Temperature fractionation extract

Dual nickel, 9 820—821 Dual-pressure processes, in nitric acid production, 17 175, 177, 179 Dual-solvent fractional extraction, 10 760 Dual Ziegler catalysts, for LLDPE production, 20 191 Dubinin-Radushkevich adsorption isotherm, 1 626, 627 Dubnium (Db), l 492t Ductile (nodular) iron, 14 522 Ductile brittle transition temperature (DBTT), 13 487 Ductile cast iron, 22 518—519 Ductile fracture, as failure mechanism, 26 983 Ductile iron... 

B. 2,2-(Trimethylenedithio)cyclohexanone. A solution of 3.02 g. (0.02 mole) of freshly distilled 1-pyrrolidinocyclohexene, 8.32 g. (0.02 mole) of trimethylene dithiotosylate4 (Note 2), and 5 ml. of triethylamine (Note 3) in 40 ml. of anhydrous acetonitrile (Note 4), is refluxed for 12 hours in a 100-ml., round-bottom flask under a nitrogen atmosphere. The solvent is removed under reduced pressure on a rotary evaporator, and the residue is treated with 100 ml. of aqueous 0.1 N hydrochloric acid for 30 minutes at 50° (Note 5). The mixture is cooled to ambient temperature and extracted with three 50-ml. portions of ether. The combined ether extracts are washed with aqueous 10% potassium bicarbonate solution (Note 6) until the aqueous layer remains basic to litmus, and then with saturated sodium chloride solution. The ethereal solution is dried over anhydrous sodium sulfate, filtered, and concentrated on a rotary evaporator. The resulting oily residue is diluted with 1 ml. of benzene and then with 3 ml. of cyclohexane. The solution is poured into a chromatographic column (13 x 2.5 cm.), prepared with 50 g. of alumina (Note 7) and a 3 1 mixture of cyclohexane and benzene. With this solvent system, the desired product moves with the solvent front, and the first 250 ml. of eluent contains 95% of the total product. Elution with a further 175 ml. of solvent removes the remainder. The combined fractions are evaporated, and the pale yellow, oily residue crystallizes readily on standing. Recrystallization of this material from pentane gives 1.82 g. of white crystalline 2,2-(trimethylenedithio)cyclo-hexanone, m.p. 52-55° (45% yield) (Note 8). 

For m -> oo, the critical value is identical with that in a d- solvent, i.e., A2 = 0 and X = 0-5- Since the solubility of macromolecules decreases with increasing molecular weight, it is possible to separate these materials with respect to their molecular weights by changing the composition of the solvent and/or the temperature. In general, one roughly distinguishes between two methods, namely fractional precipitation and fractional extraction. 

The atactic amorphous portion (9-16% of the total) contained in the obtained polypropylene has been separated by treating the raw polymer with n-heptane at room temperature. When operating in such a way, we have not separated the stereoblock fraction (extractable in boiling n-hep-tane) from the isotactic (not extractable in boiling n-heptane) fraction of polymer. The results reported in this paper are generally referred to the crystalline fraction, named non-atactic, which contains also some stereoblock polymers (at the considered polymerization temperatures, the latter generally correspond only to 5-7 % of the total) (9)... 

The mixture in the autoclave is homogeneous. This was insured by keeping the Magne Drive stirrer always at a steady 1500 r.p.m. It was experimentally proved that even distribution of coal and tetralin in the autoclave is a fair assumption because the fraction extracted from the last portion of mixture, which remained in the autoclave and was taken after the system cooled to room temperature and the autoclave was opened, was found to be very close to the yield obtained from the last sample taken from the system through the sample lines at reaction temperature. 

At each temperature, the method of finite differences was used and j evaluated for a series of x. The plot of ( x/ t)/l — x = k vs. x closely approximated a straight line (Figure 8). It is therefore considered that the rate constant, k, changes linearly with x, the fraction extracted. 

Stone et al. (S29) developed by a mathematical analysis the functional relationship between the rate of extraction of silica from pure quartz in sodium hydroxide solution and time, temperature, sodium hydroxide concentration, and particle size. With the use of response surface methodology, a comprehensive picture of this dissolution process was obtained from a few well-chosen experiments. The fractional extraction of silica can be expressed by a second-order equation. The effect of quartz particle size and temperature are predicted to be about equal and greater than the influence of sodium hydroxide concentration and reaction time. The reaction rate is controlled by the surface area of the quartz. An increase in sodium hydroxide concentration increases the activation energy for the reactions and is found to be independent of quartz size. 

The PC/PE ratios of alcohol-fractionated lecithins are largely determined by processing variables such as alcohol polarity, concentration, lecithin/alcohol ratio, temperature, and extraction time (33). By extracting natural lecithin with a PC to PE ratio of 1.2 1 with 90% ethanol, an alcohol-soluble fraction with a PC/PE ratio of 8 1 can be obtained (33, 120). The fractions may be blended with other surfactants or carriers to obtain desired functionality. 

SCCO2 fractional extraction of soybean deodorizer distillate using an extractor with a reboiler at the bottom and obtained 83.6% tocopherol recovery at the optimal conditions of 31.03 MPa, 363 K top, and 343 K bottom temperature. Free fatty acids and squalene were concentrated in the extract together with tocopherols, whereas sterols were concentrated in the raffinate. 

In fractional extraction, the feed material is extracted in two or more stages. The selectivity for essentied oils, fatty oils, and resins is controlled in each stage throu selection of extraction pressure, temperature, or cosolvent addition. With the first extraction stage at subcrltical tenperatures, sensitive essential oils are removed at mild conditions and at slx>rt processing times. 

The nature of coke was studied by extraction of its soluble fraction with different solvents (benzene-methanol (8) and carbon tetrachloride) with a Soxhlet. After the evaporation of the solvent at room temperature, the extract was analyzed by 1-HNMR, IR and mass spectrometry. The soluble fraction of the coke is the less polymerized, and can be taken as containing the precursors that determine coke composition. 

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