Impact of coal extract solvent fraction composition on mesophase formation and carbonization yield

The demand for graphitic carbon products such as high performance carbon fiber and synthetic graphite continues to grow, requiring further development and understanding of viable feedstock and precursor materials. In particular, coal extracts from mild direct coal liquefaction are of interest as a relatively low-cost feedstock for graphitic products. In this work, a coal extract was solvent fractionated into oil, asphaltene, and preasphaltene fractions and the impact of each fraction on mesophase formation and carbonization yield was investigated. Furthermore, interactions between the solvent fractions were studied by preparing blends at fixed ratios and determining the effect on mesophase optical texture. It was found that the preasphaltene fraction can contribute to strikingly higher carbonization yields relative to the oil and asphaltene fractions. However, only low preasphaltene content could be tolerated in the blends to form mesophase with desirable optical texture, demonstrating the strong lyotropic character of the mesophase. These findings provide a framework for balancing mesophase pitch properties while maximizing carbonization yields towards producing graphitic carbon products, such as carbon fiber and synthetic graphite.