Crude distillation residues

There are analogies between the characterization of crude distillation residues and the previous feeds. The main difference is that for atmospheric and vacuum distillation residues of crude PINA and H/C can be estimated only through the kind of analysis (such as NMR) not normally available in refineries. Moreover, their final boiling point is not defined and the internal distribution of the different hydrocarbon classes of alkanes, cyc/o-alkanes and aromatics has to be deduced in a different way. Inside each macro-class, the relative amount of the components can be derived from the following statistical distribution ... 

Figures 10 and 11 show some examples of model predictions of the feedstock characterization of crude distillation residues. Figure 10 compares model predictions with the experimental distillation curves of three Arabian atmospheric residues. Figure 11 shows the model ability in predicting the aromatic carbon content and the H/C of different feeds in comparison with some NMR data. A more detailed description and discussion of this residue characterization is reported elsewhere (Bozzano et al., 1995, 1998).

The distillation of crudes chosen for their yield in heavy fractions is the most common means. Bitumen is extracted from the residue from a vacuum distillation column (a few dozen mm of mercury), the latter being fed by atmospheric distillation residue. Unlike the practice of a decade ago, it is now possible to obtain all categories of bitumen, including the hard grades. 

Properly speaking, steam cracking is not a refining process. A key petrochemical process, it has the purpose of producing ethylene, propylene, butadiene, butenes and aromatics (BTX) mainly from light fractions of crude oil (LPG, naphthas), but also from heavy fractions hydrotreated or not (paraffinic vacuum distillates, residue from hydrocracking HOC). 

Feedstocks are light vacuum distillates and/or heavy ends from crude distillation or heavy vacuum distillates from other conversion processes visbreaking, coking, hydroconversion of atmospheric and vacuum residues, as well as deasphalted oils. 

The reaction mixture comprising 2,2,2-trifluoroethyl vinyl ether, 2,2,2-trifluoroethanol and potassium 2,2,2-trifluoroethylate was fractionally distilled, whereupon crude 2,2,2-trifluoroethyl vinyl ether was obtained which boiled at 42° to 45°C at 760 mm. More 2,2,2-trifluoroethyl vinyl ether was obtained when the distillation residue was returned to the bomb and reacted with acetylene in the same manner as hereinabove described. 

The reaction mixture was removed from the vessel and distilled at a pressure of 30-60 mm, and a bath temperature of 30°C to 50°C until the methanol had all been removed. The extremely viscous tarry residue remaining in the still pot was given a very crude distillation, the distillate boiling at B2°C to 1 32°C/2 mm. In an attempt to purify this distillate by a more careful distillation, 5.3 g of a liquid distilling from 53°C to 150°C/5 mm was collected. At this point, much solid sublimate was noted not only in this distillate but in the condenser of the still. 7 g of the solid sublimate was scraped out of the condenser of the still. Recrystallization of the sublimate from ethyl acetate containing a small amount of petroleum ether gave beautiful crystals melting at 175°C to 177°C (5 g). Infrared analysis confirmed that this compound was hydroquinone (9% conversion). 

High-Temperature Defoamers. Polyisobutylene compounds are particularly effective in high-temperature (300° to 1 XX)° F) treatments of hydrocarbon fluids [786,788], such as during the distillation of crude oil and coking of crude oil residues. Polyisobutylene compounds are less expensive than silicone-based compounds. 

J. Balzer, M. Feustel, M. Krull, and W. Reimann. Graft polymers, their preparation and use as pour point depressants and flow improvers for crude oils, residual oils and middle distillates. Patent US 5439981, 1995. 

The composition of crude oil may vary with the location and age of an oil field, and may even be depth dependent within an individual well or reservoir. Crudes are commonly classified according to their respective distillation residue, which reflects the relative contents of three basic hydrocarbon structural types paraffins, naphthenes, and aromatics. About 85% of all crude oils can be classified as either asphalt based, paraffin based, or mixed based. Asphalt-based crudes contain little paraffin wax and an asphaltic residue (predominantly condensed aromatics). Sulfur, oxygen, and nitrogen contents are often relatively higher in asphalt-based crude in comparison with paraffin-based crudes, which contain little to no asphaltic materials. Mixed-based crude contains considerable amounts of both wax and asphalt. Representative crude oils and their respective composition in respect to paraffins, naphthenes, and aromatics are shown in Figure 4.1. 

Reduced crude a residual product remaining after the removal, by distillation or other means, of an appreciable quantity of the more volatile components of crude oil. 

Methylal and sodium formate may be obtained from the first distillate of the main reaction mixture. The crude distillate is placed in a flask fitted with a reflux condenser and to it is added a solution of 200 g. of sodium hydroxide in 300 cc. of water. The methyl formate is hydrolyzed to sodium formate. The methylal layer is separated, dried over calcium chloride and distilled. In this way 240-260 g. of methylal, boiling at 37-420, is obtained. By evaporating the watery portion to dryness there is obtained a residue of about 280 g. of crude sodium formate. 

The mixture is extracted with ten 175-ml. portions of benzene or 1 1 benzene-ether mixture (Note 4). The combined extract is washed with 75-ml. portions of water until the washings are neutral to litmus. The organic solvent is removed by distillation on a steam bath. The crude oily residue is converted directly (Note 5) to the /3-tetralone bisulfite addition product. 

The most advanced primary crude distillation units of this period, however, were constructed with continuous pipe stills for initial heating and partial vaporization, the effluent from the pipe still heater being discharged into a large evaporator, where the vapors were separated from the residual liquid. 

A solution of 21.3 g. (0.10 mole) of freshly distilled N,N-dimethyldodecylamine (Note 1), 9.6 g (0.10 mole) of 94% <-butyl hydroperoxide (Note 2), and 0.050 g. of vanadium oxyacetylacetonate (Note 3) in 27 g. (34 ml.) of Cbutyl alcohol is placed in a 250-ml. round-bottomed flask fitted with a. thermometer, a reflux condenser, and a heating mantle. The reaction mixture is heated to approximately 65-70°, at which point an exothermic reaction begins. The heating is discontinued until the vigorous exothermic reaction subsides (about 5 minutes) and then the reaction mixture is heated at reflux (the reaction mixture boils at 90°) for 25 minutes. After the resulting mixture has been cooled to room temperature, it is analyzed (Note 4) to establish the absence oft-butyl hydroperoxide, and then concentrated with a rotary evaporator (30-35° bath with 30-40 mm. pressure). The crude solid residue is triturated with 50 ml. of cold (0-5°), anhydrous diethyl ether and then filtered under conditions which prevent exposure of the residual amine oxide to atmospheric moisture (Note 5). The residual solid is washed with 50 ml. of cold (0-5°) anhydrous diethyl ether and then dried under reduced pressure to leave 12.9-15.5 g. of the crystalline amine oxide, m.p. 131-131.5°. Concentration of the mother liquors and trituration of the residual paste with 25 ml. of cold (0-5°) anhydrous diethyl ether separates another 4.9-3.4 g. of the amine oxide, m.]). 130-131°. The total yield of the crystalline amine oxide (Note 6) is 17.4-18.9 g. (76 83%). 

Concentration of Type II Nitrogen or Type II Sulfur in Subfractions. When separating distillation residues of Oficina crude oil into asphaltenes, resins, and deasphalted oils using n-pentane, some drastic changes occur in nitrogen and sulfur distribution, as can be seen in Tables I and II. 

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