Thermal decomposition of two coal model compounds — pyridine and 2-picoline. Kinetics and product distributions

摘要

The thermal decomposition of two coal model compounds, pyridine and 2-picoline, has been studied in a completely stirred fused-silica reactor over the temperature range 1060-1240 K at pressures between 8.0 and 13.3 kPa and at reactor residence times between 1 and 5 s. Profiles of major products and kinetics of thermal decomposition of both compounds are given and a detailed investigation by GC/MS of the minor products of decomposition has been made. Profiles of pyridine and its major products of decomposition can be satisfactorily modelled by a homogenous gas phase kinetic model. The rate of decomposition of 2-picoline was faster than predicted by a homogenous gas phase mechanism and the decomposition would appear to be surface-assisted in the silica reactor. Both compounds were found to be useful models for the evolution of fuel-bound nitrogen from decomposition of coals. 2-Picoline, a nitrogen heteroaromatic analogue of toluene, was found, like its hydrocarbon analogue, to have a high propensity for sooting. The presence of the nitrogen atom in the condensed ring products of 2-picoline was found to be a useful chemical marker for unravelling the complex condensation chemistry leading to the formation of soot.