Reassessment of the Kinetic Influence of Toluene on n-Alkane Pyrolysis

• Published in: Energy & fuels 2010-07, Vol.24 (7), p.3817-3830
• Main Authors: Lannuzel, Frédéric, Bounaceur, Roda, Michels, Raymond, Scacchi, Gérard, Marquaire, Paul-Marie
• Format: Article
• Language: English
• Subjects: Catalysis and Kinetics; Chemical and Process Engineering; Engineering Sciences
• ISSN: 0887-0624; 1520-5029
• DOI: 10.1021/ef100253z

The inhibition effect of toluene on the kinetics of n-alkane pyrolysis has been well-known for a long time. However, most studies were performed at high-temperature−low-pressure conditions. The present study investigates a wider range of experimental pressures and temperatures (from 0.001 to 700 bar and from 350 to 600 °C). To account for those, a kinetic model based on free-radical reactions was developed. This model was tested against available literature data for the low-pressure range and against new experiments for the high-pressure range. Whatever the temperature and pressure, it arises that toluene has indeed an inhibitive effect on the pyrolysis of n-octane. This effect is explained by the formation of benzyl radicals stabilized by resonance, via hydrogen-transfer reactions, that leads to new termination reactions. However, this inhibition will be significantly modulated as a function of the pressure, temperature, and reaction progress, from strong to very weak. Our paper describes the mechanistic reasons for this change in the extent of the inhibition effect and proposes an integrated model for the kinetic effects of monoaromatic hydrocarbons on n-alkanes during pyrolysis.