Distillation with direct solvent extraction

Direct solvent extraction is the most widely used oil-recovery method for soybeans, but it also requires considerable capital and large scale to compete. In actual practice, solvent extraction is used to crush over 98% of the soybean processed in the United States. Process flow diagrams are shown in Figures 3 and 4. Most soybean solvent-extraction plants process more than 2,500 MT/day (Figure 5), and some are capable of processing as much as 5,000 MT/day (especially newly constructed plants in Brazil). Direct-solvent-extraction plants smaller than 1,000 MT/day have difficulty competing in the United States. At various times, soybeans have been extracted commercially with petroleum distillate fractions that resemble gasoline, acetone, carbon disulfide, ethanol, trichloroethylene, and even water. 

RB-HVP was subjected to direct solvent extraction followed by high vacuum distillation (77). Ten g of PB-HVP was hydrated with 100 mL of odor-free distilled-deionized water. The mixture was spiked with 25 pL of an internal standard solution (5.0 pg/pL of 2-ethyl butanoic acid 3.3 pg/pL of 4-tert-amyphenol and 4.3 pg/pL of 2-methyl-3-heptanone in methanol). The solution was extracted with ether (2 x 50 mL). Extractions were conducted for duplicate... 

Description A typical SED unit mainly consists of an extractive distillation column and a solvent recovery column. The hydrocarbon feed is separated into non-aromatics and aromatics products through extractive distillation with the solvent. For the benzene-recovery case, benzene is directly produced from the SED unit. For the benzene and toluene recovery case, pure benzene and pure toluene are produced from the aromatics product of the SED unit through downstream fractionation. 

Peak numbers correspond to those in Figures i and 2 and Table II. RI, retention index. Average relative conccniratiop t. standard deviation (n=I2). SDE, simultaneous steam distillation-solvent extraction. DE, direct solvent extraction. Compound tentatively identified by comparing its mass spectrum to Wiley 13SK mass spectral database, Compound not previously identified in saffron. Compound positively identified as described in materials and methods. V trace. Compound tentatively identified by comparing its mass spectrum with published literature (II). nd. not detected. I.S., internal standard, N/A, not available, peak could not be resolved. 

One of the simplest and most efficient approaches for aroma isolation is direct solvent extraction. The major limitation of this method is that it is most useful on foods that do not contain any lipids. If the food contains lipids, the lipids will also be extracted along with the aroma constituents, and they must be separated from each other prior to further analysis. Aroma constituents can be separated from fat-containing solvent extracts via techniques such as molecular distillation, steam distillation, and dynamic headspace. 

Other Organic Processes. Solvent extraction has found appHcation in the coal-tar industry for many years, as for example in the recovery of phenols from coal-tar distillates by washing with caustic soda solution. Solvent extraction of fatty and resimic acid from tall oil has been reported (250). Dissociation extraction is used to separate y -cresol fromT -cresol (251) and 2,4-x5lenol from 2,5-x5lenol (252). Solvent extraction can play a role in the direct manufacture of chemicals from coal (253) (see Eeedstocks, coal chemicals). 

Natural Products. Various methods have been and continue to be employed to obtain useful materials from various parts of plants. Essences from plants are obtained by distillation (often with steam), direct expression (pressing), collection of exudates, enfleurage (extraction with fats or oils), and solvent extraction. Solvents used include typical chemical solvents such as alcohols and hydrocarbons. Liquid (supercritical) carbon dioxide has come into commercial use in the 1990s as an extractant to produce perfume materials. The principal forms of natural perfume ingredients are defined as follows the methods used to prepare them are described in somewhat general terms because they vary for each product and suppHer. This is a part of the industry that is governed as much by art as by science. 

Allelopathic test materials and controls. Some 2.5 mL of aqueous or organic extracts were required for thorough saturation. Water-soluble or partially water-soluble extracts were appUed directly to the filter paper. Distilled water controls were used. With organic solvent-soluble extracts, the solution was applied to the filter paper and allowed to dry, then distilled water was added to support germination. Controls having pure solvent applied were similarly allowed to dry before the distilled water was added, ( antification of the amount of allelopathic material applied to each sample... 

Essences of pink and white fresh guava obtained by direct extraction of flesh juices with dichloromethane revealed that the total amount of Cs aldehydes, alcohols, and acids comprised 20 and 44% of the essence of fresh white and pink guavas, respectively [49]. The flavour of the Costa Rican guava has been described as sweet with strong fruity, woody-spicy, and floral notes [53]. One hundred and seventy-three volatile compounds were isolated by simultaneous steam distillation-solvent extraction. The terpenes and terpenic derivatives were found in this fruit in major concentrations and were strong contributors to tropical fruit notes (Fig. 8.1). The aliphatic esters contributed much to its typical flavour. 

Solid waste matriees Solvent extraction or direct injection (with azeotropic distillation) into capillary GC column GC/FID 9-21 pg/L (aqueous matrices) 0.08-0.20 mg/kg (solid matrices) Environmental Protection Agency (1996a) [Method 8015B]... 

Samples were eluted in the reverse direction by using the Milton-Roy pump with the pulse dampener removed. The eluant flow (50-75 mL/min at 200-300 lb/in.2) was monitored at 254 nm by using an Altex 153 detector with a biochemical flow cell. Elution with each solvent was continued until the detector response returned to base line. All columns were eluted with acetonitrile this solvent was preceded by 4.5 M NaCl/0.04 M HC1 and 0.04 M HC1 elutions on the MP-1 column and by 4.5 M NaCl and distilled water elutions on the MP-50 column. The aqueous column effluents were adjusted to pH 2 (MP-1) or pH 11 (MP-50) and then extracted three times with dichloromethane. The acetonitrile column effluents were saturated with NaCl to separate the water, which was extracted twice more with acetonitrile. Fifty percent aliquots of the processed organic solvents from each respective column were concentrated in Kudema-Danish evaporators to a final volume of about 10 mL (any remaining water was removed as the low-boiling azeotrope in the process) to give 25,000 1... 

Procedures for the determination of 11 elements in coal—Sb, As, Br, Cd, Cs, Ga, Hg, Rb, Se, U, and Zn—by neutron activation analysis with radiochemical separation are summarized. Separation techniques include direct combustion, distillation, precipitation, ion exchange, and solvent extraction. The evaluation of the radiochemical neutron activation analysis for the determination of mercury in coal used by the Bureau of Mines in its mercury round-robin program is discussed. Neutron activation analysis has played an important role in recent programs to evaluate and test analysis methods and to develop standards for trace elements in coal carried out by the National Bureau of Standards and the Environmental Protection Agency. 

Figure 14.5. Representation of solvent extraction behavior in terms of certain properties rather than direct compositions [Dunstan et aL, Sci. Pet., 1825-1855 (1938)]. (a) Behavior of a naphthenic distillate of VGC = 0.874 with nitrobenzene at 10°C. The viscosity-gravity constant is low for paraffins and high for naphthenes, (b) Behavior of a kerosene with 95% ethanol at 17°C. The aniline point is low for aromatics and naphthenes and high for paraffins, (c) Behavior of a dewaxed crude oil with liquid propane at 70°F, with composition expressed in terms of specific gravity.

The core technology used in the analysis of aroma chemicals is gas chromatography (GC) therefore, foods must be sampled so they can be introduced on to a GC column. For liquid samples it is possible to inject them into split, splitless, or on-column injectors directly. This is the preferred method for the analysis of synthetic aromas, essential oils, and aroma standards however, solid or dilute liquid samples need to be extracted, distilled, or gas-phase generated in order to obtain useful results. This unit begins with simple direct analysis of a synthetic flavor (see Basic Protocol 1) followed by the analysis of a dilute liquid sample by solvent extraction (see Basic Protocol 2). It ends with a protocol for determining retention indices (see Support Protocol). 

It is important to use rather pure acid esters for the resolution step. The hydrogen phthalates are usually solids that may be crystallized from petroleum ether, benzene, or acetic acid. Phthalic acid is the usual major impurity and may interfere with the crystallization of the ester. If it does, or if the ester is liquid, it is convenient to extract the crude product with chloroform or benzene, in which phthalic acid is nearly insoluble. Distillation of the solvent from the dried extract usually leaves the ester pure enough to crystallize or to use directly. 

Selective solvent extraction of volatiles will remove volatiles with very high yields although the extracts are always contaminated with non-volatile components. For example, acetonitrile extraction followed by co-extraction with pentane was used by Vemin (38). In our experiments the direct extraction of crushed crackers with Freon 113 or ethyl acetate contained too much residual lipid. Distillation of the solvent yielded a lipid concentrate low in aroma volatiles. Attempts to use gel filtration (Bio-Beads S-X12 from Bio-RAD) to remove the lipids but retain the odorous substances were also unsuccessful. 

Solvent extraction has found application for many years in the coal tar industry. Extraction of phenols from coal-tar distillates by washing with caustic soda solution can be considered such a process. In the isomer separation, a process for separation of m- and p-crcsol by dissociation extraction has been reported. Work is in progress in several parts of the world to use solvent extraction for the direct manufacture of chemicals from coal. Crude tall oil is a byproduct of pulp mills. It is refined by solvent extraction using propane or furfural. 

By the early part of the twentieth century, pure grades of volatile hydrocarbon solvents such as benzene and hexane became available through progress in petroleum-refining methods. They were found to be very useful for the extraction of fragrant plants and plant materials. If the plant material extracted is rich in waxes (as is generally the case with flowers, stems, and leaves), these are also taken up in the extract. After careful removal of the volatile solvent by distillation, a waxy concrete remains behind. This is then washed with alcohol to separate the fragrance materials, which are soluble in alcohol, from the insoluble waxes. An absolute is then produced by the removal of the alcohol by distillation, usually under reduced pressure. Certain plant materials that contain no water, such as resins or dried leaves and mosses, may be extracted directly with alcohol. The extracts obtained—often sticky, viscous, and resiny—are called resinoids. 

Distillation techniques, such as steam distillation, are typically carried out in a rotary evaporator after the sample has been solubilized in an organic solvent. The distillate is injected directly onto a suitable GC column. This method is used widely due to its simplicity and because components with high boiling points are recovered easily. High-vacuum distillation is used widely to isolate volatile components from solvent extracts. This procedure often requires an extraction step to remove water. 

Solvent extraction. The press cake emerging from a screw press still retains 3 to 15 percent of residual oil. More complete extraction is done by solvent extraction of the residues obtained from mechanical pressing. The greater efficiency obtained in the solvent extraction process encouraged the industry for direct application to oilseeds. In the United States and Europe, continuous extractor units are used in which fresh seed flakes are added continuously and are subjected to a counterflow of solvent by which intimate contact is achieved between the seeds and solvent. The common solvent for edible oil is commercial hexane or heptane, commonly known as petroleum ethers, boiling in the range of 146 to 156°F (63.3 to 68.9°C). After extraction, maximum solvent recovery is necessary for economical operation. The solvent is recovered by distillation and is reused. The extraction oil is mixed with prepress oil for refining. The extracted meals contain less than 1 percent of residual oil. 

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