SELECTIVE PREPARATION OF ANISOTROPIC SPHERES FROM COMMERCIAL PITCHES BY CARBONIZATION UNDER VACUUM.

Mesophase spheres were selectively prepared from petroleum A240, hydrotreated A240, and coal tar pitches by heat treatment at 430 degree C for 1 h under vacuum (5-10 Torr), the sphere content being as high as 55 vol% in the residual product. Mesophase spheres from A240 and coal tar pitch tended to coalesce as bulk mesophase of irregular shape when heat-treated for the longer time of 3 H. In contrast, spherical shapes of larger diameter were maintained when hydrotreated A240 was heated under the same conditions where the sphere content was 70 vol%. The spheres were separated by pyridine extraction.