Cryogenic reactor

If this trend is extrapolated to lower temperatures it is clear that at temperatures varying between -78 and -150°C for carbon—hydrogen bonds on various types of hydrocarbons, AF becomes zero and then endothermic. Under these conditions (AG < 0) the reaction with elemental fluorine will not and should not proceed at all Wfe have observed this in many cases experimentally. At temperatures as low as -150°C the reaction of fluorine with all studied organic compounds either does not occur or is extremely slow. We have occasionally reported reactions in the cryogenic reactor as low as -120°C. It should be explained that the — 120°C reported is the temperature of a single trap in a multizone reactor rather than that for the entire reactor. It is possible that fluorination occurs during the volatilization process at such low temperatures. 

However, there is another approach to low-temperature chemistry that offers much more promise for yielding product materials in useful concentrations and amounts. While in free-radical stabilization one arrests or stops chemical processes by means of a matrix isolation, in synthesis studies the observation of the chemical process becomes now the essence of the experiment. In the former area one might produce carbene (CH2) and trap it for a detailed study by a variety of techniques. Typically, in the latter area the CH2 would be pumped into a cryogenic reactor and one would observe the reactions that might occur and their rates. The kind of experiments that one may do and the nature of the results are best illustrated by looking at several current examples. 

Instructions for the conversion of polynuclear arenes (coronene, anthracene, decacyclene, naphthacene, naphthalene, pentacene, ovalene, 9,10-benzphenanthrene, 1,2-benzanthracene, 1,3,6,8-tetraphenylpyrene) into the corresponding perfluoro-alicyclic compounds and of 1,4-dichlorobenzene into perfluorocyclohexane by LaMar controlled-concentration direct-flow fluorination at room temperature and atmospheric pressure are now available in the patent literature, and precise details of the use of the method, in conjunction with a cryogenic reactor, to convert neopentane into perfluoroneopentane in low yield (10% after g.l.c. isolation) are also to hand. jhe results of kinetic studies on the direct fluorination of methane, [ H2]methane, halogenomethanes, and olefins are likewise in print. Treatment of the perfluoropropene dimers (CFsjsCiCF-CFs-CFs and trans-(CF3)2CF-CF -CF CFa with fluorine at —78 °C yields perfluoro-(2-methylpentane) quantitatively, while fluorination of a mixture of the trimers [(CFsjaCFlaC .CF-CFs and... 

LaMar direct fluorination (see p. 2) of ethyl acetate in a four-zone cryogenic reactor (lowest temperature —100 °C) provides the trifluoroacetates CF3 C02 C2F6 and CF3-C02-CHF-CF3 in 5 and 20% yield, respectively, after isolation by g-l.c. " apparently fluoride ion readily initiates decomposition of these esters according to F" + CFa COs-CFX CFsCFa COF -I- CFs-CFX-Q- -> F -I-CFa CXO (X = H or J). 

Figure 3-16. Flow diagram of the Lummus process for producing butadiene (1) reactor, (2) quenching, (3) compressor, (4) cryogenic recovery, (5) stabilizer, (6) extraction.

This method of low-temperature, direct fluorination involves very precise control of fluorine concentrations during the reaction, and initial high dilution of the fluorine with helium. The reaction of elemental fluorine with organometallic compounds is conducted (27) in a cryogenic-zone reactor (see Fig. 8) at temperatures in the range of - 78 to... 

The process begins with a gasification process that converts coal into carbon monoxide and hydrogen. Part of this gas is sent to a water-gas shift reactor to increase its hydrogen content. The purified syngas is then cryogenically separated into a carbon monoxide feed for the acetic anhydride plant and a hydrogen-rich stream for the synthesis of methanol. 

Agopovich, J. W. et al., J. Amer. Chem. Soc., 1983, 105, 5048 After ozonisation of trifluoroethylene in chlorotrifluoromethane solution at —95°C, the reactor must only be allowed to warm slightly (to —88°C) during subsequent cryogenic distillation. When allowed to warm towards ambient temperature the reactor exploded violently. The residue from distillation is peroxidic and probably sensitive to sudden temperature increases. 

In the newer Sasol plants the tailgas from the FT reactors is first water-washed (to extract the remnants of water-soluble oxygenated compounds), then treated in a Benfield unit (to remove all CO ) and then fed to a cryogenic unit where the gas is separated into four streams, a CH -rich, a H -rich, a C and a C /C stream. 

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