The Chemistry of Mesophase Formation

Abstract

The origins and development of the concept of carbonaceous mesophase, as derived from discotic aromatic nematic liquid crystals, enable applications to be made to industrial processes. The world availability of pitch materials is such that there is an abundance of pitch which produces cokes of little commercial value. A major incentive for research into the Chemistry of mesophase formation is the commercial up-grading of such pitches and the development of specialized pitches. Structure in cokes is described in terms of optical texture. The importance of viscosity of pyrolyzing pitch in controlling size of optical texture is stressed. Pitch viscosity itself is related to chemical composition of the parent material. Those rich in oxygen and sulphur tend to produce cokes with small sized optical texture; those rich in hydrogen tend to produce cokes with large sized optical texture related to needle coke formation. Generally, cokes with small sized optical texture tend to have higher strength, higher reactivity and higher CTE values. Cokes with larger sized optical texture, e.g. needle cokes, have lower reactivity and CTE values. The important role of transferable hydrogen in carbonizing systems is stressed. Attention is drawn to the fact that inerts or quinoline-insoluble material in pitch may not be inert, but can be chemically and physically active in the carbonization system. Future research and development is outlined.