Tem studies of coal tars: Crude tar and its insoluble fractions

Abstract

Tars as issued from a coking plant were characterized by Transmission Electron Microscopy (TEM). A method of microtomy allowing tars to be thin-sectioned was perfected. The microtextural data obtained are compared to those obtained from anthracene-oil insolubles (AOI) also prepared by thin section and to those obtained from ground AOI. Crude tars are constituted of droplets of various sizes and shapes, either clean or including other phases such as carbon blacks (in majority) and spheres with radial or alternate textures (concentric and then radial). Clean droplets are γ resins (toluene soluble). Droplets containing other phases are γ resins only in their skin and β resins (toluene insoluble but quinoline soluble) in the areas in contact with carbon blacks or spheres. No Brooks and Taylor mesophase spheres were observed. The thin-sectioned AOI contain the same phases, in the same amount. However they are devoided of surrounding droplets, i.e. AOI or α resins are made of carbon blacks and radial or alternate spheres, in the AOI observed after grinding only the carbon blacks particles remain, this means that radial or alternate spheres are viscoelastic or plastic.