Pyrolysis studies

One noteworthy neurotoxic response was demonstrated in laboratory pyrolysis studies using various types of phosphoms flame retardants in rigid urethane foam, but the response was traced to a highly specific interaction of trimethylolpropane polyols, producing a toxic bicycHc trimethylolpropane phosphate [1005-93-2] (152). Formulations with the same phosphoms flame retardants but other polyols avoided this neurotoxic effect completely. 

Hexafluoroetbane [76-16-4] M 138.0, b -79°. Purified for pyrolysis studies by passage through a copper vessel containing C0F3 at ca 270°, and held for 3h in a bottle with a heated (1300°) platinum wire. It was then fractionally distd. [Steunenberg and Cady J Am Chem Soc 74 4165 1962.]... 

Pyrolysis studies have often been applied to chlorotnfluoroethylene and tetrafluoroethylene Pyrolysis of chlorotnfluoroethylene at 560-590 °C yields 70-83% of a mixture containing both linear and cyclic dimers of chlorotri... 

Table I. Pyrolysis Studies on MeNH-[H2SiNMe]x-H Oligomers...

Borazine Pyrolysis Studies. In a simplistic manner, one can visualize the formation of boron nitride via stepwise eliminations between rings, i.e.,... 

The material balance is consistent with the results obtained by OSA (S2+S4 in g/100 g). For oil A, the coke zone is very narrow and the coke content is very low (Table III). On the contrary, for all the other oils, the coke content reaches higher values such as 4.3 g/ 100 g (oil B), 2.3 g/ioo g (oil C), 2.5 g/ioo g (oil D), 2.4/100 g (oil E). These organic residues have been studied by infrared spectroscopy and elemental analysis to compare their compositions. The areas of the bands characteristic of C-H bands (3000-2720 cm-1), C=C bands (1820-1500 cm j have been measured. Examples of results are given in Fig. 4 and 5 for oils A and B. An increase of the temperature in the porous medium induces a decrease in the atomic H/C ratio, which is always lower than 1.1, whatever the oil (Table III). Similar values have been obtained in pyrolysis studies (4) Simultaneously to the H/C ratio decrease, the bands characteristics of CH and CH- groups progressively disappear. The absorbance of the aromatic C-n bands also decreases. This reflects the transformation by pyrolysis of the heavy residue into an aromatic product which becomes more and more condensed. Depending on the oxygen consumption at the combustion front, the atomic 0/C ratio may be comprised between 0.1 and 0.3 ... 

Further detailed studies in this area are obviously needed to resolve the chemistry involved. Such pyrolysis studies supplemented by hydrogenation experiments with acid-form and salt-form brown coals offer promise of resolving the precise role of pyrolysis in the hydrogenation of these coals and of how the ash-forming cations participate in the hydrogenation reactions. 

Another valuable advantage of Raman spectroscopy, which is unique, is its capability of being used to characterise carbon species, in particular graphitic and amorphous carbon this can be of value to many degradation and pyrolysis studies. Perfectly ordered graphite is characterised by a Raman-active vibrational mode that occurs at 1,575 cm-1 this band is usually referred to as the C7 band. With increasing disorder in the carbon, a new band, the D band, appears at... 

Several years later, Kanatzidis et al. reported the preparation of hetero-binuclear complexes of tetrahedrally arranged Cu and In centers, with two bridging thiolato or selenolato groups, [ PPh3 2Cu(p-QEt)2In(SEt)2], (Q = S or Se) (i.e., equation 6.3).38 Pyrolysis studies undertaken revealed that the Se derivative could be converted into CuInSe2 at 400-450 °C at 0.01 mm Hg (see equation 6.4). However, none of the precursors had been evaluated in a thin-film deposition study. 

The mechanism for the photolysis of diethyl mercury is identical to that for the pyrolysis88, 90. The reaction of C2H5 with diethyl mercury, which apparently was of no importance under the conditions used in the pyrolysis studies, is also insignificant over the temperature range 25-75 °C. The photolysis produces ethyl radicals which initially have about 31 kcal.mole-1 excess energy so that the C4/C2 ratio is dependent on the surface/volume ratio and on the total pressure in the system. At 25 °C with essentially thermalized radicals (200 torr Ne added) CJC2 20 while at 20 torr CJC2 3. 

The expulsion of CO from ketocyclohexadienyl radical is also reasonable, not only in view of the data of flow-reactor results, but also in view of other pyrolysis studies [64], The expulsion indicates the early formation of CO in aromatic oxidation, whereas in aliphatic oxidation CO does not form until later in the reaction after the small olefins form (see Figs. 3.11 and 3.12). Since resonance makes the cyclopentadienyl radical very stable, its reaction with an 02 molecule has a large endothermicity. One feasible step is reaction with O atoms namely,... 

A mechanism involving a carbene intermediate can also be drawn and is supported by pyrolysis studies ... 

A reevaluation of molecular structure of humic substances based on data obtained primarily from nuclear magnetic resonance spectroscopy, X-ray absorption near-edge structure spectroscopy, electrospray ionization-mass spectrometry, and pyrolysis studies was presented by Sutton and Sposito (2005). The authors consider that humic substances are collections of diverse, relatively low molecular mass components forming dynamic associations stabilized by hydrophobic interactions and hydrogen bonds. These associations are capable of organizing into micellar structures in suitable aqueous environments. Humic components display contrasting molecular motional behavior and may be spatially segregated on a scale of nanometers. Within this new structural context, these components comprise any molecules... 

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. 

T. Bhaskar, M. Tanabe, A. Muto, and Y. Sakata, Pyrolysis study of a PVDC and HIPS-Br containing mixed waste plastic stream Effect of the poly(ethylene terephthalate), /. Anal. Appl. Pyrolysis, 77(l) 68-74, August 2006. 

The possibility of the above reactions, their extent, and hence the main source of methane formation (which is the chief hydrocarbon in pyrolysis gases) have been examined in the present work by carrying out pyrolysis studies on coals, dehydrogenated coals, and reduced coals. 

Materials. To satisfy the requirements for models for pyrolysis studies, it was necessary to select compounds that were of high purity and well-defined structure which would produce carbonaceous residues when subjected to high temperatures. Commercially available organic dyestuffs proved to be a ready source of model compounds containing various heterocyclic structures. It was necessary to purify these dyes by recrystallization and extraction to remove small quantities of organic impurities and residual inorganic contaminants. The identity, structure, and chemical composition of the model compounds can be seen in Table I and Figure 1. 

Starch and Bakelite were obtained from stock supplies and were used as-received for pyrolysis studies of blends. Hydrogenated creosote was prepared in the laboratory by catalytically hydrotreating a 270°-355°C. creosote fraction to remove all heterocyclic impurities and to saturate completely the ring systems. 

Study of Volatile Products from Thermal Analyzers. The MC-2 mass chromatograph is ideally suited for thermal analysis or pyrolysis studies for the obvious reasons of quantitative and qualitative analysis and also for its unique trapping assembly. With the traps, sample effluents can be collected and concentrated over extended periods of time prior to analysis. 

One further finding with the —lIRNMeR — pyrolysis studies comes from Raman studies of the ceramic product. The NMR data show no traces of Si—C bonds, nor does the Raman spectrum. However, the Raman spectrum does show the presence of C—N bonds up to 1200 °C (the highest temperature studied). This suggests that the silicon nitride nanoparticles interact with the carbon matrix through C—N bonds. One might speculate that the interface looks somewhat like C3N4. 

The SIMS spectrum of a 0.5 mm thick film of polystyrene cast on silver is shown in Figure 8. The characteristic ions, phenyl-type (m/z 77, 78, 79), benzyl (m/z 91), and protonated styrene (m/z 105) along with higher m/z ions resembling those from pyrolysis studies, are observed. 

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