Distillate fractions characterization

One distinguishes preparatory distillations that are designed to separate the fractions for subsequent analysis from non-preparatory analytical distillations that are performed to characterize the feed itself. For example, the distillation curve that gives the recovered volume or weight as a function of the distillation temperature characterizes the volatility of the sample. 

Each petroleum cut obtained by mixing the TBP distilled fractions (and thus characterized by the TBP cut points) is described by a coiiection of properties including the viscosity at two temperatures. 

Their bulk properties as well as their chemical composition can characterize crude oils. Distillation of cmde oil provides fraction profiles over a certain boiling range. The crude oil as well as the distillation fractions can be described in terms of density, viscosity, refractive index, sulfur content, and other bulk parameters. 

Separation, Characterization and Analysis of the Distillate Fractions. Results from the analyses of the <200° C coal-liquid distillates (after removal of trace quantities of acids and bases) are summarized in Table IV. Results from the dual silica-gel/alu-mina-gel adsorption chromatography separations of the 200° to 325° C, 325° to 425° C, and 425° to 540° C coal-liquid distillates are summarized in Table V. Data for the acid and base extracts of the polyaromatic-polar adsorption fractions are also included in Table V. Summary data on analysis of the saturate fractions are listed in Table VI. Data in Table VI show a trend toward higher percentages of zero- and one-ring saturates in lower-rank coals. 

The remaining four distillate fractions were characterized in detail as was each liquid product obtained. The results for the starting materials are listed in Table I. 

CCB was fractionated into six asphaltene-free distillate fractions of varying boiling ranges and an asphaltene-rich non-distillable residue. Characterization of the distillate and the non-distillable fractions indicate significant differences in the asphaltene, ash, aromaticity, molecular weight and aromatic ring distributions. 

Work in the area of hydrocarbon-type analysis, i.e. saturate, olefin, and aromatic, has been conducted at the Laramie Energy Research Center (LERC) for over two decades. During this time, a significant portion of the eflFort has been directed towards the quantification and characterization of the various types of olefins found in Green River Formation shale oils and their distillate fractions (1-9). 

In addition to the whole crude oil tests performed as part of the inspection assay, a comprehensive or full assay requires that the crude be fractionally distilled and the fractions characterized by the relevant tests. Fractionation of the crude oil begins with a true boiling point (TBP) distillation using a fractionating column with an efficiency of 14-18 theoretical plates and operated at a reflux ratio of 5 1 (ASTM D-2892). The TBP distillation may be used for all fractions up to a maximum cut point of about 350°C atmospheric equivalent temperature (AET), but a low residence time in the still (or reduced pressure) is needed to minimize cracking. 

Generally, the preformed pyrrylmagnesium halide (4) is refluxed in ether with an alkyl halide, the acid-soluble isopyrrole mixture being readily separated from 1//-pyrroles by extraction. As described in the earliest reports of this reaction,10,13-15 products were isolated by fractional distillation and characterized as picrates, although the authors were generally... 

The chemical action of petroleum products on organisms depends on their chemical composition, which is in turn dependent on the type of petroleum, on the method of its treatment, on the distillation fraction and also on any additives. Petroleum itself contains about 100 different chemical compounds. They are characterized by different solubilities — benzene derivatives are water-soluble up to a concentration of approximately 100 mg 1, naphthalenes up to about 30 mg 1 and hydrocarbons with a higher formula mass are water-insoluble. The solubility increases the hazardous character of toxic substances. In general, petroleum products are only slowly degraded biologically and it is highly probable that the most toxic substances are decomposed most slowly and the products of their degradation can be even more harmful than the initial substances [4]. 

The ebullioscope of von Weber, shown in Fig. 32, operates in a similar manner. With this apparatus vapour pressure curves in the range of 10 to 760 mm Hg can be determined, whilst it can also be employed for other purposes, for instance for the calibration of thermometers, ebullioscopic measurements, the determination of vapour-liquid equilibria and the characterization of distillate fractions, such as those from petroleum and tar [33]. The apparatus consists of a vertical boiling tube A of 34 mm I.D. and 500 mm length. At its lower end the liquid is heated by an electric soldering iron element B of variable output, which is contained in a well C, the outer... 

Morgan, T.J., George, A., Alvarez, R, Millan, M., Herod, A.A., Kandiyoti, R. (2008) Characterization of molecular mass ranges of two coal tar distillate fractions (creosote and anthracene oils) and aromatic standards by LD-MS, GC-MS, probe-MS size exclusion chromatography. Energy Fuels, 22, 3275-3292. 

Ben Franklin is credited with the saying, Waste not want not. I don t think that he was referring to chemical waste but chemical waste is a major factor in scale-up. In the laboratory, waste from filtrates, unused distillation fractions, etcetera is of inconsequential quantity but as the scale increases, it can mean the success or failure of a project. In the laboratory, reactions are often run in dilute solutions. On a larger scale, to minimize waste and to be able to make more material, reactions are commonly much more concentrated sometimes they are run without solvent When a solvent is used, it is best if it can be recycled. If the solvent must be disposed of, it adds to the cost and is not as environmentally friendly. When there is less solvent to act as a heat sink, heats of reaction become more pronounced. Lacking other controls, an exothermic reaction run at 20% concentration will have a much greater temperature rise than one run at 2%. The characterization of the waste is also important. Whenever possible the waste should not be contaminated with highly toxic or environmentally unfriendly chemicals. 

Finally, it should be mentioned that Braun and Sobecki reported in 1911 [95] about the preparation of oligoalkanes. They extended the Grignard reaction to a,(o-dibromoalkanes. Starting out from 1,5-dibromopentane, decane, pentadecane and eicosane were isolated by fractionated distillation and characterized by elemental analyses and cryoscopy in benzene. The analogous dimer were obtained from 1,7-dibromoheptane and 1,10-dibromodecane. Twenty years later Carothers et al. [96] replaced magnesium by sodium and isolated pure alkanes up to heptakontane. 

To extend the applicability of the characterization factor to the complex mixtures of hydrocarbons found in petroleum fractions, it was necessary to introduce the concept of a mean average boiling point temperature to a petroleum cut. This is calculated from the distillation curves, either ASTM or TBP. The volume average boiling point (VABP) is derived from the cut point temperatures for 10, 20, 50, 80 or 90% for the sample in question. In the above formula, VABP replaces the boiling point for the pure component. 

It is common that a mixture of hydrocarbons whose boiling points are far enough apart petroleum cut) is characterized by a distillation curve and an average standard specific gravity. It is then necessary to calculate the standard specific gravity of each fraction composing the cut by using the relation below [4.8] ... 

Crude oil is generally characterized by a TBP analysis whose results are expressed as temperatures equivalent to atmospheric pressure as a function of the fraction of volume and weight distilled... 

FIGURE 2 11 Distillation of crude oil yields a series of volatile fractions having the names indicated along wih a nonvolatile residue The number of carbon atoms that characterize the hydrocarbons in each frac tion IS approximate... 

Rerunning operations are characterized by large volumes of distillate products and relatively small residue yields. Frequently, the product is withdrawn as a sidestream with undesirable light fractions passing overhead and polymers being withdrawn from the bottom of the tower. Lube rerun stills usually have several sidestreams which permit close control of flash point and viscosity while producing a wide range of stocks. 

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