Water soluble asphaltenes

Water-Soluble Asphaltenes with Commercial Thinners... 

The stabilization of water-oil emulsions happens as a result of the interfacial layers, which mainly consist of colloids present in the crude oil—asphaltenes and resins. By adding demulsifiers, the emulsion breaks up. With water-soluble... 

Figure 4. Degradation products from asphaltene fractions separated by Triton-B acids I, acidic fraction from water-soluble salts acids II, acidic fraction from water-insoluble salts...

The selection of asphaltene dispersant chemistry and dosages requires careful consideration. Most asphaltene dispersants are either light aromatic compounds with polar groups (e.g., cresylic acid) or highly water-dispersible or water-soluble surfactants. These materials will prevent insolubility of asphaltenes, but they also tend to adversely affect the dehydration of emulsions and to increase oil-in-water concentrations. 

The incorporation of Sb and As into the asphaltenes may involve a different mechanism from that of the metals as these elements may replace S in the asphaltenes. Degradation of the asphaltenes would possibly reduce alkyl or aryl arsines RxAsHa x or stibines, RxSbHa-x/ several of which are water soluble. 

Taylor (68) reported success in the demulsification of Kuwait crude oil emulsion with ethoxylated nonyl-phenol-formaldehyde (NPE) resins in which the EO content varied from 0 to 20 mol. They found optimum demulsification with n = 5 mol of EO per phenol group and strong evidence of NPE interacting with the asphaltenes of the bulk. Here, water solubility was changed with change in the length of the hydrophobic portion of the NPE resins. 

Asphaltenes adsorb in a manner limited by the diffusion of soluble asphaltenic aggregates to the oil-water interface, whereupon they self-assemble to form an elastic, rigid stable film of high mechanical strength. It is this film which is primarily responsible for the stability of asphaltenic W/0 emulsions. 

Emulsions stabilized by fine particles can be broken up if the wettability of the particles is changed by adding oil- or water-soluble demulsifiers. Iron sulphides, clays, and drilling muds can be made water wet, causing them to leave the interface and be diffused into the water droplets or they can be made oil-wet so that they can be dispersed in the oil. Paraffins and asphaltenes can be dissolved by the demulsifier to make their films less viscous, or crystallization and precipitation can be prevented [1, 3,16-18],... 

The asphaltene perchlorates are essentially insoluble in water or toluene, but have significant solubility in other solvents tetrahydrofuran, >0.5% acetone, 0.39% chloroform, 0.28% methanol, 0.17% benzene, 0.08%. The possibility that extraction with these or other solvents might bring about fractionation of the components is being investigated. 

Husack and Golumbic (4) reported the isolation of the phenolic acids from asphaltenes by extraction into Claisen alkali (KOH in water/methanol). In a somewhat similar approach, H-coal preasphaltenes were treated with several methanolic hydroxide solutions. The results, shown in Table V, show that 10%-12% of the preasphaltenes are soluble in methanol alone. Substantially more of these materials dissolve in 1.5M sodium or lithium hydroxide solutions. The greatest amounts of preasphaltenes were extracted by 1.5M solutions of quaternary ammonium hydroxide bases. Because Triton-B (ben-zyltrimethylammonium hydroxide) in methanol was capable of dissolving 65% of the preasphaltene materials, it was used in a more elaborate fractionation scheme. 

The products from these hydrogenations were separated into gases (analyzed by G.C.), water (analysed by azeotropic distillation), insolubles (CH2CI2 insolubles), asphaltene (CH2CI2 soluble/X4 insoluble) (Shell X4 40-60 C b.p. light petroleum), oils (CH2CI2 soluble/X4 soluble). Hydrogen transferred from the donor solvent was determined by G.L.C. analysis of the ratio of tetralin to naphthalene in the total hydrocarbon liquid product. 

Surface-active agents. Surface-active agents such as emulsifiers and surfactants play a very significant role in the stability of emulsions. They greatly extend the time of coalescence, and thus they stabilize the emulsions. Mechanisms by which the surface-active agents stabilize the emulsion are discussed in detail by Becher (19) and Coskuner 14). They form mechanically strong films at the oil-water interface that act as barriers to coalescence. The emulsion droplets are sterically stabilized by the asphaltene and resin fractions of the crude oil, and these can reduce interfacial tension in some systems even at very low concentrations (i7, 20). In situ emulsifiers are formed from the asphaltic and resinous materials found in crude oils combined with ions in the brine and insoluble dispersed fines that exist in the oil-brine system. Certain oil-soluble organic acids such as naphthenic, fatty, and aromatic acids contribute to emulsification 21). 

The methods of emulsion breaking (de-emulsification) are of importance in various areas of industry [39,61], especially in oil recovery in crude petroleum the content of highly saline water may be as high as 50 - 60%. Oil-soluble surfactants present in petroleum (asphaltenes, porphyrines, etc) and those introduced during tertiary recovery form highly developed adsorption layers at the water surface, and thus create structural-mechanical... 

The slow settling and consolidation after the suspension, reaching about 30% solids, have been attributed to the presence of unrecovered bitumen (Figure 9) (5) or to the presence of fine clays and amorphous materials, which either may hold amounts of water disproportionate to their concentration or may form an ordered floe structure at 30 wt% solids (4). One explanation emphasizes the possible role of soluble organic surfactants that modify the clay surfaces, the effect of strongly bound organic material on the minerals, asphaltenic components from... 

In 1960, Blair [59] and Dodd [68] published key studies on water-in-crude oil emulsions and their films (see [1-6] for references). Using a Cenco surface film balance to study the water-oil interface, Blair showed that the principal source of stability arises from the formation of a condensed and viscous interfaciai film by adsorption of soluble material from the petroleum phase, such film presenting a barrier to coalescence of the dispersed droplets. This primary film may be augmented by secondary adsorption of large particles or micelles originally suspended in the petroleum. The classical picture of emulsion stabilization by an adsorbed monolayer yielding low interfaciai tension values does not seem to be an accurate one in this case. It appears that a primary adsorbed layer is initially formed, almost certainly comprised of asphaltenes, and a secondary layer superimposes on this primary layer and is likely comprised of asphaltenes, wax particles, and possibly... 

McLean and coworkers [19,56] have investigated the effects of crude oil solvency and resin-asphaltene interactions on the stability of water-in-crude oil emulsions. They showed that there were three main factors that control the solubility of asphaltenes in crude oil, their tendency to aggregate, and their tendency to adsorb at oil-water interfaces. These are... 

MeLean and Kilpatrick (37) studied the effects of asphaltene aggregation in heptane/toluene mixtures on the stability of water-in-oil emulsions. The asphaltenes were separated from four different crudes with various heptane/toluene ratios, and various concentrations of asphaltenes and resin/asphaltene (H/A) ratios. The emulsions were most stable when the crude medium contained 30-40% toluene and a lower R/A ratio, i.e., R/A < 1. These results also show the significance of the solubility of the asphaltenes in determining the emulsifying potential for these crude oils (38-42). 

Resins are the materials which remain oil soluble after asphaltenes are precipitated in n-pentane or n-heptane, but are adsorbed on to surface-active material such as silica gel. They are a comparatively little known fraction (52, 53). Their composition is very much dependent on the separation procedure. The resin molecule is structiually similar to, but smaller than the asphaltene molecule and appears to be a good solvent for asphaltenes (17, 19). Because of its dispersion function for asphaltenes, researchers (35,36, 53, 54) started to note over recent years the influence of resins on the stability of water-in-crude emulsions. 

Generally, oilfield emulsions are most often W/O with the surface-active emulsifiers residing in the crude-oil continuous phase. According to the Bancroft rule (109) the phase for which the emulsifiers are most soluble is the continuous phase. The emulsifiers possess some degree of polarity which attracts them to the water phase. Solid emulsifiers would be very fine particles in a state of incipient flocculation (110). The emulsifiers may be one or more of the following solids whieh are partially hydrophobic with contact angle (9>90°), polar asphaltenes and resins with some partial insolubility indueed by solvents which dilute the crude oils, or metalloporphyrins integrated within the asphaltenes (24, 25). 

In 1987, Eley et al. (72) used the pendant-drop retraction method in the study of film compressibilities of crude oil/water interfaces for three crudes. These varied in asphaltene content. Libya (Brega) had 0.46 g/L, Kuwait 3.7 g/L, and Tia Juana (Venezuela) 5.94 g/L. They added a dispersant containing a nonionic oil-soluble surfactant, and observed increased film compressibilities. The concentration of effective dispersant correlated with the asphaltene con-... 

Mechanical stabilization is a process where interfacial components act as particles, creating a mechanically stable film on the surface of the droplets. This film encapsulates the droplets and, due to its immobility and low solubility in both water and oil, creates a very stable emulsion. Asphaltenes, resins, wax particles, minerals, and clay are compounds believed to enhance the formation of mechanically stable films. 

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