Characterisation of tars from the co-pyrolysis of waste lubricating oils with coal

Pyrolysis of a lubricating oil waste with or without coal yields important quantities of valuable products such as C-1-C-3 alkanes, C-2-C-4 olefins an d BTX. However, information on molecular structures of tars obtained is onl y available in terms of analyses in the CC-MS ranges. This range correspond s to an upper limit of approximately 300 u; aromatics of mass greater than 300 u do not normally elute from high-temperature GC columns. For this reas on, an oil tar, a coal tar and a tar obtained by the co-pyrolysis of the co al and oil (50:50 wt%) have been characterised by an array of techniques: p robe-mass spectrometry (probe-MS) (to extend the range of mass to 600 u); s ize exclusion chromatography (SEC) in 1-methyl-2-pyrrolidinone (NMP) solven t; matrix-assisted laser desorption ionisation-mass spectrometry (MALDI-MS) ; and UV-fluorescence spectroscopy (UV-F) to provide specific information o n chemical structures of products. Thin-layer chromatography (TLC) was also carried out for three samples of t ar (from oil, coal and mixed oil/coal) and fractions recovered from the pla tes were analysed by other techniques: SEC, UV-F and probe-MS. In addition, the proportion of the tars amenable to gas chromatography was determined; CC-MS was used to determine the main components of each tar within the GC r ange. In summary, it can be concluded that Samca coal tar is mainly formed by lar ge polynuclear aromatic ring systems, as well as by heterocyclic structures and alkyl or heteroatom substituents. The tar from the coal/oil mixture is much more similar to the tar from oil than to the tar from coal, reflectin g the synergy in the co-pyrolysis reaction. (C) 2000 Elsevier Science Ltd. All rights: reserved.