Trans-atmospheric

Air separation by PSA on a large scale is today dominated by machines in which the pressure swing may be from near atmospheric to substantially sub-atmospheric pressure. The industry typically calls these machines vacuum swing adsorption (VSA) separators. A second sub-class in air separation is the machines that use a pressure swing the ranges from somewhat super-atmospheric to sub-atmospheric and these may be called trans-atmospheric PSA. The distinctions made here have implications as to equipment specifications and performance limitations in both bed size factor and O2 recovery. 

Practical concerns, specifically mass transfer, Umit the recovery to values in the high 70% range. All this said, the vast majority of operating air separation units are the small capacity medical oxygen concentrators. These operate under either PSA or VSA or trans-atmospheric process cycles. The key objective for medical O2 is small unit size and power consumption prior to the push for portability was a secondary consideration. There are many such PSA air separation units that operate at recoveries as low as 35%. 

Schiff, H. I G. I. Mackay, C. Castledine, G. W. Harris, and Q. Tran, Atmospheric Measurements of Nitrogen Dioxide with a Sensitive Luminol Instrument, Water, Air Soil Pollution, 30, 105-114 (1986). 

Alkenes resemble alkanes m most of their physical properties The lower molecular weight alkenes through 4 are gases at room temperature and atmospheric pressure The dipole moments of most alkenes are quite small Among the 4 isomers 1 butene cis 2 butene and 2 methylpropene have dipole moments m the 0 3-05 D range trans 2 butene has no dipole moment Nevertheless we can learn some things about alkenes by looking at the effect of substituents on dipole moments... 

W. Wein, Flow Dynamics of Atmospheric Fluid Bed Combustion Systems and their Effect on SO Capture and NO Suppression, trans. Lurgi from UGB Magafine, Feb. 1985, pp. 119-123. 

PApo-8 -carotenal. The specifications of this colorant. (38) were discussed earlier. P-Apo-8 -carotenal has provitamin activity with 1 g of the colorant equal to 1,200,000 lU of vitamin A. Like all crystalline carotenoids, it slowly decomposes ia air through oxidatioa of its coajugated double boads and thus must be stored ia sealed coataiaers uader an atmosphere of iaert gas, preferably under refrigeration. Also like other carotenoids P-apo-8 -carotenal readily isomerizes to a mixture of its cis and trans stereoisomers when its solutions are heated to about 60°C or exposed to ultraviolet... 

Cyanoanthracene (anthracene-9-carbonitrile) [1210-12-4] M 203.2, m 134-137°. Purified by crystn from EtOH or toluene, and vacuum sublimed in the dark and in an inert atmosphere [Ebied et al. 7 Chem Soc, Faraday Trans 7 76 2170 1980 Kikuchi et al. J Phys Chem 91 574 1987. ... 

Physalien (all trans /J-carotene-3,3 -diol dipalmitate) [144-67-2] M 1044, m 98.5-99.5°, A (Xmax) 1410 (449nm), 1255 (478nm) in hexane. Purified by chromatography on water-deactivated alumina, using hexane/diethyl ether (19 1) to develop the column. Crystd from benzene/EtOH. Stored in the dark, in inert atmosphere, at 0°. 

Calcium thiosulfate [10124-41-11 M 152.2, m 43-49°, pKj 0.6, pKj 1.74 (for H2S2O3). Recrystd from water below 60° in a N2 atmosphere, followed by drying with EtOH and Et20. Stored in a refrigerator. [Pethybridge and Taba J Chem Soc, Faraday Trans 7 78 1331 1982.]... 

The mixture was then allowed to warm to room temperature in a nitrogen atmosphere during which process the ammonia evaporated. The reaction mixture was then acidified with 1 N aqueous hydrochloric acid, and the organic constituents extracted with ethyl acetate. The ethyl acetateextracts were combined, washed with water and dried. Evaporation of the ethyl acetate under reduced pressure yielded 1.4 g of crude dl-trans-3-(r,r-dimethylheptyl)-6,6a, 7,8,10,10a -hexahydro-1 -hydroxy-6,6-dimethyl-9H-dibenzo(b/J] pyran-9-one. The... 

Figure 9-79A. COg absorption from atmosphere effect of liquor rate on Kqs at atmospheric pressure. Reproduced by permission of the American Institute of Chemical Engineers, Spector, N. A., and Dodge, B. F., Trans. A.I.Ch.E., V. 42 (1946) p. 827 all rights reserved.

Figure 9-87. X-Y diagram for adicibatic absorption of HCl at 1 atmosphere. Reproduced by permission of the American Institute of Chemical Engineers, Oldershaw, C. F., Simenson, L, Brown, T. and Rad-cliffe, F. Trans. Sect. Chemical Engineering Progress, V. 43, No. 7 (1947) p. 371 all rights reserved.

Spector, N. A., and B. F Dodge, Removal of Carbon Dioxide from Atmospheric Air, Trans. Amer. Inst. Chem. Engrs. 42, 827 (1946). 

Brosse, N. Pinto, M-F. Jamart-Gregoire, B. J. Chem. Soc., Perkin Trans. 1 1998, 22, 3685. Under nitrogen atmosphere, the thermal potential is slightly lower (AH = 2150 J/g), and the onset temperature is 150 °C. 

The different ratios of 52/53 produced by cycloadditions performed at atmospheric and high pressure, and the forma tion of the unusual trans adducts 53, have been explained by the facts that (i) Diels-Alder reactions under atmospheric pressure are thermodynamically controlled, and (ii) the anti-endo adducts 52 are converted into the short-lived syn-endo adducts 54 which tautomerize (via a dienol or its aluminum complexes) to 53. The formation of trans compounds 53 by induced post-cycloaddition isomerization makes the method more flexible and therefore more useful in organic synthesis. 

Values for degassed solutions. "With one atmosphere cyclohexane. N,N-dlmethyl-l-naphthylamlne. Trans-1,6-dlphenyl-l, 3,5-hexatrlene. Average of 13 literature values (see Ref. 50). Values from many authors agree for a single exponential, but there appear to be two exponentials that show wavelength dependence. 2,5-Dlphenyloxazole. "p-Bls(2-phenylozazolyl)benzene. Decay time dependent on Cl or I" concentration. 

When the aim is isolation for identification by direct probe insertion mass spectrometry (MS), plastic materials, filter papers, and blenders should be avoided to prevent contamination during extraction and chromatography. It is also very important to avoid the cis-trans isomerization of carotenoids in solution, which is accelerated by heat, light, acids, and active surfaces. Therefore, a pure carotenoid or even a crude extract should never be stored in solution it should be kept completely dry in an inert atmosphere at low temperature. 

Fig. 6. UV-Vis absorption spectral change of trans-25 (0.126 mM) in acetonitrile under a nitrogen atmosphere upon photoirradiation with three bright lines (Amaj[ = 365, 436, and 546, nm) of a super-high-pressure Hg lamp. The spectra are depicted at 10 min intervals of photoirradiation. The irradiation with each bright line was continued for 30 min in ascending order of wavelength. (Reprinted with permission from Ref. 153.)...

Ivey, H. J., and D. J. Morris, 1965, The Effect of Test Section Parameters on Saturation Pool Boiling Burnout at Atmospheric Pressure, AIChE Chem. Eng. Prog. Symp. Ser. 67(60) 157—166. (2) Jacket, H. S., J. D. Roarty, and J. E. Zerbe, 1958, Investigation of Burnout Heat Flux in Rectangular Channels at 2000 psia, Trans. ASME, J. Heat Transfer 50 391. (5)... 

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