Extraction boiling-solvent

Ambient-Temperature Extraction of Hydrocarbons From Marine Sediment-Comparison with Boiling-Solvent Extractions... 

For extraction purposes, a Soxhlet apparatus (Fig. 23(H)) can be inserted between a flask of boiling solvent and the reflux condenser A above. This apparatus is similar in design to that shown in Fig. 19, p. 3b in the type shown in Fig. 23(H) the hot extract continuously overflows through the side- tube into the boiling solvent below, but the syphon type shown in Fig. 19 is also available. 

The patent Hterature indicates that the AUiedSignal process uses lower boiling solvents such as chlorofluorocarbons as the cooling/extraction baths (16), whereas the processes of Stamicarbon indicate the use of decalin solvent followed by cooling and slow removal of the decalin in successively hotter chambers while stretching (17). 

Another solvent extraction scheme uses the mixed anhydrous chlorides from a chlorination process as the feed (28). The chlorides, which are mostly of niobium, tantalum, and iron, are dissolved in an organic phase and are extracted with 12 Ai hydrochloric acid. The best separation occurs from a mixture of MIBK and diisobutyl ketone (DIBK). The tantalum transfers to the hydrochloric acid leaving the niobium and iron, the DIBK enhancing the separation factor in the organic phase. Niobium and iron are stripped with hot 14—20 wt % H2SO4 which is boiled to precipitate niobic acid, leaving the iron in solution. 

Extraction and Extractive Distillation. The choice of an extraction or extractive distillation solvent depends upon its boiling point, polarity, thermal stabiUty, selectivity, aromatics capacity, and upon the feed aromatic content (see Extraction). Capacity, defined as the quantity of material that is extracted from the feed by a given quantity of solvent, must be balanced against selectivity, defined as the degree to which the solvent extracts the aromatics in the feed in preference to paraffins and other materials. Most high capacity solvents have low selectivity. The ultimate choice of solvent is deterrnined by economics. The most important extraction processes use either sulfolane or glycols as the polar extraction solvent. 

Extractive distillation, using similar solvents to those used in extraction, may be employed to recover aromatics from reformates which have been prefractionated to a narrow boiling range. Extractive distillation is also used to recover a mixed ben2ene—toluene stream from which high quaUty benzene can be produced by postfractionation in this case, the toluene product is less pure, but is stiU acceptable as a feedstock for dealkylation or gasoline blending. Extractive distillation processes for aromatics recovery include those Hsted in Table 4. 

As already noted (p. 1073), the platinum metals are all isolated from concentrates obtained as anode slimes or converter matte. In the classical process, after ruthenium and osmium have been removed, excess oxidants are removed by boiling, iridium is precipitated as (NH4)2lrCl6 and rhodium as [Rh(NH3)5Cl]Cl2. In alternative solvent extraction processes (p. 1147) [IrClg] " is extracted in organic amines leaving rhodium in the aqueous phase to be precipitated, again, as [Rh(NH3)5Cl]Cl2. In all cases ignition in H2... 

Finally, the extraction of solid or semisolid masses into solvents can be carried out by use of a Soxhlet extractor (Fig. A3.1 lb). The. .ample is placed in a porous cup in the extractor. The boiling solvent condenses into the cup and accumulates until a siphon column is established in the adjacent tube. Then the saturated solvent returns to the boiling flask and fresh solvent distills again, repeating the process. 

The first step for the determination of PAHs is removal from the matrix by solvent extraction, which preferably is performed with boiling toluene or benzene (hot solvent extraction by refluxing see Jacob and Grimmer 1994), although other solvents (e.g. tol-uene/acetone, acetone, and dichloromethane) and other extraction procedures (ultrasonic treatment, Soxhlet extraction, and accelerated solvent extraction) can also be applied. 

Lussier [71] has given an overview of Uniroyal Chemical s approach to the analysis of compounded elastomers (Scheme 2.2). Uncured compounds are first extracted with ethanol to remove oils for subsequent analysis, whereas cured compounds are best extracted with ETA (ethanol/toluene azeotrope). Uncured compounds are then dissolved in a low-boiling solvent (chloroform, toluene), and filler and CB are removed by filtration. When the compound is cured, extended treatment in o-dichlorobenzene (ODCB) (b.p. 180 °C) will usually suffice to dissolve enough polymer to allow its separation from filler and CB via hot filtration. Polymer identification was based on IR spectroscopy (key role), CB analysis followed ASTM D 297, filler analysis (after direct ashing at 550-600 °C in air) by means of IR, AAS and XRD. Antioxidant analysis proceeded by IR examination of the nonpolymer ethanol or ETA organic extracts. For unknown AO systems (preparative) TLC was used with IR, NMR or MS identification. Alternatively GC-MS was applied directly to the preparative TLC eluent. 

The classical methods of solvent extraction of polymers can be conveniently divided into those for which heat is required (Soxhlet/Soxtec ), and those methods for which no heat is added, but which utilise some form of agitation, i.e. shaking or sonication (Table 3.3). Other LSE procedures consist in soaking the polymer in boiling solvents [84,85] and cold LSE [80,86]. These methods are also time-consuming, use large amounts of solvents which are scheduled to be restricted in the future, and exhibit other limitations when analytes are present in small quantities, where they may actually be lost in concentration steps following extraction. Many norms are still based on such standard procedures [87,88],... 

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