Deasphalting, solvent

The most common method used for asphaltene precipitation. It uses a solvent (light paraffin such as C3,C4,C5, and C7) to separate a residue into a deasphalted oil (DAO) and a pitch (asphaltene), containing the latter most of the impurities of the feedstock. DAO is normally used as FCC or hydroaacker feed. SDA is used in refineries to upgrade heavy bottoms streams to DAO that may be processed to produce transportation fuels. The process may also be used in the oil field to enhance the value of heavy crude oil before it gets to the refinery (Billon et al., 1997 McOrath, 2008). 

When used, it is always ahead of extraction. The primary goal is to remove asphaltenes, which could be a possible byproduct and to make the viscosity specification that is required. This is accomplished by asphaltenes separation by solubility of non-asphaltenes in a solvent and precipitation of asphaltenes using e.g. propane as a solvent. Secondary effects include Conradson Carbon reduced, metals reduced, saturates increased, viscosity index increased, and color improved. 

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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. 

Intermediate feedstock preparation processes such as direct hydroconversion of vacuum residues, solvent deasphalting, improved coking will also make their appearance. 

Lubricants. Petroleum lubricants continue to be the mainstay for automotive, industrial, and process lubricants. Synthetic oils are used extensively in industry and for jet engines they, of course, are made from hydrocarbons. Since the viscosity index (a measure of the viscosity behavior of a lubricant with change in temperature) of lube oil fractions from different cmdes may vary from +140 to as low as —300, additional refining steps are needed. To improve the viscosity index (VI), lube oil fractions are subjected to solvent extraction, solvent dewaxing, solvent deasphalting, and hydrogenation. Furthermore, automotive lube oils typically contain about 12—14% additives. These additives maybe oxidation inhibitors to prevent formation of gum and varnish, corrosion inhibitors, or detergent dispersants, and viscosity index improvers. The United States consumption of lubricants is shown in Table 7. 

Solvent Deasphalting This is the solvent extraction of virgin residuum to remove asphaltenes or other tarry constituents. The deasphalted oil may be further processed into lubricating oils and greases, or used as cat cracking feed. 

Lubricating Oil Manufacture This consists of solvent deasphalting, phenol treating, and solvent dewaxing. In dewaxing, waxy lube is diluted with a solvent such as propane or methyl ethyl ketone (MEK), and cooled to crystallize the wax which is then removed by filtration. 

Refinery product separation falls into a number of common classes namely Main fractionators gas plants classical distillation, extraction (liquid-liquid), precipitation (solvent deasphalting), solid facilitated (Parex(TM), PSA), and Membrane (PRSIM(TM)). This list has been ordered from most common to least common. Main fractionators are required in every refinery. Nearly every refinery has some type of gas plant. Most refineries have classical distillation columns. Liquid-liquid extraction is in a few places. Precipitation, solid facilitated and membrane separations are used in specific applications. 

The teed to the cat cracker in a typical refinery is a blend of gas oils from such operating units as the crude, vacuum, solvent deasphalting, and coker. Some refiners purchase outside FCC feedstocks to keep the FCC feed rate maximized. Other refiners process atmospheric or vacuum residue in their cat crackers. In recent years, the trend has been toward heavier gas oils and residue. Residue is most commonly defined as the fraction of feed that boils above 1,050°F (565 C). Each FCC feed stream has different distillation characteristics. 

Hood. R and Bonilla, J., Residue Upgrading by Solvent Deasphalting and FCC, presented at the Stone Webster 5th Annual Meeting, Dallas, Texas. October 12, 1993. 

Takeuchi, C. Fukui, Y. Nakamura, M., and Shiroto, Y., Asphaltene Cracking in Catalytic Hydrotreating of Heavy Oils. 1. Processing of Heavy Oils by Catalytic Hydroprocessing and Solvent Deasphalting. Ind. Eng. Chem. Proc. Des. Dev, 1983. 22(2) pp. 236-42. 

Solvent deasphalting Treatment Absorption Remove asphalt Vacuum tower residual, propane Heavy lube oil, asphalt... 

Propane deasphalting solvent deasphalting using propane as the solvent. 

The major solvent refining processes include solvent deasphalting, solvent dewaxing, lube oil solvent refining, aromatic extraction, and butadiene extraction. These processes are briefly described below. 

Solvent deasphalting is carried out primarily to recover lube or catalytic cracking feedstocks from asphaltic residuals, with asphalt as a byproduct. Propane deasphalting is the predominant technique. The vacuum fractionation residual is mixed in a fixed proportion with a solvent in which asphalt is not soluble. The solvent is recovered from the oil via steam stripping and fractionation, and is reused. The asphalt produced by this method is normally blended into fuel oil or other asphaltic residuals. 

Solvent deasphalted oils and residua to lighter products (12, 13)... 

Besides influencing over-all reaction rates, pore diffusion can cause changes in selectivity. An extreme example of this was observed (26) when a high molecular weight California solvent-deasphalted oil was hydrocracked over a small pore size palladium zeolite catalyst at high temperatures. The feedstock gravity was 16.4° API, and 70% boiled above 966°F. The resulting product distribution is compared with that... 

Figure 10. Interaction between catalyst pore size and feed molecular weight in hydrocracking a California solvent deasphalted oil...

Petroleum can be fractionated into four generic types of materials representing general chemical properties. These include saturated hydrocarbons, aromatic hydrocarbons, resins, and asphaltenes. The standard ASTM separation procedure (D2007) for isolating the asphaltenes and the other components in petroleum is based on solubility behavior and chromatography, as shown in Fig. 5. Commerically, many refineries utilize solvent separations to produce a solvent deasphalted oil which has lower impurity levels. 

Another processing option involves the use of solvent deasphalting (SDA) to treat the vacuum residuum prior to hydroprocessing (Hung etal.,... 

Fig. 16. Schematic flow diagram showing solvent deasphalting (SDA) combined with residuum hydrocracking (Howell et al., 1985).

Solvent deasphalting (Chang and Murphy, 1992 Van Tine and Feintuch, 1997) provides an extension to vacuum distillation and is a later addition to the petroleum refinery. Before its use, many processes capable of removing asphaltic materials from feedstocks were employed in the form of distillation (atmospheric and vacuum), as well as clay and sulfuric acid treatment. 

Thus, solvent deasphalting allows for the removal of sulfur compounds as well as nitrogen compounds and metallic constituents by balancing yield with the desired feedstock properties (Table 7-18 Figure 7-22) (Flynn et al., 1961). 

The ASCOT process is a residual oil upgrading process which integrates the delayed coking process and the deep solvent deasphalting process (low energy deasphalting, LED A) (Bonilla, 1985 Bonilla and Elliott, 1987 Hydrocarbon Processing, 1996). 

In the process, the vacuum residuum is brought to the desired extraction temperature and then sent to the extractor where solvent (straight run naphtha, coker naphtha) flows upward, extracting soluble material from the down-flowing feedstock. The solvent-deasphalted phase leaves the top of the extractor and flows to the solvent recovery system where the solvent is separated from the deasphalted oil and recycled to the extractor. 

The HOT process is a catalytic cracking process for upgrading heavy feedstocks such as topped crude oils, vacuum residua and solvent deasphalted bottoms using a fluidized bed of iron ore particles (Ozaki, 1982). 

The low energy solvent deasphalting process selectively extracts the more paraffinic components from vacuum residua while rejecting the condensed ring aromatics. As expected, deasphalted oil yields vary as a function of solvent type and quantity, and feedstock properties (Chapter 7). 

The MDS Process is a technical improvement of the solvent deasphalting process, particularly effective for upgrading heavy crude oils (Table 8-6) (Kashiwara,... 

The ROSE process is a solvent deasphalting process with minimum energy consumption using a super-critical solvent recovery system and the process is of value in obtaining oils for further processing. (Gearhart, 1980 Low et al., 1995, Hydrocarbon Processing, 1996 Northrup and Sloan, 1996). 

ASCOT process a resid (q.v.) upgrading process that integrates delayed coking and deep solvent deasphalting. 

Heavy feedstock any feedstock of the type heavy oil (q.v.), bitumen (q.v.), atmospheric residuum (q.v.), vacuum residuum (q.v.), and solvent deasphalter bottoms (q.v.). 

MDS process a solvent deasphalting process that is particularly effective for upgrading heavy crude oils. 

ROSE process a solvent deasphalting process (q.v.) that uses a super-critical solvent recovery system to obtain high-quality oils from heavy feedstocks (q.v.) for further processing. 

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