Separating aromatic hydrocarbon from

Solv useful to separate aromatic hydrocarbons from their mixts)... 

The ability to bind the additional amount of aromatic hydrocarbons is also characteristic of complexes with other binary acid systems, for example, of the complexes A HF BFj. This property of ternary complexes can be used to separate aromatic hydrocarbons from saturated ones and to separate aromatic hydrocarbons differing in their basicity (for the use of complexes with HCl and AlCl, see > with HF and BF3 see ° )- References recording the formation of the ternary complexes A HY mMY and of their solvates for hydrocarbons of the benzene series are listed in Table 1. 

Nitromethane can be used in an extractive process to separate aromatic hydrocarbons from aliphatic hydrocarbons due to the lower solubility of the aliphatic fractions in nitromethane [3]. Nitroparaffins are used to separate lactic acid from fermentation beers [4], nitrocellulose from the nitrating solution [5], and plutonium (IV) from aqueous solutions [6]. Nitropropane is used to extract rosin from pine lumber at elevated temperatures [7]. Toluene can be separated from similar boiling-point aliphatic paraffins by azeotropic distillation with nitromethane [8]. Ethylbenzene forms an azeotrope with nitromethane which allows its separation from styrene through a distillation process. 

Sulfolane, another highly polar solvent, is used to separate aromatic hydrocarbons from aliphatic hydrocarbons [10]. The extraction process first developed by Shell Oil in 1959 and which is referred to as the Sulfolane process is used worldwide. The solvency of sulfolane for certain fatty acids and fatty acid esters is the basis for upgrading animal and vegetable fatty acids used in food products, paints, plastics, resins, and soaps. Aqueous solutions containing 30-70 wt% sulfolane are used to remove lignin from wood chips [11]. Sulfolane is used to remove acidic components like hydrogen sulfide and carbon dioxide from gas feed stocks. 

Extraction Solvent. Dimethyl sulfoxide is immiscible with alkanes but is a good solvent for most unsaturated and polar compounds. Thus, it can be used to separate olefins from paraffins (93). It is used in the Institute Fransais du Pntrole (IFF) process for extracting aromatic hydrocarbons from refinery streams (94). It is also used in the analytical procedure for determining polynuclear hydrocarbons in food additives (qv) of petroleum origin (95). 

Several solvent uses have been proposed. Dimethyl sulfate has been used as a solvent for the study of Lewis acid—aromatic hydrocarbon complexes (148). It also is effective as an extraction solvent to separate phosphoms haUde—hydrocarbon mixtures and aromatic hydrocarbons from aUphatics, and it acts as an electrolyte in electroplating iron (149—152). The toxicity of dimethyl sulfate precludes its use as a general-purpose solvent. 

Another application of SFC-GC was for the isolation of chrysene, a poly aromatic hydrocarbon, from a complex liquid hydrocarbon industrial sample (24). A 5 p.m octadecyl column (200 cm X 4.6 mm i.d.) was used for the preseparation, followed by GC analysis on an SE-54 column (25 m X 0.2 mm i.d., 0.33 p.m film thickness). The direct analysis of whole samples transferred from the supercritical fluid chromatograph and selective and multi-heart-cutting of a particular region as it elutes from the SFC system was demonstrated. The heart-cutting technique allows the possibility of separating a trace component from a complex mixture (Figure 12.21). 

Because process mixtures are complex, specialized detectors may substitute for separation efficiency. One specialized detector is the array amperometric detector, which allows selective detection of electrochemically active compounds.23 Electrochemical array detectors are discussed in greater detail in Chapter 5. Many pharmaceutical compounds are chiral, so a detector capable of determining optical purity would be extremely useful in monitoring synthetic reactions. A double-beam circular dichroism detector using a laser as the source was used for the selective detection of chiral cobalt compounds.24 The double-beam, single-source construction reduces the limitations of flicker noise. Chemiluminescence of an ozonized mixture was used as the principle for a sulfur-selective detector used to analyze pesticides, proteins, and blood thiols from rat plasma.25 Chemiluminescence using bis (2,4, 6-trichlorophenyl) oxalate was used for the selective detection of catalytically reduced nitrated polycyclic aromatic hydrocarbons from diesel exhaust.26... 

An alternative method for fractionating and purifying petroleum hydrocarbons prior to GC or HPLC separation has been developed (Theobald 1988). The method uses small, prepacked, silica or Cjg columns that offer the advantage of rapid separation (approximately 15 minutes for a run) good recovery of hydrocarbons (85% for the Cjg column and 92% for the silica column) reusability of the columns and for the silica column in particular, good separation of hydrocarbon from non-hydrocarbon matrices as may occur with environmental samples. Infrared analysis and ultraviolet spectroscopy were used to analyze the aromatic content in diesel fuels these methods are relatively inexpensive and faster than other available methods, such as mass spectrometry, supercritical fluid chromotography, and nuclear magnetic resonance (Bailey and Kohl 1991). 

Arce, A. et al.. Separation of aromatic hydrocarbons from alkanes using the ionic liquid l-ethyl-3-methylimidazolium bis (trifluoromethyl)sulfonyl amide. Green Ghem., 9, 70, 2007. 

Domarfska, U., Pobudkowska, A., and Krolikowski, M., Separation of aromatic hydrocarbons from alkanes using ammonium ionic liquid C2NTf2 at T = 298.15 K, Fluid Phase Equilib., 259,173,2007. 

Extractive distillation, that is, fractional distillation in the presence of a solvent, is used to recover aromatic hydrocarbons from, say, reformate fractions in the following manner. By means of preliminary distillation in a 65-tray prefractionator, a fraction containing a single aromatic can be separated from the reformate, and this aromatic concentrate is then pumped to an extraction distillation tower near the top, and aromatic concentrate enters near the bottom. A reboiler in the extractive distillation tower induces the aromatic concentrate to ascend the tower, where it contacts the descending solvent. 

Gmehling J, Krummen M (to Carl v. Ossietzky University Oldenburg), DE10154052 Separation of aromatic hydrocarbons from non-aromatic hydrocarbons, comprises using a selective solvent selected from liquid onium salts publication date 2003-07-10... 

The extraction of aromatic hydrocarbons (Fig. 5.5) from crude oil uses two sorbents in series, first a cyanopropyl column attached to a second silica column. In this procedure, aromatic hydrocarbons are sorbed on both the cyanopropyl sorbent and on the silica sorbent. The heteroatom hydrocarbons (containing nitrogen, oxygen, and sulfur) are trapped on the cyanopropyl sorbent and eluted as a separate fraction from the silica column. Because the major interaction of aromatic heterocyclic hydrocarbons is through hydrogen bonding to the surface of the sorbent, the cyanopropyl sorbent is easier to elute than a silica sorbent alone. For this reason, the cyanopropyl column is used before the silica column. The separation of hydrocarbons from crude oil is an example of normal-phase chromatography that has been performed for many years on silica gel prior to the introduction of SPE. 

SO.,"] < [MeSO.,"] [40]. These results were quite encouraging and suggested that these SLMs based on ILs could be used for the selective separation of the organic esters from the reaction mixture. SILMs can also be used for the separation of aromatic hydrocarbons from aliphatic hydrocarbons. In this context, the selective separation of benzene, toluene and p-xylene from n-heptane was achieved using SILMs based on [bmim ][PE "], [hmim+][PFg ], [omim+][PFg ] and [Et MeMoEtN [TfjN"] supported on a polyvinyhdene fluoride manbrane [9]. It was found that aromahc hydrocarbons were successfully transported through the membrane based on these ionic liquids, and the maximum selectivity to n-heptane was when benzene used in the aromatic permeation and [bmim+][PFg ] was taken in the hquid membrane phase. 

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