Experimental Study on Fullerene Formation Process in Toluene Flame at Low Pressure Condition

Abstract

Polycyclic Aromatic Hydrocarbons generated in the combustion processes of fuel rich hydrocarbon flames are considered to be important precursors of soot that causes environmental pollution. On the other hand, in a combustion process under low pressure conditions, the generation of fullerenes which are one of large cage-shaped carbon clusters was reported. Combustion synthesis of fullerenes is expected to be one of the mass production methods of fullerenes and a premixed flame of toluene and oxygen is utilized in real mass production process of fullerenes. However, the fullerene formation mechanism from PAH in toluene and oxygen premixed flames has not been clarified yet. Therefore, in the present study, contents of PAH and fullerene in the total soot obtained from premixed flames of toluene and oxygen surrounded with premixed flame of methane and oxygen under various physical conditions were analyzed through gas and liquid chromatography. In the present study over 5 weight percent PAHs were found in the collected soot samples and 22 kinds of substances in PAHs can be specified by using the standard sample and 10 isometric structures of PAHs can be specified by using a gas chromatograph system. When the flame fluctuation was small because of low flow rate of the center and outer flames, the fullerene content in the soot sample increased and the PAH contents of lower molecular weight increased with the increase of the pressure in the chamber. When the flame fluctuation was relatively large because of high flow rate of the center and outer flames, the fullerene content in the soot sample had the maximum peak and the PAH contents of lower molecular weight were dramatically changed from those in the case with small flame fluctuation. Contents of C60 in the total fullerenes increased and those of C70 decreased with the increase of the pressure in the chamber.