Experimental Studies on the Adsorption/Occlusion Phenomena Inside the Macromolecular Structures of Asphaltenes

Abstract

Asphaltenes are the polar macromolecules with complex structures in oils, usually existing as aggregates. Inside the macromolecular structures of asphaltenes, some other fractions can be adsorbed/occluded, and the occluded compounds contain some important geochemical information. However, the adsorption/occlusion phenomena of asphaltenes need verification. Thus, this work was aimed to experimentally study the adsorption/occlusion processes inside the asphaltenes, using the deuterated paraffin n-C 20 D 42 as the target compound under the conditions of high temperature/high pressure, with some chloride salts as additives to probe the mechanism of the adsorption/occlusion inside asphaltenes. The results show that the adsorption/occlusion phenomena take place inside asphaltenes during their thermal evolution. Occlusion inside asphaltenes could occur via two paths, namely, the physical process maybe through the polar interactions among the molecules and the chemical process through condensation or polymerization of the molecules, and then some substantial microporous units could develop to adsorb/occlude other fractions. The temperature and the additives have influences on the occlusion taking place inside asphaltenes. Higher temperatures promoted the pyrolysis of asphaltenes, and the additives play an important role in the properties of adsorption/ occlusion inside asphaltenes.

Metal porphyrin occlusion: Adsorption during asphaltene aggregation

“…Experimental evidence of the fractal-type structure of asphaltene aggregates suggest they could adsorb or trap other compounds from oils (Carbognani and Rogel, 2002;Liao et al, 2005;Liao et al, 2006;Yang et al, 2009;Zhao et al, 2012;Derakhshesh et al, 2013). These occluded compounds contain important geochemical information (Yang et al, 2009) about the aging and origin of the crude oil.…”

Determination of the series of even carbon numbered n-alk-1-enes trapped inside geomacromolecules

“…However, recent studies have shown that a series of even carbon numbered n-alk-1-enes are present in the trapped fractions of asphaltenes (Yang et al, 2009;Zhao et al, 2010Zhao et al, , 2012Tian et al, 2012) and solid bitumens (Cheng et al, 2012(Cheng et al, , 2013. They may be stable in these geomacromolecules owing to the protection afforded by the matrix, which inhibits transformation of the trapped n-alk-1-enes during later geochemical processes.…”

Electron Paramagnetic Resonance Study of the Fractions and Trapped Compounds in Asphaltenes of Merey Heavy Crude Oils and Its Vacuum Residue

“…This may be due to the presence of mobile petroporphyrins additional to the occluded petroporphyrins in the structure of asphaltenes generated by the action of the temperature on the samples in the vacuum towers. , Interaction of different compounds with asphaltenes and their aggregates is an interesting phenomenon, which is relevant to properties such as swelling and solvent interaction. This effect has been studied by several authors and the nature of the interaction still in discussion. − The adsorption and occlusion of different compounds in asphaltenes aggregates have been studied by Castillo et al; they proposed the existence of two mechanisms for trapping these molecules: occlusion and adsorption onto aggregates with the occlusion as the predominant effect …”