THERMAL-DECOMPOSITION OF N-METHYLPYRROLE - EXPERIMENTAL AND MODELING STUDY

The thermal decomposition of N-methylpyrrole was studied behind reflected shocks in a pressurized driver single pulse shock tube over the temperature range 1050-1300 K at overall densities of approximately 3 X 10(-5) mol/cm3. A large number of decomposition products with and without bound nitrogen were obtained under shock heating. High concentrations of isomerization (2- and 3-methylpyrrole) and six-membered ring compounds (pyridine) were also found. The main decomposition channel is initiated by a rupture of the N-CH3 bond with a rate constant of initiation k(init) = 10(16.26) exp(-79.5 X 10(3)/RT) s-1, where R is expressed in units of cal/(K mol). Abstraction reactions and recombination of methyl radicals lead to the production of a line of hydrocarbons such as CH4, C2H6, and C2H4. Abstraction of a hydrogen atom from the N-CH3 group leads to the production of C4H4N-CH2. which upon ring enlargement produces pyridine. Toluene was used as a free radical scavenger to distinguish between radical chains and unimolecular processes. Reaction products such as CH3CN are obtained by a unimolecular decomposition of the N-methylpyrrole ring. The total decomposition of N-methylpyrrole in terms of a first-order rate constant is given by k(total) = 10(16.7) exp(-79.2 X 10(3)/RT) s-1. First-order Arrhenius rate parameters for the formation of the various reaction products are given, a reaction scheme is suggested, and results of computer simulation and sensitivity analysis are shown. Differences and similarities in the reactions of pyrrole and N-methylpyrrole are discussed.