Separation of asphaltene

However, for the past 30 years fractional separation has been the basis for most asphalt composition analysis (Fig. 10). The separation methods that have been used divide asphalt into operationally defined fractions. Four types of asphalt separation procedures are now in use ( /) chemical precipitation in which / -pentane separation of asphaltenes is foUowed by chemical precipitation of other fractions with sulfuric acid of increasing concentration (ASTM D2006) (2) solvent fractionation separation of an "asphaltene" fraction by the use of 1-butanol foUowed by dissolution of the 1-butanol solubles in... 

Fic. 5. Standard ASTM (D2007) procedure for separation of asphaltenes and other generic components in petroleum (after Reynolds, 1985). 

Although, n-pentane and n-heptane are the solvents of choice in the laboratory other solvents can be used (Speight, 1979) and cause the separation of asphaltenes as brown-to-black powdery materials. In the refinery, supercritical low molecular weight hydrocarbons (e.g., liquid propane, liquid butane, or mixtures of both) are the solvents of choice and the product is a semisolid (tacky) to solid asphalt. The amount of asphalt that settles out of the paraffin/residuum mixture depends on the size of the paraffin, the temperature, and the paraffin-to-feedstock ratio (Figure 3-10) (Girdler, 1965 Mitchell and Speight, 1973 Corbett and Petrossi, 1978 Speight et al., 1984). 

Figure 1. Separation of asphaltenes from petroleum residuum...

Some time ago work was initiated on chromatographic separations of asphaltenes and resins in various chromatographic systems (GPC, ion exchangers, adsorption) to compare their behavior in these analytical systems. Part of the results have been reported previously (10), but they are used here to provide a better overview of the results obtained from separating the same materials by various methods. Literature data on the various procedures were... 

McKay s solvent sequence completely eluted the Wilmington asphaltenes but did not elute all the Athabasca asphaltene samples and had to be extended by additional solvent mixtures to obtain good sample recoveries (cf. Figure 2). For large scale preparative separations of asphaltenes, the asphaltenes were dissolved in benzene and eluted with the same solvent, omitting the cyclohexane step. This accelerated the operation, but at the same time, as expected, the percentage of the neutral fraction now increased from 20%-21% to approximately 28%-30%, in reasonable agreement with the bulk results from the cyclohexane experiments (see Table III). Table III also shows the additional solvent systems used. 

A second fraction of organic acids was recovered from the water/methanol filtrate by adjusting the pH to 4.0 with hydrochloric acid followed by suction filtration. The precipitate was washed with water, dried in vacuo at 80° C and weighed (1.6 g, 14%). Ion Exchange Separation of Asphaltenes... 

In summary, the separation of asphaltenes from petroleum, heavy oil, and bitumen is not only a function of the amount of added diluent but also a function of the type and composition of the diluent (14, 22, 24). 

Table 10 shows the results of all four series of experi ments. Table 11 provides the summary results. The experiments entitled one-week standing were designed to determine if there was a separation of asphaltenes between the top oil layer and the lower emulsion layer. Table 10 shows that there is a eoneen tration of both asphaltenes and resins in the emulsion layer. One particular experiment shows low eoneentra tion (—0.04%) however, this result is felt to be anom alous. It is interesting to note that both the resins and asphaltenes are concentrated in the emulsion layer. In terms... 

Recently, we have been using electrophoretic mobility measurements in an attempt to support some of our hypotheses. Our experimental plan, however, required the separation of asphaltenes, resins and gas oil as it exists in the crude. To do this we basically used standardized technique //143/57 of the Institute of Petroleum. Electrophoretic mobility measurements were made of the whole crude. Cut 2 and Cut 3 plus asphalt when contacted with the standard... 

Boussingault (1837) and Marcusson (1931) did a remarkable job on asphaltenes of oil that was used to establish a procedure for the separation of these, developed by Nellensteyn (1933), based on the solubility of asphaltenes in carbon tetrachloride. This procedure converged to the method known today for the separation of asphaltenes using n-heptane or n-pentane as a flocculating agent. 

Speight, J. G. Long R.B. Trowbridge, T.O., (1984). Factors influendng the separation of asphaltenes from heavy petroleum feedstock s. Fuel, 63, 616-621 Speight, J. G., (1992) Molecular Models for Petroleum Asphaltenes and Implications for Processing. Kentucky University e U.S. DOE EAST, oil Shale. Symposium Proceedings, 177... 

Aqua-conversion. Catalytic process that uses catalyst-activated transfer of hydrogen from water added to the feedstock in slurry mode. The homogeneous catalyst is added in the presence of steam, which allows the hydrogen from the water to be transferred to the heavy oil when contacted in a coil-soaker system normally used for the visbreaking process. Reactions that lead to coke formation are suppressed and there is no separation of asphaltene-type material (Houde et al., 1998). 

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