Chemistry of the co-pyrolysis of an aromatic petroleum residue with a pyridine-borane complex

Synthesis of boron-doped mesophase by controlled co-pyrolysis of an aromatic petroleum residue and a pyridine-borane complex, PB, as a boron source, was carried out. Pyrolysis was performed at temperatures ranging from 400 to 440 T, under 1 MPa nitrogen atmosphere. Soaking time was varied between 1.5 and 6 h, and the boron concentration in the pyrolysis mixtures ranged from 0 to 1 wt.%. The effect of the presence of boron upon solid yield, insoluble content, mesophase development and microstructure was studied. PB reacts with molecules of the petroleum residue and creates B-C bonds, B 2 substituting C in the polyaromatic molecules, with sp(2) hybridisation, and probably also creating B crosslinking between polyaromatic units. The enhanced reactivity caused by B addition is reflected in an increment of viscosity; as a result, the development of mesophase is strongly increased, but the size of the mesophase structures is decreased to a mosaic texture; B also causes an increase of the interlayer spacing and a noticeable enhancement of insoluble material. (C) 2002 Elsevier Science Ltd. All rights reserved.