The shock tube pyrolysis of pyridine

Fossil fuels such as coal and heavy fuel oils contain up to about 2 per cent by weight of fuel nitrogen, most of this being present in pyridine or pyrolic aromatic structures. Under pyrolytic conditions these ring structures decompose to give HCN and CH3CN. For present day computer modelling of NOx formation in flames it is necessary to know the mechanism and rates of reaction. A number of previous studies of pyridine pyrolysis have been undertaken using shock tubes or flow reactors. In this present study a shock tube was used to obtain the kinetics of pyridine decomposition in the range 1590–2335 K and with pressures between 2.2 and 3.4 atm. Two independent sets of data were obtained. One set of results was found to be represented by an Arrhenius rate constant k=109.7±0.5 exp (−220.0 kJ mol−1 RT−1)s−1. For the other work k= 109.8±0.5 exp (−228.191±18.42 kJ mol−1 RT−1)s−1. In addition, the pyrolysis mixtures of pyridine plus toluene have also been studied to understand the synergistic effects. The results indicated the strong involvement initiated by fission of the pyridine ring system.