EFFECT OF HBR, HCL AND CL-2 ON FULLERENE FORMATION IN BENZENE OXYGEN ARGON FLAMES

Amounts between 2.5 and 5.9% of HBr, HCl and Cl-2 were added to fuller ene forming benzene/oxygen/argon flat-flames burning at 75 mbar in an attempt to affect halogen substitutions in the carbon framework. The i nhibition effect of HBr dramatically reduced the yield of fullerene, w hile it stayed in the same order of magnitude after addition of HCl or Cl-2. No formation of halogenated fullerenic compounds could be detec ted by mass spectrometry using chemical ionization with CH4/N2O or MAL DI. The measurement of bromine- and chlorine-precursor mass spectra sh owed the formation of a great number of bromine or chlorine containing compounds, essentially polycyclic aromatic hydrocarbons (PAH). In the case of HBr addition, only relatively small molecules could be observ ed because reactions with bromine atoms are thermodynamically less fav ourable in regions far from the burner with relatively high temperatur es.