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Pulse pyrolysis

All of these problems are overcome if the precursors are pyrolyzed in an inert host gas at high pressure, because under these conditions energy transfer occurs mostly by colhsions with the host gas, and radical recombination is largely suppressed. Of course, a constant stream of hot gas at high pressure is incompatible with the requirements of matrix isolation, so the experiment has to be carried out in a pulsed fashion. Chen and co-workers were the first to propose what they called a hyperthermal nozzle for pulsed pyrolysis at very high temperatures, at that time for gas-phase studies. Several research groups have implemented variants of this design" for work in matrix isolation and have used it successfully for a variety of sffidies. [Pg.818]

In a study of the effect of steady-state pyrolysis of tobacco vs. pulsed pyrolysis simulating the pnfting seqnence in a smoked cigarette, Patterson et al. (2904) reported that the pulsed pyrolysis procedure gave much higher levels of the low molecular weight phenols (phenol, 2-, 3-, and 4-methylphenol [o-, m-,and... [Pg.503]

Alternatively, flash vacuum pyrolysis with subsequent trapping of the products in low temperature matrices of 4 or other thermal precursors should lead to matrix-isolated lb. Under these conditions lb and the by-products are isolated in separate matrix sites and thus the thermal recombination is prevented. Several attempts for the thermal generation of lb were reported, however, in all cases difluoroacetylene 6 was found as the only C2F2 species. Thus, pulse pyrolysis of dibromodifluoroethylene 7 or the stannyl compound 8 produces 6 as the main product. [32] If CO is added in the gas phase, propadienone 4 is generated as an additional product, which indicates that lb is formed as a reactive intermediated in the gas phase that is long-lived enough to be trapped by CO. [Pg.11]

P. Almen and I. Ericsson. Studies of the thermal degradation of polysulfones by filament-pulse pyrolysis-gas chromatography. Polym. Degrad. Stabil, 50(2) 223-228,1995. [Pg.276]

Investigations on benzyl radical were also undertaken by Misic, Piech and Bally.They used this species to generate the corresponding car-bocation under matrix-isolation conditions. The study extended also to the allyl species (radical and cation), and used X-ray irradiation of the radicals to produce in situ the cations. The radicals were generated by pulsed pyrolysis in the gas phase. [Pg.62]

Pulsed pyrolysis is another source of radicals that has recently been developed [13]. The conditions are sufficiently mild that one is often able to limit the pyrolysis to the dissociation of a single bond. Then, by the selection of the correct precursor molecule, one is able to prepare relatively clean sources of radicals in an inert carrier gas for expansion cooling and spectroscopic analysis. [Pg.311]

With filament pulse pyrolysis experiments at 800 °C, the pyrolysis chamber being coupled with gas chromatography mass spectrometry have been performed with both a poly(l,4-phenylene ether sulfone) and a poly(bisphenol A ether 1,4-phenylene ether sulfone) [63]. The major products of pyrolysis are shown in Table 7.4. [Pg.188]

Pyroprobe 1000. This provides complete choice of thermal processing parameters. Pulse pyrolysis is permitted at rates up to 20 °C per second to temperatures as high as 1400 °C. In addition to accuracy and reproducibility, the temperature versatility allows for uninterrupted sequential runs on the same sample under different thermal conditions without removing the sample probe. Two probe designs are available coil element for solid polymers and ribbon element for polymer film and solvent deposits on polymers. [Pg.108]

Infrared spectra of polymers are also obtained in a rapid screening mode by pulse pyrolysis-FTIR using solid samples (ca. 0.1-0.5 mg) that are placed "as is" into the Pyroprobe-Pyroscan-FTIR system for semi-quantitative, qualitative information. The vapor phase IR spectrum in Figure 3a is that from a pulse pyrolysis (750 C for 10 sec) of a 100 mg sample of solid poly(styrene). The thermal decomposition of poly(styrene) to its slyrene... [Pg.14]

Figure 2. (a) Pyrolysis/Concentrator/GC/RD. Pyrogramfrom pulse pyrolysis (750 C/10 sec) of propylene-1-butene copolymer, (b) Peak area ratio fiJB versus % 1-butene concentration. [Pg.15]

Investigation of the pyrolytic degradation of ion exchange resins by means of foil pulse pyrolysis coupled with gas chromatography/mass spectrometry. Sep. Sci. TechnoL, 28, 653 —673. [Pg.341]

Pulsed pyrolysis and 40 pg of polymer. Styrene (92.4-99.8% depending upon temperature), benzene, toluene, and ethyl benzene 163... [Pg.495]

Recently, other photochemical and thermal retro-Wolff rearrangements have been examined by several researchers.52 55 Under flash vacuum and pulsed pyrolysis conditions, Wentrup and co-workers observed the formation of (cyanovinyl)ketenes from aza fulvenones. Additionally, Moore and co-workers have done extensive work on the gas-phase photochemistry and molecular dynamics on the C2H2O surface using state-resolved spectroscopic methods. [Pg.1821]

Cationic and anionic ion exchange resins Foil pulse pyrolysis 400-500 °C Sulfur dioxide, benzene at 500 °C also ethyl benzene, styrene, hydrogen sulfide, toluene at higher temperatures. Anionic resins trimethylamine methyl chloride at 400 °C, and styrene, p-methyl styrene, p-ethyl styrene at 400-900 C. - [86]... [Pg.115]


See other pages where Pulse pyrolysis is mentioned: [Pg.179]    [Pg.180]    [Pg.241]    [Pg.279]    [Pg.36]    [Pg.255]    [Pg.269]    [Pg.17]    [Pg.17]   
See also in sourсe #XX -- [ Pg.524 ]




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