Investigations on the cross-linking of binder pitch matrix of carbon bodies with molecular oxygen .1. Chemistry of reactions between pitch and oxygen

The reactivity between a petroleum pitch (Ashland A 240) and oxygen was studied at 1 MPa oxygen pressure and temperatures between 200 and 280 degrees C using thin pitch films. After oxidation the pitch was analyzed by FT-IR and XPS with respect to the formation of oxygen-containing functional groups. A green mix shaped into cylindrical bodies was treated with oxygen for various times for the determination of oxygen-containing functional groups by pyrolysis gas analysis. These and some additional results by DSC and ESR were used to develop reaction schemes. We have distinguished between (1) the formation of oxygen-containing functional groups (hydroxyl, carbonyl, carboxyl); (2) cross-linking reactions between oxygen-containing functional groups, both occurring with liberation of water only, and (3) cross-linking reactions by formation of C-C bonds induced by decomposition of oxygen-containing functional groups and typically accompanied by formation of CO2 and CO. The latter result indicates that oxygen-containing functional groups only affect an intermediate stability of volatile pitch molecules up to temperatures at which C-C bonds can be formed in the pyrolysis. (C) 1997 Elsevier Science Ltd.