Study on chemical composition and formation mechanism of some typical pitch feedstocks using field desorption mass spectrometry

The molecular distributions and constitutions of several A-240 petroleum and coal tar pitch fractions were investigated using field desorption mass spectrometry. The molecular profiles of all samples analysed were greatly extended and the maximum mass weight of CTP-BSHI approached 640 corresponding to 13 aromatic fused-rings, while that of A-240-BS approximated to 784 matched to 14 kata-condensed rings. The coal tar pitch samples were mainly composed of peri-condensed polyaromatics, with kata-condensed PAHs amounting to 1 4 of total sample. In contrast, A-240 petroleum pitch samples consisted almost totally of polyacenes (or their isomers) and polyaryl alkanes. The extremely different characteristics in the compoundtype distributions between these two pitches reflect the different features of high temperature gas-phase pyrolysis and medium temperature liquid-phase pyrolysis reactions.