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A Shock Tube and Modeling Study about Anisole Pyrolysis Using Time‐Resolved CO Absorption Measurements
Author(s) -
Shu Bo,
Herzler Jürgen,
Peukert Sebastian,
Fikri Mustapha,
Schulz Christof
Publication year - 2017
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.21105
Subject(s) - chemistry , anisole , homolysis , dissociation (chemistry) , reaction rate constant , radical , bond dissociation energy , pyrolysis , shock tube , analytical chemistry (journal) , bond cleavage , decomposition , photochemistry , shock wave , thermodynamics , kinetics , organic chemistry , physics , quantum mechanics , catalysis
The pyrolysis of anisole (C 6 H 5 OCH 3 ) was studied behind reflected shock waves via highly sensitive absorption measurements of CO concentration using a rotational transition in the fundamental vibrational band near 4.7 µm. Time‐resolved CO mole fractions were monitored in shock‐heated C 6 H 5 OCH 3 /Ar mixtures between 1000 and 1270 K at 1.3–1.6 bar. The decomposition of C 6 H 5 OCH 3 proceeds exclusively via homolytic dissociation, with reaction rate k 1 , forming methyl (CH 3 ) and phenoxy (C 6 H 5 O) radicals. The subsequent decomposition of C 6 H 5 O by ring rearrangement and bond dissociation yields CO. To determine the rate constant k 2 of C 6 H 5 O decomposition avoiding secondary reactions, allyl phenyl ether (C 6 H 5 OC 3 H 5 ) was used as an alternative source for C 6 H 5 O. Its decomposition was studied between 970 and 1170 K at ∼1.4 bar. The potential‐energy surface of C 6 H 5 O dissociation has been reevaluated at the G4 level of theory. Rate constants determined from unimolecular rate theory are in good agreement with the present experiments. However, the obtained rates k 2 = 9.1 × 10 13 exp(−220.3 kJ mol −1 / RT )s −1 are significantly higher than those reported before (factor 6, 2, and 1.5 faster than those data reported by Lin and Lin, J. Phys. Chem . 1986, 90, 425–431; Frank et al., 1994; Carstensen and Dean, 2012, respectively). Good agreement was found between the measured CO concentration profiles and simulations based on the mechanism of Nowakowska et al. after substituting k 2 by the value obtained from experiments on C 6 H 5 OC 3 H 5 in this work. The bimolecular reaction of C 6 H 5 O and CH 3 toward cresol was identified as the most important reaction influencing the CO concentration at longer reaction time.