Gas phase pyrolysis of heterocyclic compounds, part 4: flow pyrolysis and annulation reactions of some oxygen heterocycles: furan, benzo[b]furan and dibenzofuran. A product oriented study

Continuous flow pyrolysis (CFP) of furan (1), benzo[b]furan (2) and dibenzofuran (3) has been investigated at 900 degreesC. Complete decomposition of 1 and 2 was observed, while 3 proved to be more temperature resistant. In the pyrolysates of 1-3, up to 22 different products were identified by GC-MS, 12 of these are identical. Mainly polycyclic aromatic hydrocarbons (PAHs), such as naphthalene (11) (6-28%), phenanthrene (17) (2-25%), biphenyl (22) (1-11%), pyrene (18) (1-10%), benzopyrene (19) (1-10%), fluoranthene (20) (3-9%), triphenylene (21) (3-9%), acenaphthylene (13) (1-6%), anthracene (23) (1-6%) and fluorene (12) (1-3%), were obtained. Only from 3, small amounts of larger oxygen containing polycyclic hetarenes (PHAs), such as benzo[b]naphtho[2,3-d]furan (37) and benzo[1,2-b:4,5-b']bis[1]benzofuran (36), are generated as additional products besides PAHs. (C) 2001 Elsevier Science B.V. All rights reserved.