Pyrolysis conditions

Kerogen Decomposition. The thermal decomposition of oil shale, ie, pyrolysis or retorting, yields Hquid, gaseous, and soHd products. The amounts of oil, gas, and coke which ultimately are formed depend on the heating rate of the oil shale and the temperature—time history of the Hberated oil. There is Htde effect of shale richness on these relative product yields under fixed pyrolysis conditions, as is shown in Table 5 (10). 

Thermal isomerization of a-pinene, usually at about 450°C, gives a mixture of equal amounts of dipentene (15) and aHoocimene (16) (49,50). Ocimene (17) is produced initially but is unstable and rearranges to aHoocimene, which is subject to cyclization at higher temperatures to produce a- and P-pyronenes (18 and 19). The pyrolysis conditions are usually optimized to give the maximum amount of aHoocimene. Ocimenes can be produced by a technique using shorter contact time and rapid quenching or steam dilution (51). 

The stmcture of residual char particles after devolatilization depends on the nature of the coal and the pyrolysis conditions such as heating rate, peak temperature, soak time at the peak temperature, gaseous environment, and the pressure of the system (72). The oxidation rate of the chat is primarily influenced by the physical and chemical nature of the chat, the rate of diffusion and the nature of the reactant and product gases, and the temperature and pressure of the operating system. The physical and chemical characteristics that influence the rate of oxidation ate chemical stmctural variations, such as the... 

PTFE decomposes to TFE with first-order kinetics and a 347.4-kJ/mol activation energy under vacuum pyrolysis conditions It is extremely flame resistant and does not bum in air Its limiting oxygen mdex (LOR, the muumum oxygen content of an atmosphere under ambient conditions that sustams combustion, is 96%, which means that it requires almost pure oxygen for combustion... 

In contrast to this behavior stabilized sulfonyl ylides 125 lose PhjP under flash vacuum pyrolysis conditions to give sulfonyl carbenes 127 which evolve to the formation of various products among which the alkenes 129, observed in all the cases (Scheme 35) [129]. 

In contrast to carbenes of the AX2 type, which contain three atoms, generation of carbenes with a more complex structure under photolysis or vacuum pyrolysis conditions may be accompanied by intramolecular rearrangements. Thus, the matrix isolation study of the vacuum pyrolysis... 

Matrix IR spectra of various silenes are important analytical features and allow detection of these intermediates in very complex reaction mixtures. Thus, the vibrational frequencies of Me2Si=CH2 were used in the study of the pyrolysis mechanism of allyltrimethylsilane [120] (Mal tsev et al., 1983). It was found that two pathways occur simultaneously for this reaction (Scheme 6). On the one hand, thermal destruction of the silane [120] results in formation of propylene and silene [117] (retroene reaction) on the other hand, homolytic cleavage of the Si—C bond leads to the generation of free allyl and trimethylsilyl radicals. While both the silene [117] and allyl radical [115] were stabilized and detected in the argon matrix, the radical SiMc3 was unstable under the pyrolysis conditions and decomposed to form low-molecular products. 

One potential solution to these problems, suggested some 20 years ago by Chantrell and Popper (1), involves the use of inorganic or organo-metallic polymers as precursors to the desired ceramic material. The concept (2) centers on the use of a tractable (soluble, meltable or malleable) inorganic precursor polymer that can be shaped at low temperature (as one shapes organic polymers) into a coating, a fiber or as a matrix (binder) for a ceramic powder. Once the final shape is obtained, the precursor polymer can be pyrolytically transformed into the desired ceramic material. With careful control of the pyrolysis conditions, the final piece will have the appropriate physical and/or electronic properties. 

Several studies have dealt with the problem of discriminating between mastic and dammar, and three marker compounds of mastic have been identified moronic, masticadienonic and acetyl masticadienolic acids [42], The chemical structure of (iso)masticadienonic acid and 3-0-acetyl-3-epi(iso)masticadienonic acid is characterized by a side chain, as for dammarane molecules, but with a carboxylic acid end group (Table 12.1). Under pyrolysis conditions this side chain is susceptible to cleavage as demonstrated by the presence, among the pyrolysis products of mastic, of 2-methyl-pent-2,4-dienoic acid, that perfectly matches with the chemical structure of the side chain end. In addition 3-(9-acetyl-3-epi-(iso)masticadienolic acid also loses the acetyl group and, in contrast to masticadienonic acid, is not detected at all. 

There is substantial data to support reaction sequence [2] and some data suggesting sequence [3] (21, 22) may occur under certain pyrolysis conditions, but no evidence has been published for [3] in the absence of a large excess of polymer substrate. In the case of [2] and [3] it has been suggested that these reactions would be dependent on the carbon-halogen bond strength in the organohalogen component (9). 

The Diels-Alder adduct of sulpholene and cyclopentadiene is a useful starting material for substituted diene synthesis121. The diene moiety is unmasked by retro-Diels-Alder reaction and sulphur dioxide extrusion under flash vacuum pyrolysis conditions (equations 74 and 75)122,123. 

An alternative approach has been to use Curie-point pyrolysers. The use of the Curie point in accurately reproducing a temperature has already been discussed for the calibration of TG furnaces (p. 481). In a slightly different way the Curie point can be used for accurately reproducing pyrolysis conditions with the added advantage that the rise time is only about 0.4 s. The... 

The photolysis of trimethyl boron at temperatures up to 300 °C may occur by reactions (1)—(3) of the pyrolysis process112. Subsequent steps which lead to hydrogen formation in the pyrolysis system are much less important [CH4 H2 a 2 1 under pyrolysis conditions, 9 1 in photolysis system]. 

Beginning with allene (1) itself, its thermal dimerization to 1,2-bismethylenecy-clobutanes (126) constitutes one of the oldest allene reactions known. Although the yield is only moderate (in the region of 30%, depending on the pyrolysis conditions), the dimerization generates a very useful diene from a readily available starting material (Scheme 5.43) [117]. 

Scheme 48). The very slow pyrolysis of the (4-methylphenyl)amine derivative (1223, R = Me) at 540°C and 10 5 torr resulted in IR absorption at 2079 cm-1, indicating the presence of methyleneketene (1224, R = Me). Under less carefully controlled pyrolysis conditions at higher pressure, the 2079 cm-1 absorption was accompanied by an absorption at 2123 cm 1, pointing to the presence of imidoylketene (1225, R = Me). Above 600°C, both intermediates disappeared and quinoline (1226, R = Me) was the only product. 

Aromatic polyesters, commercially important molding resin materials, show a low degree of flammability and produce high percentages of char on exposure to a flame or on heating to pyrolysis conditions (9). 

The influence of pyrolysis conditions on the structure, morphology, electrical properties, and electrochemical behavior has been investigated. Raman spectroscopy shows that characteristic sp carbon bands form from the pyrolysis treatments. The electrochemical properties for a few of the electrode systems have been reported and, for the most part. 

Alder-Rickert cleavage has not been widely used for cycloproparene synthesis, since the preparation of the precursors is often tedious, except for the simple cases like 7,7-difluorobenzocyclopropene (21). The approach offers, however, decisive advantages in special situations. If the Alder-Rickert cleavage is carried out under flash-vacuum pyrolysis conditions, the products may be isolated under neutral conditions and at low temperature. Thus the synthesis of the highly reactive li/-cyclopropa[a]naphthalene (56) by pyrolysis of 68 has been achieved by this approach. Several other approaches to 56 failed. 

The study of retained NMP in the films was conducted using a Du Pont DP-102 Mass Spectrometer. These films were heated in a tube-type pyrolysis furnace and the amount of NMP given off detected and quantitized against a calibration curve. Pyrolysis conditions were 750°Cx2 seconds with quantitation done on mass 99 molecular ion. A CDS-190 Pyroprobe was used for the pyrolysis study. 

The sulfone 80 undergoes clean extrusion of sulfur dioxide on exposure to flash vacuum pyrolysis conditions to produce divinyl compound 81 (Equation 18) <1999J(P1)605>. 

Careful examination of the pyrolysis of the trithiane from thioacetone has shown that the product is always a mixture of the thioketone, CH3CSCH3, and the thioenol, CH2=CSHCH3 (50). The amount of thioenol, which is always the lesser component, varies from about 5-15 % depending upon pyrolysis conditions. Below 500° C, the trithiane is completely pyrolyzed. Above 600° C, thioacetone undergoes extensive decomposition. In between 500° C and 600° C, the relative proportion of thioketo tautomer increases with increasing pyrolysis temperature. 

Whereas the parent difluoro-vinylcyclopropane isomerizes to difluorocyclopentene under pyrolysis conditions, the corresponding alkyl compounds also lead to acyclic dienes. The activation energy for the difluoro-vinylcyclopropane isomerization is practically identical with that observed for the unsubstituted hydrocarbon [211, 212], If the alkyl group is oriented cis to the vinyl substituent, only dienes are isolated, and the process occurs at much lower, temperatures. Presumably these stereoisomers rearrange by a different mechanism (a 1,5-homodienyl hydrogen shift [213]). When the dichlorocyclopropane XVII is subjected to flash vacuum pyrolysis it isomerizes to 9,9-dichloro-bicyclo[5.3.0]dec-l(7)-ene [214],... 

Under flash vacuum pyrolysis conditions 1- and 2-(l-adamantyl)indazoles as well as 1-, 2- and 3-tritylindazoles are mutually interconverted (91BSF592, 89BSB349). 

Oxadiazoles undergo thermal and photochemical ring cleavage at the 0(1)-N(2) and C(3)-C(4) bonds to yield nitrile and nitrile oxide fragments, and products derived therefrom. Thus, diphenylfurazan (30, X = 0) decomposes under flash vacuum pyrolysis conditions (600°C, 10-3 mm... 

There is less evidence for the participation of azomethine ylides 88 in the early examples of the thermal cyclization reactions of Meldrum s acid derivatives 86. This reaction, conducted under flash vacuum pyrolysis conditions, may proceed via the methyleneketene 87. Hydrogen transfer from this highly unstable species may lead to the dipolar intermediate 88, which could cyclize either in a 6zr, to give 89, or 8tt, to give 90, manner (Scheme 27) [83JCS(CC)988 85TL833 87JCS(CC)140]. 

Most probably sulfur is not cleaved from the products after cycloreversion, because methyl, ethyl, and phenyl isothiocyanate are stable under the pyrolysis conditions. 

As mentioned above, the oxazirane ring ha limited stability. The products of its thermal decomposition vary considerably with the structure of the oxaoirane and also with the pyrolysis conditions. The products of thermal decomposition of the 3-arytoxaziraoes are the isomeric nitrones. This is apparently a general reaction and may be conveniently accomplished by beating solutions of the oxasiraun in... 

The behavior of various alkyloxaairanee at elevated temperatures under pyrolysis conditions has also been, studied. Under these conditions amides generally are obtained in good yield. These reactions are carried out in the gas phase at 200-300° and are a direct consequence of the relatively weak oxygen-nitrogen bond. Whether unpairing of the electrons of this bond occurs is uncertain but the reaction may best be described as a concerted rearrangement as indicated below ... 

Pyrolysis of CH4 and NH3 gives very low yields of amino acids. The pyrolysis conditions are from 800° to 1200°C with contact times of a second or less. However, the pyrolysis of CH4 and other hydrocarbons gives good yields of benzene, phenylacetylene, and many other hydrocarbons. It can be shown that phenylacetylene would be converted to phenylalanine and tyrosine in the primitive ocean.17 Pyrolysis of the hydrocarbons in the presence of NH3 gives substantial yields of indole, which can be converted to tryptophan in the primitive ocean. 

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