Distillation liquid air

Claude (2) A process for fractionally distilling liquid air, based on the original Linde process but using two stages. Developed by G. Claude. 

Lastly, it is possible by distilling liquid air to separate the more volatile nitrogen from the less volatile oxygen and argon. 

The most familiar mixture of chemically free elements is air, which is about four-fifths nitrogen and one-fifth oxygen, with a measurable trace of inert gases. We ve already seen how these elements can be separated by distilling liquid air because each has a different boiling point. The nitrogen in liquid air will always boil off first. 

Still another inert gas was to be discovered by Ramsay and Travers. The scientists, however, did not feel as certain as in the case of neon. One day in July, 1898, the colleagues were busy with distilling liquid air and separating it into fractions. By midnight they collected more than 50 fractions... 

Industrially, elemental nitrogen is extracted from the air by the fractional distillation of liquid air from which carbon dioxide and water have been removed. The major fractions are nitrogen, b.p. 77 K and oxygen, b.p. 90 K, together with smaller quantities of the noble gases. 

After compression and removal of impurities, the air is cooled ia heat exchangers and expanded to low pressure through a turbiae, to recover energy, or through a valve. Liquid air, which forms at about 80 K, is separated via a distillation column. The column as well as the heat exchangers and the associated piping are placed within a cold box, which is packed with iasulation to minimise heat transfer (qv) between streams and to protect the system from the ambient air external to the cold box. 

In the Hquid-phase process, both benzaldehyde and benzoic acid are recovered. This process was iatroduced and developed ia the late 1950s by the Dow Chemical Company, as a part of their toluene-to-phenol process, and by Snia Viscosa for their toluene-to-caprolactam process. The benzaldehyde recovered from the Hquid-phase air oxidation of toluene may be purified by either batch or continuous distillation. Liquid-phase air oxidation of toluene is covered more fully (see Benzoic acid). 

Carbon tetrafluoride [75-73-0] M 88.0, b -15 . Purified by repeated passage over activated charcoal at solid-C02 temperatures. Traces of air were removed by evacuating while alternately freezing and melting. Alternatively, liquefied by cooling in liquid air and then fractionally distilled under vacuum. (The chief impurity originally present was probably CF3CI). 

Pure ozone is made by fraetional distillation of the blue liquid resulting from the eooling of ozonized oxygen in liquid air. Commereially it is often supplied dissolved in ehlorofluoroearbons in stainless steel eyiinders at ea 475 psig eyiinder pressure at 20°C often transported ehilled with dry iee. These solutions ean be handled safely at vapour eoneentrations of ea 20% by volume of ozone. 

Helium occurs as a component of natural gases found under rock formations in certain locations, especially some in Texas. Argon is obtained by distillation of liquid air. 

Manufacture By distillation of liquid air, the same as nitrogen. Most oxygen is used captively, less than 20% of production being sold on the merchant market. 

Nitrogen, oxygen and argon are produced by fractional distillation of air. Liquid nitrogen (LN) is a quite cheap and safe source of cold and finds applications such as ... 

Ammonia is synthesised from its elements nitrogen and hydrogen. The nitrogen is obtained by the fractional distillation of liquid air. The hydrogen is obtained by the reaction of methane (from natural gas) with steam. 

The potential for the condensation and fractional distillation of air on the outside of equipment containing cryogenic liquids with boiling points less than that of 02 must be considered. For example, because N2 boils at a lower temperature than 02 (-196 versus -183°C), air can condense on the outside of liquid N2-bearing piping. The liquid that drops off of the piping will be enriched in 02 and can pose an enhanced fire or explosion risk in the vicinity of the equipment. 

Apparatus. The generator employed is shown in fig. 10. There are six important points. (1) The column. <4 is designed so that throttling is avoided it is at least 2 ft. long and surmounted by a reflux doublesurface water-condenser B. (2) A Perkin triangle (air-cooled), inserted between the down-condenser and the traps, enables any phosphorus oxychloride which distils to be removed. (3) It is convenient to have three traps, viz. C, ice and salt D, acetone and carbon dioxide E, liquid air. (4) The intermittent addition of the solid antimony trifluoride presents a problem. The mechanical solid feed... 

Preparation. The only important large-scale process is the fractional distillation of liquid air. 

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