Selective extraction hydrocarbons

Sulfur dioxide acts as a dienophile ia the Diels-Alder reaction with many dienes (253,254) and this reaction is conducted on a commercial scale with butadiene. The initial adduct, sulfolene [77-79-2] is hydrogenated to a solvent, sulfolane [126-33-0] which is useful for selective extraction of aromatic hydrocarbons from... 

Another sulfur dioxide appHcation in oil refining is as a selective extraction solvent in the Edeleanu process (323), wherein aromatic components are extracted from a kerosene stream by sulfur dioxide, leaving a purified stream of saturated aHphatic hydrocarbons which are relatively insoluble in sulfur dioxide. Sulfur dioxide acts as a cocatalyst or catalyst modifier in certain processes for oxidation of o-xylene or naphthalene to phthaHc anhydride (324,325). 

A gas processing plant selectively extracts ethylene and ethane from an incoming natural gas mixture stream. These two light hydrocarbons are absorbed in a heavy gasoline type absorber oil, and then stripped with open steam in an open tower. The system data are (see Figure 8-41) ... 

Parex (1) [Para extraction] A version of the Sorbex process, for selectively extracting p-xylene from mixtures of xylene isomers, ethylbenzene, and aliphatic hydrocarbons. The feedstock is usually a C8 stream from a catalytic reformer, mixed with a xylene stream from a xylene isomerization unit. The process is operated at 177°C the desorbent is usually p-diethylbenzene. The first commercial plant began operation in Germany in 1971 by 1992, 453 plants had been licensed worldwide. Not to be confused with Parex (2). 

Karasek et al. [1] determined hydrocarbons in benzene water extracts (pH7) of soil and in incinerator or fly ash by a variety of techniques including gas chromatography with flame ionization, electron capture and mass spectrometric detectors. Benzene water extractants were adjusted to pH4, 7 and 10 before the extraction in order to selectively extract various types of acidic and basic organic compounds in addition to hydrocarbons. 

It is possible that the photoionization detector (1) may not be completely selective for aromatics and can lead to an overestimate of the more mobile and toxic aromatic content and (2) the results from the two analyses, purge-able and extractable hydrocarbons, can overlap in carbon number and cannot simply be added together to get a total concentration of the total petroleum hydrocarbons. 

G.l.c. papers of interest include the classification of 22 acyclic monoterpenoid alcohols according to retention indexes, resolution of cyclic ketones [e.g. ( )-menthone, ( )-isomenthone] as diethyl (+)-tartrate acetals, and the use of lanthanide shift reagents to resolve non-terpenoid racemic epoxides.The occurrence and prevention of monoterpenoid hydrocarbon isomerization during silica gel chromatography has been examined and the separation of monoterpenoids and sesquiterpenoids by gel permeation chromatography is reported. Monoterpenoid hydrocarbons have been selectively extracted from essential oils using dimethylsilicone. ... 

The Purex process is used for almost all fuel reprocessing today. Irradiated UO2 fuel is dissolved in HNO3 with the uranium being oxidized to U02(N03)2 and the plutonium oxidized to Pu(NC>3)4. A solution of TBP in a high-boiling hydrocarbon, such as n-dodecane, is used to selectively extract the hexavalent U02(N03)2 and the tetravalent Pu(NC>3)4 from the other actinides and fission products in the aqueous phase. The overall reactions are... 

While the above details provide a general procedure for handling mixtures of acidic, basic and neutral components, other selective extraction reagents may be utilised in certain special instances. For example, cold concentrated sulphuric acid will remove unsaturated hydrocarbons (alkenes and alkynes) present in... 

An example of the difference of the solvent extracts from the bulk material comes from a series of studies on the exhaustive extraction of coal by boiling pyridine and fractionation of the regenerated soluble solids by sequential selective extraction schemes (Berkowitz, 1979). Subsequent analyses showed that the petroleum ether-soluble material was mostly composed of hydrocarbons (e.g., paraffins, naphthenes, and terpenes), while the ether-soluble, acetone-soluble, and acetone-insoluble fractions were resinlike substances with 80 to 89% carbon and 8 to 10% hydrogen. Indeed, this and later work (Vahrman, 1970) led to the concept that coal is a two-component or two-phase system (Derbyshire et al., 1991 Yun et al., 1991). 

Bouzige, M., V. Pichon, and M.C. Hennion. 1998. On-line coupling of immunosorbent and liquid chromatographic analysis for the selective extraction and determination of polycychc aromatic hydrocarbons in water samples at the ng F1 level. J. Chromatogr. A 823 197-210. 

Table II. Comparison of Selected Oxygenated Hydrocarbon Compounds in Steam Distilled and LCO2 Extracted Ginger Oil...

Description Hydrocarbon feed is preheated with hot circulating solvent and fed at a midpoint into the extractive distillation column (EDC). Lean solvent is fed at an upper point to selectively extract the aromatics into the column bottoms in a vapor/liquid distillation operation. Nonaromatic hydrocarbons exit the column top and pass through a condenser. A portion of the overhead stream is returned to the column top as reflux to wash out any entrained solvent. The balance of the overhead stream is the raffinate product, requiring no further treatment. 

GT-Styrene Recovery A process for recovering styrene from hydrocarbon fractions obtained by the steam cracking of petroleum. It uses extractive distillation with a proprietary selective extractant. Developed by GTC Technology (formerly Glitsch Technology Corporation) and planned for installation at a Chinese oil refinery in 2007. 

Selective extraction was used to operationally determine the quantitative and qualitative distributions of PCB 8 and saturated hydrocarbons among free lipid (FL), humic acid (HA), and humin (HU) fractions of four contaminated estuarine sediments. In all samples, over 90% of the total sedimentary PCB s and hydrocarbons were extracted with FL fractions. Bound (HA and HD) and free assemblages of these compounds may have derived from different sources. Two polar, chlorinated pollutants also detected In this study, hexachlorophene (HCP) and pentachlorophenol (PCP), were proportionately more concentrated In bound fractions than the non-polar compounds HCP was detected only In HA fractions and was probably chemically hound to refractory organic matter. Selective extraction Is a promising technique for Investigating strongly bound polar pollutants, such as HCP, which apparently are not recovered by conventional solvent extraction. 

The objective of this study was to determine, by selective extraction, whether or not non-polar, non-lonlc pollutants (e.g., PCB s and petroleum hydrocarbons) can become bound" In natural sediments, and, If so, whether their qualitative distributions provide Information about the Incorporation process. 

Liquid membrane systems were first introduced in 1968 (34), and since then they have been evaluated for various chemical and biochemical applications (35). Some of the applications include the selective extraction of hydrocarbons (36), the recovery of rare earths from process streams (37), the extraction of organic contaminants like phenol from water streams (38), and amino acid recovery (39). 

On a different note, anisotropic molecules, once extracted fully or partly into the membrane, become selectively oriented. By itself, the inside of the membrane is a highly anisotropic, hairbrush-like, lipophilic solvent. Any anisotropic lipophilic molecule selectively extracted into the membrane must therefore automatically become oriented to avoid the unfavorable energetics of disrupting this ordered state. Indeed, it has been shown experimentally (by specific labeling with a transmembrane photosensitive probe) that cholesterol is oriented perpendicularly to the membrane in closed vesicles (Nakatani et al., 1996). By contrast, the linear hydrocarbon p-carotene has been shown (by linear dichroism spectroscopy on flat bilayer stacks) to lie parallel to the surface (Norden... 

The present dependence of both Murphy and Johannson s methods on particular lots of petroleum ether is, however, a weakness and unnecessary. Thus, the property most probably determining the suitability of particular lots of petroleum ether for this selective extraction is either the proportion of aromatic hydrocarbons, and/or the proportion of longer chain or cyclic aliphatic hydrocarbons. It would probably be easy and very valuable to compare suitable and unsuitable batches of solvent by GLC (one of its most valuable and appropriate spheres of application ) and use the results to formulate a synthetic mixture of pentane, cyclohexane, and toluene or benzene for the extractant in this method. This would achieve a standardization enabling other laboratories to be far more confident of success with this method. 

Determination, offline GC-FID or FPD-P recoveries (1) >95% of hydrocarbons (2) quantitative extraction of phosphonates (3) phosphonic acids global recoveries are close to 80%, a loss of about 20% occurring during the derivatization process successive implementation of three extraction steps giving a selective extraction method... 

Chaudot, X., Tambute, A., and Caude, M., Selective extraction of hydrocarbons, phosphonates and phosphonic acids from soils by successive SF and pressurized liquid extractions, J. Chromatogr. A, 866, 231-240, 2000. 

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