TEM Studies of Coal Tars Influence of Distillation Process at Increasing Temperature

A Solmer coal tar and the same filtered were progressively distilled. The pitches obtained have increasing KS softening points. They were characterized by Transmission Electron Microscopy (thin sectioning) and Optical Microscopy (on the same areas). The filtered coal tar contains only γ resins (toluene soluble TS). During the distillation process, mesophase spheres with Brooks and Taylor texture are formed. They are attacked by anthracene oil (AO sensitive), but are quinoline insoluble (QI). They are first single, then coalesced, then formed into mosaics. The initial unfiltered tar contains a resins—both anthracene oil insolubles (AOI) and quinoline insolubles (QI). They are carbon blacks and plastic spheres with radial and alternate textures. Unfiltered tar also contains β resins (toluene insoluble and quinoline soluble QS) and γ1 resins (TS) associated as halos surrounding the AOI core. The majority of the tar is γ2 resins (TS) gathered in droplets. During the distillation process, the initial AOI and QI remain constant. The γ2evolve to mesophase nuclei (partly QS and partly QI) then to Brooks and Taylor mesophase individual spheres (AO sensitive but QI) and finally to mosaics (AOI and QI). The β and α1 halos evolve into edge to edge associations of aromatic units (flow orientations finally becoming both AOI and QI)