Kinetics of pyrolysis of a coal model compound, 2-picoline, the nitrogen heteroaromatic analogue of toluene. 2. The 2-picolyl radical and kinetic modeling

• Published in: Journal of physical chemistry (1952) 1992-12, Vol.96 (25), p.10339-10348
• Main Authors: Doughty, Alan, Mackie, John C
• Format: Article
• Language: English
• Subjects: 01 COAL, LIGNITE, AND PEAT; 010900 > Coal, Lignite, & Peat-- Environmental Aspects; 400800 > Combustion, Pyrolysis, & High-Temperature Chemistry; ACETYLENE; ALKENES; ALKYNES; AZINES; CARBONACEOUS MATERIALS; CHEMICAL REACTIONS; COAL; COMBUSTION; CYANIDES; CYCLOALKENES; CYCLOPENTADIENE; DATA; DECOMPOSITION; DIENES; ENERGY SOURCES; FOSSIL FUELS; FUELS; HETEROCYCLIC COMPOUNDS; HYDROCARBONS; HYDROCYANIC ACID; HYDROGEN COMPOUNDS; INFORMATION; INORGANIC ACIDS; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; KINETICS; MATERIALS; NUMERICAL DATA; ORGANIC COMPOUNDS; ORGANIC NITROGEN COMPOUNDS; OXIDATION; PICOLINES; POLYENES; PYRIDINES; PYROLYSIS; PYROLYSIS PRODUCTS; RADICALS; REACTION KINETICS; THEORETICAL DATA; THERMOCHEMICAL PROCESSES 014000 > Coal, Lignite, & Peat-- Combustion; THERMODYNAMICS
• ISSN: 0022-3654; 1541-5740
• DOI: 10.1021/j100204a045

The pyrolysis of 2-picoline, investigated experimentally in our previous paper, has been successfully modeled using a 70-reaction free-radical mechanism. The mechanism includes decomposition pathways of o-pyridyl and 2-picolyl, both of which are formed through the principal initiation reactions of 2-picoline. The proposed mechanism for 2-picolyl decomposition involves the direct ring opening of the 2-picolyl radical. Further reactions of the open chain isomer of 2-picolyl resulted in the formation of the major products HCN and acetylene and the minor products 1-cyanocyclopentadiene and cyclopentadiene. Kinetic modeling confirmed the feasibility of this mechanism by predicting the observed profiles for these species. Optimizing of the heat of formation of 2-picolyl through kinetic modeling resulted in a value of 68 ([+-] 5) kcal mol[sup [minus]1]. This value suggests a lower level of resonance stabilization for 2-picolyl compared to benzyl. This inference is supported by the normal value of the rate constant for 2-picolyl + H recombination found by modeling to be in the range 1 [times] 10[sup 13] 6 [times] 10[sup 13] cm[sup 3] mol[sup [minus]1] s[sup [minus]1]. The reactant and product profiles predicted by the kinetic model were found to be very sensitive to the rate of the initiation reaction yielding methyl and o-pyridyl radicals. 43 refs., 8 figs., 3 tabs.