Separation asphaltene

Without going into details of the chromatographic method, a SAR separation (asphaltenes having been eliminated) can be performed in a mixed column of silica followed by alumina. The saturated hydrocarbons are eluted by heptane, the aromatics by a 2 1 volume mixture of heptane and toluene, and the resins by a 1 1 1 mixture of dichloromethane, toluene and methanol. 

Conclusions from the Data. The preliminary data presented here show that (1) the separation scheme separated asphaltenes according to compound type (2) the Wilmington asphaltenes are a complex mixture of predominantly polar compound types (3) acids, as defined by the anion-exchange resin and IR spectrometry, are the predominant compound types in the mixture, amounting to 80% of the asphaltene and (4) the molecular weights of most individual molecules range from 500 to 800. These data suggest an answer to the question posed earlier Why... 

Analyses of deposit and stream samples from a commercial H-Oil unit indicate that several mechanisms influence fouling. The rejection of "vanadium- and nickel sulfides" from the catalyst and the precipitation of polycyclic aromatics appear to contribute to fouling in the reactor, reactor outlet line, and high pressure separator. "Asphaltene precipitation" is the prevalent fouling mechanism in the H-Oil vacuum tower. 

The chemical classification of petroleum that distinguishes between oils of a paraffin base from those of an asphaltene base was introduced into petroleum chemistry to distinguish the oils that separate paraffin on cooling from those that separate asphaltenes. The presence of paraffins is usually reflected in the paraffinic nature of the constituent fractions whereas a high asphaltic content corresponds with the naphthenic properties of the fractions. This could lead to the misconception that paraffin-base petroleum consists mainly of paraffins and that asphalt-base petroleum consists mainly of cyclic (or naphthenic) hydrocarbons. In order to avoid confusion, a mixed base has been introduced for those oils that leave a mixture of asphaltic petroleum and paraffins as residue from nondestruc-... 

Asphaltene Separation. Asphaltenes were isolated from bitumen (Athabasca) by using an excess of n-pentane (40 mL of n-C5Hi2 per gram of bitumen) and following... 

Fordedal and Sjoblom used dielectric spectroscopy to study several real erode oil emulsions and model systems stabilized with either separated asphaltenes and resins from crude oil or by commercial surfactants (55). Emulsions could be stabilized by the asphaltene fraction alone, but not by the resin fraction alone. A study of a combination of mixtures shows an important interaction between emulsifying components. F0rdedal et al. used dielectric spectroscopy to study model emulsions stabilized by asphaltenes extracted from crude oils (56). Analysis showed that the choice of organic solvent and the amount of asphaltenes, as well as the interaction between these variables, were the most significant parameters for determining the stability of the emulsions. 

Asphaltenes are obtained in the laboratory by precipitation in normal heptane. Refer to the separation flow diagram in Figure 1.2. They comprise an accumulation of condensed polynuclear aromatic layers linked by saturated chains. A folding of the construction shows the aromatic layers to be in piles, whose cohesion is attributed to -it electrons from double bonds of the benzene ring. These are shiny black solids whose molecular weight can vary from 1000 to 100,000. 

The complexity of petroleum products raises the question of sample validity is the sample representative of the total flow The problem becomes that much more difficult when dealing with samples of heavy materials or samples coming from separations. The diverse chemical families in a petroleum cut can have very different physical characteristics and the homogeneous nature of the cut is often due to the delicate equilibrium between its components. The equilibrium can be upset by extraction or by addition of certain materials as in the case of the precipitation of asphaltenes by light paraffins. 

Liquid chromatography is preceded by a precipitation of the asphaltenes, then the maltenes are subjected to chromatography. Although the separation between saturated hydrocarbons and aromatics presents very few problems, this is not the case with the separation between aromatics and resins. In fact, resins themselves are very aromatic and are distinguished more by their high heteroatom content (this justifies the terms, polar compounds or N, S, 0 compounds , also used to designate resins). 

Solvent deasphalting. This is an extraction of the heaviest fractions of a vacuum residue or heavy distillate. The extract is used to produce the bitumen. The separation is based on the precipitation of asphaltenes and the dissolution of the oil in an alkane solvent. The solvents employed are butane or propane or a butane-propane mixture. By selecting the proper feedstock and by controlling the deasphalting parameters, notably temperature and pressure, it is possible to obtain different grades of bitumen by this process. 

Fig. 11. Schematic of a residuum oil supercritical extraction (ROSE) process using compressed pentane to separate vacuum resids into asphaltenes (high...

Fractionation. Kett-McGee developed the ROSE process for separating the heavy components of cmde oil, eg, asphaltenes, resins, and oils, in the 1950s. This process was commercialized in the late 1970s, when cmde oil and utility costs were no longer inexpensive. In the ROSE process (Fig. 11), residuum and pentane ate mixed and the soluble resins and oils recovered in the supetctitical phase. By stepwise isobatic temperature increases, which decrease solvent density, the resin and oil fractions ate precipitated sequentially. 

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... 

The fractions obtained in these schemes are defined operationally or proceduraHy. The amount and type of asphaltenes in an asphalt are, for instance, defined by the solvent used for precipitating them. Fractional separation of asphalt does not provide well-defined chemical components. The materials separated should only be defined in terms of the particular test procedure. 

Residues containing high levels of heavy metals are not suitable for catalytic cracking units. These feedstocks may be subjected to a demetallization process to reduce their metal contents. For example, the metal content of vacuum residues could be substantially reduced by using a selective organic solvent such as pentane or hexane, which separates the residue into an oil (with a low metal and asphaltene content) and asphalt (with high metal content). Demetallized oils could be processed by direct hydrocatalysis. 

Solvent extraction may also be used to reduce asphaltenes and metals from heavy fractions and residues before using them in catalytic cracking. The organic solvent separates the resids into demetallized oil with lower metal and asphaltene content than the feed, and asphalt with high metal content. Figure 3-2 shows the IFP deasphalting process and Table 3-2 shows the analysis of feed before and after solvent treatment. Solvent extraction is used extensively in the petroleum refining industry. Each process uses its selective solvent, but, the basic principle is the same as above. 

Petroleum crude oil, gas condensate, and natural gas are generally complex mixtures of various hydrocarbons and nonhydrocarbons with diverse molecular weights. In order to analyze the contents of a petroleum fluid it is a general practice to separate it first into five basic fractions namely, volatiles, saturates, aromatics, resins, and asphaltenes [74, 77]. Volatiles consist of the low-boiling... 

Dispersants for Asphalts. Asphalt and asphaltene components can produce difficulties in various processes in recovering crude petroleum oils and preparing them for transportation through pipelines or in refining separation. 

Asphaltene precipitation, in many instances, carries from the well tubing to the flow lines, production separators, and other downstream equipment. It has also been reported (19) that asphaltic bitumen granules occured in the oil and gas separator with oil being produced from certain oil fields. 

The crude oil produced from the Main Zone of the Torrance Field has an API gravity of 18° and contains 5.3 weight percent asphaltenes. The solubility of the asphaltene molecules in Main Zone oil was measured by the Oliensis Test(35). In this test, the solubility parameter Qf ie oil was lowered by adding to the oil successively larger volumes of hexadecane, a poor solvent for asphaltene molecules. The minimum volume (in milliliters) of hexadecane, which when added to 5 g of crude oil, will cause the chromatographic separation of the asphaltene fraction is termed the Oliensis Number. The Oliensis Number for the Main Zone crude oil is 3, indicating that the asphaltene molecules are not well-solubilized in the oil. Small changes in the solubility parameter of the Main Zone oil can cause the asphaltenes to precipitate. 

Contact angle measurements for a water droplet on an asphaltene modified borosilicate surface confirmed that low concentrations of TFSA molecules change the wettability of the surface from fractionally-wet to water-wet. Table II shows the results of the contact angle measurements all reported results are the average of 10 separate measurements, none of which varied from the mean by more than 5° As the concentration of the TFSA... 

The iron sulphide in South African coals is a mixture of pyrite and marcasite (18). Although marcasite is known to transform into pyrite at elevated temperatures, separate spiking experiments were performed to see if pyrite or marcasite would show a preferential catalytic effect. The addition of pyrite and marcasite minerals (-200 mesh), to the coal showed equivalent total conversions, and yields of oil and asphaltene. 

Michael, G. Al-Siri, M. Khan, Z. H., and Ah, F. A., Differences in Average Chemical Structures of Asphaltene Fractions Separated From Feed and Product Oils of a Mild Thermal Processing Reaction. Energy Fuels, 2005. 19 pp. 1598-1605. 

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