Aromatics extraction

In the manufacture of base oils, one of the refining operations is to extract with the aid of an appropriate solvent (furfural most often) the most aromatic fractions and the polar components. When free of solvent, the extracted aromatic fraction can eventually be refined, particularly to remove color or to thicken it, or still further, to fractionate it. The term, aromatic extract is used in every case. 

Lubricating Oil Extraction. Aromatics are removed from lubricating oils to improve viscosity and chemical stabihty (see Lubrication and lubricants). The solvents used are furfural, phenol, and Hquid sulfur dioxide. The latter two solvents are undesirable owing to concerns over toxicity and the environment and most newer plants are adopting furfural processes (see Furan derivatives). A useful comparison of the various processes is available (219). 

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). 

The sulfolane process is a versatile extractant for producing high purity BTX aromatics (benzene, toluene, and xylenes). It also extracts aromatics from kerosines to produce low-aromatic jet fuels. 

Sulfolane is a water-soluble biodegradable and highly polar compound valued for its solvent properties. Approximately 20 million pounds of sulfolane are consumed annually in applications that include delignification of wood, polymerization and fiber spinning, and electroplating bathes.It is a solvent for selectively extracting aromatics from reformates and coke oven products. 

Dipicryl-l,3,4-oxadiazole has been described as an initiating explosive, 2,5-dimethyl-l,3,4-oxadiazole has been used to extract aromatic hydrocarbons from mixtures with alkanes. The use of 4,4 -carbonyl-bis(2-phenyl-5-oxo-l,3,4-oxadiazole) as a blowing agent for foaming thermoplastic compositions (e.g., polycarbonates) has been described < 1996CHEC-II(4)268>. 

Arosorb A process for extracting aromatic hydrocarbons from refinery streams using a solid adsorbent, either silca gel or achvated alumina. Developed by the Sun Oil Company in 1951. California Research Corporation developed a similar process. 

Formex A process for extracting aromatic hydrocarbons from petroleum reformate, using N-formyl morpholine at 40°C. Developed by SNAM-Progetti. 

MERIFINING A process for extracting aromatic mercaptans and organic acids from cracked hydrocarbon fractions by aqueous alkali, using a bundle of hollow fibers. Developed by the Merichem Company, Houston, TX. Twelve units were operating as of 1991. 

The process equipment consists mainly of two extraction columns with pulsating trays and four distillation columns according to Fig. 10.4 [7]. The feed, with a high content of aromatics, is pumped to the middle of the first extraction column where the aromatics are extracted with the solvent SI (tetraethylene glycol). In the lower part, the extracted aromatics are washed with S2 (dodecane). The outgoing raffinate phase R1 (containing aliphatics,... 

Solvent extraction with methanolic hydrolysis of the soil has been used to extract aromatic hydrocarbons. Significantly higher quantities of organics were recovered compared to the use of only an organic solvent extraction [41 ]. 

Silica gel is an adsorbent for aromatics and has found use in extracting aromatics from refinery streams. Silica gel is manufactured amorphous silica that is extremely porous and has the property of selectively removing and holding certain chemical compounds from mixtures. For example, silica gel selectively removes aromatics from a petroleum fraction, and after the nonaromatic portion of the fraction is drained from the silica gel, the adsorbed aromatics are washed from the silica gel by a stripper (or desorbent). Depending on the kind of feedstock, xylene, kerosene, or pentane may be used as the desorbent. 

A major portion of the world s BTX is made by naphtha reforming. The technology and economics of this route is well reported in petroleum refinery handbooks. Often this route uses extractive distillation to extract aromatics prior to distillation. Reforming operations are often integrated with ethylene cracking operations to maximise benzene production from reformate and pyrolysis gasoline. ... 

Table 6 Carbon stable isotope compositions of solvent extractable aromatic compounds in carbonaceous...

Figure 3 Carbon stable-isotope compositions of solvent extractable aromatic and PAHs plotted against carbon number from the Murchison and Asuka-881458 CM2 carhonaceous chondrites (sources Yuen et al., 1984 Gilmour and Pillinger, 1994 Sephton et al., 1998 ...

Air (aromatics) Collect air samples on charcoal tube extract aromatics with carbon disulfide and H2SO4... 

The list of acids isolated from aqueous extracts of the shale is given for comparison. These acids were identified in the water extracts from raw Aleksinac shale as well as from bitumen-free shale, i.e., before and after the extraction of the bitumen (21). Mass spectrometric identifications of various isomers were based on comparison of the relative intensities of molecular ions and their corresponding base peak ions. The compounds extracted with water from the bitumen-free shale were very similar to the compounds isolated from the raw shale. The findings suggest that the acids were present as salts in both instances. In the aqueous extracts aromatic and dicarboxylic acids predominated, while aliphatic monocarboxylic acids were absent. Comparison of the chemical nature of water extractable acids with the acids obtained from the bitumen of the same shale showed a similarity in the type and range of aromatic and saturated unbranched dicarboxylic acids. 

Often, the extraction is followed by extractive distillation. In these cases the solvent must not only preferentially extract aromatics, it must also lower the volatility of the aromatics so that they can be more easily separated from the solvent by distillation. 

In addition to extraction from solids, supercritical fluids can be used to extract aromatic molecules from liquids. Senorans et al. have utilized carbon dioxide to extract high-quality brandy aroma using a countercurrent supercritical fluid extractor. The aroma quality is influenced by the extraction conditions. Medina and Martinez studied alcohol removal from beverages using supercritical carbon dioxide, to produce beverages with low-alcohol content but sufficient flavor, because of three key benefits 1) water and salts are not appreciably removed by the carbon dioxide 2) proteins and carbohydrates are not extracted or denatured and 3) there is a good control in the aroma recovery. The alcohol removal efficiency increases with the extraction pressure raffinate alcohol concentration can be reduced up to 3 wt.% at 250 bar and 40°C, from 6.2 wt.% in the feed. " ... 

CineUi. E, Noe, S. Paret, G Extract aromatics with FM, Hydrocarbon Processing, 51 (4) 141-14411972V Danulat, H. F Markwort, H Lorp process balances BTX yield", Europ. Chat, News. Large Plant Survey... 

Aromatic liquids Beverage extract (concentrate) Camphor oil, 3.3 Extract, aromatic or flavouring Extracts, aromatic, liquid, 3, 3.2,3.3 Extracts, flavouring, liquid,... 

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