6165-96-4Relevant articles and documents
Scavenging of hydrocarbon radicals from flames with dimethyl-bisulfide II. Hydrocarbon radicals in fuel-rich low-pressure flames of acetylene, ethylene, 1,3-butadiene and methane with oxygen
Hausmann,Homann
, p. 651 - 667 (2007/10/03)
The new technique of free-jet condensation/scavenging with dimethyl-disulfide has been applied for the quantitative analysis of hydrocarbon radicals and carbenes in flat premixed hydrocarbon/oxygen flames burning with fuel-rich mixtures at 27 mbar. The results are reported as profiles of mole fractions of the radicals. The limit of detectability was about l-10~7mole fraction. Qualitatively the radicals are very similar with the four fuels, but there are large differences in their quantities. While in the methane flame only C1 and C2 radicals were present in detectable concentration, higher radicals up to naphthyl could be detected with the unsaturated fuels. Although methyl could not be determined quantitatively, it was found to be the major hydrocarbon radical in all flames. Methoxy radical was only found in the methane flame. Whereas, for example, C2, C3H2 and C3H are typical high-temperature species, C2H is surprisingly formed at the beginning of the oxidation zone at relatively low temperature. Vinyl and the vinyl-type radicals C2nH3 (n = I to 4) are in equilibrium with acetylene and the polyynes (C2nH2) at maximum flame temperature and in the burned gas. Since phenyl peaks always after benzene, it is concluded that it is mainly a degradation product from benzene and other lower aromatics. The mechanism of formation of C2H and C2, the equilibria of the C2nH3 and the relation between aliphatic and aromatic radicals are discussed. VCH Verlagsgesellschaft mbH, 1997.
SCAVENGING OF RADICALS FROM THE GAS PHASE BY FREEZING WITH DIMETHYL DISULFIDE: 2. RADICALS FROM DISCHARGES AND A FLAME OF ACETYLENE.
Kubitza,Schottler,Homann
, p. 695 - 700 (2007/10/02)
The method of detecting radicals from low-pressure gas-phase systems by scavenging with dimethyl disulfide (DMD) has been applied to microwave discharges in C//2H//2/He mixtures and to a C//2H//2/O//2 flame. It was accomplished by condensing a supersonic nozzle beam from the reaction system together with a beam of DMD on a liquid-N//2 cooled surface. The scavenging products were measured by GC/MS after warming-up. Radicals measured in the discharge were C//2H, C//4H, C//6H, C//3H//2, C//2 besides H atoms. Preliminary measurements on the flame showed that C//6H//5 (phenyl), CH//2, C//3H//2, besides H and O atoms were prominent radicals at the end of the oxidation zone. The concentration of phenyl is of the same order as that of e. g. naphthalene.
LOW-PRESSURE PYROLYSIS OF BUTADIYNE (C4H2).
Homann,Pidoll
, p. 847 - 854 (2007/10/02)
Butadiyne (C//4H//2) mixed with helium (maximum 1:9) was pyrolyzed in a low-pressure flow reactor at temperatures between 700 and 1000 degree C and total pressures of 3 to 13 mbar. The residence time (maximum 45 ms) was varied by a movable inlet lance for the C//4H//2. Samples were drawn through a molecular beam system and analyzed mass-spectrometrically. The main products were C//2H//2, H//2, polyyines (C//6H//2, C//8H//2), oligomers of the composition (C//4H//2)//n, n equals 2 to 5, polymer and coke. The activation energy for oligomer formation ranged from 145 to 168 kJ mol** minus **1 increasing with higher degree of oligomerization. A mechanism for the formation of polyynes and oligomers is discussed starting with an excited C//4H//2 which can add C//4H//2 to give either a linear or a branched dimer C//8H//4. The results are compared to the formation of polycyclic aromatic compounds in the burned gas of fuel-rich flames that also contains C//2H//2 and C//4H//2.
