oil interface where asphaltene are adsorbed and form a stable multilayer that prevents separation of the immiscible phases. Because of their high polarity, asphaltenes can self-associate and be found at the water-oil interface as large aggregates, influencing the stabilization of the emulsions [29].…”