Absorption spectroscopy of toluene pyrolysis.

Toluene pyrolysis in high temperature/high pressure argon atmosphere has been studied in a conventional diaphragm-type shock tube. The investigated ranges of temperature and pressure were 1500-2300 K and 8-13 bar, respectively. Extinction measurements in the near infrared have been carried out to follow the formation of carbonaceous particulate (soot). Pyrolysis products were optically characterized by absorption measurements in the wavelength range 300-800 nm, with high time/spectral resolution. The application of Tauc analysis to the absorption spectra allowed to identify three levels of energy gap; they have been attributed to carbonaceous structures with 3-5 and 7-9 fused aromatic rings, and to soot particles.