Formation of fullerenes in the laser-pyrolysis of benzene

Laser pyrolysis of benzene-based mixtures is a continuous way of synthesizing fullerene-containing soots. The method is based on a CO, laser's interaction with a mixture of hydrocarbon, oxidizer, and sensitizer (usually SF,) in a cross-flow irradiation cell at a relatively low pressure (ca. 0.8 bar) using different carrier gases for benzene vapor. The effects of the flow rate of the carbon-precursor, the nature and ratio of sensitizer to oxidizer, the laser's power density, and the nature of the carrier gases are studied to improve the yield of fullerene. Fullerenes are separated from soot by extraction with toluene and then identified, quantified, and isolated by liquid chromatography. Infrared analyses of the exhausted gases and solid products allow the identification of some components and also give information on the role of the different parameters. Chemical analysis shows that sulfur (from the SF,) is an important component in soot produced this way, becoming the major component of the toluene extract. (C) 2000 by The Combustion Institute.