Fractions produced

Many valuable chemicals can be recovered from the volatile fractions produced in coke ovens. Eor many years coal tar was the primary source for chemicals such as naphthalene [91-20-3] anthracene [120-12-7] and other aromatic and heterocycHc hydrocarbons. The routes to production of important coal-tar derivatives are shown in Eigure 1. Much of the production of these chemicals, especially tar bases such as the pyridines and picolines, is based on synthesis from petroleum feedstocks. Nevertheless, a number of important materials continue to be derived from coal tar. 

Proof of the existence of benzene in the light oil derived from coal tar (8) first estabHshed coal tar and coal as chemical raw materials (see Eeedstocks, COAL chemicals). Soon thereafter the separation of coal-tar light oil into substantially pure fractions produced a number of the aromatic components now known to be present in significant quantities in petroleum-derived Hquid fuels. Indeed, these separation procedures were for the recovery of benzene—toluene—xylene (BTX) and related substances, ie, benzol or motor benzol, from coke-oven operations (8) (see BTX processing). 

Cmde petroleum is a mixture of compounds boiling at different temperatures that can be separated into a variety of different generic but often overlapping fractions (Table 1). The amounts of these fractions produced by distillation depend on the origin and properties of cmde petroleum (2). 

In the Sulser-MWB process the naphthalene fractions produced by the crystallisation process are stored in tanks and fed alternately into the crystalliser. The crystalliser contains around 1100 cooling tubes of 25-mm diameter, through which the naphthalene fraction passes downward in turbulent flow and pardy crystallises out on the tube walls. The residual melt is recycled and pumped into a storage tank at the end of the crystallisation process. The crystals that have been deposited on the tube walls are then pardy melted for further purification. Following the removal of the drained Hquid, the purified naphthalene is melted. Four to six crystallisation stages are required to obtain refined naphthalene with a crystallisation point of 80°C, depending on the quaHty of the feedstock. The yield is typically between 88 and 94%, depending on the concentration of the feedstock fraction. 

Phospho-L-threonine (L-threonine-O-phosphate) [1114-81-4] M 199.1, m 194 (dec), [a]p -7.37 (c 2.8, H2O) (pK as above). Dissolve in the minimum volume of H2O, add charcoal, stir for a few min, filter and apply onto a Dowex 50W (H" " form) then elute with 2N HCI. Evaporate the eluates under reduced pressure whereby the desired fraction produced crystals of the phosphate which can be recrystd from H2O-MeOH mixtures and the crystals are then dried in vacuo over P2O5 at 80 . [de Verdier Acta Chem Scand 7 196 7955.]... 

Fractionators produce two results only (1) stream splitting, with so many pounds going out one end and all other feed pounds going out the other and (2) component segregation toward one or the other of the product streams, characterized by the Fenske ratio ... 

The feed to a catalytic reformer is normally a heavy naphtha fraction produced from atmospheric distillation units. Naphtha from other sources such as those produced from cracking and delayed coking may also be used. Before using naphtha as feed for a catalytic reforming unit, it must be hydrotreated to saturate the olefins and to hydrodesulfurize... 

The performance of a novel microwave-induced pyrolysis process was evaluated by studying the degradation of HDPE and aluminiutn/polymer laminates in a semibatch bench-scale apparatus. The relationship between temperature, residence time of the pyrolytic products in the reactor, and the chemical composition of the hydrocarbon fraction produced was investigated. 28 refs. 

Yasumoto et al. (30) describe two components of a Pseudomonas sp. culture with identical HPLC retention times to TTX and anhydro-TTX. These fractions produced typical signs of TTX intoxication in mice, with median death times similar to standard TTX and anhydro-TTX. Noguchi et al. (32) demonstrate by HPLC and GC-MS analyses that 7 biotypes of Vibrio sp. produced substances with retention times and molecular weights similar to TTX and anhydro-TTX. However, they observed mouse toxicity in only 1 biotype. Likewise, Simidu et al. (34) report that extracts of V. alginolyticus ATCC 17749 cultures displayed TTX-like toxicity in mice. The latter study shows that a variety of marine bacteria, plus E. coliy produced substances that, by HPLC analysis, were identical to TTX and anhydro-TTX. 

Figure 6. Schematic representation of the model used by Williams et al. (1986) to calculate the age of the Oldoinyo Lengai (Tanzania) caibonatite magma. The model assumes an instantaneous Ra-Th fractionation produced by the exsolution of a carbonatite melt from a nephelinite parental magma in radioactive equilibrium for both Ra-Th pairs. The existence of Ra- Th disequihbria indicates that the fractionation occurred shortly before eruption, and thus the ( Tla/ °Th) ratios have not significantly changed since the exsolution. By assuming the same Ra-Th fractionation for both pairs, the ( Ra/ °Th) in the carbonatite gives the ( Ra/ h) ratio just after the exsolution, and its age can then be calculated from the equation ...

Preparative TLC (System I, 85 15 2 chloroform/methanol /water followed by System IV, 50 50 2 hexane/ethyl ether/formic acid) of the chloroform/acetone fraction produced 43 separate bands, 33 of which had definite activity. IR spectra of these active bands were strikingly similar, exibitlng the same major features as noted for the unseparated chloroform/acetone fraction. UV spectra were also similar absorption at 275 and 220 nm, with the latter being strongest. 

Coagulation of natural rubber latex by stages with the object of removing the yellow colouring matter in the first fraction. The latex in the second fraction produces a white crepe rubber. See Bleaching Agent. 

As the proportions of the various fractions produced do not match consumer demand, catalytic cracking is used to break down larger hydrocarbon molecules in the heavy fractions into smaller molecules, such as those used as gasoline. In industry, the vapour of the alkane being cracked is passed over a heated catalyst of aluminium oxide in the absence of air. 

Textile dyes can be dissolved or solubilised in water to a greater or lesser extent, this being essential for all conventional dyeing processes. Since solubility in water is generally accompanied by insolubility in nonpolar solvents, most textile dyes have this property. Solvent dyes, on the other hand, are soluble in organic solvents but insoluble in water. Solvent dyes are used as colour markers for the many different hydrocarbon fractions produced in oil refineries. Although the concentration of dye is low, the vast volumes involved makes the overall dye usage considerable. 

The composition of protein and starch fractions produced from pin milling and air classification are related to a number of variables variability in composition of field pea cultivars, number of passes through pin mill and air classifier, vane settings and protein content of peas, and seed moisture (5,9,23,31). 

Dry bean flour fractions produced by dry roasting, milling and air classification resulted in versatile food ingredients. Fractions possessed good functional and nutritional properties which were found to be acceptable in a variety of food systems. These processes and products appear to have potential for improving nutritive status through improved dry bean utilization. 

ISOTOPIC FRACTIONATION PRODUCED DURING DISSIMILATORYFe(in) REDUCTION... 

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