Mechanism of co-pyrolysis of coal-tar pitch with polyacrylonitrile

Co-pyrolysis of coal-tar pitch with polyacrylonitrile (PAN) and PAN oxidized in air at 300 degreesC was studied as a possible way of manufacturing of carbonaceous materials enriched in nitrogen. The thermal behaviour of components and blends was evaluated by thermogravimetry and optical microscopy of solid residues. The transformation of nitrogen functional groups on co-treatment was monitored using elemental analysis, infrared spectroscopy and X-ray photoelectron spectroscopy. Oxidized polymer behaved as an inert during co-pyrolysis. In contrast, strong interactions of unoxidized PAN with pitch could be deduced from enhanced residue yield and extensive deterioration of the optical texture of resultant coke. Principal chemical interaction between components seems to be hydrogen abstraction from pitch constituents by radicals generated from PAN bonds scission. Pitch matrix does not modify distinctly the way of nitrogen functionalities evolution. At semi-coke stage majority of nitrogen occurs as pyridinic nitrogen with pyrrolic and/or pyridonic one being a second relevant form. (C) 2002 Elsevier Science B.V. All rights reserved.