Ab Initio Quantum Chemical and Kinetic Modeling Study of the Pyrolysis Kinetics of Pyrrole

Abstract

The kinetics of pyrolysis of pyrrole have been investigated theoretically by ab initio quantum chemical techniques and by detailed chemical kinetic modeling of previously reported experimental results. [Mackie, J. C.; Colket, M. B.; Nelson, P. F.; Esler, M. Int. J. Chem. Kinet. 1991, 23, 733.] The overall kinetics can be successfully modeled by a 117 step kinetic model that gives good agreement with temperature profiles of major products and also provides an acceptable fit for minor products. The thermochemistry and rate parameters of a number of key reactions have been obtained by ab initio calculations carried out at CASSCF, CASPT2, and G2(MP2) levels of theory. Several reaction pathways were investigated. The major product, HCN, arises principally from a hydrogen migration in pyrrole to form a cyclic carbene with the NH bond intact. Ring scission of this carbene leads to an allenic imine precursor of HCN and propyne. This is the decomposition pathway of lowest energy. Pyrolysis is preceded by the facile tautomerization of pyrrole to 2H-pyrrolenine. The latter can undergo CN fission to form an open chain biradical species, which is the precursor of the butenenitrile isomeric products, cis- and trans-crotononitrile and allyl cyanide. The biradical can also undergo facile H-fission to form cyanoallyl radical, which is an important precursor of acetylene, acetonitrile, and acrylonitrile. H2 also arises principally from H-fission of the biradical.

NO formation from ammonia, hydrogen cyanide, pyrrole, and caprolactam under incinerator conditions

“…8 emphasize that pyrrole is mainly converted into HCN for all investigated air equivalence ratios, which is in agreement with the experimental investigations of Mackie et al [23] and the newer modelling results from Martoprawiro et al [24]. Under fuel rich conditions, hydrogen cyanide is a stable species not being decomposed.…”

“…For the simulation of the decomposition of pyrrole, the modified mechanism used for simulating the oxidation of ammonia and HCN has been extended with the pyrrole mechanism from Martoprawiro et al [24]. The calculated concentration profiles of CH 4 and NH 3 agree well with the experimental data (not shown in the Fig), however, the calculated decomposition rate of pyrrole is much lower than that from the experimental data (Fig.…”

An experimental and kinetic modeling study of a premixed nitromethane flame at low pressure

“…In addition to C 2 H 6 , C 2 H 2 and C 2 H 4 are identified with higher concentrations than other hydrocarbon intermediates. C 2 H 4 can be formed through the self-combination of CH 3 by H 2 -abstraction [12] and can convert to C 2 H 2 according to Martoprawiro et al's study [43]. C 2 H 2 can be consumed by O/OH to form CO and C 2 H 2 O [41].…”

Experimental and theoretical studies on decomposition of pyrrolidine

“…Ncontaining monocyclic model compounds investigated to date include pyrrole, pyridine, 2-picoline and pyrrolidine [2]. Extensive studies of the pyrolysis, oxidation and combustion of pyrrole [3][4][5][6][7][8][9][10] and pyridine [11][12][13][14][15][16][17][18] have been performed; both are aromatic compounds with unsaturated bonds. In contrast, information on the pyrolysis and 1540-7489/$ -see front matter Ó 2010 The Combustion Institute.…”