Growth and coalescence of mesophase in pitches with carbon black additives and in coal

Abstract

The techniques of polatized light optical microscopy and of washing the surfaces of solid pyrolysis products with chloroform prior to SEM examination are used to monitor the growth and coalescence of growth units of mesophase in a petroleum pitch, a coal extract and a caking coal. Additions of 1 wt% of carbon black retard growth and coalescence and promote clustering of these units because of adhesion of carbon black particles. This has the effect ultimately of reducing the size of the optical texture in coke from the coal extract, but not with coke from the petroleum pitch which has lower viscosity. With the coal, mesophase growth units tend to form clusters and do not coalesce. Mesophase can form an anisotropic skin on the inside of developing pores (bubbles) in the fluid phase and this may limit their growth.