Liquefied noble gases

However, as in soiid noble gas matrices, the real value of liquefied noble gases becomes apparent when other and more interesting ligands are attached to the transition metal. 

The first transition metal-nohle gas complex to be observed in liquefied noble gas solution was CrCCOlsXe (38). Continuous UV photolysis of Cr(CO)6 dissolved in liquid Xe at 175 K or liquid Kr doped with 5% Xe at 151K produced a new species. This new species had v(C—O) IR bands (Fig. 7) which could be assigned to CrlCOsXe by comparison with those of CrCCOlsXe in a Xe matrix [Eq. (2)]. When the photolysis was halted, Cr(CO)5Xe decayed Avith a lifetime of 2 s. The activation energy for the thermal decay of CrCCOlsXe in hquid Kr + 5% Xe was determined to be Ea = 15 2 kJ mol . The surprisingly long lifetime of CrCCOlsXe in solution at this temperature was attributed to the high concentration of Xe and the extremely low concentration of the other reactants. 

The noble gases are very low-boiling gases. Except for radon, they can be isolated by fractional distillation of liquefied air. Radon is collected from the radioactive disintegration of radium salts. Table 24-1 gives the percentage of each noble gas in the atmosphere. 

Although the noble gas elements are monatomic and could not give rise to dipole-dipole forces or hydrogen bonding, these elements still can be liquefied and solidified. Explain. 

Atoms-to-Mass Conversion Helium (He) is an unreactive noble gas often found in underground deposits mixed with methane. The mixture is separated by cooling the gaseous mixture until all but the helium has liquefied. A party balloon contains 5.50 X 10 atoms of helium gas. What is the mass, in grams, of the helium ... 

A gas-liquid-particle process termed cold hydrogenation has been developed for this purpose. The hydrogenation is carried out in fixed-bed operation, the liquefied hydrocarbon feed trickling downwards in a hydrogen atmosphere over the solid catalyst, which may be a noble metal catalyst on an inert carrier. Typical process conditions are a temperature of 10°-20°C and a pressure of 2.5-7 atm gauge. The hourly throughput is as high as 20-kg hydrocarbon feed per liter of catalyst volume. 

As a cheap alternative to noble metal and even nickel catalysts, Laosiripojana et al. proposed high surface area ceria [234]. Complete conversion of liquefied petroleum gas (prepared as a sulfur-free 60 wt.% propane/40 wt.% butane mixture) could be achieved above a reaction temperature of 800 °C. The S/C ratio was low at 1.45 and ethylene as a by-product could be suppressed at O/C ratios exceeding 0.6. The weight hourly space velocity was relatively low at 120 L (h gcat). however, catalyst deactivation was moderate within 70-h test duration, which is a promising result. 

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