Pyrolysis of benzene behind reflected shock waves

✍ Scribed by H.J. Singh; R.D. Kern

• Publisher: Elsevier Science
• Year: 1983
• Tongue: English
• Weight: 637 KB
• Volume: 54
• Category: Article
• ISSN: 0010-2180
• DOI: 10.1016/0010-2180(83)90021-4

✦ Synopsis

The pyrolysis of benzene was studied in the temperature and pressure range of 1400-2200K and 0.25-0.81 arm using a shock tube coupled to a time-of-flight mass spectrometer. The mixtures employed were 2.1 and 5% benzene diluted with neon, which yielded a carbon atom density range of (1.6-7.9) x 1017 atom cm -3 in the reflected shock zone. Products were analyzed by recording the mass spectra at 30 #s intervals during a total observation time of 700-1200 #s. C2H2, C4H 2, and C6H 2 were the major products produced during the decomposition. The only species having m/e > 78 were CsH 2 and CsH 6 (phenylacetylene), which were formed in relatively low concentrations and only at the high temperature end of the study. The product analysis was further substantiated by performing experiments with benzene-d6 mixtures under similar conditions. One important finding of this study was the observation that the phenyl radical was not detected above the threshold level of 10-10-10-11 tool cm -3 under the reaction conditions investigated. From the initial rates of benzene decomposition, a second-order rate constant was best described by the equation k = 1014.81 exp(-34.33 kcal/RT) cm a mol ---1 s---1.

After numerous calibration experiments, concentration profiles were consmtcted which accounted for 75-93% of the total carbon atom input and thereby established an upper limit of soot yield to be not more than 30% of the initial carbon atom concentration.