Asphaltene treated

Reaction with Aluminum Chloride. Asphaltene reacts readily with AlCl3 even at temperatures well below 100° C. The characteristics of the product, mainly in terms of solubility, are strongly influenced by the reaction medium (Table I). Asphaltene treated with AlCl3 in benzene remains fully soluble, while when the remaining solvents are used as a reaction medium the solubility drops to a mere 10%-20%. 

To characterize the systems in which adsorption was measured, the wettability of clean and asphaltene-treated quartz crystals and Berea cores was assessed by several criteria. Water-advancing contact angles, meas-... 

Waterflood recoveries were similar in the clean cores with any of the oils, and recoveries were higher in the asphaltene-treated cores (Figure 19). This kind of behavior has been associated with mixed-wettability systems (124—126), defined by Salathiel (125) as systems in which the small pores are water-wet, and the larger pores form continuous oil-wet channels that allow efficient displacement of oil by water. All three criteria used for wettability assessment (contact angle, end-point relative permeabilities, and waterflood recoveries) indicate more oil-wet conditions after asphaltene treatment. 

Sandstone rock surfaces are normally highly water-wet. These surfaces can be altered by treatment with solutions of chemical surfactants or by asphaltenes. Increasing the pH of the chemical treating solution decreases the water wettability of the sandstone surface and, in some cases, makes the surface medium oil-wet [1644]. Thus the chemical treatment of sandstone cores can increase the oil production when flooded with carbon dioxide. 

A feasible procedure for the recovery of oil from the residual solids in the first stage of coal hydrogenation consists in treating the heavy oil slurry from the hot catchpot with superheated steam (25). At short contact times of a spray of heavy oil slurry with superheated steam, a high recovery of oil, with little or no coking or secondary asphaltene production, was achieved. 

Other chemical modifications pursued in our laboratories include metallation of the asphaltenes or halo-asphaltenes using metal or metallo-organics followed by, for example, carboxylation to the end product. Interaction of the asphaltenes with m-dinitrobenzene affords an oxygen-enriched material which, when treated with hydroxylamine or another amine yields materials containing extra nitrogen. Similarly, reaction of the asphaltenes with maleic anhydride and subsequent hydrolysis yields product bearing carboxylic acid functions. 

Figure 1. Test micrograph showing the displacement of the unscattered beam (small dots) in the selected area diffraction (SAD) pattern when it occurs in polar coordinates (Philips EM 300). The tilt has been fixed at the 002 Bragg angle for carbon ( 0.3°) and the azimuth changed by small increments. The 000 spot displaces along a practically perfect circle which corresponds to the 002 Debye Scherrer ring. Such a device allows exploration of any position in the SAD pattern, even when neither sharp nor intense hkl reflections are visible. The SAD pattern of an asphaltene heat-treated at 500°C has been superimposed to the test micrograph. Various positions of a 0.13 A aperture are shown.

Asphalt Solubility in Normal Alkanes. The separation of an asphalt into two fractions—asphaltenes and maltenes—by precipitation with low molecular weight alkanes is a physical method of separation based on solubility. Figure 1 shows that pentane precipitates more asphalt components (17.0 wt %) than does heptane (10.6 wt %). It would be expected that when pentane asphaltenes are treated with heptane, the amount of material equal to 10.6 wt % (based on asphalt) would be precipitated. However, more—14.8 wt %—is precipitated. A similar, but even more pronounced, effect can be seen when heptane and decane treatments are compared (see Figure 1). 

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. 

Table IV. Chemical Composition of the Pentane and Benzene Fractions of AlCl3-Treated Asphaltene...

The product distribution indicates that a certain specific reaction between asphaltene and ZnCl2 takes place at quite low temperatures (150°-200° C) and results in substantial insolubilization of treated asphaltene for example, at 200° C about 55% of asphaltene becomes insoluble in benzene. The following possibilities can account for this insolubilization ... 

Hydrogenation studies were undertaken on the parent iron-tin treated coal (Drum 289) as well as the THF insolubles, preasphaltene, asphaltene and oil derived from a continuous reactor run as previously discussed. Studies with no additional catalyst added (case A) and with the addition of a sulphided nickel molybdate catalyst supported on alumina (case B) were performed. The results are presented in Table 1. The Ni/Mo catalyst in case B did not increase the conversion of the coal or the THF insolubles beyond that for case A because sufficient amounts of iron and tin materials were already... 

In the reaction of untreated preasphaltenes the yield of THF insoluble "residue was 40% by weight of the reactant asphaltol while the presence of iron reduced the residue yield to 30%. Tin had the largest effect in these reactions reducing the residue yield to 15%. The inter-conversions from reactions of the untreated, iron- and tin-treated preasphaltenes were all 91 1% and so the reduced polymerization resulted in increased yields of oil and asphaltene. 

Within oil-field emulsion breaking, the economics usually favor minimal heat input because light ends are not lost to the gas phase and fuel-gas consumption is minimized. Other significant effects caused by the addition of heat are an increased tendency toward scale deposition on fire tubes, an increased potential for corrosion in treating vessels, and a tendency to render asphaltenes insoluble (because of loss of light aromatic components), which may produce an interface pad problem. 

In some crude oils, high amounts of insoluble asphaltenes and inorganic solids with high surface charges (chiefly clays) will combine to form a stable solids interface pad. This interface problem is usually accompanied by poor water quality and excessive consumption of emulsion breakers. This type of interface pad is typically removed from a treating vessel by desand-desludging operations to form uneconomically treatable slop oils. Disposal costs of this slop may be high for either the oil producer or refiner. 

This problem occurs primarily in treating heavy crude oils and light asphaltic crude oils produced by miscible flooding. The addition of an asphaltene dispersant to the crude oil to prevent accumulation of insoluble asphaltenes may resolve this problem. 

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