Phase thermal

Production of a-methylstyrene (AMS) from cumene by dehydrogenation was practiced commercially by Dow until 1977. It is now produced as a by-product in the production of phenol and acetone from cumene. Cumene is manufactured by alkylation of benzene with propylene. In the phenol—acetone process, cumene is oxidized in the Hquid phase thermally to cumene hydroperoxide. The hydroperoxide is spHt into phenol and acetone by a cleavage reaction catalyzed by sulfur dioxide. Up to 2% of the cumene is converted to a-methylstyrene. Phenol and acetone are large-volume chemicals and the supply of the by-product a-methylstyrene is weU in excess of its demand. Producers are forced to hydrogenate it back to cumene for recycle to the phenol—acetone plant. Estimated plant capacities of the U.S. producers of a-methylstyrene are Hsted in Table 13 (80). 

Diazopyrazole (436) undergoes gas-phase thermal extrusion to form an azirine, probably by the mechanism shown (8lAHC(28)23i) 4-diazopyrazoles show normal diazonium-type reactions (Schemes 55 and 56) (67AHC(8)l). Analogous diazoimidazoles and diazopurines are known (67AHC(8)i). 

The gas phase thermal chemistry and photochemistry of oxiranes is reviewed in (77CRV473). References to thermal reactions of oxiranes are given in (B-80MI50502) and ref. 10 in (76TL1449). 

Figure 12.12 Tripping mechanism of an overcurrent-cum-single-phasing thermal relay...

Wet-air oxidation (also called liquid-phase thermal oxidation) is not a new technology it has been around for over forty years and has already demonstrated its great potential in wastewater treatment facilities. Despite this, there are some very important issues that remain to be addressed before a wet oxidation process can be scaled-up the kinetics of oxidation of many important hazardous compounds... 

High-resolution dilatometric measurements have revealed the appearance of anisotropy in the cubic-phase thermal strain in the precursive temperature region for the soft-mode martensitic transformations in VaSi/ Ni-Al, In-Tl/ and SrTiOa In the case of Ni-Al and SiTiOa, the onset temperatures for the strain anisotropy are close to those at which the appearance of central peak behaviour occurs. 

The R s of a fibrous or cellular insulation like those in Table 2 generally decrease as the temperature increases. In the case of closed-cell polymeric foams like polyurethane nr pnlyisncyanurate board, the R may decrease if the insulation temperature drops below the condensation temperature of the blowing agent in the cells. This is because of changes in the gas- phase composition and therefore the gas-phase thermal conductivity. The R of insulations also depends on density when all other factors are constant. The relationship bett een R and density... 

King and Harding296 have reported an interesting Sulfo-Cope rearrangement, and have presented evidence for the formation of the unstable sulfene (142) during the gas or liquid phase thermal [3,3]sigmatropic rearrangement of allyl vinyl sulfone (equation 88). 

More recently, a number of reports dealing with 1,3-sulfonyl shifts which proceed by other mechanisms have been published. For example, Baechler and coworkers suggested that the higher activation enthalpy observed for the isomerization of the deuterium labeled methallyl sulfone 72 in nitrobenzene at 150°C as compared to the corresponding sulfide, together with the positive entropy of activation may be taken as evidence for a homolytic dissociation mechanism (equation 44). A similar mechanism has also been suggested by Little and coworkers for the gas-phase thermal rearrangement of deuterium labelled allyl sec-butyl sulfone, which precedes its pyrolysis to alkene and sulfur dioxide. 

Many second-order reactions follow Class I rate expressions. Among these are the gas-phase thermal decomposition of hydrogen iodide (2HI - H2 + I2), dimerization of cyclopen-tadiene (2C5H6 -> C10H12), and the gas phase thermal decomposition of nitrogen dioxide (2N02 2NO + 02). 

In a nonattaching gas electron, thermalization occurs via vibrational, rotational, and elastic collisions. In attaching media, competitive scavenging occurs, sometimes accompanied by attachment-detachment equilibrium. In the gas phase, thermalization time is more significant than thermalization distance because of relatively large travel distances, thermalized electrons can be assumed to be homogeneously distributed. The experiments we review can be classified into four categories (1) microwave methods, (2) use of probes, (3) transient conductivity, and (4) recombination luminescence. Further microwave methods can be subdivided into four types (1) cross modulation, (2) resonance frequency shift, (3) absorption, and (4) cavity technique for collision frequency. 

Cross A high-pressure, mixed-phase, thermal process for cracking petroleum, introduced in the United States in 1924 by the Cross brothers, further developed by the MW Kellogg Company, and widely used in the 1920s and 1930s. Eventually, 130 units were built in the United States and abroad. 

Fleming An early liquid-phase, thermal process for cracking petroleum. See also Dubbs. Flesch-Winkler See Winkler. 

Gyro Also called Gyro-cracking. An early vapor-phase thermal cracking process for refining petroleum. 

Gas phase thermal cracking of the volatiles occurs, reducing the levels of tar. Char (fixed carbon) and ash are the pyrolysis byproducts that are not vaporized. In the second step, the char is gasified through reactions with oxygen, steam, and hydrogen. Some of the unbumed char may be combusted to release the heat needed for the endothermic pyrolysis reactions. 

The gas-phase thermal decomposition of dimethyl mercury by itself and in the presence of inert gas has been extensively investigated61,63,67,71-79. The... 

Nagahata, R., Sugiyama, J.-I., Goyal, M., Asai, M., Ueda, M. and Takeuchi, K., Solid-phase thermal polymerization of macrocyclic ethylene terephthalate dimer using various transesterification catalysts, J. Polym. Sci., Polym. Chem., 38, 3360 (2000). 

First-order kinetics have been reported for gas-phase thermal decomposition of nitroethyl carboxylates to give nitroethylene and the corresponding aliphatic acid." ... 

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