Distillation, fractional INDEX

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. 

This is a set of equations applicable to z = 1,..., C, where C is the total number of components. Equation 12.17 is one form of the Fenske equation (Fenske, 1932) for a total reflux distillation column. The number of stages A, is the minimum required to achieve the separation corresponding to component flow rates and and bottoms rate B. In this equation, N, the number of stages, is also known as the fractionation index. 

The VGC is a measure of petroleum composition that connects two physical properties—specific gravity and viscosity—for distillation fractions. It was developed by Hill and Coates in 19286 to be an index of the paraffinic or naphthenic character. The objective was to fill in the gap between clearly paraffinic and clearly naphthenic samples. It is still reported for base stocks and ranges from approximately 0.78 (paraffinic base stocks) to 1.0 (highly aromatic base stocks) and its value provides some guidance for the solvency properties of the oil. Like the results of the n-d-M method, the VGC is usually reported for naphthenic products, but not for paraffinic ones. 

Table 4-132 Index numbers from thermogravimetry of orginal samples (feed) and heavy oils. Evaporation start temperatures and distillable fraction. 

In the following set of experiments, we wiU examine the applications of a variety of distillation techniques to the purification of liquid mixtures. In Experiments [3A] and [3B] you will conduct simple distillations. In Experiment [3A] a volatile liquid component is separated from a nonvolatile solid. Experiment [3B] illustrates the use of the Hickman still in the separation of hexane and toluene, which have boiling points 42 °C apart. The composition of the fractions is analyzed by refractive index and boiling point. Experiments [3C] and [3D] introduce the use of micro spinning-band distillation columns for the separation of cyclohexane (bp 80.7 °C) and 2-methylpentane (bp 60.3 °Q. The composition of the distillate fractions are determined by gas chromatography. The number of theoretical plates is determined for the spinning-band column used. In Experiment [3D] you wiU be introduced to one of the simplest yet most efficient and powerful distillation techniques for the separation of liquid mixtures at the semimicroscale level, the Hickman-Hinkle stiU. 

Bromine (128 g., 0.80 mole) is added dropwise to the well-stirred mixture over a period of 40 minutes (Note 4). After all the bromine has been added, the molten mixture is stirred at 80-85° on a steam bath for 1 hour, or until it solidifies if that happens first (Note 5). The complex is added in portions to a well-stirred mixture of 1.3 1. of cracked ice and 100 ml. of concentrated hydrochloric acid in a 2-1. beaker (Note 6). Part of the cold aqueous layer is added to the reaction flask to decompose whatever part of the reaction mixture remains there, and the resulting mixture is added to the beaker. The dark oil that settles out is extracted from the mixture with four 150-ml. portions of ether. The extracts are combined, washed consecutively with 100 ml. of water and 100 ml. of 5% aqueous sodium bicarbonate solution, dried with anhydrous sodium sulfate, and transferred to a short-necked distillation flask. The ether is removed by distillation at atmospheric pressure, and crude 3-bromo-acetophenone is stripped from a few grams of heavy dark residue by distillation at reduced pressure. The colorless distillate is carefully fractionated in a column 20 cm. long and 1.5 cm. in diameter that is filled with Carborundum or Heli-Pak filling. 4 hc combined middle fractions of constant refractive index are taken as 3-l)romoaccto])lu iu)nc weight, 94 -100 g. (70-75%) l).p. 75 76°/0.5 mm. tif 1.57,38 1.5742 m.]). 7 8° (Notes 7 and 8). 

In 1899 Thoms isolated an alcohol from Peru balsam oil, which he termed peruviol. This body was stated to have powerful antiseptic properties, but has not been further investigated until Schimmel Co. took up the subject. The oil after saponification was fractionated, and after benzyl alcohol had distilled over, a light oil with characteristic balsamic odour passed over. It boiled at 125° to 127° at 4 mm., and had a specific gravity 0 8987, optical rotation -1- 12° 22, and refractive index 1-48982. This body appeared to be identical with Hesse s nerolidol, whilst in physical and chemical properties it closely resembles peruviol. The characters of the various preparations were as follows —... 

The specific gravity, refractive index, and specific rotation given above are those recorded by Paolini and Divizia and are probably accurate since the a-santalol was prepared by regeneration from its strychnine phthalate. The values recorded for commercial santalol, prepared by fractional distillation, are as follows, and are the average values for the mixed santalols as they occur in sandalwood oil... 

The preduct of condensation remaining in the distilling apparatus is purified by the fractional distillation in vacuo. Under a pressure of 12 mm. a liquid distils off at a temperature of from 143° to 145° C. This preduct of condensation of citral with acetone, which I term Pseudo-ionone, is a ketone readily decomposable by the action of alkalis. Its formula is CigHjoG, its index of refraction nT> = 1-527, and its specific weight 0-904. 

Petroleum or mineral oil (kerosene, etc.) are less soluble in alcohol than most oils. They have a low specific gravity and refractive index, and are not saponified by alcoholic potash. The lower boiling fractions can usually be detected by their odour, and the higher boiling fractions remain in the residue on fractional distillation. They are unaffected by fuming nitric acid. 

Y Picoline. Commercially pure y-picoline contains )S-picoline and 2 6-lutidine and sometimes traces of non-basic impurities (aromatic hydrocarbons) which cannot be separated by fractionation. The non-basic impurities are removed by steam distillation of the base in dilute hydrochloric or sulphuric acid solution (for details, see under a Picoline). The impure y-picoline is converted into the zinc chloride complexes of the component bases the 2 6-lutidine - ZnClj complex is the least stable and upon steam distillation of the mixture of addition compounds suspended in water, 2 6-lutidine passes over flrst. The complete separation of the 2 6-lutidine may be detected by a determination of the density and the refractive index of the dry recovered base at varioiu stages of the steam distillation. The physical properties are —... 

Geddes, R. L. (1958) AIChE Jl 4, 389. General index of fractional distillation power for hydrocarbon mixtures. 

Suppose you fractionated that liquid of composition A, collected a few drops of the condensed vapor at the top of the column, analyzed it by taking its refractive index, and found that this liquid had a composition corresponding to point J on our diagram. You would follow the same path as before (B-C-D, one distillation D-G-H, another distillation) and find that composition J falls a bit short of the full cycle for distillation 2. 

In a hood, to a well-stirred dispersion of 62 gm (1.35 moles) of methyl-hydrazine, 175 ml of chlorobenzene, and 20 gm of powdered, anhydrous sodium sulfate is added dropwise, with cooling, 61 gm (0.663 mole) of freshly distilled l-chloro-2-propanone. After the addition has been completed, the reaction mixture is stirred for 1 hr. The moist sodium sulfate is separated by filtration and the filtrate is distilled. The fraction boiling between 60°C and 64°C is collected as product, yield 16.8 gm (31 %) of a yellow liquid. On redistillation the boiling point is raised slightly to 61°-64°C, index 1.4300. 

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