Effects of coal structures on denitrogenation during flash pyrolysis

Yallourn, Taiheiyo, South Banko, Miike, and Hunter Valley coals were pyrolyzed using a Curie-point pyrolyzer at 500-1040 degrees C. Product distributions were determined by GC-TCD and GC-FTD, and N-2 evolved in the gas phase was analyzed using a quadrupole mass spectrometer. Samples were also prepared by mildly oxidizing Yallourn coal and hydrogenating the resulting ethanol soluble over a Ru/Al2O3 catalyst. Quinoline and hydrogenated quinolines were also used as models in order to better understand the role of the heterocyclic structure in denitrogenation during pyrolysis. More than 90 mol % of the nitrogen atoms in the coals remained in the char and tar as a result of the pyrolysis of the raw coals. However, the heterocyclic structures of the raw Yallourn coal were partially changed by hydrogenation over a Ru/Al2O3 catalyst, and this alteration enhanced the cleavage of those structures during pyrolysis, decreased the nitrogen content of the char, and increased the yield of nitrogen compounds in the gas phase.